Dr. HENRY LYATSKY GEOSCIENCE CONSULTING PRACTICE
Based in Calgary, Alberta, Canada
Read our user-friendly tutorials (HERE and HERE) on the basics of gravity and magnetic geophysical methods.
Sign up for our SHORT COURSE on gravity and magnetic exploration methods.
Fault detection with gravity and magnetic data in the Alberta Basin: read our published ATLAS.
Read our PETROLEUM ASSESSMENT of sedimentary basins offshore western Canada.
Read our thoughts on the uses and abuses of SCIENTIFIC LOGIC.
What is a geophysical anomaly? Read our IDEAS.
Basement structure in northern Williston Basin in Saskatchewan and Manitoba from HORIZONTAL-GRADIENT VECTOR gravity and magnetic maps.
Find Lyatsky Geoscience in the media HERE and HERE!
WHAT WE DO
** Interpretation of gravity and magnetic data in conjunction with seismic, geological and remote-sensing information, on regional and local scales.
** Field acquisition and processing of potential-field data, including quality control of field programs.
** Integrated geological and geophysical studies of sedimentary basins.
** Regional and local prospect delineation for oil and gas, mineral and coal exploration.
** Technical teaching, training and instruction.
** Free-lance science research and writing, including two geophysical atlases and three practical books on the geology and exploration methods in western Canada and U.S.
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This web page is best viewed with MEDIUM screen text size.
We use the GEOSOFT potential-field data-processing software!
We use potential-field, seismic and geological information to delineate fault networks in the crust and tie them to the genesis and distribution of mineral and hydrocarbon deposits.
Dr. Henry Lyatsky, P.Geoph., P.Geol., second generation in the profession and the business, has considerable field and in-house experience, successfully using potential-field and seismic data, as well as diverse geological information, in oil and gas, mineral and coal exploration. He has designed, carried out and QC'd potential-field airborne and land data-acquisition programs in the field, and processed and interpreted such data in successful exploration programs.
With domestic and international experience, Dr. Henry Lyatsky has worked in many parts of the Alberta, Williston and Mackenzie basins, Canadian Shield, east and west coasts of Canada, Canadian and U.S. Cordillera, Beaufort Sea, North Sea, Pannonian Basin, Ukraine, Azerbaijan and Mongolia.
A detailed, practical tutorial on the uses of gravity and magnetic data to identify brittle basement faults are included in our gravity and magnetic atlas of the Alberta Basin (Lyatsky et al., 2005, Alberta Geological Survey Special Report 72). Click here for a free download!
As well, very helpful for delineating subtle potential-field anomalies has been our horizontal-gradient vector (HGV) method. It recognizes the horizontal gradient as a vector, having a magnitude and a direction, and depicts the gradient on a map as a vector arrow for each data grid node. The resulting maps are very effective at resolving the details of anomaly clusters, finding lineaments and indicating block tilts.
The HGV method is described in a number of our technical publications. Consistent work on it was initiated by my father, Dr. Vadim Lyatsky, and the HGV method was developed in the public domain during the 1990s. It resulted from a close collaboration with the faculty and students at the University of Calgary and scientists at the Geological Survey of Canada (and with the benefit of early sponsorship by the Home Oil Company Ltd.). The most recent updates of the HGV method, applied to regional gravity and magnetic data in the Williston Basin, are described by Lyatsky, Dietrich and Edwards, 1998, Geological Survey of Canada Open File 3614.
Like many processing techniques, the HGV method works best not on its own but when incorporated into a comprehensive program utilizing various methods of data processing, display and interpretation, applied to a broad range of geological and geophysical information.
Our thinking on the modes of crystalline-basement control on the sedimentary cover, and the practical methods of identifying and predictively using this control in exploration, is still evolving (see, for example, our book Lyatsky, Friedman and Lyatsky, 1999, Principles of Practical Tectonic Analysis of Cratonic Regions, Springer-Verlag). It is work in progress, and your thoughts and suggestions are welcome. Some of our current ideas are summarized below.
TABLE OF CONTENTS
Material in this web site is arranged, by the exploration region and subject, into the following sections.
1) Alberta and Williston basins in western Canada and U.S.
2) Queen Charlotte frontier shelf basin on the west coast of Canada.
3) Central Asia of China and CIS.
4) Dr. Henry Lyatsky's c.v. and publications.
5) Canadian Cordillera.
6) Western continental margin of North America in Canada and the U.S.
7) Improving geophysics education.
8) The meaning of geophysical anomaly in exploration.
BASEMENT FAULT CONTROL ON THE ALBERTA AND WILLISTON BASINS IN WESTERN CANADA
Free download of our Alberta Geological Survey atlas: click here!
Linear patterns in well locations commonly reflect linear distribution of oil and gas reservoirs. This suggests some control by basement faults.
Geophysical anomaly domains reflect some common patterns of geophysical anomalies. They may or may not correspond to geological domains in the basement, and should not be interpreted directly.
In the cratonic platformal basins of western Canada and U.S., hydrocarbon-exploration success has been aided by tracing subtle basement faults that affect the geology of the sedimentary cover.
Many gravity and magnetic lineaments are associated with basement faults, which sometimes control productive reservoir trends in the sedimentary cover. Continuation of such potential-field lineaments into undrilled areas often points to new exploration opportunities.
Steep brittle faults in the crystalline basement are often overlooked in seismic-data interpretations but are commonly represented by potential-field anomalies. Geological evidence from the Canadian Shield shows some of these faults and crustal weakness zones have existed since the Precambrian; geophysical and geological evidence suggests they continue across the Alberta Platform and into the Cordilleran interior.
Many basement faults coincide with lithofacies and thickness variations and peculiarities of hydrocarbon-reservoir distribution at various levels in the Phanerozoic platformal sedimentary cover in the Alberta and Williston basins. Reactivation of steep old faults and creation of new ones, during various tectonic stages, accommodated differential uplift, subsidence and tilting of crustal blocks - in turn affecting the structural and lithostratigraphic peculiarities in the cover.
Phanerozoic block faulting with many kilometers of vertical offset is obvious and well recognized in the Cordilleran foreland and miogeosyncline in the United States, where Precambrian crystalline basement rocks are exposed in the uplifted blocks' cores. In the craton in western Canada, however, the basement block structures are comparatively low-amplitude and subtle, and often overlooked.
Gravity anomalies, being controlled by lateral variations in the density of rocks, are particularly sensitive to vertical block offsets.
Cheap public-domain aeromagnetic data in most of Alberta and southern Saskatchewan offer a sufficiently detailed coverage to resolve all anomalies originating in the crystalline basement.
The sedimentary cover contains some magnetic anomaly sources, but these sources are usually very minor and they lack a general geologic correlation with hydrocarbon reservoirs. The usual gravity coverage of one station per township in western Canada is too sparse to resolve all the small basement-sourced gravity anomalies, but it is sufficient to identify regional trends and anomalies from broad sources. The gravitational potential field is simpler than its magnetic counterpart, and the rock-density causation of anomalies simplifies the rock-anomaly relationships further.
Exploration money can thus be saved if the cheap public-domain data, both gravity and magnetic, are analyzed in detail before any resort to the costly "high-resolution" surveys.
Many mathematical data-processing methods are available with modern computers, but, like any mathematical exercise, they are inherently abstract.
Only those processing methods can produce geologically meaningful anomaly information that have a basis in the physics of potential fields (which is universal) and the rock-anomaly relationships (which are specific to the study area).
Experience shows that no single, universally applicable "silver-bullet" data-processing or -display method brings to light the desirable subtle potential-field anomalies in all parts of the platformal sedimentary basins in western Canada.
In many areas, good results are obtained with horizontal gradients, vertical derivatives, and some convolution filters.
At all stages in data preparation and processing, steps that, in theory, could generate anomaly-like linear artifacts are kept to a minimum. In particular, we aim to minimize the use of bandpass wavelength filtering, because linear artifacts can be created due to Gibbs ringing. Besides, anomaly separation may be imperfect due to non-vertical filter roll-off, and the choice of cut-off wavelength could be challenged as arbitrary.
The most vivid displays of anomalies, in both raw and derivative maps, are often achieved with combined color-coding and line contouring of anomalies on the same map sheet. The anomalies in each platformal-basin area are not identical to those anywhere else, and in each area extensive experimentation is required with various techniques and parameters of data processing and display, as it is not known ahead of time which methods will produce the most geologically meaningful results.
Two fundamentally different types of crystalline-basement structures, formed in different tectonic conditions, are recognized in the North American craton in western Canada:
(1) Archean and Early Proterozoic ductile orogenic structures, and
(2) Middle Proterozoic to Recent cratonic ones.
The latter are usually brittle, steep, block-bounding faults. Brittle cratonic structures partly follow the ancient orogenic ones (as is the case with the large NE-trending Snowbird-Virgin River and Great Slave Lake-MacDonald fault systems), but also commonly cut across them. Although signatures of ancient ductile orogenic structures predominate in potential-field maps, brittle block-bounding faults had the most influence on the evolution of platformal sedimentary basins.
Distribution patterns of oil, gas, coal and mineral deposits in the Alberta and Williston basins partly follow regional and local linear trends. Cratonic block-bounding faults are recognizable from their subtle potential-field signatures, as well as from their effects on the distribution of depocenters and arches at various levels in the Phanerozoic sedimentary cover.
Because the exact ways in which basement faults control the structure and lithofacies in the platformal sedimentary cover are manifold and often unclear, the obvious predictive power of this basement-cover relationship has been underutilized in exploration. To improve the exploration methodology, we use comprehensive geological and geophysical analysis to clarify the nature and timing of this fault control.
The modern relief of the Alberta and Williston basins' cratonic crystalline basement (misleadingly referred to sometimes as "basement structure") contains features of two dissimilar main types, which exerted very different influences on the sedimentary cover.
One basement-relief type is Precambrian erosional remnants, formed when the future platforms' basement was exposed at the surface. This part of the basement relief might bear some connection with the ancient ductile orogenic structures, linked to which is the distribution of variously resistant and recessive basement rocks. However, these old ductile structures were not reactivated subsequently, and the erosional basement relief passively affected only the lowest parts of the platformal sedimentary cover.
Studies of Hudsonian and older ductile orogenic basement structures are thus of limited utility for the practical needs of hydrocarbon exploration.
Of much more consequence for the Phanerozoic cover's evolution and hydrocarbon-trap distribution have been the post-orogenic, cratonic crustal warps and especially high-angle brittle faults, which have controlled the Phanerozoic movements of basement blocks. Some of these faults had formed in post-Hudsonian Precambrian time, and were already available for reactivation even at the onset of early Paleozoic deposition. Others formed later, at various times in the Phanerozoic.
Steep basement fractures and faults tend to be expressed poorly in seismic reflection profiles, especially if their vertical offsets in the sedimentary cover are less than 10 m. Details of basement-cover relationships in Alberta are hard to resolve seismically for another reason as well: the lower Paleozoic cover rocks commonly have seismic velocities similar to those in the uppermost part of the crystalline basement, so the basement-cover contact may lack a clear seismic signature.
Geophysically, steep cratonic block-bounding faults are recognizable from their subtle gravity and magnetic signatures. The steep fractures' diagnostic but largely subtle gravity and magnetic anomalies are commonly masked by strong but undesirable anomalies related to ancient ductile structures. Gravity and magnetic lineaments are identified based on a variety of anomaly criteria - linear breaks and discontinuities in the pattern of anomaly shapes, wavelengths, orientations and amplitudes; alignments of local anomalies; gradient zones; various subtle features that appear in derivative maps.
These brittle faults in the Alberta and Williston basins are seen to be regionally and locally pervasive, and detailed processing of gravity, magnetic and 3-D seismic data reveals their presence even on a township and smaller prospect scales.
Geologically, basement faults are expressed by their effects on the distribution of modern surface lineaments and, crucially, depocenters, arches and facies trends at various levels in the sedimentary cover.
The geologic history of basin-controlling vertical movements and tilting of basement blocks is thus reconstructible from the rock record, having been recorded in the preserved geologic variations within the cover.
Uplifted blocks produced the arches, whereas downdropped ones controlled the depocenters.
Some thickness and facies variations within the depocenters also indicate block tilts. Structural effects such as these are apparent at all stratigraphic levels in the cover, from Paleozoic to Cenozoic. From many detailed geological and seismic studies, these effects are seen to be common even on a prospect scale. For example, many major petroliferous Paleozoic reef trends in Alberta run NE-SW, and NE-SW/NW-SE trends are observed commonly in Cretaceous fluvial channel deposits.
Because all the Phanerozoic basement faults were not active during every stage of the platforms' evolution, and some faults that were active possess no detectable geophysical signatures, the correlation between inferred basement fault networks and geologic variations in the cover should never be expected to be immaculately 1:1.
Causal connections are nonetheless suggested by the evident partial basement-cover correlations.
The same orthogonal lineament families - NE-SW/NW-SE and weaker N-S/E-W - are widespread in the Plains and Canadian Shield topography. In detail, the collections of surface trends differ from area to area. The NNW-SSE topographic trends, for example, are common in northern Alberta, gradually changing to largely NW-SE in central Alberta and largely WNW-ESE in the south of the province. In the northern Williston Basin in Saskatchewan, the pattern of geological, geophysical and topographic lineaments is more complicated, as many observed trends are variously NNW-SSE/ENE-WNW and WNW-ESE/NNE-SSW, as well as N-S/E-W.
In various combinations, at 90-degree and 120-degree angles, these fractures combined into conjugate pairs that were newly created or available for reactivation at various times in the fluctuating regional stress field. Some steep fractures propagated not from the basement up but from the ground surface down, as some detailed coal-field studies suggest to be the case for fractures caused by Laramide crustal flexure in pericratonic areas. Which fracture pairs were active during which times, and in what fashion, is inferred from their preserved effects in various horizons in the sedimentary cover.
Free download of our Alberta Geological Survey atlas: click here!
The depocenter-arch patterns at various levels in the cover reflect periods of relative tectonic stability, punctuated by episodic crustal restructuring when the depocenter-arch configurations changed. As the patterns of raised, lowered and tilted blocks changed during restructuring, so did the patterns of depocenters and arches. Some of the block-related depocenters and arches persisted through several tectonic stages, others vanished temporarily or for good, and new ones occasionally appeared. Yet, usually these depocenters and arches followed the same, long-lived families of basement faults.
The famous Peace River Arch/Embayment in northern Alberta, for example, is well known to have manifested itself repeatedly during the Phanerozoic, variously as a composite positive or negative feature hundreds of meters in vertical amplitude, creating at different times either a depocenter or an arch.
Similar block fluctuations and inversions, with smaller amplitudes, are recognized throughout the Alberta and Williston basins. Many of the linear boundaries of geologically reconstructed, large and small depocenters and arches all over these basins have been found to coincide with strong and subtle, basement-sourced gravity and magnetic anomalies.
In this basement-cover association lies the predictive exploration power of our approach.
Free download of our Alberta Geological Survey atlas: click here!
CONCLUSIONS: IMPORTANCE OF BASEMENT STUDIES
On these principles, the following Phanerozoic cratonic tectonic stages, represented by their characteristic rock assemblages, have been distinguished in the Alberta Basin:
(1) Early/Middle Cambrian to Silurian;
(2) Devonian to Early Mississippian;
(3) Late Mississippian to Triassic;
(4) Jurassic to Early Cretaceous;
(5) late Neocomian to middle Late Cretaceous;
(6) Late Cretaceous Campanian to ?Early Tertiary;
(7) Pliocene to Recent.
These essentially cratonic tectonic stages bear little connection with the evolution of the Cordillera. They also differ from the hypothetical stages of Sloss, for two main reasons:
(1) Sloss' unconformity-bounded Sequences were determined for the U.S. Midcontinent Platform, not the Interior Platform in Canada; and
(2) Sloss failed to distinguish between platform-scale unconformities of tectonic and non-tectonic (e.g., eustatic) origin, thus leaving the geologic nature of his Sequences undefined.
By offering a way to elucidate the timing and nature of basement-fault control on the evolution of the platformal cover, our approach provides a sound, practical methodology for delineating the crustal structures that had a controlling influence on the evolution of and reservoir distribution in large cratonic platformal regions. This analysis is done inexpensively, with geological and geophysical data already available.
Confirmed association of hydrocarbon reservoirs with traceable deeper structures gives our improved understanding of basement structural control the useful predictive power.
QUEEN CHARLOTTE BASIN OFFSHORE WESTERN CANADA
This is a brief summary. See my CSEG Recorder article for more details.
A potential frontier oil-bearing province lies offshore along the west coast of Canada, in the shelf region between the mainland on the east and the Queen Charlotte Islands (Haida Gwaii) and Vancouver Island on the west.
Renewed interest in shelf basins of western Canada results from widespread expectations that the long-standing offshore-exploration moratorium there may be lifted. Lyatsky Geoscience, having studied this region for over 20 years, concludes that the best oil prospects probably exist in Cretaceous reservoirs in the Queen Charlotte Basin, particularly in western Queen Charlotte Sound.
Large oil accumulations would be needed to justify investment in this high-cost frontier environment. Tofino, Winona, Georgia, and Juan de Fuca basins lack significant known oil-source rocks, although accessibility of the last two basins makes gas exploration plausible. Yet, the southwestern part of the Queen Charlotte Basin seems to contain a stack of source, reservoir, and caprock strata, largely at oil-window burial depths, as well as large block-fault trap structures.
Encouraged by oil seeps from rocks of all ages, two dozen wells were drilled in the Queen Charlotte and Tofino areas mostly in the 1950s and 1960s, eight of them in the Queen Charlotte Basin offshore: six in Hecate Strait, two in Queen Charlotte Sound. However, Queen Charlotte Islands mostly lack caprock, Hecate Strait seems to lack adequate source and reservoir rocks (see below), and the offshore wells did not significantly test the Mesozoic horizons. Rocks on the mainland are mostly crystalline.
Economic basement in the Queen Charlotte Basin area is massive, thick Upper Triassic flood basalts, underlain onshore by partly metamorphosed older rocks. Above, good source rocks exist in the ~1000-m-thick Upper Triassic-Lower Jurassic assemblage, with Type I and II kerogen and TOC up to 11%. Geochemical evidence suggests these rocks provided most of the basin’s oil; a major pulse of oil generation and migration was in the Tertiary. The overlying Upper Jurassic-Upper Cretaceous clastic succession, ~3000 m thick, has negligible source potential but contains high-quality reservoirs with (largely secondary) porosity of 5-15%. Above, mostly offshore, lie Tertiary mudstone, sandstone, and volcanic deposits, up to ~6000 m thick in some fault-bounded depocenters.
Tertiary deposits have Type III and II kerogen, with up to 2.5% TOC locally, but clay products of feldspar decomposition greatly degrade their permeability, especially at basal levels. Reservoir-quality sandstone facies lie mostly near the top of this unit, where migration routes from below and the seal above may be inadequate. We regard the Tertiary deposits as predominantly caprock, perhaps with secondary exploration targets.
Stratigraphic and sedimentological studies indicate the Triassic-Jurassic source rocks were deposited in a broad shelfal basin encompassing this entire region and beyond. However, the Cretaceous basin was confined to western Queen Charlotte Islands and northwestern Vancouver Island, with uplands to the east shedding detritus. Western Queen Charlotte Sound was probably part of this basin, while eastern Queen Charlotte Sound and Hecate Strait largely lost their source rocks and received few Cretaceous deposits. Tertiary caprock, with thickness varying block to block, then blanketed Hecate Strait and Queen Charlotte Sound. Western Queen Charlotte Sound could thus contain a favorable source-reservoir-seal stack.
Gravity data also indicate a great thickness of low-density (sedimentary?) rocks is present beneath western Queen Charlotte Sound but not elsewhere in the basin.
Caprock-breaching faults are sparser in Queen Charlotte Sound than in Hecate Strait. Regional geological and geophysical correlations suggest Cenozoic reactivation of major Mesozoic block-fault networks. Seismic and gravity data show the faults to be comparatively sparse, and depocenters and raised blocks comparatively broad, in western Queen Charlotte Sound.
The caveats are several. Cretaceous rocks, deposited near their provenance areas, tend to be petrologically immature, and secondary porosity in them may be hard to predict. Buried source rocks in the deepest depocenters may be thermally overmature. Some traps may be breached by Neogene faults: the Sockeye B-10 offshore well encountered oil staining, suggesting oil passed through these Tertiary rocks and escaped. A major influence on local hydrocarbon-maturation levels on Queen Charlotte Islands is proximity to the Jurassic and Tertiary igneous plutons. Similar potential-field anomalies suggests massive igneous bodies may be present beneath eastern Queen Charlotte Sound, and correlations with mainland igneous suites put the age of these suspected plutons at Miocene. Pluton-related magnetic anomalies do not seem to significantly extent into western Queen Charlotte Sound.
To improve basin delineation, further exploration in this prospective area could include seismic and potential-field surveys, plus re-examination of relevant aspects of onshore geology.
Cretaceous strata beneath western Queen Charlotte Sound are a prime exploration target.
Overseas, Lyatsky Geoscience has completed a regional study of the petroleum geology of the Chinese and ex-Soviet Central Asia, which resulted in several publications by the previous partner (Dr. Vadim Lyatsky, my father) and his oil-industry collaborators, as well as a released atlas containing 17 plates and a transparent overlay.
Per day domestic/international -- CAD/USD$950; per hour -- CAD/USD$135;
or on per-project basis by agreement with client
Dr. HENRY LYATSKY
"In 1966, Andy Dufresne escaped from Shawshank prison. All they found of him was a muddy set of prison clothes, a bar of soap, and an old rock hammer, damn near worn down to the nub. I remember thinking it would take a man six hundred years to tunnel through the wall with it. Old Andy did it in less than twenty. Oh, Andy loved geology. I imagine it appealed to his meticulous nature. An ice age here, million years of mountain building there. Geology is the study of pressure and time. That's all it takes really, pressure, and time." -- Morgan Freeman's character in "The Shawshank Redemption" the movie.
Educated in both exploration geophysics and geology, Dr. Henry Lyatsky, P.Geoph., P.Geol. has worked extensively in the oil and mineral industries, as well as in government and academia.
EMPLOYABILITY IN THE UNITED STATES AND MEXICO
Full client-contract and employment rights under NAFTA
LANGUAGES --- good Russian, some German
"...The worst of all peasants are the so-called educated. These people should not only be prevented from learning to read, but from learning to talk as well. No need to prevent them from thinking; nature has done that." -- William S. Burroughs
Ph.D., geology, 1992, University of British Columbia, Vancouver
M.Sc., geophysics, 1988, University of Calgary
B.Sc., geology and geophysics, 1985, University of Calgary
CSEG (Canadian Society of Exploration Geophysicists)
MEG (Mineral Exploration Group)
APEGA (Association of Professional Engineers and Geoscientists of Alberta)
VOLUNTEER COMMUNITY WORK
Calgary Mineral Exploration Group
* President 2006-2008
* Vice-President 2002-2006
* Secretary 2000-2002
Chair, Calgary Mining Forum 2005
University of Calgary Geoscience Alumni Chapter
* Director 2010-2014
Political management and campaigns
"Nature within her inmost self divides
To trouble men with having to take sides." -- Robert Frost
"...There is no such thing as society. There are individual men and women, and there are families. And no government can do anything except through people, and people must look to themselves first. It's our duty to look after ourselves and then, also to look after our neighbour. People have got the entitlements too much in mind, without the obligations. There's no such thing as entitlement, unless someone has first met an obligation." -- Margaret Thatcher
Conservative Party of Canada and - in the Ralph Klein days - Alberta Progressive Conservative Party
Numerous campaign-management and constituency-executive positions
(These days, provincially, I am all United Conservative Party, of course)
LIST OF PUBLICATIONS
BOOKS AND ATLASES
Lyatsky, H.V., Pana, D.I. and Grobe, M., 2005. Basement Structure in Central and Southern Alberta: Insights from Gravity and Magnetic Maps; Alberta Geological Survey, Special Report 72 (with 56 maps and an interpretive note).
Lyatsky, H.V. and Pana, D.I., 2003. Catalogue of Selected Regional Gravity and Magnetic Maps of Northern Alberta; Alberta Geological Survey, Special Report 56 (with 35 maps and an interpretive note).
Lyatsky, H.V. and Lyatsky, V.B., 1999. The Cordilleran Miogeosyncline in North America - Geologic Evolution and Tectonic Nature; Lecture Notes in Earth Sciences 86, Springer-Verlag, 384 p.
Lyatsky, H.V., Friedman, G.M., and Lyatsky, V.B., 1999. Principles of Practical Tectonic Analysis of Cratonic Regions, with Particular Reference to Western North America; Lecture Notes in Earth Sciences 84, Springer-Verlag, 369 p., 3 color fold-outs.
Lyatsky, H.V., 1996. Continental-Crust Structures on the Continental Margin of Western North America; Lecture Notes in Earth Sciences 62, Springer-Verlag, 352 p.
PAPERS AND ARTICLES
Lyatsky, H.V., 2017. Knowledge true and false: scientific logic and climate change; Recorder (Canadian Society of Exploration Geophysicists), v. 42, no. 2, p. 26-30.
Lyatsky, H.V., 2016. Gravity and magnetic geophysical methods in oil exploration; E&P Magazine, October 2016, p. 52-54.
Lyatsky, H.V., 2010. Magnetic and gravity methods in mineral exploration: the value of well-rounded geophysical skills; Recorder (Canadian Society of Exploration Geophysicists), v. 35, no. 8, p. 30-35.
Lyatsky, H.V., 2009. BC's silent majority key to Queen Charlotte basin oil; Oil and Gas Journal, v. 107, no. 38, p. 31-34.
Lyatsky, H.V., 2006. Frontier next door: geology and hydrocarbon assessment of sedimentary basins offshore western Canada; Recorder (Canadian Society of Exploration Geophysicists), v. 31, no. 4, p. 66-75.
Lyatsky, H.V., Pana, D., Olson, R., and Godwin, L., 2004. Detection of subtle basement faults with gravity and magnetic data in the Alberta Basin, Canada: a data-use tutorial; The Leading Edge, v. 23, no. 12, p. 1282-1288.
Lyatsky, H.V., 2004. The meaning of anomaly; Recorder (Canadian Society of Exploration Geophysicists), v. 29, no. 6, p. 50-51.
Lyatsky, H.V., Pana, D., Olson, R., and Godwin, L., 2003. Mapping of basement faults with gravity and magnetic data in northern Alberta; Recorder (Canadian Society of Exploration Geophysicists), v. 28, no. 5, p. 38-40.
Lyatsky, H.V., 2003. British Columbia's geology holds promise of significant reserves; Offshore, v. 63, no. 3, p. 34-35.
Lyatsky, H.V., 2003. Institutional Review - Lyatsky Geoscience Research & Consulting Ltd.; in W. Lee, H. Kanamori, P. Jennings, and C. Kisslinger (eds.), International Handbook of Earthquake and Engineering Seismology, Part B (International Geophysics, Vol. 81B); Elsevier/Academic Press, summary on p. 1313, full report on attached CD #2 under directory 7912Canada.
Lyatsky, H.V., 2003. Contribution to the Canadian National Report; Canadian National Quadrennial Report to IASPEI-IUGG2003 (Sapporo, Japan), p. 9-11.
Lyatsky, H.V., 2000. Cratonic basement structures and their influence on the development of sedimentary basins in western Canada; The Leading Edge, v. 19, no. 2, p. 146-149.
Lyatsky, H.V., 2000. Ancient crystalline basement in western Canada: its influence on the platformal sedimentary cover, and basement remnants across the Cordillera; in: F. Cook and P. Erdmer (comps.), Slave-Northern Cordillera Lithospheric Evolution (SNORCLE) Transect and Cordilleran Tectonics Workshop Meeting, University of Calgary; Lithoprobe Report # 72, p. 232-243.
Edwards, D.J., Lyatsky, H.V., and Brown, R.J., 1998. Regional interpretation of steep faults in the Alberta Basin from public-domain gravity and magnetic data: an update; Recorder (Canadian Society of Exploration Geophysicists), v. XXIV, no. 1, p. 15-24 (reprinted in part from Edwards, Lyatsky and Brown, 1996 at the request of the Canadian Society of Exploration Geophysicists).
Lyatsky, H.V. and Dietrich, J.R., 1998. Mapping Precambrian basement structure beneath the Williston Basin in Canada: insights from horizontal-gradient vector processing of regional gravity and magnetic data; Canadian Journal of Exploration Geophysics, v. 34, p. 40-48.
Edwards, D.J., Lyatsky, H.V., and Brown, R.J., 1996. Interpretation of gravity and magnetic data using the horizontal-gradient vector method in the Western Canada Basin; First Break, v. 14, p. 231-246.
Edwards, D.J., Lyatsky, H.V., and Brown, R.J., 1995. Basement fault control on Phanerozoic stratigraphy in the Western Canada Sedimentary Province: integration of potential-field and lithostratigraphic data; in: G.M. Ross (ed.), Alberta Basement Transects Workshop, Lithoprobe Report #47, Lithoprobe Secretariat, University of British Columbia, p. 181-224.
Lyatsky, H.V., 1994. Formation of non-compressional sedimentary basins on continental crust: limitations on modern models; Journal of Petroleum Geology, v. 17, p. 301-316.
Lyatsky, H.V. and Haggart, J.W., 1993. Petroleum exploration model for the Queen Charlotte Basin area, offshore British Columbia; Canadian Journal of Earth Sciences, v. 30, p. 918-927.
Lyatsky, H.V., 1993. Basement-controlled structure and evolution of the Queen Charlotte Basin, west coast of Canada; Tectonophysics, v. 228, p. 123-140.
Lyatsky, H.V., Thurston, J.B., Brown, R.J., and Lyatsky, V.B., 1992. Hydrocarbon-exploration application of potential-field horizontal-gradient vector maps; Recorder (Canadian Society of Exploration Geophysicists), v. XVII, no. 9, p. 10-15.
Lyatsky, H.V. and Haggart, J.W., 1992. New petroleum prospects on the west coast of Canada; Oil and Gas Journal, v. 90, no. 34, p. 53-56.
Lyatsky, H.V., 1991. Diachronous acoustic basement in seismic reflection data from the Queen Charlotte Basin, British Columbia; in: Current Research, Part A; Geological Survey of Canada, Paper 91-1A, p. 401-407.
Lawton, D.C. and Lyatsky, H.V., 1991. Density-based reflectivity in seismic exploration for coal in Alberta, Canada; Geophysics, v. 56, p. 139-141.
Lyatsky, H.V., 1991. Regional geophysical constraints on crustal structure and geologic evolution of the Insular Belt, British Columbia; in: G.J. Woodsworth (ed.), Evolution and Hydrocarbon Potential of the Queen Charlotte Basin, British Columbia; Geological Survey of Canada, Paper 90-10, p. 97-106.
Lyatsky, V.B. and Lyatsky, H.V., 1990. Integrated geological basin analysis as a method of hydrocarbon exploration on continental shelves; Proceedings, 22nd Offshore Technology Conference, Houston, p. 237-242.
Lawton, D. and Lyatsky, H.V., 1989. Advances in reflection seismic methods for shallow coal exploration in western Canada; in: W. Langenberg (comp.), Advances in Western Canadian Coal Geoscience; Alberta Research Council, Information Series No. 103, p. 330-340.
Lyatsky, H.V. and Lawton, D.C., 1989. Reflection seismic study of a Lower Paleocene coal deposit, Wabamun, Alberta; in: Geophysical Atlas of Western Canadian Hydrocarbon Pools; Canadian Society of Exploration Geophysicists & Canadian Society of Petroleum Geologists, Calgary, p. 301-310.
Lyatsky, H.V. and Lawton, D.C., 1988. Application of the surface reflection seismic method to shallow coal exploration in the Plains of Alberta; Canadian Journal of Exploration Geophysics, v. 24, p. 124-140.
OTHER PROFESSIONAL PUBLICATIONS
Lyatsky, H.V., 2017. The air war for oil: why we lose and how to win; The Source (Canadian Association of Geophysical Contractors), v. 13/4, p. 31-32.
Lyatsky, H.V. and Heinrichs, B., 2013. Oilsands not an economy-environment tradeoff; Vancouver Sun, December 5, 2013.
Lyatsky, H.V., 2013. Members in the News; Recorder (Canadian Society of Exploration Geophysicists), v. 38, no. 4, p. 84.
Lyatsky, H.V., 2009. How I got involved in geophysics; Recorder (Canadian Society of Exploration Geophysicists), v. 34, no. 8, p. 40.
Hawkins, P.A. and Lyatsky, H.V., 2005. The other industry - the mining community in Calgary; The PEGG (Association of Professional Engineers, Geologists and Geophysicists of Alberta), v. 33, no. 2, p. 28.
Hawkins, P.A. and Lyatsky, H.V., 2004. The Calgary Mineral Exploration Group; Recorder (Canadian Society of Exploration Geophysicists), v. 29, no. 10, p. 51.
Card, C., Pana, D., Ashton, K., Lyatsky, H., Ramaekers, P., Wheatley, K., Thomas, D., Koning, E., Slimmon, W., Gilboy, C., Bethune, K., and Leppin, M., 2003. Subproject 5: Basement to western Athabasca Basin; in: Jefferson, C.W., Delaney, G., and Olson, R.A., EXTECH IV Athabasca Uranium Multidisciplinary Study of Northern Saskatchewan and Alberta, Part 2: Current Results of Subprojects 1 to 5; Geological Survey of Canada, Current Research 2003-C19, p. 5-6.
Lyatsky, H.V., 2002. Commentary: Failure to Teach; Geolog (Geological Association of Canada), v. 31, part 1, p. 15.
Lyatsky, H.V., 2000. Stay practical! (Letter to the editor); Geolog (Geological Association of Canada), v. 29, part 4, p. 15.
Lyatsky, H.V., 2000. Responsible organization of geoscience research in Canada (Commentary column); Geolog (Geological Association of Canada), v. 29, part 2, p. 17.
Lyatsky, H.V., Dietrich, J.R., and Edwards, D.J., 1998. Analysis of Gravity and Magnetic Horizontal-Gradient Vector Data Over the Buried Trans-Hudson Orogen and Churchill-Superior Boundary Zone in Southern Saskatchewan and Manitoba; Geological Survey of Canada, Open File 3614, 34 p.
Edwards, D.J. and Lyatsky, H.V., 1996. Synthetic modelling of Bouguer gravity horizontal-gradient vector data; Newsletter of the Lithoprobe Seismic Processing Facility, v. 9, no. 2, p. 45-49.
Lyatsky, H.V., 1994. Book review of 'Foreland Basins and Fold Belts', American Association of Petroleum Geologists, Memoir 55; Journal of Petroleum Geology, v. 17, p. 247-248.
Edwards, D.J., Brown, R.J., and Lyatsky, H.V., 1994. Interpreting potential fields with the horizontal gradient vector (HGV): a short note using examples from central Alberta, Canada; Newsletter of the Lithoprobe Seismic Processing Facility, University of Calgary, v. 7, no. 2, p. 64-70.
Lyatsky, H.V., Haynes, A.K., Brown, R.J., Thurston, J.B., and Lyatsky, V.B., 1991. Aeromagnetic Horizontal-Gradient Vector Map of the Queen Charlotte Basin Area, British Columbia; Geological Survey of Canada, Open File 2436 (scale 1:1,000,000).
Lyatsky, V.B., Brown, R.J., and Lyatsky, H.V., 1990. The Use of Potential-Field Horizontal-Gradient Vector Data in Hydrocarbon Exploration; A.P. Holder (ed.), Lyatsky Geoscience Research and Consulting Ltd., Calgary, 26 p.
Lyatsky, H.V., 1988. Screen Graphics Manual For the Tektronix 4107 Terminal Used With the Perkin-Elmer System; Dept. of Geology & Geophysics, University of Calgary, 69 p.
Dietrich, J.R. and Lyatsky, H.V., 1985. A Structural and Stratigraphic Study of Reflection Seismic Data Over the Kopanoar Prospect in the Central Beaufort Sea; Geological Survey of Canada, Petroleum Appraisal Secretariat, Calgary, 7 p.
ABSTRACTS OF PRESENTATIONS
Few abstracts are formally published these days, but I continue to make presentations regularly. This list is very incomplete as it does not include the many presentations, as well as radio and TV appearances, for which no abstract was formally published.
Lyatsky, H.V., 2013. Natural fracture patterns in the Alberta Basin: don't forget the basement!; Reservoir (Canadian Society of Petroleum Geologists), v. 40, no. 5, p. 15.
Lyatsky, H.V., 2010. Self-promotion for consultants and start-ups: lessons from business and politics; 19th Calgary Mining Forum, Abstracts, p. 22-23.
Enachescu, M., Lyatsky, H.V., Colton, P., Einarsson, P., and Feir, A., 2009. Synergistic interpretation of Labrador Sea geophysical data; Canadian Society of Petroleum Geologists, Canadian Society of Exploration Geophysicists, Canadian Well Logging Society, Annual Convention, Calgary, Program, p. 737-740.
Enachescu, M.E., Lyatsky, H.V., Colton, P., and Einarsson, P., 2009. Integrated interpretation of reflection seismic, potential field and petroleum geology data in the Hopedale Basin, Canadian Labrador Sea; American Association of Petroleum Geologists, Annual Convention, Denver.
Lyatsky, H.V., 2007. Sedimentary basins offshore western Canada and their petroleum prospects; Reservoir (Canadian Society of Petroleum Geologists), v. 34/4, p. 13-15 and v. 34/5, p. 8-9.
Lyatsky, H.V., Pana, D.I., Grobe, M., Meerburg, G., and Godwin, L., 2006. Basement structure in the Alberta Basin, Canada from gravity and magnetic studies; Canadian Society of Petroleum Geologists, Canadian Society of Exploration Geophysicists, Canadian Well Logging Society, Annual Convention, Calgary, Program, p. 236.
Lyatsky, H.V., Pana, D.I., Grobe, M., and Godwin, L., 2005. Alberta regional basement structure from gravity and magnetic data: implications for mineral exploration; 14th Calgary Mining Forum, Abstracts, p. 30.
Lyatsky, H.V., 2003. Hydrology applications of fault-network identification in northern Alberta from gravity and magnetic data; Reservoir (Canadian Society of Petroleum Geologists), v. 30, no. 8, p. 16.
Lyatsky, H.V., Pana, D., Olson, R., and Godwin, L., 2003. Mapping of basement faults with gravity and magnetic data in northern Alberta; Canadian Society of Petroleum Geologists, Canadian Society of Exploration Geophysicists, Joint Convention, Calgary (long abstract reprinted as an article in the Canadian Society of Exploration Geophysicists magazine Recorder).
Haggart, J.W., Dietrich, J.R., and Lyatsky, H.V., 2003. Petroleum geology framework, West Coast Offshore region; Canadian Society of Petroleum Geologists, Canadian Society of Exploration Geophysicists, Joint Convention, Calgary.
Lyatsky, H.V., Pana, D., and Olson, R., 2003. Delineation of fault networks in NE Alberta with gravity and magnetic data; 12th Calgary Mining Forum, Abstracts, p. 42.
Pana, D., Lyatsky, H.V., and Creaser, R.A., 2003. Uranium potential of basement rocks in the Alberta portion of the Athabasca Basin: integrated geophysical, geological and isotopic studies; 12th Calgary Mining Forum, Abstracts, p. 70.
Haggart, J.W., Dietrich, J.R., and Lyatsky, H.V., 2003. Petroleum geology of Canada's west coast offshore region; Geological Association of Canada, Mineralogical Association of Canada, Society of Exploration Geochemists, Annual General Meeting, Vancouver, v. 28, abstract #720.
Lyatsky, H.V., 2002. Various forms of basement influence on the North American cratonic sedimentary cover; Reservoir (Canadian Society of Petroleum Geologists), v. 29, no. 1, p. 16 (reviewed in Nickle's New Technology Magazine, March 2002, Exploration Technology section, p. 28-29).
Lyatsky, H.V. and Marchand, M., 2001. The Calgary Mining Forum (conference report); Geolog (Geological Association of Canada), v. 30, part 2, p. 26.
Haggart, J.W., Dietrich, J.R., and Lyatsky, H.V., 2001. Petroleum geology of Queen Charlotte Islands (QCI) region, British Columbia, Canada; American Association of Petroleum Geologists, Annual Convention, Denver; Program and Abstracts, A78.
Lyatsky, H.V., 2000. Reassessment of West Coast earthquake risk; Reservoir (Canadian Society of Petroleum Geologists), v. 27, no. 8, p. 18.
Lyatsky, H.V., 2000. Potential Mesozoic petroleum province offshore B.C. and Alaska; Reservoir (Canadian Society of Petroleum Geologists), v. 27, no. 3, p. 16.
Lyatsky, H.V., 2000. Basement-cover relationships in the cratonic platforms of western Canada: methodology of practical geological analysis; presented at the GeoCanada2000 conference (Geological Association of Canada, Mineralogical Association of Canada, Canadian Well Logging Society, Canadian Geophysical Union, Canadian Society of Exploration Geophysicists, Canadian Society of Petroleum Geologists), Calgary.
Lyatsky, H.V., 2000. Continuity of indigenous ancient North American crust across the Canadian Cordillera - a review of evidence; presented at the GeoCanada2000 conference (Geological Association of Canada, Mineralogical Association of Canada, Canadian Well Logging Society, Canadian Geophysical Union, Canadian Society of Exploration Geophysicists, Canadian Society of Petroleum Geologists), Calgary.
Lyatsky, H.V., 1999. Basement in western Canada - its influence on the platformal sedimentary cover and the Cordilleran orogenized zones; Reservoir (Canadian Society of Petroleum Geologists), v. 26, no. 10, p. 17-18.
Lyatsky, H.V., 1999. Methodology for delineation of cratonic crustal structures; 8th Calgary Mining Forum, Program, unpaginated.
Lyatsky, H.V. and Haggart, J.W., 1999. A potential frontier petroleum province offshore British Columbia; Canadian Society of Exploration Geophysicists, 1999 Convention, Calgary, Abstract Book, p. 187.
Lyatsky, H.V., 1999. Continuity into the Cordilleran interior from the North American craton of Archean and Proterozoic transverse crustal structures: evidence from geological and potential-field data; in: F. Cook and P. Erdmer (comps.), Slave-Northern Cordillera Lithospheric Evolution (SNORCLE) Transect and Cordilleran Tectonics Workshop; Lithoprobe Report #69, p. 299-304.
Dietrich, J.R., Thomas, M.D., Hajnal, Z., Redly, P., Zhu, C., Lyatsky, H.V., and Majorowicz, J.A., 1998. Basement-sedimentary cover relationships in the Williston Basin of southeast Saskatchewan and southwest Manitoba: insights from regional geophysical studies; in: J.E. Christopher, C.F. Gilboy, D.F. Paterson, and S.L. Bend (eds.), Eighth International Williston Basin Symposium, Saskatchewan Geological Society, Special Publication 13, p. 176.
Lyatsky, H.V. and Dietrich, J.R., 1998. Delineation of fault networks from public-domain regional gravity and magnetic data in the Trans-Hudson Orogen in southern Saskatchewan and Manitoba; 7th Annual Calgary Mining Forum, Program, p. 53-54.
Lyatsky, H.V., Dietrich, J.R., and Edwards, D.J., 1997. Reprocessing and interpretation of regional gravity and magnetic data in the Trans-Hudson orogen beneath the Phanerozoic cover in southern Saskatchewan and Manitoba; Canadian Geophysical Union, 23rd Scientific Meeting, Banff, Alberta; Program & Abstracts, p. 24.
Dietrich, J.R., Magnusson, D.H., Lyatsky, H.V., and Hajnal, Z., 1997. Basement-sedimentary cover relationships along the Churchill-Superior boundary zone, southwestern Manitoba; Manitoba Mining & Minerals Convention '97, Winnipeg; Program, p. 33.
Lyatsky, H.V., 1997. Fault-bounded blocks of continental crust on the continental margin offshore western Canada: a geology-based revision of current models; Canadian Geophysical Union, 23rd Scientific Meeting, Banff, Alberta; Program & Abstracts, p. 38.
Dietrich, J.R., Magnusson, D.H., Lyatsky, H.V., Hajnal, Z., and Redly, P., 1997. Basement-sedimentary cover relationships in the eastern Williston Basin; Canadian Society of Petroleum Geologists & Society of Exploration Paleontologists and Mineralogists, Joint Convention, Calgary; Program with Abstracts, p. 80.
Lyatsky, H.V., 1997. Control of the western continental margin of North America by the Cordilleran Fairweather-Queen Charlotte-Wallowa fault system; in: F. Cook and P. Erdmer (comps.), Slave-Northern Cordillera Lithospheric Evolution (SNORCLE) Transect and Cordilleran Tectonics Workshop Meeting; Lithoprobe Report #56, p. 184-186.
Lyatsky, H.V. and Dietrich, J.R., 1997. Mapping Precambrian basement structure beneath the Williston Basin in southern Saskatchewan and Manitoba: insights from horizontal-gradient vector processing of public-domain aeromagnetic and gravity data; Canadian Society of Exploration Geophysicists, High-Resolution Aeromagnetics for Hydrocarbon Exploration Forum, Calgary; Program with Expanded Abstracts, unpaginated.
Lyatsky, H.V., 1996. Chairman's report on the General Geophysics session, Canadian Geophysical Union, 22nd Scientific Meeting; Elements (Canadian Geophysical Union), v. 14, no. 2, p. 5.
Lyatsky, H.V., 1996. Lineament analysis of potential-field data in the studies of basement structure; Reservoir (Canadian Society of Petroleum Geologists), v. 23, no. 1, p. 7.
Lyatsky, H.V. and Pratico, V., 1996. Applications of the magnetic and gravity horizontal-gradient vector (HGV) technique to regional mineral exploration; 5th Calgary Mining Forum; Program, p. 11.
Edwards, D.J., Lyatsky, H.V., and Brown, R.J., 1996. Using the horizontal-gradient vector method to assess the influence of basement faulting on the Phanerozoic cover of central Alberta; Current Research Symposium, Dept. of Geology and Geophysics, University of Calgary; Program & Abstracts, p. 38.
Lyatsky, H.V., Brown, R.J., and Edwards, D.J., 1996. Utility of magnetic and gravity horizontal-gradient vector (HGV) technique in hydrocarbon and mineral exploration; Canadian Geophysical Union, 22nd Scientific Meeting, Banff, Alberta; Program & Abstracts, p. 180 (presented in the General Geophysics session chaired by H.V. Lyatsky).
Edwards, D.J., Brown, R.J., and Lyatsky, H.V., 1995. Interpreting potential-field data with horizontal-gradient vector (HGV) mapping - examples from Alberta, Canada; European Association of Exploration Geophysicists, 57th Annual Meeting and Technical Exhibition, Glasgow, U.K.; Extended Abstracts of Papers, paper P-146.
Lyatsky, H.V., Edwards, D.J., and Brown, R.J., 1995. Influence of basement fault networks on evolution of sedimentary basins in North America; Canadian Geophysical Union, 21st Scientific Meeting, Banff, Alberta; Program & Abstracts, p. 48.
Edwards, D.J., Brown, R.J., and Lyatsky, H.V., 1995. Application of the horizontal-gradient vector method to gravity and magnetic data in central Alberta: the identification of reactivated basement faulting; Canadian Society of Exploration Geophysicists, National Convention, Calgary; Program & Expanded Abstracts, p. 123-124.
Lyatsky, H.V., 1993. Multidisciplinary studies in basin evolution: Jurassic examples; Arkell International Symposium on Jurassic Geology, London, U.K.; Abstracts of Poster Communications, unpaginated.
Lyatsky, H.V., 1993. Geophysical methods in a multidisciplinary study of western Canadian continental margin; European Association of Exploration Geophysicists, 55th Meeting and Technical Exhibition, Stavanger, Norway; Extended Abstracts of Papers, paper D-030.
Lyatsky, H.V. and Haggart, J.W., 1992. A new look at hydrocarbon potential, Queen Charlotte Basin area, British Columbia; Geological Survey of Canada, Oil and Gas Forum, Calgary; Program & Abstracts, p. 10.
Lyatsky, H.V. and Haggart, J.W., 1992. Hydrocarbon potential of the Queen Charlotte Basin area, British Columbia: a new assessment; presented at the Cordilleran Geology and Exploration Roundup, Vancouver.
Lyatsky, H.V., Haggart, J.W., Hickson, C.J., and Woodsworth, G.J., 1991. Diffuse continent-ocean boundary at the continental margin of western Canada; 38th Annual Pacific Northwest Meeting of the American Geophysical Union, Pasco, Washington; Abstract Volume, p. 23.
Lyatsky, H.V., Chase, R.L., Hickson, C.J., Thompson, R.I., and Woodsworth, G.J., 1991. Continental crust off the west coast of Canada?; presented at the Cordilleran Geology and Exploration Roundup, Vancouver.
Lyatsky, H.V., Chase, R.L., Lewis, P.D., Thompson, R.I., and Woodsworth, G.J., 1990. Block faulting and evolution of the Queen Charlotte (QC) Basin, west coast of Canada; EOS, Transactions of the American Geophysical Union, v. 71, p. 1581.
Lyatsky, H.V., Chase, R.L., Thompson, R.I., and Woodsworth, G.J., 1990. Alternative interpretation of geophysical data in the Queen Charlotte (QC) Basin Area, B.C.; EOS, Transactions of the American Geophysical Union, v. 71, p. 1143.
Brown, R.J., Thurston, J.B., Lyatsky, V.B., and Lyatsky, H.V., 1990. Regional gravity and magnetic data in integrated geological basin analysis; Canadian Society of Exploration Geophysicists, Annual Convention, Calgary; Program & Abstracts, p. 24-25.
Lyatsky, H.V., Seemann, D.A., and Woodsworth, G.J., 1990. Fault-block structure of the Insular Belt in Canada; Geological Association of Canada & Mineralogical Association of Canada, Annual Meeting, Vancouver; Program with Abstracts, p. A79.
Lyatsky, H.V., Currie, R.G., Seemann, D.A., Teskey, D.J., and Woodsworth, G.J., 1990. Magnetic and gravity studies in the Insular Belt, B.C.; Cordilleran Geology and Exploration Roundup, Vancouver; Program & Abstracts, p. 63-64.
Lawton, D.C., Holland, M., and Lyatsky, H.V., 1989. The influence of thin bed tuning on AVO analysis; Canadian Society of Exploration Geophysicists & Canadian Society of Petroleum Geologists, Joint Convention, Calgary; Program & Abstracts, p. 42.
Lyatsky, H.V. and Lawton, D.C., 1989. Reflection seismic modeling study of a shallow coal field in central Alberta; EOS, Transactions of the American Geophysical Union, v. 70, p. 139.
Lyatsky, H.V. and Yuan, T., 1989. Formation of non-compressional sedimentary basins on continental crust: stretching, simple shear and plume model; 25th Western Inter-University Geological Conference, Vancouver; Program & Abstracts, unpaginated.
Lyatsky, H.V. and Lawton, D.C., 1988. Reflection seismic modelling study of shallow coal deposits near Wabamun, Alta.; 24th Western Inter-University Geological Conference, Winnipeg; Program & Abstracts, unpaginated.
Lyatsky, H.V., 1987. Reflection seismic modeling study of Glauconitic channels in the Retlaw area, southern Alberta; Current Research Symposium, Dept. of Geology and Geophysics, University of Calgary; Program & Abstracts, unpaginated.
Lyatsky, H.V., 1987. Analysis of crustal geophysical data in the Kapuskasing Structural Zone, NE Ontario; 23rd Western Inter-University Geological Convention, Edmonton; Program & Abstracts, unpaginated.
Dietrich, J.R. and Lyatsky, H.V., 1986. Seismic stratigraphy of the Kopanoar oil field, Beaufort Sea; 22nd Western Inter-University Geological Convention, Saskatoon; Program & Abstracts, p. 19-20.
Lyatsky, H.V., 1992. Structure, Evolution, and Petroleum Potential of the Queen Charlotte Basin; Ph.D. dissertation, Dept. of Geological Sciences, University of British Columbia, Vancouver, 249 p., 3 enclosures.
Lyatsky, H.V., 1988. Reflection Seismic Study of a Shallow Coal Field in Central Alberta; M.Sc. thesis, Dept. of Geology and Geophysics, University of Calgary, 121 p.
Lyatsky, H.V., 1986. Analysis of Geophysical Data in the Kapuskasing Structural Zone, N.E. Ontario; B.Sc. thesis, Dept. of Geology and Geophysics, University of Calgary, 41 p.
I have taught a second-year undergraduate quarter-course in potential-field methods in geophysics at the University College London (University of London), U.K. My duties included lecturing, demonstrating, assessing students' homework and seminars, and setting and grading examinations. I have also taught a similar course segment at the University of Calgary. As well, I have lectured occasionally on potential-field methods to undergraduate students at the University of Calgary and other schools.
During my graduate studies, I worked part-time as a teaching assistant (demonstrator) in undergraduate courses of all levels in geology, geophysics and physics, as well as grading students' homework assignments, seminars and examination papers. I was involved in teaching courses in reflection seismic methods, integrated geophysical interpretation, geophysics field school, marine geology, stratigraphy, rock physics, introductory geology and introductory physics.
For almost three years after my return from the U.K., I took part in supervising a Ph.D. student at the University of Calgary. That effort resulted in several joint publications and conference abstracts, as well as a completed thesis by the student.
I have also conducted many seminars and tutorials on various topics in geology and geophysics at universities, government institutions and commercial companies in Canada, the United States, Mexico and Europe.
1988 - present:
PRIVATE CONSULTING PRACTICE, Calgary.
Interpretation of gravity and magnetic data in conjunction with seismic, geological and remote-sensing information; field acquisition and processing of potential-field data; integrated geological and geophysical studies of sedimentary basins; regional and local prospect delineation for hydrocarbon and mineral exploration; technical course instruction.
1993 - 1994:
UNIVERSITY OF LONDON, Research School of Geological & Geophysical Sciences, University College London & Birkbeck College, U.K.
Post-doctoral research fellow, geophysics instructor.
Regional and local gravity and seismic studies in the North Sea; subsalt hydrocarbon exploration; undergraduate instruction.
GEOLOGICAL SURVEY OF CANADA, Cordilleran Division, Vancouver.
Studies in structure, evolution and petroleum potential of the Queen Charlotte Basin and continental margin, British Columbia; field work on the mainland British Columbia.
GEOLOGICAL SURVEY OF CANADA, Cordilleran Division, Vancouver.
Regional geological and geophysical studies of the Queen Charlotte Basin and the Insular Belt in Canada; geological field work on the Queen Charlotte Islands and Gulf Islands, British Columbia.
GEOLOGICAL SURVEY OF CANADA, Pacific Geoscience Centre, Sidney, British Columbia.
Regional geological and geophysical studies of the Queen Charlotte Basin; geological field work on the Queen Charlotte Islands; field assistance in the LITHOPROBE Southern Cordilleran Refraction Experiment (SCORE '89); Western Canada Telemetry Network maintenance.
July 1986 - December 1986:
UNIVERSITY OF CALGARY, Department of Geology and Geophysics.
Processing of seismic reflection data and seismic modeling of shallow coal targets in central Alberta.
Fall 1984 - Spring 1985:
GEOLOGICAL SURVEY OF CANADA, Institute of Sedimentary and Petroleum Geology, Calgary.
Part-time contract researcher.
Structural and stratigraphic interpretation of seismic reflection data in the Canadian Beaufort Sea.
HOME OIL COMPANY LTD., Calgary.
Analysis and modeling of seismic reflection character for the purpose of identification of thin porosity zones in Middle Devonian carbonates in northwestern Alberta.
HOME OIL COMPANY LTD., Swan Hills, Alberta.
Pipeline maintenance operations in northern Alberta.
HOME OIL COMPANY LTD., Calgary.
Construction of geologic cross-sections and seismic time-structure maps; technical work.
EVOLUTION OF THE NORTH AMERICAN CORDILLERA IN RELATION TO THE ALBERTA BASIN
"I shall certainly admit a system as empirical or scientific only if it is capable of being tested by experience. ...Not the verifiability but the falsifiability of a system is to be taken as a criterion of demarcation. ...It must be possible for an empirical scientific system to be refuted by experience." -- Karl Popper
"...Those who uphold it dogmatically - believing, perhaps, that it is their business to defend such a successful system against criticism as long as it is not conclusively disproved - are adopting the very reverse of that critical attitude which in my view is the proper one for the scientist." -- Karl Popper
Erroneously regarding the craton to be inert and only passively responding to external influences, attempts are sometimes made to interpret the Phanerozoic tectonic evolution of the western part of the North American craton by applying tectonic templates assumed for the evolution of the neighboring Cordillera. This approach is illogical at its core. Possessing their own sources of radiogenic heat, continental lithospheric provinces can self-develop. The craton and the Cordillera are different tectonic provinces, with dissimilar indigenous tectonic stages.
The craton is the more ancient part of the continent, and a continent-wide study should begin with it. Besides, as this section will show, many existing speculative scenarios of the Cordilleran evolution are themselves in error, as they assume the Cordillera's development was driven entirely from without, by plate-boundary influences. These scenarios are model-driven, and they fail to consider the Cordilleran geology on its own terms.
The Cordillera evolved on the fringes of an ancient craton, and the inherited ancient ex-cratonic structures had a significant part in its orogenic development. Review of diverse geological and geophysical evidence shows that, contrary to some common misconceptions,
(1) the Canadian Cordilleran miogeosynclinal region has never contained an Atlantic-type passive continental margin, and
(2) the main differences between tectonic zones in the Cordilleran interior lie not in their assumed exotic-terrane composition but in the degree and history of in situ, multi-aspect, multi-cycle orogenic reworking of the indigenous, ex-cratonic North American lithosphere and crust.
Steep, deep-seated, long-lived crustal weakness zones are well known to have existed in the western part of the North American craton since Late Archean or Early Proterozoic time. Their recognition is based on reliable geological field mapping, subsurface geological studies and geophysical surveys conducted for decades in the Canadian Shield and adjacent Phanerozoic cratonic platforms. These ancient weakness zones are seen to continue far into the Cordilleran interior, where they influenced many tectonic manifestations throughout the Phanerozoic.
Trending mostly NE-SW, ancient crustal weakness zones divide the North American craton into distinct large blocks. Some of these zones predate cratonization, which occurred in the Early Proterozoic in Alberta and Saskatchewan and somewhat later in much of the U.S. Many more steep brittle faults, variously following and cutting across the ancient ductile structures, were created in the upper crust after cratonization.
Being generally unable to detect high-angle rock discontinuities, seismic reflection profiles may give the unwary a false, incomplete impression that only low-angle discontinuities exist in the continental crust. The nature, origin and age of these seismically reflective low-angle crustal discontinuities are unknown, and they could be related to a multitude of possible causes: original discontinuities in the protolith, subsequent superimposed metamorphic fronts and rheologic boundaries, ductile and brittle shearing, intrusive igneous bodies and so on. Most steep discontinuities are missed in seismic reflection images altogether, but they are better detected with potential-field data.
A geophysical anomaly, by itself, is unable to reveal the nature and age of its geologic source. Without direct geological observations, the inherent non-uniqueness of interpretations of the geophysically imaged geometries in the distribution of specific physical rock properties precludes definitive conclusions about the composition and structure of the deep crust. Even in the exposed and drilled uppermost part of the crust, every dry oil or water well, and every failed mining or geotechnical project, represents a failure of prediction.
Seismic experiments in crystalline terrains, where the multiply-reworked continental-basement rocks are exposed, show the reflectivity in these rocks to be exceedingly complex, with countless, variously oriented, unpredictable reflectors, refractors and diffractors. Superdeep wells drilled into the upper continental crust in Europe, Russia and North America have also presented many surprises quite unanticipated by prior geophysical predictions, including unexpected findings about sources of seismic reflections and potential-field anomalies, as well as position of the brittle-ductile boundary and thermal and hydrologic conditions. Not even such sparse geological constraints are available for the middle and lower crust. The arbitrary and model-driven assumption that seismic-reflection geometries deep in the continental crust mostly represent thrusting contradicts the existing geological observations and leads to an incorrect perception that continental crust is usually a stack of thrust sheets.
Another false myth in modern tectonics is that continental lithosphere is essentially inert, responding only passively to external influences from plate boundaries and sub-lithospheric mantle. Having its own sources of energy, continental lithosphere is capable of indigenously driven self-development, and external plate-boundary influences (subduction, terrane collisions etc.) and mantle plumes are not required to explain all intracontinental tectonism.
Rejuvenation of old steep weakness zones and fractures, and creation of new ones, in various crustal tectonic regimes and conditions, influenced block movements and the formation of volcano-sedimentary cratonic basins in the Proterozoic and Phanerozoic. The cratonic Proterozoic Athabasca Basin in northern Saskatchewan and Alberta, for example, has a polygonal, almost N-S/E-W shape, and it is cut internally by through-going NE-SW-trending block boundaries (notably, Virgin River-Snowbird).
Cratonic crustal block movements and warping in the Phanerozoic played a crucial part in the development of the cratonic platformal basins - Alberta, Williston and others. High-angle faults, rejuvenated sporadically in favorable stress regimes, imposed the widespread NE-SW/NW-SE and N-S/E-W pattern on the distribution of lithofacies and thicknesses at various levels in the sedimentary cover and strongly affected the distribution of hydrocarbon fields. These steep cratonic basement-rooted faults are commonly unnoticed in deep seismic surveys, but they are clearly recognizable from geologic variations in the sedimentary cover, neotectonic crustal movements, and potential-field anomalies.
On trend with the Proterozoic Athabasca Basin and the latest Proterozoic-Phanerozoic Peace River Arch in the western part of the craton, the prominent NE-SW-trending Skeena Arch in the Cordilleran interior has manifested its activity since at least the Mesozoic, dividing the Intermontane Belt into major crustal blocks and forming the southern boundary of the Bowser Basin. Some faults on trend with the Skeena Arch’s southern boundary have been noted to continue even into the Cordilleran Coast and Insular belts farther west. The other transcurrent arch in the Intermontane Belt, Stikine, which bounds the Bowser Basin on the north, has a similar nature. Mesozoic sedimentary basins in the Intermontane Belt - Bowser, Nechako, Whitehorse Trough - owe their existence to differential uplift, subsidence and tilting of crustal blocks separated by transverse and Cordillera-parallel crustal faults. Further indications of transcurrent crustal structures, against the background of predominant NNW-SSE trends, are NE-SW gravity and magnetic lineaments crossing much of the Cordillera, E-W-elongated Mesozoic igneous plutons, and NE-SW and E-W lakes and rivers.
Wide westward extent of ancient pre-Cordilleran craton(s) is suggested by other evidence as well. Tectonically reworked Precambrian rocks of various Archean and Proterozoic ages are recognized all over the Canadian Cordillera, while paleontological, paleomagnetic and structural evidence for exoticism of assumed accreted terranes is continually revised or eliminated. The oldest known incidence of the “Cordilleran” NNW-SSE tectonic trend is the ~1,760-Ma thermally induced Kimiwan geochemical anomaly in the cratonic basement of the central and western Alberta Platform, but thereafter orogenic activity shifted to the west.
Two-sided old volcano-sedimentary and sedimentary basins - Middle Proterozoic Belt-Purcell, Late Proterozoic Windermere and late Paleozoic Prophet-Ishbel - in the eastern Cordillera are known from sedimentological studies to have received sediments from land sources on the east and west. Internal variations in these basins are related to numerous faults and blocks with various orientations.
The Belt-Purcell Basin, though very deep, was evidently broad, intracratonic and non-orogenic, and the ancient cratonic area to the west of it is conventionally called the Western craton. The NNW-SSE Cordilleran tectonic trend was firmly established with the onset of Windermere rifting at ~780 Ma. The Prophet-Ishbel trough was probably a foredeep to the Antler orogen, whose continuation into Canada lay in the Cordilleran regions to the west. The NNW-SSE and transverse Phanerozoic tectonic zonation in the Canadian Cordillera was inherited from Precambrian time.
In the cratonic Alberta Basin, many Paleozoic platformal sedimentary units are laterally monotonous and fail to exhibit a wedge-like thickening to the west. Occasional westward continuation of cratonic platformal depositional settings far into the Cordilleran interior is indicated by the presence even on the west side of the Omineca Belt of Paleozoic carbonate-platform remnants similar to the coeval carbonate platforms in the cratonic Alberta Basin.
Contrary to a common assumption, at no time did the eastern Canadian Cordillera contain a one-sided, passive Atlantic-type continental margin.
Another common error in the studies of the cratonic Alberta Basin and the eastern Cordillera is the Bond-Kominz theoretical model of basin subsidence. Wrongly, that model assumed the former existence in the eastern Cordillera of an Atlantic-type continental margin, and it counter-factually supposes that the formative tectonic evolution in that region commenced only at the onset of the Phanerozoic. Neither assumption is correct, and the early Cordilleran Windermere tectonism is known from field studies to date back to at least ~780 Ma. Some prior, if poorly understood, orogenesis in that region seems to have taken place even earlier, in the interval between Belt-Purcell and Windermere times, based on metamorphic and deformational contrasts between the Belt-Purcell and Windermere rocks.
Equally wrong is the idea to divide the Alberta Basin's tectonic evolution into two main stages - the passive-margin stage before the mid-Jurassic, and the foreland stage after.
No Paleozoic passive continental margin existed in the eastern Cordillera. On the other hand, in relation to the late Paleozoic Cordilleran Antler and Teslin orogens, the cratonic Alberta Basin was in a foreland position even then, with the Prophet-Ishbel Trough (now largely thrust-faulted in the Laramide Rocky Mountain Belt) serving as a foredeep. The change in the mid-Jurassic was that western-derived, Cordilleran detrital clasts first appeared in the Alberta Basin (although some provenance studies suggest that Cordilleran Antler highlands were shedding sediments into the basin in the Late Devonian). For all its sedimentological and paleogeographic significance, this Jurassic event reflected nothing more than a rise of topographic highlands or mountains in the eastern Cordillera. No significant change in the cratonic depocenter-arch configuration is noted in Alberta in the mid-Jurassic. The Alberta Basin was tectonically the same - cratonic and platformal - before and after.
The ancient craton(s) of the North American continent previously continued far into the regions that would be subsequently remobilized to become the Cordillera. Geochemical evidence of reworked, ex-cratonic ancient basement rocks is well known from the metamorphic complexes in the southern Omineca Belt. Highly metamorphosed former supracrustal rocks are known in these complexes as well. To achieve their high metamorphic grades, in the Mesozoic and early Cenozoic these rocks were first lowered to great crustal depths of 20-30 km, and then rapidly returned to the surface. Mapped tectonic manifestations (magmatic, metamorphic, structural and sedimentary) indicate that intense Nevadan and Columbian orogenic episodes occurred in that region in the Middle Jurassic and mid-Cretaceous, each ending with decompression and crustal extension.
The Late Cretaceous-Early Tertiary Laramide orogenic cycle, with its own well-recognized extensional pulse in the end, was only one in this long series. This repetitive, multi-cycle orogenic tectonic history contradicts the commonly assumed scenario with a passive continental margin in the eastern Cordillera before the mid-Mesozoic, compression and exotic-terrane accretion and stacking from then till the Early Tertiary, and extension thereafter.
The Laramide Rocky Mountain fold-and-thrust belt is known from outcrop, drillhole and seismic data to be a thin-skinned, rootless thrust stack that does not involve the cratonic basement, which in that region is not tectonically reworked. Cordilleran tectonic reworking of the ancient crystalline-crust basement begins near the Rocky Mountain-Omineca belt boundary, and that line should be considered the modern edge of the North American craton.
In contrast to the recurrent, strong crustal tectonic reworking in the Omineca and Coast Belt orogenic zones, metamorphism and deformation were comparatively slight in the more-rigid crustal blocks of the Intermontane Belt and Yukon-Tanana massifs: their volcano-sedimentary cover is preserved largely intact, its upper parts are metamorphosed only weakly or not at all, and block faulting is common. The magmatism in that region was largely teleorogenic, induced by orogenesis in adjacent regions (mostly, Coast Belt). Preserved blocks of rigid, semi-reworked ex-cratonic Precambrian crust probably lie beneath the exposed Late Proterozoic and Phanerozoic volcano-sedimentary cover (the oldest known cover rocks are Devonian in the Intermontane Belt and Late Proterozoic in the Yukon-Tanana massif). Presence of an older continental basement is suggested by radiometric inheritance (Early Proterozoic in the Yukon-Tanana massif), seismic-velocity structure of the crust, and long-time rigidity of these crustal blocks that saved them from a more profound orogenic reworking.
The Skeena and Stikine arches in the Intermontane Belt follow the ancient NE-SW cratonic tectonic trends, regardless of assumed Cordilleran terranes. Ex-cratonic crystalline basement, tectonically reworked to various degrees, seems to continue at least as far west as the Intermontane-Coast belt boundary, and possibly even into the Insular Belt whose structural patterns are similar.
Local rifts, Mediterranean- or Red-Sea-type deep marine basins and even ephemeral minor subduction zones might nonetheless have existed in the Canadian Cordillera at various times and in various localities; the inversion and closure of these marine basins took place largely in late Paleozoic (Antler-Teslin) time. Such pre-Mesozoic events, during which the main active crustal weakness zones were the ones oriented NNW-SSE, may account for the partition of the Intermontane Belt into the Stikine and Quesnel crustal blocks. This Paleozoic division was quite different than the subsequent, Mesozoic partition into blocks defined by the reactivated but ancient, transcurrent Stikine and Skeena arches.
Because crustal blocks with a shared ancient crustal ancestry in the Cordilleran interior developed throughout the Phanerozoic side by side, roughly in situ, the postulated multiple big former oceans (Cache Creek, Teslin, Anvil) are improbable. The Cache Creek rock complex ("terrane"), moreover, is known to contain Permian felsic igneous rocks, and its diverse rock assemblage reflects a turbulent and variable - rather than oceanically quiescent and uniform - tectonic history. The Omineca, Intermontane, Coast and Insular belts developed essentially in situ, but the Intermontane and (to a lesser degree) Insular belts have retained more of their ancient ex-cratonic crustal inheritance than the neighboring Omineca and Coast Belt orogenic zones.
Outward-verging Mesozoic and Cenozoic fold-and-thrust zones in the Cordilleran interior are known to bilaterally flank the Coast Belt and Omineca orogens. Like the big Rocky Mountain fold-and-thrust belt on the east side of the Omineca orogen, these zones are probably rootless. These shallow deformation zones on the orogens’ flanks partly obscure the deep, steep crustal boundaries of the Coast and Omineca orogenic belts. The Rocky Mountain Belt was able to grow bigger than its counterparts in the Cordilleran interior partly because the thick, completely unmetamorphosed, stratified sedimentary-cover succession of the cratonic Alberta Basin offered a layered mechanical medium easily delaminated into thrust sheets.
Wholly unconvincing is the supposed seismic evidence that the entire Cordilleran crust is a stack of exotic-terrane thrust sheets. Lithoprobe's current interpretation holds the Cordilleran crust to be a stack of thrust-sheet exotic-terrane slivers, overlying a preserved thin ex-cratonic sliver in the lower crust. Yet, strong disagreements exist between the current seismic and electrical-resistivity interpretations about the depth where the presumed ex-cratonic bottom sliver ends and the overlying terrane thrust slices begin. These disagreements illustrate the inherent uncertainties in geophysical interpretation. They are also arbitrary and sterile, because they fail to consider numerous other possible interpretations.
Geophysical anomalies carry useful but indirect information about the spatial distribution of specific physical properties of rocks. Yet, they say nothing about the imaged discontinuities’ geologic nature, genesis or age. High-angle crustal discontinuities are usually missed in seismic reflection images altogether, and the geologic origin of low-angle reflections is unknown. Correlation of seismic events is complicated by these events’ unknown nature, common lack of continuity, reflection-character variations and gaps in the data. In a strongly deformed and magmatized region like the Cordillera, many off-line arrivals and other hard-to-identify forms of coherent noise contaminate the seismic data at short and long traveltimes. The technical need for road access during data acquisition in the mountains required the Lithoprobe seismic reflection profiles to be shot largely along passable valleys, which tend to follow steep NNW-SSE-trending and transcurrent crustal faults; as a result, some of the seismic lines were shot not across but along the strike of large-scale crustal structures.
Geological and geophysical evidence shows that, contrary to the conventional model, no ongoing subduction is currently taking place off Vancouver Island, and the modern Cascadia subduction zone does not reach north into Canada (see next section). Postulations of trans-Cordilleran subhorizontal crustal detachments similarly rely on assumption-based correlations of selected, disconnected low-angle seismic events and their assignment to faults that at the surface are known to be variously low-angle or steep. Principal significance in these interpretations is assigned, arbitrarily, only to those reflections that seem to fit the assumed structural geometry, while the numerous other reflections are disregarded as unimportant. The Slocan Lake and Monashee faults, for example, are correlatable with any confidence only with reflections that dissipate in the upper and middle crust. The much-criticized use of discontinuous “floating” events to justify these faults’ presumed trans-crustal continuity is unfounded, and it contradicts the results of refraction seismic surveys. Instead, the biggest, steep fault system in the southern Omineca Belt region seems to be the one along the Kootenay Lake, which forms the western boundary of the Kootenay Arc and is associated with big seismic-velocity changes even in the lower crust.
Today's lower continental crust, especially in mobilized orogenic regions, exists in ductile conditions at high grades of metamorphism. Such a rock mass, which can flow easily, contains many diverse sources of seismic reflectivity. Indeed, the ductile lower crust is known to be reflective worldwide, for reasons that have nothing to do with crustal-scale thrusting.
Notoriously unpredictable are fault geometries in the middle and lower crust, below the brittle-ductile transition. Many deep faults assume unexpected geometries, or dissipate completely. Older deformation patterns are obliterated by subsequent metamorphism, melting and re-deformation. Preservation of ancient structures in the Cordilleran crust is ruled out by the geological evidence for large-scale vertical crustal movements and extensive reworking in Late Proterozoic, Paleozoic, Mesozoic and Cenozoic time. To make assumption-based projections of fault geometries deep in the crust, or to assume that ancient deep crustal features are simply preserved, is groundless.
Paleomagnetically derived speculations about large lateral translations of assumed Cordilleran terranes err in confusing inferences and assumptions with factual evidence. The factual data can be, for example, the results of laboratory analysis of magnetic properties of rocks. In contrast, an interpretation of these factual results in terms of the rocks' paleolatitude is just an inference. Because we understand so little of rock magnetism (sources of the oceanic magnetic stripes, for instance, are still unclear), these paleolatitude interpretations are commonly in error, as is starkly brought to light every time they collide with direct evidence from regional field mapping.
The profound, laterally variable, multi-cycle tectonic reworking of the entire crust and perhaps deeper lithosphere in the Omineca orogenic belt included Mesozoic and Cenozoic differential subsidence and uplift of big crustal zones by tens of kilometers. Therefore, the postulated preservation and direct continuity from the craton of Proterozoic features in the middle and lower crust across the eastern Cordillera are implausible. In particular, there is no geological or geophysical evidence for the assumed creation and preservation within the eastern Cordilleran crust since the Proterozoic of an ancient passive-margin ramp. Due to strong, extensive and repeated Late Proterozoic and Phanerozoic whole-crust tectonic reworking of huge tectonic zones in the Cordillera, direct and unbroken continuity from the craton of an unaltered ancient basement under the Cordilleran interior is impossible.
Neither is the Cordilleran Moho a Proterozoic relic: indeed, COCORP seismic interpretations just south of the Canada-U.S. border note that the Cordilleran Moho truncates the seismically-inferred orogenic crustal structural patterns, and regard the Moho as probably a product of Cenozoic regeneration. The presumed trans-Cordilleran low-angle crustal detachments are likewise not supported by compelling correlations of unquestionably interpreted primary seismic reflections, and they contradict the geological evidence for large-scale vertical crustal movements in Late Proterozoic, Paleozoic, Mesozoic and Cenozoic time.
The Proterozoic Laurentian and possibly Western cratons in pre-Cordilleran time continued far into the modern-day Cordilleran interior. Today, their semi-reworked remnants are found in the comparatively stable Intermontane and Yukon-Tanana crustal massifs, which are surrounded by orogenic zones where multi-cycle crustal tectonic reworking was much greater.
The main differences between tectonic zones in the Cordilleran interior lie not in their assumed exotic-terrane composition but in the degree of in situ multi-aspect orogenic reworking of indigenous, ex-cratonic North American lithosphere and crust. It is the real ex-cratonic and younger orogenic crustal structures, not the assumed terrane boundaries, that control the distribution of mineral deposits.
EARTHQUAKE HAZARD ON THE WEST COAST OF NORTH AMERICA
See our CSEG Recorder article for more details.
Based on a combined analysis of seismic, potential-field and geological information offshore and onshore, an internally consistent model of crustal structure and ongoing plate interactions has been produced for the west coast region of North America from Alaska to Oregon. It is found that the Cascadia subduction zone exists only in the U.S. and does not continue north into Canada, where no ongoing subduction is taking place. Instead, the continental margin in that region is marked by a large Fairweather-Queen Charlotte-Wallowa fault system that runs from Alaska to Idaho, where it begins and ends inside the North American continent.
The conventional active-subduction tectonic model for the western continental-margin region of Canada, which assumes the oceanic plates to be rigid and the subduction to be ongoing, has been found to be inconsistent with a broad range of geological and geophysical factual evidence. Consequently, it is concluded that the usual earthquake-risk assessments for the Seattle-Vancouver area, which are based on this model, are considerably exaggerated. Although many dangerous earthquakes do occur in that area, along numerous faults at various crustal and lithospheric levels, a commonly forecast giant mega-thrust earthquake is impossible due to the absence of an active subduction-related mega-thrust.
The assumption that oceanic lithospheric plates offshore western North America are rigid fails in the face of all the factual evidence. The entire Cascadia subduction zone is unusual in the Circum-Pacific region, in that it lacks some of the main geological and geophysical attributes from which subduction zones are normally identified. There is no deep-water bathymetric trench. No thrust earthquakes are taking place: analysis of fault-plane solutions and young geologic structures suggests strike-slip and normal faulting, apparently with N-S compression in the continental crust and extension at deeper lithospheric levels. Steep crustal-scale faults of Mesozoic and Cenozoic ages are seen to continue from the continental interior far outboard into the submerged continental-margin zone offshore western Canada.
The diffuse plate boundary off western Canada seems to be marked by a zone of interlocked continental, transitional and oceanic crustal blocks tens of kilometers wide, controlled by strands of the continental Fairweather-Queen Charlotte-Wallowa fault system. This conclusion is based on combining seismic and potential-field data with geological data from field mapping and drilling.
Both the southern (Gorda, off northern California) and northern (Vancouver Island, off British Columbia) parts of the oceanic Juan de Fuca plate have contorted magnetic stripes and diffuse seismicity. Seismic data show the northern Juan de Fuca plate's crust is strongly faulted and has variable thickness.
But, whereas the Gorda segment is commonly recognized to be squishing and probably not subducting, oceanic-plate rigidity and normal subduction continue to be conventionally assumed for the Vancouver Island segment, where the evident oceanic-crust disruption is by far the greater.
An assumed plate-interaction model with dextral movements off Queen Charlotte Islands, triple junction off Queen Charlotte Sound, and subduction off Vancouver Island has for two decades guided geophysical data interpretations and seismic-hazard assessments. But the data suggest an alternative.
The WNW-trending Early Tertiary Olympic-Wallowa crustal weakness zone is known from field mapping to begin in Idaho and run across northeastern Oregon and the entire Washington state. The deep Juan de Fuca graben and Juan de Fuca strait lie within it. Its strands and other steep faults are traced in potential-field maps to continue on the continental shelf off Vancouver Island, where the sharply contrasting stratigraphy in the deep Tofino Basin wells suggests dissimilar vertical movements of fault-bounded crustal blocks throughout the Tertiary. Some of these deep, steep faults on the shelf controlled volcanic eruptions, as evidenced by known elongated Tertiary volcanic-rock bodies along these faults.
Unlike offshore Washington, no accretionary melange has been drilled off Vancouver Island. Poorly imaged quasi-compressional structures in seismic profiles on the continental slope off Vancouver Island are probably due to sediment slumping, and many well-resolved faults are steep (quite in contrast to the east-dipping thrusts with intra-sedimentary detachments clearly imaged and drilled on the continental slope off Oregon).
Local alignment at the foot of the Vancouver Island continental slope of highly distorted magnetic stripes continuing from oceanic regions and linear gravity anomalies that continue from known faults in land areas suggests interlocking of broken-up oceanic and continental blocks; magnetic stripes in these blocks are related to secondary structural deformation and have little value for plate-motion reconstructions.
The Cascadia zone's subduction is often recognized to be decaying off Oregon and Washington state, and from our analysis it no longer seems to be occurring in Canada.
No significant young compressional structures are found in the rock record on Vancouver Island: big Tertiary faults, some inherited from the Mesozoic, are straight and steep; some of them disrupt seismic-reflection patterns at depth. There is no bathymetric trench, and no thrust earthquakes are known onshore or offshore. Along the western continental margin in the U.S. and Canada onshore, the measured modern vertical movements of different crustal blocks differ greatly and fail to fit any simple 2-D flexural model as expected at subduction zones.
Thick crust (10 to >20 km) and the lack of magnetic stripes under the 8-km-thick Winona sedimentary basin on the lower continental slope off northern Vancouver Island suggest that the underlying crustal blocks are continental. A huge, steep, listric, NNW-SSE-trending, west-dipping normal fault, seen very clearly in seismic sections, separates these blocks from the continental shelf.
Several tens of kilometers outboard to the west, the outer edge of the Winona Basin is marked by the subparallel Revere-Dellwood fault, which truncates the magnetic stripes abruptly and west of which the crust is by all parameters oceanic. Seismic velocities of >5 km/s at the lower stratified levels of the basin suggest the deepest sedimentary rocks in it are old, perhaps similar to the Paleozoic and Mesozoic volcanic and sedimentary supracrustal rocks on Vancouver Island. Anticlines in the shallower, unconsolidated Winona Basin sediments, seen in seismic profiles, are similar to those typically caused by mud diapirism.
Likewise, no magnetic stripes are found in a zone several tens of kilometers wide at the base of the continental slope off Queen Charlotte Sound. Ocean-floor volcanic mounds in that magnetically blank zone are small and scattered, their geochemistry is inconsistent with spreading, and gravity anomalies in the free-air and isostatic maps are minor. These observations rule out the commonly assumed existence in that area of sea-floor spreading and a plate triple junction.
The broad NW-SE-trending fault system in which the Winona Basin lies runs past Queen Charlotte Sound and Islands, where some of its strands bound the Queen Charlotte bathymetric terrace formed by a foundered continental-crust block (with a Moho up to 20 km deep). Off southeastern Alaska, this fault system merges with the broad Fairweather fault zone which forms the plate boundary offshore but begins in the north inside the Alaskan continental interior.
The Fairweather-Queen Charlotte fault zone meets the Olympic-Wallowa zone of crustal weakness on the continental shelf and slope off southern Vancouver Island.
No active subduction mega-thrust being present beneath Vancouver, the earthquake hazard in that region is lower than conventionally estimated.
THE FAILURE TO TEACH
"Ignorance is strength." -- George Orwell
(An earlier version of this column by Henry Lyatsky was published by the Geological Association of Canada in the Spring 2002 issue of its newsmagazine Geolog)
Dead silence was my answer a few years ago when, giving a guest lecture to a graduating geophysics class at a major Canadian university, I asked these almost-graduates to explain the term anomaly. The silence grew denser, and palpably more perplexed, when I asked what sort of material an anomaly source is made of.
This experience has been repeated in other schools, and with many other senior classes. I have since found it useful to make up an entire one-hour lecture on such fundamentals for graduates - a lecture the host faculty sometimes request to be given ahead of a usual talk on real-life exploration examples.
The dual function of academic institutions has been part of the university tradition since Socrates: (1) to advance knowledge, and (2) to educate the young. Our modern universities’ success in the first of these endeavors is in the eye of the beholder. In the second one, the failure could not be more naked.
Poor teaching is engineered into the academic system itself. University departments are financed based on the number of students in their programs, while the faculty receive few career prizes or penalties for how these students are taught. As a result, departments seek to attract as many students as they can, often by overselling the future career prospects, and then proceed to ignore the enrolled students as much as possible. The biggest failing occurs in the main educational focus that separates a university from a vocational school: the teaching of analytical ability.
Instructor indifference, arrogance, incapacity and a lack of accountability are among graduates’ biggest complaints. Many professors lack the inclination, or the ability, to teach the analytical use of observed facts to arrive at a testable conclusion. In lectures, labs and assignments, analysis is often replaced with minor technical tasks, rote memorization, or conceptual dogmatism that insists on ignorance.
Students complain of their unaccountable instructors’ perpetually incomprehensible accents or untreated personality disorders (for the record, I have an accent, so no lapse of political correctness here). Stories abound of garbled or vacuous classroom performance, gratuitously complicated or risibly trivial homework, exams unrelated to course material, and uninformed career advice. With the standards abysmally low across the board, instructor failure is seldom penalized or even officially noted. Formal complaints from students are easily avoided by bribing them with undeservedly inflated course grades.
Monkey-see-monkey-do, students are often taught a computer application - a stereonet or deconvolution program, for instance - without being told, from first principles, what stereonets or signal deconvolution actually do. Lacking basic understanding, these graduates later find themselves unable to upgrade as the technology changes.
A deceptive, common teaching-success measure is the proportion of new graduates in jobs. This short-term measure, which in geology and geophysics rises and falls with the commodity prices, does not consider the job quality - and many new "professional" employees are little more than glorified technicians. These young people are easily let go in the frequent industry downturns, and their lack of basic knowledge and adaptability leaves them obsolete after even a short period out of work. A new crop of graduates is by then available to take their place, with more up-to-date technical skills. Much more revealing is to see how many alumni are still in the profession after several business cycles, and what career levels they achieve.
Equally unrepresentative is to grandly showcase the Spectacularly Successful Alumnus, the CEO (until the next corporate takeover, at any rate), in pursuit of reflected glory. The circumstances of one person uniquely gifted or lucky may say little about the lives of the many.
The students, to put it bluntly, are being robbed on a colossal scale. Giving them a poor education violates the medics’ Hippocratic oath: first, do no harm. The young graduates’ unmet, unrealistic expectations down the road lead to broken careers and broken lives. Also robbed are their employers, families, and (remember them?) the taxpayers. What is certified as university education often amounts to little more than sketchy vocational training, without a central theme, thrown together ad hoc, and dismally delivered.
If the problem lies with the instructors, the solution lies with them, too. As long as teaching is seen by academics as an unavoidable nuisance, one to be minimized where possible as it interferes with publishing, the disservice will continue. Because dedication is impossible to legislate, accountability-based and market-based policy solutions could be brought in from the ongoing debate about the reforms of North American secondary schools.
1. Demonstrated ability in quality teaching must be made a top factor in academic employment and promotion.
2. Demotion and dismissal must be the price to professors for poor teaching.
3. Faculty tenure, which often shelters failure, must be abolished.
4. Standardized testing of students may be dull, but it has a passable claim to objectivity.
5. Testing instructors on their grasp of the subjects they teach could weed out the unqualified.
6. Above all, competitive consumer choice must allow students, armed with tuition vouchers, to easily bolt into a network of leanly-organized private universities.
Talking more about the plain teacher ethic might also help. Genuine teacher commitment is risking all to run a banned, underground school under the Taliban. Anyone who measures up, please rise.
THE MEANING OF ANOMALY
(This article by Henry Lyatsky was published in the June 2004 issue of the CSEG magazine Recorder.)
It began by accident, when I casually asked a class of fourth-year geophysics students to define the term anomaly. The disconcerting, blank silence that ensued was repeated by many subsequent senior classes in the following years, and at various schools.
Meanwhile, a client wanted to know about EM anomalies on his mineral property, another asked if anomalies in a derivative magnetic map were real or processing artifacts, a oilman wondered if gravity anomalies might help to delineate a frontier basin, somebody else was giving a talk about separating intrasedimentary from intrabasement magnetic anomalies, a software vendor offered anomaly enhancement, and a voice on the phone enthused that seeing good anomalies in one 3-D seismic survey surely made up for finding none in the more expensive other.
Some things seem so blindingly self-evident that no one bothers to examine them. The sun rises in the east and sets in the west. The Earth is round not flat (we say today), or flat not round (we said a few centuries ago). Oil and mineral deposits are found in the rock mass, and we use geophysics to locate them. And a geophysical anomaly is... what exactly? We say “anomaly” all the time. What could be more obvious?
In an appalling, guilty, dreadful chill of sudden horror at my own dismal ignorance, I got busy looking it up. But because everyone is assumed to know, it seemed, many geophysics texts and reference books don’t even bother to offer a definition. Our exploration bible, the SEG dictionary (Sheriff, 1991), spake thus.
anomaly. 1. A deviation from uniformity in physical properties; a perturbation from a normal, uniform, or predictable field. 2. Observed minus theoretical value. 3. A portion of a geophysical survey, such as magnetic or gravitational, which is different in appearance from the survey in general. 4. A gravity measurement which differs from the value predicted by some model, for example, a Bouguer or free-air anomaly (q.v.). 5. In seismic usage, generally synonymous with structure. Occasionally used for unexplained seismic events. 6. Especially, a deviation which is of exploration interest; a feature which may be associated with petroleum accumulation or mineral deposit. 7. An induced-polarization anomaly is usually positive and greater than background (or the normal effect) to be economically interesting. In the frequency domain an anomalous region has a resistivity which decreases with frequency. An interesting resistivity anomaly is generally smaller than background.
Well, fine. These specific points are useful, as far as they go. But what do they add up to? Item 2 only seems to mathematize item 4, but 4 is unaccountably restricted only to gravity surveys. And is an anomaly source generally a structure (item 5)? Is a geophysical anomaly the same as the geologic feature which is its source (items 1 and 5), or are these phenomena of different categories? Are only those anomalies deemed of exploration interest worthy of the title (item 6)? Why different anomaly definitions for different survey types? Some of these items seem to record colloquialisms (5), others are descriptive not definitional (7). When all is said and done, what is an anomaly?
To be most useful, an ideal definition would (a) be general to all exploration geophysics regardless of survey type and target, and (b) provide an interpretive link between an anomaly and its rock-made source. Without claiming the final word, allow me humbly to offer the following (cf. Lyatsky and Pana, 2003). A geophysical anomaly is the difference between the observed (measured) geophysical-field or -survey value and the value that would be observed at the same location if the earth were more uniform than it is.
This definition incorporates Sheriff’s (1991) items 2 and 4, but is broad enough to be relevant for many geophysical fields. It hints at interpretational utility, linking anomalies to detectable non-uniformities in the earth.
But what is the survey value that would be measured “if the earth were more uniform than it is”? And how much more uniform? Exploration geophysics commonly aims to find local rock-property variations. The International Geomagnetic Reference Field is a conventional global uniform-earth magnetic model, so we can reasonably pretend the anomalies left after the IGRF data reduction are attributable to local (map-scale) rock-magnetization changes. Free-air, Bouguer and isostatic reductions offer idealized uniform-earth models for gravity data, accounting imperfectly but progressively well for the earth’s overall character and leaving post-reduction anomalies more purely related to map-scale rock-density variations. In seismic data, a perfectly uniform earth lacking reflectors, refractors or diffractors would bounce back no signal at all: no wiggles in the trace, no colors to indicate amplitude.
Can an anomaly be related directly to a particular type of geologic feature? Without previously known geological constraints, no. The first reason is the non-uniqueness that arises from physics: an infinite number of different source geometries can produce exactly the same anomaly. The second reason lies in the phrase rock-property variation. An anomaly-causing change in the rocks’ physical properties may or may not be related to any significant change in lithology, and vice versa.
A geophysical anomaly is detected when a survey encounters some geometric perturbation in the distribution of a particular physical property in the rocks. Not just any perturbation, of course, and not with any geometry. Whereas reflection seismic data generally reveal horizontal or low-angle discontinuities, gravity and magnetic data help with high-angle ones. Gravity anomalies arise due to lateral perturbations in rock density, magnetic ones are caused by lateral changes in rock magnetization, and seismic anomalies indicate variations in acoustic impedance. Intraformational variations in the rocks’ magnetite content, even without changes in bulk lithology, may cause big magnetic anomalies but nothing much in gravity maps or seismic sections. Perfectly flat-lying strata would produce vivid railroad-track seismic reflections, but a featureless gravity map. And so on.
A crucial intermediate logical step must thus be taken when linking geophysical anomalies to geology. We can’t simply go from lithology to anomaly or from anomaly to lithology. First, we must consider what perturbations in the physical properties of rocks (velocity, density, magnetization, electrical resistivity, etc.) a particular geometry of lithology changes would be accompanied by, and then design a geophysical survey to delineate the anomalies these rock-property perturbation are expected to cause. The same consideration applies when interpreting anomalies in terms of their geologic sources. Geophysical anomalies indicate rock-property variations, not simply lithology changes.
And the moral of the story? Things are both less and more complicated than they seem, but our logic must always be crystal clear. And perhaps it sometimes pays to look into the seemingly obvious. Therein may hide the most subversive pitfall of them all: something fundamental we don’t quite grasp, which gives us a false sense of security by masquerading as reassuring trivia.
Lyatsky, H.V. and Pana, D.I., 2003. Catalogue of Selected Regional Gravity and Magnetic Maps of Northern Alberta; EUB/Alberta Geological Survey, Special Publication 56, 40 p.
Sheriff, R.E., 1991. Encyclopedic Dictionary of Exploration Geophysics (third edition); Society of Exploration Geophysicists, 384 p.
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