by Applied Geophysics' Chief Geophysicist, S. Parker Gay, Jr.*


2014, "Some Observations on the Amarillo/Wichita Mountains Thrust-Fold Belt and its Extensions SE into East Texas and NW into New Mexico”
Shale Shaker, The Journal of the Oklahoma City Geological Society, Vol. 65, no. 5, p. 338-366.


2009, Reactivation Tectonics: The Evidence & The Consequences, American Stereo Map Co., Technical Publication No. 3, 263 p.

This is a summary that ties together all of Parker Gay’s discoveries and advances in geology related to “Reactivation Tectonics.” Some geologists, who have not studied Gay’s material or don’t have the background to understand it, dispute his conclusions, but there are no flaws in his science. It will sooner or later become mainstream geology.
Available from Applied Geophysics, Inc. for US $50.00.


2003, The “Great Dike of Wyoming” and Satellite Bodies: A Comparison to the Great Dyke of Rhodesia/Zimbabwe: Wyoming Geological Association Guidebook for 2002/2003, pp 101-111.

Applied Geophysics, Inc. flew the aeromagnetic survey of the Powder River Basin in 1985. As soon as it was processed, several long, spectacular-appearing magnetic anomalies became evident in the northern part of the Basin. After an on-and-off study that took place over several years, the author concluded that these anomalies are caused by ultra-mafic bodies similar to the Stillwater Complex in Montana and the Great Dyke of Rhodesia in Africa.



2004, Glacial Till: A Troublesome Source of Near-Surface Magnetic Anomalies: The Leading Edge, June 2004, Vol. 23, No. 6, The Meter Reader:

In the 1980's, a popular fad in magnetics was to ascribe magnetic anomalies to “diagenetic magnetite,” a mineral supposedly formed over oil fields by the interaction of iron minerals existing at shallow depths in the ground with gas leaking from the reservoir. Some of the areas so interpreted were located in places covered with glacial till, which the author, from previous work, knew was magnetic and could cause the “diagenetic magnetite” anomalies. Since the magnetic nature of glacial till did not seem to be well known among the potential field geophysicists of this era, the author decided to gather as many examples as possible of documented magnetic anomalies over glacial till and place them in the literature. He used several examples from his own files, but most were obtained by calling and writing to colleagues he knew from his 25 years in mining exploration. A total of 29 examples were documented. From this, he concluded that regional glacial till in North America is always magnetic (since it originated - in the beginning - on the Canadian shield) and that there is thus no “non-magnetic” glacial till, as one prominent petroleum industry potential field geophysicist suggested.



2003, The Nemaha Trend - A System of Compressional Thrust-Fold, Strike-Slip Structural Features in Kansas & Oklahoma, parts 1 & 2: Shale Shaker, The Journal of the Oklahoma City Geological Society, Vol. 54, no. 1, p. 9-17, & no. 2, p. 39-49.

In the 1980's and 1990's the author spent a considerable amount of time talking to Midcontinent petroleum company geologists about the Nemaha system, and many of them showed him seismic and geologic cross sections displaying reverse faults and repeated section. The general consensus was that the system was, without a doubt, compressional. Yet, at the same time, articles and talks by some in the academic and geologic survey community indicated a possible extensional origin. There seemed to be a lack of communication between the two groups. To correct this wide gap in knowledge, the author gathered together 29 examples of reverse faults taken from articles, theses, and private files and documented them in this paper. These show unequivocally that the system is mainly compressional, although it has had subsequent (and perhaps partially contemporaneous) strike-slip movement.



1999, An Explanation for "4-way Closure" of Thrust-fold Structures in the Rocky Mountains, and Implications for Similar Structures Elsewhere: The Mountain Geologist, Vol. 36, No 4. (Oct. 1999), p. 235-244, RMAG

This paper shows how “end-closure” of anticlines results from the small component of maximum compressive stress that is directed along the long axis of the anticline perpendicular to the main stress that raised the anticline. It then shows how the longitudinal stress results from compression across a basement fault not at right angles to the direction of maximum compression. This is a quite straightforward physical solution to the geometry we have always observed. However, it is a radical departure from currently accepted dogma, and thus revises a major aspect of structural geology. We do not expect immediate acceptance of this idea, but eventual acceptance is certain.



1999, Maps: It's the Basement's Fault: AAPG Explorer, v. 20, no. 12, p. 28-31.

This two-part series in the AAPG Explorer briefly summarizes the conclusions published in references 18 and 19 above. It also makes the strong point that the basement fault block pattern in covered areas is only mappable with magnetic techniques and not by seismic or gravity methods.


1999, Basement Mapping Highly Crucial: AAPG Explorer, v. 20, no. 11, p. 32-33.


1999, Using Magnetics in Petroleum Exploration, with E.A. Beaumont as senior author, in N.H. Foster and E.A. Beaumont, editors, Treatise of Petroleum Geology Handbook, Exploring for Oil & Gas Traps: AAPG, Tulsa, Oklahoma.

This is a brief summary in Ted Beaumont's words of the conclusions of #19 (above).



1995, The Basement Fault Block Pattern: Its Importance in Petroleum Exploration, and Its Delineation with Residual Aeromagnetic Techniques, in R.W. Ojakangas, editor, Proceedings of the Tenth International Basement Tectonics Conference: Kluwer Academic Publishers, Dordrecht, The Netherlands.

This is AGI's position paper on the use of magnetics for oil and gas exploration. It expands on the Kansas paper (18) and shows that most structure in the sedimentary section and much of the stratigraphy is controlled by basement throughout the U.S. and by inference, worldwide. Gay takes to task those magnetic interpretations that assume a uniform composition of basement and points out that, geologically, this is not known to occur.



1995, Basement Control of Selected Oil and Gas Fields in Kansas as Determined by Detailed Residual Aeromagnetic Data, in Kansas Geophysical Atlas: Kansas Geological Survey, Lawrence, Kansas.

Here it is shown that in Kansas many oil and gas field structures result from movement of basement faults or compaction over basement topography and that some stratigraphic reservoirs also result from basement fault movement.


 1992, Epigenetic Versus Syngenetic Magnetite as a Cause of Magnetic Anomalies: Geophysics, vol. 57, no. 1.

This is a continuation of the study cited in 16.


1991, Syngenetic Magnetic Anomaly Sources: Three Examples: Geophysics, vol. 56, no. 7. (with Bronson Hawley as second author).

This was Parker Gay's response to an interpretational fad of the day that attributed most "high frequency" (i.e. narrow) aeromagnetic anomalies to "diagenetic" magnetite. It was shown that narrow magnetic anomalies are instead usually caused by a variety of syngenetic geologic sources, culture, post-depositional igneous activity, coal burns, etc.



 1989, Gravitational Compaction, A Neglected Mechanism in Structural and Stratigraphic Studies: New Evidence from the Midcontinent, USA, AAPG Bulletin, vol. 73, no. 5.

This is a condensed version of #10 (above) in a leading publication, but arrives at and proves, the additional conclusion that bed thinning observed over compactional anticlines is a natural consequence of the compaction process itself.



1987, Mafic Dyke Swarms Associated with Mesozoic Rifting in Eastern Paraguay, South America: M.D. Druecker, and S.P. Gay, Jr., in Mafic dyke swarms, H.C. Halls, and W.F. Fahrig, editors, Geological Association of Canada Special Paper 34, p. 187-193.

Careful work on magnetic profiles in a low level magnetic survey in Paraguay allowed the mapping of mafic dike swarms and determining whether they were injected during normal or reverse magnetic epochs.


1986, Relative Timing of Tectonic Events in Newly Recognized Precambrian Terranes in South Central Kansas, as Determined by Residual Aeromagnetic Data, in J. Aldrich, editor, Proceedings of the Sixth International Basement Tectonics Conference, Santa Fe, N.M., 1985: International Basement Tectonics Association, Salt Lake City.

This is the first attempt ever, and the only one so far (2007), to methodically define the Archean-Proterozoic structural history of an area by noting the age associations of magnetic anomalies.


1986, The Effects of Cathodically Protected Pipelines on Aeromagnetic Surveys: Geophysics, vol. 51, no. 8, p. 1671-1684.

This is the first study ever, and the only one so far (2007), that mathematically defines the magnetic anomalies due to DC electric currents flowing in pipelines - anomalies that are observed on nearly every magnetic map of petroleum basins.


1986, "Graniteville-Type" Proterozoic Igneous Intrusions Mapped in Southeast Kansas, in Steeples, "Symposium on Geophysics in Kansas - a 25-year Update": Kansas Geological Survey, Lawrence, Kansas.

This short study showed that certain oval-shaped magnetic anomalies in south-central Kansas were similar to those mapped earlier in southeast Missouri (6) and arose from the same group of Proterozoic intrusions. It also showed that the area within the intrusions where the rock is of fairly uniform composition, magnetic highs can be reliably ascribed to basement highs, unlike the remaining 99% of areas underlain by crystalline metamorphic basement.


1985, Gravitational Compaction, A Neglected Mechanism in Structural and Stratigraphic Studies: New Evidence from the Midcontinent, USA: Applied Geophysics, Inc., 109 p.

This was a thorough documentation and proof of the supposition of a number of leading American geologists of the 1920's and 1930's that compaction of the sedimentary section over basement hills creates overlying anticlinal structures. This is a very fundamental cause of geological structure that even today (2007) is greatly underappreciated by the geological community - even though this publication leaves no room for doubt either as to its validity or its pervasiveness.


1984, Spokane Mountain Deposit, Northwest USA - a Uranium Discovery Resulting from Aeromagnetic Lineament Analysis in a Precambrian Metamorphic Terrane, in Proceedings of the Fourth International Conference on Basement Tectonics, Oslo, Norway: International Basement Tectonics Association, Salt Lake City.

This was a case history of the discovery of a uranium deposit found along a regional fault mapped by 3D stereo aeromagnetic techniques.


1976, Aeromagnetic Lineament Study of Covered Precambrian Basement, Southeastern Missouri, in R.A. Hodgson, et al, editor, Proceedings of the First International Conference on the New Basement Tectonics, Salt Lake City, Utah: Utah Geological Association, Pub. No. 5.

This was a focused study of an area in southeast Missouri that again showed that basement faults controlled later structure. A second phase of the study showed that magnetic methods mapped in detail the boundaries of a number of unmapped Proterozoic intrusions that were exposed at the surface in only two places in the study area.


1973, Pervasive Orthogonal Fracturing in Earth's Continental Crust: American Stereo Map Co., Tech. Pub., No. 2, 124 p.

In this paper, data were gathered from the literature on regional fracture zones and lineaments from a diversity of geological and geophysical studies to show the pervasiveness of orthogonal fracturing in the earth's crust. The 140-year old riddle of jointing in rocks was solved by tying joints directly to vertical movement of basement shear zones.


1972, Fundamental Characteristics of Aeromagnetic Lineaments, their Geological Significance and their Significance to Geology (The New Basement Tectonics): American Stereo Map Co., Tech. Pub., No. 1, 94 p.

The author was the first earth scientist to use the term "aeromagnetic lineament," and he showed that these features, as observed on aeromagnetic maps, most often coincided with basement shear zones and that their movement controlled much, or most, later geology - hence "the new basement tectonics," or more to the point, "reactivation tectonics."


 1971, Morphological Study of Geophysical Maps [incl. aeromagnetic maps] by Viewing in Three-Dimensions: Geophysics, vol. 36, p. 396-414.

This is the first, and only, published paper by the author on the use of 3D stereo maps (viewed with red/blue glasses) for interpreting magnetic and gravity maps - a technique he has used continuously for 40 years, and still uses, as a powerful interpretational tool.


1970, Aeromagnetics and Geology of 36 Copper and Molybdenum Porphyry Deposits in the Western United States and British Columbia (with C.A. Mardirosian): Distributed by American Stereo Map Co., Salt Lake City, Utah, 122p.

This paper was a compendium of all the then-publically available aeromagnetic maps over Cu and Mo porphyry deposits. From this, we were able to prove the idea, for the first time, that ore districts are generally characterized by aeromagnetic lows. We also concluded that a certain percentage of ore districts lie on regional structures.


1966, Geophysical Case History, Marcona [Iron] Mining District, Peru, in Mining Geophysics, vol. 1: Society of Exploration Geophysicists, Tulsa, Oklahoma.

This paper summarized seven years of the author's work in Peru, 1957-1964, in which a number of major iron ore bodies were discovered.


1965, Standard Curves for Magnetic Anomalies over Long Horizontal Cylinders: Geophysics, vol. 30, p. 818-828.

Likewise, this paper saw a fair amount of use before the proliferation of computer methods for interpretation.


1961, Standard Curves for Interpretation of Magnetic Anomalies over Long Tabular Bodies: Geophysics, vol. 28, p. 161-200. Best Paper Award for 1963 from Society of Exploration Geophysicists. (Also reprinted in Mining Geophysics, vol. II, SEG, Tulsa, 1967.)

This paper, and its standard curves, was the bible for magnetic interpretation for over a decade before the advent of computer techniques in magnetic modeling. It was used by magnetics and gravity specialists world wide, the author having been shown dog-eared copies in Spain and India in the late 1970's.

* Gay has published a number of articles on other geological and geophysical topics not involving magnetic methods.

**Best Paper Award for 1963, from the Society of Exploration Geophysicists

l Keynote Speaker

ll Invited Papers