Professional Information for

David W. Baker

P.O. Box 906

Monarch, MT 59463

Telephone: (406) 236-5934

Internet Contact Link

Education

Diplom Nat. Sci., Earth Science, Swiss Federal Institute of Technology, 1964

Ph.D., Geology, University of California at Los Angeles, 1969

Post-Doctoral Fellow, Yale University, 1970

Professional Experience

Research Geologist, Gulf Oil Corp., 1976-1983

Consulting Geologist and Tectonophysicist, Little Belt Consulting Services, Monarch, Montana, 1984-present

Skill Summary

My company is Little Belt Consulting Services. It is primarily involved with mineral deposit evaluation using the following techniques:

• Geologic mapping and surveying (air photo, GPS, tape/compass/altimeter)
• Mineralogical/petrographic/petrologic studies ("in-house" petrographic lab with petrographic and ore microscopes and access to microprobe and SEM facilities)
• Geophysical and geochemical surveys
• Digital processing of satellite imagery, "ground-truthing" spectral signatures with X-ray clay mineral studies and portable high-resolution spectrometer
• Economic analyses

However, I also develop websites for the Internet that provide an overview of complicated technical material.

I am unabashedly enthusiastic about the geology of Central Montana. I was born in Great Falls and graduated from Great Falls High School. Having worked in many other parts of the world, it is a pleasure to be able to describe and discuss local features with the knowledge that some of these are unique in the world and some are such outstanding examples that people come from other parts of the globe to see them.

PROFESSIONAL AFFILIATIONS

American Geophysical Union, Montana Geological Society, Geological Society of America, Tobacco Root Geological Society, American Association for the Advancement of Science, Schweizerische Mineralogische und Petrographische Gesellschaft, National Center for Science Education

Listed In:

American Men and Women of Science

Marquis Who's Who in America

Publications on Gemstones

Cornflower-blue sapphires from Yogo Gulch in Montana are precious gemstones. The highly prized color results from the unusual conditions of formation. (Ultramafic) magma, generated in the asthenosphere at a depth of approximately 150 km, rose to the base of the crust (50 km depth) where it assimilated aluminum-rich rock. Corundum (sapphire) formed in the contact aureole and was then carried by the magma to the near-surface and intruded as a 5 km long dike. Diagnostic inclusions in Yogo sapphires are white "snowballs" of primary igneous analcime that formed at 50 km depth. The cornflower-blue color is a consequence of reducing conditions and low ferric iron content. Sapphires from western Montana formed at mid-crustal depths (20 - 30 km) under more oxidizing conditions. They have high iron contents which quench the red component in the transmission spectrum, thus shifting the color away from the cornflower-blue. The stones are heat-treated. A fine 1 carat heat-treated stone has a wholesale value of approximately $400 compared with $2500 for the untreated Yogo sapphire.

Baker, D.W. (Editor) (1994) Overview of the gemstone industry of Zambia. Export Board of Zambia. 4 vols., 290 p. (World Bank project) - articles by M. Picciani and others.

This 4 volume study, funded by the World Bank, provides an in-depth survey of the gemstone industry of Zambia with recommendations on how to greatly improve exploration, mining, lapidary, marketing, export, training, and safety aspects of the industry. Many of the recommendations have been implemented.

Publications on the Geology of Central Montana

Regional tectonic patterns in north-central Montana are the result of at least two periods of quasi-flat-slab subduction. The Eocene-age Bearpaw Mountains are situated on a northeast-trending Precambrian suture zone between two Archean-age micro-plates. This zone, known as the Great Falls Tectonic Zone (GFTZ), was the collision zone between the Hearne Province to the northwest and the Wyoming Province to the southeast. A COCORP seismic profile across the south flank of the Bearpaw Mountains shows the internal structure of the GFTZ with steeply-dipping Wyoming Province descending northwestward under the Medicine Hat Block. We consider the collision to have occurred about 2.7 billion years ago (=2.7 giga-anni or 2.7 Ga) during the Archean, with reactivation about 1.8 to 1.7 Ga during the Proterozoic.

During the Trans-Hudson Orogeny about 1.8 to 1.7 Ga, the Dakota Plate was subducted westward under most of Montana in a manner similar to India being subducted under the Himalayas. Some of the effects that can be attributed to this event include a doubling of the thickness of the lithosphere, potassic metasomatism of the upper mantle, underplating of the base of the crust with more than 10 km of magma, pervasive deformation and metamorphism of crustal rocks, and uplift with erosion of perhaps 10 to 15 km of crust before the transgression of Belt Series sediments about 1.58 Ga.

Laramide tectonics and volcanism affecting the Bearpaw Mountains from about 58 Ma (=58 mega-anni or 58 million years ago) to about 48 Ma resulted from the flat-slab configuration of the subducted oceanic Farallon Plate beneath Montana. The Bearpaw Mountains are an elliptical dome formed by uplifted basement rock. The dome is the northernmost of a series of Laramide uplifts that include the Little Belt, Big Snowy, Beartooth, and Bighorn Mountains. The GFTZ may have provided paths of easy migration for mantle-derived phonolite lava flows and shonkinite intrusions that are present in the overlying Bearpaw Mountains.

Baker, D.W. (1992) Central Montana Alkalic Province: critical review of Laramide plate tectonic models that extract alkalic magmas from abnormally thick Precambrian lithospheric mantle. Northwest Geology, vol. 20/21, p. 71-96.

The Central Montana Alkalic Province (CMAP) is characterized by highly alkalic magmas and abnormally thick lithospheric mantle. Recent studies of trace element and isotope geochemistry show that Laramide magmas extracted low melting components, introduced during Proterozoic metasomatism, from lithospheric mantle. Two plate tectonic models are currently used to describe Laramide magmatism. The back-arc advection model heats the base of the lithosphere with back-arc circulation of the asthenosphere to generate magmas and, in the process, destroys most of a thick lithospheric mantle "keel" considered to have extended under Idaho and western Montana before the Cretaceous. The flat-slab model generates magma in the asthenosphere by lowering the melting point as water is released due to dehydration of amphibole and phlogopite in the flat subducted plate. The keel of mantle lithosphere under the CMAP is created as a result of "drag" from the moving, subjacent flat slab.

Laramide magmatism and tectonics of the Northern Rockies and the CMAP are consistent with the flat slab model for the subducted Farallon plate, but not with the back-arc advection model.. The slow SW-to-NE advance of the onset of volcanism across Idaho and Montana and the magmatic gap in the Paleocene correlate with an increasing plate convergence rate and are consistent with an apparent "hinging upwards" of the subducted Farallon plate rather than the migration of the hinge line. Major gold deposits (Kendall, Zortman, Judith Mountains) in the CMAP are associated with acidic rocks emplaced during the Late Cretaceous-Paleocene northeastward advance of volcanism. Lead-zinc-silver deposits (Neihart, Hughesville, Castle Mountains) and sapphire deposits (Yogo Gulch) are associated with the Eocene igneous flare-up, which correlates with a decrease in the plate convergence rate and a slight settling and decoupling of the flat slab from the base of the lithosphere. The high potassium content of Eocene magmas was extracted by magmas rising through the mantle lithosphere from veins that were emplaced about 1.8 billion years ago.

Baker, D.W. and Berg, R.B. (Editors) (1991) Guidebook of the Central Montana Alkalic Province - Geology, Ore Deposits and Origin. Montana Bureau of Mines and Geology Special Publication 100, 201 p.

Guidebook to the igneous rocks and mining districts of Central Montana. The igneous rocks are characterized by high potassium contents. Field trips with road logs and descriptions of individual mountain ranges.

Baker, D.W., McBride, G. and Dahy, J. (1991) Field guide to the Little Belt Mountains. In Guidebook of the Central Montana Alkalic Province - Geology, Ore Deposits and Origin. Montana Bureau of Mines and Geology Special Publication 100, p. 145-162.

Chamberlain, V.R. and Baker, D.W. (1991) Field Guide - Great Falls to Ryan Dam via Rainbow Dam Road. Little Belt Press, Monarch, Montana, 15 p.

Technical Reports and Publications on Oil Exploration

Pervasive gravity sliding on the flanks of the Bearpaw Mountains occurred on two bentonite beds in the Marias River Formation (Upper Cretaceous Colorado Group). The gravity sliding coincided with rapid loading as a thick pile of volcanics accumulated on the uplifted dome. The best explanation for blocks of strata gliding down slopes less than 3 degrees is the overpressure that developed in and below the bentonite layers due to a transformation of smectite (montmorillonite) to illite, which created superior seals and released structurally-bound water. Above the detachment zone, strata include the Eagle Formation, a wide-spread shoreface sandstone unit 45 to 75 m (150 to 250 ft) thick, and the overlying Claggett Shale, 135 to 170 m (450 to 550 ft) thick. Sandwiched between source rocks, the very porous and permeable Eagle Sandstone is a prolific reservoir for shallow gas trapped in structures 150 to 750 m deep.

Gravity sliding broke the overlying strata into many blocks, creating a large number of structural traps in the Bearpaw Mountains and their perimeter, continuing outward more than 50 km. Slide-induced faulting produced pull-apart structures in the "heads" of the gravity slides and compressional "pop-up" structures, containing imbricated Eagle strata, in the "toes" of the slides. Fault displacements are erratic and can vary from 10 to 400 m between adjacent blocks of strata. While the slide structures were generally evident from early surface geology and drilling, recent seismic data have provided clear images and a better understanding of the structural form of the gas traps.

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Baker, D.W. (1983) Oil Exploration in the Williston Basin: regional tectonics, LANDSAT imagery, groundwater flow, and migration of hydrocarbons. Gulf Research & Development Corp. Tech. Mem.

The Williston Basin in North Dakota is located on top of a 1.8 billion year old suture zone where two continents collided to form a mountain range. Reactivation of these old structures resulted in the traps for oil as it migrated through the basin. A series of 7 reports document the plate tectonics, regional tectonics, development of features visible on LANDSAT imagery, groundwater flow and migration of hydrocarbons.

Publications on Experimental Rock Deformation

Clay platelets are deposited on the sea floor in random orientations, but tend to rotate towards the horizontal as water is squeezed out during burial compaction. X-ray techniques were used in an experimental study to document a simple relationship between the loss of porosity and the strength of the preferred orientation of the clay platelets. This strong preferred orientation, due to volume loss during compaction, has a large effect on the fabric of mica in slate that forms during tectonic deformation. Deformation, loss of porosity, and preferred orientation are modeled quantitatively using data from the Welsh Slate Belt.

Wenk, H.R., Venkitasubramanyan, C.S., Baker, D.W. and Turner, F.J. (1973) Preferred orientation in experimentally deformed limestone. Contributions to Mineralogy and Petrology, v. 38, p. 81-114.

This study shows how calcite crystals become aligned during deformation experiments at high temperatures and pressures. Inverse pole figures show the effect of the conditions of deformation. Spherical harmonic analysis was used to analyze X-ray data.

Baker, D.W., Carter, N.L. and George, R.P. (1972) Seismic velocity anisotropy calculated for ultramafic minerals and aggregates. In Heard, H.C., Borg, I., Carter, N.L. and Raleigh, C.B. (Editors) Flow and Fracture of Rocks, American Geophysical Union Geophysical Monograph 16, p. 157-166.

The Schwartz-Cristoffel equation is used to calculate the seismic velocity behavior in highly anisotropic single crystals and rocks. Rocks are modeled by averaging the elastic compliances and stiffness coefficients. In the ultramafic rocks studied the seismic velocity anisotropy is dominated by the preferred orientation of olivine.

Wecker, S.M., Davidson, T. and Baker, D.W. (1972) Preferred orientation of crystallites in uniaxally deformed polytetrafluorethylene. Journal of Applied Physics, v. 43, p. 4344-4348.

The alignment of crystallites in teflon during stretching is studied using X-ray techniques.

Baker, D.W. (1972) Symmetry of the orientation distribution in crystal aggregates and mechanical twinning. Proceedings of the First International Symposium on Quantitative Texture Analysis, Polish Academy of Sciences, Krakow, p. 125-147.

Baker, D.W. (1971) X-ray analysis of preferred orientation of ore minerals--in particular with the pole-figure goniometer. (Translation from German and revision of paper by K.v. Gehlen, 1960, Beitr. Miner. Petrog., v. 7, p. 340-388), Siemens Review, v. 38, p. 45-64.

Baker, D.W. (1970) On the symmetry of orientation distribution in crystal aggregates. Advances in X-ray Analysis, v. 13, p. 425-454.

Baker, D.W., Wenk, H.R. and Christie, J.M. (1969) X-ray analysis of preferred orientation in fine-grained quartz aggregates. Journal of Geology, v. 77, p. 144-172.

Wenk, H.R., Baker, D.W. and Griggs, D.T. (1967) X-ray fabric analysis of hot-worked and annealed flint. Science, v. 157, p. 1447-1449.

Publications on Plate Tectonics and Petrofabrics

Carter, N.L., Baker, D.W. and George, R.P. (1972) Seismic anisotropy, flow, and constitution of the upper mantle. In Heard, H.C., Borg, I., Carter, N.L. and Raleigh, C.B. (Editors) Flow and Fracture of Rocks, American Geophysical Union Geophysical Monograph 16, p. 167-190.

Seismic velocity anisotropy in the upper mantle under the oceans is controlled by the orientation of olivine crystals. The results of lab studies of the experimental deformation of olivine are used to interpret the pattern of flow of the mantle near and away from oceanic ridges.

Griggs, D.T. and Baker, D.W. (1969) The mechanism of deep-focus earthquakes. In Mark, H. and Fernback, S. (Editors) Properties of Matter under Unusual Conditions, Wiley & Sons, New York, p. 23-42.

Numerical analysis of heat-flow instabilities during shearing deformation of mantle rocks is used to evaluate the mechanism of shear melting as a mechanism for earthquakes that originate at depths of 400 to 700 km.

Lunardi, L.F., Bishop, J.R. and Baker, D.W. (in press) Piezoelectric fabric of quartzite mylonite from the Northern Snake Range, Nevada. Journal of Structural Geology.

Tensor analysis of piezoelectric data and spherical harmonic analysis of x-ray pole figure data are combined to demonstrate the preferred orientation of quartz crystals in a shear zone in Nevada. The rock has a piezoelectric effect so that when it is squeezed, it develops a positive charge on one side of the specimen and a negative charge on the other. Positive ends of a-axes in right-handed crystals are aligned with negative ends of a-axes in left-hand crystals to produce this effect. This is the first documentation of this effect in a shear zone.

Riekels, L.M. and Baker, D.W. (1977) The origin of the double maximum pattern of optic axes in quartzte mylonite. Journal of Geology, v. 85, p. 1-14.

Spherical harmonic analysis of X-ray pole-figure data is used to determine the preferred orientation of quartz crystals in extremely deformed rock from the Moine thrust in Northwest Scotland.

Baker, D.W. and Riekels, L.M. (1977) Dauphiné twinning in quartzite mylonite. Journal of Geology, v. 85, p. 15-26.

The development of mechanical twinning in extremely deformed quartzite is studied statistically by analyzing orientation data obtained through spherical harmonic analysis of X-ray pole figures.

Baker, D.W. and Wenk, H.R. (1972) Preferred orientation in a low-symmetry quartz mylonite. Journal of Geology, v. 80, p. 81-105.

This is the first application of the spherical harmonic analysis method to analyze a highly deformed rock. The rock comes from the Moine thrust zone in Northwest Scotland. The c-axes of the quartz crystals are parallel to two planes to form the "crossed-girdle" pattern. Each girdle is perpendicular to a maximum of a-axes.

Scotese, C.R. and Baker, D.W. (1975) Continental drift reconstruction and animation. Journal of Geological Education, v. 23, p. 167-171.

Publications and Reports on Microcomputer Applications

Baker, D.W. (1986) SEED - a dBASE II inventory program for fields and crops that generates "seeding reports" for the Agricultural Stabilization an Conservation Service, for Montana Wheatgrowers Association, 68 p.

Baker, D.W. (1985) Using the BASIC compiler. MicroVision - The Victor Magazine, v. 1, no. 5-6, p. x-xiii.

Baker, D.W. (1985) How to learn to write assembly language programs. MicroVision - The Victor Magazine, v. 1, no. 2, p. 19-21.

Theses

Baker, D.W. (1964) The Windgaellen Fold, Canton Uri, Switzerland. Thesis Diplom. Nat. Sci., Swiss Federal Institute of Technology, Zurich, Switzerland.

Baker, D.W. (1961) Geology of Spencer Mountain, Somerset Co., Maine. B.S. Thesis, Massachusetts Institute of Technology.

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