Stratigraphic architecture and sediment provenance provide important insights into processes of basin formation, filling, and sediment dispersal that are controlled by the tectonic evolution of ancient mountain belts and active continental margins. As a stratigrapher, my research interests focus on integrating basin stratigraphy and provenance data to constrain long-term variability associated with lithospheric-scale processes such as the evolution of magmatic systems and plate-boundary fault zones.
Mesozoic Tectonics of the Western U.S.
 |
 |
Proposed tectonic model for evolution of the Blue Mountains region and central Nevada during Middle Triassic through Early Cretaceous time. |
Detrital and magmatic zircons separated from sedimentary and volcanic rocks of the Blue Moutains region. |
In my Ph.D. research, I am investigating Mesozoic rocks of eastern Oregon and western Idaho to answer some long-standing questions about the geologic history of the Pacific Northwest. Rocks of the Blue Mountains region are relatively undeformed and occupy a critical position between coeval lithotectonic assemblages to the north in British Columbia and to the south in California and Nevada. Recent studies underscore an enduring lack of consensus regarding the Mesozoic tectonic history of the western United States. Despite a rich history of investigations in the Blue Mountains, fundamental aspects of the regional geology remain ambiguous, hampering our ability to accurately reconstruct the pre-Cretaceous evolution of the western Laurentian margin. In collaboration with Becky Dorsey (my dissertation advisor) and Jeff Vervoort at Washington State University, I am using trace-element, samarium-neodymium isotopic, and detrital-zircon provenance analysis of mudrocks and sandstones to characterize the tectonic settings of sediment source areas and to constrain the timing of terrane accretion in the region. Integration of my new data with existing information from California, Nevada, and southern British Columbia is generating new insights into the history of Mesozoic terrane accretion and related basin evolution in western North America.
This research has been supported by grants from the National Science Foundation to Becky Dorsey (EAR-0537691) and Jeff Vervoort (EAR-0537913), and grants from GSA, AAPG, SEPM, Sigma Xi, and the University of Oregon to LaMaskin.
Publications and Abstracts Resulting from this research:
Dorsey, R.J., and LaMaskin, T.A ., 2008, Mesozoic collision and accretion of oceanic terranes in the Blue Mountains Province of northeastern Oregon: New Insights from the stratigraphic record, in Spencer, J.,E. and Titley, S.R., eds., Circum-Pacific Tectonics, Geologic Evolution, and Ore Deposits: Tucson, Arizona, Arizona Geological Society, Digest 22. (PDF)
LaMaskin, T.A ., 2008, Late Triassic (Carnian-Norian) Mixed Volcaniclastic-Carbonate Facies of the Olds Ferry Terrane, Eastern Oregon and Western Idaho: in , Blodgett, R., and Stanley, G., eds ., The Terrane Puzzle: New Perspectives on Paleontology and Stratigraphy from the North American Cordillera: Geological Society of America Special Paper 442, p. 251-267. (PDF)
Dorsey, R.J., and LaMaskin, T.A., 2007, Stratigraphic record of Triassic-Jurassic collisional tectonics in the Blue Mountains Province, northeastern Oregon: American Journal of Science, vol. 307, p. 1167-1193. (PDF)
LaMaskin, T.A., Dorsey, R.J., and Vervoort, J.D., in press, Tectonic controls on mudrcok geochemistry, Mesozoic rocks of eastern Oregon and western Idaho: Implications for Cordilleran tectonics: submitted to Journal of Sedimentary Research.
LaMaskin, T.A., Dorsey, R.J., and Vervoort, J.D., 2008, Provenance of Mesozoic rocks in eastern Oregon and western Idaho (abstr.): Oregon Academy of Sciences, Portland, Oregon. (PDF)
LaMaskin, T.A., Vervoort, J. and Dorsey, R.J., 2008, Geochemical, Isotopic and Detrital-Zircon Provenance of Mesozoic Rocks, Oregon and Idaho, U.S.A. (abstr.): Goldschmidt 2008, Vancouver, B.C., Geochimica et Cosmochemica. (PDF)
LaMaskin, T.A., Vervoort, J. and Dorsey, R.J., 2007, Geochemistry of Triassic and Jurassic mudrocks in the Blue Mountains, eastern Oregon: new insights into sedimentary provenance and basin evolution (abstr.): Geological Society of America Abstracts with Programs, Vol. 39, No. 4. (LINK)
LaMaskin, T.A., Dorsey, R.J., and Vervoort, J.D., 2007, Insights into the Mesozoic tectonic history of the Blue Mountains Province, eastern Oregon, from initial results of detrital zircon dating: Geological Society of America Abstracts with Programs, v. 39, No. 6, p. 208. (LINK)
Dorsey, R.J., and LaMaskin, T.A ., 2006, Mesozoic arc-arc and arc-continent collision in the Blue Mountains Province, northeastern Oregon: A new hypothesis to be tested (abstr.): Geological Society of America Abstracts with Programs, Vol. 38, No. 5, p. 36. (LINK)
LaMaskin, T.A., and Dorsey, R.J., 2006, Basinal response to nascent arc-arc collision: Late Triassic-Early Jurassic of the Blue Mountains Province, northeastern Oregon (abstr.): Geological Society of America Abstracts with Programs, Vol. 38, No. 5, p. 36. (LINK)
LaMaskin, T.A., 2005, Mixed carbonate-volcaniclastic facies of the Olds Ferry terrane, eastern Oregon and western Idaho (abstr.): Geological Society of America Abstracts with Programs, Vol. 37, No.7, p. 16. (LINK)
LaMaskin, T.A., Dorsey, R.J., and Northrup, C.J., 2004, Tectono-Stratigraphic Architecture of Upper Triassic Through Middle Jurassic Strata in Eastern Oregon: Implications for Tectonic Evolution of The Blue Mountains: (abstr.): Geological Society of America Abstracts with Programs, Vol. 36, No. 4, p. 36. (VIEW POSTER)
Devonian Sea-level History and Carbonate Platform Development in the Great Basin, U.S.
  |
 |
| Detailed sequence corellation of Late Devonian strata in the Great Basin. | View of Late Devonian cyclic carbontes looking north along the southern Egan Range in east-central Nevada. |
For my M.S. research, I investigated Late Devonian carbonate rocks in eastern Central Nevada to establish a sequence-stratigraphic framework and evaluate eustatic controls on basin architecture. In collaboration with Maya Elrick (my thesis advisor), I subdivided the Guilmette Formation carbonate platform into 3rd-order sequences based on carbonate facies assemblages and regional correlation of meter-scale cycle-stacking patterns. I established age control for fossiliferous intervals using conodont biostratigraphy with the help of Gil Klapper.
Through our collaborative work we recognized that the Fox Mountain Member of the underlying Simonson Formation and the formerly enigmatic "yellow-slope forming interval" of the basal Guilmitte Formation represent the transgressive-systems tract and highstand-systems tract of a single 3rd-order sequence. This regionally correlative rock package represents the Taghanic Onlap phase of Devonian eustatic sea-level rise. Using conodont biostratigraphy and sequence-stratigraphic patterns, we tied additional 3rd-order overlying variations in basin architecture to known global-eustatic pulses, demonstrating that platform carbonates of eastern Central Nevada were not affected by onset of the Antler orogeny until deposition of the overlying Pilot Shale.
LaMaskin, T.A ., and Elrick, M., 1997, Sequence Stratigraphy of the Middle to Upper Devonian Guilmette Formation, Southern Egan and Schell Creek Ranges, Nevada: in , Klapper, G., Murphy, M.A., and Talent, J.A., eds ., Paleozoic Sequence Stratigraphy, Biostratigraphy, and Biogeography: Studies in Honor of J. Granville (Jess) Johnson: GSA Special Paper 321. (PDF)
LaMaskin, T.A ., and Elrick, M., 1995, Sequence Stratigraphy of the Middle to Upper Devonian Guilmette Formation, Eastern Nevada: Linked Earth Systems (abstr.): 1995 Society of Economic Paleontologists and Mineralogists Meeting, St. Petersburg, Florida, Vol. 1.
LaMaskin, T.A., and Elrick, M., 1994, Facies Relationships and Characterization of Meter-scale, Upward-shallowing Cycles in the Upper Devonian Guilmette Formation, Eastern Great Basin (Abstr.): Geological Society of America Program with Abstracts, Vol. 26, No. 2, p. 65.
Contamination Assesment Methods
 |
 |
From 1995 to 2003, I worked as an Environmental Consultant specializing in soil and groundwater contamination investigation and remediation. During that time frame, I worked on projects ranging from small farm waste dumps to major Department of Defense Superfund sites. I was fortunate to work with a number of very talented scientists and engineers from across the country on a number of problems including natural attenuation of chlorinated solvents and subsurface geophysical assessment of waste extent.
LaMaskin, T.A ., Woodworth, A.D., Spangler, J.H., Welch, M.S., Sergi, S. and Banks, T.L., 2003, Conceptual Site Model Development for an Unlined Solid Waste Landfill in the Virginia Coastal Plain: Evidence for Natural Attenuation of Chlorinated Solvents (abstr.): Geological Society of America Program with Abstracts, Vol. 35, p. 1. (VIEW POSTER)
LaMaskin, T.A ., and Spencer, J.O., 2003, Subsurface Site Characterization Using the Integration of Multiple Data Platforms: The Whole is Greater Than the Sum of the Parts (abstr.): Geological Society of America Abstracts with Programs, Vol. 35, No. 6, p. 406. (VIEW POSTER)