Structural geology, geologic mapping, thermochronology
Education and/or Training
M.S. 2005, University of California, Los Angeles (Geology)
B.S. 2001, University of Arizona (Geology)
Projects and/or Research Interests
I serve as the manager of the Cook Inlet Basin Analysis Program and co-manager of the Interior Basins Program at the State of Alaska, Division of Geological & Geophysical Surveys (DGGS), for which we conduct field-based stratigraphic, structural, petrologic, and petroleum systems studies to assess the hydrocarbon potential of Alaska's sedimentary basins and reconstruct their geologic histories. My research interests center on the application of geologic mapping, interpretation of map-scale structural geometries, outcrop structural kinematics, and thermochronology to understand how basin margins deform over time, the implications for basin subsidence, and the evolution of potential structural hydrocarbon traps. These results are integrated with results of DGGS stratigraphic field studies to develop source-to-sink histories of prospective and potentially prospective hydrocarbon basins.
My work in Alaska has been focused in the Cook Inlet basin, North Slope and northern foothills of the Brooks Range, Alaska Peninsula, and Susitna and Tanana/Nenana basins. I have also led, or collaborated on geologic research projects in Bolivia, Papua New Guinea, Nepal, Iran, and southern Mexico.
Professional Experience
2006-present, Geologist, State of Alaska, Division of Geological & Geophysical Surveys, Fairbanks, AK
2005-2006, Operations geologist, ConocoPhillips Alaska, Anchorage, AK
Selected Professional Activities
AFFILIATIONS
2012-present, Affiliate Faculty, University of Alaska, Fairbanks, Geology and Geophysics Dept.
Member, Geological Society of America
Member, American Association of Petroleum Geologists
Member, Phi Beta Kappa Honor Society
AWARDS
2001, Outstanding Graduating Senior Award, Department of Geosciences, University of Arizona
2000, Evans B. Mayo Award, outstanding achievement, geology field camp, University of Arizona
Selected Publications
- Gillis, R.J., Trop, J.M., and Kuyl, Leo, 2024, Preliminary description and interpretation of the Doone Creek fault and associated structures: The potential offset and northeastward continuation of the Bruin Bay fault system in the south-central Talkeetna Mountains, Alaska: Alaska Division of Geological & Geophysical Surveys Preliminary Interpretive Report 2024-1, 18 p. https://doi.org/10.14509/31108
- Gillis, R.J., Wartes, M.A., Herriott, T.M., LePain, D.L., Benowitz, J.A., Wypych, Alicja, Donelick, R.A., O'Sullivan, P.B., and Layer, P.W., 2022, 40Ar/39Ar and U-Pb geochronology of Cretaceous-Paleocene igneous rocks and Cenozoic strata of northwestern Cook Inlet, Alaska: Linkages between arc magmatism, cooling, faulting, and forearc subsidence: Alaska Division of Geological & Geophysical Surveys Professional Report 125 v. 1.1, 78 p. https://doi.org/10.14509/30554
- Zippi, P.A., Gillis, R.J., Montayne, Simone, and Loveland, A.M., 2021, Palynological and thermal maturity analysis of outcrop samples from the Kenai, Seldovia, and Tyonek quadrangles, Cook Inlet region, Alaska: Alaska Division of Geological & Geophysical Surveys Raw Data File 2021-8, 4 p. https://doi.org/10.14509/30660
- Herriott, T.M., Crowley, J.L., Schmitz, M.D., Wartes, M.A., and Gillis, R.J., 2019, Exploring the law of detrital zircon: LA-ICP-MS and CA-TIMS geochronology of Jurassic forearc strata, Cook Inlet, Alaska, USA: Geology, v. 47.
https://doi.org/10.1130/G46312.1
- Herriott, T.M., Wartes, M.A., O'Sullivan, P.B., and Gillis, R.J., 2019, Detrital zircon maximum depositional dates for the Jurassic Chinitna and Naknek Formations, lower Cook Inlet, Alaska: A preliminary view: Alaska Division of Geological & Geophysical Surveys Preliminary Interpretive Report 2019-5, 11 p. https://doi.org/10.14509/30180
- Gillis, R.J., Fitzgerald, P.G., Ridgway, K.D., Keough, B.M., Benowitz, J.A., and Allen, W.K., 2019, Overview of the new 1:25,000-scale geologic mapping of the McCallum-Slate Creek fault system, eastern Alaska Range, Alaska: Alaska Division of Geological & Geophysical Surveys Preliminary Interpretive Report 2018-3, 10 p. https://doi.org/10.14509/30136
- Herriott, T.M., Wartes, M.A., Decker, P.L., Gillis, R.J., Shellenbaum, D.P., Willingham, A.L., and Mauel, D.J., 2018, Geologic map of the Umiat-Gubik area, central North Slope, Alaska: Alaska Division of Geological & Geophysical Surveys Report of Investigation 2018-6, 55 p., 1 sheet, scale 1:63,360. https://doi.org/10.14509/30099
- Betka, P.M., Gillis, R.J., and Benowitz, J.A., 2017, Cenozoic sinistral transpression and polyphase slip within the Bruin Bay fault system, Iniskin-Tuxedni region, Cook Inlet, Alaska: Geosphere, v. 13, no. 5, p. 1806-1833.
https://doi.org/10.1130/GES01464.1
- Gillis, R.J., Benowitz, J.A., O'Sullivan, P.B., Layer, P.W., and Wartes, M.A., 2017, Zircon U-Pb and 40Ar/39Ar results from dikes collected within the Bruin Bay fault zone, lower Cook Inlet: Alaska Division of Geological & Geophysical Surveys Raw Data File 2017-7, 14 p. https://doi.org/10.14509/29750
- Gillis, R.J., 2016, Discovery of a new sandstone with residual oil in Maastrichtian(?) strata at Shelter Creek, lower Cook Inlet, Alaska, in Herriott, T.M., ed., Petroleum-related geologic studies in lower Cook Inlet during 2015, Iniskin-Tuxedni region, south-central Alaska: Alaska Division of Geological & Geophysical Surveys Preliminary Interpretive Report 2016-1-7, p. 51-58. https://doi.org/10.14509/29541
- Gillis, R.J., ed., 2015, Overview of 2014 energy-focused studies in Susitna basin, south-central Alaska, and preliminary results: Alaska Division of Geological & Geophysical Surveys Preliminary Interpretive Report 2015-3, 34 p. https://doi.org/10.14509/29408
- Gillis, R.J., Herriott, T.M., and Tsigonis, R.M., 2015, Preliminary results of reconnaissance structural studies of the western Susitna basin, south-central Alaska, in Gillis, R.J., ed., Overview of 2014 energy-focused studies in Susitna basin, south-central Alaska, and preliminary results: Alaska Division of Geological & Geophysical Surveys Preliminary Interpretive Report 2015-3-5, p. 25-34. https://doi.org/10.14509/29469
- Betka, P.M., and Gillis, R.J., 2014, Preliminary characterization of brittle deformation on the Iniskin Peninsula: Implications for the kinematic history of the Bruin Bay fault system, lower Cook Inlet, Alaska: Alaska Division of Geological & Geophysical Surveys Preliminary Interpretive Report 2014-5, 14 p. https://doi.org/10.14509/29130
- Gillis, R.J., ed., 2014, Cook Inlet program 2013 field studies: Observations and preliminary interpretations from new 1:63,360-scale geologic mapping of the Iniskin Peninsula, lower Cook Inlet, Alaska: Alaska Division of Geological & Geophysical Surveys Preliminary Interpretive Report 2014-2, 31 p. https://doi.org/10.14509/27303
- Gillis, R.J., Wartes, M.A., Herriott, T.M., Bull, K.F., Decker, P.L., and Betka, P.M., 2014, Overview of new 1:63,360-scale geologic mapping of the Iniskin Peninsula, lower Cook Inlet, Alaska, in Gillis, R.J., ed., Cook Inlet program 2013 field studies: Observations and preliminary interpretations from new 1:63,360-scale geologic mapping of the Iniskin Peninsula, lower Cook Inlet, Alaska: Alaska Division of Geological & Geophysical Surveys Preliminary Interpretive Report 2014-2-1, p. 3-6. https://doi.org/10.14509/27306
- Gillis, R.J., Stanley, R.G., LePain, D.L., Mauel, D.J., Herriott, T.M., Helmold, K.P., Peterson, C.S., Wartes, M.A., and Shellenbaum, D.P., 2013, Status of a reconnaissance field study of the Susitna basin, 2011: Alaska Division of Geological & Geophysical Surveys Preliminary Interpretive Report 2013-4, 8 p. https://doi.org/10.14509/25015
- Wartes, M.A., Gillis, R.J., Herriott, T.M., Stanley, R.G., Helmold, K.P., Peterson, C.S., and Benowitz, J.A., 2013, Summary of 2012 reconnaissance field studies related to the petroleum geology of the Nenana basin, interior Alaska: Alaska Division of Geological & Geophysical Surveys Preliminary Interpretive Report 2013-2, 13 p. https://doi.org/10.14509/24880
- Gillis, R.J., ed., 2013, Overview of 2012 field studies: Upper Alaska Peninsula and west side of lower Cook Inlet, Alaska: Alaska Division of Geological & Geophysical Surveys Preliminary Interpretive Report 2013-1, 48 p. https://doi.org/10.14509/24824
- Gillis, R.J., 2013, Overview of 2012 field studies: Upper Alaska Peninsula and west side of lower Cook Inlet, Alaska, in Gillis, R.J., ed., Overview of 2012 field studies: Upper Alaska Peninsula and west side of lower Cook Inlet, Alaska: Alaska Division of Geological & Geophysical Surveys Preliminary Interpretive Report 2013-1A, p. 1-4. https://doi.org/10.14509/24844
- Gillis, R.J., Swenson, R.F., Wartes, M.A., and Frohman, R.A., 2013, Reconnaissance investigations of the Bruin Bay fault system along the western margin of lower Cook Inlet and upper Alaska Peninsula, in Gillis, R.J., ed., Overview of 2012 field studies: Upper Alaska Peninsula and west side of lower Cook Inlet, Alaska: Alaska Division of Geological & Geophysical Surveys Preliminary Interpretive Report 2013-1G, p. 33-37. https://doi.org/10.14509/24850
- Decker, P.L., Gillis, R.J., Helmold, K.P., and Peterson, Shaun, 2012, Summary of fossil fuel and geothermal resource potential in the Railbelt energy region, in Swenson, R.F., Wartes, M.A., LePain, D.L., and Clough, J.G., Fossil fuel and geothermal energy sources for local use in Alaska: Summary of available information: Alaska Division of Geological & Geophysical Surveys Special Report 66J, p. 95-112. https://doi.org/10.14509/24433
- Benowitz, J.A., Haeussler, P.J., Wallace, W.K., O'Sullivan, P.B., and Gillis, R.J., 2012, Cenozoic tectono-thermal history of the Tordrillo Mountains, Alaska: Paleocene-Eocene ridge-subduction, decreasing relief, and late Neogene faulting: Geochemistry, Geophysics, Geosystems, v. 13, issue 4. https://dx.doi.org/10.1029/2011GC003951
- Finzel, E.S., Gillis, R.J., Ridgway, K.D., and LePain, D.L., 2009, Preliminary evaluation of basin margin exhumation and provenance of Cenozoic strata, Chuitna and Beluga rivers area, Cook Inlet forearc basin, Alaska: Alaska Division of Geological & Geophysical Surveys Preliminary Interpretive Report 2009-4, 16 p. https://doi.org/10.14509/19641
- Gillis, R.J., LePain, D.L., Ridgway, K.D., and Finzel, E.S., 2009, A reconnaissance view of an unnamed fault near Capps Glacier, northwestern Cook Inlet basin, and its potential as a regional-scale, basin-controlling structure: Alaska Division of Geological & Geophysical Surveys Preliminary Interpretive Report 2009-3, 9 p. https://doi.org/10.14509/19503
- Decker, P.L., Reifenstuhl, A.E., and Gillis, R.J., 2008, Structural linkage of major tectonic elements in the Ugashik-Becharof Lakes region, northeastern Alaska Peninsula, in Reifenstuhl, R.R., and Decker, P.L., eds., Bristol Bay-Alaska Peninsula region, overview of 2004-2007 geologic research: Alaska Division of Geological & Geophysical Surveys Report of Investigation 2008-1F, p. 85-103, 1 sheet. https://doi.org/10.14509/17946
- Decker, P.L., Reifenstuhl, R.R., Gillis, R.J., and Loveland, Andrea, 2008, Revised geologic map and structural model of the Staniukovich Peninsula-Herendeen Bay area, in Reifenstuhl, R.R., and Decker, P.L., eds., Bristol Bay-Alaska Peninsula region, overview of 2004-2007 geologic research: Alaska Division of Geological & Geophysical Surveys Report of Investigation 2008-1I, p. 161-176, 2 sheets, scale 1:50,000. https://doi.org/10.14509/17949
- Horton, B.K., Hassanzadeh, J., Stockli, D.F., Axen, G.J., Gillis, R.J., Guest, B., Amini, A., Fakhari, M., Zamanzadeh, S.M., and Grove, M., 2008, Detrital zircon provenance of Neoproterozoic to Cenozoic deposits in Iran, Implications for chronostratigraphy and collisional tectonics: Tectonophysics, v. 451, issue 1, p. 97-122. http://dx.doi.org/10.1016/j.tecto.2007.11.063
- Gillis, R.J., Horton, B.K., and Grove, M., 2006, Thermochronology, geochronology, and upper crustal structure of the Cordillera Real: Implications for Cenozoic exhumation of the central Andean plateau: Tectonics, v.25, TC6007. http://dx.doi.org/10.1029/2005TC001887
- Gillis, R.J., Gehrels, G.E., Ruiz, J., and Flores de Dios Gonzales, L.A., 2005, Detrital zircon provenance of Cambrian-Ordovician and Carboniferous strata of the Oaxaca Terrane: southern Mexico: Sedimentary Geology, Special Volume 182, p. 87-100. http://dx.doi.org/10.1016/j.sedgeo.2005.07.013
Selected Presentations
- Gillis, R.J., Trop, J.M., and Kuyl, Leo, 2023, The Doone Creek fault: A newly identified structure in the Talkeetna Mountains, Alaska, that belongs to a system of north- and northeast-trending faults that may delineate the Paleogene forearc basin boundary (poster): Alaska Geological Society Technical Conference, Anchorage, Alaska, April 22, 2023: Alaska Division of Geological & Geophysical Surveys, 1 sheet. https://doi.org/10.14509/31023
- Gillis, R.J., Shellenbaum, D.P., Herriott, T.M., Mauel, D.J., Wartes, M.A., Decker, P.L., Freeman, L.K., LePain, D.L., Gregersen, L.S., Elliott, B.A., Benowitz, J.A., and O'Sullivan, P.B., 2016, Results of new 1:63,360-scale geologic mapping and related field studies in the south-central Tyonek Quadrangle, south-central Alaska: Middle Eocene transtension and post-Oligocene inversion on the northwest periphery of the Cook Inlet forearc basin (poster): Alaska Geological Society Technical conference, Fairbanks, Alaska, April 22, 2016: Alaska Division of Geological & Geophysical Surveys, 1 sheet. https://doi.org/10.14509/29672
- Gillis, R.J., Wartes, M.A., LePain, D.L., Decker, P.L., Herriott, T.M., and O'Sullivan, R.B., 2014, Structural, stratigraphic, and thermochronologic evidence for Eocene transtension and exhumation along the arc-forearc margin, Cook Inlet, Alaska: Alaska Geological Society Annual Technical Conference, Abstracts, p. 10.
- Gillis, R.J., Wartes, M.A., Benowitz, J.A., O'Sullivan, P.B., Metcalf, J.R., and Herriott, T.M., 2014, Forearc cooling during two different modes of flat-slab subduction, insights from lower-temperature bedrock and detrital thermochronology, south-central Alaska: Geological Society of America, Abstracts with Programs v. 46, no. 6, p. 376. https://gsa.confex.com/gsa/2014AM/finalprogram/abstract_249867.htm
- Gillis, R.J., Wartes, M.A., and O'Sullivan, P.B., 2011, Preliminary findings from reconnaissance structural studies along the Bruin Bay fault system and adjacent areas, south-central Alaska: AAPG Pacific Section Meeting, Anchorage, Alaska, May 10, 2011: Alaska Division of Geological & Geophysical Surveys, 1 sheet. https://doi.org/10.14509/23403
- Gillis, R.J., LePain, D.L., Reifenstuhl, R.R., and Helmold, K.P., 2009, Regional Paleocene-Eocene exhumation of the North American forearc basin margin, south-central Alaska, recorded by apatite fission-track thermochronology (poster): Geological Society of America Abstracts with Programs, v. 41, no. 7: Alaska Division of Geological & Geophysical Surveys, 1 sheet. https://doi.org/10.14509/21163
- Gillis, R.J., Reifenstuhl, R.R., and Decker, P.L., 2008, Implications of new apatite and zircon fission-track thermochronology for Mesozoic and Tertiary basin margin exhumation, upper Alaska Peninsula (poster): 11th International Conference on Thermochronometry, Anchorage, Alaska, September 15th-19th, 2008: Alaska Division of Geological & Geophysical Surveys, 1 sheet. https://doi.org/10.14509/21826
