Martha (Rebecca) Stokes, Ph.D.
Martha (Rebecca) Stokes is a Physical Scientist with the USGS Geology, Energy & Minerals (GEM) Science Center in Reston, VA.
Rebecca received her B.S. in Geology from Texas A&M University in 2006, and a M.S. (2008) and Ph.D. (2012) from Indiana University focused on metamorphic petrology and mineral fabric development. Rebecca was a Postdoctoral Associate at MIT from 2012-2013 where she led a team tasked with developing an alternative potash fertilizer using K-feldspar. In 2013, Rebecca joined Chevron ETC where she served as a clay mineralogist and led research efforts investigating methods to quantify rock fabric in unconventional shale reservoirs. Rebecca joined the USGS in 2020 where her principal research interests include: spectroscopic analysis of hydrocarbon bearing rocks, porosity and mineral fabric development in sedimentary rock systems, and cross-disciplinary approaches to explore complex geologic questions.
Professional Experience
August 2020 to Present: Physical Scientist, USGS Geology, Energy, and Minerals Science Center, Reston, VA
September 2013-October 2019: Research Scientist, Chevron ETC, Houston, TX
September 2012-September 2013: Postdoctoral Research Associate, Massachusetts Institute of Technology, Cambridge, MA
Education and Certifications
Ph.D. Geology, Indiana University, 2012
M.S. Geology, Indiana University, 2008
B.S. Geology, Texas A&M University, 2006
Affiliations and Memberships*
Clay Minerals Society, Member
Society of Core Analysts, Member
Geological Society of America, Member
American Association of Petroleum Geologists (AAPG), Member
Science and Products
Geochemical and isotopic data from glendonites and surrounding sediment, Carter Creek, North Slope Alaska
The dataset consists of geochemical and isotopic data from fine-grained sediments and glendonite crystals collected at Carter Creek on the North Slope of Alaska. Total Organic Carbon (TOC) values in the measured section were found to range between 0.5 and 3.5%, with a shift towards lower values in the uppermost 5 m of the section. Stable isotopes (13C) in organic matter were relatively stable thro
Total neutron scattering of methane in Niobrara Formation samples at the wet-gas maturity level
Petroleum within unconventional source-rock reservoirs is hosted in organic matter and mineral pore space as well as in voids and microfractures. Recent work has shown that for source-rock reservoirs in the dry gas window, significant portions of methane (CH4), the main component of petroleum at elevated maturities, can be stored within fine organic matter porosity. However, within reservoirs at l
Evidence for strain induced graphitization across a ductile fault zone
A suite of slate samples collected along a 2 km transect crossing the Lishan Fault in central Taiwan were evaluated to assess the role of ductile strain energy in natural graphitization at greenschist facies metamorphic conditions. Scanning electron microscope (SEM) imaging documents phyllosilicate and quartz replacement textures consistent cleavage development via dissolution-precipitation proces
Portable Raman spectroscopic analysis of bulk crushed rock
This study presents a simplified method and empirical relationships for determining organic matter thermal maturity using a portable Raman system equipped with a 785 nm laser, for analysis of crushed, whole-rock samples. Several sets of rocks comprised of shale and coal samples with various mineralogical composition, thermal maturity, total organic carbon (TOC), and age were used to test the metho
Strain induced molecular heterogeneity in ancient sedimentary organic matter mapped at nanoscales using optical photothermal infrared spectroscopy
Here we report ultra-high resolution infrared mapping of organic matter functional group distribution in Tasmanites (algal microfossils) from the Upper Devonian Ohio Shale using optical photothermal infrared spectroscopy (O-PTIR). O-PTIR is capable of rapidly measuring the vibrational response of samples in situ with ~500-nm spatial resolution, well below the infrared diffraction limit. Our result
Textural occurrence and organic porosity of solid bitumen in shales
This study presents Raman spectroscopic data paired with scanning electron microscopy (SEM) to assess solid bitumen composition and porosity development as a function of solid bitumen texture and association with minerals. A series of hydrous pyrolysis experiments (1-103 days, 300-370°C) using a low maturity (0.25% solid bitumen reflectance, BRo), high total organic carbon [(TOC), 14.0 wt. %] New
Deformation-induced graphitization and muscovite recrystallization in a ductile fault zone
A suite of slate samples collected along a 2 km transect crossing the Lishan fault in central Taiwan were evaluated to assess the role of ductile deformation in natural graphitization at lower greenschist facies metamorphic conditions. The process of natural aromatization, or graphitization, of an organic precursor is well established as a thermally driven process; however, experimental studies ha
Authors
Martha (Rebecca) Stokes, Aaron M. Jubb, Ryan J. McAleer, David Bish, Robert Wintsch
Insights into glendonite formation from the upper Oligocene Sagavanirktok Formation, North Slope, Alaska
The type locality for the upper Oligocene Nuwok Member of the Sagavanirktok Formation (Carter Creek, North Slope, Alaska, USA) contains abundant occurrence of glendonite, a pseudomorph after the calcium carbonate mineral ikaite, which typically forms in the shallow subsurface of cold marine sediments. The region during the time of Nuwok Member deposition was located at a high latitude, similar to
Authors
John W. Counts, Madeleine Vickers, Martha (Rebecca) Stokes, Whittney Spivey, Kristina Frank Gardner, Jean Self-Trail, Jared T. Gooley, Ryan J. McAleer, Aaron M. Jubb, David W. Houseknecht, Richard O. Lease, Neil Patrick Griffis, Martin S. Vickers, Kasia Śliwińska, Hannah Gail Dooley Tompkins, Adam M. Hudson
Evaluation of portable Raman spectroscopic analysis for source-rock thermal maturity assessments on bulk crushed rock
This study presents a simplified method and empirical relationships for determining organic matter thermal maturity using a portable Raman system equipped with a 785 nm laser, for analysis of crushed, whole-rock samples. Suites of rocks represented by shale and coal samples with various mineralogical composition, thermal maturity, and total organic carbon (TOC) were used to test the method and bui
Authors
Martha (Rebecca) Stokes, Aaron M. Jubb, Paul C. Hackley, Justin E. Birdwell, Elliott Barnhart, Clint Scott, Jenna L. Shelton, Margaret M. Sanders, Javin J. Hatcherian
Methane pore accessibility, densification, and accommodation by organic matter in the Niobrara Formation at wet-gas thermal maturity conditions
Petroleum within unconventional source-rock reservoirs is hosted in organic matter and mineral pore space as well as in voids and microfractures. Recent work has shown that for source-rock reservoirs in the dry gas window, significant portions of methane (CH4), the main component of petroleum at elevated maturities, can be stored within fine (<5 nm) organic matter porosity. However, within reservo
Authors
Aaron M. Jubb, Leslie F. Ruppert, Tristan G. A. Youngs, Tom Headen, Justin E. Birdwell, Michael Cheshire, Martha (Rebecca) Stokes
Mapping ancient sedimentary organic matter molecular structure at nanoscales using optical photothermal infrared spectroscopy
Elucidating the molecular structure of sedimentary organic matter (SOM) is key to understanding petroleum generation processes, as well as ancient sedimentary environments. SOM structure is primarily controlled by biogenic source material (e.g., marine vs. terrigenous), depositional conditions, and subsurface thermal history. Additional factors, e.g., strain, may also impact the molecular structur
Authors
Aaron M. Jubb, Martha (Rebecca) Stokes, Ryan J. McAleer, Paul C. Hackley, Eoghan Dillion, Jing Qu
Relating systematic compositional variability to the textural occurrence of solid bitumen in shales
This study presents Raman spectroscopic data paired with scanning electron microscopy (SEM) images to assess solid bitumen composition as a function of solid bitumen texture and association with minerals. A series of hydrous pyrolysis experiments (1–103 days, 300–370 °C) using a low maturity (0.25% solid bitumen reflectance, BRo), high total organic carbon [(TOC), 14.0 wt%] New Albany Shale sample
Authors
Martha (Rebecca) Stokes, Brett J. Valentine, Aaron M. Jubb, Paul C. Hackley
Science and Products
Geochemical and isotopic data from glendonites and surrounding sediment, Carter Creek, North Slope Alaska
The dataset consists of geochemical and isotopic data from fine-grained sediments and glendonite crystals collected at Carter Creek on the North Slope of Alaska. Total Organic Carbon (TOC) values in the measured section were found to range between 0.5 and 3.5%, with a shift towards lower values in the uppermost 5 m of the section. Stable isotopes (13C) in organic matter were relatively stable thro
Total neutron scattering of methane in Niobrara Formation samples at the wet-gas maturity level
Petroleum within unconventional source-rock reservoirs is hosted in organic matter and mineral pore space as well as in voids and microfractures. Recent work has shown that for source-rock reservoirs in the dry gas window, significant portions of methane (CH4), the main component of petroleum at elevated maturities, can be stored within fine organic matter porosity. However, within reservoirs at l
Evidence for strain induced graphitization across a ductile fault zone
A suite of slate samples collected along a 2 km transect crossing the Lishan Fault in central Taiwan were evaluated to assess the role of ductile strain energy in natural graphitization at greenschist facies metamorphic conditions. Scanning electron microscope (SEM) imaging documents phyllosilicate and quartz replacement textures consistent cleavage development via dissolution-precipitation proces
Portable Raman spectroscopic analysis of bulk crushed rock
This study presents a simplified method and empirical relationships for determining organic matter thermal maturity using a portable Raman system equipped with a 785 nm laser, for analysis of crushed, whole-rock samples. Several sets of rocks comprised of shale and coal samples with various mineralogical composition, thermal maturity, total organic carbon (TOC), and age were used to test the metho
Strain induced molecular heterogeneity in ancient sedimentary organic matter mapped at nanoscales using optical photothermal infrared spectroscopy
Here we report ultra-high resolution infrared mapping of organic matter functional group distribution in Tasmanites (algal microfossils) from the Upper Devonian Ohio Shale using optical photothermal infrared spectroscopy (O-PTIR). O-PTIR is capable of rapidly measuring the vibrational response of samples in situ with ~500-nm spatial resolution, well below the infrared diffraction limit. Our result
Textural occurrence and organic porosity of solid bitumen in shales
This study presents Raman spectroscopic data paired with scanning electron microscopy (SEM) to assess solid bitumen composition and porosity development as a function of solid bitumen texture and association with minerals. A series of hydrous pyrolysis experiments (1-103 days, 300-370°C) using a low maturity (0.25% solid bitumen reflectance, BRo), high total organic carbon [(TOC), 14.0 wt. %] New
Deformation-induced graphitization and muscovite recrystallization in a ductile fault zone
A suite of slate samples collected along a 2 km transect crossing the Lishan fault in central Taiwan were evaluated to assess the role of ductile deformation in natural graphitization at lower greenschist facies metamorphic conditions. The process of natural aromatization, or graphitization, of an organic precursor is well established as a thermally driven process; however, experimental studies ha
Authors
Martha (Rebecca) Stokes, Aaron M. Jubb, Ryan J. McAleer, David Bish, Robert Wintsch
Insights into glendonite formation from the upper Oligocene Sagavanirktok Formation, North Slope, Alaska
The type locality for the upper Oligocene Nuwok Member of the Sagavanirktok Formation (Carter Creek, North Slope, Alaska, USA) contains abundant occurrence of glendonite, a pseudomorph after the calcium carbonate mineral ikaite, which typically forms in the shallow subsurface of cold marine sediments. The region during the time of Nuwok Member deposition was located at a high latitude, similar to
Authors
John W. Counts, Madeleine Vickers, Martha (Rebecca) Stokes, Whittney Spivey, Kristina Frank Gardner, Jean Self-Trail, Jared T. Gooley, Ryan J. McAleer, Aaron M. Jubb, David W. Houseknecht, Richard O. Lease, Neil Patrick Griffis, Martin S. Vickers, Kasia Śliwińska, Hannah Gail Dooley Tompkins, Adam M. Hudson
Evaluation of portable Raman spectroscopic analysis for source-rock thermal maturity assessments on bulk crushed rock
This study presents a simplified method and empirical relationships for determining organic matter thermal maturity using a portable Raman system equipped with a 785 nm laser, for analysis of crushed, whole-rock samples. Suites of rocks represented by shale and coal samples with various mineralogical composition, thermal maturity, and total organic carbon (TOC) were used to test the method and bui
Authors
Martha (Rebecca) Stokes, Aaron M. Jubb, Paul C. Hackley, Justin E. Birdwell, Elliott Barnhart, Clint Scott, Jenna L. Shelton, Margaret M. Sanders, Javin J. Hatcherian
Methane pore accessibility, densification, and accommodation by organic matter in the Niobrara Formation at wet-gas thermal maturity conditions
Petroleum within unconventional source-rock reservoirs is hosted in organic matter and mineral pore space as well as in voids and microfractures. Recent work has shown that for source-rock reservoirs in the dry gas window, significant portions of methane (CH4), the main component of petroleum at elevated maturities, can be stored within fine (<5 nm) organic matter porosity. However, within reservo
Authors
Aaron M. Jubb, Leslie F. Ruppert, Tristan G. A. Youngs, Tom Headen, Justin E. Birdwell, Michael Cheshire, Martha (Rebecca) Stokes
Mapping ancient sedimentary organic matter molecular structure at nanoscales using optical photothermal infrared spectroscopy
Elucidating the molecular structure of sedimentary organic matter (SOM) is key to understanding petroleum generation processes, as well as ancient sedimentary environments. SOM structure is primarily controlled by biogenic source material (e.g., marine vs. terrigenous), depositional conditions, and subsurface thermal history. Additional factors, e.g., strain, may also impact the molecular structur
Authors
Aaron M. Jubb, Martha (Rebecca) Stokes, Ryan J. McAleer, Paul C. Hackley, Eoghan Dillion, Jing Qu
Relating systematic compositional variability to the textural occurrence of solid bitumen in shales
This study presents Raman spectroscopic data paired with scanning electron microscopy (SEM) images to assess solid bitumen composition as a function of solid bitumen texture and association with minerals. A series of hydrous pyrolysis experiments (1–103 days, 300–370 °C) using a low maturity (0.25% solid bitumen reflectance, BRo), high total organic carbon [(TOC), 14.0 wt%] New Albany Shale sample
Authors
Martha (Rebecca) Stokes, Brett J. Valentine, Aaron M. Jubb, Paul C. Hackley
*Disclaimer: Listing outside positions with professional scientific organizations on this Staff Profile are for informational purposes only and do not constitute an endorsement of those professional scientific organizations or their activities by the USGS, Department of the Interior, or U.S. Government