Online Lunch Talk: Alex Zumberge

Speaker: Alex Zumberge Nov. 4, 2020 | 12:00 pm - 1:00 pm

FREE! MEMBERS ONLY

Geochemical Correlation of Late Mississippian-Sourced Crude Oils from the Western USA

By John B. Curtis, John E. Zumberge and J. Alex Zumberge; GeoMark Research, Houston TX

Some twenty-five million years after the deposition of the renowned Late Devonian/Early Mississippian black shales across North America, Middle to Late Mississippian sediments also generated oils in western North America. These areas include Central Montana, western North Dakota in the Williston Basin, the Las Animas Arch area of eastern Colorado, the Arkoma, Ft. Worth and Permian basins of Oklahoma and Texas, as well as Railroad Valley of Nevada and the Thrust Belt in Central Utah. Using sterane and terpane biomarkers and carbon isotopes, these Mississippian-sourced oils indicate a wide range of source rock depositional environments. The Heath Formation of Central Montana generated oils with evaporitic/carbonate biomarker features including both photic zone euxinia (PZE) and stratified water column indications. However, workers have been challenged to correlate these type-area outcrop units of Central Montana to the sub-surface of the Williston Basin of western North Dakota (Bottjer et al., 2019). The Heath-sourced oils in the Williston are strikingly different than those of Central Montana. Although they both have PZE, Williston Heath/Amsden oils lack the evaporitic signatures seen in the Heath/Amsden oils of Central Montana, have very low sterane to hopane ratios (i.e., low algae/bacteria relative abundances), and most surprisingly, have extremely high C28/C29 regular sterane ratios. Prasinophytes are a unique class of green algae that produce C28 sterols as major steroid constituents and thrive in oxygen depleted environments that are unfavorable for other planktonic primary producers (Schwark and Empt 2006). High C28/C29 sterane values have only been measured in oils from Late Cretaceous » CONTINUED ON PAGE 24

ALEX ZUMBERGE has extensive lab experience in oil and rock extract analyses with emphasis on correlation tools like bulk organic properties, lipid biomarkers and carbon isotopes. He has over eight years’ experience in a lab environment doing experiments himself as well as overseeing general sample/project flow through each analysis phase. Alex recently finished his PhD in Organic Geochemistry at the University of California – Riverside where he specialized on sterane/hopane relationships through time from the Precambrian to the present. Additionally, Alex has experience with traditional analytical techniques (LC, GC, GC-MS, GC-MS/MS) as well as new analytical approaches that allow access to the kerogen-bound biomarker pool within rock extracts via Hydrogen Pyrolysis, HyPy. Currently, Alex is the Director of Analytical Services at GeoMark Research and manages oil technical service projects as well as the new GRI+ rock lab.