SEPTEMBER 2025 LUNCHEON MEETING
CHRISTINE GRIFFITH
presents:
IMPACT OF CORDILLERAN TECTONICS ON
THE SAN MARCOS ARCH AND SABINE AREA UPLIFTS
IN THE NORTHERN GULF OF MEXICO BASIN
11:30 AM Wednesday, September 17, 2025
at Willow Brook Country Club
3205 W Erwin St.
Tyler, TX 75702
Cost: $25 if you RSVP
$30 at the door if you do NOT reserve
Abstract
The San Marcos Arch in Texas is a southeast-trending structural high that extends downdip from the Llano Uplift at the edge of the Paleozoic Laurentian continent. The arch was continually high from the Paleozoic to the present, but the greatest uplift and angular truncation occurred during the Late Cretaceous, Cenomanian to Campanian, ~96–80 Ma, based on subsurface correlations tied to nannofossil biostratigraphy. Thin sedimentary intervals and shallower water facies updip indicate that the San Marcos Arch and the Llano Uplift acted as a structural unit that formed an island or promontory in the Western Interior Seaway. Water circulation between the Western Interior Seaway and the Gulf of Mexico passed west of the San Marcos / Llano island before the Late Coniacian but shifted eastward ~87 Ma to pass primarily through the East Texas Basin. The Sabine uplift in East Texas/Louisiana was a north-south trending crustal fragment south of the Paleozoic Ouachita suture that subsided after the Jurassic. Like the San Marcos Arch, it experienced greatest uplift and angular truncation during the Late Cretaceous, ~96–90 Ma. The Sabine uplift formed the east flank of the Western Interior Seaway before subsiding ~87 Ma. Neither the San Marcos Arch and Sabine uplifts is associated with the formation of the Gulf of Mexico, as uplift occurred long after the extensional formation of the Gulf of Mexico and without large sediment loads to cause flexure. In addition, both features are at high angles to extensional features in the Gulf of Mexico. They have been interpreted as forebulges or folds associated with compression from the Mexican Cordillera, but the most profound unconformities over these uplifts formed before the maximum deformation of the Mexican Cordillera , 75-45Ma. The timing of uplift, ~100-80 Ma, is consistent with the initiation of significant contractional deformation in the Sevier fold-and-thrust belt, collision of terranes along the southwestern margin of North America and development of the southern portion of the Western Interior Seaway.
Biography
Christine Griffith worked for Shell Oil as petroleum geologist and team lead for exploration and development projects onshore and offshore United States, Nigeria, and Brazil. After retirement, she received her Ph.D.in Geology from Texas A&M University with a dissertation on the regional sequence stratigraphy of the Upper Cretaceous Austin Chalk in south and central Texas. Christine’s previous degrees were a BS in Geology from the University of Illinois and a MS in Geology from the University of Wisconsin. She is a longtime member of the AAPG and House of Delegates, a member of the Houston and South Texas Geological Societies, and a licensed professional geologist in Texas. She teaches classes in Introductory Geology and Petroleum Geology at Texas A&M University.