The Green River from Trapper's Point. (Tom Rea)

JACKSON HOLE, WYO – How did Wyoming’s dramatic scenery, consisting of high mountains with intervening deep basins form? The answer to this question has been debated for over a century, and geologists are still working to provide answers.

Wyoming State Geological Survey geologist Ranie Lynds will explore and explain some of the recent data that sheds additional light on the formation of the scenery we see and love across Wyoming. Her talk is titled: “Unraveling the Geologic History of the Greater Green River Basin in Wyoming.”

The Green River at Seedskadee National Wildlife Refuge. (USFWS)

During the Late Cretaceous, Wyoming was part of an epicontinental seaway that extended from Canada to Mexico, otherwise known as the Western Interior Seaway (WIS). The WIS was a low spot in the North American continent that formed from mountain building and crustal loading of the Wyoming fold-and-thrust belt to the west, an event generally known as the Sevier orogeny.

Greater Green River Basin map

At some point in the Late Cretaceous, the western interior foreland basin was segmented into a series of intermontane basins by basement-cored uplifts that are today’s mountain ranges in an event known as the Laramide orogeny. The timing of the Laramide orogeny, and its impacts on the east-flowing drainage systems from the Sevier hinterland, has been the subject of research and argument for more than a century.

This talk will address new age data obtained from zircons preserved in outcrop samples collected from Wyoming’s Great Divide and Hanna basins. Although zircon is a mineral that forms during crystallization of magma, it is commonly found in sedimentary strata derived from magmatic-sourced igneous rocks. This dataset suggests at least two episodes of Laramide deformation in the Late Cretaceous through Paleocene strata, beginning at about 79 million years ago.

Constraining the timing of evolution of the Rocky Mountain region is key to understanding how and why continents deform. Some of the most prolific hydrocarbon-bearing formations were deposited during this time, and the ability to predict reservoir facies and distribution is important to Wyoming’s economy.

About Ranie Lynds

Ranie Lynds

Lynds began managing the WSGS Energy and Minerals Resources Division in late 2017. She has a BS in geology and an MS in geophysics from Stanford University and a PhD from the University of Wyoming where she specialized in fluvial sedimentology. Ranie has worked on coal bed natural gas drill rigs in Colorado’s San Juan Basin, dabbled in Utah’s uranium industry, and spent several years studying geologic carbon sequestration in Wyoming’s basins.

Since joining the WSGS in 2012, she has focused primarily on oil and gas research, delving into the details of not-so-well documented hydrocarbon systems throughout the state and participating heavily in the WSGS’ STATEMAP program. Ranie spends most of her free time trail running, mountain biking, and resurrecting some of Laramie’s historic homes.

Teton County Library Auditorium, Tuesday, October 2 at 6pm.