Science Moab: Old Oceans, Oil and Orogeny

More than 65 million years ago, a sea route existed across North America, from what is now the Gulf of Mexico to what is now Alaska. Peter Flaig is a research scientist at the Department of Economic Geology in Austin, Texas, studying the geology of this seaway by examining sediments from the southwestern United States to Canada and Alaska. We spoke with Hulaig about the boundaries of this seaway, which includes part of what is now the Colorado Plateau.

Science Moab: Can you tell us a little bit about the Western Interior Seaway, the prehistoric sea that cuts across western North America?

Frag: [The Western Interior Seaway was] A sea route that crossed continents and eventually disappeared. It was several hundred meters deep, but not as deep as the continental shelf. There was sediment coming out of Sevier Orogeny. The Sevier orogen bends the lithosphere and creates this large inland basin along with water-filled continents. River and floodplain sediments enter this inland seaway as deltas and coastlines along this highly complex coastline that runs across North America. The sea route separated Laramidia and Appalachia. [Laramidia was a landmass that stretched from modern-day Alaska to Mexico. -ed.]

Science Moab: How have the Seaway’s shorelines and water levels changed over time?

Frag: There are sea level changes of tens to hundreds of meters. The coastline moved towards the center as the seaway narrowed and receded as the seaway rose, creating a stack of different sedimentary environments. You can also start with a very wide channel in .As seaways shrink, these coastlines move eastward [and in that location] Because the coastal plains formed over ancient shores, peat swamps and river systems are now tree-lined, and the dinosaurs that lived in those coastal plains now live. [that location would again] Return to more marine conditions.

Science Moab: The Mancos Shale represents one of the deepest parts of the basin, is that correct?

Frag: Think about the Mississippi Delta. Suppose you walk the actual aerial portion of the delta out onto the furthest delta front, the Gulf of Mexico. You will end up in hundreds of meters of water where all coarse-grained sediment such as sand is lost. It’s just depositing silt and mud. The Mancos Shale is the deeper part of the system, past all of the actual coarse-grained sediment input, and is only depositing very fine silt and mud. I record a lot of time.

Science Moab: Do Seaway deposits have economic value?

Frag: Seaway sediments are of great interest to the oil and gas industry because of the great outcrops. When people drill oil and gas reservoirs, they have a swiss cheese view of what is going on underground. Excavating is very expensive. Bookcliffe provides us with outcrops analogues of these underground reservoirs. They are not necessarily reservoirs. It’s possible, but it represents something you can’t see underground. What a good reservoir is and how it’s connected over long distances, Bookcliffe provides us with that ongoing exposure.

Science Moab: What made you want to study seaways in the first place?

Flaig: Well, the Department of Economic Geology was looking for someone to look at these outcrops as analogues of reservoir systems. He one of the best places to do that is Bookcliffe. So I initially started using these as outcrops analogues of people’s reservoirs around the world. I am also very interested in what kind of flora and fauna the Seaway deposits preserve, what they tell us about the evolution of the interior of North America, what natural things happened to this planet based on wax. And the decline of glaciers. What does it look like when no humans are around? We want to understand what we are doing to our planet that is causing sea level rise and temperature change.

Science Moab: What research are you passionate about with Seaway?

Frag: I am very interested in what happens to the deposit. It is very interesting to examine deposits and understand why they have such characteristics. These system features speak to the broader geometries of the shale-bearing subsurface. In Alaska, for example, many of these systems are submerged and have very active oil and gas reservoirs. I look at outcrops of these systems to understand how these properties change, to predict whether we’ll see the same thing underground, and to make predictions about what’s actually going on. I’m really interested in asking if it should be changed.

Science Moab is a nonprofit organization dedicated to engaging community members and visitors in the science happening in southeastern Utah and the Colorado Plateau. To learn more and listen to the rest of this interview, please visit: interview has been edited for clarity.

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