INSIGHTS FROM 'TEXAS THROUGH TIME': FOCUS ON WEST TEXAS
EWING, Thomas E., Bureau of Economic Geology, University of Texas at Austin, Austin, TX; and Frontera Exploration Consultants, San Antonio TX
In June 2013 I began to put together a summary volume on the geology of Texas as geologists currently understand it, to be designed for general audiences. At present, the draft is completed and we are in review and editing/compositing stage; anticipated printing date is September, 2015. The book is fully illustrated in color, and around 300-340 pages long. It includes a comprehensive series of time-stratigraphic charts and an atlas of paleogeography and other features.
To write such a summary involved summarizing and synthesizing hundreds of geological reports and articles. That has led to some interesting new insights, a few of which follow:
Precambrian history is long and complex, we need more subsurface samples! The biggest question is the 'juvenile crust' section of the Southern Granite-Rhyolite province, how it gets added and how it's reworked into the Llano Orogen.
Latest Precambrian-Middle Cambrian rifting includes activity on the Devils River trend as far as Van Horn. Interestingly, Cambrian and Ellenburger isopachs don't show subsidence into that area, but instead towards San Antonio.
The story of rifted and displaced terranes south of the craton is newly considered and revised. One terrane (south of the former Marathon Basin, south of the Devils River) was sheared off to form 'Cuyania' in South America in mid-late Ordovician. It's possible that Sabinia (the Sabine Block) is also a part of North America and not exotic - but we need crazy deep drilling to be sure!
Ouachita-Marathon deformation is a 'soft docking' not a high-impact continental collision. It doesn't seem to explain the Late Paleozoic uplifts and basins, which are more consistent with SW-NE compression and related strike-slip.
The project also includes a website (now in beta), which will be part of the BEG website. It will include statewide information; some material from the book; and a series of 70-plus 'Great Places to View Texas Geology'. These are miniature field trip guides to highlight publicly accessible places to be wowed by Texas rocks and landscapes. Each site includes a nontechnical discussion of what you see, why it's important; a gallery of photographs; and a few references and websites for more information.
In West Texas these sites include: the Guadalupe Mountains (4 sites), Balmorhea/Davis Front, Marathon Basin, Odessa Meteor Crater, Big Spring, Iraan-Fort Lancaster, and Langtry-Pecos Canyonlands - plus some 11 sites in the Trans-Pecos mountains. In Northwest Texas, we add: Muleshoe Depression, Blanco Canyon, Caprock Canyons, Palo Duro, and Lake Meredith area.