WIPS Invitation to DPS

For all members of DPS

Please join us via Zoom on Monday, February 1 at 8 PM Central Standard Time for a presentation by John McLeod for the Western Interior Paleontological Society (WIPS)

When Reefs and Rivers Collide: An Unusual Fossil Biota from the Pennsylvanian Of North Texas

Intermittent outcrops around Lake Bridgeport in north Texas can afford exceptional collecting of a diverse and well preserved fossil biota.  From 2011 until mid-2015, the dam-impounded lake dropped to record-low water levels due to a combination of extended drought and growing consumption demand by the city of Fort Worth.  During this four-year window, extensive exposure of long-submergent formations afforded detailed study of the geology and fossil content of formerly inaccessible localities. Owing to its unique paleogeographic setting and favorable conditions for preservation, the assemblage is unusual in containing a diverse mixture of terrestrial and marine environments, plants, large invertebrates, vertebrates, trace fossils, sedimentary structures and even pseudofossils.

The greater Pennsylvanian seaway of the Lake Bridgeport area was closed to the north by the emergent Wichita Mountains in southern Oklahoma and received additional sandy sediment from the Perrin river and delta that originated from the rising Ouachita Mountains to the southeast.  Although much of the shallow muddy bottom around the deltas was well-oxygenated, at least two thin intervals of less-oxic sediments preserve nodules containing an unusual fauna.  A sea level rise eventually drowned the muddy substrate and deltas with algal limestone but some of the predecessor benthic and pelagic species survived and even prospered in and around the new environment.  A massive accumulation of fossils and associated sedimentary structures from Lake Bridgeport outcrops collected over a 30-year period has yielded a number of new or unique specimens