Department members Dan Chaney and Pete Kroehler traveled to north central Texas in October to excavate early Permian plant specimens for exhibit in the National Fossil Halls, which currently are undergoing renovation. They worked at a site where Bill DiMichele, Curator of Fossil Plants, and Dan had previously collected research specimens. This post combines Bill’s descriptions of the fossils and their scientific importance with Dan and Pete’s photos from the quarry.
The excavation site viewed from a nearby hill. A Humvee, lent by the landowner, was rugged enough to allow Dan and Pete to drive the rough terrain all the way to the site instead of having to walk in and out each day. Click photo to zoom.
The fossil locality where Dan and Pete collected fossils is called "Colwell Creek Pond." The rock there formed from sediments that settled in the bottom of a lake around 275 million years ago. The quality of fossil preservation is outstanding and unusual. Whole, large leaves are preserved in exquisite detail, including all their internal cell structure. Not only can we determine the kinds of plants that lived here, but we can study their natural relationships and interpret the environmental conditions under which they lived.
An example of the beautiful fossils found at the Colwell Creek Pond site. This is Compsopteris, a pteridosperm, or seed fern, which is an extinct plant type common during the Permian. Click photo to zoom.
When this deposit formed, the region was part of the ancient supercontinent Pangea, and located in the tropics. There were several major periods of polar glaciation during the Permian, and intervals of global warmth between them; it is in one of those warm periods that the Colwell Creek Pond plant community formed. The Colwell Creek Pond rocks themselves reveal a great deal about the ancient habitat, the climate under which it formed, and the ecological effects of climate change, which occurred during the approximately 2500 years it took for the deposit to form. Parallel studies of the deposit and of the early-Permian-age fossil soils surrounding it allow scientists to recreate this ancient landscape in great detail.
Comparison of the plants preserved in this deposit with those from others formed during older and younger glacial periods allows scientists to study the effects of global cooling and warming on ecosystem structure and diversity. This, of course, has direct relevance to modern concerns about ecological change in light of projected global warming.
Photos by Dan Chaney and Pete Kroehler.
Read Bill DiMichele’s earlier posts about Texas fieldwork.