Paleontological resource survey: Amistad National Recreational Area

Visaggi, Christy; Johnson, Jack; Johnson, Angel; Kenworthy, Jason; Santucci, Vincent

Amistad National Recreation Area (AMIS) is one of at least 213 National Park Service units with paleontological resources. Despite a rich and abundant fossil record comprising vertebrates, invertebrates, plants, microfossils, and trace fossils, paleontological resources remain relatively unexplored at Amistad NRA. The purpose of this survey was to obtain adequate baseline paleontological resource data for the park and offer recommendations for the future management of AMIS paleontological resources.This report was compiled through extensive fieldwork, literature review, and interviews with park staff. Fieldwork completed primarily in March 2006 covered 25 in-park localities and 11 additional exposures in the AMIS vicinity. The investigation focused mainly on Cretaceous deposits as limited records exist for these fossils on National Park Service land. Numerous publications detail Quaternary fauna and flora uncovered during archeological salvage operations prior to the construction of Amistad Dam.The Mesozoic Era is represented by Lower and Upper Cretaceous units inside the park including the Salmon Peak Limestone, Devils River Limestone, Del Rio Clay, Buda Limestone, and Boquillas Formation. The most common marine invertebrates encompass rudistid bivalves, Ilymatogyra oysters, Nerinea gastropods, and Cribratina forams. Fragmentary echinoids, ammonoids, scallops, bryozoans, burrows, and borings are also found in these deposits. The most interesting fossils at the park are likely rudistid reefs, quite distinct from modern reefs which are composed primarily of coral, as well as ammonoids, as both of these organisms went extinct at the end of the Mesozoic.The Cenozoic Era is represented by assemblages preserved in rock shelters formerly utilized by indigenous people of the Chihuahuan Desert. Plant remains, pollen, and vertebrates are commonly preserved in this cultural context; mollusks, arthropods, and middens are additionally noted in the literature at select localities. Paleontological resources of the Quaternary are often utilized in studying the diet and behavior of ancient cultures as well as changes in the biota and climate of southwest Texas.There are several repositories for AMIS paleontological collections. Limited fossils recovered inside park boundaries as a result of this investigation were accessioned at AMIS headquarters; records for pre-existing fossils housed at the park were updated. Although current interpretative efforts mainly focus on cultural resources, opportunities for increased education and awareness of paleontological resources at the park are plentiful. Developing programs in cooperation with the neighboring Shumla School is suggested as a shared interest exists in learning more about the paleontology of the region. Heightened protection of in situ paleontological resources at the park is needed, particularly for six localities to be registered as significant with the NPS. Additional surveys set up through an inventory and monitoring program are highly recommended for Amistad NRA as well. Threats such as theft, erosion, and development must be mitigated as these resources are non-renewable and are important for scientific research. Documentation of fossil localities, inventory of AMIS paleontological resources, improved fossil collections, and various recommendations resulting from this project impart a strong basis for the future of paleontology at Amistad National Recreation Area.

Paleontological resource survey: Amistad National Recreational Area

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