Katahdin Woods and Waters National Monument: Paleontological resource inventory (sensitive version)

Tweet, Justin; Santucci, Vincent; Ashton, Isabel

doi:10.36967/2293971

Katahdin Woods and Waters National Monument (KAWW) in northern Maine has a paleontological record documenting approximately half of the Paleozoic, from the Cambrian into the Early Devonian, a span of time from approximately 539 to 407 million years ago. Paleontological resources were recognized as a significant feature of the monument upon its establishment in 2016. Remoteness, complex geologic structures, and copious surficial cover have hindered the study of paleontology in northern Maine. Therefore, outcrops in KAWW and its surrounding area are scientifically important in this region. The first report of fossils within what is now KAWW was made in 1838, by C. T. Jackson. Other brief reports were made in succeeding decades; the most detailed can be found in the papers published by Robert Neuman and Douglas Rankin from the 1960s to the 1980s. These two geologists incorporated fossils into their projects to provide information on topics such as the relative ages of rock units and paleogeography. The many brief reports over the decades have given a wide-ranging but fragmented picture of the paleontological resources of what is now KAWW. The geological story told by the rocks of KAWW is of a series of collisions involving eastern North America and smaller crustal fragments, each contributing to what is now the eastern margin of the continent and to the formation of the Appalachians. The events were punctuated by volcanic eruptions and other igneous activity, including the supervolcano that produced the Katahdin Granite and Traveler Rhyolite. The bedrock geology of KAWW is incompletely understood because of extensive surficial cover, complex faulting, and other factors, but more than a dozen rock units have been recognized within the monument. Among these are sedimentary rocks, metamorphosed sedimentary rocks, extrusive igneous rocks, and intrusive igneous rocks. Many of the geologic units of KAWW are either unnamed or informally named units, so it is likely that future work will lead to revision of the geologic nomenclature. Fossils have been found in the great majority of the sedimentary rocks within KAWW, spanning the Cambrian, Ordovician, Silurian, and Early Devonian. The sedimentary formations and their fossils are marine in origin. Most of the described fossils are either corals or brachiopods (shelled animals that outwardly resemble clams and other bivalve mollusks). Crinoid columnals are common in some fossiliferous units. At least four external repositories hold fossils collected from sites within KAWW before the monument was established: Eberhard Karls University of Tübingen, the National Museum of Natural History, the New York State Museum, and the Peabody Museum of Natural History. Among the fossils found at localities now within the monument are type specimens for four fossil species. Two other fossil species are based on specimens from localities potentially within the monument but with imprecise geographic information. The use of rivers as boundaries, particularly the East Branch of the Penobscot, complicates research of historical localities because past investigators frequently did not state on which side of the river a locality was found. However, rock units are usually exposed on both sides of the East Branch, so it is extremely likely that investigation would show that both sides have the same kinds of fossils.