From Shield to Sea: Geological Field Trips From the 2011 Joint Meeting of the GSA
Late Devonian paleontology and paleoenvironments at Red Hill and other fossil sites in the Catskill Formation of north-central Pennsylvania
Edward B. Daeschler and Walter L. Cressler III
The stratified red beds of the Catskill Formation are conspicuous in road cut exposures on the Allegheny Plateau of north-central Pennsylvania. These sites have been central to recent investigations into the nature of Late Devonian continental ecosystems. By the Late Devonian, forests were widespread within seasonally well-watered depositional basins and the spread of plants on land from the late Silurian through the Devonian set the stage for the radiation of animals in both freshwater and terrestrial settings. A diverse assemblage of flora and fauna has been recovered from the Catskill Formation including progymnosperms, lycopsids, spermatophytes, zygopterid and stauripterid ferns, barinophytes, invertebrates, and invertebrate traces, and vertebrates such as placoderms, acanthodians, chondrichthyans, actinopterygians, and a variety of sarcopterygians including early tetrapods. Since the early 1990s, highway construction projects along the Route 15 (Interstate 99) have provided a new opportunity for exploration of the Catskill Formation in Lycoming and Tioga counties. The fauna along Route 15 are dominated by Bothriolepis sp. and Holoptychius sp. and also include Sauripterus taylori and an assortment of other interesting records. The most productive Catskill site, and the source of early tetrapod remains, is Red Hill in Clinton County. Red Hill presents a diverse and unique flora and fauna that is distinct from Route 15 sites, and also provides a spectacular section of the alluvial plain deposits of the Duncannon Member of the Catskill Formation.
Overview
-earliest paleontological investigations - 1830s and 1840s
-James Hall described pectoral fin of the rhizodontid sacropterygian Sauripterus taylori
-Charles Lyell passed through Blossburg in 1840 examined Catskill Formation
-additional fossil material was described by Leidy, Newberry, and Eastmann
-recent paleobiological investigations - 1993 ANSP
-Clinton, Lycoming, and Tioga Counties
-paleontological investigations have been closely linked with the construction of the railway system and the highway system
-Catskill Formation - composed of sand, silt, and mud deposited in a series of prograding deltas
-Catskill Delta Complex.
-clastic wedge derived from the middle to late Devonian Acadian Mountains shedding sediment westward and northwestward toward a shallow epicontinental sea in the foreland basin of the orogenic zone.
-studies have focused on the deltaic and alluvial plain facies at the top of the formation.
-Late Devonian
-time of major transitions in flora, fauna, and geobiological system
-forests were widespread within the seasonally well-watered depositional basins.
-dominant tree was the progymnosperm Archaeopteris (18 feet tall)
-first plant known with a bifacial cambium as in modern wood
-reproduced through spores
-Seed plants are first known from the Late Devonian (Rothwell, et al., 1989)
-opportunistic seed plants, growing in areas disturbed by fire, took advantage of the destruction of the widespread fern Rhacophyton (Cressler, 2006; Cressler et al., 2010a).
-Lycopsids were important swamp plants in the Late Devonian
-attaining the stature of small trees
-contributing to the thin coal seams known from the time
-small lycopsids are the precursors of the immense lycopsids that were the primary components of the Carboniferous coal swamps (Cressler and Pfefferkorn).
- Increased stature of the plants in the Late Devonian was accompanied by a concomitant increase in root zone depth, which led to increased paleosol development (Driese and Mora, 1993).
-Spread of plants on land - set the stage for the radiation of animals in both freshwater and terrestrial settings.
-large, suspension-feeding bivalves, Archandon catskillensis
- recorded sporadically from Catskill formation
-fossil terrestrial arthropods (first known from the Silurian)
-millipedes (Wilson et al., 2005)
-scorpions and a trigonotarbid arachnid (Shear, 2000)
-no evidence of herbivory of living plant tissue during the Late Devonian.
-increased contribution of organic detritus by land plants to terrestrial and freshwater ecosystems during this time provided the primary productivity for these increasingly complex and diverse ecosystems
-Vertebrate assemblage
-placoderms, acanthodians, chondrichthyans, actinopterygians, range of sacropterygians
-at least three species of tetrapods
-two distinct faunas characterize the vertebrates from the Catskill Formation
-Holoptychius sp.
-Bothriolepis
-these appear to be organisms mainly restricted to lower alluvial plain - deltaic habitats.
-Some of the sarcopterygians (particularly the tetrapods) are lineages adapted for mobility in stream channels and shallow obstructed waters, a habitat that the well-vegetated alluvial plains of the Catskill Delta Complex seem to have provided.
Day 1
Road Log
Stop 1. Powys Curve
-fauna is dominated by the antiarch placoderm Bothriolepis sp.
The “Bothriolepis Problem”
Thomson and Thomas (2001) and Weems (2004) reviewed the taxonomic status of Bothriolepis from the Catskill Formation.
-it is clear from these papers that the diagnosis of species-level features in Bothriolepis from the Catskill Formation is a microcosm of the issues concerning species-level taxonomy of this cosmopolitan Late Devonian genus more broadly.
-Bothriolepis material from the Catskill Formation was first described by Leidy (1856) as Stenacanthus nitidus based on a distal portion of the pectoral appendage
