Sedimentology of the thacher limestone (lower devonian helderberg group), New York state-discussion

1993 ◽  
Vol 86 (3-4) ◽  
pp. 325-327
Author(s):  
Gerald M. Friedman
1999 ◽  
Vol 107 (6) ◽  
pp. 643-658 ◽  
Author(s):  
Nathaniel W. Diedrich ◽  
Bruce H. Wilkinson

2017 ◽  
Vol 53 ◽  
pp. 269-284
Author(s):  
Martin A. Becker ◽  
Rebecca B. Chamberlain ◽  
Harry M. Maisch ◽  
Alex Bartholomew ◽  
John A. Chamberlain

Glacial erratics belonging to the Rickard Hill facies (RHF) of the Saugerties Member of the Schoharie Formation (upper Emsian: Lower Devonian) occur scattered throughout the Piedmont of northern New Jersey and Lower Hudson Valley of New York. These RHF glacial erratics contain an assemblage of trilobites belonging to: Anchiopella anchiops, Burtonops cristatus, Calymene platys, Terataspis grandis, cf. Trypaulites sp. and cf. Coniproetus sp. This RHF glacial erratic trilobite assemblage consists predominately of disarticulated cephala and pygidia that were originally preserved as part of a localized, third-order eustatic sea level lag deposit in the Helderberg Mountains region of central New York State and subsequently transported in glacially plucked blocks by the Hudson-Champlain Lobe of the Laurentide Ice Sheet southward into New Jersey. Physical and chemical weathering during glacial erosion, transportation and deposition of the RHF glacial erratics has revealed some anatomical features of these trilobites in high detail along with other invertebrates. This unique sequence of weathering reveals additional characteristics that bear upon issues of bathymetric controls on upper Schoharie Formation lithology, trilobite faunal abundance and taphonomy during the upper Emsian (Lower Devonian) of eastern New York State.  


The oldest recorded terrestrial invertebrates are various small Diplopods (millepedes) from the Lower Old Red Sandstone of Britain which were probably preserved preferentially due to their robust calcified exoskeleton. While the myriapod affinities and terrestrial habits of the earliest, pre-Prídolí, claims are highly questionable, true diplopods are known from the latest Silurian (Stonehaven Group) and Lower Devonian of Scotland. In addition, a variety of enigmatic myriapod-like arthropods occur sporadically in the late Silurian-Lower Devonian freshwater facies of the M idland Valley of Scotland and Welsh Borderlands. Among these, the kampecarids ss. constitute a discrete group of short-bodied, diplopodous uniramian arthropods, possibly with myriapod affinities and aquatic habits. In contrast to the diversity of chelicerate groups represented in the later terrestrial invertebrate faunas of Rhynie, Aiken and Gilboa, the Middle to Upper Devonian fossil record of the Myriapoda is very sparse. While true diplopods are notably absent, a variety of fragmentary chilopods (centipedes) are now known from the Gilboa Fauna (Givetian) of New York State.


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