INTERSECTION OF ECOLOGICAL AND TAPHONOMIC FACTORS IN THE PRESERVATION OF DISPARATE FAUNAS, INCLUDING SOFT-BODIED TAXA (SOME NEW OR NOT PREVIOUSLY RECOGNIZED), CLOSELY ASSOCIATED IN THE KINZERS FORMATION, EARLY CAMBRIAN OF S.E. PENNSYLVANIA

Special preservation of soft-bodied taxa or others with limited preservation potential has distracted attention from the fact that faunas of Konservat-Lagerstätten are often biased in other ways. The degree to which these biases reflect global taphonomic or other variables as opposed to local ecological circumstances is not fully resolved, especially in regard to early Cambrian faunas. Varied fossil-bearing facies of the Kinzers Formation provide an opportunity to assess patterns of preservation of taxa in different circumstances in the same geographic area, over a relatively short interval of time. Grainstones in the basal Emigsville Member (topmost Vintage Formation of some authors) deposited on a current-swept outer shelf or shoaling ramp yield a fauna dominated by small shelly taxa, brachiopods, chancelloriids and echinoderm ossicles. The overlying shale is lithologically variable on a fine scale. Here, Skinner (1997, 2005) recognized distinctive faunal/taphonomic assemblages: (1) shelly faunas in silty, formerly calcareous (leached) shale where brachiopods and echinoderms predominate; (2) rare concentrations of articulated echinoderms with associated shelly taxa; (3) faunas rich in trilobites, mostly disarticulated and fragmentary, with Salterella and varied shelly invertebrates; (4) occasional concentrations of trilobites, many of them articulated; (5) thin lagerstätten with lightly schlerotized arthropods and soft parts of worms, algae and other taxa, some exquisitely preserved. Recent discoveries include an Anomalocaris claw with spines significantly different from others so far known, excellent specimens of Emmonsaspis (Chordata), Atalotaenia (“worm”) and Odaria (Phyllocarida), and an assemblage of shells of Pelagiella (helcionellid or basal gastropod) with paired sets of chaetae. These lagerstätten are interbedded on a decimeter to meter scale with horizons in which shelly faunas predominate. Finally, in the Upper Member of the Kinzers, still within the Olenellus/Bonnia Zone, two different groups of trilobite taxa predominate in limestones composed largely of skeletal debris and much finer grained limestones. These observations document the close association in space and time of an Early Cambrian lagerstätte with a variety of continental shelf assemblages.