Taphonomy of lacustrine shoreline fish-part conglomerates in the Late Triassic age Lockatong Formation (Collegeville, Pennsylvania, USA): Toward the recognition of catastrophic fish kills in the rock record

• Published in: Palaeogeography, palaeoclimatology, palaeoecology Vol. 313; pp. 234 - 245
• Main Authors: Malenda, H. Fitzgerald, Simpson, Edward L., Szajna, Michael J., Fillmore, David L., Hartline, Brian W., Heness, Elizabeth A., Kraal, Erin R., Wilk, Jewels L.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 2012
• Subjects: Fish taphonomy; Freshwater; Lockatong Formation; Newark basin; Triassic; USA, Pennsylvania; INE, USA, California; USA, California, Salton Sea; Newark basin; Triassic; Fish taphonomy; Lockatong Formation
• ISSN: 0031-0182; 1872-616X
• DOI: 10.1016/j.palaeo.2011.11.022

Fish parts, bones and scale elements, preserved in sandstones and conglomerates characterize an uncommon type of lacustrine strandline setting identified in the Triassic Lockatong Formation of the Newark Supergroup. The Triassic fish-part sandstones and conglomerates are composed of disarticulated skeletal remains and formed during the lake expansion phase. Diverse mudstone-clast types derived from the underlying lowstand playa deposits integrated into the younger transgressive shoreline sequence that contains disarticulated fish parts. We propose that the Salton Sea, California, USA is a modern hypersaline lacustrine environmental analog for the deposition of fish remains. On the Salton Sea, high-wind events cause mass fish kills forming a modern shoreline dominated by barnacles and fish remains. Using modern day observations from fish kills in the Salton Sea, California, USA, we suggest that the following taphonomic scenario: mass kills of Triassic fish species took place during deposition of the lacustrine Lockatong Formation. High wind events caused overturning of the lake waters either depleting oxygen or toxically poisoning the fish. After death, bacterial decomposition bloated the fish by generated gas in tissues causing the fish carcasses to float. The decomposing fish carcasses were driven shoreward by wind and wave action and deposited on the shoreline and possibly scavenged by phytosaurs. Following soft tissue decay, the disarticulated remains were reworked into normally graded beds composed of intraclasts and fish-part elements. The intermixing of intraformational clasts and fish parts reflects the impact of storms on the lacustrine shoreline during the expansion phase of the Van Houten cycle, short period Milankovich frequency cycles that consist of three recorded phases of lake rise to fall recorded in various facies stackings. ► A rare type of lacustrine strandline setting is identified in the Triassic. ► A deposit composed of disarticulated fish skeletal. ► Observations from fish kills in the Salton Sea, California, USA, are used. ► High wind events that caused overturning of the eutrophic Triassic lake bottom. ► Decomposing fish carcasses that were reworked into shoreline deposits.