Biostratigraphy and paleoecology of the Upper Cretaceous-Lower Tertiary sequence in the New Jersey coastal plain

The New Jersey Inner Coastal Plain is underlain by a Campanian (Upper Cretaceous) to Thanetian (Paleocene) stratigraphic sequence containing fossil assemblages from before, during and after the K/T boundary mass extinction event. The lithostratigraphic framework and the microfossil zonation of these faunal changes is reviewed. Microstratigraphic analysis of the sequence reveals that dominant marine organisms of the Upper Cretaceous such as ammonites and oysters are selectively extirpated at the K/T boundary, while those organisms with a non-planktotrophic reproductive strategy were the surviving marine invertebrates. Comparative taphonomy is applied to two fossil assemblages in the sequence to demonstrate the differences between reworked taphocoenoses of nearshore and estuarine environments and those of deeper-water taphocoenoses. A complete synonymy for all New Jersey K/T vertebrate taxa is presented, and all valid taxa are plotted on a stratigraphic range chart with guild/niche information about each group. Two geochemical investigations are evaluated for their bearing on the question of catastrophic extinction processes caused by asteroid impact. It is concluded that the methodology of comparative taphonomy can be a useful tool in determining the difference between transported, reworked fossil assemblages produced by physical events like storms, and those assemblages which accumulated in deeper-water settings where modification was primarily biological. The mass extinction event as recorded in this sequence was gradual, but exacerbated by a sharper mass mortality at the end of the Cretaceous; diversity rebound to pre-K/T levels did not occur until the Thanetian. Plankton crash most drastically affected those organisms with a planktotrophic larval stage. The drop in plankton biomass was mediated upward in the food chain to duraphagous predators (and to those who ate them) by way of the die-off in previously abundant Cretaceous mollusks. The iridiuim data are ambiguous, and toxic metal data lend no support to the Strangelove Ocean hypothesis. Finally, it would appear that a combination of gradual climatic changes coupled with a sudden event like a bolide impact caused a protracted period of mass extinctions with suppression of full biomass productivity lasting well into the Paleocene.