Latest Paleocene lithologic and biotic events in neritic deposits of southwestern New Jersey

Abstract

In the southwestern New Jersey Coastal Plain, four drill holes contain continuous neritic sedimentation across the Paleocene/Eocene boundary (calcareous nannofossil Zone NP 9/NP 10 boundary). Significant lithologic and biotic changes occur in these strata near the top of the Paleocene. Global warming, increased precipitation, and other oceanographic and climatic events that have been recognized in high‐latitude, deep‐oceanic deposits of the latest Paleocene also influenced mid‐latitude, shallow‐marine, and terrestrial environments of the western North Atlantic. The diverse, well‐preserved calcareous nannofossil flora that is present throughout the entire New Jersey boundary section accurately places these events within the uppermost part of the upper Paleocene Zone NP 9. Several rapid but gradational changes occur within a 1.1‐m interval near the top of Zone NP 9. The changes include (1) a change in lithology from glauconitic quartz sand to clay, (2) a change in clay mineral suites from illite/smectite‐dominated to kaolinite‐dominated, (3) a change in benthic foraminiferal assemblages to a lower diversity fauna suggestive of low‐oxygen environments, (4) a significant increase in planktonic foraminiferal abundance, and (5) an increased species turnover rate in marine calcareous nannofossils. Pollen was sparse in the New Jersey drill holes, but terrestrial sporomorph species in Virginia exhibit increased turnover rates at a correlative level. Foraminiferal assemblages and lithology indicate that relative sea level rose in New Jersey at the same time as these late Paleocene events occurred in late Biochron NP 9. The higher sea levels influenced sediment type and absolute abundance of planktonic foraminifers in the deposits. Above the initial increase of kaolinite in the upper part of Zone NP 9, the kaolinite percentage continues to increase, and the maximum kaolinite value occurs in the uppermost part of Zone NP 9. There are few changes in either the sediments or the biota precisely at the Zone NP 9/NP 10 boundary in New Jersey. The clay‐rich deposits with a high kaolinite clay mineral suite, the lowered diversity benthic foraminiferal assemblages, the abundant planktonic foraminiferal specimens, and the calcareous nannofossil assemblages continued essentially unchanged into the earliest Eocene Zone NP 10. Within the lower part of Zone NP 10, the kaolinite percentage decreased to very low values.

Drilling disturbance and constraints on the onset of the Paleocene–Eocene boundary carbon isotope excursion in New Jersey

“…For example, it would have caused sudden and substantial acidification of the upper layers of the ocean in contact with the atmosphere, whereas a slower rate of carbon release would have caused a less sharp acidification response because shallow and surface waters are continually mixed into the much larger deep ocean reservoir on timescales of the circulation of the deep ocean, i.e., millennia Hönisch et al, 2012). There was no mass extinction of calcareous plankton Zachos et al, , 2007Bown and Pearson, 2009;Self-Trail et al, 2012) or shallow-water smaller benthic foraminifera (Gibson et al, 1993;Stassen et al, 2012) at the Paleocene-Eocene boundary; hence, a quasiinstantaneous onset to the event would imply that these organisms adapted to rapid acidification. More generally, the lack of a global mass extinction on land and in the oceans (except among deep-sea benthic foraminifera) would indicate unexpected, and perhaps reassuring, resilience of life to profound and abrupt global warming (e.g., Thomas, 2004;McInerney and Wing, 2011).…”

Plant and mammal diversity in the Paleocene to early Eocene of the Bighorn Basin

“…The Paleocene/Eocene boundary interval increasingly is being recognized as an interval of rapid change in global ocean circulation and global climatic conditions (Rea et al, 1990;Kennett and Stott, 1991;Koch et al, 1992;Pak and Miller, 1992;Gibson et al, 1993). Oxygen isotope records from planktonic and benthic foraminifera at many DSDP sites indicate a strong warming trend beginning in the latest Paleocene and continuing into the latter part of the early Eocene (Shackleton et al, 1984;Miller et al, 1987).…”

Eustatic variations during the Paleocene‐Eocene greenhouse world

“…Cores from both sites contain upper Paleocene-lower Eocene sediments deposited on a broad continental shelf (Figure 2) [Gibson et al, 1993], perhaps as far south as $27°N [Kopp et al, 2007]. Average paleowater depth at Bass River has been estimated at $150 m, on the basis of benthic foraminifer assemblages [van Sickel et al, 2004].…”