23 Paleontology (Posters)

Tuesday, 10 April 2001
8:00 AM - 12:00 PM

DEADMAN ISLAND REVISITED: THE QUATERNARY OF THE LOS ANGELES BASIN BASED ON MOLLUSCAN FAUNAS

Paper number: 23-7
Program: THEME SESSIONS
Time: 8:00 AM – 12:00 PM

Authors

Abstract

Deadman Island in San Pedro Harbor was the type locality for the upper and lower San Pedro Series until its destruction in 1928 during enlargement of the Long Beach/San Pedro Harbors. Early work on the Island showed eight fossiliferous horizons (zones). Zones 1 to 6 were attributed to the Santa Barbara Formation and later to the Timms Point Silt. Zone 1 contains Calyptogena gibbera Crickmay, which is known only from Deadman Island, the Niguel Formation, and the Towsley Formation. The Niguel and Towsley formations are both late Pliocene in age, suggesting a similar age for Zone 1 on Deadman Island. Fossils from Zones 2-6 suggest deposition in water temperatures cooler than present, and at water depths between 50 and 100 m. Zone 5 contains the coolest and deepest fauna. The fauna and sediments from Zones 2-6 suggest correlation with the Timms Point Formation of middle Pleistocene age.

Reworking seems to be a major problem in the upper zones (7 and 8) on Deadman Island. Fossils from Zone 7 (lower San Pedro series) suggest water temperatures similar to today, and deposition in water between 25 and 30 m deep, possibly deeper, on an open coast. Both northern and southern extra-limital taxa are present, but it is not clear which are autochthonous or allochthonous. Amino acid data suggest the southern extra-limital taxa are autochthonous, and correlate with oxygen-isotope Stage 5e. Fossils from Zone 8 (upper San Pedro series) also suggest water temperatures similar to today, and deposition in water depths between 5 and 30 m on an open coast. Both northern and southern extra-limital taxa are again present. The amino acid data suggest the southern extra-limital taxa are probably reworked and zone 8 correlates with oxygen-isotope Stage 5a.