Origin and history of upper Pleistocene marine terraces, San Diego, California

Abstract

Geomorphic, structural, paleontologic, and stratigraphic analysis of features of emergent marine terraces have been used to reconstruct part of the late Pleistocene paleoenvironmental, paleogeographic, and tectonic history of the San Diego area. The Nestor terrace abrasion platform was cut 120,000 yr B.P. during a marine stillstand 6 ± 4 m above present sea level. Fossil marine invertebrates on this platform reflect slightly higher than present shallow-water marine temperatures, consistent with the slightly higher level of the sea and smaller volume of glacial ice. The 105,000-yr B.P. stillstand 12 ± 3 m lower than present sea level may be recorded in a single very small unfossiliferous terrace remnant. The Bird Rock terrace abrasion platform was cut 80,000 yr B.P. during a stillstand 14 ± 2 m lower than present sea level. Fossil marine invertebrates on this platform reflect slightly lower than present shallow-water marine temperatures, consistent with the slightly lower level of the sea and larger volume of glacial ice. General, rather uniform tectonic elevation of the entire San Diego coastal area has amounted to 19 to 24 m during the past 80,000 yr for a rate of uplift of 24 to 30 cm per thousand years. Just south of the Rose Canyon fault, the Nestor platform was elevated tectonically by approximately 23 m between 120,000 and 80,000 yr B.P. and another 31 m during the subsequent 80,000 yr to a total of 54 m in 120,000 yr, or 45 cm per thousand years.