Subsidence of the Laguna Salada Basin, northeastern Baja California, Mexico, inferred from Milankovitch climatic changes

Abstract

Laguna Salada in northern Baja California, Mexico, is an active half-graben product of the trans-tensional tectonics of the Gulf of California. It is sensitive to changes in sediment supply from the Colorado River basin. We present a time series analysis of the upper 980 m of a gamma-ray log from a borehole drilled near the Laguna Salada fault. The power spectrum of the gamma-ray log resembles the spectrum of δ18O Pleistocene isotopic variations from ice cores and from the deep ocean, known to be strongly controlled by Milankovitch cycles. We correlate δ18O stages with silty and sandy intervals in the log. Downcore ages for the last 780 ky are constrained within ~10 kyr. We derive a simple time vs. depth calibration relation for the basin over this time interval. Estimated sedimentation rates at the drill site appear to be constant with a value of ~1.6 mm/yr. We propose that this subsidence rate is produced by the Laguna Salada fault.

Keywords

• Gulf of California extensional province
• Milankovitch cyclicity