ABSTRACT: Sedimentological Constraints on Tectonic Models for the Tertiary of the Los Angeles Basin Area
Charles L. Lane
The Santa Monica and Santa Ana Mountains (northwest and southeast of the Los Angeles basin, respectively) have been sampled with respect to sandstone, conglomerate, and paleocurrent data. Data collection focused on the Tertiary section from both ranges; provenance and paleocurrent transport directions were determined in order to attempt constraint on paleomagnetic translation and rotation models for the Tertiary of southern California.
Discriminant analysis indicates no significant difference between detrital modes for sandstones from the Santa Ana and Santa Monica Mountains. Sandstones from both mountain ranges are derived from a dissected magmatic arc. Conglomerate clast populations are high in volcanic clasts (unlike the sandstone populations) and indicate a provenance different than that for sandstones. However, conglomerate modes are essentially the same for both mountain ranges.
Similarity of detrital modes for sandstones and conglomerates from both mountain ranges indicates a close geographic proximity throughout the Tertiary and constrains paleomagnetic models that postulate long-distance translation of the Santa Monica Mountains during that time frame. Similarity of conglomerate clast types from both mountain ranges and the younging counterclockwise rotation of paleocurrent vectors for units in the Santa Monica Mountains are consistant with rotational paleomagnetic models for the Los Angeles basin area.
AAPG Search and Discovery Article #90097©1990 Fifth Circum-Pacific Energy and Mineral Resources Conference, Honolulu, Hawaii, July 29-August 3, 1990