Foraminifera of the Monterey shale and Puente formation, Santa Ana Mountains and San Juan Capistrano area, California

Abstract

In the Santa Ana Mountains and San Juan Capistrano area, Orange County, Calif., thick sections of Miocene sedimentary rocks are exposed. '!'hey are assigned to the Monterey shale. of middle and late Miocene age and the Puente formation of late Miocene age. The area described is divided into four geographic units: the northern and central Santa Ana Mountains, the southwestern Santa Ana Mountains, the area east of Oso Creek (east flank of the Capistrano syncline), and the area west of Oso Creek (west flank of the Capistrano syncline). The faunal assembl•ages of each area are compared with those of the California Miocene stages proposed by Kleinpell (1938). In the Santa Ana Mountains, the Topanga formation (Relizian (?) stage) and the El l\1odeno volcanics (Luisian stage) are oyerlain Ull(:Onformably by the Puente formation (Mohnian stage). On the east flank of the Capistrano syncline, south of the El Toro Air Station, the •Topanga formation is overlain by the Monterey shale, which ranges in age from late Luisian at the base to l\fohnian at the top. To the west of Oso Creek, the Topanga formation is overlain by the Monterey shale which ranges in age from early Luisian at the base to late Luisian and Mohnian at the top. Changes in thicknesses of rocl\:s assigned to the Luisian •and Mohniah stages are due to unconformities and local depositional variations. No evidence was found to indicate that foraminiferal faunas assigned to the Mohnian stage grade laterally into faunas of the Luisian stage.

Eotaria citrica, sp. nov., a new stem otariid from the “Topanga” formation of Southern California

“…However, no specific details regarding the age assigned to that locality were given and the Monterey Fm. in this area ranges from mid Langhian through upper Tortonian (14.9–7.1 Ma; Smith, 1960 ; Blake, 1991 ; Barron & Isaacs, 2001 ). So it remains uncertain whether this represents a late Miocene or older record of Allodesmus, coeval and/or conspecific with those of the Altamira Shale.…”