. Bulletins of American paleontology. Baja California Stratigraphy: Carreno and Smith 69 part of tlie San Felipe quadrangle were presented by Boehni ( l'^)S2). The thickness of the marine section is estimated as 100 m. San Felipe Diatoiiiite Meiuher. Late Mioeene-Early Plioeene.—Boehm's lower member was described from exposures along the eastern side of the southern Sierra San Felipe. The unit is more than 30 m thick and contains Late Miocene, middle bathyal diatoms, silicoflagellates, radiolarians. and deep-water tbramin- ifers that suggest marine deposition in the embayment began at —
. Bulletins of American paleontology. Baja California Stratigraphy: Carreno and Smith 69 part of tlie San Felipe quadrangle were presented by Boehni ( l'^)S2). The thickness of the marine section is estimated as 100 m. San Felipe Diatoiiiite Meiuher. Late Mioeene-Early Plioeene.—Boehm's lower member was described from exposures along the eastern side of the southern Sierra San Felipe. The unit is more than 30 m thick and contains Late Miocene, middle bathyal diatoms, silicoflagellates, radiolarians. and deep-water tbramin- ifers that suggest marine deposition in the embayment began at — Ma. Most of the microfossils support a Late Miocene age. but there are exceptions. The ra- diolarian Didymoeynis liiii^hesi (Campbell and Clark) has a last appearance datum of Ma; it might have been reworked from an earlier seawater incursion in the northern gulf. Thalassiosira oestrupii (Ostenfeld), an Early Pliocene diatom zonal marker, and the radi- olarians Didymoeyrtis petiiiltimiis (Riedel) and Spoii- i^aster peiitas Riedel and Sanhlippo in the upper part of the member suggest it is Ma. The diatomite member grades upward to the Caiioii las Cuevitas Mudstone Member. Canon las Cuevitas Mudstone Member. Late Mio- cene.—The type section is along an unpaved road just east of Buenavista Pass (Nelson. IM21 ). ap- 12-15 km west of Pete's Camp on Mexico 5. The pumiceous mudstone is almost 65 tii thick and contains middle bathyal microfossils such as the Late Miocene to Early Pliocene Uviiierina peret^rina Cush- man (Boehm, 1984. and revised ages for Zones N 1 7- NI9). Stock ( 1997) reported a pumice and lapilli layer just above the base that had a ^"Ar/*"Ar age of ± Ma. Unnamed marine conglomerate. Pliocene.—The overlying unnamed marine conglomerate of R. L. An- dersen (1973) was referred to the Salada Formation by Boehm ( 1984) and later authors, but that name is not appropriate because of differences in lithology. prov-
Size: 1951px × 1281px
Photo credit: © Book Worm / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookauthorpaleonto, bookcentury1800, bookdecade1890, bookyear1895
