. Bulletins of American paleontology. 70 Bulletin 371 extensive and significant tor the histiny tit'the northern Gulf of California. Sequence 3 consists of alluvial Ian deposits and fanglomerates. Tuff of San Felipe. Middle Miocene.—Called ••Tnir," by Bryant ( 1986). the Tuff of San Felipe was named and described by Stock et ul. ( 1999) for a wide- spread, rhyolitic tuff that is well-exposed near Caiion el Parral between the Sieira de Santa Rosa and the SieiTa San Fermin (Text-hg. 43). It is characterized by densely welded lithic lapilli and a thickness of ISO ni near its presumed vent ar
. Bulletins of American paleontology. 70 Bulletin 371 extensive and significant tor the histiny tit'the northern Gulf of California. Sequence 3 consists of alluvial Ian deposits and fanglomerates. Tuff of San Felipe. Middle Miocene.—Called ••Tnir," by Bryant ( 1986). the Tuff of San Felipe was named and described by Stock et ul. ( 1999) for a wide- spread, rhyolitic tuff that is well-exposed near Caiion el Parral between the Sieira de Santa Rosa and the SieiTa San Fermin (Text-hg. 43). It is characterized by densely welded lithic lapilli and a thickness of ISO ni near its presumed vent area close to the present coast- line. It has a radiometric age of Ma and a low- inclination reversed magnetization that was interpreted h\ Stock ct cil. ( 1999) as within reversed polarity sub- chron ( Ma). The Tuff of San Felipe extends over an km- area. \\om the east- ern side of the Sierra San Pedro Martir to the coast ot the Gulf of California and 40 km to the southwest. Ongoing studies suggest the Luiil is present in Sonora, providing a link between the eastern and uestern sides of the ancient Gulf of California (Oskin el a!.. 2000). The Tuff of San Felipe is overlain by alluvial fan deposits, younger luffs, basalts dated at ± Ma. and Plio-Pleistocene continental deposits (Stock el uL. 1999). Puertecitos embaymeiil Plate 2. Column 27 (Text-hgs. 2. 43-45. Appendices ) Column alter Martin-Barajas et ul. ( 1997); the area is shown on the Puertecitos quadrangle, H11B77, 1: ; and geokigic maps o\' Martin-Barajas et ul. (1995, 1997), Lewis (1994), and Slock et al. (1991). Geographic Settiiiii The Puertecitos embayment extends over approxi- mately 300 km- from the southern Sierra San Fermin to the fishing port of Puertecitos; it lies east of the Sierra San Pedro Martir and the main Gulf eseaipment. Late Miocene to Early Pliocene shallow-water sedi- ments dominate the section in the northern part of the basin; volcanic units
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