. Bulletins of American paleontology. 50 Bulletin 371. Texl-tigure 29.—Giant pectinid iiinlds Innii the i.(mlacl between Heim's beds 2 and 3 al the old Ibrt seetion. The right valve at lower left could be the largest individual recorded for the genus AmusM- iipciirn (Los Angeles County Museum ol Invertebrate Paleontology hypolype 7632); the other right valve is /uivola sp. (Los Angeles County Museum of Invertebrate Paleontology hypotype 7633). J. T. Smith locality 89J,S3 = ()3JS()4 of Text-figure 2S. Photo. J. T .Smith. 1985. (//. (). studies of the CeiTO Colorado Menibei, the
. Bulletins of American paleontology. 50 Bulletin 371. Texl-tigure 29.—Giant pectinid iiinlds Innii the i.(mlacl between Heim's beds 2 and 3 al the old Ibrt seetion. The right valve at lower left could be the largest individual recorded for the genus AmusM- iipciirn (Los Angeles County Museum ol Invertebrate Paleontology hypolype 7632); the other right valve is /uivola sp. (Los Angeles County Museum of Invertebrate Paleontology hypotype 7633). J. T. Smith locality 89J,S3 = ()3JS()4 of Text-figure 2S. Photo. J. T .Smith. 1985. (//. (). studies of the CeiTO Colorado Menibei, the upper subunit of the El Cien Formation, by Giddc ( and in Fischer el ciL. 1995) indicate it contains botii marine and nonmarine facies. regress- ing upsection \o a continental deposit. Earlier literature refers the Oiigocene-Mit)cene marine sequences in this area to older names, including the San Giegorio and Isidro Formations, which were described from the Purisima-lray basin to tiie north. Table 5 summari/es the stratigraphic nomenclature, which is still tiiidci dis- cussion. Granitic and mctamorphic basement rocks do not crop out in the western Magdalena embayment. Stnitii>iaphy Tcpetate Formation, lute Early Eocene to early Middle Eocene.—The type area in Arroyo Colorado was revisited by CaiTefio et al. (2000), who reviewed its stratigraphy, age. and depositional history. Strata in AiToyo Colorado were not designated by Heim (1922) but were regarded as the slratotype by Mina-Uhink (1957): the section has GPS coordinates 24°23'; N. Ill°07'; W (Instituto de Geologia Museo de Paleontologfa locality IGM-2984). CaiTeiio et al. (2000) divided the northeast-dipping 55-m-thick section into seven lithological units sepa- rated by erosional contacts; they recommended using a composite stratotype to represent the lithologic var- iation and longer chronostratigraphic range of the unit as a wh(.ile. The base is not exposed and the lowest part has no dia
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