Mollusks of the Upper Jurassic (upper Oxfordian-lower Kimmeridgian) shallow marine Minas Viejas Formation, northeastern Mexico

U-Pb ages of igneous xenoliths in a salt diapir, La Popa basin: Implications for salt age in onshore Mexico salt basins

“…1). A Gulf of Mexico, as opposed to Panthalassan, or Pacific, source for the marine water that fed the onshore salt basins is indicated by a dominant Gulf of Mexico affinity of the mollusks in the Minas Viejas carbonate strata (Zell et al, 2015). The salt of the onshore Mexican salt basins thus bears a relationship to the Louann Salt analogous to that of Holocene salt pans with intercalated mafic volcanic rocks within the Afar Depression of East Africa to Miocene salt of the Red Sea rift basin, which is separated from the depression by a basement arch (e.g., Bosworth et al, 2005).…”

“…Late Jurassic (160-159 Ma) 40 Ar/ 39 Ar dates on allochthonous volcanic xenoliths in salt diapirs were previously reported from coastal Louisiana (Stern et al, 2011), but the stratigraphic relationship of the xenoliths to the salt is uncertain. Interpretation of salt age in the Gulf of Mexico basin relies principally on the biostratigraphic age of overlying strata (e.g., Salvador, 1987), whereas the age of onshore Mexico salt is suggested by biostratigraphic age of carbonate blocks in diapirs of La Popa basin (Vega and Lawton, 2011) and carbonate strata interbedded or structurally interleaved in exposed evaporite in the Sierra Madre Oriental (Cross, 2012;Zell et al, 2015). Because the stratigraphic relations of evaporite and fossiliferous carbonate strata are somewhat equivocal, independent evidence of salt age is desirable for establishing tectonic models of salt deposition in the Gulf region and elsewhere.…”

“…From sample ages and textural characteristics, we infer the original stratigraphic context Gypsum, shale, and limestone alike contain abundant characteristics of peritidal to supratidal depositional conditions, including chicken-wire structure, small oscillation ripples, desiccation polygons, birds-eye structure, peloids, thin cryptobiotic lamination, and locally abundant untransported oyster accumulations (Kroeger and Stinnesbeck, 2003;Cross, 2012). Ammonite and bivalve fossils, including the gryphaeid oyster Nanogyra virgula, recovered from carbonate strata in the upper ~550 m of the Minas Viejas Formation indicate a late Oxfordian-early Kimmeridgian age for the carbonates (Cross, 2012;Zell et al, 2015). The Minas Viejas section in the Sierra Madre Oriental is gradationally overlain by sandy limestone that has long been considered as pertaining to the Zuloaga Limestone (e.g., Kroeger and Stinnesbeck, 2003), which is late Oxfordian in exposures to the west where salt is absent (Imlay, 1943).…”

Provenance and maximum depositional ages of Upper Triassic and Jurassic sandstone, north‐eastern Mexico

“…Near Ciudad Victoria, the Olvido Formation (broadly equivalent to the Minas Viejas Formation) contains late Oxfordian ammonites (Humphrey & Diaz, 2003). The middle part of the Minas Viejas Formation near Galeana likewise contains late Oxfordian to early Kimmeridgian fossils (Cross, 2012; Zell et al, 2015). Two zircon crystals from a felsic volcanic layer stratigraphically above the member with late Oxfordian fossils yielded U‐Pb isotopic dates of ca.…”