Resumo

OCAMPO-DIAZ, Yam Zul Ernesto; JENCHEN, Uwe  e  GUERRERO-SUASTEGUI, Martín. Facies and depositional systems of the Galeana Sandstone Member (Taraises Formation, Lower Cretaceous, northeastern Mexico). Rev. mex. cienc. geol [online]. 2008, vol.25, n.3, pp.438-464. ISSN 2007-2902.

The sandstone of the Galeana Sandstone Member ofTaraises Formation have been interpreted as an extended delta deposit, which had its origin from the Coahuila Block, and few authors have proposed that the source area could be associated with the Tamaulipas Archipiélago. The present study documents the sedimentological characteristics of the Galeana Sandstone Member, and on the basis of fades analysis and paleocurrent data, the sedimentary environments, and its depositional evolution were determined. The sandstone of the Galeana Sandstone Member show seven fades associations, which are interpreted as tidal flat, prodelta, tidal-dominated delta front, deltaic barred mouths, sublittoral and subaqueous dune deposits. The tidal flat deposits are characterized by thinning-upward sequences, and they contain herringbone cross-bedding, lenticular andflaser bedding, as well as trace fossils of the genus Skolithos, Thalassinoides, Diplocraterion, and Rhizocorallium. The deltaic system, deltaic barred mouth, and sublittoral deposits are characterized by interbedded sandstone and shale that show thickening-upward and thinning-upward sequences, as well as scarce sedimentary structures such as parallel lamination, normal graded beds, lenticular stratification, herringbone cross-bedding, and Macaronichnus trace fossils. The subaqueous dune deposits show chaotic sequences with cross-bedding generated by dunes migration, reactivation surfaces, and ichnofossils of the genus Thalassinoides. The field data, such as paleocurrent and stratigraphic relationships suggest that: (i) sandstone of the Galeana Sandstone Member had a source area located to the east of Potrero Prieto locality, which could be the Tamaulipas Archipiélago, and (ii) the depocenter is located in the Galeana area, as indicated by the observed changes in bed thicknesses and the presence of an angular disconformity.

Palavras-chave : Sedimentology; tidal flats; deltaic sedimentation; Taraises Formation; Galeana Sandstone Member; Cretaceous; NE Mexico.