Abstract

MONREAL, Rogelio et al. Characterization of the Bisbee Group (Lower Cretaceous) south of the Basómari Range, northeastern Sonora, Mexico. Bol. Soc. Geol. Mex [online]. 2011, vol.63, n.2, pp.365-378. ISSN 1405-3322.

The Bisbee Group is the most important lithostratigraphic unit that identifies the Lower Cretaceous in southeastern Arizona and northeastern Sonora. In the sierra Basómari, this group is characterized by outcrops of the Morita, Mural and Cintura formations, which are strongly affected by folds of kilometric dimensions locally overturned, normal faults of Mesozoic age, and a Cenozoic normal faulting. These lithostratigraphic units are overlain by Tertiary volcanic and sedimentary rocks. In the study area the Morita Formation is constituted by thin- to medium-bedded fine-grained sandstone, with some horizons with fossil wood, intercalated with fossiliferous and marly thin- to medium- bedded limestone. The Mural Limestone is characterized by thin- to massive-bedded fossiliferous limestone, intercalated with thin- to medium-bedded sandstone and clayish sandstone beds. The Cintura Formation is mainly made up of thin- to massive-bedded sandstone intercalated with laminar to thin-bedded mudstone. The Bisbee Group rocks in the area of the sierra Basómari represent shallow- marine sedimentary environments: intertidal inner neritic, middle neritic with development of lagoonal and ooidal bank conditions, outer neritic (open marine platform) and pelagic.

Keywords : lithostratigraphy; Lower Cretaceous; Bisbee Group; Sonora; Mexico.