Stratigraphy And Paleoecology Of The Mulege Embayment, Baja California Sur, Mexico

A diverse fauna consisting of 86 species of gastropods, 62 pelecypods, 3 echinoids, 1 scaphapod, 1 anthozoan and 1 arthropod was collected from a prominent + 12m marine terrace in the Mulegé area. This fauna and two U 234fIh 230 dates of 124,000 t6000 years and 144,000 t 7000 years (Sangamon, Se highstand) establish a late Pleistocene age for this terrace at Mulegé, Baja California Sur, México. The geology of Mulegé area consists of a thick series of volcanoclastic rocks of the Oligocene-MioceneComondú Group unconformably overlain by thin upper Pliocene near-shore and estuarine marine sediments of the Infierno Formation. These are unconformably overlaip by the Mulegé Formation (new formation) which consists of marine sandstones and conglomeratesin locally extensive terrace deposits. In the late Pleistocene the Mulegé area consisted of a brackish sand and mud-flat estuary flanked by open-otean, rocky, and sandy shoreline environments. The estuarine and near-shore environments in the Infierno Formation and Mulegé Formation document the presente of the Mulegé estuary during the late Pliocene and late Pleistocene. The presente of these paleo-environments near their original sea leve1 position indicates no significant late Pliocene to recent uplift of the Baja California Península in this area.