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ABSTRACT: The K/T Boundary, Cretaceous/Late Paleocene Unconformity and Stratigraphy of the Western San Joaquin Valley, California

Max B. Payne

Anderson and Pack named the Cretaceous Moreno and Panoche formations and described their type sections. Although mapping these formations over 193 km, they did not recognize the K/T boundary unconformity that cuts out the Moreno and the upper Panoche north of the type sections. Payne described four members of the Moreno at Escarpado Canyon, their type section, and the stratigraphically most complete exposure. The Paleocene (Danian) Dos Palos Shale Member of the Moreno overlies the uppermost Cretaceous (Maastrichtian) Marca Shale Member.

North and south of the southeast Panoche Hills, a late Paleocene unconformity truncates the Cretaceous sequence. Southward, the lowest Paleocene sand at the base of the Cerros Shale Member of the Lodo Formation contains the Turritella pachecoensis fauna. Northward this fauna appears in the Paleocene Laguna Seca Sand, with type section at Laguna Seca Creek in the Laguna Seca Hills. The subsurface Laguna Seca Sand commonly but erroneously has been cited as Garzas, a term lacking description or published type section. The 6.7-km Panoche was elevated to group status, and described in detail together with its newly included formations, and the Moreno and Panoche Formations were further discussed and mapped southward.

A recent suggestion, based on absence of a benthic foraminifer, that 600 m or more of Panoche have been faulted out at its type section is unsupported by detailed mapping and ammonite and inocerami sequences, as none indicate a gap in the sequence at this locality.

AAPG Search and Discovery Article #91003©1990 AAPG Annual Convention, San Francisco, California, June 3-6, 1990