Print this pageSubsidence of Neogene Basins in the Southern Gulf of California
James C. Ingle Jr.
Stratigraphic, geochronologic, and paleobathymetric data from DSDP sites 475
and 476 offshore of Cabo San Lucas, Baja Sur, Mexico together data from onshore
Neogene sequences exposed on (1) Isla Maria Madre in the gulf mouth, (2) Punta
Mita on Nayarit coast of mainland Mexico, and (3) the San Jose del Cabo area of
Baja Sur, allow rates and style of basin subsidence and margin deformation to be
determined for the southernmost Gulf of California through application of
backstripping techniques. Tectonic subsidence curves constructed for sequences
overlying oceanic, transitional, and continental crust reveal patterns of basin
formation as the southernmost gulf evolved from (1) a flooded portion of the
Basin and Range province to (2) a rifted setting associated with penetratio of
the East Pacific Rise. The distribution of Miocene (12 to 6 Ma) and Pliocene
marine sediments in this region indicates that major marine depocenters shifted
westward ca. 5 Ma in concert with (1) uplift and deformation of the eastern
margin of the Miocene proto-gulf and (2) rapid subsidence and formation of the
modern Gulf of California as rifting and spreading occurred along the relocated
East Pacific Rise during Pliocene time. Subsequent Plio-Pleistocene (ca. 2 to
0.7 Ma) deformation and uplift along the eastern margin of the newly formed
peninsula of Baja California again shifted major depocenters to their modern
positions within the evolving gulf. Analysis of 
magnetic
anomaly patterns and
microplate history in the eastern Pacific and gulf region by Atwater, Curray,
Klitgord, Lonsd le, Mammericks, Stock, and others permit tentative correlations
of major plate events and individual basin histories.
AAPG Search and Discover Article #91019©1996 AAPG Convention and Exhibition 19-22 May 1996, San Diego, California