VOLCANIC ARC DERIVED, MESOZOIC SEDIMENTARY ROCKS
Triassic through Cretaceous eugeoclinal strata on the Vizcaino Peninsula were deposited in association with the emplacement of volcano-plutonic complexes at the North American continental margin. The oldest associated unit is a 220 m.y. old partial, dismembered ophiolite that is conformably overlain by generally fine-grained marine volcaniclastic rock, impure limestone and chert of Late Triassic age. These Triassic strata are locally, unconformably overlain by Late Jurassic age or older coarse-grained marine volcaniclastic and extrusive rocks. Lithostratigraphic relationships indicate contemporaneous arc-type magmatism in close proximity during Late Jurassic-Early Cretaceous deposition. This magmatic arc terrane is represented on the Peninsula by volcanic and plutonic rocks which cluster in age between 140 to 155 m.y.