Abstract

The Salinian block is the elongate segment of the California Coast Ranges that lies between the Sur-Nacimiento and San Andreas fault zones. Known basement rocks within this block consist of Cretaceous and older granitic and high-grade metamorphic rocks that contrast sharply with Franciscan Group rocks of overlapping age east of the San Andreas and west of the Sur-Nacimiento fault zones.

The metamorphic rocks of the Salinian block (often termed Sur series) are probably in part Paleozoic in age and appear to have been derived from a relatively shallow-water shelf-type sequence of psammitic rocks with subordinate calcareous and pelitic rocks. A graphite- and pyrite-bearing unit, mapped for more than 20 mi in the northern Santa Lucia Range, defines two sets of folds. Mineral lineations and mesoscopic folds indicate that major folding about northeast-trending axes occurred prior to prominant folding about north-northwest-trending axes.

Assuming approximately 300 mi of post-Cretaceous right slip along the San Andreas fault, the metamorphic rocks of the Salinian block are tentatively correlated with similar Paleozoic and, perhaps in part, Precambrian rocks of the Mojave Desert and southwestern Tehachapi Mountains. The age of the early northeast-trending folds is unknown, but they may be a southwestward extension of Paleozoic tectonic and stratigraphic trends that head from Nevada into southern California. The north-northwest-trending folds are in part Cretaceous as indicated by the syntectonic emplacement of Cretaceous granitic rocks.

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