Abnormally high fluid pressures exist within the Cretaceous sediments of the Sacramento Valley and probably exist within similar sediments of the San Joaquin Valley. The existing fluid potential distribution and chemistry of the pore waters strongly suggest that the abnormally high fluid potentials result from tectonic compaction stemming from continuous uplift of the California Coast Range, at least from late Tertiary into Recent time. This uplift has squeezed, as in a closing vice, the prism of Mesozoic sediments within and between the rising Coast Range and the relatively stable Sierran basement. The distribution of these high fluid potentials, laterally and with depth, suggests that the great majority of the Mesozoic sediments occupying the Coast Range has fluid press res which approximate those exerted by the lithostatic load. Low-angle thrusting may be an important future structural event of this region as a result thereof. The production of such high fluid potentials by regional tectonic compaction may be a normal occurrence during the regional uplift of a geosynclinal system.

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