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The early Pleistocene Laguna and Turlock Lake Formations and China Hat and Arroyo Seco Gravels along the east side of the San Joaquin Valley, California, were deposited in alluvial fans and marginal lakes. Upward-coarsening sequences of silt-sand-gravel record westward progradation of glacial outwash fans from the Sierra Nevada into proglacial lakes in the San Joaquin Valley. Distinctive sedimentary features delineate lacustrine, prodelta, and delta-front facies within fan-margin deposits and lower, middle, and upper-fan facies within alluvial-fan deposits.The lacustrine facies consists of a few metres of thinly and evenly bedded, rhythmically laminated claystone and clayey siltstone in varved couplets. Draped lamination, sinusoidal lamination, and load and pillar structures occur in some beds. Siltstone and claystone grade upward to slightly thicker wavy beds of siltstone and very fine-grained unconsolidated sand deposited in a prodelta setting. Convolute laminae within deformed steeply dipping foreset beds suggest slumping on the prodelta slope. The prodelta facies grades up to the delta-front facies, which consists of burrowed and bioturbated cross-bedded fine sand.Deltaic deposits are 5-6 m thick.The lower-fan facies forms the base of the fan sequence and consists of several metres of irregularly bedded, laminated, oxidized siltstone and fine sand. The middle-fan facies consists of cross-bedded, medium-grained to gravelly sand-filled channels cut into the lower-fan facies. lnterbedded lens-shaped siltstone beds 2 m thick and several metres across were deposited in abandoned channels. The upper-fan facies consists of moderately to strongly weathered clayey gravel and sand containing pebble imbrication and crude stratification. Argillization during post-depositional soil formation has blurred the distinction between mud-supported debris-flow deposits and clast-supported channel deposits, but both are present in this facies.The deposits described here demonstrate the need for additional fan models in order to incorporate the variety of deposits developed in alluvial fan sequences deposited in humid climates. In previous models based on arctic fans, debris flows, abandoned channels, or widespread siltstone beds are not present in fan sequences, nor are marginal lacustrine and deltaic deposits well represented.

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Local middle Eocene tectonic activity within the southern Sacramento Basin divided it into eight deposltlonal provinces during deposition of the Domenglne Formation. These provinces include the 1) Southeastern Channel Area, which grades laterally (southwest) to the 2) Southern Marsh Area and offshore (northwest) to the 3) Northeastern Bar Area. This latter area grades still farther northwest to the relatively stable 4) Northwestern Shelf Area, but was disrupted by active faults Into the subsident 5) Rio Vista Basin and 6) Sherman Island Trough to the west and southwest. This subsldent region was bordered on the south by the 7) Mt. Diablo Uplift and on the west by the 8) Kirby Hills Uplift. The Domenglne can be divided into eight distinct members, not all of which are present in each depositional provinee. Sedimentary facies within the eight members of the Domengine include 1) upward-fining coarse-to fine-grained sandstone beds, 2) upward-coarsening bar or delta-front/shoreline sandstone beds, 3) foramin perferal shelf shale, 4) carbonaceous marsh deposits, 5) fIaser-bedded subtidal deposits, 6) shelf sandstone, and 7) fluvial conglomerate and sandstone. The Domengine Formation is probably a tide-wave-dominated deltaic system. Although marine processes were Important in controlling the types and distribution of grain sizes and sedimentary structures, the overall sediment distribution system and resulting formational geometry were controlled by tectonics and subsidence related to the growth of the Stockton Arch, sediment compaction in the Meganos Gorge (submarine canyon), active faulting, and distribution of basin-margin up lifts.

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