WARM-TEMPERATE, MARINE, CARBONATE SEDIMENTATION IN AN EARLY MIOCENE, TIDE-INFLUENCED, INCISED VALLEY; PROVENCE, SE FRANCE
The Saumane-Venasque compound paleovalley succession accumulated in a strongly tide-influenced embayment or estuary. Warm-temperate normal marine to brackish conditions led to deposition of extensive cross-bedded biofragmental calcarenites. Echinoids, bryozoans, coralline algae, barnacles, and benthic foraminifers were produced in seagrass meadows, on rocky substrates colonized by macroalgae, and within subaqueous dune fields. There are two sequences, S1 and S2, the first of which contains three high-frequency sequences (S1a, S1b and S1c). Sequence 1 is largely confined to the paleovalley with its upper part covering interfluves. Each of these has a similar upward succession of deposits that includes; 1) a basal erosional surface that is bored and glauconitized; 2) a discontinuous lagoonal lime mudstone or wackestone; 3) a thin conglomerate generated by tidal ravinement; 4) a TST series of cross-bedded calcarenites; 5) a MFI of argillaceous, muddy quartzose, open-marine limestones; and 6) a thin HST of fine-grained calcarenite. Tidal currents during stages S1a, S1b and S1c were accentuated by the constricted valley topography, whereas basin-scale factors enhanced tidal currents during in the deposition of S2. The upper part of the succession in all but S1c has been removed by later erosion. There is an overall upward temporal change with quartz, barnacles, encrusting corallines, and epifaunal echinoids decreasing but bryozoans, articulated corallines, and infaunal echinoids increasing. This trend is interpreted to be the result of changing oceanographic conditions as the valley was filled, bathymetric relief was reduced, rocky substrates were replaced as carbonate factories by seagrass meadows and subaqueous dunes, and the setting became progressively less confined and more open marine. These limestones are characteristic of a suite of similar cool-water calcareous sand bodies in environments with little siliciclastic or freshwater input during times of high amplitude sea-level change wherein complex inboard antecedent topography was flooded by a rising ocean.