THE APTIAN-ALBIAN CONTINENTAL-MARINE SYSTEM OF THE NORTHERN NEGEV, SOUTHERN ISRAEL: DEPOSITIONAL SETTINGS, PALEOENVIRONMENTS AND CYCLIC STRATIGRAPHY

The Aptian-Albian continental/marine transition of the NW Arabian Plate is represented in southern Israel by siliciclastics and minor carbonates representing a broad spectrum of fluvial, aeolian, shallow-marine, and distal-marine facies. The fluvial suite includes sandy cross-bedded braided channel deposits and overbanks with incipient paleosols, and fine-grained coastal-floodplain deposits with well-developed paleosols. Aeolianites correspond to large-scale dunes to 3m high, and smaller, inversely-graded, critically climbing translatent laminae sets originating as wind ripples. Climate shifts are reflected in the paleosols. The dominant paleosols are analogous to modern spodosols and hydromorphic oxic horizons indicating humid climates, but semiarid climate transitions are expressed by aeolianites with associated K horizon duripans (calcretes) and calcite-bearing A horizons.

Sharp-based, cross-bedded, laminated or ooidal shallow marine sandy carbonates truncate the fluvial units and pass offshore to bioturbated fines with preserved trace-fossils, and then to basinal beds of marl and laminated dark shale with ammonites, and phosphatic hardgrounds enriched with ferruginous ooids. These facies sets can be stacked into 3^rd order R/T cycles, beginning with a deeply incised FSST unconformity with highly-developed lateritic paleosols. Incised within are fluvial or fluvio-aeolian LST regressive deposits indicating low continental accommodation. Upwards, marine siliciclastics and carbonates lie above transgressive or ravinement surfaces sharply, reflecting abrupt sea-level rise and accommodation-space expansion.

The R/T cycles can be grouped into four 2^nd order cycles dated to Barremian-Early-Aptian, mid-Aptian–earliest Albian, Early to mid-Albian, and Late Albian, that correlate with eustatically-controlled transgressive episodes known from northern Israel and the Arabian Plate. The transgressive part of the second 2^o cycle is marked by deep subtidal carbonate-free laminated dark shales topped by phosphatic marls with ammonites that indicate abrupt sea-level rise and marine onlap accompanied by organic influx and anoxic conditions. The ammonites date this transgressive interval to near the OAE1b.