Sequence development of Late Cenomanian-Turonian carbonate ramps, platforms and basins in Israel

The Cenomanian-Turonian carbonate-dominated lithofacies of Israel reflect a complex interplay between tectonics, sea-level change, and palaeoecology. Improved correlation based on revision of the bio- and chronostratigraphic framework has enabled the establishment of a sequence-stratigraphic model c omprising five sequences delineated by four sequence boundaries, in the Lat e Cenomanian-Early Coniacian interval. The Late Cenomanian-Turonian success ion begins with prograding, highstand, carbonate-platform deposits of the f irst sequence. Interruption of progradation and drowning of this platform t ook place within the Late Cenomanian guerangeri Zone (=the vibrayeanus Zone in Israel), resulting in a drowning unconformity which is regarded as a Ty pe 3 sequence boundary (labelled CeUp). The drowning is attributed in part to extinctions in the rudist-dominated biofacies (e.g., Caprinidae), which led to reduced carbonate production and enhanced the impact of the sea-leve l rise. Similar drowning of Tethyan platforms around the CIT boundary has b een linked to the establishment of coastal upwelling and consequent eutroph ication. Outer ramp hemipelagic facies (Derorim and the Lower Ora formation s) replaced the platform carbonates, thickening substantially southwards in the Eshet-Zenifim Basin of southern Israel. Along the ancient continental slope (Mediterranean coastal plain) evidence of this drowning is obscured b y submarine erosion, while in central and northern Israel the drowned secti on is represented by condensation or a hiatus, reflecting an elevated, sedi ment-starved sea-floor. A carbonate platform dominated by rudistid shoals ( 'Meleke' Member; Shivta Formation) was re-established in the Judean hills a nd northern Negev during the middle part of the Turonian coloradoense Zone (local zone T4). Later, during kallesi Zone times (T7), the platform facies prograded southwards towards the Eshet-Zenifim intra-shelf basin. The drow ning succession and overlying resurrected carbonate platform are topped in central and southern Israel by a pronounced Type 1 sequence boundary (Tu1) between the kallesi (T7) and ornatissimum (T8) zones (Middle Turonian). In central Israel and northern Negev the sequence boundary is overlain by lows tand deposits of the 'Clastic Unit' and by the transgressive and highstand inner to mid-ramp deposits of the Nezer and Upper Bina formations. In the s outhern Negev the sequence boundary is overlain by lowstand and transgressi ve systems tracts of mixed carbonates, siliciclastics, and localized evapor ites (Upper Ora Formation), and then by mid to inner ramp carbonates of the Gerofit Formation. The latter represents a very high rate of accumulation, indicating rapid, continued subsidence balanced by platform growth. The Tu 2 sequence boundary of the Late Turonian is expressed in the southern Negev by a shift from inner ramp carbonates of the Gerofit Formation to outer ra mp chalky limestones of the Zihor Formation, indicating localized drowning. The succeeding Col sequence boundary again indicates localized drowning of the prograding highstand deposits of the Zihor Formation ('Transition Zone ') overlain by Lower Coniacian transgressive deposits of the upper part of the Zihor Formation. All of these third-order sequences are expressed in so uthern Israel, where the rate of subsidence was in balance with sea-level f luctuations. In contrast, the Judean Hills and eastern Galilee areas have a more incomplete succession, characterized by hiatuses and condensation, be cause of reduced subsidence. More distal areas of continuous deep-water deposition in western Galilee an d the coastal plain failed to record the Middle Turonian lowstand, while a longer term, second-order sequence spanning the entire Late Cenomanian-Earl y Coniacian interval, is present in the Carmel and Yirka Basin areas. (C) 2 000 Academic Press.