Evolution of Cretaceous to Eocene alluvial and carbonate platform sequences in central and south Jordan

Abstract

The Cretaceous to Eocene succession in central and south Jordan is characterised by passive continental margin depositional sequences, which pass upward from alluvial/paralic to carbonate shelf and pelagic ramp settings. Detailed section logging and outcrop mapping have produced robust lithostratigraphic and lithofacies schemes that can be correlated throughout the region and in the subsurface. These schemes are set in a sequence-stratigraphic context in relation to the evolution sedimentation on the Arabian and Levant plates. Three major megasequences are described (Kurnub, Ajlun and Belqa), and these are further subdivided into large-scale depositional sequences separated by regional sequence boundaries that represent maximum flooding surfaces. There is close correspondence between maximum flooding surfaces recording major sea-level rise with those derived for the Arabian and Levant plates, although there are some discrepancies with the precise timing of global sea-level fluctuations. An upward change from braided to meandering stream fluvial environments in central and south Jordan during the Early Cretaceous, reflects a decreasing geomorphological gradient of the alluvial plain, declining siliciclastic sediment flux, and increased floodplain accommodation, associated with a regional Late Albian (second-order) rise in relative sea-level. The Late Albian to Early Cenomanian marine transgression across the coastal alluvial plain marks a major sequence boundary. During Cenomanian to Turonian times a rimmed carbonate-shelf was established, characterised by skeletal carbonates showing small-scale, upward-shallowing cycles (fourth- to fifth-order parasequences) ranging from subtidal to intertidal facies, arranged into parasequence sets. Rimmed carbonate shelf sequences pass laterally to coeval coastal/alluvial plain facies to the south and east. Eustatic (third-order) fluctuations in relative sea level during the Cenomanian and Early Turonian resulted in deposition of ammonite-rich wackestones and organic-rich marls, during high sea-level stands (maximum flooding surfaces). Progradational sabkha/salina facies passing landwards to fluvial siliciclastics were deposited during an Early Turonian sea-level low stand, marks a regional sequence boundary, above which a highstand carbonate platform was established. A second-order, regional rise in sea level and marine transgression during the Early Coniacian marks a Type 2 sequence boundary, and subsequent drowning of the rimmed carbonate shelf by Late Coniacian times. Sedimentation during the Santonian to Maastrichtian was characterised by a hemi-pelagic chalk-chert-phosphorite lithofacies association, deposited in shallow to moderate water depths on a homoclinal ramp setting, although thicker coeval sequences were deposited in extensional rifts. The marked change in sedimentation from rimmed carbonate shelf to pelagic ramp is attributed to Neo-Tethyan mid-oceanic rifting, tilting, intracratonic deformation and subsidence of the platform; this is reflected in changes in biogenic productivity and ocean currents. Oceanic upwelling and high organic productivity resulted in the deposition of phosphorite together with giant oyster banks, the latter developing within oxygenated wave-base on the inner ramp. Chalk hardgrounds, sub-marine erosion surfaces, and gravitational slump folds indicate depositional hiatus and tectonic instability on the ramp. In the Early Maastrichtian, deeper-water chalk-marl, locally organic-rich, was deposited in density-stratified, anoxic basins, that were partly fault controlled. Pulsatory marine onlap (highstand sequences) during the Eocene is manifested in pelagic chalk and chert with a paucity of benthic macro-fauna, indicating a highly stressed, possibly hypersaline, and density-stratified water column. Comparison with global and regional relative sea-level curves enable regionally induced tectonic factors (hinterland uplift and ocean spreading) to be deduced, against a background of global sea-level rise, changing oceanic chemistry/productivity and climatic change.

A magnetotelluric transect across the Dead Sea Basin: electrical properties of geological and hydrological units of the upper crust

“…7b). From surface geology, Khalil (1992) and Powell & Basem (2011) identified the upper and lower Cretaceous as the Ajloun (mainly limestone) and the Kurnub (sandstone) groups, respectively. Taking into account the differences in uplift rates between the western and eastern rift shoulders (Garfunkel et al 1981), it seems plausible that the shallow conductive layer E1 coincides with the Kurnub Sandstone group.…”

Sequence Stratigraphy, Palaeogeography and Petroleum Plays of the Cenomanian – Turonian Succession of the Arabian Plate: An Updated Synthesis

“…In the onshore Levant, mixed carbonatesiliciclastic ramp systems are documented within the middle-late Turonian (Buchbinder et al, 2000;Bauer et al, 2003;Powell and Moh'd, 2011). High energy carbonate facies are recognized (Saint-Marc, 1981;Bauer et al, 2003;Schulze et al, 2005) (Figs 10 and 12f).…”

“…Outcrops in the onshore Levant, particularly the welldocumented sections in Jordan (e.g. Powell and Moh'd, 2011), provide a type-section for the Turonian of the Arabian Plate. In Jordan, a prominent salina/sabkha gypsum bed at the top of the Shueib Formation (see Fig.…”

“…In Jordan, a prominent salina/sabkha gypsum bed at the top of the Shueib Formation (see Fig. 10, Silla outcrop) (Schulze et al, 2005;Powell and Moh'd, 2011) marks the culmination of significant regression and the mid-Turonian K150 SB. This surface is contemporaneous with the major erosional unconformity noted across much of the Arabian Plate.…”

“…Extensive carbonate platforms are recognized across the northern part of the Arabian Plate (Buchbinder et al, 2000;Bauer et al, 2003;Schulze et al, 2005;Powell and Moh'd, 2011).…”