This study aims to provide the depositional facies, sequence stratigraphic and paleoclimatic characteristics of the
Mid-Eocene (Bartonian) continental succession exposed at Gebel El-Goza El-Hamra (Shabrawet Area, NE Eastern
Desert, Egypt). The studied succession consists of siliciclastic rocks followed upward by carbonate rocks. Detailed
field observation and petrographic investigation indicate accumulation in floodplain-dominated alluvial and
shallowlacustrine systems. The floodplain-dominated alluvial facies (45mthick) is composed mainly of carbonate
nodules-bearing, mottled mudrock with subordinate sandstone and conglomerate beds. The conglomerate
and pebbly sandstone bodies interpreted as ephemeral braided channel deposits. The massive, laminated,
planner cross-bedded, fine- to medium-grained sandstone bodies interlayered within mudstone reflect sheet
flood deposits. The mudrocks associated with paleosols represent distal floodplain deposits. The shallow
lacustrine facies (15 m thick) is made up of an alternation of marlstone, micritic limestone, dolostone and
mudrock beds with charophytes and small gastropods. Both the alluvial and lacustrine facies show evidence of
macro-and micro-pedogenic features. Pollen assemblages, stable δ18O and δ13C isotopes, and paleopedogenic
features reflect prevalence of arid to semi-arid climatic conditions during the Bartonian.
The sequence stratigraphic framework shows an overall fining-upward depositional sequence, consisting of Lowand
High-accommodation Systems Tracts (LAST, HAST), and is bounded by two sequence boundaries (SB-1, SB-
2). Conglomerate and pebbly sandstone deposits (braided channel and sheet flood deposits) of the lower part of
the alluvial facies reflect a LAST. Mudrock and silty claystone facies (distal floodplain deposits) of the upper part
of alluvial facies and its overlying lacustrine facies correspond to a HAST. The LAST, HAST and SB were formed
during different accommodation-to-sediment supply (A/S) ratio phases. The variation in A/S ratios was mainly
controlled by sea-level change as well as by local tectonic subsidence and uplift of the basin coincident with
the reactivation of the Syrian Arc System during the Bartonian. |
