Origin, dimensions, and distribution of remobilized carbonate deposits in a tectonically active zone, Eocene Thebes Formation, Sinai, Egypt

Abstract

Determination of the distribution and mechanism for carbonate-dominated mass transport sediments is often compromised by the scale and access to exposures. Consequently, many studies lack the resolution to capture the heterogeneity and dimensions of mass transport deposits. This study documents the size, shape, and stratal assemblage of remobilized carbonates in the Eocene Thebes Formation in the Hammam Faraun Fault Block (HFFB) of western Sinai, revealing the complexities of carbonate mass transport deposits at sub-seismic scale. Present day pseudo three-dimensional exposure of the Thebes Formation in a large fault block, formed during the opening of the Gulf of Suez, allowed for lateral and down-dip measurement of slope and basinal facies in the field and from photos. Remobilized facies were digitized in the photos and evaluated using image analysis software, a technique with a wide range of applications to outcrop studies of sedimentary architecture. Debris flow deposits in the lower section of the Thebes Formation comprises clasts with differing fossil assemblages. A relative sea level rise at the start of upper Thebes Formation deposition resulted in basinal sediments comprising periodic incursions of high-density turbidite grainstones encased within a background of planktonic foraminiferal wackestones. Foraminiferal assemblages of remobilized facies imply multiple sources on the carbonate platform, demonstrating the effect of short-lived tectonism on slope instability and deposition of mass transport deposits. The results of the study confirm that tectonism associated with the Syrian Arc Fold Belt, which altered the style of basin sedimentation between Egypt and Syria, persisted into the Eocene at least as far south as Wadi Araba in the western desert and Hammam Faraun in Sinai. In addition, the shape, size, and extent of the two dominant remobilized facies, debris flows and grainstone turbidites are influenced by their mud-rich versus grainy compositions.

Carbonate slope re‐sedimentation in a tectonically‐active setting (Western Sicily Cretaceous Escarpment, Italy)

“…, some of the deep‐rooted faults could have been related to the reactivation of older faults (Lower Jurassic) occurring in Sicily that were related to the drowning of the carbonate platforms (Di Stefano et al ., ). Reactivation of pre‐existing extensional faults that account for slope instability and reworked sediments resulting in large MTDs are described from the Eocene Thebes Formation, exposed along the eastern coastline of the Gulf of Suez (Corlett et al ., ). Similarly, along the WSCE, faulting during the Cretaceous created a series of escarpments that became prone to instability and lead to megabreccia and olistolith deposition.…”

A geocellular modelling workflow for partially dolomitized remobilized carbonates: An example from the Hammam Faraun Fault block, Gulf of Suez, Egypt

“…One of the anticlinal ridges associated with the SAFB that developed in the unstable area of the Arabo-Nubian massif formed through reactivation of the Wadi Araba fault. Repeated tectonism along the Wadi Araba fault during deposition of the Thebes Formation led to multiple stacked masstransport deposits in the HFF Block study area (Corlett et al, 2018). Finally, the third syn-rift megasequence unconformably overlies the earlier pre-rift strata comprising siliciclastics of the Nukhul Formation, overlain by evaporites of the Ras Malaab Group (Sharp et al, 2000).…”

“…Reactivation of the Wadi Araba fault during the SAFB resulted in the deposition of masstransport deposits south of Wadi Araba in the Galala Plateau region of the Eastern Desert (Scheibner et al, 2003;Höntzsch et al, 2011) and in the HFF Block study area along a NNW to SSE shallowly dipping ramp. The Thebes Formation at the HFF Block study site contains multiple mass-transport deposits that were deposited onto a middle to outer carbonate ramp consisting of slope to basin packstones (S-1 and B-1) to mudstones (Corlett et al, 2018).…”

“…Mass-transport facies (R-1 to R-6) represent a history of tectonic instability during the SAFB along the Wadi Araba fault, currently located on the western side of the Gulf of Suez, northwest of the HFF Block (Schütz 1994). Full descriptions of these facies and the depositional history may be found in Corlett et al (2018) and are summarized in Table 1. The Thebes Formation in the HFF Block is informally divided into lower and upper units with the lower dominated by mostly R-1 matrix supported conglomerate debrites, with sharp irregular base and convex upper contact, surrounded and draped by in situ slope packstones (S-1), and R-2 tabular, graded foraminifera grainstone turbidites beds that, when present, follow facies facies R-1, and overlain by facies S-1.…”

“…Of these 34 logs, 24 were recorded by hand and measured directly on the face of the exposure. The remaining ten logs were recorded as "laser logs" using a laser range finder (TruPulse 200L) to measure sections in inaccessible cliff faces (Corlett et al, 2018). The laser logs were recorded during a third field season, following facies and structural mapping, along with detailed facies descriptions.…”