Fragmentation, rafting, and drowning of a carbonate platform margin in a rift-basin setting

Abstract

High-resolution bathymetric and shallow seismic data along the northeast Red Sea margin reveal a previously disregarded mechanism for carbonate platform drowning at a steep-flanked rift basin. At the seafloor, salt extrusions highlight the influence of extensional salt tectonics, with a salt flow from the southern flank of the Al Wajh carbonate platform that likely originates from below. Salt-flow direction, morphology, and kilometer-sized slumps and rotated blocks indicate platform-margin disintegration and rafting of platform blocks toward the southwest. The outlines of several smaller detached or semi-detached carbonate platforms to the south of the main platform can be refitted to the larger platform margin by counter-moving the direction of mass wasting. Several platforms, reaching heights above the seafloor of up to 650 m, are partially or fully submerged in the mesophotic zone and appear to be in danger of drowning. We conclude that the southern outer rim of the Al Wajh platform is breaking apart owing to salt withdrawal, which indicates that carbonate platforms on top of salt sequences grow on mobile ground, leading to platform disintegration, basinward rafts, and the demise of broken-off, smaller pieces of platform. Salt displacement also controls the growth geometries of individual platform rafts, with keep-up reef growth (growth rate equal to sea-level rise) and drowning occurring in close spatial proximity. Therefore, the interplay between salt diapirism and platform growth is not limited to platforms growing on the apexes of diapirs and is more complex than previously thought.

Sediment dynamics and geomorphology of a submarine carbonate platform canyon system situated in an arid climate setting

“…The Red Sea is a young, narrow, land‐locked marine rift basin with active axial zone seafloor spreading (Purser & Bosence, 1998; Augustin et al ., 2021). The occurrence, morphology and hydrography of the present‐day reefs are directed by extensional tectonic processes and salt diapir formation (Montaggioni et al ., 1986; Dullo & Montaggioni, 1998; Bosence, 2005) and salt withdrawal (Petrovic et al ., 2023). The land‐attached reefs are also influenced by the input of clastics delivered by flash floods through wadis entering the marine realm (Piller & Pervesler, 1989; Piller & Mansour, 1994; Petrovic et al ., 2022).…”

“…The modern morphology of the Red Sea margins is primarily influenced by fault blocks, salt tectonics and siliciclastic input derived from onshore drainage systems (Bosence, 2005; Smith & Santamarina, 2022; Petrovic et al ., 2023). Narrow and gently inclined shelves in the northern Red Sea connect to steep‐sloped shallow‐water carbonate platforms and fringing reefs.…”

“…Their formation was previously interpreted to be exclusively related to rift tectonics, salt diapirs and fan deltas (Dullo & Montaggioni, 1998; Bosence, 2005; Rowlands et al ., 2014; Rowlands & Purkis, 2015). However, a recent study highlighted the additional influence of salt withdrawal on carbonate platform evolution (Petrovic et al ., 2023). The land‐attached Al Wajh carbonate platform is in the north‐eastern part of the NNE to SSW‐oriented Zabargad fracture zone, which is interpreted to be an extensive transform fault system (Crane & Bonatti, 1987; Ligi et al ., 2018).…”

Stratigraphic evolution and drowning steps of a submerged isolated carbonate platform in the northern South China Sea

“…Many ICPs later drowned, while others persevered and continued to grow to become modern ICPs (Courgeon et al, 2016). The long-term evolution of ICPs and drowning episodes leading to guyot formation have been the focus of several studies over the last few decades; however, the controlling factors remain unclear (El-Yamani et al, 2022;Petrovic et al, 2023). The internal architecture, onset, growth, and demise of guyots are determined by the biotic evolution, eustasy, volcanism, subsidence, and environmental variables (Courgeon et al, 2018).…”

“…Platform drowning is thought to be caused by a variety of interactive factors, including (1) an abrupt increase in accommodation space induced by rapid sea-level rise and subsidence exceeding the carbonate growth potential and flooding the shallow-water carbonate platform below the photic zone (Schlager, 1981;Petrovic et al, 2023), (2) a sharp decline in carbonate factory production associated with the degradation of environmental and climatic conditions, such as global anoxic events and excess of clastic and/or nutrient input (Sattler et al, 2009;Vu et al, 2017), and (3) strong current flow causing sediment removal and exclusion of sessile fauna (Hata et al, 2017;Betzler et al, 2021;Ling et al, 2021). Under pressure, the factory's surface area may frequently decrease and retreat to higher or more protected topographies to combat unfavorable environmental conditions or keep up with the swiftly rising accommodation space.…”