Distinct relict fringing reefs in the northern shelf of the Gulf of Elat/Aqaba: Markers of Quaternary eustatic and climatic episodes

Abstract

Quaternary reef development and demise have been shown to correspond to worldwide sea-level fluctuations and related environmental changes, yet the mechanisms and rates affecting this relationship are not well resolved. A set of high-resolution seismic reflection and multibeam bathymetric data were interpreted. Six distinct systems of relict fringing reefs embedded within the sedimentary cover of the northern shelf of the Gulf of Elat/Aqaba were identified. The two uppermost relict fringing reefs are also exposed on the sea floor in water depths of ca 20 m and ca 60 m, along the north-western corner of the northern Gulf of Elat/Aqaba and sub-parallel to the current northern coast, respectively. Two other relict fringing reefs are laterally correlated to each of the last two transgressive cycles, and are inferred to have formed during decelerations in sea-level rise during the last two deglaciations. These reefs and the units to which they are laterally correlated portray a repeating stratigraphic pattern of reef development during deposition of seismically homogeneous sediment and an ensuing demise during deposition of heterogeneous sediment. Correlation of the reef stratigraphy with rates of Late Quaternary sea-level rise and a sediment accumulation rate from one shelf core provide age estimations for the seismic stratigraphy. Two phases of fringing reef generation occurred during the last deglaciation (since ca 18 ka); the older reef probably developed between 12Á8 ka and 11Á5 ka at ca 60 m below present sea-level and the younger reef after 8Á4 to 8Á0 ka at ca 20 m below present sea-level. These last two phases of reef generation are separated by a lobate seismic unit that is interpreted as fluvial-deltaic deposits that backstepped across the shelf during the Early Holocene transgression. Results suggest that fringing reefs evolved along the northern shelf of the Gulf of Elat/Aqaba only during relative decelerations in sea-level rise, contemporaneous with low input of terrigenous sediment and probably during a period of aridity. At present, no fringing reef grows along the northern coast of the 516 Gulf of Elat/Aqaba, suggesting that these relatively arid periods may have been drier than Recent. The pattern of slowdown in sea-level rise contemporaneous with conditions of increased aridity seems to have repeated during the last two sea-level rises, approximately at the same sea-levels, suggesting a common mechanism of short (millennium-scale) phases of eustatic and climatic alteration during deglaciations.

Timescale dependent sedimentary record during the past 130 kyr from a tropical mixed siliciclastic–carbonate shelf edge and slope: Ashmore Trough (southern Gulf of Papua)

“…Finally the southern GoP shelf‐edge reef provides another case study on the edification of transgressive reefs and barrier reefs on a fluvio‐deltaic substrate. Along with other case studies reported from Belize barrier reef (Ferro et al., 1999; Droxler & Jorry, 2013), the Gulf of Mexico (Rezak & Bright, 1976; Belopolsky & Droxler, 1999), the north‐east Brazilian outer shelf (Gomes et al., 2020), the Calabrian continental shelf of Italy (Franchi et al., 2018) and the Gulf of Elat/Aqaba in the Red Sea (Hartman et al., 2015), all of these Quaternary case studies may constitute relevant analogues to interpret geometries and facies heterogeneities in the subsurface. Recently, it has been demonstrated that at least two Miocene palaeodeltas in the South China Sea provided favourable substratum of elevated sand bars for the emergence of transgressive carbonate build ups (Mathew et al., 2020).…”

Offshore Evidence for an Undocumented Tsunami Event in the ‘Low Risk’ Gulf of Aqaba-Eilat, Northern Red Sea

“…Slumping events and slope failures disassociated to canyons are characterized by scars in the region where the failure occurs, and a mound feature marking the primary depositional area. Such features are not present on the surface at the north beach study site, nor are they described in the subsurface [ 40 ]. Similarly, at the Tur Yam site, the slope at the coring location is also around ~3°, and there are no morphological indications for slumping or failure.…”

Coral-reef records of Quaternary changes in climate and sea-level

“…Drowned reefs in the Gulf of Carpentaria (Harris et al 2008) apparently began their growth ~10.5 ka ago, sustained for some 2 000 yr, but by ~7−8 ka BP had virtually ceased to grow, unable to keep pace with rising sea-level. Hartman et al (2015), using high-resolution seismic reflection and multibeam bathymetry, were able to identify six distinct systems of fringing reefs embedded in the sediment cover in the Gulf of Aqaba. The most recent of these relate to two phases of growth since the last deglaciation, one between 12.8 and 11 5 ka, now A C C E P T E D M A N U S C R I P T…”