Shoreline Evolution, Aeolian Deflation and Anhydrite Distribution of the Holocene, Abu Dhabi

Abstract

Easier access to most parts of the Abu Dhabi coastline, combined with satellite imagery, has enabled a more detailed examination of the Holocene strata than was possible twenty or thirty years ago. Whilst the basic principles of coastal progradations documented in those early days are still valid, they portrayed an oversimplified picture of the Holocene coastal geomorphology and sabkha sedimentology. New data re-emphasises the importance of antecedant topography in imposing depositional complexity on the Holocene System. Former Holocene shorelines can now be mapped with greater clarity and reveal its highly embayed nature. The Holocene transgressive limits are locally redefined. Some palaeo-highs, that formed earlier Holocene peninsulas, have been completely removed by deflation. Two phases of sabkha anhydrite are recognised and their distributions are largely predictable by remote sensing.

Extreme aridity prior to lake expansion deciphered from facies evolution in the Miocene Ili Basin, south‐east Kazakhstan

“…4B) around the groundwater table and in the capillary fringe of the S1 subfacies (Alonso Zarza, 2003). Morphologically, the sulphates in subfacies S2/S3 resemble those reported from landward areas of Arabian sabkhas (Butler, 1970;Butler et al, 1982;Warren & Kendall, 1985;Kirkham, 1997;Schreiber & El Tabakh, 2000) and are similar to sulphates found in saline mudflats surrounding playa lakes (Watson, 1985;Magee, 1991;Salvany et al, 1994;Ort ı & Rosell, 2000;Ort ı et al, 2014). According to these authors, sulphates in subfacies S2/S3 are interpreted as intra-sediment precipitates from rising groundwater brines, formed in the capillary fringe zone.…”

“…With further sulphate precipitation and volume increase, these layers are deformed to saucer‐like depressions with jacked‐up and eroded edges (Fig. F), similar to sulphate morphologies of the seaward areas of sabkhas (Butler, ; Butler et al ., , figs 18 to 20; Warren & Kendall, ; Kirkham, ). Occurrences of large gypsum lenses (Fig.…”

“…). The current study establishes a groundwater table, respectively a lake level, sensitive facies model that compiles diagnostic lithological features (Platt & Wright, ; Alonso Zarza et al ., ; Freytet & Verrecchia, ) and observations of evaporite morphology and mineralogy in comparison to modern and fossil examples of playa and sabkha evaporites (Hardie et al ., ; Butler et al ., ; Magee, ; Salvany et al ., ; Kirkham, ; Arenas & Pardo, ; Ortí & Rosell, ; Schreiber & El Tabakh, ; Ortí et al ., ). This model is able to: (i) characterize evaporite formation and early diagenesis at different water levels; (ii) identify periods of water mass accumulation and evaporite precipitation; and (iii) finally reconstruct the hydrological evolution of the basin.…”

Challenges to carbonate-evaporite peritidal facies models and cycles: Insights from Lower Cretaceous stromatolite-bearing deposits (Oncala Group, N Spain)

“…In the same way, the peritidal facies of Abu Dhabi are not arranged as shore-parallel belts, but show a much more intricate arrangement (see facies maps in Purser and Evans, 1973;Wagner and van der Togt, 1973;Kirkham, 1997;Alsharhan and Kendall, 2003), which results of an intricate system of subtle bathymetric highs and lows superimposed upon the regional slope (Kendall and Skipwith, 1969;Wagner and van der Togt, 1973;Riegl et al, 2010), as well as variations in the orientation to strong NW winds and in the inclination of the regional slope J o u r n a l P r e -p r o o f (Riegl et al, 2010). This mosaic facies distribution is also reflected in the vertical facies stacking patterns.…”

“…4B). Several authors consider that these erosive surfaces in ancient deposits constitute an unequivocal evidence that anhydrite precipitation occurred shortly after deposition in a sabkha environment, and was not produced by the burial conversion of gypsum to nodular anhydrite as occurs in other ancient successions (see Warren and Kendall, 1985;Warren, 1991;Kirkham, 1997;Alsharhan and Kendall, 2003;Warren, 2016). This makes the studied peritidal deposits one of the best examples of true coastal sabkha-type successions in the geological record, contrasting with many ancient sequences that have been misinterpreted as sabkha deposits just due to the presence of nodular anhydrite (see Warren, 2016, p. 250).…”