Were springline carbonates in the Kurkur–Dungul area (southern Egypt) deposited during glacial periods?

Abstract

The tufa deposits in the Kurkur–Dungul area, southern Egypt, date from marine isotope stage (MIS) 11 to MIS 1. Springs across the region were active during glacial periods (with sea-level below –50 m), reflecting changed atmospheric circulation over the Indian Ocean, as well as peak interglacial periods. During times of low sea-level, reduced Indonesian throughflow promoted formation of an Indian Ocean Warm Pool, and anomalous rainfall on its western margin. We suggest that Egypt lies at the intersection of westerly (‘maghrebian’) and easterly (‘mashriqian’) rainfall provinces, which show different timing with relation to orbital forcing and different source water regions. Tufa-growth periods are therefore not mechanistically linked to ‘humid periods’ or ‘sapropel events’ identified elsewhere. Stable isotope and T(Δ47) data are also inconsistent with these spring systems being part of a larger system spanning northern Africa, and lack a clear interaction between northern hemisphere heating and mid-latitude rainfall. We also follow previous researchers in concluding that formation of springline deposit formation was probably delayed compared with rainfall, owing to aquifer flow distances. This delay is unlikely to be sufficient to explain why rainfall is out of phase with movements of the monsoon belts, but may complicate interpretation of these records.Supplementary material: A lithofacies description and supplementary figures and tables are available at https://doi.org/10.6084/m9.figshare.c.5246661

Facies and early diagenesis of rainwater-fed paleospring calcareous tufas in the Kurkur oasis area (southern Egypt)

“…The tufa sites 1 to 4 are located at the lower erosional surfaces along the Nubian plain, the downstream of Wadi Abu Gorma and the scarp face of the Sinn El-Kaddab Plateau, whereas the tufa sites 5 to 7 are located at relatively higher elevations along the upstream of Wadi Abu Gorma and the surface of the Sinn El-Kaddab Plateau. Using U − Th age data, Jimenez (2014) and Kele et al (2021) dated the Kurkur tufas between 326 ± 14 ky for the older tufas at the higher levels, and 139 ± 11 ky for the younger tufas at the lower levels.…”

“…This can take place in a wide variety of depositional settings (e.g. Pedley 1990;Ford and Pedley 1996;Das and Mohanti 2005;Gandin and Capezzuoli 2008;Arenas et al 2014;Nicoll and Sallam 2017; Rodríguez-Berriguete 2020; Kele et al 2021). Tufa formation is most likely associated with karstification processes and later carbonate precipitation in fluvial and springfed systems (e.g.…”

“…Tufas are characterized by highly porous textures with poor stratification and by elongated shapes, and commonly contain abundant remains of macrophytes (marginal pond plants such as reeds, rushes and shrubs) and microphytes (tiny plants or photosynthetic organisms such as cyanobacteria, epiphytes and diatoms) that are coated by calcium carbonates (e.g. Ford and Pedley 1996;Arenas et al 2000Capezzuoli et al 2014;Nicoll and Sallam 2017;Kele et al 2021;Sallam and Abou Elmagd 2021). Tufas are, like most terrestrial carbonates, very sensitive to environmental and and climatic fluctuations during their origination (e.g.…”

“…These tufas have characteristic textures resulting from complex interactions between organic and physiochemical processes during both precipitation and early diagenesis (e.g. Sultan et al 1997;Hassan 2014;Nicoll and Sallam 2017;Sallam and Ruban 2019;Kele et al 2021). Gaber et al (2018) dated these tufas as Pleistocene for the older, upper levels (~ 345 m a.s.l.)…”

“…Crombie et al (1997) and Gaber et al (2018) indicated that the older tufas at the higher topographic levels were formed under warm pluvial conditions, whereas the younger tufas in Wadi Kurkur and at the bottom of the oasis were formed under drier conditions. Kele et al (2021) documented that the tufas in the Kurkur-Dungul area originated from paleosprings that were active during glacial periods with low sea-level (below-50 m), and these tufas date between 368 ± 14 and 11.7 ± 1.2 ka (from marine isotope stage (MIS) 11 to MIS 1).…”