Arabian Peninsula Wet Periods - a note

 My last note discussed Marine isotype Stages (MIS). These provided a dated measurement of glacial (dry climate) and interglacial (wetter) periods over extended time periods. The most relevant time periods from our perspective are summarised below 

"MIS 4 – 71

MIS 5 – 130, usually sub-divided into a to e:

MIS 5a – 82 (peak of interglacial sub-stage)

MIS 5b – 87 (peak of glacial sub-stage)

MIS 5c – 96 (peak of interglacial sub-stage)

MIS 5d – 109 (peak of glacial sub-stage)

MIS 5e – 123 (peak of Last Interglacial, also known as the Eemian among other names)

MIS 6 – 191 (Penultimate Glacial Period, also called Illinoian glacial in North America, later Saalian in northern Europe and later Wolstonian in Britain)

MIS 7 – 243 (Aveley Interglacial in Britain)"

If the Aboriginal ancestors came out of Africa they would have had to travel through the Arabian Peninsula. But was that possible? The work of Abi Stone et al (2023) suggest that it was.

Abstract:

"Past environmental and climatic conditions within the Arabian Peninsula are key to understanding the setting for hominin dispersal across the Saharo-Arabian dryland belt. The tufa deposits within the volcanic harrats on the southwest coast of Saudi Arabia fill a significant spatial gap in the distribution of palaeoenvironmental records on the west coast of the Arabian Peninsula adjacent to the Red Sea. In the catchment of Wadi Dabsa in the Harrat Al Birk, there are widespread fossil palustrine to shallow-lacustrine tufa deposits with fluvial elements. Several phases of tufa accumulation, separated by fluvial downcutting, are observable within these powerful palaeoenvironmental proxies. U–Th dating of targeted dense, banded tufa facies, yield ages that are stratigraphically consistent at the landscape scale, and indicate that tufa accumulation occurred during distinct humid phases broadly coeval with the last two warm interglacial Marine Isotope Stages (MIS 7 and MIS 5). For the first time this shows humid intervals in southwest Arabia coincident with the southern coast. There is a similar pattern emerging further north in the Arabian Peninsula, The Sinai and Levant and further on into continental Europe. Furthermore, tufa δ18O ranges from −14.6 to −1.9‰, covering a range similar to those reported for tufa from north African oasis sites and speleothems elsewhere on the Arabian Peninsula and The Levant. The lowest δ18O values are derived from MIS 5e samples, a pattern in agreement with speleothems in Yemen and Oman, and consistent with an isotopic-enabled climate model simulation for this time slice. The δ13C and Sr isotopic compositions of dated tufa samples indicate deposition from shallow-circulating meteoric water, with no geothermal influence. This, along with the δ18O values, suggest a freshwater supply that was a potable water source in this landscape. The δ13C signatures at Wadi Dabsa are more negative than for parts of north Africa, suggesting Wadi Dabsa may have experienced comparatively higher biomass, thicker soils and wetter conditions with lower evaporative losses. This new record of tufa deposition during the middle and late Pleistocene, suggests for the first time that the west coast of Arabia experienced a similar history of humid phases over the past 250 ka as southern Arabia and the Nefud in the northern interior. These regional changes in hydroclimatic regime occur at timescales coincident with hominin dispersals." Abi Stone, Robyn H. Inglis, Ian Candy, Diana Sahy, Anne-Lise Jourdan, Dan N. Barfod, Abdullah M. Alsharekh, “Humid phases on the southwestern Arabian Peninsula are consistent with the last two interglacials”, Quaternary Science Reviews, Volume 319, 2023, https://doi.org/10.1016/j.quascirev.2023.108333 

Comment

The warmer wet periods suggested by the analysis do appear to fit with an out of Africa date of 72000 kya (MIS 5). An earlier date might also be possible to fit with MIS 7 should the present latest date for occupation within Sahul (c65,000 kya) be pushed back.