Rock varnish evidence for a Younger Dryas wet period in the Dead Sea basin

Abstract

[1] Rock varnish from 14.6 to 13.2 ka recessional shorelines of late glacial Lake Lisan and fan delta surfaces between 280 and 365 m bmsl (meters below mean sea level) along the western margins of the Dead Sea contains replicable layering patterns, characterized by a low Mn and Ba orange/yellow surface layer and a high Mn and Ba dark basal layer. The deposition of the dark basal layers immediately after the lake recession represents a wet period coinciding with the Younger Dryas (YD) cooling (12.9-11.6 ka), manifesting the influence of midlatitude westerly winds in the eastern Mediterranean-central Levant (EM-CL). In contrast, varnish from the distal base of fan deltas contains only orange/ yellow surface layers, diagnostic of the Holocene relatively dry climate. The absence of the dark basal layers in the varnish further indicates a YD high stand at~365 m bmsl and a lake level rise of at least 100 m from its Bølling-Ållerød lowstand. This rise stands in contrast to the abrupt drop of the lake level during the Heinrich (H1) cold event, illustrating the opposite response of the EM-CL climate to changes in the North Atlantic climate. The YD wet event most likely reflects a southward shift of the Atlantic meridional overturning circulation-modulated midlatitude westerly wind belt in the EM-CL region.

Hunted gazelles evidence cooling, but not drying, during the Younger Dryas in the southern Levant

“…1D; ref. 9) and the formation of a dark manganese and barium oxide desert varnish crust on the paleo-lakeshore pebbles (6). These results also help to resolve some discrepancies in recent reconstructions of the YD.…”

“…1). Vastly disparate interpretations of the environmental and climatic impact of the YD on the southern Levant have been proposed with some arguing for xeric and others for opposing mesic conditions (3)(4)(5)(6)(7)(8)(9)(10).…”

Nanoscale Observations Support the Importance of Chemical Processes in Rock Decay and Rock Coating Development in Cold Climates

“…The layering typical of clay minerals in HRTEM views of varnish [67] is being broken apart by the dissolution and then the reprecipitation of the Mn-rich granules into the clays-to the point where the layered texture is mostly lost (Figure 9c). These nanoscale movements do not create instability in the varnish laminations seen at the micron scale that are stable for tens of millennia [131][132][133]. Scale matters and these snanoscale movements would be analogous to cars shuffling in a parking structure composed of micron-scale laminations.…”

Inter-comparison of three-dimensional models of volcanic plumes

“…mass eruption rate was 1,000× that of the weak plume: 1.5× 10 9 kg s -1 (e.g., Suzuki and Koyaguchi, 2009). The atmospheric conditions were based on the reanalysis data obtained from European Centre for Medium-Range Weather Forecasts (ECMWF) by Costa et al (2013) for Pinatubo volcano at 13:40 PLT of 15 June 1991 (the profiles are shown in Fig. 1B in Costa et al, 2016).…”