OSL-dated, dune-dammed waterbody sediments along dunefield fringes improves resolution and reliability of dunefield evolution chronologies

Several studies demonstrated that >~100 absolute ages of sand at certain spatial/vertical resolutions are required for constructing a reliable chronological framework for palaeoenvironmental and palaeoclimatic interpretations of dunefield construction (Telfer and Hesse, 2013). As acquiring abundant absolute ages demands significant field and lab resources, several methodological approaches, such as port-OSL-OSL age estimates, have attempted to partly overcome this necessity (Stone et al., 2019).

Arid-zone encroaching dunes in the past and present, often dam drainage systems and generate proximal upstream, dune-dammed waterbodies that when dry, form playas. These waterbodies that are often seasonal, deposit distinct, low-energy, fluvial, fine-grained sediments (LFFDs), often as couplets. This recurring aeolian-dominated aeolian-fluvial (AF) process gradually leads to amplified LFFD accumulation, and partly configures dunefield, and particularly dunefield margin landscape evolution.

The INQUA DuneAtlas of global dunefield chronological data includes some dated samples that are non-dune sediments such as interdune and LFFD samples. However, the complementary contribution of such sediments to interpreting dunefield chronologies has not been fully assessed (Lancaster et al., 2016). Furthermore, and surprisingly, DuneAtlas dune sand samples that date to the LGM are sparse. We demonstrate that OSL ages, partly supported by port-OSL profiling, mainly of sandy units within LFFDs, improves the resolution and reliability of dating dunefield construction events and morphological maintenance of existing dunes, and in some cases even reveals periods of dune mobilization that are absent in dated dune cores.

Spatially dense, OSL-dated dune cores and sections of the ~10³ km² sized northwestern Negev dunefield (Israel) study area, revealed that the dunefield was constructed in two main sand incursion and vegetated linear dune (VLD) buildup/extension periods during the Heinrich 1 (H1) and Younger Dryas (YD) (Roskin et al., 2011; Thomas and Bailey, 2019). In this study, exposed, OSL-dated LFFD sections along the dunefield margins revealed that dune-dammed waterbodies destroyed earlier dunefield-margin dunes, partly erode others, but also preserve remains of eroded dunes between LFFD units. The LFFD sections revealed for the 1^st time, significant and initial dune incursion and damming during the LGM, and also LFFD deposition thru the early Holocene (Robins et. al., 2022, 2023). The extent and relative thickness of H1-dated LFFDs suggest that dune encroachment then was greater than during the YD of the climate may have been slightly wetter. Early Holocene sediments may imply partial dune buildup or equilibrium-like dune maintenance in the early Holocene and, or also, a lag between YD dune-damming and later fluvial dune-breaching - when LFFD stratigraphic buildup gradually neared dune crest elevation leading to an outburst flood.

Altogether, studying and dating dune-dammed LFFDs are proposed to not only be a complementary, but rather a primary approach to date dunefield evolution and interpret past forcing drivers of sand mobilization and stabilization, and palaeohydrology.

 

References

Lancaster, N., et al., 2016. QI 

Robins, L., et al., 2022. QSR 

Robins, L., et al., 2023. QSR

Roskin, J., et al., 2011. QSR 

Stone, A. et al. 2019. QG 

Telfer, M.W. and Hesse, P.P., 2013. QSR 

Thomas, D.S. and Bailey, R.M., 2019. AR