Quaternary tipping points in the sedimentological system of the Orog Nuur catchment (S-Mongolia) – First results
P 3.7 in Interplay of endogenous and exogenous processes, climate change, and their feedbacks
The evolution of landscape systems (mountain ranges – catchments – lake basins) are subjected to the effects of different ‘tipping points’. Before and after such inherent thresholds, geomorphological processes affect landscape change differently. For example, fluvial dynamics control lake status, which in turn control the sediment availability for the aeolian system. Identifying and evaluating tipping points in regard of landscape systems is a key task in the BMBF-CAME II program “Q-TiP”.
In the tectonically active, (semi-)arid catchment of the Orog Nuur basin in the South Mongolian Gobi Desert, sedimentological and chronological studies investigate the behavior of sediment cascades under the influence of potential climatic and tectonic tipping points. Unpublished results from a previous project will be reclaimed and upgraded by additional field work and sampling (summer 2017). Sediment archives, such as alluvial and lacustrine deposits, dunes and aeolian mantles will be dated to establish a chronologic framework around sedimentological and tectonic tipping points.
The Lake Orog is hosted by a catchment of about 12.000 km2. Previous studies on lake sediment cores and terrestrial sections indicate high lake levels during the MIS 3 (~70-35 ka). Lake desiccation is indicated by sand layers during most of the MIS 2 and the Younger Dryas. Previous observations indicate climate driven alluvial fan aggradation during glacials and incision phases in interglacial periods. The sedimentological perspective suggests different aggradation modes (debris-flow controlled vs. sheet-flow controlled) between high-glacial (~20 ka) and late glacial (~13 ka) fanglomerates. This cyclic alluvial fan behavior appears to have been active already during the penultimate glacial, but needs more evidence for validation in regard of its tipping point character. Aeolian mantles are widespread in the study area and have mainly been deposited since the late Glacial / early Holocene. However, chronologically and spatially resolved proxy variations (grain size, geochemistry) have not yet been investigated and linked to other archives (e.g. alluvial fans; lake record). Thus, the sedimentological link between lake levels, aeolian deposits, alluvial fans and river terraces are investigated in regard of climatic and non-climatic (i.e. tectonic) tipping points and in order to support the understanding of landscape systems.