Attila Çiner

Soft-sediment deformation structures (SSDS) in water-saturated, unconsolidated sediments are the product of various causes and provide a valuable record of environmental and geological perturbations. We report a record of SSDS preserved in a ∼166 m-long drill core (DX-2) extracted from the Late Pleistocene Diexi Palaeolake, eastern Tibetan Plateau. Two factors make this an outstanding site for studying SSDS: (1) it is among the most seismically active regions on Earth, and (2) it has experienced extremely fast sedimentation rates (∼15 mm/yr) thanks to the prodigious sediment supply from seismically perturbed hillslopes and rivers upstream. We describe and interpret 13 SSDS types within the DX-2 based on detailed sedimentological, morphological, and lithological analysis. We consider the genesis of the abundant SSDS observed in the DX-2 core with several possibilities: mass movement, rock avalanche-driven tsunamis, rapid sedimentation, and seismic shaking as the most probable triggering mechanisms. We suggest high-intensity earthquakes of VI (Modified Mercalli Intensity) or greater as drivers of SSDS in the DX-2. Based on our observations, we propose a conceptual model that attempts to explain the transition from ductile to brittle SSDS behaviour with progressive accumulation and consolidation of the sediment pile. This paper highlights the value of SSDS analysis in palaeo-earthquake identification, aiming to improve the applicability of SSDS as a palaeo-earthquake marker in alpine and canyon areas.

The hypersaline Urmia Lake in NW Iran offers unique sedimentary environments sensitive to climate and environmental shifts, fostering coated grain formation and serving as a vital indicator of paleoenvironmental conditions. This study characterizes coated grains within a 25‐m sediment core dating back to ~50 cal ka bp, assessing their significance through morphology, internal structures, mineralogy, and geochemistry. Coated grains in Urmia Lake exhibit concentric laminations, primarily calcite and aragonite, revealing alternating light carbonate‐rich and dark organic‐rich laminations. These reflect seasonal and long‐term variations in water chemistry and biogenic production. Dry season algal blooms contribute to lamination, highlighting the interplay between seasonal climate fluctuations and the consequent lake water enrichment in calcium, carbonate, and bicarbonate ions. The diversity and abundance of coated grains indicate three main lake level fluctuation stages in the last ~50 cal ka: a lowering stage with dominant coated grains, a low lake level with dominant terrigenous fragments and minerals, and a high lake level with prominent Artemia urmiana fecal pellets. The role of the brine shrimp A. urmiana in coated grain formation involves absorbing calcium, carbonate, and bicarbonate ions and inhibiting coated grain formation during high lake levels while providing nuclei during lake lowering. An in‐depth investigation of coated grains provides a chemical and biological formation framework, highlighting three main episodes in the lake's history.

Several mountains in Turkey were glaciated during the Late Pleistocene. One of them, Mt. Aladağ, is located in the central Taurus Range and covers an area of 800 km2. The elevation changes from 400 to 3771 m asl, making the mountain one of the most profound karst systems in the world. It is limited by several outwash fans, cut and offset by the left-lateral Ecemiş Fault Zone on the west, Zamantı River on the east, and Mt. Karanfil on the south. Two major local ice caps >3000 m asl, on Yedigöller and Körmenlik Plateaux, occupied the summits of Mt. Aladağ in the past. Although several glacier tongues derived from these ice caps and deposited moraines and outwash fans, today, only a few debris-covered glaciers and rock glaciers are left. We used the cosmogenic 36Cl surface exposure dating method on limestone bedrock, moraine and outwash fan boulder samples to constrain the timing of paleoglaciations. A total of 121 samples indicate several episodes of deglaciation during the last glacial cycle. The oldest moraines (~47 and ~38 ka old) are found in the W-NW of Mt. Aladağ in two adjacent valleys. An outwash fan (~78 ka) at the exit of the northern valley also indicates the existence of earlier glacial conditions, also confirmed by previous outwash fan ages obtained from the SW of the mountain. The highest peaks (>3200 m) became ice-free by ~55 ka, but two ice caps remained active till the onset of the Holocene. Interestingly, the Last Glacial Maximum (LGM; ~21 ka) moraines are rare and only preserved at high altitudes. On the other hand, the longest paleoglacier (>15 km) of Mt. Aladağ, on the eastern side, rapidly retreated from ~15 ka to ~12.5 ka, indicating Late Glacial to Younger Dryas deglaciation. Additionally, Early Holocene moraines are found in eastern and western valleys abundantly.On the other hand, Mt Karanfil (3059 m asl), a small mountain 20 km south of Mt. Aladağ, contains four well-preserved terminal and lateral moraine complexes, each originating from one to three cirque areas from the mountain’s N-NW face. The mean ages of moraines range from ~17 ka to ~19 ka, indicating mostly an LGM deglaciation. One sample from a relict rock glacier in a cirque floor was dated to ~10 ka, testifying to the development of permafrost conditions on the onset of Holocene. We also used the Parallel Ice Sheet Model (PISM) to reconstruct the glaciers and climate during the LGM on Mt. Karanfil. We ran 21 paleoclimate simulations as a function of present temperature and precipitation to reach the steady‐state glacier extents and compared the results with the modelled glacial areas and the field‐observed ice extents. The best‐fit setups imply that Mt. Karanfil’s LGM climate was 8.3 ± 0.5 oC colder than today if the precipitation levels were the same as today. More humid (20% wetter) or arid (20% drier) conditions produce paleotemperatures 6.9 ± 0.4 oC or 10.4 ± 0.6 oC lower than today, respectively. Financial support by TÜBİTAK 116Y155 and ANSTO (AP11366) projects are greatly acknowledged.