Reconstructing Permafrost Sedimentological Characteristics and Post-depositional Processes of the Yedoma Stratotype Duvanny Yar, Siberia

Abstract

Cryogenic weathering is a key driver of periglacial sediment composition and properties. Selective mineral-grain weathering caused by freeze-thaw cycles in permafrost environments has the ability to dominate this process, leading to silt-rich grain-size distributions. The cryogenic weathering index (CWI) is a promising tool to quantify cryogenic weathering and freezing conditions. It considers the low resistance of quartz to freeze-thaw cycles compared to feldspars. Using this approach, this study aims to decipher post-depositional weathering by reconstructing cryogenic late Pleistocene Yedoma origins of the Yedoma stratotype exposure Duvanny Yar. To estimate the recent environmental endmember and to determine the initial mineral composition of sediment until freezing, the distribution of CWI in the active layer was studied. In addition to CWI, we studied mineral composition, heavy mineral distribution, grain size distribution and grain morphology. We suggest that cryogenic weathering likely altered polygenetic deposits (fluvial, nival, colluvial, lacustrine, alluvial, and aeolian processes) during sediment and ground ice accumulation. Moreover, we found two CWI distribution peaks in the late Pleistocene - Holocene sediments at the boundaries between glacial and interglacial ages. In conclusion, we see that the Duvanny Yar sediment facies varied by CWI, but also with grain-size distribution, suggesting environmental changes during formation. Nevertheless, post-depositional processes like cryogenic weathering have influenced sediment characteristics and should be considered in paleoenvironmental reconstructions.

Interrelationships among mountain relief, surface organic layer, soil organic carbon, and its mineral association under subarctic forest tundra

“…The average SOC concentration on the steep, forest-covered slopes of Bucharama Valley reached 5.2%, slightly more than the values of 4.6% on the mountain tundra plots on the western edges of the plateau 36 and 4.7% in a low-Arctic site (64°N) featuring relatively flat topography and sparse spruce forest cover but less than the values of 7.6% and 11.7% in sites at considerably lower (58°N) and higher (75°N) latitudes 60 . The average 2.15% SOC concentration on gentler slopes of Malyj Orokan was noticeably lower than that in all the other localities but was comparable to the value of 2.6% in the gently undulating Siberian Yedoma sediments with a SOL thickness of 30–50 cm 61 , 62 .…”

An Update on Eukaryotic Viruses Revived from Ancient Permafrost

“…The various on-site sampling protocols have been previously described in [ 31 , 43 ] for samples #3 and #5 (collected in the spring 2015), in [ 13 , 44 ] for sample #4, in [ 45 ] for sample #6, and [ 46 , 47 ] for samples #7–9 (see Table 1 ).…”

An update on eukaryotic viruses revived from ancient permafrost

“…The various on-site sampling protocols have been previously described in [28, 40] for samples #3 and #5 (collected in the spring 2015), in [41] for sample #4, in [42] for sample #6, and [43, 44] for samples #7-9 (see Table 1). Liquid sample #2 and #4 were collected in pre-sterilized 50 ml Falcon tube in august 2019, as well as sample #1 consisting of surface soil without vegetation from the Shapina river bank collected on 07/15/2017 and since maintained frozen at −20 C in the laboratory.…”