Ice cap erosion patterns from bedrock ¹⁰Be and ²⁶Al, southeastern Tibetan Plateau

Abstract

Quantifying glacial erosion contributes to our understanding of landscape evolution and topographic relief production in high altitude and high latitude areas. Combining in situ 10Be and 26Al analysis of bedrock, boulder, and river sand samples, geomorphological mapping, and field investigations, we examine glacial erosion patterns of former ice caps in the Shaluli Shan of the southeastern Tibetan Plateau. The general landform pattern shows a zonal pattern of landscape modification produced by ice caps of up to 4000 km2 during pre‐LGM (Last Glacial Maximum) glaciations, while the dating results and landforms on the plateau surface imply that the LGM ice cap further modified the scoured terrain into different zones. Modeled glacial erosion depth of 0–0.38 m per 100 ka bedrock sample located close to the western margin of the LGM ice cap, indicates limited erosion prior to LGM and Late Glacial moraine deposition. A strong erosion zone exists proximal to the LGM ice cap marginal zone, indicated by modeled glacial erosion depth >2.23 m per 100 ka from bedrock samples. Modeled glacial erosion depths of 0–1.77 m per 100 ka from samples collected along the edge of a central upland, confirm the presence of a zone of intermediate erosion in‐between the central upland and the strong erosion zone. Significant nuclide inheritance in river sand samples from basins on the scoured plateau surface also indicate restricted glacial erosion during the last glaciation. Our study, for the first time, shows clear evidence for preservation of glacial landforms formed during previous glaciations under non‐erosive ice on the Tibetan Plateau. As patterns of glacial erosion intensity are largely driven by the basal thermal regime, our results confirm earlier inferences from geomorphology for a concentric basal thermal pattern for the Haizishan ice cap during the LGM. © 2018 John Wiley & Sons, Ltd.

A GIS‐based multi‐proxy analysis of the evolution of subglacial dynamics of the Quebec–Labrador ice dome, northeastern Quebec, Canada

“…Kleman and Stroeven, 1997; De Angelis and Kleman, 2005; Davis et al ., 2006; Staiger et al ., 2006; Briner et al ., 2008; Refsnider and Miller, 2010), which were affected by sustained cold‐based subglacial conditions near an inferred stable ice‐divide centre. In studies that examine 10 Be abundances from different subglacial regimes, results with 10 times the abundance of 10 Be (when compared to nearby samples over glacially eroded terrain) are typically interpreted to reflect regions of sustained cold‐based conditions (Marquette et al ., 2004; Staiger et al ., 2006; Briner et al ., 2008; Fu et al ., 2018). Other studies utilizing the same methodology reported samples as low as 4 times the abundance of 10 Be to be indicative of sustained cold‐based regimes (Fable et al ., 2002; Briner et al ., 2014).…”

“…Other studies utilizing the same methodology reported samples as low as 4 times the abundance of 10 Be to be indicative of sustained cold‐based regimes (Fable et al ., 2002; Briner et al ., 2014). Intermediate or transition zones, between warm and cold‐based endmember categories, yield 10 Be abundances 1.4 to 4.2 times higher than surrounding warm‐based terrains (Li et al ., 2005; Staiger et al ., 2006; Fu et al ., 2018).…”

Southwestward growth of plateau surfaces in eastern Tibet

“…3C-E). These million-year-scale erosion rates roughly overlap with millennial-scale erosion rates of 0.02 ± 0.02 mm/yr, 0.03-0.04 mm/yr and 0.02-0.09 mm/yr for catchments draining the Zuogong 48 , Litang 49 and Kangding 50 plateaus, respectively.…”

“…In the Songpan-Garze-Yidun terranes, samples at high elevations (>4,000 m) and low relief ( 1D and 3A). Prolonged slow surface erosion, at rates of 0.01-0.03 mm/yr during the Cenozoic 15,[51][52][53] , in line with catchment-wide millennial erosion rates of <0.02-0.09 mm/yr 49,50 (Fig. 3), suggests that the low-relief landscapes in the Litang and Kangding plateaus were established before the India-Asia collision and maintained throughout most of the Cenozoic, consistent with little crustal thickening and exhumation 51 .…”

Glacial landscape and paleoglaciation in Terra Sabaea: Evidence for a 3.6 Ga polythermal plateau ice cap

“…These areas present evidence of paleoglaciation where an ice reservoir was at the origin of the valleys (Boule, 1896, Durand, 1939, Veyret, 1973, Valadas and Veyret, 1981, Derbyshire et al, 1991, Kuhle, 1998, Heyman et al, 2008, Fu et al, 2013a, Fu et al, 2018. The presence of depositional features such as moraines, kames, eskers, or kettles hole and features such as glacial lineation, scoured terrain, hummocky terrain and moraines indicate that these areas was covered by an ice cap at the highest elevation (Boule, 1896, Durand, 1939, Veyret, 1973, Valadas and Veyret, 1981, Derbyshire et al, 1991, Kuhle, 1998, Heyman et al, 2008, Fu et al, 2013a, Fu et al, 2018. Ice caps with cold-based regimes are weak agents of erosion compared to those with wet-based regimes.…”