The Tibetan Plateau; glaciation and loess deposition

Author(s): Rutter, N. W.; Rokosh, D.
Author Affiliation(s): Primary:
University of Alberta, Department of Earth and Atmospheric Sciences, Edmonton, AB, Canada
Volume Title: Role of Tibetan Plateau in forcing global climatic changes; selected papers presented at the symposium
Volume Author(s): Tandon, O. P., editor
Source: Journal of Himalayan Geology, 19(2), p.23-37; Symposium on the Role of Tibetan Plateau in forcing global climatic changes, Dharmsala, India, Oct. 26-31, 1996, edited by O. P. Tandon. Publisher: Wadia Institute of Himalayan Geology, Dehra Dun, India. ISSN: 0970-0951 CODEN: HMLGBX
Note: In English. 69 refs.; sects., geol. sketch maps
Summary: Faunal and floral evidence suggest that the Tibetan Plateau has been rising since Tertiary times and reached its maximum elevation sometime during the Quaternary. Although the area is presently tectonically active, radiometric dating on structural components suggest that the Plateau is controversial. Most geological evidence suggests that there were multiple glaciations but that ice extent was limited, confined to local mountains or uplands and, in some cases, minor ice sheets. Few agree that there was a major ice sheet over the entire Plateau. The timing of glacial events is poorly known because of a lack of absolute dates. Some have speculated that the more extensive, relatively early glacial activity was, in part, controlled by a lower elevation of the Plateau, allowing moisture to penetrate from the southwest. It appears that when the Tibetan Plateau reached a critical height at least 2.5 million years ago, loess deposition began in north-central China. The uplift caused, in part, a change in climate and atmospheric circulation, allowing for an almost complete record of loess deposition and soil development. The loess is sourced from deserts of north and northwest China and carried by northwest winds into the Loess Plateau. During relatively colder times wind velocity was stronger, resulting in higher loess accumulation and larger average grain size than during relatively warmer times. Loess deposition continues during inter glacials but at lower accumulation rates and with finer grain sizes, allowing soils to develop. Grain size variations are controlled largely by the position and intensity of the Siberian High. A grain size time scale was constructed at the Baoji section in the southern Loess Plateau back to 2.5 Ma, based on the timing of orbital variations (Milankovitch forcing), independent of the deep sea isotope records. From about 2.5 Ma to 1.67 Ma there is no clear dominance of any one orbital variation. From 1.67 to about 0.6 Ma the 41K obliquity signal dominates, whereas from 0.6 Ma to the present the 100K eccentricity is the major signal. Additionally, there is close climatic correlation between the Baoji grain size record and the DSDP Site 607 O profile from the North Atlantic for the last 1.67 Ma, implying a well-integrated, widespread climate system.
Year of Publication: 1998
Research Program: DSDP Deep Sea Drilling Project
IPOD International Phase of Ocean Drilling
Key Words: 24 Surficial Geology, Quaternary Geology; Asia; Atlantic Ocean; Cenozoic; China; Clastic sediments; DSDP Site 607; Deep Sea Drilling Project; Deposition; Far East; Glacial extent; Glacial geology; Glacial sedimentation; Glaciation; Himalayas; IPOD; Ice sheets; Leg 94; Loess; Mid-Atlantic Ridge; North Atlantic; Northeast Atlantic; Plateaus; Pleistocene; Quaternary; Sedimentation; Sediments; Tibetan Plateau; Uplifts; Xizang China
Coordinates: N270000 N370000 E0970000 E0720000
Record ID: 2012077327
Copyright Information: GeoRef, Copyright 2018 American Geosciences Institute. Reference includes data from Geoline, Bundesanstalt fur Geowissenschaften und Rohstoffe, Hanover, Germany