Multiproxy paleoaltimetry of the Late Oligocene-Pliocene Oiyug Basin, southern Tibet

Abstract

The stable isotope compositions of carbonate and organic samples from the Oiyug basin in southern Tibet allows for model calculations of the Oligocene to Pliocene paleoelevation of the south central Tibetan Plateau. We measured the oxygen isotope composition of pedogenic and lacustrine calcite, dolomite, and siderite, and the hydrogen isotope composition of n-alkanes from plant waxes to reconstruct the ␦ 18 O and ␦D values of Oiyug basin paleometeoric water. Calculated water isotope values from Oiyug basin carbonate and organic samples, respectively, are in close agreement, suggesting the preservation of an unaltered paleometeoric water isotopic signal in these archives. Late Oligocene-middle Miocene paleoelevation estimates from groundwater/ pedogenic calcite and lacustrine dolomite indicate basin elevations of 4.1 km ؉1.2/ ؊1.6 km. Plant-wax n-alkanes ␦D and lacustrine-siderite ␦ 18 O compositions of middle Miocene (ϳ15 Ma) samples indicate paleoelevations of 5.1 km ؉1.3/؊1.9 km. This estimated elevation is similar to the 5.4 km paleoelevation estimate based on fossilfloral physiognomy from the same stratigraphic interval. Calculated late MiocenePliocene paleoelevation estimates derived from the ␦ 18 O composition of lacustrine marls and carbonate/siderite concretions, as well as the ␦D from plant wax n-alkanes indicate a mean elevation of 5.5 km ؉1.4/؊2.0 km at ϳ5 Ma. Although calculated mean paleoelevations for the Oiyug basin all fall within the errors associated with the model calculations, the close agreement of the different paleoelevation proxies provides an additional degree of confidence in the fidelity of the calculated paleoelevations. Calculated paleoelevations indicate a possible increase in Oiyug basin elevations of ϳ1.4 km between the early and late Miocene. Given the modern Oiyug basin elevation of ϳ4.3 km, study results allow for a possible >1 km decrease in elevation since the early Pliocene. These findings, in conjunction with other Tibetan paleoaltimetry studies, are consistent with tectonic models supporting high elevations of the Tibetan Plateau since the initiation of India-Asia collision during the Eocene, and subsequent late Cenozoic extensional collapse.

Paleoaltimetry Potentiality of Branched GDGTs From Southern Tibet

“…MBT 0 5ME -MAT (8C) for the Gazhacun Fm (15 Ma) and Zhongdangcun Fm (10 Ma) from the Namling Basin, following soil calibrations based on Naafs et al (2017) and this study for the southern TP, compared with paleotemperature records of CLAMP from the Namling Basin and the global marine oxygen isotope records (Zachos, 2001). (Currie et al, 2016). Thus, we would propose that the paleoaltitude of the Namling Basin was close to its present mean altitude of 5.0 km asl before 15 Ma.…”

“…Noting the consistency of reconstructed paleoaltitudes based upon the floral physiognomy of Namling fossils, plant-wax n-alkanes dD and lacustrine-siderite d 18 O compositions (which appear to have grown at high altitudes of 4.7-5.4 km asl at 15 Ma; Currie et al, 2005Currie et al, , 2016Ding et al, 2017;Khan et al, 2014;Spicer et al, 2003), we selected Miocene samples from the Namling Basin to calculate lake water temperatures and reconstruct paleoaltitudes. Noting the consistency of reconstructed paleoaltitudes based upon the floral physiognomy of Namling fossils, plant-wax n-alkanes dD and lacustrine-siderite d 18 O compositions (which appear to have grown at high altitudes of 4.7-5.4 km asl at 15 Ma; Currie et al, 2005Currie et al, , 2016Ding et al, 2017;Khan et al, 2014;Spicer et al, 2003), we selected Miocene samples from the Namling Basin to calculate lake water temperatures and reconstruct paleoaltitudes.…”

“…The Namling Basin is located in the east-central Gangdese Arc, 60 km north of the Yarlung Zangbo Suture, and has an altitudinal range from 4.3 km asl at the Basin floor to >5.6 km asl in the surrounding mountains ( can be dated to an age range of 15.03-15.1 Ma (Currie et al, 2005(Currie et al, , 2016Spicer et al, 2003). The Zhongdangcun Fm is >700 m thick near Cuogejia Village, in the northernmost sector of the Namling Basin ( Figure 2b).…”

Asian Eocene monsoons as revealed by leaf architectural signatures

“…In the complex physiognomic space arising from large global data sets the predictive precision derived from such vectors is low compared to smaller data sets with a simpler calibration space (Yang et al, 2015). For enthalpy derived estimates of paleoaltitude this data set has been validated by multiple isotope studies (Currie et al, 2016).…”

Paleogene monsoons across India and South China: Drivers of biotic change

“…incorporates leaf trait spectra from vegetation exposed to monsoon climates in India and Thailand, and in terms of palaeoaltimetry has been validated against an array of stable isotope palaeoaltimeters (Currie et al, 2016). We compare the climates derived from our fossil material with those recorded in the leaf architecture of modern vegetation from India and South China, and examine these leaf trait spectra for different monsoon signatures using the global dataset of Yang et al (2015).…”