Browsing by Author "Ding, Lin"

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The Ancestral Lhasa River: A Late Cretaceous trans-arc river that drained the proto-Tibetan Plateau
(2019-09-19) Laskowski, Andrew K.; Orme, Devon A.; Cai, Fulong; Ding, Lin
Late Cretaceous trench basin strata were deposited in the subduction zone that consumed Neo-Tethyan oceanic lithosphere along the southern margin of the proto–Tibetan Plateau. We conducted detrital zircon (DZ) U-Pb geochronology on six trench basin samples (n = 1716) collected near Dênggar, Tibet (∼500 km west of Lhasa), to assess the provenance of these rocks and reconstruct Late Cretaceous sediment transport pathways. They contained DZ ages that point to a unique source around Lhasa city, north of the Late Cretaceous Gangdese magmatic arc. The modern Lhasa River catchment contains the requisite sources, and its main trunk transects the Gangdese magmatic arc, joining with the Yarlung River at a barbed junction at the India-Asia suture. We infer that the Lhasa River is an ancient feature that transported sediment to the subduction zone in Late Cretaceous time and persisted during India-Asia collision.
Configuration and Timing of Collision Between Arabia and Eurasia in the Zagros Collision zone, Fars, Southern Iran
(American Geophysical Union, 2021-08) Cai, Fulong; Ding, Lin; Wang, Houqi; Laskowski, Andrew K.; Zhang, Liyun; Zhang, Bo; Mohammadi, Ali; Li, Jinxiang; Song, Peiping; Li, Zhenyu; Zhang, Qinghai
The configuration and timing of the Arabia-Eurasia continental collision, part of the broader Alpine-Himalayan collisional system, remains controversial. We conducted sandstone petrology, detrital zircon U-Pb-Hf isotopic and trace element analysis, and Cr spinel electron microprobe geochemical analysis of samples from Paleocene to Miocene peripheral foreland strata in interior Fars, southern Iran. These data were used to test competing models for ophiolite obduction and Arabia-Eurasia collision. In addition, we applied these data to compare the history of outward and upward growth of the Zagros and Himalayan-Tibetan segments of the Alpine-Himalayan collisional orogenic belt. The first appearance of radiolarian-rich chert conglomerate, 100–90 Ma detrital zircons with positive ɛHf(t) values from +1 to +20 and midocean ridge geochemical affinity, and suprasubduction zone (SSZ) affinity Cr-spinel is in the lower and middle Sachun Formation. These data indicate that obduction occurred before deposition of the upper Maastrichtian-lower Paleocene Sachun Formation and developed in an intra-oceanic setting rather than an Arabia-Eurasia collision setting. Abundant continental-arc affinity detrital zircon with 180–160 Ma and 50–27 Ma age-probability peaks and varied ɛHf(t) values are present in the upper Oligocene-lower Miocene Razak and Agha Jari formations, indicating sedimentary overlap with Eurasia. SSZ-affinity Cr-spinel in all samples indicates that ophiolitic rocks were a continual source of detritus in the foreland basin since Paleocene. The depositional age of the basal Razak Formation is between 25.7 and 21.5 Ma. Therefore, we interpret that collision between Arabia and Eurasia must have been initiated before deposition of the Razak Formation.
Episodic Late Cretaceous to Neogene crustal thickness variation in southern Tibet
(Wiley, 2023-10) Sundell, Kurt E.; Laskowski, Andrew K.; Howlett, Caden; Kapp, Paul; Ducea, Mihai; Chapman, James B.; Ding, Lin
Recent advancements in quantitatively estimating the thickness of Earth's crust in the geologic past provide an opportunity to test hypotheses explaining the tectonic evolution of southern Tibet. Outstanding debate on southern Tibet's Cenozoic geological evolution is complicated by poorly understood Mesozoic tectonics. We present new U-Pb geochronology and trace element chemistry of detrital zircon from modern rivers draining the Gangdese Mountains in southern Tibet. Results are similar to recently published quantitative estimates of crustal thickness derived from intermediate-composition whole rock records and show ~30 km of crustal thinning from 90 to 70 Ma followed by thickening to near-modern values from 70 to 40 Ma. These results extend evidence of Late Cretaceous north–south extension along strike to the west by ~200 km, and support a tectonic model in which an east–west striking back-arc basin formed along Eurasia's southern margin during slab rollback, prior to terminal collision of India with Eurasia.
Field Report: Research along the Yarlung Suture Zone in Southern Tibet, a persistent geological frontier
(2018-03) Laskowski, Andrew K.; Ding, Lin; Cai, Fulong; Chen, Yaofei; He, Songlin
The Yarlung Suture Zone in Southern Tibet marks the boundary between India and Asia–formerly separated by an ocean basin–and is a critical record of the tectonic processes that created the Tibetan Plateau. The Yarlung Suture Zone is also a frontier research area, as difficulty of access has limited research activity, providing ample opportunities for new discoveries. This paper documents field research conducted by the authors along the Yarlung suture zone in eastern Xigaze (Shigatse, Rikaze) County, ∼250 km west of the city of Lhasa, in July 2017. The goal of this research was to map the Suture Zone structure in detail, and more specifically to understand the branching relationships between two major fault systems—the Great Counter Thrust and Gangdese Thrust. A summary of early geological exploration is included to provide context for this research.
New Paleomagnetic Constraints on the Early Cretaceous Paleolatitude of the Lhasa Terrane (Tibet)
(Frontiers Media SA, 2022-05) Li, Zhenyu; Ding, Lin; Laskowski, Andrew K.; Burke, William B.; Chen, Yaofei; Song, Peiping; Yue, Yahui; Xie, Jing
New zircon U-Pb dating results from the Zonggei Formation volcanics indicate that the volcanic rocks formed at ∼114–110 Ma. Paleomagnetic data, petrography, and rock magnetism confirm the primary nature of isolated characteristic remanent magnetizations carried by titanomagnetite and hematite. A statistical analysis of the combined results from the Zonggei and Duoni formations reveals a group-mean direction of D±ΔD = 0.4° ± 6.0°, I±ΔI = 22.2° ± 5.6°, α95 = 5.6°, k = 35.2 after bedding correction based on 20 group-mean directions. The corresponding paleopole was calculated to be λp = 70.3°N, φp = 270.5°E with A95 = 5.2°. The interpretation of our data alongside the Cenozoic data from the Tethyan Himalaya indicates that the India–Asia collision initiated by 61.7 ± 3.0 Ma at 13.0° ± 1.8°N, assuming a single-collision model. Intracontinental crustal shortening totaling 1,770 ± 470 km took place on the Asian side since the onset of India–Asia collision. Furthermore, the data show that the Neo-Tethys Ocean reached its maximum N-S width of 7,100 ± 530 km at ∼132 Ma and shrank to 6,400 ± 550 km by ∼115 ± 5 Ma. This is consistent with previous estimates based on the geophysical images of the subducted Neo-Tethyan slab beneath Eurasia.
Provenance analysis of Cretaceous peripheral foreland basin in central Tibet: Implications to precise timing on the initial Lhasa-Qiangtang collision
(Elsevier BV, 2020-01) Chen, Yaofei; Ding, Lin; Li, Zhenyu; Laskowski, Andrew K.; Li, Jinxiang; Baral, Upendra; Qasim, Muhammad; Yue, Yahui
Mesozoic strata along northern margin of the Lhasa terrane near Dingqing, Tibet provide a semi-continuous record of the Bangong-Nujiang Ocean closure and the subsequent Lhasa-Qiangtang collision. In this study, we present results of sandstone petrographic, detrital zircon Usingle bondPb, and Cr-spinel geochemical data to determine the provenance of the Mesozoic strata (from the Triassic Quehala Group and the Mid-Jurassic to Lower Cretaceous Xihu, Lagongtang, and Duoni Formations, which are young from ~220 Ma to ~100 Ma) in this region, thereby allowing for interpretation of their tectonic setting. The similar 1200–900 age cluster from the lower Xihu Formation to that of the Triassic Quehala Group and the distinct age peaks at ~200 Ma and ~146 Ma from the upper Xihu Formation suggest a Lhasa terrane provenance to the south. Distinctive age clusters of 300–210 Ma and ~1800 Ma and Cr-spinel composition analysis of the Lagongtang Formation indicate a provenance shift from the Lhasa terrane to the Qiangtang terrane and the Bangong-Nujiang suture zone to the north. The Lagongtang Formation was deposited in a bathyal-abyssal to shallow-slope environment from north to south, that we interpret as the foredeep depozone and distal foredeep of a peripheral foreland basin system that developed due to flexural subsidence related to the Lhasa-Qiangtang collision and terrane accretion. The age of the Lhasa-Qiangtang collision is constrained by a ~140 Ma tuffite Usingle bondPb age at the base of the foreland basin strata. An angular unconformity between the Xihu and Lagongtang Formation, which we interpret as the result of the Lhasa-Qiangtang collision. Our results indicate that the Lhasa-Qiangtang collision initiated around ~140 Ma in the Dingqing region, simultaneously with previous determinations 1200 km to the west near Gaize area. Therefore, we prefer quasi-simultaneous onset of collision along-strike to zippering collision models wherein the east collision age is older than the west.
Record of Crustal Thickening and Synconvergent Extension from the Dajiamang Tso Rift, Southern Tibet
(MDPI AG, 2021-05) Burke, William B.; Laskowski, Andrew K.; Orme, Devon A.; Sundell, Kurt E.; Taylor, Michael H.; Guo, Xudong; Ding, Lin
North-trending rifts throughout south-central Tibet provide an opportunity to study the dynamics of synconvergent extension in contractional orogenic belts. In this study, we present new data from the Dajiamang Tso rift, including quantitative crustal thickness estimates calculated from trace/rare earth element zircon data, U-Pb geochronology, and zircon-He thermochronology. These data constrain the timing and rates of exhumation in the Dajiamang Tso rift and provide a basis for evaluating dynamic models of synconvergent extension. Our results also provide a semi-continuous record of Mid-Cretaceous to Miocene evolution of the Himalayan-Tibetan orogenic belt along the India-Asia suture zone. We report igneous zircon U-Pb ages of ~103 Ma and 70–42 Ma for samples collected from the Xigaze forearc basin and Gangdese Batholith/Linzizong Formation, respectively. Zircon-He cooling ages of forearc rocks in the hanging wall of the Great Counter thrust are ~28 Ma, while Gangdese arc samples in the footwalls of the Dajiamang Tso rift are 16–8 Ma. These data reveal the approximate timing of the switch from contraction to extension along the India-Asia suture zone (minimum 16 Ma). Crustal-thickness trends from zircon geochemistry reveal possible crustal thinning (to ~40 km) immediately prior to India-Eurasia collision onset (58 Ma). Following initial collision, crustal thickness increases to 50 km by 40 Ma with continued thickening until the early Miocene supported by regional data from the Tibetan Magmatism Database. Current crustal thickness estimates based on geophysical observations show no evidence for crustal thinning following the onset of E–W extension (~16 Ma), suggesting that modern crustal thickness is likely facilitated by an underthrusting Indian lithosphere balanced by upper plate extension.