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A Cretaceous‐Eocene depositional age for the Fenghuoshan Group, Hoh Xil Basin: Implications for the tectonic evolution of the northern Tibet Plateau
Author(s) -
Staisch Lydia M.,
Niemi Nathan A.,
Hong Chang,
Clark Marin K.,
Rowley David B.,
Currie Brian
Publication year - 2014
Publication title -
tectonics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.465
H-Index - 134
eISSN - 1944-9194
pISSN - 0278-7407
DOI - 10.1002/2013tc003367
Subject(s) - geology , cretaceous , plateau (mathematics) , paleontology , tectonics , structural basin , sedimentary depositional environment , group (periodic table) , colorado plateau , geochemistry , mathematical analysis , chemistry , mathematics , organic chemistry
The Fenghuoshan Group marks the initiation of terrestrial deposition in the Hoh Xil Basin and preserves the first evidence of uplift above sea level of northern Tibet. The depositional age of the Fenghuoshan Group is debated as are the stratigraphic relationships between the Fenghuoshan Group and other terrestrial sedimentary units in the Hoh Xil Basin. We present new radiometric dates and a compilation of published biostratigraphic data which are used to reinterpret existing magnetostratigraphic data from the Fenghuoshan Group. From these data, we infer an 85–51 Ma depositional age range for the Fenghuoshan Group. U‐Pb detrital zircon age spectra from this unit are compared to age spectra from Tibetan terranes and Mesozoic sedimentary sequences to determine a possible source terrane for Fenghuoshan Group strata. We propose that these strata were sourced from the Qiangtang Terrane and may share a common sediment source with Cretaceous sedimentary rocks in Nima Basin. Field relationships and compiled biostratigraphic data indicate that the Fenghuoshan and Tuotuohe Groups are temporally distinct units. We report late Oligocene ages for undeformed basalt flows that cap tilted Fenghuoshan Group strata. Together, our age constraints and field relationships imply exhumation of the central Qiangtang Terrane from the Late Cretaceous to earliest Eocene, followed by Eocene‐Oligocene deformation, and shortening of the northern Qiangtang and southern Songpan‐Ganzi terranes. Crustal shortening within the Hoh Xil Basin ceased by late Oligocene time as is evident from flat‐lying basaltic rocks, which cap older, deformed strata.