Structural and geomorphic evolution of the Gonghe basin complex, northeastern Tibet: Implications for the timing of plateau growth

Open Access
Author:
Craddock, William Howard
Graduate Program:
Geosciences
Degree:
Doctor of Philosophy
Document Type:
Dissertation
Date of Defense:
January 18, 2011
Committee Members:
  • Eric Kirby, Dissertation Advisor
  • Eric Kirby, Committee Chair
  • Rudy L Slingerland, Committee Member
  • Donald Myron Fisher, Committee Member
  • Derek Elsworth, Committee Member
Keywords:
  • tectonics
  • geology
  • geomorphology
  • geochronology
  • Tibetan plateau
  • Gonghe basin complex
  • Jungong basin
  • Yellow River
  • geodynamics
  • stratigraphy
  • structural geology
Abstract:
Reconstructing the kinematic history of the outward expansion of the Tibetan plateau is central to ongoing debates over the geodynamics of continental plateau growth and the manner in which the growth of high topography shapes the earth’s climate. For the broad northeastern margin of the plateau, disagreement exists over the timing, magnitude, rate, and style of contractional deformation in the upper crust. I present four field based studies from the Gonghe basin complex in the regions interior which bear on these issues. First, I document regionally extensive contractional deformation across a broad swath of interior northeastern Tibet (the Anyemaqen Shan and west Qinling Shan) during the Cretaceous, thereby providing evidence for pre-Cenozoic crustal thickening of the region. Second, I show that although northeastern Tibet may have experienced contractional tectonism during the early Tertiary, this episode appears to be confined to regions near the plateau edge (e.g. the west Qinling fault and the western Qaidam basin) and is not apparent in the intervening region. Third, I add new evidence from interior northeastern Tibet (the Gonghe basin region) to a growing body of work that points to a rapid change in structural style and depositional patterns across the entire plateau margin during the late Miocene, from slow sedimentation in broad basins, to rapid sedimentation in narrow, structurally bounded basins. Fourth, I show that upper crustal shortening since the late Miocene has been small, on the order of 4%, along a 350 km profile in interior northeastern Tibet. Fifth, I show that fault networks in the region sole into decollements at deep levels (10s of km) in the crust, analogous to other intracontinental mountain ranges such as the Laramide ranges in the western United States, or the Sierra Pampeanas of Argentina. Finally, I reconstruct the time-transgressive incision of the Yellow River during the Quaternary. Canyon incision lagged the onset of mountain building in the Miocene by nearly ~10 Ma, and spatiotemporal patterns of incision suggest that it resulted drainage basin integration around northeastern Tibet.