Collision Zone Geodynamics

Author : Megan Anne Mueller
Publisher :
ISBN 13 :
Total Pages : 178 pages
Book Rating : 4.:/5 (132 download)

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Download or read book From Subduction to Collision written by Megan Anne Mueller and published by . This book was released on 2021 with total page 178 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Tethyan orogenic belt extends from the western Mediterranean to southeast Asia and the exposed rocks and landscapes present today are records of multiple orogenic events. The most recent, the Alpine-Himalayan orogeny, evolved during the Mesozoic-Cenozoic closure of the Neotethys Ocean during the convergence of Gondwana with Laurasia. Over the last few decades, significant advances in geochemical and geochronological methods and their widespread application have created a high-resolution temporal framework that reveals that various proxy records of intercontinental collisions across the Alpine-Himalayan belt differ by tens of millions of years. Consequently, new questions have arisen, including how to unite these seemingly disparate records of subduction and collision into a temporally and spatially credible reconstruction.The work set forth in this dissertation situates the Anatolian segment of the Alpine-Himalayan orogenic belt in the broader discussion on the timescales and drivers of intercontinental collisions and their effect on biogeography. The various suture zones in Anatolia that delineate former branches of the Neotethys Ocean have complex and unresolved geodynamic reconstructions, including single and double subduction systems, pre-collisional subduction of lower plate terranes, forearc and backarc extension, ophiolite obduction, and protracted collisional deformation. Resolving these competing geodynamic scenarios is essential for paleogeographic reconstructions for refining the mechanistic links between subduction, accretion, and collision processes. Furthermore, the role of collisions in the early Cenozoic Anatolian archipelago in facilitating mammalian faunal exchange, including anthropoid primates, between Europe, Asia and Africa relies on accurate paleogeographic and topographic reconstructions. Near-continuous deposition in western Anatolian sedimentary basins preserves an unbroken record of subduction through collision that is unparalleled across the Tethyan realm. This dissertation utilizes this sedimentary record by providing new stratigraphic, sedimentologic, petro- and geochronologic, and sedimentary provenance constraints on the chronology of collision along the İzmir-Ankara-Erzincansuture zone and the Intra-Pontide suture zone in western Anatolia. The sedimentary basin reconstructions presented in this dissertation, synthesized with existing datasets, provide a model for multi-stage continental collision that is applicable across the Tethyan realm. Detrital zircon U-Pb geochronology and sandstone petrography data from the forearc-foreland Central Sakarya Basin in western Anatolia indicate that collision along the İzmir-Ankara-Erzincan suture zone began at 76 Ma, recorded as a major shift in provenance and the onset of exhumation, sediment recycling, and suture zone uplift. Furthermore, new stratigraphy, sedimentology and sedimentary provenance studies from the foreland Sarıcakaya Basin in western Anatolia reveal that significant upper plate deformation was delayed by 20 Myr. By 54 Ma, the Central Sakarya Basin was partitioned by a basement-involved thrust fault, and flexural loading from the thrust created the Sarıcakaya Basin. This 20 Myr protracted collision along the İzmir-Ankara-Erzincan suture zone can be explained by three Tethyan models for multi-stage collision: slab breakoff, relict basin closure, or subduction of thinned passive margin lithosphere. The validity of relict basin closure is evaluated using detrital zircon U-Pb geochronology, detrital rutile U-Pb and trace element geochemistry, and sandstone petrography from sedimentary units across the Intra-Pontide suture. A major shift in provenance in the Paleocene-early Eocene caused by accretionary prism exhumation demonstrates that collisional stress from incipient İzmir-Ankara-Erzincan suturing could have been taken up by the Intra-Pontide suture. Furthermore, the sedimentary evolution of both suture zones reveals that the uplift and exhumation of the accretionary prism is an important signal of collisional geodynamics. Even though continental collisions assembled a larger landmass that favored trans-Tethyan mammalian dispersals, for 30 Myr after initial collision, collisional deformation did not form significant topography; marine barriers and endemism persisted until the late Eocene. Accretionary orogenies, like those in Anatolia, likely have an important control on biogeography. The findings presented in this dissertation bear on fundamental questions regarding the interconnectedness of Earth systems, including the effects of plate tectonics, the causes of topographic change, and the geologic drivers of biodiversity.