The Formation and Evolution of Mesozoic Age Oceanic Lithosphere: Rift Magmatism, Seafloor Spreading, and Sediment Processes
Abstract
The formation and evolution of Mesozoic-age oceanic lithosphere documents the processes leading to the modern distribution of continents and ocean basins starting with the breakup of Pangaea, and plays an important role in global geochemical cycling. My dissertation research uses geophysical data to investigate two themes pertaining to the formation and evolution of Mesozoic-age oceanic lithosphere: (i) the Jurassic/Early Cretaceous continental breakup at the Eastern North American Margin (ENAM) and ensuing seafloor-spreading of the early Atlantic Ocean, and (ii) the construction of the deep-ocean sedimentary section in the Jurassic-age northwestern Pacific. To address the first theme, we analyzed and modeled magnetic anomaly data to understand both the mode of magmatism that facilitated continental breakup at the ENAM and the early seafloor spreading history of the Atlantic Ocean. Studying continental breakup and seafloor spreading provides insight into the initial formation of Mesozoic-age oceanic lithosphere, and the role this lithosphere plays in the progression of Wilson Cycles. Key findings from this research include: (1) both first- and second-order magmatic segmentation, representing variations in the amount and distribution of magmatism, were present to drive continental breakup at the ENAM; (2) variations in breakup magmatism could have been influenced by preexisting structure acquired during previous Wilson Cycles, and likely governed the segmentation and transform fault spacing of the ensuing Mid-Atlantic Ridge; (3) five newly identified magnetic anomalies can be correlated along the ENAM that may document the initial oceanic lithosphere formation of the Atlantic Ocean; and (4) a reorientation of the early Mid-Atlantic Ridge, accommodated by asymmetric crustal accretion, can explain the difference in spreading center strike between the initial and modern Mid-Atlantic Ridge. To address the second theme, we interpreted multi-channel seismic reflection data from the northwestern Pacific to investigate the construction of the sedimentary section during the evolution of Mesozoic-age oceanic lithosphere, and the role of this sediment in global geochemical cycling. Results from this research suggest that a period of seafloor erosion impacted the sedimentary section, which would reduce the amount of chemical sequestration occurring in deep-ocean sediment during global geochemical cycles.
Citation
Greene, John Anthony (2020). The Formation and Evolution of Mesozoic Age Oceanic Lithosphere: Rift Magmatism, Seafloor Spreading, and Sediment Processes. Doctoral dissertation, Texas A&M University. Available electronically from https : / /hdl .handle .net /1969 .1 /192291.