The Owen Ridge uplift in the Arabian Sea: Implications for the sedimentary record of Indian monsoon in Late Miocene

Abstract

International audienceThe pelagic cover of the Owen Ridge in the Arabian Sea recorded the evolution of the Indian monsoon since the Middle Miocene. The uplift of the Owen Ridge resulted from tectonic processes along the previously unidentified Miocene India-Arabia plate boundary. Based on seismic reflection data tied with deep-sea drilling to track the Miocene India-Arabia plate boundary, we propose a new timing for the uplift of the Owen Ridge and highlight its impact on the record of climate changes in pelagic sediments. The new dataset reveals a fracture zone east of the Owen Ridge corresponding to the fossil plate boundary, and documents that the main uplift of the Owen Ridge occurred close to ∼8.5 Ma, and is coeval with a major uplift of the east Oman margin. Late Miocene deformation at the India-Arabia plate boundary is also coeval with the onset of intra-plate deformation in the Central Indian Ocean, suggesting a kinematic change of India and surrounding plates in the Late Miocene. The uplift of the Owen Ridge above the lysocline at ∼8.5 Ma accounts for a better preservation of Globigerina bulloides in the pelagic cover, previously misinterpreted as the result of a monsoon intensification event

Tectonics of the Dalrymple Trough and uplift of the Murray Ridge (NW Indian Ocean)

“…Therefore, the angular unconformity marking the main uplift of the Murray Ridge recognized by Gaedicke et al (2002a) (picked in blue on Fig. 3) is different from the U-unconformity recognized everywhere in the Owen Basin and the Oman abyssal plain (Rodriguez et al, 2014).…”

“…The exact location of the fossil India-Arabia plate boundary remains debated (Edwards et al, 2000;Mountain and Prell, 1990;Royer et al, 2002;Whitmarsh, 1979). The recent identification of a fracture zone buried under the Indus deposits 5-10 km east of the OFZ (Rodriguez et al, 2014), together with magnetic anomalies reconstructions , suggests that the plate boundary remained close to the Owen Ridge since at least the beginning of oceanic accretion in the Gulf of Aden in the Early Miocene (Fournier et al, 2010). Buried, abrupt and sharp vertical fault offsets recognized on the eastern side of the Southern Murray Ridge (Edwards , 2000) could correspond to the northward prolongation of the fracture zone that used to form the Miocene India-Arabia plate boundary (Fig.…”

“…The U-unconformity is recognized over the entire Owen Basin and the Oman abyssal plain (Rodriguez et al, 2014;Shipboard Scientific Party, 1974;Whitmarsh, 1979;Whitmarsh et al, 1974). According to ODP (Ocean Drilling Project) and DSDP (Deep Sea Drilling Project) Sites, the U-unconformity marks a highly diachronous transition between Upper Oligocene-Lower Miocene pelagic chalk and Upper Oligocene-Lower Miocene turbidites coming from the Indus fan.…”

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“…Clift and Plumb (2008), Molnar et al (2010), and the report from the Detailed Planning Group "Asian Monsoon and Cenozoic Tectonic History" (www.iodp.org/doc_download/2336-mmdpgreport) provide comprehensive overviews of these issues. More recently, Rodriguez et al (2014) suggested that the ~8 Ma intensification inferred on the basis of increased Globigerina bulloides concentrations is an artifact of increased preservation related to uplift of the Owen Ridge at this time, resulting in enhanced preservation.…”

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“…Clift and Plumb (2008), Molnar et al (2010), and the report from the Detailed Planning Group "Asian Monsoon and Cenozoic Tectonic History" (www.iodp.org/doc_download/2336-mmdpgreport) provide comprehensive overviews of these issues. More recently, Rodriguez et al (2014) suggested that the ~8 Ma intensification inferred on the basis of increased Globigerina bulloides concentrations is an artifact of increased preservation related to uplift of the Owen Ridge at this time, resulting in enhanced preservation.…”