Climatic and tectonic controls on deep water sedimentary cyclicity : evidence from the Miocene to Pleistocene of Cyprus

Davies, Quintin James (2001). Climatic and tectonic controls on deep water sedimentary cyclicity : evidence from the Miocene to Pleistocene of Cyprus. PhD thesis The Open University.



Traditionally, sedimentation at active plate margins is thought to be dominantly controlled by tectonism, with any climatic cyclicity being overprinted. Since the early Miocene, Cyprus has been situated above an active subduction zone, which has strongly influenced the regional tectonics. Global climate change also occurred during the Miocene marking a transition from relative global warmth of the early-Miocene to the Neogene 'icehouse world'. Cyprus has extensive outcrops of Miocene to Pleistocene deep water sediments and provides an ideal setting to test the magnitude of climatic signals in tectonically active areas, and thus deduce the relative roles of climate and tectonics on sedimentation.

Detailed sedimentary logging and biostratigraphical dating of the Miocene-age pelagic Pakhna Formation reveals that the formation can be divided into depositional sequences,bounded by hard grounds or erosion surfaces, and contains a distinct pattern of marl-chalk couplets. These sequences correlate, within the constraints of biostratigraphy to European and New Jersey Margin sequence chronostratigraphy. Three smaller scales of cyclicity are identified by stratigraphic time series analysis, and are likely to correspond to the 100 kyr, 41ky and ~20 ky Milankovitch cycles. Stable oxygen and carbon isotope analysis on pelagicforaminifera indicate the following climatic influences; (1) chalk-marl couplets probably record climatically controlled supply of terrigenous material; (2) a strong link between 818O maxima and sequence boundaries; and (3) the globally recognised 813C Monterey ExcursionIS present. The increasing abundance of tectonically derived Troodos material partially masks the climatically controlled sedimentation in the Pakhna Formation south of the Troodos massif.

Rapid Troodos uplift during the Pliocene-Pleistocene is demonstrated by the high abundance of ophiolite derived clasts in the Khirokitia-Psematismenos submarine fan-complex. Here,graphic logging, and biostratigraphy suggests that the six cycles observed are likely to correlate to cycles identified in European sequence chronostratigraphy, though higher frequency,climatic cyclicity is obscured by the overprint of tectonic activity.

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