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Title: Sedimentology and tectonic setting of Miocene reef and related sediments in Cyprus
Author: Follows, Edward Jonathan
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 1990
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A Late Cretaceous-Early Tertiary regressive sedimentary succession is developed in Cyprus. Regression continued in the Neogene, above the active Cyprus plate margin, with pelargic carbonate deposition that was followed by varied clastic and carbonate successions of the Miocene Pakhna Formation. Overlying Messinian evaporites of the Kalavasos Formation mark the peak of regression prior to the Pliocene transgression. Within the Pakhna Formation, two phases of reef growth were developed: the Aquitanian - Burdigalian aged Terra Member, and the Tortonian aged Koronia Member. The Terra Member is exposed only in west and southeasten Cyprus, mainly between pelagic carbonates. The Koronia Member is exposed around the margins of the Troodos Massif in north, south and west Cyprus and on the Akamas Peninsula in northwest Cyprus. There was little tectonic influence on the growth patterns of the reefs of the Terra Member. The reefs of the Koronia Member however, developed on up-faulted blocks. Most of the Koronia Member fore-reef facies and associated clastic input were shed into downfaulted basinal depocentres. The Koronia Member developed in a dominantly extensional re*gime, but with compressional structures developed in southern Cyprus. Limited extension in west Cyprus resulted in gradual reef migration away from a subsiding graben axis, without associated debris flows. Pulsed extension occurred on the north margin of the Troodos Massif. This resulted in mid Miocene channels and debris flows of reef talus, disruption of the evaporites of the Kalavasos Formation and then culminated in an east-west detachment of metre to kilometre-scale blocks of Pliocene sediments. Compartmentalised faulting was constrained by north-south and east-west trending faults. Stacked selenite crystals and laminated gypsum are the main lithologies in the fault localised evaporitic deposition that follows the Koronia member. Primary reef construction and the nature of the background carbonate pelagic sediments distinguishes betwen the first and second Miocene reef phases in Cyprus. The Terra Member reefs are dominantly framestones, comprising faviids and domal poritids with several types of secondary reef-dwelling corals. There is no indication of a connection with the Indo-Pacific coral faunal province. Benthonic foraminifera and fragments of crustose coralline algae are abundant in the off-reef. By contrast, the Koronia Member is a bindstone comprising virtually monospecific, alminar poritrid corals, but with coralline algae also playing a r^ole in encrustation. The Koronia member off-reef facies comprises decimetre-thick beds of bioclastic reef detritus. In north Cyprus however, beds of similar detritus (centimetres in thickness), are overlain by progressively thicker (up to several metres) debris flow sheets. The reefs of the Terra Member exhibit a limited acicular fringe cement, probably aragonitic. This is overlain by an abundant, marine, bladed, formerly high-Mg calcite cement. Later cements present in the reef facies include micritised calcite spars, perhaps indicating microboring within cements during their precipitations. Neomorphism was extensive, converting most cements to low-Mg calcite. Stable isotopic data for all the Cyprus calcites exhibit depletion in the heavier isotopes, 18O and 13C, indicative of meteoric alteration. The Koronia Member limestones show abundant indication of early lithification, with fringing fibrous aragonite and micrite cements. Isotopic analyses of the botryoidal aragonite cements indicate a marine origin. The dolomite, of Pliocene age, is thought to result from marine-freshwater mixing on the basis of stratigraphic, solution-replacive fabric and isotopic data. Dolomite characteristically replaces the Pliocene fissure fill contents in southeast Cyprus and off-reef horizons in the Terra Member and Koronia Member of west and north Cyprus respectively. The growth and burial history of Miocene reefs and related-sediments contribute to the understanding of the tectonic history and palaeogeographical evolution of Cyprus, particularly with respect to sealevel variation.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available