Research Information System
British Sedimentological Research Group's 54th annual meeting, Keele, United Kingdom, 19 - 22 December 2015, pp.120, (Full Text)
There is current international interest in the initiation of oceanic island arcs (e.g. IODP Expeditions 350-352). Such early arc units may not be preserved in the stratigraphic record. However, related volcanogenic sediments may be widely dispersed and so can provide information on early island arc genesis.
In Cyprus, the U. Cretaceous Troodos Ophiolite formed above a subduction zone at ca. 90Ma and is overlain in the west of the island by volcanogenic sediments, dated palaeontologically at ca. 80 Ma (Campanian-early Maastrichtian). In the SW Pacific (e.g. Izu-Bonin region) arc volcanism followed ca. 8-10 Ma after supra-subduction zone ophiolite genesis. Do the Cyprus sandstones record early stage oceanic arc volcanism or instead the products of continental margin arc volcanism (known to have occurred elsewhere in the region during the Late Cretaceous)?
The Kannaviou Formation is represented by medium- to coarse-grained volcaniclastic sandstones, which were mostly deposited by gravity flows, interbedded with smectite-rich clays and deep-sea radiolarian mudstones. Abundant vesicular volcanic glass is present, together with common monocrystalline quartz, plagioclase and felsic volcanic lithics. Less common components include clinopyroxene, muscovite, biotite, hornblende and pelagic bioclasts. Fourteen samples were pointcounted using the Gazzi-Dickinson method. The average framework composition (Q24F39L37) is suggestive of a dissected arc, to transitional arc source. Scanning electron microscope images indicate the presence of abundant uncrystallised volcanic glass, together with other detrital and diagenetic components. Chemical analysis of major and trace elements using X-ray fluorescence indicates a magmatic arc source. Rare Earth Element analysis by Laser Ablation Inductively Coupled Plasma Mass Spectrometry is suggestive of an oceanic island arc source and, or a continental margin arc source using different discriminant diagrams. Ion microprobe analyses of volcanic glass, plagioclase, pyroxene and hornblende are compatible with a volcanic arc provenance. The terrigenous material, however, is indicative of a continental contribution.
To further characterise the provenance, on-going research includes additional fieldwork, U-Pb dating of detrital zircons and ion microprobe analysis of trace elements in volcanic glass. Upper Cretaceous felsic extrusive rocks occur in the Kyrenia Range, N Cyprus and may have a similar origin to the Kannaviou Formation; this is being investigated.