Petrography and geochemistry of the late Eocene–early Oligocene submarine fans and shelf deposits on Lemnos Island, NE Greece. Implications for provenance and tectonic setting

Abstract

Provenance and tectonic history of the late Eocene-early Oligocene submarine fans and shelf deposits on Lemnos Island, NE Greece, were studied using sandstone framework composition, sedimentological data and sandstone and mudstone geochemistry. The resulting tectonicsedimentological model is based on the late Eocene-early Oligocene Lemnos Island being in a forearc basin with the outer arc ridge as a major sediment source. Modal petrographic analysis of the studied sandstones shows that the source area comprises sedimentary, metamorphic and plutonic igneous rocks deposited in the studied area in a recycled orogenic environment. Moreover, within the above sediments, the minor occurrence of volcanic fragments suggests little or no influence of a volcanic source. Provenance results, based on major, trace and rare earth element (REE) data, suggest an active continental margin/continental island arc signature. All the samples are LREE, enriched relative to HREE, with a flat HREE pattern and positive Eu anomalies, suggesting that the processes of intracrustal differentiation (involving plagioclase fractionation) were not of great importance. Results derived from the multi-element diagrams also suggest an active margin character, and a mafic/ultramafic source rock composition, while the positive anomaly of Zr that can be attributed to a passive continental margin source, is most likely associated with reworking and sorting during sediment transfer. Palaeocurrents, with a NE-NNE direction, indicate a northeast flow, towards the location of the late Eocene-early Oligocene magmatic belt in the north-east Aegean region. Conglomerates are composed of chert, gneiss and igneous fragments, such as basalts and gabbros, suggesting this outer arc ridge as a likely source area.

The Rhodope Zone as a primary sediment source of the southern Thrace basin (NE Greece and NW Turkey): evidence from detrital heavy minerals and implications for central-eastern Mediterranean palaeogeography

“…From the late Eocene (Priabonian), most of the successions record deep-marine sedimentation, including carbonate olistoliths and significant volcanoclastic debris. A general coarsening upward trend is documented for the entire southern Thrace basin through time (Maravelis and Zelilidis 2010;d'Atri et al 2012;Cavazza et al 2014). Available palaeocurrent measurements (Limnos: Maravelis and Zelilidis 2010; southern Thrace: d' Atri et al 2012) indicate that only the most proximal facies show northward palaeocurrents whereas most measured palaeocurrent indicators show an eastward palaeoflow, most likely the result of gravity flow deflection.…”

Comment on Maravelis et al. “Accretionary prism–forearc interactions as reflected in the sedimentary fill of southern Thrace Basin (Lemnos Island, NE Greece)”

“…Here we like to point out that Caracciolo et al (2013) highlighted that Maravelis and Zelilidis (2010) have never recognised the occurrence of (1) glaucophane schists, nor of (2) (2014). Another point of discussion is related to both the analytical techniques and the "provenance" diagrams used by Maravelis et al (2015).…”

Reply to the Discussion by Maravelis and Zelilidis on “Unravelling provenance from Eocene–Oligocene sandstones of the Thrace Basin, North‐east Greece” by Caracciolo et al. (2011), Sedimentology, 58, 1988–2011.

“…In the Petrography/Geochemistry section of their Discussion, Maravelis & Zelilidis () affirm that the primary sediment supplier for Limnos was an ophiolitic source. However, the petrographic results of Maravelis & Zelilidis (; Figs 6, 7, 8, 9, 10B and 11) show typical arkosic composition, consisting of monocrystalline quartz and feldspar grains associated with granitoid rock fragments. Basalt and cherts were only detected, but not attributed to ophiolite sources.…”

“…The Discussion by Maravelis & Zelilidis () and the work by Maravelis & Zelilidis () do not take into account the presence of significant amounts of neovolcanic material (Marsaglia et al ., ; Critelli & Ingersoll, ; Critelli et al ., ). Conversely, they comment on the lack, or at least the scarcity, of volcanic particles.…”