Cementation characteristics and age of beachrocks in a fresh-water environment, Lake İznik, NW Turkey (original) (raw)
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First note on marine-like cementation of late holocene beachrock, Iznik Lake (Turkey)
Geochronometria, 2012
Micro-fabric characteristics and optically stimulated luminescence (OSL) dating results are presented to discuss the controlling agents and timing of beachrock cementation on the freshwater Iznik Lake shoreline. The beachrocks are made up of grain-supported polygenic conglomerate containing 20.42% carbonate with encrusted grains, basically as micrite coatings, isopachous aragonite rims, cryptocrystalline void fills and meniscus bridges. The optical ages of twelve samples yielded ages that range from 4.226±0.569 ka on the lowermost beds to 0.706±0.081 on the uppermost. This is the first report of precipitation of marine-like cements in Iznik Lake. The abundant aragonitedominated cement is likely indicative of precipitation-prone dry evaporative conditions from the climatic optimum to the last millennia.
Sedimentary Geology, 2013
We present new data on the diagenetic characteristics, subsurface nature and radiocarbon ages of beachrock from the Thracian Black Sea coast of Turkey, indicative of sea-level changes and climatic conditions favoring lithification of beach sands between 5.4 ka and 3.5 ka cal BP. Micrite coatings and succeeding meniscus cements typify diagenetic history and suggest a two-stage cementation over this timeframe. The early cements are typical of upper intertidal zone when the sea-level was likely similar to that of today. The ensuing intergranular bridges refer to an approximate 2 m decline in sea-level, favoring downward percolation of meteoric waters related to subaerial exposure, marked by a reduction in Mg concentration and dissolution pits on early cement coatings. Formation of beachrock during this bimillennial period could be associated with relatively drier conditions promoting the precipitation of connective cements.
Journal of Coastal Research, 2013
Avcıoglu, M.; Erginal, A.E.; Kiyak, N.G.; Kapan-Yes ilyurt, S., and Yigitbas . 0000. A preliminary note on depositional characteristics and optical luminescence age of a marine terrace, Strait ofÇanakkale, Turkey, Journal of Coastal Research, 00(0), 000-000. Coconut Creek (Florida), ISSN 0749-0208.
Global and Planetary Change, 2009
The small insular group of Mykonos–Delos–Rhenia in Cyclades, Greece, and the southern coast of Turkey from Andriake to Arsuz show three bands of beachrocks, emerged up to + 0.35 m and submerged sometimes down to − 4.3 m. Because beachrocks are formed within the intertidal zone by carbonate cementation of the beach deposits during stages of shoreline stabilisation (both eustatic and tectonic), they correspond to different generations indicating different sea level stands.11 sites on the southern coast of Turkey and 7 bays on the insular group of Mykonos–Delos–Rhenia were studied. 52 beachrock samples were analysed by polarizing microscope, cathodoluminescence and SEM. This study indicated that carbonate elements that constitute most of the samples were at least partly incorporated within the intertidal zone. The adequate method for radiocarbon dating (total sample or cement) was decided according to these observations. Because diagenetic cements seemed difficult to extract manually and the sources of carbonate pollution are limited in Mykonos–Delos–Rhenia, we performed 14C AMS dating on total samples. On the southern coast of Turkey, due to the abundance of micrite in between the limestone pebbles that often constitute the beachrocks, available cements had to be manually extracted for 14C AMS dating.The dates obtained from Mykonos–Delos–Rhenia beachrocks indicate 3 separate sea level stands: the first one at about − 3.6 m (± 0.5 m) around 2000 BC, the second one at about − 2.5 m (± 0.5 m) around 400 BC and finally the third sea level at about − 1 m (± 0.5 m) around 1000 AD. On the southern coast of Turkey, several relative sea level positions in 4 areas (I to IV) are recognised. From Finike Bay to the west (area I), a post-Roman relative sea level rise is observed after a period of coastline stabilisation. The area from the east of Finike Peninsula to Çimtur (area II) witnessed relative sea level rise since mid-Holocene interrupted by 3 phases of stability corresponding to beachrock bands. Two levels have been dated. The first one is between 0 m and − 0.8 m and dates from 5th to 7th century AD. The second one is between − 1.5 m and − 2.2 m and dates around 7th to 6th century BC. From Incekum to Karataş–Osmaniye Fault Zone to the south of Adana (area III), the shoreline was raised around + 0.5 m after 19 BC–200 AD and later becomes stable at least since the 12th century AD as can be interpreted from archaeological remains. To the east, beachrocks in Gözcüler (area IV) indicate a relative sea level rise interrupted by a phase of coastline stabilisation between 0 m and − 0.5 m from the 4th to the 7th century AD. Our southern Turkish coastline observations reveal a very dynamic tectonic regime – mainly subsidence to the west and uplift to the east – since at least mid-Holocene.The comparison of the results obtained from Greece and Turkey indicates a tectonic subsidence during the last 6000 years in the centre of Cyclades.
On the Origin and Age of the Arıburnu Beachrock, Gelibolu Peninsula, Turkey
Turkish Journal of Earth …, 2008
Abstract: The beachrock formation on the Arıburnu coast situated in the Gelibolu Peninsula has been studied by field observation, thin-section interpretation, physicochemical analyses including ICP-AES and SEM/EDS, and OSL dating. These analyses reveal the presence of different ...
14th International Conference of the Geological Society of Greece, 2016
Beachrocks represents a coastal deposition in the intertidal area, and studying their properties may lead to create a model which identifies the conditions of their formation (paleo-environment). This paper focuses most intently on the cement material which is able to recover the paleo-environment conditions during diagenesis of such coastal sediment. We used optical microscopy, secondary electron microscopy and Raman Spectroscopy to characterize the cement texture, mineralogy and chemistry in the beachrocks. The existence of pure calcite primarily controlled by the meteorite water, while Mg-calcite appears between the lower meteoric and the upper marine phreatic zone. Finally, the presence of aragonite associated with the marine phreatic to lower marine vadose environment.
Beachrock as a Paleoshoreline Indicator: Example from Wadi Al-Hamd, South Al-Wajh, Saudi Arabia
Journal of Marine Science and Engineering
The present study concerns the Holocene inland beachrocks that are exposed in the Red Sea coastal plain at the mouth of Wadi Al-Hamd, South Al-Wajh City, Saudi Arabia, and their utility as an indicator for Holocene climate and sea level changes. In addition, the framework composition, and carbon and oxygen isotopic data, are employed to interpret the origin of their cement. The beachrock consists mainly of gravel and coarse-grained terrigenous sediments dominated by lithic fragments of volcanic rocks, cherts and rare limestones along with quartz, feldspars and traces of amphiboles and heavy minerals. In addition, rare skeletal remains dominated by coralline algae, benthic foraminifera and mollusca remains are recognized. The allochems are cemented by high Mg-calcite (HMC) formed mainly in the intertidal zone under active marine phreatic conditions. The cement takes the form of isopachous to anisopachous rinds of bladed crystals, micritic rim non-selectively surrounding siliciclastic...
Mediterranean Geoscience Reviews, 2019
On the seaward northwest slopes of Mount Keldağ, Hatay, the combination of an unconformably overlapping sequence of cemented gravels on a wave-cut platform, and a raised notch and irregular pits left by grazing molluscs on the walls of this notch, carved in an NE-trending high-angle fault plane, retain the record of raised braided stream gravels transformed into beachrock. From the OSL ages, this study reveals that deposition of this sequence occurred between 232.30 ± 31.62 and 214.01 ± 27.42 ka during the penultimate interglacial. The four distinct facies identified are massive matrix-supported conglomerate, massive to crudely stratified gravel, cross-stratified gravel, and clast-supported open-work gravel. Extending to the paleo-coastline during the MIS7 highstand, this sequence was cemented by carbonate and iron-oxide cements and records an uplift of around 0.1 mm/year up to the present.
Microfacies Analysisoflower and Middle Eocene Carbonate Rocks in the East of Lake Van (Turkey)
Zenodo (CERN European Organization for Nuclear Research), 2022
A detailed study on the microfacies and depositional environments of Lower and Middle Eocene sedimentary rocks outcrop in Van Province (Turkey) were conducted. The investigation was based on sixty five samples collected from three stratigraphic sections and included Toprakkale and Yücelendere formations. These rock units are composed of carbonate rocks. The petrographic study of thin sections have been carried out to investigate their microfacies and depositional environments. The rocks are generally biomicrite. According to the characteristics of carbonate rock samples five microfacies were determined. These are; 1) Wackestone with Globigerina and Acarinina microfacies, 2) Wackestone-Packstone with Globigerina and Acarinina microfacies, 3) Packstone-Grainstone with Globigerina and Acarinina microfacies. 4) Grainstone with Milioliidae and Red Algae microfacies. 5) Packstone with Nummulites and Red Algae microfacies. These microfacies indicate that Lower-Middle Eocene rocks were formed in depositional environments ranging from shelf lagoon to deep marine. These differences in depositional environments have been interpreted as the result of changes in water level in relation to transgression and regression events.
Clastic sedimentary features of beachrocks and unconsolidated deposits of parent beaches were investigated along the northern Aegean coastline (Greece) to assess their suitability in palaeo-environmental reconstruction. Twelve paired datasets were collected in the Thermaikos, Toroneos, Siggitikos and Ierissos gulfs of the Chalkidiki Peninsula, the adjoining Kavala Gulf and Thassos Island, comprising beachrock cores and companion beach subsurface sediments. Particle size analyses based on univariate and bivariate statistics suggest that, during the time period of beachrock formation, depositional conditions differed distinctly from those of the modern parent beaches. The results imply difference of maturity level of beach evolution from the time of cementation (coarser materials-early stage of beach formation) to modern situation (finer materials-reworked and 'mature' beach sediments). Furthermore, the findings indicate increasing coastal protection due to beachrock exposure in the modern swash zone. In conclusion, it is suggested that textural analysis of beachrocks in comparison with unconsolidated sediments of the parent beach might provide information regarding differences of coastal depositional regimes and future research could focus on specific-layer analysis and comparison.