Beachrocks and sea level changes since Middle Holocene: Comparison between the insular group of Mykonos–Delos–Rhenia (Cyclades, Greece) and the southern coast of Turkey (original) (raw)
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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.
The coastal belt of HatayeSamanda g in the East Mediterranean is marked by the intersection of the AfricaneArabian and Eurasian (Anatolian platelet) plates, where several Quaternary shorelines related to relative sea-level changes can be seen above the current sea level. In this study, the most common and best preserved high sea-level markers of the Marine Isotope Stage (MIS) 5 and MIS 3 shorelines were dated for the first time using the mollusc-based electron spin resonance (ESR) method. As a result of this research, the age of the late MIS 5 and MIS 3 sea-level highstands in the Eastern Mediterranean, the elevation of the corresponding shoreline at Samanda g coast, and the vertical component of the late Quaternary tectonic movements, which has an impact on shoreline, were determined. The shorelines at 48e43 m elevations between Çevlik and Samanda g, at 58.6 m in Tekebaşı and at 21 m at Kelda g have been dated to approximately 72 ka and, therefore, are correlated with MIS 5a. The shoreline at 40e39 m elevations between Çevlik and Samanda g has been dated to approximately 53 ka and, therefore, is correlated with MIS 3. According to the position of the MIS 5a shorelines, the uplift rate over the last 72 ka was 0.88 mm/y between Çevlik and Samanda g, 1.08 mm/y in Tekebaşı, and 0.56 mm/y in Kelda g, yielding a 0.84 mm/y average. This rather fast uplift appears to be related to the vertical component of the strike-slip active faults in the Samanda geAntakya Fault Zone.
Quaternary International, 2011
This paper provides new relative sea level data inferred from coastal archaeological sites located along the Turkish coasts of the Gulf of Fethye (8 sites), and Israel, between Akziv and Caesarea (5 sites). The structures selected are those that, for effective functioning, can be accurately related to sea level at the time of their construction. Thus their positions with respect to present sea level provide a measure of the relative sea level change since their time of construction. Useful information was obtained from the investigated sites spanning an age range ofe2.3ee 1.6 ka BP. The inferred changes in relative sea level for the two areas are distinctly different, from a rise of 2.41 to 4.50 m in Turkey and from 0 to 0.18 m in Israel. Sea level change is the combination of several processes, including vertical tectonics, glacioehydro-isostatic signals associated with the last glacial cycle, and changes in ocean volume. For the Israel section, the present elevations of the MIS-5.5 Tyrrhenian terraces occur at a few meters above present sea level and vertical tectonic displacements are small. Data from GPS and tide gauge measurements also indicate that any recent vertical movements are small. The MIS-5.5 shorelines are absent from the investigated section of the Turkish coast, consistent with crustal subsidence associated with the Hellenic Arc. The isostatic signals for the Israel section of the coast are also small (ranging from À0.11 mm/yr to 0.14 mm/yr, depending on site and earth model) and the observed (eustatic) average sea level change, corrected for this contribution, is a rise of 13.5 AE 2.6 cm during the past e2 ka. This is attributed to the time-integrated contribution to sea level from a combination of thermal expansion and other increases in ocean volume. The observed sea levels from the Turkish sites, in contrast, indicate a much greater rise of up to 2.2 mm/yr since 2.3 ka BP occurring in a wide area between Knidos and Kekova. The isostatic signal here is also one of a rising sea level (of up toe1 mm/yr and site and earthmodel dependent) and the corrected tectonic rate of land subsidence ise1.48 mm/yr. This is the primary cause of dramatic relative sea level rise for this part of the coast.
On the Origin and Age of the Arıburnu Beachrock, Gelibolu Peninsula, Turkey
Turkish Journal of Earth Sciences, 2008
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 amounts of major (Si, Ca, Mg, K, Fe, Al and Na) and trace elements within the beachrock cement with Si (36.2%) and Ca (32.68%) dominating the overall composition. Beachrocks composed of highly-fractured and friable beds reach a total thickness of 80 cm extending from +60 cm at the uppermost level down to-1 m at their most seaward extent and grade from conglomerate to lithic arkose in vertical section. The total amount of CaCO 3 ranges between 59.08% and 36% and the cement consists of high-Mg calcite based on EDS analysis. From SEM examination, four main morphologies were identified in cement material: (1) micritic coatings, (2) cryptocrystalline pore-filling cement, (3) meniscus cement and (4) microbial cement and suggest the presence of marine phreatic conditions with the exception of meniscus bridges, which imply that cementation may have been dominated by carbonate-rich meteoric waters at any successive stage of cementation. Five buried beachrock samples under unconsolidated beach sand were sampled for Optically Stimulated Luminescence (OSL) dating and show that the minimum and maximum ages of beachrock are 1.42±0.20 ka and 2.28±0.28 ka BP, respectively.
Tracking shoreline evolution in central Cyclades (Greece) using beachrocks
2017, Karkani A., Evelpidou N., Vacchi M., Morhange C., Tsukamoto S., Frechen M., Maroukian H., Tracking shoreline evolution in central Cyclades (Greece) using beachrocks, Marine Geology, 388, pp. 25-37. Beachrocks represent a significant paleo-environmental proxy because they can record both the vertical and the horizontal evolution of the shoreline. They have often been used to assess Holocene shoreline evolution and crustally induced Relative Sea-Level (RSL) changes in the Mediterranean Sea. In this paper, we used submerged beachrocks from Paros and Naxos Islands (Aegean Sea, Greece) to reconstruct the shoreline modification and provide new insights on the RSL evolution in central Cyclades. Paros and Naxos Islands are of great importance in terms of archaeological evidence of coastal occupation. However, the evolution of their coastlines was seldom explored. In this study, we coupled detailed underwater surveys, analysis of aerial photogrammetry, microstratigraphic analysis and luminescence dating to study beachrock outcrops found down to about 6 m below the present sea-level. We, then, spatially and chronologically constrained some major palaeogeographical changes of a number of coastal sectors of the two islands. Furthermore, the multiple analyses of beachrocks, sediment coring and archaeological data suggested that RSL rose by at least 3.8 m in the last 4.0 ka and that RSL variation in the last 2.0 ka did not exceed 2 m with respect to the present mean sea level.
Comment on "MIS 5a and MIS 3 relatively high sea-level stands on the Hatay-Samandağı coast, Eastern Mediterranean, Turkey". U. Doğan, A. Koçyiğit, B. Varol, İ. Özer, A. Molodkov, E. Zöhra. Quaternary International (2012), 2012
TURKISH JOURNAL OF EARTH SCIENCES, 2021
The timing of the deposition of the well-preserved Quaternary marine terraces in the coastal region of northeastern Turkey are crucial in understanding the Quaternary tectonics of the Pontides. The chronology of raised marine terraces between Trabzon and Rize has remained unrevealed because of chronologic limitations. This study aims to establish chronology for the terrace deposits by applying optically stimulated luminescence (OSL) dating methods using single aliquot regenerative dose (SAR) techniques on quartz grains extracted from marine terraces. Eleven samples were collected from the lowest three Quaternary marine terraces. The OSL ages clusters into three groups: 52.4 ± 4.6 to 60.0 ± 4.7 ka (terrace level T1); 16.8 ± 0.8 to 33.9 ± 2.8 ka (T2); and 11.7 ± 0.9 ka (T3). This chronology is consistent with the classical terrace stratigraphy; i.e. younger terraces are located at lower elevations and vice versa for the older terraces. We correlate the established terrace chronology with MIS 3c, MIS 3a, and MIS 1. We calculated apparent uplift rates are 0.98 ± 0.12 mm/year, 1.39 ± 0.26 mm/year, and 1.50 ± 0.78 mm/year from marine terrace levels 1, 2, and 3, respectively. Based on the existing eustatic sea-level data/curve, we estimated tectonic uplift rates up to 5 mm per year. Our results indicate that the coastal region of the Eastern Pontides experienced three accumulation periods, with sea-level highstands overprinting the uplifting coastline, and the coastal region of Eastern Pontides has been tectonically active from Late Pleistocene to Early Holocene. This study reveals that marine terraces in the coastal region of northeastern Anatolia might have displaced by the South Black Sea Fault which ultimately points to a regional subsidence with the higher uplift rate, and it points to a differential uplift along the Eastern Pontides.
E. GALILI, M. S¸EVKETOG˘ LU, A. SALAMON, D. ZVIELY, H. K. MIENIS, B. ROSEN & S. MOSHKOVITZ Published in: http://sp.lyellcollection.org/cgi/reprint/SP411.10v1.pdf?ijkey=GIICaMOjyMtjaaQ&keytype=finite Abstract: Late Pleistocene beach deposits in 22 selected sites around Cyprus demonstrate the vertical changes in the Earth’s crust in that island over the last 125 ka. The beach/shallow-marine deposits were observed on the abraded coastal cliffs at 3–22 m above the present sea-level. They overlie Pliocene marls, and some of them contain the Senegalese marine astropods Persististrombus latus, Bursa granularis and Conus ermineus that no longer live in the Mediterranean. These are index fossils for the Marine Isotope Stage (MIS) 5e in the Mediterranean and, as such, suggest an uplift of up to 15.5 m over about the last 125 ka: that is a maximal rate of 0.12 mm a21. These findings are in accordance with Holocene beachrocks, abrasion platforms, wave notches and Roman/ Byzantine fish tanks that retained their elevations, and thus enable the reconstruction of the coast encountered by the early colonizers. While the maximal uplift since the early Holocene has been minor and did not exceed 1.2–1.5 m, the sea-level changes have reached 40–50 m. The transition between the impermeable Pliocene marls and the porous Late leistocene deposits above them is the origin of freshwater springs and associated vegetation. The early colonizers seemed to recognize the potential of that essential permanent source of water and excavated wells, the earliest wells known so far. The locations of the Early Neolithic settlements Mylouthkia and Akanthou) adjacent to visible water springs along the coastal cliffs may not be incidental. Not surprisingly, recent wells dug in the coastal Pleistocene deposits rely on the very same hydrological setting.