Sedimentary and environmental characteristics of the Gilan-Mazenderan plain, northern Iran: Influence of long- and short-term Caspian water level fluctuations on geomorphology

The south-southwestern Caspian coastal lowland in Iran, or the Gilan-Mazenderan plain, is a relatively narrow but long, composite depositional area of late Quaternary age. The Sefid Rud delta, the Anzali Lake (connected to the Caspian Sea by a meandering outlet 3.5 km long) and storm-dominated beaches are its prominent sedimentary features. They are controlled by the present water level of the Caspian Sea at -26.36 m in 2000. The Late Pleistocene-Holocene deposits of the lowland, which are covered commonly by a modern loess-origin soil, mainly consist of alternations of marine and non-marine sediments. The marine units form coastal terraces at 19-20 m (I), 2-0 m (II) and –6/-8 m (III) corresponing to the Late Khvalinian and Neocaspian transgressions. The deposits of the youngest terrace (terrace III) that represents a prograding beach-ridge complex are a consequence of several medium-term, cyclic water level oscillations in Late Holocene. Just after the initiation of the beach-ridge complex, Lake Anzali formed by damming of rivers and then by progradation of the complex in time forced to form the outlet of the lake. The nearest medium-term cycle lasted c. 65 years between 1930-1995 and the records showed that it included a lot of short-term (c. 4-5 yrs) and very short-term (week to months) water level oscillations. During the last erratic rise of sea level (1977-1996), the area of Lake Anzali doubled; the delta and the coastal sands including modern beaches were eroded on c. 30-100 m. Overall, a step-like morphology, repetition of marine and non-marine facies and also water level records of the last 75 years indicate that the ancient and recent deposition on the coastal lowland has been controlled by long- medium- and short-term fluctuations of the Caspian Sea level

Late Holocene erosion in NW Anatolia from sediments of Lake Manyas, Lake Ulubat and the southern shelf of the Marmara Sea, Turkey

This paper deals with modern and ancient sedimentation in fresh water lakes and the marine shelf of the southern Marmara region, NW Anatolia, Turkey. Most of the information has been obtained from monitoring of suspended load discharged into two lakes (Manyas and Ulubat) in the last 45 years and from 8-11 m thick lacustrine sediments, in addition to radiocarbon-dated shelf sediments. This allows a holistic approach to the drainage basin denudation over time. The results show that the sedimentation rates in the lakes were low 0. 22 cm.yr-1, from 4000-2000 yr BP and then they increased (0.29 cm.yr-1) up to sub-recent times and reached 0.44 cm.yr-1 in the last century. It is suggested that deforestation created high rates of sedimentation in the basins and/or strong denudation of the region during the Late Holocene. This study also shows that for shallow freshwater lakes the calculation of sedimentation rates must include fine particles lost by the outlets and coarse-grained bed load deposited on their shores. In addition, a high rate of sedimentation has been created by short, but repetitive intense depositions. During the last century particularly during the last 45 years the rate of sedimentation or denudation has increased dramatically in NW Turkey. The two World Wars and mismanagement of the land had important local effects by increasing deforestation and resulting in the present erosive conditions

Boron content of Lake Ulubat sediment: A key to interpret the morphological history of NW Anatolia, Turkey

Freshwater Lake Ulubat (c. 1.5 m deep and c. 138 km2) receives sediment from a 10.414 km2 area in the seismically active Susurluk Drainage Basin (SDB) of NW Turkey. The B and trace element contents of the lake infill seem to be a link between the fresh landforms of the SDB and the lacustrine sediment. Deposition in Lake Ulubat has been 1.60 cm.a-1 for the last 50 a according to radionucleides; however the sedimentation rate over the last millennium was 0.37 cm.a-1 based on 14C dating. The B content of the lacustrine infill displays a slight increase at 0.50 m and a drastic increase at 4 m depth occurring c. 31 a and c. 1070 a ago respectively. Probably the topmost change corresponds to the start of open mining in the SDB and the second one to the natural trenching of borate ore-deposits. These dates also show indirectly a 1.4 cm.a-1 erosion rate during the last millennium as the borate beds were trenched up to 15 m. By extrapolation, it is possible to establish that the formation of some of the present morphological features of the southern Marmara region, especially river incision, began in the late Pleistocene, and developed especially over the last 75 ka

Wind control on the accumulation of heavy metals in sediment of Lake Ulubat, Anatolia, Turkey

Freshwater Lake Ulubat (zmean = 1.5-2.0 m and Area = ~138 km2), NW Anatolia, Turkey was filled in by fine-to-medium-grain silts during the late Holocene. Deposition in Lake Ulubat has been 1.6 cm yr-1 for the last 50 years, but the sedimentation rate over the last ~1,600 years was lower (0.37 mm yr-1). The organic matter and carbonate contents of the infill show cyclic changes that reflect environmental fluctuations. The silt-dominated lithology and the vertically uniform heavy metal distributions are probably due to wind-controlled sedimentation in the lake. Heterogeneous mud, derived from a large, mountainous drainage basin, is deposited in the lake mostly during summer, June to October, when conditions are hot and calm. Winter months are stormier and sediments are re-suspended due to the shallow water depth and the effect of waves on the lake bottom. It is likely that re-suspended sediments, particularly fine-grained particles, together with the heavy metals, are transported out of the lake via the outlet, especially during periods of high lake level. This resuspension and removal process probably caused the lake sediments to become silt-dominated and depleted in heavy metals. The role of broad shallow lakes in sequestering sediments and heavy metals can be described more accurately when wind data are considered. Such information may also be helpful for land-use planning in downstream areas

Fuzzy n-ary polygroups related to fuzzy points

AbstractRecently, fuzzy n-ary sub-polygroups were introduced and studied by Davvaz, Corsini and Leoreanu-Fotea [B. Davvaz, P. Corsini, V. Leoreanu-Fotea, Fuzzy n-ary sub-polygroups, Comput. Math. Appl. 57 (2008) 141–152]. Now, in this paper, the concept of (∈,∈∨q)-fuzzy n-ary sub-polygroups, (∈¯,∈¯∨q¯)-fuzzy n-ary sub-polygroups and fuzzy n-ary sub-polygroup with thresholds of an n-ary polygroup are introduced and some characterizations are described. Also, we give the definition of implication-based fuzzy n-ary sub-polygroups in an n-ary polygroup, in particular, the implication operators in Łukasiewicz system of continuous-valued logic are discussed

Soft hyperstructure

AbstractIn this paper, we study soft hypergroupoids. Firstly, we introduce the notion of soft hypergroupoids, and some examples are given. Also, we show that soft hypergroupoids are closely related to L-subhypergroupoid. Secondly, using the notion of soft hypergroupoid, some new properties of soft hypergroupoids are obtained. Lastly, we investigate some properties of soft subhypergroupoids

On Fuzzy Ordered Hyperideals in Ordered Semihyperrings

In this paper, we introduce the concept of fuzzy ordered hyperideals of ordered semihyperrings, which is a generalization of the concept of fuzzy hyperideals of semihyperrings to ordered semihyperring theory, and we investigate its related properties. We show that every fuzzy ordered quasi-hyperideal is a fuzzy ordered bi-hyperideal, and, in a regular ordered semihyperring, fuzzy ordered quasi-hyperideal and fuzzy ordered bi-hyperideal coincide

Abrupt environmental changes within a late Holocene lacustrine sequence south of the Marmara Sea (Lake Manyas, N-W Turkey): possible links with seismic events

A coring campaign in Lake Manyas (Kus Gölü) on the southern coast of the Sea of Marmara (Turkey) has provided insights into basin infilling processes during the upper eleven metres of the sedimentary record. Combined sedimentary features between 5 and 4 m depth have been explained by a seismite. A brittle mixed layer (uniquely rich in seeds and ostracod valves) was widely detected at 4 m downcore. This has been interpreted as being the result of a seiche either through a salt inundation linked to a tsunami in the Sea of Marmara (the large-scale scenario) or a local hydrothermal fluid discharge (the small-scale scenario). Ostracod valves, which are usually not preserved in the L. Manyas sediments are either incorporated here as tsunami debris (providing a spatially-averaged snapshot of the regional assemblage) or are locally preserved following a temporary geochemical/hydrochemical change of the water of unknown duration (but probably several decades). The brittle mixed layer overlies cracks resulting from the direct effects of the seismic shock wave on slightly compacted sediment. Palynological and particle-size analyses indicate a change from backswamp to open lacustrine conditions at around 964 cm depth. The end of the backswamp has been correlated with a decrease in the levels of the Sea of Marmara from 4,000 to 3,000-2,800 yr ago (uncal.), caused by regional tectonic movements. An age-depth model is presented based on two AMS radiocarbon dates, on the palynological detection of the end of the Beysehir Occupation Phase (130 cm above the event) and on maximal sedimentation accumulation rates obtained by radionuclide analyses. The entire study sequence covers the last 4,300 years. The paper examines the possibility of an Early Byzantine age for the seismic event. This may have been the historical event at AD 460 that destroyed Cyzicus (the ancient Erdek, 20 km north of the lake) and various villages in the interior and was felt widely in the then-known world. Other possibilities include various local and regional events in that same period: the Early Byzantine Tectonic Paroxysm and the large earthquake in AD 447 that affected the entire Sea of Marmara region