Multidisciplinary studies in coastal systems of the eastern Mediterranean region have proven to be excellent tools in understanding paleoenvironmental, paleoecological, and paleoclimatic changes that ...took place during the Holocene period, and how these changes interacted with urban development and growth. This paper presents sedimentological, high-resolution x-ray fluorescence (XRF scanning), micropaleontological, and x-ray diffraction (XRD) data from three shallow sediment cores that were retrieved from Aliki (ancient Siphai or Tipha) salt pond. The study area is located in a unique, highly tectonic geographical region, at the northeast part of the Gulf of Corinth in Greece. Beachrock deposits that form a barrier between the salt pond and the marine environment seem to play an important role in the evolution of the area. The chronological framework was set at around 3100 cal. BP by four 14C radiocarbon dates, and the evolutionary model that was established indicates four different changes taking place during this period at the study area. From around 3100 to 1600 cal. BP, a transition from a closed to an open lagoonal environment was identified, interrupted by a fluvial terrestrial deposit at around 2500 cal. BP. A shift toward a closed lagoonal system at around 1600 cal. BP and the establishment of a salt pond environment seem to correlate with tectonic activity. The study provides important information about the evolution of coastal landscape in such a tectonic active region and points the interaction between regional human activity and climatic changes during the late-Holocene period.
The interactions of the different monsoon systems across Southeast Asia create extreme climate phenomena. Central Vietnam, located near the centre of this transitional region, has encountered ...numerous effects. As a result, its sediments from lakes or speleothems are valuable archives for interpreting past climate variability. However, there is still a lack of high-resolution paleoenvironmental and palaeoclimatic reconstructions during the Holocene in Vietnam. Our study presents a paleoenvironmental diatom-based record of sediment cores collected from Biển Hồ maar lake (14°03′N, 108°00′E) in the Central Highlands of Vietnam covering nearly the entire Holocene. Based on changes in diatom assemblages in the sediment sequence, we identified two periods of the Early Holocene (~11,700–7800 cal BP) and the Mid- to Late-Holocene (~7800–360 cal BP), which mark a remarkable shift in the environment around Biển Hồ. Alternations of key diatom species during the Early Holocene indicate intensity variations between water-mixing and thermal stratification mechanisms in meso-eutrophic conditions. During the Mid- to Late-Holocene, the complete dominance of Aulacoseira granulata var. granulata implies year-round destratification and intense mixing of the lake water column in a permanently eutrophic environment. Its morphological variability reveals intervals of dry environmental conditions driven by pronounced droughts across the Asian continent.
An understanding of past climatic variability at regional to local scales is mandatory for a proper evaluation of current and potential future repercussions from global climate change. The Southeast ...Asian tropics remain severely under-represented in paleoenvironmental and paleoclimatic reconstructions, although a few recent paleoclimate studies evaluated the variability, position and strength of the main Asian monsoon systems at different timescales from modern records to the last 15,000 years. Comparable data from Việt Nam, however, are scarce although Việt Nam and its Central Highlands are critically located at the intersection of the East Asian Summer Monsoon and the Indian Summer Monsoon with highly important socio-ecological consequences from changes in the climate system. This study presents a high-resolution sedimentary climate record from Ea Tyn Lake in Việt Nam’s Central Highlands covering the last 1250 years. Using geochemical and sedimentological proxies and principal component analysis, we reconstructed at least 12 drought events, some of which appear to be of supraregional significance as they coincide with historically documented droughts in India, China, and Cambodia. Beyond tracking short-term climate events, the Rb/Sr elemental ratio along the Ea Tyn Lake sediment sequence reflects long-term monsoon variability throughout the last millenium, which was previously only reconstructed via δ18O speleothem records from China and India. Our Ea Tyn Lake record shows that the East Asian Summer Monsoon was relatively strong between ~1000 and 1350 cal CE and weaker between 1350 and 1850 cal CE, followed by renewed intensification after ~1850 cal CE.
In this study, we present a modeling approach that investigates how much cultivable land was required to supply a society and whether societies were in need when environmental conditions ...deteriorated. The approach is implemented for the North-Eastern Peloponnese and is based upon the location of Late Helladic IIIB (1300-1200 BCE) archaeological sites, an assessment of their sizes, and a proposed diet of the people. Based on these information, the areal requirement of each site is calculated and mapped. The results show that large sites do not have sufficient space in their surroundings in order to supply themselves with the required food resources and thus they depended on supplies from the hinterland. Dry climatic conditions aggravate the situation. This indicates that potential societal crisis are less a factor of changing environmental conditions or a shortage of arable land but primarily caused by socio-economic factors.
During the last few decades, X-ray attenuation systems have been established as standard techniques in geosciences and as excellent scientific tools for the analysis of sedimentary facies and ...structures. In the present study, we use two non-destructive and high-resolution systems (computed tomography, X-ray fluorescence) to address all sedimentological facies and structural characteristics on a 6 m long, partly laminated sediment record, from Vouliagmeni lake, located at the eastern part of the Corinth Gulf, Greece. Vouliagmeni lake is the deepest coastal lake in Greece, and its location is of great importance since it is located in one of the most tectonically active regions in the world. The chronological framework of the retrieved sediment sequence spans the last 12,000 years, with alternations of laminated and non-laminated sections. The annual accumulation of the laminated sequences was determined through the radionuclide concentration of 14 samples. Scanning tomography was performed with a medical CT scanner and a μCT scanner, aiming to compare the potentials and variations of both methods. Lamination boundaries, event layers (turbidites) and sediment deformations were distinguished through processing the extracted 3D rendered volumes, after applying ranges depending on Hounsfield (HU) values. Microscopic analysis revealed three main layer types in the varve sequences that were examined, attributing to summer/spring, autumn and winter deposits. Statistical analysis of the elemental composition, magnetic susceptibility (MS) measurements and HU values revealed three clusters/facies, reflecting climatic and in-lake hydrological changes. Cluster A emulates sedimentation during arid conditions, while Cluster B reflects humid conditions with increased precipitation and erosion. Cluster C represents sequences with homogenous Ca-rich sediment. Our proposed workflow highlights the possible correlation between the non-destructive variables that were measured, but also the variations and applications of each method and software used during this study.
Fossils represent invaluable data to reconstruct the past history of life, yet fossil-rich sites are often rare and difficult to find. The traditional fossil-hunting approach focuses on small areas ...and has not yet taken advantage of modelling techniques commonly used in ecology to account for an organism's past distributions. We propose a new method to assist finding fossils at continental scales based on modelling the past distribution of species, the geological suitability of fossil preservation and the likelihood of fossil discovery in the field, and apply it to several genera of Australian megafauna that went extinct in the Late Quaternary. Our models predicted higher fossil potentials for independent sites than for randomly selected locations (mean Kolmogorov-Smirnov statistic = 0.66). We demonstrate the utility of accounting for the distribution history of fossil taxa when trying to find the most suitable areas to look for fossils. For some genera, the probability of finding fossils based on simple climate-envelope models was higher than the probability based on models incorporating current conditions associated with fossil preservation and discovery as predictors. However, combining the outputs from climate-envelope, preservation, and discovery models resulted in the most accurate predictions of potential fossil sites at a continental scale. We proposed potential areas to discover new fossils of Diprotodon, Zygomaturus, Protemnodon, Thylacoleo, and Genyornis, and provide guidelines on how to apply our approach to assist fossil hunting in other continents and geological settings.
In this study, soil and aquatic sediments were sampled in the Aetoliko Lagoon and its catchment area, which is exclusively dominated by olive orchards. For the first time in Greece, soil as well as ...sediments samples of one coherent protected aquatic ecosystem were directly compared. In order to determine the influence that the usage of copper-based fungicides have on the lagoon sediments and on the soils of the surrounding area, twenty five (25) soil samples from different olive orchards that are bordering the water body and ten (10) sediment samples from the bottom of the lagoon were taken. The samples were analyzed for total copper content (total digestion) and extractable copper (diethylenetriaminepenta acetic acid, DTPA, extraction method). Furthermore, soil/sedimentological and geochemical analyses such as pH, grain size, total organic carbon, total sulfur, total nitrogen, and calcium carbonate content were carried out. The results show that the total copper in soils ranges from 58.37 to 671.33 mg kg−1. In addition the DTPA-extractable copper in soils has an average value of 45.00 mg kg−1. The average value of total copper in soils (286.24 mg kg−1) is higher than the threshold value for the Cu concentration (100 mg kg−1) set by the EU countries. Total copper content in the lagoon sediments is lower than in soils and varies between 43.85 mg kg−1 and 71.87 mg kg−1. The DTPA-extractable copper in sediments is in low ranges from 0.14 to 0.60 mg kg−1. On average, the total copper value for the lagoon sediments (55.93 mg kg−1) exceeds the Toxicity Screening Value (25.20 mg kg−1) for Cu in freshwater sediments. From the present study, it is clear that, although the copper in soils of the surrounding lagoon area exceeds the threshold limit for ecological risk, the lagoon sediments are influenced in a smaller degree. Our study can be used as a valuable reference and baseline for future studies on the environmental monitoring of the Aetoliko lagoon, as well as for studies in similar ecosystems.
This study presents a Holocene multi-proxy record from Lake Vouliagmeni, eastern Gulf of Corinth, Greece. The lake is subjected to intense climatic and tectonic forces causing stratigraphic ...variations with laminated sediments frequently interrupted by homogenous sections and event deposits. Lamination couplets consist of aragonite layers alternating with detrital and organic residues formed during periods of seawater intrusion and stratification of the lake water. The discontinuous occurrence of laminated deposits excludes a varve based chronology from being established but highlights the susceptibility of the lake to record environmental and climatic changes. Our synthesis model for regional climatic reconstruction and local environmental changes derives from δ18O and δ13C data from laminated and homogenous sediments studied separately and depending on the dominant carbonate mineral. This is further strengthened by high-resolution geochemical proxies, diatom and sedimentological data. Regional climatic signals from key sites and possible links to the Lake Vouliagmeni record are explored in response to atmospheric circulation patterns. Phases of overall humid conditions are recorded by increased inflow of siliciclastic material to the lake and negative δ18Obulk values. In contrast, periods of marine intrusion and enhanced evaporation are recorded by aragonite precipitation, positive δ18OAr values and laminations. The laminations formed in the lake seem to occur during periods of sea water intrusion into the lake, which led to pycnocline stabilization and stratified lake waters.
•δ18Obulk and δ13Cbulk reflect variations in precipitation and detrital influx.•Periods of stratified lake waters and pycnocline stabilization are displayed with aragonite laminations.•Humid phases are recorded from 10 to 7.8, 5.2 to 4.4 and 1.5 to 0.2 ka cal BP with lower δ18Obulk.•Increased summer temperatures occur from 7.4 to 6.8 and 5.4 to 4.5 ka cal BP and are reflected with increased carbonate accumulation.
The onset of the Bronze Age (approximately 4150 yrs cal. BP) in the southern Lake Garda region (N-Italy) is marked by an increase in the number of settlements and by the widespread adoption of ...pile-dwelling building techniques. The prominence of this phenomenon polarized the attention of local palaeoenvironmental investigations. As a result, pre-Bronze age landscape and climate dynamics have been investigated to a lesser degree. In an attempt to address this disparity, our contribution focuses on the period between ∼7100 and ∼3800 yrs cal. BP, i.e. approximately between Early Neolithic and Early Bronze Age. The location of our analysis is the former lake of Bande di Cavriana (Mantua). Multi-proxy investigations highlight few major climatic shifts prior to the Bronze Age onset. A first transition into more warm/dry conditions is recorded between ∼6300 and 6100 yrs cal. BP. Similar conditions occur again after ∼4600 yrs cal. BP, peaking at ∼4300 yrs cal. BP. Speculatively, taking into account dating uncertainties, this second shift might represent the local expression of the ‘4.2Ka’ event. A marked transition into a colder/more humid situation occurs then after ∼4300 yrs cal. BP and persists into the Bronze Age. Major vegetational changes begin during the Neolithic with the steady rise of Carpinus betulus pollen (from ∼5700 yrs cal. BP). A more rapid expansion of this taxon after ∼5100 yrs cal. BP might reflect shifts in forest exploitation strategies during the Copper Age (e.g. coppicing) or changes in the ruminant fauna (e.g. grazing vs. browsing habits), arguably due to human intervention. Nonetheless, pollen grains of anthropogenic indicators appear with consistent frequency only since the Bronze Age. The establishment of the Bande di Cavriana pile dwelling (∼3950 yrs cal. BP) is marked by declining arboreal pollen values and growing anthropogenic taxa. This behavior likely reflects a more intense landscape exploitation (deforestation, expansion of arable fields and meadows), although an influx of herbaceous pollen from near-site activities (e.g. cereal processing, garbage dumping) should not be overlooked.
•Climate and land cover changes are investigated between ∼7100 and 3800 cal. BP.•A first transition into warmer/more arid conditions occurs between ∼6300 and 6100 cal. BP.•A second warm/arid event begins ∼4600 cal. BP and peaks at ∼4300 cal. BP.•The Carpinus betulus rise after ∼5100 cal. BP was arguably favored by human intervention.•The Bronze Age onset (∼4150 cal. BP) occurs during a marked colder/wetter shift.
PDF
