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Historical climate change in southern England was investigated using ostracod oxygen-isotope (δ18O) records from two anthropogenic lakes in Hampshire, southern England. A strong relationship is observed between δ18Oostracod, δ18Oprecipitation and δ18Olake_water in the contemporary environment and therefore δ18Oostracod from the sedimentary record of these systems has the potential to reflect past climate variability. The possibility of these sites to act as archives of climate change through δ18Oostracod analysis is explored through the study of lake sediment cores that cover the period from the early 20th century onwards. Both lakes showed similar directionality of shifts in δ18Oostracod over this period, suggesting common driving mechanisms. Comparing δ18Oostracod timeseries to meteorological data is challenging in part because of the complexity with which climate parameters are recorded in the δ18Olake_water and consequently within lacustrine carbonates. Our findings highlight the potential of sediments from anthropogenic lakes to act as archives of past climate and indicate they may be an important resource for generating climatic reconstructions across the medieval to instrumental period, which the sediments of many anthropogenic lakes cover. Such climate reconstructions would greatly improve our spatial and temporal understanding of climate variability where instrumental data are unavailable and other natural archives are scarce. [ABSTRACT FROM AUTHOR]

Despite global and local evidence of significant precipitation changes since the Little Ice Age (LIA), their impact upon lake hydrology and surrounding vegetation has yet to be investigated in NW Anatolia. Moreover, the LIA, as a trigger to the social/political recession of the Ottoman Empire in the 17th century is expected to have these impacts. To address this important gap, we studied three cores from Lake Sünnet, a landslide-dammed high altitude lake with extreme sedimentation rates, by using a wide range of proxies including lithology, stable isotopes of O and C, diatoms, pollen, and ostracods. The LIA timespan of AD 1510–1750 is represented by poorly preserved diatom flora and scarce ostracod fauna that collectively suggest very shallow aquatic conditions. The period AD 1640–1710 within the LIA is standing out with higher Abies and total herb pollen percentages that denotes considerably cooler conditions. During and soon after this cold and dry period precisely overlapping the Maunder Minimum, the currently deep Lake Sülüklü in close vicinity was a dry lowland where tall trees were growing. Progressive warming/lake level rise in Lake Sünnet after the AD 1750s is suggested based on a continuous diatom record with increasing planktonic share, increase in diverse and warm demanding arboreal cover, and a positive shift in δ18O of the lake muds. Following the relatively dry/cold period of AD 1800–1850 (Dalton Minimum) when the lake level was stationary and Artemisia cover became the most expanded of the whole record, a relatively warmer climate has dominated the area until the end of the 20th century. [ABSTRACT FROM AUTHOR]

The shift toward wetter climatic conditions during the African Humid Period (AHP) transformed previously marginal habitats into environments conducive to human exploitation. The Turkana Basin provides critical evidence for a dynamic climate throughout the AHP (~15–5 kyr BP), as Lake Turkana rose ~100 m multiple times to overflow through an outlet to the Nile drainage system. New data from West Turkana outcrops of the late-Pleistocene to early-Holocene Galana Boi Formation complement and extend previously established lake-level curves. Three lacustrine highstand sequences, characterized by laminated silty clays with ostracods and molluscs, were identified and dated using AMS radiocarbon on molluscs and charcoal. This study records the earliest evidence from the Turkana Basin for the onset of AHP by at least 13.9 kyr BP. In addition, a depositional hiatus corresponds to the Younger Dryas (YD), reflecting the Turkana Basin's response to global climatic forcing. The record from Kabua Gorge holds additional significance as it characterized the time period leading up to Holocene climatic stability. This study contributes to the paleoclimatic context of the AHP and YD during which significant human adaptation and cultural change occurred. [ABSTRACT FROM AUTHOR]

The endorheic nature of Lake Trasimeno in combination with its position in central Italy makes it a relevant site to better constrain spatial differences in Holocene climatic variability in the Mediterranean area. Herein, we present a high-resolution ostracod record from the Holocene section of an 8.59-m-long sedimentary core, which is compared with historical data to distinguish anthropogenic and climatic signals. The occurrence, abundance and vanishing of ostracod species are directly controlled by lake-level variations, which are in turn related to global and regional climatic changes (i.e. moisture variations). The total organic carbon content as well as observed lithological changes provide additional information about Lake Trasimeno's hydrological and trophic conditions in the past. Most important variations have been identified at ca. 10,000 cal. yr BP, when the lacustrine basin changed from a temporary to a permanent waterbody (from Sarsicypridopsis aculeata to Candona angulata association). The highest lake level and the total absence of ostracods occur at around 9000 cal. yr BP. The recorded humid phase persisted up to ca. 4200 cal yr BP since when a lake-level decreasing trend started and continued until the present day (Candona angulata, Cyprideis torosa and Darvinula stevensoni associations). The frequency of changes in the relative abundance of the main species shows centennial variations (i.e. C. angulata, C. torosa and Darvinula stevensoni). As historical evidences yield that human interventions to control the lake level remained unsuccessful in the past, Lake Trasimeno records an almost pristine climatic signal during most of the Holocene, which is quite unusual in the highly populated Mediterranean area. [ABSTRACT FROM AUTHOR]

New detailed palynological and ostracodological analyses together with texture data from a sediment core drilled in Ostia Antica confirm the existence of the ancient Ostia harbour and its location by the Tiber River. Using the different proxies analysed in this work and chronologically framing the sediment record with three AMS radiocarbon dates, four phases have been singled out: pre-harbour, harbour bay under fluvial influence, more protected harbour basin and post-harbour phase. Ostracodology is used to reconstruct the marine versus freshwater influence in the basin. Palynology is used to reconstruct the plant landscape and the surrounding environment. Phases with low pollen concentration and expansions of NPPs suggest soil erosion and are alternated with quieter ones, where human impact was very clear. Deciduous oaks typical of coastal plain forests are the main taxon during the harbour phases. The occurrence of riparian trees increases in periods with low pollen concentration, high NPPs and very high pine percentages. These should be the periods in which important sediment inputs inside the harbour basin arrived and could be the expression of intense flooding phases. The comparison between the ostracod assemblages recovered in the two cores and has led to speculate a complex harbour structure. A separation could explain the micropalaeontological differences between the cores. Thus, we suggest that a pier must have been built in order to protect the inner harbour from the marine influence and to unload the goods transported by the big ships. [ABSTRACT FROM AUTHOR]

Contemporary climate dynamics of the circum-Caribbean region are characterised by significant precipitation variability on interannual and interdecadal timescales controlled primarily by El Niño Southern Oscillation (ENSO) and the Atlantic Multidecadal Oscillation (AMO). However, our understanding of pre-industrial climate variability in the region is hampered by the sparse geographic distribution of palaeoclimate archives. Here, we present a high-resolution reconstruction of effective precipitation for Barbuda since the mid-16th century, based on biostratigraphic and stable isotope analyses of fossil ostracods and gastropods recovered from lake sediment cores from Freshwater Pond, the only freshwater lake on the island. We interpret episodic fluctuations in shell accumulation in the sediment record to represent changes in the balance between precipitation and evaporation during the ‘Little Ice Age’ (LIA; ~1400–1850 CE) and Industrial (1850–present) periods. Comparisons between indices of reconstructed ENSO and AMO variability, the abundance of the freshwater gastropod Pyrgophorus parvulus and the δ18O records from ostracod calcite suggest that the relative influence of ENSO and AMO on long-term rainfall patterns in Barbuda has changed over the last 400 years. Our findings are in agreement with other high-resolution palaeoclimate studies that suggest that long-term changes in effective precipitation during the LIA were much more variable, temporally and spatially, than previously suggested. [ABSTRACT FROM AUTHOR]

A multiproxy record from Lake Parishan, SW Iran, shows human impact on the lake and its catchment over the last 4000 years. The Parishan record provides evidence of changes in lake hydrology, from ostracod, diatom and isotope analyses, that are directly linked to human activity in the catchment; recorded by pollen and charcoal and supported by regional archaeological and historical data. The lake ostracod fauna is particularly sensitive to human-induced catchment alterations and allows us to identify changes in catchment hydrology that are due to more than a simple change in precipitation: evaporation state. Oxygen isotope data from endogenic carbonates follow these faunal changes but also display a longer trend to more positive values through the period, coincident with regional patterns of water balance for the late-Holocene in the eastern Mediterranean. [ABSTRACT FROM AUTHOR]

A multiproxy analysis of lacustrine sediments cored in Grand-Case Pond at Saint-Martin, north of the Lesser Antilles archipelago, reveals three distinct climatic periods for the last 3700 years. From 3700 to ~2500 yr cal. BP and from 1150 yr cal. BP to the present, carbonate mud deposition occurred in connection with pond lowstands. These periods were also punctuated by severe drought events, marked by gypsum laminae, and hurricane landfalls, leading to marine sand inputs into the pond. The intermediate time interval, from 2500 to 1150 yr cal. BP, is typified by black organic mud deposition, suggesting that hypoxic to anoxic conditions prevailed at the pond bottom. These were probably linked with a perennial pond highstand and reflect more uniform and wetter climatic conditions than today. The carbon isotopic composition of the ostracod Perissocytheridea bisulcata shows that the lowest δ13C values are recorded during the hypoxic periods, as a consequence of bacterial recycling of isotopically depleted organic matter. Such a climatic history agrees closely with that documented from other records in the Caribbean area, such as the Cariaco Basin, central coast of Belize or Barbados. By constrast, discrepancies seem to emerge from the comparison between hurricane activity recorded at Saint-Martin on the one hand and Vieques (Puerto Rico) on the other hand. We explain this apparent contradiction by a balance between two distinct storm paths in response to latitudinal shifts of the Intertropical Convergence Zone (ITCZ). Stronger storm activity over the Gulf coast and the inner Caribbean Sea is favoured by a southern position of the ITCZ in connection with dry climatic conditions. Plausible links with the North Atlantic Oscillation (NAO) are also suggested. [ABSTRACT FROM PUBLISHER]

The shallow tidal Wairau coastal lagoons, New Zealand, are in a prime location for investigating the relative roles of tectonic and eustatic sea level on their palaeogeographic evolution. The Wairau lagoons are unique in New Zealand for their wide seasonal and tidal salinity range, from hyposaline (10-20 psu) to hypersaline (35-54 psu). Foraminiferal and ostracod associations are recognised, using Q-mode cluster analysis, living in and around these lagoons and detrended canonical correspondence analysis (DCCA) shows that their distributions are strongly correlated with tidal elevation and salinity. Analyses of the modern analogue faunal data combined with Holocene microfaunal data from five 2.5-9 m deep cores enables direct palaeoenvironmental interpretation of the fossil faunas and elucidation of the lagoons' palaeogeographic evolution. The area was inundated by rising eustatic sea level from 8.5 ka onwards, forming a fully marine, sheltered, subtidal bay. Sediment supply outpaced local tectonic subsidence and the bay filled with mud, shallowing to intertidal by 4.5-3.5 ka, still with an open mouth to the sea. Since then sediment supply has kept pace with 3-4 m of inferred tectonic subsidence. At ∼1.5 ka the calcareous-dominated foraminiferal faunas suddenly changed to agglutinate-dominated faunas, indicating a switch to a semi-closed lagoon linked to the Wairau River estuary, with highly varied salinity like today. We infer this was caused by northwards extension of the Wairau Boulder Bank across the bay's mouth in response to a sharp eustatic sea-level fall after 2 ka. Sediment supply switched to fluvially derived sand which built a flood-delta into the lagoon dividing it into three water bodies. Relative sea-level rise in the last 600 years from earthquake-related compaction (ad 1855) and accelerating eustatic rise (0.6 m) has resulted in increased marginal erosion of the lagoons and their re-amalgamation into one linked water body. [ABSTRACT FROM AUTHOR]

The recent discovery of one of the earliest Mesolithic occupation sites in northern Britain, at Howick on the Northumberland coast, in association with multiperiod archaeological evidence nearby, highlights the importance of UK coastal settings as focii of human occupation through the Holocene. Environmental evidence from a nearby river valley (8.15 m of sediment ranging in age from about 12 000 cal. BP to the present) records local and regional environmental change. Twenty-four radiocarbon dates based on plant macrofossils provide a strong chronological framework. Calcareous microfossil assemblages (foraminifera, ostracods) have been recovered from the fine-grained sediments, recording a change from marine through to brackish and eventually freshwater conditions between about 8200 and 6500 cal. BP. A preliminary pollen study of the core has permitted a reconstruction of the regional vegetation as it responded to climatic amelioration and human influence upon the landscape. Radiocarbon dating and sedimentological evidence indicates a major hiatus between approximately 11 000 and 8000 years BP (including the period of Mesolithic occupation), represented by a 30 cm layer of coarse sands and sandstone pebbles, probably the result of a significant high-energy event dated to about 8300 cal. BP. Although not a typical tsunami deposit, the age and context suggests that this may be associated with the Storegga Slide event, already well-documented along the eastern coast of Scotland. The sedimentary and biological remains at Howick record environmental change over much of the Holocene and are compared with other environmental change records from the region to provide an environmental framework for the archaeology of this coastline. [ABSTRACT FROM AUTHOR]

Palaeolimnological data (diatoms, ostracods, foraminifera, molluscs, aquatic pollen and lithology) from a radiocarbon dated sediment core from a saline lake, the Laguna de Medina, provide the first complete record of Holocene lake-level change for southwest Spain for the last c. 9000 cal. years. The lake has always been relatively shallow but has exhibited marked fluctuations in salinity and water depth, especially in the earlier record when oscillations culminate in maximum lake levels from c. 6960–6680 cal. BP (c. 6070–5830 BP), indicating enhanced early- to mid-Holocene humidity and a mid-Holocene humidity maximum. Prolonged shallowing thereafter reflects in part increased aridity in the later Holocene. Lake desiccation followed by a c. 800-yr phase (zone 2) of major limnological change commencing at c. 8000 cal. BP (c. 7200 BP), and a number of other abrupt desiccation events, are also noteworthy. The mid-Holocene maximum is consistent with widespread evidence for high lake levels around 6000 BP, but the underlying climatic mechanisms are uncertain; there is some evidence it may apply predominantly to the westerly (Atlantic) Peninsula, with earlier maxima in the east. Phases of abrupt limnological change show affinities with African data; as in African lakes, the ‘zone 2’ phase appears to be a response to global change centred on c. 8.1–8.2 cal. BP. Other correlations made are tenuous, due partly to the lack of preservation in the upper record of some of the proxies used. Other desiccation events currently appear to be of more local significance, reflecting high decadal- to century-scale climatic variability throughout the Holocene. [ABSTRACT FROM AUTHOR]

A high-resolution, multiproxy palaeolimnological record from the Manga Grasslands, northeastern Nigeria, spanning the last 5500 calendar years, reveals the episodic deterioration in Sahelian climate as significant biogeophysical thresholds were crossed. Desert-dust deposition began to increase |4700 cal. BP. Rainfall during the summer-monsoon season declined permanently after 4100 cal. BP. A further significant change in atmospheric circulation, giving rise to multidecadal to centennial-scale droughts and enhanced dust deposition, occurred |1500 cal. BP. Hence, the post-1968 Sahel drought is not unique. The prolonged arid episode that occurred around 1200–1000 cal. BP in Ethiopia, the Sahel and tropical Mexico may have been linked to an abrupt cooling event in the North Atlantic and to a cluster of intense El Nin. [ABSTRACT FROM AUTHOR]

The sedimentary record at Lake Vibysjön, Närke, eastern middle Sweden has been investigated. The lake basin is situated close to the Närke Strait where the main water exchange occurred between the Vänern basin and Baltic basin during the middle and late phases of the Yoldia Sea stage of the Baltic Sea (c. 10 000– 9500 14 C years BP). The area was deglaciated in a glaciomarine environment, as reflected by the occurrence of benthic calcareous fossils (foraminifera, ostracods and the mollusc Portlandia arctica (Gray)) in the lower-most clay units. The estimated date of deglaciation, 10 440 clay-varve years BP, suggests that a saline bottom- water current entered the Baltic basin shortly after the high areas south of Lake Vibysjön became free of ice. The brackish water fauna occurs during a regional Betula-Empetrum-Hippophaë pollen zone, which in southern Sweden is correlated with the early Preboreal. The isolation of the Lake Vibysjön basin is dated to 8100 14 C years BP, and occurred during the last part of the Ancylus Lake stage. Based on investigations of other basins in Närke, it is concluded that the Mastogloia Sea reached c. 62 m a.s.l. and that the Litorina Sea reached at least 60 m a.s.l. in the area studied. [ABSTRACT FROM AUTHOR]

Large ranges of 13C/12C and 18O/ 16O ratios are found among modem ostracods from lakes in Jamaica and Mexico. If their calcite carapaces grew in isotopic equilibrium with the lake water, then the main period of carapace formation was probably in the cooler and/or wetter months. Differences in δ13C and δ18 O values between ostracods from different sites relate to spatial variations in the composition of the lake water, and differences between species at the same site probably reflect differences in organic photosynthesis or decay among the micro-habitats occupied by the species. There nevertheless remain significant variations in both δ13C and δ18O among modern valves of the same species at the same site; a consequence of the temporal and spatial variation in lake water and the fact that ostracods form their carapace over a short period. Individual valves from a 1-cm section of a sediment core show that the isotopic effects of changes in the rainfall versus evaporation status of a lake over a period of c. 102 years can be of a similar magnitude to changes recorded by bulk, fine-grained carbonate throughout the late Quaternary. These findings emphasize the need for caution when using isotopic data for single ostracod valves in palaeoclimatic studies. [ABSTRACT FROM PUBLISHER]

Sedimentary evidence, in the form of pollen, ostracod and radiocarbon-age data from three barrage tufa-dammed systems in the White Peak area of Derbyshire, is used to reconstruct the region's environmental history from 10000 to 4000BP. The data highlight the useful role that such fluvial systems can play in environmental reconstructions, through their ability to act as sumps for a wide range of proxy indicators, in a region where environmental change during the Holocene period has been relatively poorly documented. Pollen data suggest that the period of climatic amelioration following the last (Devensian) glaciation facilitated the spread of thermophilous woodland taxa on the White Peak, although there are some indications that the first immigrant trees were not established until a relatively late date. Forest clearance commencing during the mid-Holocene, and possibly as early as the late Mesolithic, was most probably to provide land for grazing, and was virtually complete by 4000BP. Ostracod data reveal fluctuations in discharge of the River Lathkill draining the White Peak, particularly lower flow rates after 7400 BP, which are difficult to explain simply in terms of climate change. [ABSTRACT FROM PUBLISHER]

An integrated analysis of molluscs, ostracods and pollen is presented from early Holocene lake marl at Llangorse Lake, Powys, South Wales. The mollusc and ostracod records reflect a littoral environment with increasing eutrophic conditions and a progressive shallowing of lake waters, although the record does not begin until around 9600 BP, probably due to the isolated location. The pollen profile provides evidence of both local and regional vegetational changes over the first two millennia of the present interglacial. Following climatic amelioration at the beginning of the Holocene, there was rapid colonization by trees and shrubs, with juniper widespread by 9800 BP, birch woodland by 9500 BP, and pine by 9300 BP. Late in the ninth millennium BP, hazel became established, to be followed during the course of the eighth millennium by elm and oak. There are indications in both the pollen and molluscan/ ostracod sequences of a relatively dry climatic regime during the early Holocene, while the pollen record suggests a short-lived climatic cooling in the middle of the tenth millennium BP. [ABSTRACT FROM PUBLISHER]

Palaeoecological studies of a 14C-dated, 6 m Livingstone core collected from Lac Ichkeul, N. Tunisia have allowed a palaeosalinity and vegetational history record for the last 3000 years to be derived from pollen, chemical and faunal evidence. The lake has been the subject of at least three different salinity regimes; saline (c. 3000 BP-c. 2000 BP), then brackish - fresh (c. 2000 BP-c. 1500 BP), and finally saline (c. 1500 BP-present). These changes in lake salinity are evaluated in the light of the known causes and the implications for the long-term future of the waterfowl populations discussed. An already disturbed Mediterranean woodland dominated by Quercus (cf. Q. suber) and Pinus (possibly P. halepensis) with a significant amount of Phillyrea characterizes the catchment vegetation from c. 3000 BP. From c. 1900 BP a degree of stabilization and regeneration occurs as woodland reinvades and ruderal indicators decline. However, from c. 1400 BP disturbance recommences and Quercus ilex pollen is seen for the first time. This is followed by further woodland interference resulting in the initial rise of Pistacia, but even this is eventually replaced by grassland as intensive cultivation of the Ichkeul catchment for Olea and winter wheat occurs. [ABSTRACT FROM PUBLISHER]