Late Glacial Early Holocene Research Articles

Dynamic Holocene glacial history of St. Jonsfjorden, Svalbard

Evidence of a dynamic Holocene glacial history is preserved in the terrestrial and marine archives of St. Jonsfjorden, a small fjord‐system on the west coast of Spitsbergen, Svalbard. High‐resolution, remotely sensed imagery from marine and terrestrial environments was used to construct geomorphological maps that highlight an intricate glacial history of the entire fjord‐system. The geomorphology and stratigraphy indicate an early Holocene local glacier advance constrained to the Lateglacial–early Holocene transition. Identification and 14C dating of the thermophilous bivalve mollusc Modiolus modiolus to 10.0±0.12 cal. ka BP suggest a rapid northward migration of the species shortly after deglaciation. Further evidence enhances the understanding of the onset and subsequent climax of the Neoglacial‐Little Ice Age in inner St. Jonsfjorden. The present‐day terminus of Osbornebreen, the dominating glacier system in St. Jonsfjorden, is located over 8.5 km up‐fjord from its Neoglacial maximum extent. Cross‐cutting relationships suggest subsequent advances of all the smaller glaciers in the area following the break‐up of Osbornebreen. Glacial deposits, landforms and their cross‐cutting relationships observed in both terrestrial and marine settings imply a complex and highly dynamic environment through the later part of the Holocene.

Climate and Fuel Controls on North American Paleofires: Smoldering to Flaming in the Late-glacial-Holocene Transition.

Smoldering and flaming fires, which emit different proportions of organic (OC) and black carbon (BC, in the form of char and soot), have long been recognized in modern wildfire observations but never in a paleo-record, and little is known about their interactions with climate. Here we show that in the late glacial-early Holocene transition period, when the climate was moist, relatively high quantities of char were deposited in Linsley Pond, Connecticut, USA while soot was more abundant during the warmer and drier early Holocene interval. The highest soot mass accumulation rates (MARs) occurred at the beginning of the Holocene as fuel availability increased through the climatic transition when boreal forests were locally extirpated. These variations with time are related to the different formation pathways of char and soot, which are governed by combustion efficiency. This study provides an approach for differentiating smoldering from flaming combustion in paleo-wildfire reconstructions. Our results suggest that climate and fuel loads control the occurrence of different wildfire types and precipitation may play a key role.

Pleistocene leopards in the Iberian Peninsula: New evidence from palaeontological and archaeological contexts in the Mediterranean region

This study analyses the fossil record of leopards in the Iberian Peninsula. According to the systematic and morphometric features of new remains, identified mainly in Late Pleistocene palaeontological and archaeological sites of the Mediterranean region, they can be attributed to Panthera pardus Linnaeus 1758. The findings include the most complete leopard skeleton from the Iberian Peninsula and one of the most complete in Europe, found in a chasm (Avenc de Joan Guitón) south of Valencia. The new citations and published data are used to establish the leopard's distribution in the Iberian Peninsula, showing its maximum development during the Late Pleistocene. Some references suggest that the species survived for longer here (Lateglacial-Early Holocene) than in other parts of Europe. Finally, the contexts of appearance and origin of leopard remains are described and the processes of interaction with prehistoric human groups are assessed.

Effects of past climate variability on fire and vegetation in the cerrãdo savanna of the Huanchaca Mesetta, NE Bolivia

Abstract. Cerrãdo savannas have the greatest fire activity of all major global land-cover types and play a significant role in the global carbon cycle. During the 21st century, temperatures are projected to increase by ~ 3 °C coupled with a precipitation decrease of ~ 20%. Although these conditions could potentially intensify drought stress, it is unknown how that might alter vegetation composition and fire regimes. To assess how Neotropical savannas responded to past climate changes, a 14 500-year, high-resolution, sedimentary record from Huanchaca Mesetta, a palm swamp located in the cerrãdo savanna in northeastern Bolivia, was analyzed with phytoliths, stable isotopes, and charcoal. A non-analogue, cold-adapted vegetation community dominated the Lateglacial–early Holocene period (14 500–9000 cal yr BP, which included trees and C3 Pooideae and C4 Panicoideae grasses. The Lateglacial vegetation was fire-sensitive and fire activity during this period was low, likely responding to fuel availability and limitation. Although similar vegetation characterized the early Holocene, the warming conditions associated with the onset of the Holocene led to an initial increase in fire activity. Huanchaca Mesetta became increasingly fire-dependent during the middle Holocene with the expansion of C4 fire-adapted grasses. However, as warm, dry conditions, characterized by increased length and severity of the dry season, continued, fuel availability decreased. The establishment of the modern palm swamp vegetation occurred at 5000 cal yr BP. Edaphic factors are the first-order control on vegetation on the rocky quartzite mesetta. Where soils are sufficiently thick, climate is the second-order control of vegetation on the mesetta. The presence of the modern palm swamp is attributed to two factors: (1) increased precipitation that increased water table levels and (2) decreased frequency and duration of surazos (cold wind incursions from Patagonia) leading to increased temperature minima. Natural (soil, climate, fire) drivers rather than anthropogenic drivers control the vegetation and fire activity at Huanchaca Mesetta. Thus the cerrãdo savanna ecosystem of the Huanchaca Plateau has exhibited ecosystem resilience to major climatic changes in both temperature and precipitation since the Lateglacial period.

Lateglacial–early Holocene vegetation history of the Tiber delta (Rome, Italy) under the influence of climate change and sea level rise

A new pollen and plant macrofossil record from Pesce Luna (Fiumicino, Rome) provides the reconstruction of the vegetation history in the Tiber Delta region between 13,000 and 8400cal. BP. Marked fluctuations of hydro- and hygrophytes depict a variety of marsh–lagoon conditions reflecting marked changes in water-table level and salinity, determined by the transition from a continental environment with a strong fluvial influence, to a freshwater/brackish environment typical of an inner estuary, followed by a saline outer estuary environment. Both deciduous (mostly Quercus, Corylus, Tilia, Ulmus and Fagus) and evergreen elements (evergreen Quercus and Ericaceae) were already present during the Younger Dryas, being possibly enhanced by water availability and the vicinity to the sea that may have favoured long-term persistence of tree populations. Evergreen populations progressively increased during the early Holocene. Despite the strong effect of local environmental processes, a comparison of the Pesce Luna pollen record with other southern European sequences and the GISP2 δ18O record indicates that the vegetation development was also influenced by centennial-scale climate processes acting at global scale. In particular, a mid-Younger Dryas climate reversal can be recognized at Pesce Luna, similar to other Mediterranean sites both in marine and continental environments. This study improves our knowledge on the vulnerability and resilience of coastal-estuarine wetlands to the global warming and sea level rise of the last deglaciation, adding insights into the response of coastal environments to the predicted global climate changes.

Climate and abrupt vegetation change in Northern Europe since the last deglaciation

A long-standing question in palaeoecology has been to determine the importance of climate driving vegetation change since the last deglaciation. Here, we investigate the local-to-regional dynamics of vegetation change during the Lateglacial and the Holocene in Northern Europe. We extracted sites from the European Pollen Database and used the squared-chord distance (SCD) dissimilarity metric to identify time periods of high pollen assemblage turnover representing periods of abrupt vegetation change. In addition, a set of generalized additive mixed models were applied to investigate the underlying dynamics of two periods of higher rates of turnover: the Younger Dryas–early Holocene transition (YD-EH; 11.6–9.0 kyr) and early–middle Holocene (EMH; 9.0–6.0 kyr). Results revealed a high frequency of turnover events between 12.75–11.5, 10.75–11, 10.25–10, 7.75–7.25, 3.25–3.0 and 1.75–.25 kyr. Furthermore, there was a strong linear relationship between pollen assemblage turnover and large directional temperature changes during the abrupt climate changes of the Lateglacial–early Holocene transition. In contrast, patterns of turnover during the Holocene were generally site-specific and during the EMH, we found evidence that the vegetation response was non-linear and highly variable across and between regions. Our results have implications for understanding the relationship between threshold dynamics and the amplitude of an extrinsic forcing. Across the Lateglacial–early Holocene boundary, the rate and magnitude of temperature change were large enough to override any site-specific thresholds, resulting in large assemblage turnovers. In contrast, during the Holocene, the vegetation response was mediated by intrinsic factors, which resulted in varying turnover rates between regions. The next research challenge is to attempt to determine whether it is possible to appreciate the velocity and rate of change that is necessary to result in these different responses and whether this rate is the same across biomes.

A Late Glacial–Early Holocene multiproxy record from the eastern Fram Strait, Polar North Atlantic

The paleoceanographic development of the eastern Fram Strait during the transition from the cold Late Glacial and into the warm Early Holocene was elucidated via a multiproxy study of a marine sediment record retrieved at the western Svalbard slope. The multiproxy study includes analyses of planktic foraminiferal fauna, bulk sediment grain size and CaCO3 content in addition to Mg/Ca ratios and stable isotopes (delta C-13 and delta O-18) measured on the planktic foraminifer Neogloboquadrina pachyderma. Furthermore paleosubsurface water temperatures were reconstructed via Mg/Ca ratios (sSST(Mg/Ca)) and transfer functions (sSST(Transfer)) enabling comparison between the two proxies within a single record. The age model was constrained by four accelerator mass spectrometry (AMS) C-14 dates. From 14,000 to 10,300 cal yr B.P. N. pachyderma dominated the planktic fauna and cold polar sea surface conditions existed. The period was characterized by extensive sea ice cover, iceberg transport and low subsea surface temperatures (sSST(Transfer) similar to 2.1 degrees C; sSST(Mg/Ca) similar to 3.5 degrees C) resulting in restricted primary production. Atlantic Water inflow was reduced compared to the present-day and likely existed as a subsurface current. At ca. 10,300 cal yr B.P. Atlantic Water inflow increased and the Arctic Front retreated north-westward resulting in increased primary productivity, higher foraminiferal fluxes and a reduction in sea ice cover and iceberg transport. The fauna rapidly became dominated by the subpolar planktic foraminifer Turborotalita quinqueloba and summer sSST(Transfer) increased by similar to 3.5 degrees C. Concurrently, the sSST(Mg/Ca) recorded by N. pachyderma rose only similar to 0.5 degrees C. From ca. 10,300 to 8600 cal yr B.F. the average sSST(Mg/Ca) and sSST(Transfer) were similar to 4.0 degrees C and similar to 55 degrees C, respectively. The relatively modest change in sSST(Mg/Ca) compared to sSST(Transfer) can probably be tied to a change of the main habitat depth and/or shift in the calcification season for N. pachyderma during this period.

Coastal glaciers advanced onto Jameson Land, East Greenland during the late glacial–early Holocene Milne Land Stade

We report on 10Be and optically stimulated luminescence ages from moraines and glaciolacustrine sediments on eastern Jameson Land, East Greenland. Sampled landforms and sediment are associated with advances of outlet glaciers from the local Liverpool Land ice cap situated in the coastal Scoresby Sund region. Previous studies have tentatively correlated these advances with the Milne Land Stade moraines, which are prominent moraine sets deposited by mountain glaciers in the inner Scoresby Sund region. Recent constraints on the formation of the outer and inner of these moraines have suggested two advances of local glaciers, one prior to or during the Younger Dryas and another during the Preboreal. In this paper, we test the correlation of the Liverpool Land glacial advance with the Milne Land Stade. Our results show that outlet glaciers from the Liverpool Land ice cap reached ice-marginal positions marked by moraines in east-facing valleys on Jameson Land sometime during late glacial–early Holocene time (ca. 13–11 Kya). This confirms the correlation of these moraines with the Milne Land Stade moraines described elsewhere in the Scoresby Sund region.Keywords: Greenland; Jameson Land; glaciation; Milne Land Stade; cosmogenic exposure dating; luminescence dating.(Published: 10 January 2014)Citation: Polar Research 2014, 33, 20313, http://dx.doi.org/10.3402/polar.v33.20313

A Late Younger Dryas–Early Holocene tephrostratigraphy for Fosen, Central Norway

ABSTRACTA number of rapid climate oscillations occur during the Lateglacial–Early Holocene, 15–8 ka BP period and a well‐developed tephrostratigraphy in association with these oscillations increases the possibilities to correlate climate archives around the North Atlantic. This paper presents a tephrostratigraphy for Fosen peninsula, Central Norway. Both the Vedde Ash ca.12.1 ka BP and the Saksunarvatn Ash ∼10.3 ka BP are important isochrones for correlations of Late Quaternary palaeoenvironmental records in the North Atlantic region and have been assigned ages in GICC05. Beside these tephras we have also identified a new tephra, the Fosen Tephra, with a Borrobol‐type geochemistry that occurs above both the Vedde Ash and the Saksunarvatn Ash with an age ∼10.2 ka BP. Several tephras with Borrobol‐type geochemistry have been identified around the North Atlantic. One group is the Borrobol/Penifiler tephras dated to Greenland Interstadial‐1 and another group is dated to the Early Holocene. We suggest that some of the Early Holocene Borrobol‐type tephras and the Fosen Tephra may actually be the same layer. If so, the Fosen Tephra is spread over a large area of the North Atlantic and has the potential to become an important marker for short‐term climate variability in Scandinavia and in the northern hemisphere.

A comparison of reconstructions based on aquatic and terrestrial beetle assemblages: Late glacial–Early Holocene temperature reconstructions for the British Isles

This paper presents the results of a study of MCR estimates of mean July temperature (TMAX) during the late glacial interval from four British sites, comparing estimates based on terrestrial and aquatic species. We have generated precise age models for three of these datasets, and have found that in most cases the terrestrial-based estimates agree with the aquatic-based estimates. The temperatures across the late glacial are consistent and warm in the early interstadial. However, differences exist in the later interstadial where Llanilid seems to be slightly warmer than either St Bees or Gransmoor. The small-scale discrepancies between aquatic and terrestrial beetle MCR temperature estimates that were found from these sites appear to occur during the transition into the late glacial interstadial, during the transition into the Younger Dryas cooling, and during the Younger Dryas interval. We tentatively attribute these discrepancies to the presence of meltwater from snowbanks surrounding the study sites during the stated intervals, and suggest that MCR studies of late glacial beetle assemblages from northwest Europe should adopt the protocol of generating separate aquatic and terrestrial estimates, for comparative purposes.

Late Glacial–early Holocene environmental changes in Charzykowskie Lake (northern Poland) based on oxygen and carbon isotopes and Cladocera data

Based on isotopic and cladoceran investigations of a 6-m-long sediment core, a reconstruction of paleoenvironmental dynamics in Charzykowskie Lake (northern Poland) is proposed. The sediments consist of sandy silts at the bottom, followed (in upward succession) by gyttja characterized by increasing CaCO3 content. The measured δ18O values oscillate from −9.3 to −5‰ and δ13C from – 5.7 to +0.4‰. We identify 24 taxa of subfossil Cladocera and six phases (CAZ) of faunal development. Isotopic and cladoceran data together with detrended correspondence analyses (DCA) allow reconstruction of the environmental conditions, particularly changes in water level, temperature, and trophic status, during the Late Glacial and early Holocene. The lowest water temperature, connected with the inflow of cold melt water, occurred in the Late Glacial and Preboreal period. Since the Boreal period, gradual warming is observed and expressed through a positive trend in both δ18O and δ13C values and changes in Cladocera species assemblages. The lake was deepest at the beginning of the Holocene as a result of dead ice melting (supply of melt water; lowering of lake bottom) and/or precipitation increase (change in atmospheric circulation). During the Boreal period, the fall in water level takes place despite the opposite trend observed at nearby sites. In addition, the cladoceran data indicate an initial decrease in trophic conditions from α-mesotrophic to oligotrophic and then an increase to the β-mesotrophic state.

Climate, catchment runoff and limnological drivers of carbon and oxygen isotope composition of diatom frustules from the central Andean Altiplano during the Lateglacial and Early Holocene

Diatom-based carbon and oxygen isotope analyses (δ13Cdiatom and δ18Odiatom) were performed on diatom-rich laminated sediments of Lake Chungará (Andean Altiplano, northern Chile) deposited during the Lateglacial and Early Holocene (12,400–8300 cal years BP) to reconstruct climate change and environmental response across this major climate transition. The δ13Cdiatom data show both centennial-to-millennial scale changes related to fluctuations in lake productivity and CO2 concentration in the lake water, and variations in carbon sources to the lake through time. The δ18Odiatom data reflect changes in lake hydrology and climate. The combination of δ13Cdiatom and δ18Odiatom data reveals interactions between the internal lake processes and its catchment runoff. During wet periods (low δ18Odiatom values) δ13Cdiatom indicates an enhanced contribution of allochthonous carbon, whereas during dry periods (high δ18Odiatom) δ13Cdiatom values suggest more autochthonous carbon production and recycling. These decadal-to-centennial oscillations are not recognized after 10,000 cal years BP, possibly as a result of ENSO-like phenomenon weakening. Humid conditions during the Lateglacial–Early Holocene transition (12,400–10,100 cal years BP) were possibly due to the establishment of La Niña-like conditions in the tropical South Pacific. Whereas, dry conditions in the Early Holocene (10,100–9100 cal years BP) may be caused by the northward migration of the ITCZ due to both ENSO-like weakening and an insolation minimum. Finally, a return to humid conditions at the end of the Early Holocene (9100–8300 cal years BP) is coincident with an increase in summer insolation.

A comparison of late glacial-early Holocene fluctuations of Greenland Ice Sheet outlet glaciers with nearby mountain glaciers in central east Greenland

A comparison of late glacial-early Holocene fluctuations of Greenland Ice Sheet outlet glaciers with nearby mountain glaciers in central east Greenland

Tephra stratigraphy on the North Icelandic shelf: extending tephrochronology into marine sediments off North Iceland

Tephra stratigraphical and tephrochronological studies of marine core MD99‐2275 on the North Icelandic shelf have revealed 58 new tephra horizons within the last 7050 cal. a BP, bringing the total number of identified tephra layers to 76. So far, over 100 tephra layers have been identified in the entire core spanning the last 15 000 years. The majority of the newly identified tephra layers are basaltic in composition and originate from the most active volcanic systems in Iceland, namely Grímsvötn, Veidivötn‐Bárdarbunga and Katla. A total of 40 tephra layer land–sea correlations have been made within this time period, of which 16 represent absolutely dated tephra markers. In addition, two tephra marker series are revealed in the marine sediments and in the terrestrial tephra stratigraphy, located between c. 2300–2600 and between 5700–5900 years. For the last 15 000 years, 21 tephra markers have been recognized. The marine tephra layer frequency (TLF) reveals two peaks, within the last 2000 years, and between 5000 and 7000 years ago. It shows the same general characteristics as the terrestrial TLF curve in Iceland, which indicates that marine sediments can yield important information about volcanism in Iceland. This is useful in time segments in which terrestrial records are poor or non‐existent. The study contributes to a high‐resolution tephrochronological framework on the North Icelandic shelf, with core MD99‐2275 representing a potential stratotype section in the area, and for the northern North Atlantic–Nordic Seas region, as well as being an important contribution to the Lateglacial–early Holocene volcanic history of Iceland.

Multiproxy reconstruction of Late Pleistocene-Holocene environmental changes in coastal successions: microfossil and geochemical evidences from the Po Plain (Northern Italy)

Despite the overwhelming control exerted on worldwide coastal evolution by the Lateglacial-early Holocene sea-level rise, high-frequency rapid palaeoenvironmental changes are recorded within a thick postglacial succession buried beneath the southern Po Plain (Northern Italy). Amultidisciplinary study involving sedimentology, micropalaeontology (benthic foraminifers and ostracods), geochemistry (major, minor and trace elements) and radiocarbon dating (14C) on a 40m-long core (240-S5) retrieved inland of the Holocene beach ridges, allowed the reconstruction of articulate coastal scenarios and dynamics - including stages of drainage reorganization. An alluvial plain nourished by the Apenninic Savio River developed in response to low sea-level conditions during the last glacial period. During the first stages of deglaciation (Lateglacial period) the study area was flooded and a coastal plain evolved near the coeval lagoon basin. Subtle change in microfossil content documents the occurrence of a short-term progradational episode that led to the temporary establishment of more terrestrial conditions (likely attributed to the Younger Dryas event - ca. 12,500 cal years BP). Complex and unstable Lateglacial palaeoenvironmental scenarios, and a mixed contribution from two Apenninic rivers (Savio River and Fiumi Uniti system), are suggested by the geochemical composition of coastal sediments. A distinctive flooding event, possibly related to the MWP-1B, caused the abrupt replacement of the coastal plain by a barrier-lagoon system. This landward shift of facies was synchronous with a source area change from the Savio River to the Fiumi Uniti system, triggered by an important phase of drainage system reorganization. Short-term changes in microfossil content also highlight the occurrence of two early Holocene episodes of lagoon infilling not accompanied by significant changes in sediment composition. The complete infilling of lagoon, which evolved in a swamp basin, took place only after ca. 7,600 cal years BP. The establishment of hypohaline environmental conditions is supported by subtle changes in geochemical composition.

Cladocera response to Late Glacial to Early Holocene climate change in a South Carpathian mountain lake

This study explores changes in cladoceran composition in a high mountain lake of the Retezat (Lake Brazi), the South Carpathian Mountains of Romania, during the Late Glacial–Early Holocene (14,500–11,600 cal. yr. bp) transition using a paleolimnological approach. The lake had a species poor cladoceran community throughout this period. Daphnia longispina, Chydorus sphaericus and Alona affinis were the most common, showing marked fluctuations in their relative abundances through time. Distinct faunal response to warming at the Younger Dryas (YD)/Preboreal transition was recorded by increasing fossil densities and distinct community composition change: Alona affinis became dominant while numbers of Chydorus sphaericus dramatically decreased. In the Early Holocene, the productivity of Lake Brazi seem to have increased as reflected by higher numbers of Cladocera due to appearance of new species (Alona rectangula, A. quadrangularis and A. guttata) which are common in productive waters. Significant negative correlation was found between average dorsal length of daphnid ephippia and the NGRIP δ18O isotope values. Given the absence of fish predation, changes in Daphnia ephippia size were taken to indicate climatic change: larger ephippium size inferred cold conditions during the Late Glacial, while smaller size reflected climate warming during the Early Holocene. We conclude that Cladocera fossils are good indicators of climatic change that happened during the transition from the Late Glacial to the Holocene. We found that climatic conditions can be tracked either by size distribution of Daphnia ephippia (larger ephippium size under colder climate) and/or by community change of cladocerans.

Aeolian sequence and the archaeological record in the fuegian steppe, Argentina

A 20 m thick sequence of aeolian deposits and palaeosols, deposited above Neogene marine sediments adjacent to the shallow saline ephemeral Lake Arturo in interior Tierra del Fuego, is described. A deposit of archaeological stone artifacts and bones, the Lake Arturo 1 archaeological site, is located in a deflation hollow near the top of the aeolian sequence. The sequence of nine aeolian deposits, including eight palaeosols and capped by the contemporary soil, provides evidence of environmental changes which have occurred during the Holocene in the cold Fuegian steppe, beginning as early as the Late Glacial–Early Holocene transition. A chronostratigraphy is provided by guanaco ( Lama guanicoe) and Canidae bones embedded within palaeosols and organic matter content, radiocarbon dated from 9951 ± 59 BP (11,304 cal. BP) at the base of the sequence to 434 ± 43 BP (471 cal. BP) near the top. A tephra layer between Palaeosols 4 and 5 is interpreted from its geochemical fingerprint as the product of one of the mid-Holocene eruptions of Mt. Burney, located in the Southern Patagonian Andes. It is suggested that the accumulation of the aeolian sediments occurred throughout most of the Holocene, as a result of both local acquisition of fine particles derived from the weathering and erosion of the basal Neogene marine sediments, and deflation from the intermittently dry lake bed, as well as deposition of material transported by wind from more distant sources. The orientation of the aeolian deposits suggests a more northwesterly wind direction instead of the present westerlies. Weakly developed A horizons capping each of the sediment units suggest that the landscape was sensitive to environmental change, from more arid conditions when the aeolian deposits accumulated to brief periods of landscape stability when topsoil development occurred. Evidence of human occupation in Lake Arturo 1 is confined to the upper part of the sequence (ca. 500 years BP) and is interpreted as a place for primary butchering and raw material acquisition.

Molecular fingerprinting of wetland organic matter using pyrolysis-GC/MS: an example from the southern Cape coastline of South Africa

Pyrolysis–gas chromatography mass spectrometry (py-GC/MS) allows the characterisation of complex macromolecular organic matter. In lakes and wetlands this can potentially be used to assess the preservation/diagenesis and provenance of sediment organic matter. It can complement palaeoenvironmental investigations utilising ‘bulk’ sediment variables such as total organic carbon (TOC) and TOC/total nitrogen ratios. We applied py-GC/MS analyses to a ~32,000-year sediment record from the southern Cape coastline of South Africa. We used the results to evaluate the sources and extent of degradation of organic matter in this semi-arid environment. Marked down-core changes in the relative abundance of multiple pyrolysis products were observed. Correspondence analysis revealed that the major driver of this down-core variability in OM composition was selective preservation/degradation. Samples comprising highly degraded OM are primarily confined to the lower half of the core, older than ~12,000 years, and are characterised by suites of low-molecular-weight aromatic pyrolysis products. Samples rich in organic matter, e.g. surface sediments, are characterised by products derived from fresh emergent or terrestrial vegetation, which include lignin monomers, plant-derived fatty acids and long-chain n-alkanes. Pyrolysates from the late glacial-early Holocene period, approximately mid-way down the core are characterised by distinct suites of long-chain n-alkene/n-alkane doublets, which may reflect the selective preservation of recalcitrant aliphatic macromolecules and/or enhanced inputs of the algal macromolecule algaenan/polymerised algal lipids. Increased TOC, lower δ13C and increased abundance of more labile lignin and fatty acid products at the same depths suggest this period was associated with increased lake primary productivity and enhanced inputs of terrestrial OM. TOC is the only ‘bulk’ parameter correlated with the correspondence analysis axes extracted from the py-GC/MS data. Distinct fluctuations in TOC/total nitrogen ratio are not explained by variation in organo-nitrogen pyrolysis products. Notwithstanding, the study suggests that py-GC/MS has potential to complement palaeolimnological investigations, particularly in regions such as southern Africa, where other paleoenvironmental proxy variables in sediments may be lacking or equivocal.

Human-environment relationships during the Late Glacial-Early Holocene transition: some examples from Campania, Calabria and Sicily

An overview of faunistic records (i.e. of large mammals and molluscs) from some prehistoric sites of the Tyrrhenian regions of Southern Italy and Sicily (Grotta del Mezzogiorno, Grotta della Serratura, Grotta del Romito and Grotta d’Oriente) indicates an opportunistic human environmental exploitation in this region during the Late Glacial-Early Holocene transition. Patterns of faunal exploitation appear to be strongly controlled by combinations of palaeoclimatic conditions, specific orographic and geomorphological settings and sea-level fluctuations.

The palaeohydrological evolution of Lago Chungará (Andean Altiplano, northern Chile) during the Lateglacial and early Holocene using oxygen isotopes in diatom silica

AbstractOxygen isotopes of diatom silica and petrographical characterisation of diatomaceous laminated sediments of Lago Chungará (northern Chilean Altiplano) have allowed us to establish its palaeohydrological evolution during the Lateglacial–early Holocene (ca. 12 000–9400 cal. yr BP). These laminated sediments are composed of light and dark pluriannual couplets of diatomaceous ooze formed by different processes. Light sediment laminae accumulated during short‐term diatom blooms whereas dark sediment laminae represent the baseline limnological conditions during several years of deposition. Oxygen isotope analysis of the dark diatom laminae show a generalδ18O enrichment trend during the studied period. Comparison of theseδ18Odiatomvalues with the previously published lake‐level evolution suggests a correlation betweenδ18Odiatomand the precipitation:evaporation ratio, but also with the evolution of other local hydrological factors as changes in the groundwater outflow as well as shifts in the surface:volume ratio of Lago Chungará. The lake expanded (probably increasing this ratio) during the rising lake‐level trend due to changes in its morphology, enhancing evaporation. Furthermore, the lake's hydrology was probably modified as the groundwater outflow became sealed by sediments, increasing lake water residence time and potential evaporation. Both factors could cause isotope enrichment. © Natural Environment Research Council (NERC) copyright 2008. Reproduced with the permission of NERC. Published by John Wiley & Sons, Ltd.