Late Quaternary Environmental Change Research Articles

Interpreting the mammal deposits of Cloggs Cave (SEAustralia),GunaiKurnaiAboriginal Country, through community‐led partnership research

AbstractPalaeontological animal bone deposits are rarely investigated through research partnerships where the local First Nations communities have a defining hand in both the research questions asked and the research processes. Here we report research undertaken through such a partnership approach at the iconic archaeological site of Cloggs Cave (GunaiKurnai Country, East Gippsland), in the southern foothills of SE Australia's Great Dividing Range.A new excavation was combined with detailed chronometric dating, high‐resolution 3D mapping and geomorphological studies. This allowed interpretation of a sequence of stratigraphic layers spanning from a lowermost excavated mixed layer dated to between 25,640 and 48,470 cal BP, to a dense set of uppermost, ash layers dated to between 1460 and 3360 cal BP. This long and well‐dated chronostratigraphic sequence enabled temporal trends in the abundant small mammal remains to be examined.The fossil assemblage consists of at least 31 taxa of mammals which change in proportions through time. Despite clear evidence that the Old Ancestors repeatedly carried vegetation into the cave to fuel cool fires (no visible vegetation grows in Cloggs Cave), we observed little to no evidence of cooking fires or calcined bone, suggesting that people had little involvement with the accumulation of the faunal remains. Small mammal bones were most likely deposited in the cave by large disc‐faced owls,Tyto novaehollandae(Masked Owl) orTyto tenebricosa(Sooty Owl).Despite being well dated and largely undisturbed, the Cloggs Cave assemblage does not appear to track known Late Quaternary environmental change. Instead, the complex geomorphology of the area fostered a vegetation mosaic that supported mammals with divergent habitat preferences. The faunal deposit suggests a local ancestral landscape characterised by a resilient mosaic of habitats that persisted over thousands of years, signalling that the Old Ancestors burned landscape fires to encourage and manage patches of different vegetation types and ages within and through periods of climate change.Read the freePlain Language Summaryfor this article on the Journal blog.

A multi-proxy record of environmental change through the last 53,000 years recorded in the sediments of Lake Kanono, Northland, New Zealand

ABSTRACTLake sediment archives from Southern Hemisphere mid-latitude regions provide invaluable records of late Quaternary environmental change. Here, changes in depositional environment over the past ca. 53,000 years were reconstructed using a range of physical, sedimentological, geochemical, and μ-XRF elemental proxy datasets analyzed from lake sediment cores obtained from Lake Kanono, Northland, New Zealand. The Lake Kanono stratigraphy displays a terrestrial peat environment (ca. 53,700–6,670 cal yr BP), followed by a trend of increased influx of detrital sediment during the Late Glacial–Interglacial Transition (LGIT) at ca. 14,000 cal yr BP with a peak from ca. 12,000 to 9,000 cal yr BP driven by increasingly dry conditions. The increase in sediment influx continued during the early to mid-Holocene, leading to dune reactivation which altered the catchment dynamics of the region, leading to the inception of a shallow lake basin at ca. 6,670 cal yr BP. The timing of the formation of this lake basin can be associated with changes in intensity of the Southern Westerly Winds (SWW) and the appearance and increase in intensity of the El Niño Southern Oscillation (ENSO) after ca. 7,500–7,000 cal yr BP (Moy et al. 2002; Moreno et al. 2018). Drier conditions peaked from ca. 4,000 to 2,400 cal yr BP, possibly culminating in decreased lake levels that persisted from ca. 2,400 to 2,210 cal yr BP, renewed dune accumulation, and blocked stream outlets, resulting in a deep lake basin with thermal stratification that persisted to the present. Cluster analysis of the μ-XRF data demonstrates that the most prominent change in chemistry is near the onset of the Last Glacial Maximum (LGM) at ca. 26,700 cal yr BP associated with a transition to a drier, windier climate. The second most prominent change in the μ-XRF data is during the Polynesian phase of human settlement at ca. 612–575 cal yr BP (1338– 1375 CE). Hence, we can demonstrate the utility and power of a multi-proxy approach coupled with μ-XRF element data to interpret changing sediment sources to a lake basin. Such an approach allows rapid and reliable evaluation of catchment processes influenced by climate events and land-use changes at a resolution not available using other approaches.

Late Quaternary environmental changes of Lake Urmia basin (NW Iran) inferred from sedimentological and magnetic records

The ongoing changes affecting Lake Urmia (NW Iran) are revealed by the lake water level decrease (~7 m in the last 20 yr) that was attributed to natural and anthropogenic causes but the exact impact of these factors on the state of the lake is still not identified. Indeed, lack of detailed record of environmental evolution of the lake in the past limits the understanding of actual and future processes. Our project aims to obtain a high-temporal resolution record of environmental changes in the lake area for the last ~30 kyrs. Sediment cores have been obtained from the recently dried out part of the lake near Urmia City, and surface and ground waters have been measured for electric conductivity. This paper presents results of water and sediments analyses. Six 14C AMS dating on organic fractions provide a chronological framework and indicate that the record covers the last ~30 cal kyr BP. During this period, evaporitic conditions were prevailing in the lake. The electric conductivity of brines from the sediment highlights changes in the lake water salinity. The data indicate a lake-level low stand at ~30 cal kyr BP that was followed by a water level rise and establishment of lacustrine conditions for the next ~9 kyr, this phase representing the highest lake level recorded since that time to date. From the LGM, the lake experienced several fluctuations of the water level. The relatively long-term lacustrine condition established during the Early Holocene before the water level decrease between ~5.5 and 4.9 cal kyr BP. Sediments from the two dry events at ~30 cal kyr BP and at 5.5–4.9 cal kyr BP are characterized by the presence of greigite, which indicates anaerobic early diagenetic conditions in the sediment.

The time-dependent evolutionary rate of mitochondrial DNA in small mammals inferred from biogeographic calibration points with reference to the late Quaternary environmental changes in the Japanese archipelago

The time-dependent evolutionary rate of mitochondrial DNA in small mammals inferred from biogeographic calibration points with reference to the late Quaternary environmental changes in the Japanese archipelago

Bird populations and species lost to Late Quaternary environmental change and human impact in the Bahamas

Comparing distributional information derived from fossils with the modern distribution of species, we summarize the changing bird communities of the Bahamian Archipelago across deep ecological time. While our entire dataset consists of 7,600+ identified fossils from 32 sites on 15 islands (recording 137 species of resident and migratory birds), we focus on the landbirds from four islands with the best fossil records, three from the Late Pleistocene (∼25 to 10 ka [1,000 y ago]) and one from the Holocene (∼10 to 0 ka). The Late Pleistocene sites feature 51 resident species that have lost one or more Bahamian populations; 29 of these species do not occur in any of the younger Holocene sites (or in the Bahamas today). Of these 29 species, 17 have their closest affinities to species now or formerly living in Cuba and/or North America. A set of 27 species of landbirds, most of them extant somewhere today, was more widespread in the Bahamas in the prehistoric Holocene (∼10 to 0.5 ka) than they are today; 16 of these 27 species were recorded as Pleistocene fossils as well. No single site adequately captures the entire landbird fauna of the combined focal islands. Information from all sites is required to assess changes in Bahamian biodiversity (including endemism) since the Late Pleistocene. The Bahamian islands are smaller, flatter, lower, and more biotically depauperate than the Greater Antilles, resulting in more vulnerable bird communities.

Sedimentary and foraminiferal records of Late Quaternary environmental change west of Ireland and implications for the last British–Irish Ice Sheet

ABSTRACTPalaeoenvironmental change following deglaciation of the last British–Irish Ice Sheet on the continental shelf west of Ireland was investigated using multiproxy analyses of sediment and foraminifera data from nine sediment cores. Lithofacies associations record various depositional regimes across the shelf, which evolve from subglacial to postglacial conditions. Census data provide the first characterisation of benthic foraminifera populations across the continental shelf and multivariate analyses reveal three distinct biotopes. Biomineralization within these biotopes is restricted to ≤21 200 cal a bp by four radiocarbon ages. The transition from glacial to postglacial benthic foraminifera populations near the shelf break marks the establishment of productive, nutrient‐rich, ice‐distal conditions at ~20 900 cal a bp; these conditions may also mark the start of favourable conditions for postglacial cold‐water coral growth. Postglacial conditions on the inner shelf were not established until <14 500 cal a bp, suggesting glacial conditions west of Ireland may have persisted into the Bølling–Allerød Interstadial.

Dating of a late Quaternary loess section from the northern slope of the Tianshan Mountains (Xinjiang, China) and its paleoenvironmental significance

Late Quaternary loess deposits from the Tianshan Mountains are potentially valuable archives for the study of environmental change. However, the reported chronologies of the loess deposits in this area are still controversial. Previous studies have shown that there remain discrepancies between the optically stimulated luminescence (OSL) ages and accelerator mass spectrometry (AMS) 14C ages of the loess deposits from the Yili Valley. To establish a robust chronological sequence of the Shichengzi section (SCZ17) from the northern slope of the Tianshan Mountains in Xinjiang, we adopted both AMS14C and quartz OSL dating methods and the dates-based chronology was further refined by correlating sedimentary proxies (loss-on-ignition and grain size) with the proxy information from other sequences. Comparison of the AMS 14C and quartz OSL ages suggests that the AMS 14C ages of bulk organic matter are generally younger than the quartz OSL ages, with the maximum age discrepancy reaching up to ~10 ka. Regional correlation of the Holocene lithology of the SCZ17 section with other Holocene lithologies from the Tianshan Mountains reveals that the Holocene paleosol formation occurred in the late Holocene. The analyzed proxy data (e.g., grain size, carbonate content) indicate a cold and dry climate from 21.6 to ~10 ka, and a persistent wetting trend during the past ~10 ka. This study provided interesting and new evidence of late Quaternary environmental changes in arid central Asia.

Late Quaternary environmental change record in biomarker lipid compositions of Lake Ebinur sediments, Northwestern China

Late Quaternary paleoclimate records from arid regions help us understand the response of ecological systems to natural climate change to place recent changes in a longer-term perspective. In this research, a biogeochemical analysis of a sediment core from Lake Ebinur, Xinjiang, allowed us to infer the climate and environmental changes in the late Quaternary in arid northwestern China. The combined lipid biomarkers and bulk biogeochemical properties (TOC, δ13Corg) revealed moderately wet conditions from 34 to 28 ka, favoring the growth of terrestrial vegetation. The subsequent period from 28 to 13 ka was dominated by aquatic plants, algae and microbes, indicating cold and dry conditions. Ameliorated regional moisture conditions were deduced from the higher carbon preference index (CPI) and from δ13Corg values from 13 to 3.6 ka. The optimum climate conditions occurred from 9 to 5 ka. Several climatic events also exist in the Lake Ebinur records with a wide distribution into other regions. Our biogeochemical-based paleoclimate and paleoenvironmental reconstruction is generally synchronous with sedimentary records from mid-latitude Eurasia and the NGRIP ice core record, which probably has a certain linkage with the 45°N summer insolation. We propose that summer insolation conditions in the northern hemisphere might have an impact on the climate and environmental changes in arid northwestern China in the late Quaternary.

Analysis of late Quaternary linear dune development in the Thar Desert, India

Linear dunes are the most widespread dune type worldwide and act as important geoproxies of late Quaternary environmental change in deserts. They are less common in the Thar Desert, India than other dune types, especially parabolic forms, and to date their development history is poorly understood. Here we investigate a linear dunefield in the northern Thar through analysis of a series of excavated full dune profile sites and the application of optically stimulated luminescence (OSL) dating to provide chronometric control. Results show that linear dunes have been present since at least ~58 ka and were active throughout much of the Holocene. The early Holocene, a period marked by strong Indian summer monsoon winds (e.g., Gill et al., 2017), has been shown as the last major phase of dune accumulation recorded in all sites, with ages ranging from ~11.6–8.6 ka. Two spatially restricted records of dune accumulation have also been identified during the later part of Holocene: ~4–3 ka and ~2–1 ka, attributed to localised reworking within the dunes. The suite of luminescence ages generated from the study region confirms the principle recognised in other dunefields (e.g., the south-western Kalahari; Stone and Thomas, 2008) and theoretically (Bailey and Thomas, 2014) that age records from individual dunes are unlikely to capture the developmental history of dunefields.

Guidelines for reporting and archiving 210Pb sediment chronologies to improve fidelity and extend data lifecycle

Abstract Radiometric dating methods are essential for developing geochronologies to study Late Quaternary environmental change and 210Pb dating is commonly used to produce age-depth models from recent (within 150 years) sediments and other geoarchives. The past two centuries are marked by rapid environmental socio-ecological changes frequently attributed to anthropogenic land-use activities, modified biogeochemical cycles, and climate change. Consequently, historical reconstructions over this recent time interval have high societal value because analyses of these datasets provide understanding of the consequences of environmental modifications, critical ecosystem thresholds, and to define desirable ranges of variation for management, restoration, and conservation. For this information to be used more broadly, for example to support land management decisions or to contribute data to regional analyses of ecosystem change, authors must report all of the useful age-depth model information. However, at present there are no guidelines for researchers on what information should be reported to ensure 210Pb data are fully disclosed, reproducible, and reusable; leading to a plethora of reporting styles, including inadequate reporting that reduces potential reusability and shortening the data lifecycle. For example, 64% of the publications in a literature review of 210Pb dated geoarchives did not include any presentation of age uncertainty estimates in modeled calendar ages used in age-depth models. Insufficient reporting of methods and results used in 210Pb dating geoarchives severely hampers reproducibility and data reusability, especially in analyses that make use of databased palaeoenvironmental data. Reproducibility of data is fundamental to further analyses of the number of palaeoenvironmental data and the spatial coverage of published geoarchives sites. We suggest, and justify, a set of minimum reporting guidelines for metadata and data reporting for 210Pb dates, including an IEDA (Interdisciplinary Earth Data Alliance), LiPD (Linked Paleo Data) and generic format data presentation templates, to contribute to improvements in data archiving standards and to facilitate the data requirements of researchers analyzing datasets of several palaeoenvironmental study sites. We analyse practices of methods, results and first order interpretation of 210Pb data and make recommendations to authors on effective data reporting and archiving to maximize the value of datasets. We provide empirical evidence from publications and practitioners to support our suggested reporting guidelines. These guidelines increase the scientific value of 210Pb by expanding its relevance in the data lifecycle. Improving quality and fidelity of environmental datasets broadens interdisciplinary use, lengthens the potential lifecycle of data products, and achieves requirements applicable for evidenced-based policy support.

Sponge spicule and phytolith evidence for Late Quaternary environmental changes in the tropical Pantanal wetlands of western Brazil

The environmental history of the central Pantanal wetlands of western Brazil is inferred for the last 19 kyrs based on a multi-indicator paleolimnological analysis of a sediment core from Lake Negra. The core, dated by 14C and OSL, shows variations in the abundance, diversity, and preservation of sponge spicules and phytoliths through time, consistent with changing aquatic environments. In the late Pleistocene, Lake Negra was influenced by a strong monsoon and fluvial depositional processes, whereas in the Holocene, there was a drier interval where the lake was more isolated on the floodplain. Hiatuses in the stratigraphy resulted from both wet and dry conditions, through fluvial channel scour or subaerial exposure of the lake floor, respectively. Data suggest that floodplain lakes in the Pantanal wetlands and similar riverine wetlands respond in a complex and, at times, indirect manner to climate change, and the dynamics of the adjacent fluvial system must be accounted for when interpreting paleohydrology and vegetation patterns.

낙동강 삼각주 퇴적체 중부 지역에서 채취한 시추퇴적물 시료를 이용한 신생대 제4기 후기 퇴적환경 변화 연구

낙동강 삼각주 퇴적체의 중부 지역에서 회수한 시추코어(OW-1) 퇴적물의 퇴적조직 및 퇴적구조 관찰, 입도분석, 유기지화학 분석, 색지수 측정, 연대측정 및 규조 분석을 실시하여 제4기 후기 동안의 낙동강 하구지역 퇴적환경 변화를 연구하였다. 시추퇴적층은 일곱 개의 퇴적단위로 분류되는데, 하부로부터 퇴적단위 A, B, C, D, E, F, G이고, OSL과 AMS 연대 측정 결과에 의하면 시추코어는 지난 플라이스토세 최후기 인 약 13,000년 전부터 현재까지 퇴적되었다. 퇴적단위 A (11-13 ka)는 해침이 일어나기 전 육성 환경에서 형성된 하도 퇴적층으로 모래 입자표면에 국부적으로 산화된 흔적이 관찰된다. 퇴적단위 B (9.8-11 ka)는 하위 A층에 비해 세립한 입도를 보이며 퇴적물의 색에 의해 구분이 가능하고, 해양 기원의 패각도 산출된다. 따라서 연구지역은 퇴적단위 B의 형성시기부터 해침에 의해 해양환경으로 전이되었다고 해석된다. 퇴적단위 C (8-9.8 ka)의 퇴적시기엔 해수면이 본격적으로 상승을 하면서 퇴적작용도 활발하게 진행된 하천 하구 환경으로 전이된 것으로 보인다. 퇴적단위 D (6-8 ka)는 TN, TC, TOC 값들이 높고 C/N ratio가 낮은 것으로 보아 해침이 좀 더 진행되어 해수의 영향이 최대에 이른 시기를 지시한다. 코어 상부의 퇴적단위 E와 F, G는 해수면이 현재 상태에 도달한 후, 약 5,000년 전부터 낙동강 삼각주의 전진 퇴적에 의해 형성된 것으로 해석된다.

Compound-specific isotope records of late-quaternary environmental change in southeastern North Carolina

Reconstructions of late Quaternary paleohydrology are rare from the U.S. Atlantic coastal plain (ACP). Here we present compound-specific hydrogen (δ2Halkane) and carbon (δ13Calkane) isotope analyses of terrestrially-derived n-alkanes from Jones Lake and Singletary Lake in eastern North Carolina spanning the last ∼50,000 years. Combined with pollen, charcoal, and bulk geochemical analyses, the δ2Halkane data indicate arid conditions during the late-Pleistocene, but differing edaphic conditions at the sites perhaps related to differing water table depths. The δ13Calkane data indicate a significant C4 plant component during the late Pleistocene, but other proxies indicate a sparsely-vegetated landscape. The Pleistocene-Holocene transition is marked by rapid fluctuations in δ2Halkane values that are similar to the patterns of Bølling Allerød and Younger Dryas isotope data from Greenland indicating sensitivity of the regional climate to short-lived, high-amplitude climatic events. The δ2Halkane data indicate a mesic early Holocene that supported colonization by Quercus-dominated ecosystems. Evidence of middle Holocene aridity in eastern Tennessee and western North Carolina contrasts with evidence of mesic conditions on the ACP, a geographic pattern similar to modern teleconnected precipitation responses to the Pacific Decadal Oscillation. A transition to Pinus-dominated ecosystems ∼5500 cal yr B.P. is accompanied by a large increase charcoal, but is not coincident with any large changes in δ2Halkane values, indicating that hydrologic change was likely not responsible for sustained late-Holocene dominance of Pinus. The lack of a change in middle Holocene hydrology and the spatiotemporally heterogeneous nature of the Quercus-Pinus transition on the ACP indicate prehistoric anthropogenic land management practices may represent the most parsimonious explanation for the regionally pervasive ecological change.

Late Quaternary environmental change in Oujiang delta along the northeastern Zhe-Min Uplift zone (Southeast China)

We present a history of late Quaternary coastal evolution based on the study of a 41.9-m-long sediment core from the Oujiang Delta. Multiple analytical methods are employed, including sedimentary facies analysis, radiocarbon dating, and the investigations of grain size, elemental, microfossil and pollen compositions. Two transgression-regression sequences, separated by a paleosol layer, are identified. Several lines of evidence indicate that the lower sequence was deposited during the mid-early MIS 3 stage, under a relatively warm and wet climate. An elevated MIS 3 highstand sea level (higher than −24m) is observed. The upper sequence was created after the paleosol was flooded during a marine transgression at ~9.5calkyr BP. Seven weak East Asian Summer Monsoon (EASM) events are identified with central years of ~8.4, 7.7, 6.3, 5.7, 4.7, 2.8 and 1.8calkyr BP. These coincide with those from the ECS sediment cores and the Dongge Cave δ18O record, indicating that EASM precipitation is a major controlling factor of sedimentation rates in the region. The Oujiang Delta is also subject to typhoon impacts and East Asian winter monsoon (EAWM)-induced coastal currents. Active typhoons and a relatively enhanced EAWM occurred during the weak EASM period between 4.9 and 6.4calkyr BP, producing high sedimentation rates in the middle Holocene. We emphasize the high sensitivity of small Asian river deltas as archives of the EASM, EAWM and typhoons. Such environments merit further as a means to understand past changes as well as future responses to projected climatic and sea-level change.

Preliminary study of the rodent assemblages of Goda Buticha: New insights on Late Quaternary environmental and cultural changes in southeastern Ethiopia

Given its proximity to the Strait of Bab el Mandeb and the Red Sea, the Horn of Africa is particularly important for understanding human and faunal migration events to and from Africa. Towards the end of the Pleistocene, the Middle/Later Stone Age (MSA/LSA) transition represents a critical step in human cultural evolution. However, in the Horn of Africa, the environmental conditions associated with this transition remain poorly understood. The Goda Buticha (Buticha cave) sequence, located in southeastern Ethiopia, and dated from ca. 63 ka cal BP to ca. 1 ka cal BP, provides a rare opportunity to examine the environmental contexts associated with major cultural sequences documented in the region during this time period. A preliminary analysis of the rich microvertebrate (and especially rodent) remains recovered from the levels dated between 43 and 4 ka BP identified fourteen different rodent genera, including two species that are locally extinct in southeastern Ethiopia today. While the taphonomic signature is similar throughout the sequence, indicating an in situ accumulation by an owl without major perturbation, the palaeoecological analysis showed environmental change through time, characterized by open-dry setting during the Late Pleistocene, shifting to wetter and more wooded conditions heading to the Holocene. These results are generally consistent with other diverse records which include the large mammals, speleothems and lake basins records, and allow a better understanding of the dynamics of environmental contexts associated with observed cultural change and continuity in eastern Africa from the Late Pleistocene to Late Holocene.

Long-term environmental change in eastern Tasmania: Vegetation, climate and fire at Stoney Lagoon

Tasmania’s dry, inland east is ideally positioned to inform models of late Quaternary environmental change in southern Australasia. Despite this, it remains poorly represented in the palaeoecological record. Here, we seek to address this with a >13,000-year vegetation and fire history from Stoney Lagoon, a site at the eastern margin of Tasmania’s inland Midlands plains. Pollen and charcoal analysis indicates that here, a relatively moist early deglacial was followed by a dry later deglacial (ca. 14,000–12,000 cal. BP), when sclerophyll forests became well established and burning increased. This suggests that the Midlands’ vegetation responded to the climatic signals characterising Australia’s south-eastern coast rather than those governing developments in western Tasmania. Dry sclerophyll forest persisted throughout the Holocene; with a pronounced transition from more to less grassy understoreys between ca. 9000 and 7000 cal. BP. From the mid-Holocene, the sclerophyll community remains relatively stable. However, increased fire activity and trends in moisture-sensitive taxa suggest generally drier conditions coupled with greater hydroclimatic variability under the strengthening influence of the El Niño–Southern Oscillation (ENSO). Overall, these results highlight the role of macro-scale climatic shifts in shaping vegetation development in Tasmania’s inland east, while hinting at the concurrent importance of local ecological drivers. This highlights the need for spatially diverse studies to understand interactions between drivers of long-term environmental change in sub-humid southern Australia. This research also supports conservation by strengthening understandings of pre-colonial baselines in this highly modified landscape.

Late Quaternary palaeolimnology and environmental change in the South Wollo Highlands

Lake Hayq is a closed, freshwater basin on the eastern margin of the north-central highlands, Ethiopia. Using a sediment core extracted from the northern basin, this thesis aims to provide a high-resolution, detailed palaeolimnological reconstruction of changes to the environment and climate in the region since the late Pleistocene. A multi-proxy approach was applied, utilising diatoms, photosynthetic pigments and X-ray fluorescence (XRF) spectrometry. Lithological and chronological analyses were also performed, as well as the development of a transfer function to model diatom-inferred conductivity, and other quantitative analyses. Between ~ 15.6 15.1 cal kyr BP, Lake Hayq experienced a lowstand, synchronous with the timing of Heinrich Event 1 and an intense drought across East Africa. At ~ 15.1 cal kyr BP a lake began to develop at the core site in response to wetter, more humid conditions, most likely caused by the reactivation of the African-Indian monsoonal circulation. This was abruptly ended however at ~ 14.7 cal kyr BP, as the climate shifted back towards aridity and Lake Hayq shallowed, in contrast to the majority of other East African lakes, which continued to refill. This most likely reflects changes to the Indian Ocean monsoon system caused by variability in the Atlantic Meridional Overturning Circulation at this time, in conjunction with site-specific mechanisms affecting the delivery of precipitation to Lake Hayq. At ~ 12.3 cal kyr BP the African Humid Period resumed over Lake Hayq and the lake refilled, reaching maximum water depth between ~ 12.0 10.0 cal kyr BP. The lake was dominated by planktonic diatom taxa and photosynthetic pigments indicate it was meromictic. Lake level gradually declined throughout the Holocene, culminating in the termination of the African Humid Period. A high-resolution study of the period tentatively suggests that climate flickering , in the form of oscillations between dominant diatom taxa, occurred in the build up to the major climatic shift. The termination spanned ~ 600 cal years between ~ 5.2 4.6 cal kyr BP. A lowstand occurred between ~ 3.9 2.2 cal kyr BP, during which the lake became occasionally subsaline. In the late Holocene, ~ 2.2 1.3 cal kyr BP, Lake Hayq became deep and fresh again, although there is evidence of lake level variability. The palaeo-record from Lake Hayq indicates that it broadly experienced the same high-latitude, glacial-interglacial dynamics and sub-millennial shifts in climate found in other palaeolimnological records from across East Africa. The precise timing and expression of these climatic events is not always synchronous between Lake Hayq and other East African waterbodies however, most likely caused by local, site-specific positive feedback mechanisms and variability in lake morphometry. This highlights the heterogeneous pattern of climate across the region and the significance of regional drivers. This palaeo-record, spanning the late Quaternary, will help bridge gaps in current knowledge and understanding of the underrepresented, climatically sensitive and vulnerable north Ethiopian highlands. This is vital for future climate change modelling and regional downscaling, and may also inform ethnographic-archaeological research in a region considered to be the cradle of humankind .

Late Quaternary environmental change in the Southern Cape, South Africa, from stable carbon and oxygen isotopes in faunal tooth enamel from Boomplaas Cave

ABSTRACTPleistocene palaeoclimates and palaeoenvironments of southernmost Africa are important for understanding southern hemisphere climate dynamics and for reconstructing human evolution and early human settlement in this region. Measurements of δ13C in tooth enamel of 136 faunal specimens from the archaeological site of Boomplaas Cave, South Africa, show significant shifts in proportions of C3 and C4 vegetation from the earliest deposits, probably dating to Marine Isotope Stage (MIS) 5, to the late Holocene. Vegetation communities during the Last Glacial Maximum were strongly C3‐dominated, indicating an eastward expansion of the winter rainfall zone at this time. This is consistent with climate models postulating northwards shift and/or intensification of the circumpolar westerly frontal systems during glacials. Winter rainfall and lower temperatures, both of which favour C3 grasses, were clearly more important than lower pCO2 (which favours C4 grasses) in determining the nature of the vegetation. The intervals 40–36 and 17–14k cal a BP supported substantial quantities of C4 grasses, indicating a greater proportion of summer rainfall at these times. These two intervals correspond with warmer climates as reflected in Antarctic ice cores. δ13C of an as yet unnamed caprine indicate that these animals were primarily C3 grazers.

Exploring the use of sand ramps as novel archives of Late Quaternary environmental change in Southern Africa

Exploring the use of sand ramps as novel archives of Late Quaternary environmental change in Southern Africa

Late Quaternary climate change shapes island biodiversity.

Island biogeographical models consider islands either as geologically static with biodiversity resulting from ecologically neutral immigration-extinction dynamics, or as geologically dynamic with biodiversity resulting from immigration-speciation-extinction dynamics influenced by changes in island characteristics over millions of years. Present climate and spatial arrangement of islands, however, are rather exceptional compared to most of the Late Quaternary, which is characterized by recurrent cooler and drier glacial periods. These climatic oscillations over short geological timescales strongly affected sea levels and caused massive changes in island area, isolation and connectivity, orders of magnitude faster than the geological processes of island formation, subsidence and erosion considered in island theory. Consequences of these oscillations for present biodiversity remain unassessed. Here we analyse the effects of present and Last Glacial Maximum (LGM) island area, isolation, elevation and climate on key components of angiosperm diversity on islands worldwide. We find that post-LGM changes in island characteristics, especially in area, have left a strong imprint on present diversity of endemic species. Specifically, the number and proportion of endemic species today is significantly higher on islands that were larger during the LGM. Native species richness, in turn, is mostly determined by present island characteristics. We conclude that an appreciation of Late Quaternary environmental change is essential to understand patterns of island endemism and its underlying evolutionary dynamics.