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Altres ajuts: acords transformatius de la UAB Unidad de excelencia María de Maeztu CEX2019-000940-M The use of resinous substances, certainly one of the earliest technologies developed by humans, was well-known by Holocene hunter-gatherers at the onset of the Neolithisation process across Europe. Recent research has revealed the use of birch bark tar in the central Mediterranean far from this taxon's endemic regions both in the Paleolithic and Neolithic periods and shows that the first farmers from the Fertile Crescent hafted lithic tools and waterproofed artefacts using bitumen. The generalised absence of these natural products in south-western Europe may have thus forced a reformulation of Early Neolithic technologies by exploring and benefitting from existing knowledge in local European hunter-gatherer societies. However, information on resin use from the western Mediterranean is still scarce. Here, we report on the analysis of organic residues from 168 pottery sherds by gas chromatography and gas chromatography-mass spectrometry from 10 archaeological sites in this region dating from the second half of the VIth millennium to the first half of the Vth millennium cal BC. In a limited number of samples, minor amounts of several diterpenoids diagnostic of aged Pinaceae resins were detected as mixtures with fats. The presence of pine in the palynological and carpological record supports the human exploitation of this taxon, but its minimal incidence in the anthracological record suggests that other species were selected as fuelwood. This supports the hypothesis that Pinaceae resins were used in association with pottery sporadically but ubiquitously either as its contents, or as post-firing treatments to waterproof the vessels. This demonstrates the development of adhesive technologies and resin-involved labour processes specific to Early Neolithic societies.

Altres ajuts: acords transformatius de la UAB Unidad de excelencia María de Maeztu CEX2019-000940-M Urban green installations are extensively promoted to increase sustainable and accessible food production and simultaneously improve the environmental performance and liveability of city buildings. In addition to the multiple benefits of plant retrofitting, these installations may lead to a consistent increase in biogenic volatile organic compounds (BVOCs) in the urban environment, especially indoors. Accordingly, health concerns could limit the implementation of building-integrated agriculture. In a building-integrated rooftop greenhouse (i-RTG), throughout the whole hydroponic cycle, green bean emissions were dynamically collected in a static enclosure. Four representative BVOCs, α-pinene (monoterpene), β-caryophyllene (sesquiterpene), linalool (oxygenated monoterpene) and cis-3-hexenol (LOX derivate), were investigated in the samples collected from two equivalent sections of a static enclosure, one empty and one occupied by the i-RTG plants, to estimate the volatile emission factor (EF). Throughout the season, extremely variable BVOC levels between 0.04 and 5.36 ppb were found with occasional but not significant (P > 0.05) variations between the two sections. The highest emission rates were observed during plant vegetative development, with EFs equivalent to 78.97, 75.85 and 51.34 ng g−1 h−1 for cis-3-hexenol, α-pinene, and linalool, respectively; at plant maturity, all volatiles were either close to the LLOQ (lowest limit of quantitation) or not detected. Consistent with previous studies significant relationships (r ≥ 0.92; P < 0.05) were individuated within volatiles and temperature and relative humidity of the sections. However, correlations were all negative and were mainly attributed to the relevant effect of the enclosure on the final sampling conditions. Overall, levels found were at least 15 folds lower than the given Risk and LCI values of the EU-LCI protocol for indoor environments, suggesting low BVOC exposure in the i-RTG. Statistical outcomes demonstrated the applicability of the static enclosure technique for fast BVOC emissions survey inside green retrofitted spaces. However, providing high sampling performance over entire BVOCs collection is recommended to reduce sampling error and incorrect estimation of the emissions.

Altres ajuts: acords transformatius de la UAB Unidad de excelencia María de Maeztu CEX2019-000940-M The analysis of trace quantities of monosaccharide anhydrides (MAs) in sediments is complicated by the lack of fast and reliable technologies to selectively extract these water-soluble non-ionic compounds from samples of complex composition. Here we describe a solid phase extraction method that takes advantage of the affinity between monosaccharide anhydrides (MAs) and immobilized Na+ ions related to ligand-exchange processes (LE-SPE). The capacity factor of LE-SPE columns was enhanced by using non-aqueous mobile phases such as DCM/MeOH mixtures. We have used the unique properties of LE-SPE columns to selectively extract MAs from lacustrine, coastal, and deep-sea oceanic sediment samples. The analytical procedure produces extracts with low ion suppression effects (0-20%), resulting in ideal conditions for MAs quantification with LC-ESI-MS/MS systems irrespective of the sedimentary matrix and MAs concentration. The analytical method yields repeatable concentration values (RSD of 9-23% for levoglucosan and 15-34% for mannosan and galactosan) and an IS recovery of 45-70%. The instrumental dynamic range is 10-10000 pg injected, but in practice, the methodological lower limit of quantification is constrained by sample contamination during processing. The combination of LE-SPE and LC-ESI-MS/MS has the potential to produce sensitive and reliable technologies to analyze saccharides and amino acids in environmental and biological samples.

The widespread historical and ongoing abandonment of agricultural lands worldwide presents important opportunities for promoting climate change mitigation through carbon sequestration. The default management outcome of abandonment is natural regeneration through ecological succession. However, several different management strategies and new land uses for abandoned agricultural lands have been recommended by the scientific community in recent years. This paper reviews the foremost proposed strategies and compares their soil carbon sequestration potentials. Six major categories have been proposed globally. Each proposal has positive and negative outcomes depending on site-specific factors and management objectives. Accordingly, no single strategy is ideal in all scenarios and a combination of strategies addresses multiple rural development goals concurrently. A combination of passive and active management techniques is the most effective approach for maximizing soil carbon sequestration over large geographic scales, while other strategies can be designed to also promote low-carbon land use practices and fossil fuel substitution. The implications of each proposal highlighted here demonstrates the positive role that abandoned agricultural lands can serve in climate change mitigation efforts, supporting policymakers tasked with planning the future of regions undergoing abandonment.

Altres ajuts: acords transformatius de la UAB Unidad de excelencia María de Maeztu CEX2019-000940-M Bitumen from north-eastern Mesopotamian seeps was exchanged across the Tigris and the Euphrates in antiquity. Nonetheless, recent research proposed a decline in its trade during the Bronze Age alongside the boost of central Mesopotamian (Hit) seeps trade. This paper presents new provenance studies from ancient bitumen recovered at Tell Lashkir, a 4th-2nd millennium BC settlement between the lower and upper Zab Tigris tributaries. The novel application of Bayesian mixing models to biomarker and isotopic data has narrowed down the identification of the bitumen putative sources and improved the apportionment of mixtures. This placed Tell Lashkir within the pathway of bitumen active trade routes in the Bronze Age. Thus, the population inhabiting Tell Lashkir participated in exchange networks which reached southern Mesopotamia, and traded with natural resources most probably originating from central and north-eastern Mesopotamia. From a methodological standpoint, the appraisal of the Bayesian mixing models in our study with modern and archaeological reference samples has provided a better understanding of the strengths and limitations of such an approach to apportion bitumen sources from several Bronze age territories. © 2022 The Authors Bitumen from north-eastern Mesopotamian seeps was exchanged across the Tigris and the Euphrates in antiquity. Nonetheless, recent research proposed a decline in its trade during the Bronze Age alongside the boost of central Mesopotamian (Hit) seeps trade. This paper presents new provenance studies from ancient bitumen recovered at Tell Lashkir, a 4th-2nd millennium BC settlement between the lower and upper Zab Tigris tributaries. The novel application of Bayesian mixing models to biomarker and isotopic data has narrowed down the identification of the bitumen putative sources and improved the apportionment of mixtures. This placed Tell Lashkir within the pathway of bitumen active trade routes in the Bronze Age. Thus, the population inhabiting Tell Lashkir participated in exchange networks which reached southern Mesopotamia, and traded with natural resources most probably originating from central and north-eastern Mesopotamia. From a methodological standpoint, the appraisal of the Bayesian mixing models in our study with modern and archaeological reference samples has provided a better understanding of the strengths and limitations of such an approach to apportion bitumen sources from several Bronze age territories.

Lead levels and isotopic fingerprints in 315 free-ranging animals belonging to 18 wild game species in four remote areas of the Peruvian Amazon provide a comprehensive picture of anthropogenic lead pollution in tropical rainforests. The high average concentration of lead (0.49 mg kg−1 wet weight) in livers from Amazonian wild game is comparable to the levels of lead in industrialized countries and mining areas. Although hunting ammunition is probably the main source of lead in wildlife, oil-related pollution is also a major source of contaminant lead in areas in which oil is extracted. Owing to the extended use of lead shot in subsistence hunting worldwide and the ever-encroaching oil-extraction industry in tropical rainforests, these results uncover important health risks to tropical wildlife and local communities that rely on subsistence hunting. The Amazon exemplifies conflicts between extractive resource use and conservation goals. This study finds lead in livers of Amazonian game comparable to levels in industrialized nations and that lead ammunition and oil-related pollution are key sources.

Archaeological potsherds have become a valuable source of information about diet and economic practices of past societies. We have studied the organic residues in prehistoric pottery from the Neolithic rock shelter of La Cueva de El Toro (Malaga, Spain) that was continuously occupied from the second quarter of the sixth millennium to the second millennium cal BC. The site of Cueva de El Toro is remarkable because it contains evidence that its inhabitants possessed a high technological level and complex subsistence practices based on the exploitation of livestock and agriculture. By applying gas chromatographic-mass spectrometry (GC-MS) and isotopic analysis (GC-IRMS), the goal was to determine the nature and origin of preserved lipids, and thereby provide new insights into food preparation and pottery function. Detection of fatty acids and traces of diterpene compounds originating from plants suggested a consumption of meat, dairy products and plants, as well as the pine resin utilisation. Furthermore, this work allows extending the data on faunal management and exploitation in Cueva de El Toro.

The is a mounting evidence that global emissions of dust were significantly higher during glacial than interglacial periods of the Pleistocene, and probably the Pliocene epochs. this pattern is observed in records from the low and mid latitudes, albeit with a varying degree of amplitude. During these time periods spanning 4 million years, the Earth climate underwent major transitions, such as the initiation of the Northern Hemisphere Glaciations and the Mid Pleistocene Transition. In parallel, dust transport and deposition on the oceans might have underwent stepwise increases, mainly during glacials. However, it is not clear yet if such changes are representative of global or regional climate response. Thus, dust records in marine sediments reflect changes in the different processes that drive the emission, transport, and deposition of dust on the oceans. In here, we report a compilation of marine dust records spanning the Pliocene-Pleistocene from all the major ocean basins. The synthesis of dust records on a global scale allows the identification of common patterns of variability and drivers. We analyse the data to infer changes in the global atmospheric circulation on orbital time scale, and to assess its meridional and zonal response during major climate transitions since the Pliocene.

We have developed and applied new analytical methodologies to study the drivers of the spatial distribution of pyrogenic biomarkers throughout the Iberian Peninsula. The goal of the study is to develop a multiproxy pyrogenic biomarker approach to quantitatively reconstruct the paleo-occurrence and extension of biomass wildfires from sediments. For this purpose, we have compiled an extensive collection of lacustrine sediments throughout Spain. The sample suite is representative of a wide range of climates and ecosystems. We have quantified the abundance of different types of pyrogenic biomarkers such as BPCAs (benzene polycarboxylic acids derived from the chemical oxydation of pyrogenic carbon), MAS (monosaccharide anhydrides, namely levoglucosan) and PAHs (polyaromatic hydrocarbons namely with 4 or more rings). The data obtained, as concentrations or ratios, has been mapped and compared to the documented occurrence and extension of wildfires in Spain over the last 5 decades. Specifically, we have calculated the burned area within different radius around the lake, and correlated them against the biomarker data. The regional distribution of fires in Spain is the primary driver of the spatial distribution of pyrogenic biomarkers in lakes sediments. Thus, the sedimentary concentration of pyrogenic biomarkers, generally, correlates with the area of burned forest land within a radius of 10-20km. Work is still under way to decipher the meaning between the correlations of different types of pyrogenic biomarkers, and the relation between biomarker ratios and fire regimes and vegetation types. Our study shows that pyrogenic biomarkers in lakes can be used as paleoproxies to study regional fires, as opposed to those occurring at larger spatial scales. It remains to be seen, how our findings from Spanish lakes can be extrapolated to other continental regions. Nonetheless, our study validates their use to quantify the area of forest burned in the region surrounding the lake, in addition to the frequency of fires in the past.

Differences in pottery technology and style between the Cardial and Epicardial periods have been used to study the social dynamics behind the spread of agriculture and pastoralism in the northwestern Mediterranean. This paper presents new data regarding pottery use from Early Neolithic settlements in the Barcelona plain in the sixth and fifth millennia cal BC. The recovery of organic residues from a set of 74 ceramic sherds provides the opportunity to detect changes in pottery use. The exclusive presence of non-ruminant adipose products in Cardial vessels and the sole identification of dairy products in Late Epicardial vessels are accompanied by the detection of high temperature biomarkers only in the latter period. These results suggest that, at least on a local scale, the two pottery types may have been used differently in activities transforming terrestrial animal products.

The combined application of the MBT (degree of methylation) and CBT (degree of cyclization) indices, based on the distribution of branched glycerol dialkyl glycerol tetraethers (brGDGTs) in soils, has been proposed as a paleoproxy to estimate mean annual temperature (MAT). CBT quantifies the degree of cyclization of brGDGTs and relates to soil pH. MBT and the simplified version MBT' quantify the degree of methylation of brGDGTs and relate to MAT and soil pH. However, other factors such as soil water availability have also been suggested to influence MBT' and possibly restrict the combined application of the MBT' and CBT indices as a paleotemperature proxy. To assess the effect of hydrological conditions on MBT' and CBT, a set of 23 Iberian Peninsula soil samples, covering a MAT range from 10 to 18 °C and a mean annual precipitation (MAP) range of 405 mm to 1455 mm, was analyzed. We found that the CBT was indeed significantly correlated with soil pH in our sample set. In contrast, MBT' was not correlated with MAT but had a significant correlation with the aridity index (AI), a parameter related to water availability in soils. The AI can explain 50% of the variation of the MBT', and 70% of the residuals of MAT estimated with the MBT/CBT proxy as compared to instrumentally measured MAT. We propose that, in arid settings, where water may be an ecologically limiting factor, MBT' is influenced by hydrological conditions rather than temperature. Thus, our results suggest that the combination of MBT' and CBT indices should be applied with caution in paleotemperature reconstructions in soils from dry subhumid to hyperarid environments.

Summary Benzene polycarboxylic acids (BPCAs) have been used as molecular markers to quantify and characterize pyrogenic carbon (PyC) in complex samples. The existing analytical procedures to generate and quantify BPCAs are time-consuming and cannot be used to analyse a large number of samples. Here, we present an optimized methodology to quantify BPCAs in marine and lacustrine samples. It involves a multi-step procedure that includes the oxidation of the aromatic structures of the PyC to generate the BPCAs using a microwave-assisted acid digestion, reducing oxidation time 4 times over the conventional methodology. Interfering cations (Fe) were removed with a cation exchange resin using 40% methanol as a solvent elution. The sensitivity and selectivity of the analysis was greatly improved by using HILIC chromatography coupled to tandem mass spectrometry using an electrospray interface. The sensibility and reproducibility of this method was evaluated using the method of standard addition of individual BPCAs compounds in marine samples. In addition, we have appraised our methodological approach and the use of BPCAs as proxies of wildfire occurrence and magnitude using set surface sediments from Spanish lakes and wildfire database spanning 5 decades.

The occurrence of ice-free conditions in the Nordic seas during the Last Glacial Maximum has been demonstrated using microfossil and biomarker approaches. An accurate picture of the prevailing oceanographic conditions may be more difficult to ascertain. Thus, uncertainties for most proxies increase at the cold extreme of temperature calibrations and glacial sediments contain small amounts of microfossils and biomarkers. Here we discuss sea surface temperature estimates derived from alkenone indices for the Last Glacial Maximum in the Nordic seas that provide a surprising scenario, where surface temperatures were warmer than at present. We conclude that the UK37′ and UK37 estimates may not be interpreted in terms of sea surface temperature as several factors may have conspired to bias the molecular signal. However, using an alternative index based on the abundance of the C37∶4 alkenone, we estimate a maximum temperature of 6°C.

Summary Organic biomarkers have proven their value as tools, among others, to reconstruct past environmental conditions, understand human impacts in the environment, and trace the transport pathways of the carbon cycle in sedimentary basins. For this reason, a wide variety of biomarkers (e.g. n-alkanes, C37 alkenones, GDGTs, polyaromatic hydrocarbons, n-alcohols and sterols) are routinely investigated and applied in the environmental and Earth sciences. However, current methodologies for the simultaneous analysis of an ensemble of compounds are labour intensive and time-consuming, which hamper the analysis of a large number of samples quickly and reliably. Here, we present a modified analytical approach from standard techniques to quantify organic biomarkers in marine and lacustrine sediments and atmospheric aerosols. We use a Dionex™ ASE™ 350 device to perform extraction and fractionation in one single analytical step. This significantly reduces the time of the analysis, and increases reproducibility while also diminishing sample handling time. This new approach provides faster and more reproducible quantification of a wide range of organic biomarkers in different types of environmental matrices, which significantly increases the efficiency of the analysis and allows the study of a large number of samples inexpensively while reducing solvent waste and handling time.

Unidad de excelencia María de Maeztu MdM-2015-0552 Biochar is a high carbon material resulting from biomass pyrolysis that, when applied to croplands, can increase soil carbon and soil water retention. Both effects are of critical importance in semi-arid regions, where carbon decline and desertification are the main drivers of soil degradation. Since most environmental services provided by soil are mediated by belowground biota, effects of biochar on soil microbial and invertebrate communities must be evaluated under field conditions before its agricultural application can be recommended. We tested maize biochar for its mid-term effect on soil microbes and micro-arthropods of a Mediterranean vineyard. We applied biochar to three field plots with neutral sandy loam soils at a dose of 5 Mg ha−1. During two years, we monitored the abundance of functional groups of soil micro-arthropods and estimated the biomass of soil microbial groups. We also analyzed the δ13C value of microbial PLFA biomarkers to determine biochar-C utilization by each microbial group taking advantage of the δ13C natural abundance differences between the applied biochar and the soil. Biochar addition significantly reduced soil microbial biomass but did not alter the functional microbial diversity nor the abundance or biodiversity of soil micro-arthropods. The contribution of biochar-C to the diet of most microbial groups was very low through the monitoring period. However, two gram-negative bacterial groups increased their biochar-derived carbon uptake under extreme soil dryness, which suggests that biochar-C might help soil microbes to overcome the food shortage caused by drought. The decrease in microbial biomass observed in our experiment and the concomitant decrease of SOM mineralization could contribute to the carbon sequestration potential of Mediterranean soils after biochar addition.

To appraise the application of isoprenoid glycerol dialkyl glycerol tetraethers (isoGDGTs) as paleoclimate proxies in small lakes we investigated the effect of seasonal variability in temperature and dissolved oxygen concentration (DO) on the GDGT contents and its proxy in the water column of an oligotrophic karst lake in the Catalan pre-Pyrenees (Lake Montcortes). From October 2013 to November 2014, we collected suspended particulate matter (SPM) monthly at three depths and retrieved the sediment from a trap located at 20 m below the lake surface. The GDGT contents in the SPM and sediment trap presented a marked seasonal variation, showing the highest values in summer and autumn. In addition, the isoGDGT proxy TEX86 in SPM and sediment trap showed a marked seasonal variability which matched the temperatures of the upper water column and fit the published global trend between TEX86 and mean annual lake surface temperature (LST). However, in the hypolimnion where oxygen was depleted for most of the study period, we found that TEX86 co-varied with DO. This further confirms previous claims with seasonal field data that the sedimentary TEX86 LST signal may be confounded by DO conditions. Consequently, the application of TEX86 to estimate LST should be carefully appraised in environments with depleted DO conditions., This work was supported by the Spanish Ministry of Research through projects TETRACLIM (ref. CGL2010-15000), Montcortes-500 (ref. CGL-2012-33665); and ICTA-UAB's Maria de Maeztu award (MDM-2015-0552); and a pre-doctoral research studentship to MCT (FPI, BES2013-065846). MC was funded with a doctoral research studentship from the China Scholarship Council (CSC). Fieldwork was performed with the collaboration of E. Safont, N. Canellas and J. Goma. BES2013-065846Fieldwork permits were provided by the Territorial Service of the department of Agriculture, Livestock, Fishing and Natural Environment of Catalunya. Meteorological data in Pobla de Segur were provided by J. Sigro. We also thank N. Moraleda, C. Huguet and the UAB Analytical Service for technical support.

Regional cycles of agricultural land expansion and abandonment have been common throughout history in many countries of the world. Following the cessation of agricultural practice, landscapes under...

Este artículo contiene 23 páginas, 10 figuras., In Quaternary paleosciences, the rationale behind analogical inference presupposes that former processes can be explained by causes operating now, although their intensity and rates can vary through time. In this paper we synthesised the results of di erent modern analogue studies performed in a varved lake. We discuss their potential value to obtain best results from high resolution past records. Di erent biogeochemical contemporary processes revealed seasonality and year-to-year variability, e.g., calcite precipitation, lake oxygenation, production and deposition of pollen and phytoplankton growth. Fingerprints of the first two of these processes were clearly evidenced in the varve-sublayers and allow understanding related to past events. Pollen studies suggested the possibility of identifying and characterizing seasonal layers even in the absence of varves. Marker pigments in the water column were tightly associated with phytoplankton groups living today; most of them were identified in the sediment record as well. We observed that 50% of these marker pigments were destroyed between deposition and permanent burying. In another study, seasonality in the production/distribution of branched glycerol dialkyl glycerol tetraethers (brGDGTs) and derived temperature estimates were investigated in catchment soils and particles settling in the lake. The signatures of brGDGTs in depositional environments mainly were representative of stable conditions of soils in the catchment that last over decades; no brGDGTs seemed to be produced within the lake. The main contribution of this review is to show the advantages and limitations of a multiproxy modern-analogue approach in Lake Montcortès as a case study and proposing new working hypotheses for future research., Research funding was granted by the Spanish Ministry of Economy and Competitivity (MINECO/FEDER) with the projects MONT-500, ref. CGL2012-33665; GLOBALKARST, ref. CGL2009-08145), the Institute of Catalan Studies with the projects PIRIMOD and POLMONT, and the Catalan University and Research Management Agency (AGAUR) with the projects 2014 SGR 1207, 2017 SGR 1116).

The southeast Atlantic Ocean is dominated by two major oceanic systems: the Benguela Upwelling System, one of the world's most productive coastal upwelling cells and the Agulhas Leakage, which is important for transferring warm salty water from the Indian Ocean to the Atlantic Ocean. Here, we present a multi-proxy record of marine sediments from ODP Site 1087. We reconstruct sea surface temperatures (U37 K′ and TEX86 indices), marine primary productivity (total chlorin and alkenone mass accumulation rates), and terrestrial inputs derived from southern Africa (Ti/Al and Ca/Ti via XRF scanning) to understand the evolution of the Southeast Atlantic Ocean since the late Pliocene. In the late Pliocene and early Pleistocene, ODP Site 1087 was situated within the Benguela Upwelling System, which was displaced southwards relative to present. We recognize a series of events in the proxy records at 3.3, 3.0, 2.2, 1.5, 0.9 and 0.6 Ma, which are interpreted to reflect a combination of changes in the location of major global wind and oceanic systems and local variations in the strength and/or position of the winds, which influence nutrient availability. Although there is a temporary SST cooling observed around the initiation of Northern Hemisphere glaciation (iNHG), proxy records from ODP Site 1087 show no clear climatic transition around 2.7 Ma but instead most of the changes occur before this time. This observation is significant because it has been previously suggested that there should be a change in the location and/or strength of upwelling associated with this climate transition. Rather, the main shifts at ODP Site 1087 occur at ca. 0.9 Ma and 0.6 Ma, associated with the early mid-Pleistocene transition (EMPT), with a clear loss of the previous upwelling-dominated regime. This observation raises the possibility that reorganisation of southeast Atlantic Ocean circulation towards modern conditions was tightly linked to the EMPT, but not to earlier climate transitions.

Videos recorded with infrared camera traps placed in petroleum contaminated areas of the Peruvian Amazon have shown that four wildlife species, the most important for indigenous peoples’ diet (lowland tapir, paca, red-brocket deer and collared peccary), consume oil-contaminated soils and water. Further research is needed to clarify whether Amazonian wildlife's geophagy can be a route of exposure to petrogenic contamination for populations living in the vicinity of oil extraction areas and relying on subsistence hunting.

International audience; Residue analysis in pottery usually concerns habitat or funerary sites. In this work, we have studied 21 vases from the Mines of Gavà (Barcelona, Spain) which constitute the oldest evidence of mining focused on variscite during the IV th millennium BC. The main objectives are determining the degree of preservation of lipids in this context, identifying the natural substances exploited in the vessels and highlighting pottery use in the day-today mining work at this site, as well as establishing if some of the vessels are part of the grave goods from burials in the same mines. The results obtained by combining molecular and isotopic analyses showed that more than 70 % of the containers investigated provided significant amounts of lipids. A wide diversity of organic substances processed comprising animal adipose fats, plants and beeswax was determined. Relationships found between the shape of the vessels and their content highlighted their role in the mining life. This work not only exposes one of the oldest evidences of the use of beeswax in pottery in the Iberian Peninsula, but also allows us to understand the management of resources in a very specialized archaeological site focused on mining activities.

The present study deals with a specific type of cylindrical pestle identified among several thousands of macro-lithic tools studied so far for the Argaric Bronze Age (2200–1550 cal BCE) in the southeast of the Iberian Peninsula. The combination of petrographic, technological, use-wear and residue analyses has allowed us to show that these tools were used to process beeswax and animal fatty products, probably for subsistence purposes. Apart from providing an easily recognizable archaeological tracer of apiculture, these results also complete our understanding of the economic organization of El Argar. Diachronic and spatial data reveal honey and meat productions as important energy alternatives in times of nutritional scarcity within a subsistence strategy based primarily on barley monoculture. Additionally, we show that there was socially differentiated access to both, honey and meat.

The socio-economic relevance of domesticated animals during the Early Neolithic in the Iberian Peninsula is indisputable, yet we essentially know little about the way they were managed. Among domesticated animals, pig (Sus domesticus) was a common food source and previous studies have shown the potential of stable isotopes for assessing variability in pig diet in relation to husbandry practices. Nevertheless, this approach has never been applied to the earliest pigs in the Iberian Peninsula. We analyzed the carbon and nitrogen stable isotope composition of pig bone collagen from several Early Neolithic sites in the NE Iberian Peninsula. While pig δ13C values were similar across different populations, there were significant differences in δ15N values between sites. These are attributed to different pig husbandry systems, which may reflect distinct social and spatial organization and interaction with environmental conditions during the Early Neolithic in this region.

Archaeal tetraether membrane lipids span the whole membrane width and present two C40 isoprenoid chains bound by two glycerol groups (or one glycerol and calditol). These lipids confer stability and maintain the membrane fluidity in mesophile to extremophile environments, making them very attractive for biotechnological applications. The isoprenoid lipid composition in archaeal membranes varies with temperature, which has placed these lipids in the focus of paleo-climatological studies for over a decade. Non-hydroxylated isoprenoid archaeal lipids are typically used as paleo-thermometry proxies, but recently identified hydroxylated (OH) derivatives have also been proposed as temperature proxies. The relative abundance of hydroxylated lipids increases at lower temperatures, but the physiological function of the OH moiety remains unknown. Here we present molecular dynamics simulations of membranes formed by the acyclic glycerol-dialkyl-glycerol-tetraether caldarchaeol (GDGT-0), the most widespread archaeal core lipid, and its mono-hydroxylated variant (OH-GDGT-0) to better understand the physico-chemical properties conferred to the membrane by this additional moiety. The molecular dynamics simulations indicate that the additional OH group forms hydrogen bonds mainly with the sugar moieties of neighbouring lipids and with water molecules, effectively increasing the size of the polar headgroups. The hydroxylation also introduces local disorder that propagates along the entire alkyl chains, resulting in a slightly more fluid membrane. These changes would help to maintain trans-membrane transport in cold environments, explaining why the relative abundance of hydroxylated Archaea lipids increases at lower temperatures. The in silico approach aids to understand the underlying physiological mechanisms behind the hydroxylated lipid based paleo-thermometer recently proposed.

In the Quaternary paleosciences, the rationale behind analogical inference presupposes that former natural changes can be explained by causes operating now, although their intensity and rates can vary through time. In this paper we synthesise synthetize the results of different modern analog studies and discuss their value to obtain the best inferences from high resolution past records. This synthesis is based on the following: 1) The monthly monitoring of calcite precipitation reveals a strong connection with primary producers and between-years variability; this precipitation produces a seasonal signal with imprint on varve formation. 2) Clear pollen sedimentation peaks occur in spring/summer and fall/winter that coincide with temperature, precipitation, relative humidity and winds; this pattern converges with the two-layer coupled varves representing the same seasonality. 3) We assess the lake’s contemporary oxygenation dynamics over a three- year period; a combination of sedimentary REDOX proxies revealed different scenarios of oxic/anoxic shifts since 1500 CE. 4) We investigate presence of seasonality in the production/distribution of glycerol dialkyl glycerol tetraethers and derived temperature estimates in soils and particulate matter. Branched glycerol dialkyl glycerol tetraethers signatures and some derived temperature estimates proxies appear to mainly depend on the non-seasonal shifts in soil properties. 5) Currently we examine relationships and similarities between extant phytoplankton and derived pigments in water and traps, and their correspondence with subfossil pigments; some preliminary results are presented here.Keywords: high resolution, endogenic varves, calcite precipitation, pollen sedimentation, meromixis, freshwater glycerol dialkyl tetraether, subfossil pigments, long-term ecology.

Unidad de excelencia María de Maeztu MdM-2015-0552 The increasing influence of Atlantic Water (AW) in the Barents Sea, a process known as "Atlantification", is gradually decreasing sea ice cover in the region. Ongoing global climate warming is likely to be one of its drivers, but to further understand the role of natural variability and the biogeochemical impacts of the inflow of AW into the western Barents Sea, we reconstructed sea surface temperatures (SSTs) and primary productivity in Storfjordrenna, a climatically sensitive area south of Spitsbergen, between approximately 13,950 cal yr BP and 1300 cal yr BP. The alkenone U proxy has been applied to reconstruct SSTs, and the alkenone accumulation rate in marine sediments has been used to infer changes in primary productivity. Our data show that the SST increase was concomitant with the progressive loss of sea ice cover and an increase in primary productivity in the western Barents Sea. We interpret these changes as reflecting the increasing influence of AW in the area as the ice sheets retreated in Svalbard. The transition from the Arctic to the Atlantic domain first occurred after 11,500 cal yr BP, as the Arctic Front moved eastward of the study site but with considerable variability in surface ocean conditions. High SSTs at approximately 6400 cal yr BP may have led to limited winter surface cooling, likely inhibiting convective mixing and the return of nutrients to the euphotic zone and/or enhanced organic matter consumption by zooplankton due to an earlier light signal in the ice-free Storfjordrenna. During the late Holocene (3600-1300 cal yr BP), low insolation facilitated sea ice formation and thus brine production. The former may have launched convective water mixing and increased nutrient resupply to the sea surface, consequently enhancing primary productivity in Storfjordrenna. We propose that, on the basis of the paleoceanographic evidence, the modern increasing inflow of warm AW and the disappearance of pack ice on the Eurasian continental shelf are likely to weaken convective water mixing and decrease primary production in the region.

Secondary succession on abandoned agricultural lands can produce climate change mitigation co-benefits, such as soil carbon sequestration. However, the accumulation of soil organic carbon (SOC) in Mediterranean regions has been difficult to predict and is subject to multiple environmental and land management factors. Gains, losses, and no significant changes have all been reported. Here we compile chronosequence data (n = 113) from published studies and new field sites to assess the response of SOC to agricultural land abandonment in peninsular Spain. We found an overall SOC accumulation rate of +2.3% yr−1 post-abandonment. SOC dynamics are highly variable and context-dependent. Minimal change occurs on abandoned cereal croplands compared to abandoned woody croplands (+4% yr−1). Accumulation is most prevalent within a Goldilocks climatic window of ~13–17 °C and ~450–900 mm precipitation, promoting >100% gains after three decades. Our secondary forest field sites accrued 40.8 Mg C ha−1 (+172%) following abandonment and displayed greater SOC and N depth heterogeneity than natural forests demonstrating the long-lasting impact of agriculture. Although changes in regional climate and crop types abandoned will impact future carbon sequestration, abandonment remains a low-cost, long-term natural climate solution best incorporated in tandem with other multipurpose sustainable land management strategies.

Collective assessment of marine and terrigenous organic biomarkers was performed on a sediment core spanning the last 34,800 years on the upper slope southeast of Brazil to verify the signatures of climatic variations in sea surface temperature (SST), marine productivity, and the flux of terrigenous material in this region. This evaluation is based on marine and terrigenous proxies including alkenones, chlorins, aliphatic hydrocarbons, n-alcohols, and fatty acids. This first report of organic biomarker data for this region confirms a correlation between SST, changes in terrigenous organic matter flow into the ocean, and marine productivity over the last 34.8 ka as a response to the displacement of the Brazil Current. Conditions prevailing during marine isotopic stage (MIS) 3 may be considered intermediate between the last glacial maximum (LGM) and the Late Holocene. For MIS 2, a period of low relative sea level, it was verified that the lowest SSTs were associated with the LGM and higher marine productivity. SST increased by up to 4.4 °C between the LGM and the Holocene. This reveals synchronicity between SST on the southeastern Brazilian upper slope and the North Atlantic Ocean SST records reported in earlier studies.

The distributions of branched glycerol dialkyl glycerol tetraethers (brGDGTs) in sediments are used as a proxy measurement to infer changes in past mean annual air temperatures (MAT). When applied to high resolution sedimentary sequences, measurement of brGDGT distributions is employed to reconstruct MAT at subdecadal time scales. In addition, brGDGT proxy estimates are also sometimes purported to be seasonally biased in environments where annual brGDGT production may not be constant during a seasonal cycle. The main aim of this study was to assess the occurrence of seasonality in the production and distribution of brGDGTs and the seasonality bias of the derived temperature proxy. For this purpose, we examined brGDGT distributions and brGDGT-derived MAT estimates in surface soils and settling/suspended particulate matter over one year, from two sites located in the same latitude but at different altitudes, in the Catalan Pyrenees, as well as at one site in southern Norway. These locations have marked seasonal temperature cycles, which were expected to maximize the possibility of detecting any seasonal bias in the production and compositions of brGDGTs. The results show that brGDGT abundance is heterogeneous and increases with soil humidity. The brGDGT distributions and some of the brGDGT-derived proxy measurements in soils are relatively stable throughout the year and do not change significantly in the suspended particulate matter in the river or settling particulate matter in traps. Our study shows that the impact of the seasonality of temperature on brGDGT distribution was absent in the soils studied, regardless of altitude or latitude on a catchment/regional scale. As soils are likely to contain a brGDGT signature which is representative of average environmental conditions in the catchment at least over decades, brGDGT proxy reconstructions derived from soil sources are more suitable to infer variability in environmental parameters over the same timescales (i.e. decades or longer). On shorter timescales (i.e. annual), sediment downcore variability in brGDGTs is likely to be related to changes derived from in situ production and sediment sources.

The Late Pliocene has been proposed as a possible analogue for understanding future climate change and for testing climate models. Previous work has shown that during the Pliocene the major upwelling systems were relatively warm, and that this meant they were either inactive, contracted, or were upwelling warmer waters than present. Here, we examine evidence from a site located on the margins of the modern Benguela Upwelling system to test whether the upwelling cells had migrated or contracted relative to present during the Pliocene. We applied several organic geochemistry proxies and foraminiferal analyses to reconstruct the Pliocene history of ODP Site 1087 (31°28′S, 15°19′E, 1374 m water depth), including the UK37′ and TEX86 indices (for reconstructing sea surface temperatures), phytoplankton biomarker concentrations and stable isotope ratios (for estimating export primary productivity, and for oxygen isotope statigraphy), and planktonic foraminifera assemblage abundances (for inferring water mass changes). These proxies show that, between 3.5 and 3.0 Ma, the southern Benguela region was cooler than the northern Benguela region by 5 °C, the latter being where the main upwelling cells are found today. From the multiproxy data obtained, we also infer that more extensive upwelling was present in the southern Benguela region during the Pliocene than at present, and that the Benguela Upwelling cells shifted northwards after the Pliocene epoch as a result of changes in the local wind field. We also find evidence that the Benguela Upwelling was sensitive to the pronounced cooling during the M2 and KM2 glacial stages, potentially associated with the expansion of sea ice and cooling in Antarctica in the Late Pliocene.

Oil has been extracted from the Northern Peruvian Amazon for over four decades. However, few scientific studies have assessed the impacts of such activities in the environment and health of indigenous communities in the region. We have investigated the occurrence of petrogenic hydrocarbon pollution in soils and sediments from areas favoured as hunting or fishing grounds by local indigenous inhabitants. The study was conducted in one of the most productive oil blocks in Peru, located in the headwaters of the Amazon river. Soils and river sediments, in the vicinity of oil extraction and processing infrastructure, contained an oil pollution signature as attested by the occurrence of hopanes and steranes. Given the lack of any other significant source of oil pollution in the region, the sources of hydrocarbons are likely to be the activities of the oil industry in the oil block, from voluntary discharges or accidental spills. Spillage of produced water was commonplace until 2009. Moreover, petrogenic compounds were absent in control samples in sites far removed from any oil infrastructure in the oil block. Our findings suggest that wildlife and indigenous populations in this region of the Amazon are exposed to the ingestion of oil polluted soils and sediments. The data obtained supports previous claims that the local spillage of oil and produced waters in the water courses in the Corrientes and Pastaza basins could have eventually reached the main water course of the Amazon.

Archaea inhabiting marine and freshwater sediments have a relevant role in organic carbon mineralization, affecting carbon fluxes at a global scale. Despite current evidences suggesting that freshwater sediments largely contribute to this process, few large-scale surveys have been addressed to uncover archaeal diversity and abundance in freshwater sedimentary habitats. In this work, we quantified and high-throughput sequenced the archaeal 16S rRNA gene from surficial sediments collected in 21 inland waterbodies across the Iberian Peninsula differing in typology and trophic status. Whereas methanogenic groups were dominant in most of the studied systems, especially in organic-rich sediments, archaea affiliated to widespread marine lineages (the Bathyarchaeota and the Thermoplasmata) were also ubiquitous and particularly abundant in euxinic sediments. In these systems, Bathyarchaeota communities were dominated by subgroups Bathyarchaeota-6 (87.95 ± 12.71%) and Bathyarchaeota-15 (8.17 ± 9.2%) whereas communities of Thermoplasmata were mainly composed of members of the order Thermoplasmatales. Our results also indicate that Archaea accounted for a minor fraction of sedimentary prokaryotes despite remarkable exceptions in reservoirs and some stratified lakes. Copy numbers of archaeal and bathyarchaeotal 16S rRNA genes were significantly different when compared according to system type (i.e., lakes, ponds, and reservoirs), but no differences were obtained when compared according to their trophic status (from oligotrophy to eutrophy). Interestingly, we obtained significant correlations between the abundance of reads (Spearman r = 0.5, p = 0.021) and OTU richness (Spearman r = 0.677, p

Unidad de excelencia María de Maeztu MdM-2015-0552 The database includes spatial, chronological and technological information about the analyzed tools in the article entitled "Evidence of bee products processing: a functional definition of a specialized type of macro-lithic tool" (Ache et al., 2017 ). The technological information refers to the tool type, its rock type, weight, state of preservation, morphology, metrical data and functional features. We also provide an index of acronyms to properly understand the dataset published here.

TEX86 (TetraEther indeX of tetraethers consisting of 86 carbon atoms) is a sea surface temperature (SST) proxy based on the distribution of archaeal isoprenoid glycerol dialkyl glycerol tetraethers (GDGTs). In this study, we appraise the applicability of TEX86 and View the MathML sourceTEX86L in subpolar and polar regions using surface sediments. We present TEX86 and View the MathML sourceTEX86L data from 160 surface sediment samples collected in the Arctic, the Southern Ocean and the North Pacific. Most of the SST estimates derived from both TEX86 and View the MathML sourceTEX86L are anomalously high in the Arctic, especially in the vicinity of Siberian river mouths and the sea ice margin, plausibly due to additional archaeal contributions linked to terrigenous input. We found unusual GDGT distributions at five sites in the North Pacific. High GDGT-0/crenarchaeol and GDGT-2/crenarchaeol ratios at these sites suggest a substantial contribution of methanogenic and/or methanotrophic archaea to the sedimentary GDGT pool here. Apart from these anomalous findings, TEX86 and View the MathML sourceTEX86L values in the surface sediments from the Southern Ocean and the North Pacific do usually vary with overlaying SSTs. In these regions, the sedimentary TEX86-SST relationship is similar to the global calibration, and the derived temperature estimates agree well with overlaying annual mean SSTs at the sites. However, there is a systematic offset between the regional View the MathML sourceTEX86L-SST relationships and the global calibration. At these sites, temperature estimates based on the global View the MathML sourceTEX86L calibration are closer to summer SSTs than annual mean SSTs. This finding suggests that in these subpolar settings a regional View the MathML sourceTEX86L calibration may be a more suitable equation for temperature reconstruction than the global calibration.

A feature of Pliocene climate is the occurrence of “permanent El Niño-like” or “El Padre” conditions in the Pacific Ocean. From the analysis of sediment cores in the modern northern Benguela upwelling, we show that the mean oceanographic state off Southwest Africa during the warm Pliocene epoch was also analogous to that of a persistent Benguela “El Niño”. At present these events occur when massive southward flows of warm and nutrient-poor waters extend along the coasts of Angola and Namibia, with dramatic effects on regional marine ecosystems and rainfall. We propose that the persistent warmth across the Pliocene in the Benguela upwelling ended synchronously with the narrowing of the Indonesian seaway, and the early intensification of the Northern Hemisphere Glaciations around 3.0–3.5 Ma. The emergence of obliquity-related cycles in the Benguela sea surface temperatures (SST) after 3 Ma highlights the development of strengthened links to high latitude orbital forcing. The subsequent evolution of the Benguela upwelling system was characterized by the progressive intensification of the meridional SST gradients, and the emergence of the 100 ky cycle, until the modern mean conditions were set at the end of the Mid Pleistocene transition, around 0.6 Ma. These findings support the notion that the interplay of changes in the depth of the global thermocline, atmospheric circulation and tectonics preconditioned the climate system for the end of the warm Pliocene epoch and the subsequent intensification of the ice ages.

A robust understanding of past oceanographic variability in the Southern Ocean is important because of its role in modulating global climate change. Here, we analyzed the distributions of isoprenoid glycerol dialkyl glycerol tetraethers (GDGTs), both non-hydroxylated and the more recently discovered hydroxylated ones, in a well studied 500 kyr sediment record (core PS2489-2) from the Atlantic sector of the Southern Ocean and reconstructed past sea surface temperature. Given the uncertainty in the GDGT temperature indices, we appraised existing calibrations by comparing them with other temperature proxies and cold-water mass indicators determined from the same core. None of the existing calibrations afforded temporal trends and/or absolute values consistent with other better constrained temperature proxies. Using an extended compilation from a global core top hydroxylated GDGT data set, we examined if the disagreement might stem from the calibration data set and the definition of the GDGT indices. Among the new GDGT indices tested, the OHC index (an extended TEX86 index modified similarly to the UK37 index) and OHL (including a log function similar to TEX86L) showed temporal variability that was the most consistent with other proxies. However, they also gave unrealistic sub-zero glacial temperature values, which may have been caused by a biased calibration due to the small calibration data set, and/or a shift in production or export depth of GDGTs during glacial stages which, in turn, result in a GDGT-temperature relationship different from that during the interglacial stages.

Oil extraction activities in the Northern Peruvian Amazon have generated a long-standing socio-environmental conflict between oil companies, governmental authorities and indigenous communities, partly derived from the discharge of produced waters containing high amounts of heavy metals and hydrocarbons. To assess the impact of produced waters discharges we conducted a meta-analysis of 2951 river water and 652 produced water chemical analyses from governmental institutions and oil companies reports, collected in four Amazonian river basins (Maranon, Tigre, Corrientes and Pastaza) and their tributaries. Produced water discharges had much higher concentrations of chloride, barium, cadmium and lead than are typically found in fresh waters, resulting in the widespread contamination of the natural water courses. A significant number of water samples had levels of cadmium, barium, hexavalent chromium and lead that did not meet Peruvian and international water standards. Our study shows that spillage of produced water in Peruvian Amazon rivers placed at risk indigenous population and wildlife during several decades. Furthermore, the impact of such activities in the headwaters of the Amazon extended well beyond the boundaries of oil concessions and national borders, which should be taken into consideration when evaluating large scale anthropogenic impacts in the Amazon.

Two commonly used proxies based on the distribution of glycerol dialkyl glycerol tetraethers (GDGTs) are the TEX86 (TetraEther indeX of 86 carbon atoms) paleothermometer for sea surface temperature reconstructions and the BIT (Branched Isoprenoid Tetraether) index for reconstructing soil organic matter input to the ocean. An initial round-robin study of two sediment extracts, in which 15 laboratories participated, showed relatively consistent TEX86 values (reproducibility +/- 3-4 degrees C when translated to temperature) but a large spread in BIT measurements (reproducibility +/- 0.41 on a scale of 0-1). Here we report results of a second round-robin study with 35 laboratories in which three sediments, one sediment extract, and two mixtures of pure, isolated GDGTs were analyzed. The results for TEX86 and BIT index showed improvement compared to the previous round-robin study. The reproducibility, indicating interlaboratory variation, of TEX86 values ranged from 1.3 to 3.0 degrees C when translated to temperature. These results are similar to those of other temperature proxies used in paleoceanography. Comparison of the results obtained from one of the three sediments showed that TEX86 and BIT indices are not significantly affected by interlaboratory differences in sediment extraction techniques. BIT values of the sediments and extracts were at the extremes of the index with values close to 0 or 1, and showed good reproducibility (ranging from 0.013 to 0.042). However, the measured BIT values for the two GDGT mixtures, with known molar ratios of crenarchaeol and branched GDGTs, had intermediate BIT values and showed poor reproducibility and a large overestimation of the true (i.e., molar-based) BIT index. The latter is likely due to, among other factors, the higher mass spectrometric response of branched GDGTs compared to crenarchaeol, which also varies among mass spectrometers. Correction for this different mass spectrometric response showed a considerable improvement in the reproducibility of BIT index measurements among laboratories, as well as a substantially improved estimation of molar-based BIT values. This suggests that standard mixtures should be used in order to obtain consistent, and molar-based, BIT values.

[1] Marine biological export productivity declined in high-latitude regions in the North Pacific and Southern Ocean 2.7 million years ago, in parallel with the intensification of Northern Hemisphere glaciation. Here we present data from the North Atlantic, which show a similar but time-transgressive pattern of high-latitude productivity decline from 3.3 to 2.5 Ma, with productivity decreasing first at 69°N, hundreds of thousands of years before it declined at 58°N. We propose that the cumulative data are best explained by an equatorward migration of the westerly winds, which caused a southward shift in the zone of Ekman divergence and upwelling-associated major nutrient supply over this time interval. We suggest that a similar equatorward migration of the westerly winds may also help explain the productivity changes observed in other high-latitude regions, particularly the Southern Ocean. At 2.7 Ma, equatorial and temperate Atlantic sites began to show orbitally paced productivity pulses, consistent with a shoaling and meridional contraction of the nutrient-poor “warm sphere” that characterizes the low latitude upper ocean. This timing coincides with observed productivity changes in Southern Ocean, consistent with previous findings that the Southern Ocean exerts a strong influence on the fertility of the low-latitude Atlantic. Finally, we propose that the unique basin geometry of the North Atlantic caused deep water formation in this region to remain relatively stable despite equatorward migration of winds and ocean fronts.

Branched glycerol dialkyl glycerol tetraethers (brGDGTs) of purportedly terrestrial origin are frequently detected in marine sediments, even in remote ocean sites where no direct impact from land erosion via rivers takes place. At these places, the most likely explanation for the presence of brGDGTs is in situ production or eolian transport, but neither possibility has been demonstrated for the open ocean. Here, we report the presence of isoprenoid (iso) and brGDGTs in eight dust samples collected off Northwest Africa. Based on previous studies, prevailing wind patterns, bulk chemistry, n-alkane composition and isotopic signatures, we show that Northwest Africa is the likely principal origin of the GDGTs in the dust. The concentrations of plant wax n-alkanes in the dust are several orders of magnitude higher than those of GDGTs and, based on the distributions of these two compound classes, we infer that they tag different carbon pools and sources of organic matter. Our finding demonstrates that brGDGTs and isoGDGTs in marine sediments and wind-derived deposits can have an eolian source. Consequently, climate reconstruction may be attempted from wind-derived deposits of brGDGTs, even in remote oceanic areas.

mid-Pleistocene climate transition (MPT) is defined by the emergence of high amplitude, quasi-100 ka glacial-interglacial cycles from a prior regime of more subtle 41 ka cycles. This change in periodicity and amplitude cannot be explained by a change in 'external' astronomical forcing. Here, we review and integrate published records of sea-surface temperatures (SSTs) to assess whether a common global expression of the MPT in the surface ocean can be recognized, and examine our findings in light of mechanisms proposed to explain climate system reorganization across the MPT. We show that glacial-interglacial variability in SSTs is superimposed upon a longer-term cooling trend in oceanographic systems spanning the low-to high-latitudes. Regional variability exists in the timing of the onset and magnitude of cooling but, in most cases, a long-term cooling trend begins or intensifies from similar to 1.2 Ma (Marine Isotope Stage, MIS, 35-34). The SST cooling accompanies a long-term trend towards higher global ice volume as recorded in benthic foraminifera delta O-18, but predates a step-like increase in delta(18)Oat similar to 0.9 Ma (MIS 24-22) that is argued to reflect expansion of continental ice-sheets. The strongest expression of Pleistocene cooling is found during glacial stages, whereas minor or negligible trends in interglacial temperatures are identified. However, pronounced cooling during both glacial and interglacial maxima is evident at 0.9 Ma. Alongside the long-term SST cooling trends, quasi-100 ka cycles begin to emerge in both the SST and delta O-18 records at 1.2 Ma, and become dominant with the expansion of the ice-sheets at 0.9 Ma. We show that the intensified glacial-stage cooling is accompanied by evolving pCO(2), abyssal ocean ventilation, atmospheric circulation and/or dust inputs to the Southern Ocean. These changes in diverse environmental parameters suggest that glacial climate boundary conditions evolved across the MPT. In turn, these modified boundary conditions may have altered climate sensitivity to orbital forcing by placing pre-existing ice-sheets closer to some threshold of climate-ice sheet response.