Multi-proxy Approach Research Articles

Maastrichtian – Paleocene environmental and climatic conditions in Koum Basin (northern benue trough, Cameroon) inferred using a multiproxy approach including sedimentology, mineralogy, and geochemistry

The Koum Basin is one of major intracontinental basins in northern Cameroon. It is part of the Upper Benue Trough and has genetic ties to the West and Central African Rift System. The main purpose of studying the Koum Basin sedimentary deposits was to re-examine the time of the deposition and constrain the palaeoenvironmental and paleoclimatic conditions during deposition. To accomplish this, we used a combination of sedimentologic, palynologic, mineralogic, and geochemical data. Claystone units interbedded with calcareous siltstones dominate sedimentary sequence, including few clay beds, fine to medium-grained sandstone, and rare marl layers. The palynomorph assemblage suggests a previously unknown Maastrichtian – Paleocene age in this basin. The sediments originated from intermediate igneous parent rocks with a relative contribution of felsic rocks. These rocks underwent low detritism (Si/Al: 2.51–4.43; K/Al: 0.11–0.36; Ti/Al: 0.05–0.10) and chemical weathering (CIA: 55–64; PIA: 56–68) in the source region. Consequently, deposits are immature (ICV values > 1) and weakly recycled (Si2O3/Al2O3 ratios ≤5). The organic matter analysis and the palynoflora assemblage, reveal Type III kerogen with significant contributions of Type II-III and type II kerogens, as well as a continental paleo-depositional environment with open rainforest to savannah vegetation. The clay minerals distribution suggests moderate illitization and chloritization processes and thus moderate burial diagenesis at temperatures ranging from 70 to 90 °C, also attested by immature to mature Tmax values (≤436 °C) marginally. The low CIA values and very low kaolinite contents, indicate dry climatic conditions. In addition, two major-element-based discrimination diagrams show that the parent rocks of clastic sediments formed primarily in a continental arc system, with a moderate contribution from the rift system and a low contribution from the oceanic island arc, implying compressional conditions, which is consistent with previous studies on the tectonic background of the region during the late Maastrichtian to Paleocene period.

Discerning the sulfur geochemical features of turbidites and methane-rich sediments from the South China sea

Upward diffusion of dissolved methane and associated anaerobic oxidation of methane (AOM) coupled with microbial sulfate reduction (MSR) are widespread in normal hemipelagic sediments of continental margins. The occurrence of authigenic sulfur enrichment in such sediments is usually regarded as an indicator of AOM; however, extensive MSR and authigenic iron sulfide generation also occur in turbidites. Therefore, research attention should be directed toward determining the geochemical features of authigenic sulfur mineralization in methane-rich background sediments and turbidites. Here we report the sedimentology and geochemical composition of sediments from four piston cores (CL30, CL44, CL47, and CL3A) containing turbidite layers from methane-rich areas of the South China Sea. The turbidite layers were deposited at 17–15 kyr BP or earlier during the last glacial period and were located above the present sulfate–methane transition zone (SMTZ). The median grain size, proportion of sand-sized grains, and Si, Ti, K, and Zr contents show marked elevation in the turbidite layers compared with the background sediments, indicating the input of large amounts of terrigenous detrital matter with coarser grains. High total sulfur (TS) contents and low δ34SAIS values (AIS: acid-insoluble sulfur) (−35.2‰ to −26.1‰) are observed within turbidite layers relative to the background hemipelagic sediments in core CL44. These results suggest that intensive sulfidization occurred as a result of enhanced organoclastic sulfate reduction rates in turbidite horizons, which were probably caused by the resultant decrease in downward oxygen flux and waning bioturbation after rapid deposition of turbidites. In comparison, TS contents are higher and δ34SAIS values are positive (0.2‰–46.8‰) within the SMTZ on account of the rapid consumption of sulfate and build-up of isotopically heavier hydrogen sulfide pools via intensive AOM. Moreover, authigenic barium (Ba) enrichments commonly occur in the depth interval immediately above the SMTZ rather than within turbidite layers; therefore, they serve as a useful indicator of the position of the SMTZ. This study presents distinct differences in the geochemical compositions of turbidity deposits and methane-rich background sediments and highlights that a multi-proxy approach including sedimentological and geochemical analyses should be used to constrain the types of MSR in deep-sea sediments, given the common occurrence of turbidites and subsurface methane release in marginal deep-sea areas. It is also suggested that if applied with caution, S–C–Ba geochemical patterns can be used to identify palaeo-SMTZs and palaeo methane-rich zones in turbidite-containing strata.

Synthesis of high-Andean peat cores reveals suite of Holocene climate conditions favorable for peat formation

Peat-core records have a long history of being used for paleoclimate reconstructions in northern high-latitude regions but are less common in the southern tropical zone. In this study, we present a synthesis of published peat-core reconstructions and basal ages from high-elevation (>3000 m a.s.l.) sites in the northern and central Andes of South America. We complement this database by providing a new multi-proxy peat-core-based paleoecological reconstruction from the Alta Murmurani peatland, Cordillera Vilcanota, Peru. This record, with a peat inception age of 8980 cal. yr BP, was analyzed for plant macrofossils and stable isotopes (carbon, oxygen). This review (1) assesses the timing of peat initiation and development across the tropical high-elevation region of South America (8°N to 27°S); (2) assesses the reliability of peat-core paleoclimate reconstructions by comparing the peat-core inferences across sites and against other independent archives (e.g., lake sediments, ice cores, speleothems); and (3) determines which hydroclimatic conditions are favorable for peat formation and expansion across the study area. Our results show that peat initiation occurred throughout the Holocene, progressing from the northern Andes to central Andes, with highest initiation frequencies clustered at ca. 10,700 cal. yr BP and 8300 cal. yr BP, respectively. Our synthesis reveals that peat cores can be used to assess regional paleoclimate trends in the central Andes using a multi-proxy approach combining micro- and macrofossils such as pollen, stable isotopes, as well as organic and inorganic elemental analyses. We also identify three optimal peat-forming time periods, all with optimally wet conditions occurring at transitional hydroclimate phases: (1) following deglaciation, with warming temperatures and increased moisture related to glacial runoff (ca. 11,000 cal. yr BP and ∼8000 cal. yr BP), (2) under moderate moisture regimes related to intensifying ENSO and warmer conditions (∼3500 cal. yr BP), and (3) under conditions related to increased precipitation at the beginning of a cold period (Little Ice Age). We show that either regional climate (e.g., changes in precipitation) or local conditions (e.g., changes in glacial runoff) can promote peat formation across the study region.

Fuelling the Roman salt industry. Developing a new multiproxy approach to identify peat fuel from archaeological combustion residue

In Europe, especially the Low Countries, peat was intensively used as a fuel source. Yet, the identification of peat as a fuel source from archaeological combustion residues is challenging. Nevertheless, detecting peat fuel in archaeological contexts would significantly contribute to broader socio-economic questions, such as fuel and landscape management strategies. To achieve this goal, this study developed a new multiproxy approach by combining several analytical methods (light microscopy, scanning electron microscopy, analytical pyrolysis, phytolith, faecal spherulite and ash pseudomorphs analyses and micro X-ray fluorescence spectroscopy) to identify fuel types, predominantly peat, from combustion residues. This methodology was successfully applied to combustion residues discovered at 6 Roman salt production sites situated along the southern North Sea coast. Not only was peat, specifically Sphagnum sp. and Ericaceae peat, identified as the predominant fuel source, but the use of fossil coal as a secondary fuel source could also be hypothesised. This paper demonstrates the high potential of the proposed methodology to identify not only the use of peat in combustion residues, but potentially also the specific type of peat used as well as other fuel sources.

Transfer of industrial contaminants from the inner to the outer region of Sepetiba Bay (SE Brazil) by dredge spoil dumping activities: a temporal record

A multiproxy approach involving grain size, geophysical (resistivity, magnetic susceptibility, and P-wave velocity), mineralogical (XRD), and geochemical (elemental, stable isotopes) data has been applied to core SP9 (128 cm long) to reconstruct natural and anthropogenic changes since ≈1850 AD (anno domine) (dating by 210Pb and 127Cs methods) in a distal region of Sepetiba Bay (SB), Rio de Janeiro State (SE Brazil). The analyzed core is a fine-grained sedimentary sequence (except its upper 20 cm). It comprises detrital particles derived from felsic and intermediate source rocks, as suggested by the fields defined by the biplot Zr vs TiO2 and the Al2O3/TiO2 ratios. Despite the increase in particle size at the top of the core, there was a progressive increase in the organic matter and potentially toxic elements (PTEs) contents and nutrients such as N and P. The geophysical data allowed us to identify the presence of subsurface (biogenic) gas, which suggests the occurrence of eutrophication processes in the study area despite its location in the outer region of the bay. Core SP9 records cyclical changes over the last ≈170 years in the mineralogical and elemental composition of the sediments and type of organic matter supplied to the bottom. These changes are associated with phases of more significant oceanic influence, salinity variations in the study area, and greater or lesser oxygen depletion in the sediment. These changes may have resulted from climatic oscillations or variations in the configuration and extension of the Ponta da Pombeba spit. The extent of this structure and the anthropic activities have contributed to the contamination of this area since 1975 AD. However, statistical analyses (Pearson correlations and principal components analysis) suggest that the transport and accumulation of PTEs (mainly Cd and Zn) did not strictly follow the general pattern of sedimentary dynamics prevailing in the studied area. Results indicate that this area became strongly polluted by Cd and Zn and with high ecological risk due to dredging and spoil disposal activities at sites close to the study area. It is noted that the environmental degradation reached higher levels here than in areas close to the primary source of the metals, the disabled Ingá Mercantil Company, in Madeira Island. This work demonstrates the temporal effect of dredge disposal activities in a distal region of Sepetiba Bay for the first time. It is a strong indicator that dredged spoil areas must be selected carefully, since healthy areas can become degraded due to the dumping of polluted waste.

Palynofloristics and wildfire evidence from Permian deposits of the Satpura Gondwana Basin, India: a multiproxy approach

ABSTRACT Miofloral and fossil charcoal analyses of the Permian deposits of the Barakar and Motur formations from core PKK-2B, located in the Pench-Valley Coalfield, Satpura Basin (India) were carried out to assess the floral diversity, evidence for palaeo-wildfire and age. Two distinct palynoassemblages are identified: Faunipollenites varius palynoassemblage and Gondisporites raniganjensis palynoassemblage dated as Kungurian (Cisuralian) and Guadalupian (Wordian-Capitanian), respectively. These assemblages show dominance of pollen attributable to Glossopteridales followed by Cordaitales and Coniferales. The occurrence of charcoal at two levels in the sedimentary sequence indicates the occurrence of repeated wildfires in the surrounding area. Macroscopic charcoal fragments exhibit anatomical features such as bordered pitting, rays and helical thickenings on cell walls of tracheids suggesting a gymnospermous wood affinity. Most of the charcoal specimens exhibit rounded edges suggesting an allochthonous origin. Furthermore, fusinite reflectance (1.03–6.61%) of studied charcoal/inertinite fragments suggests that the temperature was in the range of ~305–962°C during charring. This indicates co-occurrence of high-temperature crown fires, together with medium- and low-temperature surface and ground fires, respectively. Our data emphasise the dominance of gymnospermous vegetation during the Permian in India and adds further evidence for the widespread occurrence of wildfires during this period in India and on entire Gondwana as well.

Bioproductivity and vegetation changes documented in Eifel maar lake sediments (western Germany) compared with speleothem growth indicating three warm phases during the last glacial cycle

Understanding supra-regional climate variability such as the changes in the North Atlantic realm is important to identify the drivers of the climate system. In this study maar lake sediments from the Eifel (western Germany) were analysed with a multi-proxy approach and compared to central and western European speleothem growth phases.Corg (chlorins) and the pollen assemblage were analysed from two sediment cores of the Hoher List infilled maar lake. To generate Corg (chlorins) and pollen records covering the entire last 130,000 yr b2k (years before year 2000 CE), the data from this study were stacked with published data from other Eifel maar lake sediment cores (Sirocko et al., 2013, 2021, 2022). The sediment cores from Hoher List infilled maar lake were dated by marker tephra layers giving chronological anchor points and the precise dating of the sediment cores was performed by the tuning of the Corg (chlorins) records to the NGRIP δ18O record (Rasmussen et al., 2014). The speleothems, whose growth phases are compared to the lake sediment proxy records, were compiled from the literature as well as speleothems from Dechencave (western Germany) dated by the 230Th/U-method in this study.The Corg (chlorins) variability shows the bioproductivity in the maar lake, which is related to water temperature and corresponds to the Greenland Interstadials (GIs) in the NGRIP δ18O record indicates its dependence on supra-regional climate variations in the North Atlantic. The pollen record shows three periods of forest with temperate forest species, during the Eemian, early Marine Isotope Stage (MIS) 3, and the Holocene. Speleothem growth in four caves in central and western Europe (Dechencave, Spannagel Cave, Hölloch Cave, Villars Cave) is predominantly sensitive to cold periods with glaciers and/or permafrost conditions above the caves inhibiting speleothem growth. The forested phases and phases of high bioproductivity in the Eifel correspond well with phases of speleothem growth indicating three warm phases in central Europe during the last glacial cycle.

Reconstructing 15 000 years of southern France temperatures from coupled pollen and molecular (branched glycerol dialkyl glycerol tetraether) markers (Canroute, Massif Central)

Abstract. Climatic changes in southern Europe during the Holocene are characterized by a strong spatial and temporal heterogeneity whose patterns are still poorly understood, notably the presence or not of a Holocene thermal maximum (HTM; 10 000–6000 cal BP). The climatic patterns also differ according to the proxies used (e.g. pollen, chironomid) and the latitude of the record. Here, a multi-proxy approach combining pollen and lipid biomarkers (branched glycerol dialkyl glycerol tetraethers, brGDGTs) is applied to the Canroute sedimentological sequence (Massif Central, France) to reconstruct the climatic variation over the last 15 000 years in southern Europe. This area is poorly documented in terms of vegetation and climate change. To provide reliable climate reconstructions, we have (1) performed a multi-method approach applied to pollen (modern analogue technique, MAT; weighted averaging partial least squares regression, WA-PLS; boosted regression trees, BRT; and random forest, RF) and molecular biomarkers brGDGTs (five calibrations) and (2) investigated the role of modern databases and calibrations in climate reconstructions. Three different databases were tested for pollen data: one global database based on a Eurasian pollen database and two regional databases corresponding to Mediterranean–Temperate Europe and Temperate Europe–Scandinavian databases respectively. Five global calibrations were tested for lipid biomarkers including four for soil and one for peat. Results show that the use of different modern databases highlights the importance of considering environmental and ecological constraints when using transfer functions on pollen sequences. Pollen- and brGDGT-inferred climate trends are consistent, notably for the Late Glacial and the Early and Late Holocene. However, the reconstructions notably differ concerning the presence of a Holocene thermal maximum with the MAT pollen-based method, but no difference is apparent with the BRT pollen method nor brGDGT. The temperature reconstructions estimated from the two independent pollen and lipid proxies are then compared to regional climate signals (chironomids, pollen, molecular biomarkers) to better understand global regional climatic patterns in southern Europe. Altogether, our results from the Canroute sequence and those already available in southern Europe reveal that for the Late Glacial and Early Holocene, the regional climate trends are consistent between sites and proxies, supporting the reliability of their reconstructions despite some discrepancies. During the Holocene, the temperature signal of Canroute does not indicate the clear presence of a pronounced HTM, but rather stable temperatures.

Last Glacial – Holocene variability of the European Slope Current, NE Atlantic

The upper branch of the Atlantic Meridional Overturning Circulation (AMOC) in the mid-latitudes of the Northeast Atlantic remains poorly studied. This study provides a complete overview of the glacial, deglacial and Holocene dynamics of the easternmost portion of the AMOC upper branch, namely the European Slope Current (ESC) and its glacial equivalent known as the Glacial Eastern Boundary Current (GEBC). This is achieved through the study of the sediment core SU81–44 retrieved from the southern Bay of Biscay (BoB) (∼1000 m water depth), and by using a multiproxy approach (i.e. benthic foraminiferal assemblage, grain size proxies, oxygen and carbon stable isotopes, and neodymium isotopic composition of foraminiferal shells). During the glacial period and the onset of the deglaciation, the grain size proxies at SU81–44 fluctuate significantly. These fluctuations are coherent with changes in relative densities of benthic foraminiferal indicator species of current strength and ventilation, thus highlighting significant changes in the GEBC vigor through time. The SU81–44 data confirm the Dansgaard-Oeschger interstadial/faster-stadial/slower flow pattern previously observed in northern BoB. Our results also provide new constraints on the strength of the slope current during the late deglaciation and Holocene period with a significant reinvigoration of the ESC, and by extension the upper branch of the AMOC during the Bølling-Allerød warming. This seems to confirm the crucial role of the ESC in deep water formation at high northern latitudes, as it is the case today. Finally, our data show a progressive weakening of the ESC during the Holocene. We hypothesize a link with a long-term decrease in the density gradient between low and high latitudes that can be attributed to long term changes in insolation and the strength of the subpolar gyre dynamics.

Spatial and temporal abilities of proxies used to detect pre-Columbian Indigenous human activity in Amazonian ecosystems

Humans have been modifying ecosystems since before the Holocene began ca. 12,000 years ago, even in Neotropical regions. The Amazon was once thought to be ‘pristine’ and only lightly impacted by Indigenous people before European colonization in the Americas (e.g., pre-Columbian); however, multiple lines of evidence have shown that Indigenous human activities over the past millennia have left ecological legacies on modern ecosystems. We review the various lines of evidence used to reconstruct pre-Columbian Indigenous human activity in Amazonia, and assess the spatial and temporal resolution and limits of each one of them. We suggest that a multi-proxy approach is always preferred, and that lines of evidence that cover overlapping yet discrete spatial and temporal scales can provide a robust and comprehensive assessment of the nuances of pre-Columbian Indigenous human activities in Amazonia, and how they affect modern ecosystems.

Palaeoecological reconstruction of Plio-Pleistocene herbivores from the Ahl al Oughlam site (Casablanca, Morocco): Insights from dental wear and stable isotopes

In this article, we use a multiproxy approach based on stable isotope analyses (δ18O and δ13C), mesowear, and microwear dental analysis to reconstruct the climate, diet, and habitat of Plio-Pleistocene herbivores at the site of Ahl al Oughlam in western Morocco. This study has been conducted on teeth from several taxa (Sivatherium maurusium, Hipparion pomeli, Metridiochoerus phacochoeroides, Gazella sp., Alcelaphini and Anancus osiris), enabling a robust ecological reconstruction. Our isotopic results suggest a predominance of C3 plant consumption for all analyzed species, while dental wear indicates a varied diet, with evidence for both browsing and grazing behavior being present. The combination of proxies indicates a landscape dominated by open C3 grasslands in an arid climate, as supported by the Mean Annual Precipitation (MAP) results. These findings contribute to the ongoing debate on the ecological context that facilitated the Plio-Pleistocene dispersal, occupation, and evolution of mammals and hominins in northern Africa, for which limited information is available.

In front of the retreating ice-sheet: Fauna complex of central-western Poland in MIS 3–2 (Krosinko site)

A new locality in Central Europe (Krosinko, Poland) yields a rich fossil material of great taxonomical variety. Its location in the Warsaw–Berlin ice-marginal valley, where it forms a 1-m horizon at a the depth of 6–8 m, is suited to a taphonomic analysis aimed at reconstructing the paleoevents and depositional history of the late Pleistocene (MIS 3–2).Our analysis revealed that the material accumulated as the result of high-energy fluvial transport. This transport disturbed the original bone associations, as indicated by the lack of articulation, low refitting, and bone surface modification. During water movement, the bones were polished, abraded, pitted, and fragmented. Prior to that, however, taphonomic signatures were left behind by predators, humans, and plant roots. This is the first time that unquestionable burning marks have been found on woolly rhino remains from Poland.The secondary context of the faunal assemblage was confirmed by neodymium isotope studies of the faunal fragments and sediment. Given the results of sedimentological analysis from previous studies, these sediments can be associated with a high-energy braided river. The remains were moved along with paleobotanical material and flints in a westerly direction; this is suggested by the direction of water flows in the valley and the river waters supplying it.The deposition occurred within a single geologic event around 26 ka BP, as indicated by the youngest radiocarbon date of the remains, or ca. 19 ka BP, considering the geochronological constraints for the local LGM ice margin position in central and eastern Poland ∼22–18 ka, and the specified accumulation time of the sediments in which they were found. Secondary mineralization of manganese and iron on the bones was the final taphonomical process that impacted the remains.The combined taphonomic, palaeozoological, isotopic and geological results show for the first time for a Polish paleontological site how data integration improves interpretation and highlights the advantages of a multiproxy approach.

Geochemistry and petrology of the Chandarpur-Raipur sandstones: Implications for the evolution of the Chattisgarh Basin, Central India

Depositional processes and stratigraphic evolution of the Chattisgarh basin exhibit a synergistic relation between sedimentation and tectonics. To interpret the sedimentation history and basin evolution, multiproxy approach including field studies, petrography, geochemical, and multivariate statistical analyses of the sandstones of Chandarpur and Raipur groups is employed. The study provides a detailed analysis of the time-connoted petrography and geochemistry of the sandstone units from each formation of the Chandarpur-Raipur sequence of Chattisgarh basin. The sandstones grade from immature wacke through submature arkose to mature quartzarenite from the bottom up the section. These sandstones are broadly characterized by felsic provenance, arid-humid palaeoclimate, and weak-intense palaeoweathering at the source. The assemblage of wacke-arkose-sublitharenite of the basal Lohardih Formation is characteristics of fan delta environment and represents initiation of rifting and basin formation stage. Subarkoses from the younging up sequence of Lohardih-Chaporadih-Kansapathar formations reflect prograding shelf environment that represents craton interior field of the continental block provenance and passive marginal tectonic setting, indicating gradual stabilization of the basin. Quartzarenites from Kansapathar Formation and stratigraphically younger Devsagar Member of Charmuria Formation also represent broadly similar provenance and tectonic setting indicating stable craton interior provenance in a passive marginal setting. Petrographic and geochemical analyses of some of the Kansapathar-Devsagar sandstones suggesting recycled orogen provenance, however, may be attributed to the orogenic activity and/or role of younger bimodal volcanic rock during rejuvenation of multistage basin opening faults. Rifting stage was followed by subsidence stage as indicated by the presence of black limestone capping the sandstone successions. Initiation of basin formation ∼1400 Ma and sedimentation can be correlated with the late-stage fragmentation of the supercontinent Columbia. The basin probably closed ∼1000 Ma during the assembly of the next supercontinent Rodinia. It is estimated that ∼87% of the 2.2-km-thick sedimentary succession in the eastern Chattisgarh basin, were already deposited within this time frame (∼1405 and ∼1007 Ma). The basin is correlatable with other Mesoproterozoic basins of Peninsular India like Vindhyan, Cuddapah basins, as well as with basins like Xiong’er rift basin of North China Craton, Espinhaco basin of eastern Brazil, that are related to the Columbia-Rodinia Supercontinent cycle.

Evaluating the temperature dependence of δ44/40Ca along with δ18O, Mg/Ca, and Sr/Ca in calcite tests of multiple foraminifera species

Preserved biomineral chemical compositions serve as valuable tools in constructing proxies for reconstructing past climates. A persistent effort exists to enhance and innovate temperature proxies, ensuring a comprehensive understanding of historical temperature variability—a vital Earth System parameter. Calcium isotopes (δ44/40Ca) in foraminifera have been debated to be sensitive to temperature and requires further refinement. In this study we present a comprehensive assessment of δ44/40Ca temperature sensitivity in foraminifera by utilizing concurrent δ44/40Ca, δ18O, Mg/Ca, and Sr/Ca ratios data on same samples. These coupled isotopic and elemental ratios were determined across various foraminifera species, including benthic (C. wuellerstorfi), thermocline planktic (G. truncatulinoides, G. inflata), and mixed layer planktic (G. ruber, G. bulloides, O. universa, G. siphonifera) from core-top and sediment trap samples from the Atlantic Ocean. The δ44/40Ca -T calibration included calcification temperatures derived from both δ18O and Mg/Ca, utilizing established δ18O -T and Mg/Ca-T relationships. The temperature sensitivity of δ44/40Ca in foraminifera is 0.042–0.058 ‰/°C using all species data from published work and this study (except data from <3 °C habitat temperature). We report foraminifera δ44/40Ca and temperature relationships: δ44/40Ca (‰) = 0.042 × T (°C) + 0.289 (r2 = 0.80, p < 0.0001), using temperatures derived from δ18O and Mg/Ca, respectively. Furthermore, we introduce a novel paleotemperature equation for foraminifera, employing a multi-regression approach that combines two temperature proxies, δ44/40Ca and Mg/Ca: SST (°C) = (9 ± 2.6) × δ44/40Ca + (3.28 ± 0.63) × Mg/Ca - (2.89 ± 1.09). This multi-proxy approach can mitigate the uncertainty associated with individual proxy measurements and allows cross-validation. Application of this multi-proxy relationship to an East Atlantic Site (GeoB1112) yields a glacial-interglacial temperature change of 4.2 ± 0.93 °C between MIS 1 and MIS 3 which is in agreement with published work.

Palaeoenvironmental reconstruction of Loch Duart (NW Scotland, UK) since the Last Glacial Maximum: implications from a multiproxy approach

ABSTRACTA sediment core from the salt marsh fringing Loch Duart, NW Scotland, UK, containing Lateglacial to Holocene sediments, was analysed using a multi‐element geochemical approach to elucidate the relative sea level (RSL) and palaeoenvironmental changes associated with the deglaciation of the British and Irish Ice Sheet. Elemental and isotopic measurements of rhenium, osmium, carbon and nitrogen, X‐ray fluorescence scanning, radiocarbon dating, and foraminiferal analysis produced a suite of data that complements the existing biostratigraphic framework. This suite of bio‐, litho‐ and chemostratigraphic analyses permits discussion of RSL changes that reflect the interplay between post‐glacial eustatic rise and glacio‐isostatic adjustment. The osmium‐isotope (187Os/188Os) data, coupled with a new age–depth model, depict an RSL fall between 16.8 and 14.1 ka cal bp at an average rate of 2 mm a−1. Falling RSL culminates in basin isolation and is followed by subsequent marine inundation from 11.6 ka cal bp. This RSL record preserves the local interaction between glacial isostatic adjustment and glacio‐eustatic sea‐level change, a relationship that is reflected in the sediment's 187Os/188Os signature. This is the first known application of the osmium isotope system in an isolation basin that is shown to be a viable proxy for RSL change, a technique that could be applied to glacially influenced isolation basins globally.

Population expansion and intensification from a Malthus-Boserup perspective: A multiproxy approach in Central Western Argentina

In Central Western Argentina (CWA), the incorporation of cultigens by hunter-gatherer populations has been much discussed. This paper explores the relationship between population dynamics, subsistence change, and burial patterns driven by the process of land use intensification and increasing reliance on maize. We hypothesize that territorial behavior emerged in the context of population growth and competition for resources with a high probability of failure, as expected in an arid environment. To evaluate this hypothesis, we explore four lines of inquiry in southern Mendoza (CWA): 1) the frequency of radiocarbon dates to estimate population dynamics; 2) the Juvenile Index as a fertility rate proxy; 3) the stable isotopes on human bone (δ13Cco, δ15N, δ13Cca) to reconstruct diet; and 4) burial patterns as an estimate of territorial control. Our results partially support our hypothesis: During an early stage, when maize started to appear in the diet, the population was increasing, and cemeteries emerged along with some signs of violence. The hypothesis is not supported in a second period, when maize consumption and population were highest, but large cemeteries disappeared. In light of this evidence, the effect of maize on human societies was not uniform and irrevocable, and the adoption of maize by human foragers contributed to a new and diverse set of human-environment relationships.

Inferring odontocete life history traits in dentine using a multiproxy approach (δ15 N, δ44/42 Ca and trace elements).

Understanding the interactions between marine mammals and their environment is critical for ecological and conservation purposes. Odontocetes offer a continuous record of their life history from birth as recorded in annual increments of their tooth dentine. Because dentine is not remodeled and contains collagen, nitrogen stable isotope compositions (δ15 N) reflect nursing and weaning events, life history traits that would otherwise be impossible to retrieve in such elusive marine animals. Yet, capturing the magnitude and temporal changes in these events is constrained by tooth size and sampling resolution. Moreover, historical and fossil specimens undergo collagen decay, hence the need to develop the measurements of other proxies. Here, we present a multiproxy approach to investigate the use of Ca isotope compositions (δ44/42 Ca) in relation to δ15 N and laser ablation profiles for different trace metal (Ba, Mg, Sr, Zn) concentrations across the dentine of a single individual of the common bottlenose dolphin Tursiops truncatus. To help interpret the dentine data, we provide milk elemental compositions and δ44/42 Ca values for two odontocete individuals. We discuss the observed changes in δ44/42 Ca across the dentine as potential markers of birth, weaning interval, incidental ingestion of seawater, trophic level and physiology. Incidental ingestion of seawater during nursing induces a positive offset in δ44/42 Ca values recorded in the early formed dentine. Life history parameters of individual marine mammals are extremely difficult to retrieve due to limitations in observing specimens in the wild and the methodology presented here offers new ecological and paleoecological perspectives.

Modern conditions and recent environmental evolution of the industrialized inner Ría of Ferrol (Galicia, NW Spain)

Galician rías provide several ecosystem services of great ecological and economic significance in the northwestern Iberian margin, requiring a good environmental quality for sustainable harnessing. More paleoenvironmental reconstructions extending to their preindustrial state are needed to predict their evolution under natural and human-induced perturbations, such as ongoing anthropogenic global warming. This study's aim is twofold: first, characterize the current environmental conditions governing the inner Ría of Ferrol (Galicia, NW Spain) and address its recent natural and anthropogenic evolution. Therefore, a multiproxy approach (benthic foraminifera, grain size, pollen content, trace metals, Al, total organic and inorganic carbon contents, total nitrogen content, δ13C, magnetic susceptibility, 210Pb and 137Cs radiotracers, and microplastics) has been applied to intertidal surface and sediment core samples. The benthic foraminiferal results exhibit typical inner ría assemblages, primarily driven by natural ría-estuarine dynamics, with a higher dominance of brackish species (H. germanica, A. morphogroup tepida), fewer living individuals and marine allochthonous taxa toward the continental end-member. The foraminiferal standing crops and surface trace metal concentrations do not reflect strong anthropogenic impacts, although areas with elevated magnetic susceptibility have been detected, probably associated with nearby industrial activities. The recent sedimentary deposits reveal anthropogenic impacts at local and regional scales, with different environmental shifts. Local impacts were triggered by physical interventions in the inner ría, with the construction of the As Pías Bridge in 1968 and the great urban-industrial development of Ferrol city and surrounding localities experienced since the late 19th century. Land-use changes have driven regional scale changes, corresponding to reforestation plans with the introduction of anthropogenic plant species for industrial purposes initiated in the 1940s. The stratigraphic analysis of sediment cores has unveiled high levels of contaminants (Zn and microplastics) in the innermost sector as the primary environmental concerns. In this sediment-infilling and restricted area, potential dredging activities could release them leading to their possible bioavailability. Although past adverse environmental conditions cannot be discarded, sedimentary intervals with negligible presence of microfauna in the innermost area have mostly been attributed to taphonomic processes involving calcareous dissolution and disaggregation of agglutinated tests, likely caused by carbonate-undersaturated conditions and organic matter metabolization by microbial activity respectively.

A multi-proxy framework to detect insect defoliations in tree rings: a case study on pine processionary

Assessing and reconstructing the impacts of defoliation caused by insect herbivores on tree growth, carbon budget and water use, and differentiating these impacts from other stresses and disturbances such as droughts requires multi-proxy approaches. Here we present a methodological framework to pinpoint the impacts of pine processionary moth (Thaumetopoea pityocampa), a major winter-feeding defoliator, on tree cover (remote-sensing indices), radial growth and wood features (anatomy, density, lignin/carbohydrate ratio of cell walls, δ13C and δ18O of wood cellulose) of drought-prone pine (Pinus nigra) forests in north-eastern Spain. We compared host defoliated (D) and coexisting non-defoliated (ND) pines along with non-host oaks (Quercus faginea) following a strong insect outbreak occurring in 2016 at two climatically contrasting sites (cool-wet Huesca and warm-dry Teruel). Changes in tree-ring width and wood density were analyzed and their responses to climate variables (including a drought index) were compared between D and ND trees. The Normalized Difference Infrared Index showed reductions due to the outbreak of –47.3% and –55.6% in Huesca and Teruel, respectively. The D pines showed: a strong drop in growth (–96.3% on average), a reduction in tracheid lumen diameter (–35.0%) and lower lignin/carbohydrate ratios of tracheid cell-walls. Both pines and oaks showed synchronous growth reductions during dry years. In the wet Huesca site, lower wood δ13C values and a stronger coupling between δ13C and δ18O were observed in D as compared with ND pines. In the dry Teruel site, the minimum wood density of ND pines responded more negatively to spring drought than that of D pines. We argue that multi-proxy assessments that combine several variables have the potential to improve our ability to pinpoint and reconstruct insect outbreaks using tree-ring data.

Tracking pollution from fur farms using forensic paleolimnology

Eutrophication, which remains one of the greatest threats to water quality worldwide, is particularly acute in agricultural areas. Here we assessed long-term drivers of potential pollution inputs to lakes in southwest Nova Scotia (Canada), a region marked by fur farming (mainly mink) and other agricultural activities. We used a BACI (before-after-control-impact) study design with sediment cores collected from 14 lakes selected based on their proximity to mink farms. We combined economic data, mink faecal samples, and a series of geochemical markers in dated sediment cores, including sterols, δ15N, visible reflectance spectroscopy (VRS)-inferred chlorophyll-a, and heavy metals, to relate changes in sediment geochemistry to the growth of mink farms in the region. Sterol biomarkers (cholesterol and β-sitosterol) measured in a range of samples (i.e. mink faeces and feed, aquaculture feed), were elevated where mink farms were located close to each study lake. Mink-related sterols (cholesterol, β-sitoserol), δ15N measurements, VRS chlorophyll-a, and heavy metals As, Cu, Sr increased in the 1980s coeval with a ∼400% increase of mink farms in the region, especially near Nowlans Lake. Agricultural impacts were subtler in other lakes. Our study expands on prior applications of geochemical fingerprinting in forensic paleolimnology when direct monitoring data are incomplete. This multi-proxy approach has promising applications for environmental pollution assessments in other lake ecosystems experiencing water quality issues.