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[Abstract] Understanding the environmental response to the last glacial termination in regions located in transitional climate zones such as the Atlantic Iberian mountains is crucial to estimate potential changes in regions affected by current glacial melting. We present an 8.5 m-long, solid last deglaciation and Holocene chronostratigraphic record including detailed sediment analysis from Lake Peixão, a pro-glacial lake in the Serra da Estrela (Central Portugal). The age–depth model relies on a Bayesian approach that includes 16 AMS 14C dates and 210Pb–137CS measurements, robustly dating the lake formation at 14.7 ± 0.32 cal. ka BP. This chronological reconstruction shows an average sedimentation rate of ca. 0.07 cm yr−1 (15 yr cm−1), enabling proxy analyses at decadal timescales. The sediment sequence is composed of five lithological units: (U1) coarse and unsorted fluvioglacial lacustrine deposits; (U2) massive fluvioglacial lacustrine deposits (863–790 cm below surface [bsf]; 14.7 ± 0.32–13.8 ± 0.12 cal. ka BP); (U3) water current fluvioglacial lacustrine deposits (790–766 cm bsf; 13.8 ± 0.12–12.9 ± 0.29 cal. ka BP); (U4) laminated/banded lacustrine deposits characterized by terrigenous deposits from ice-covered lake periods and episodic events of ice and snow melting (766–752 cm bsf; 12.9 ± 0.29–11.7 ± 0.15 cal. ka BP); and (U5) massive muddy lacustrine deposits (752–0 cm bsf; 11.7 ± 0.15 cal. ka BP–present). The occurrence of U2 to U4 deposits defines the transition from glacial cold (U1) to net warm postglacial conditions (U5). These climate transitions are marked by changes in sediments and the presence of very low sedimentation rate periods, possibly related to the Intra-Allerød Cold Period and the coldest phase of the Younger Dryas. Our results support the previously proposed timing of the retreat of the Serra da Estrela glaciers ca. 13.8 ± 0.12 cal. ka BP. The robust chronology of Lake Peixão highlights the potential of Iberian pro-glacial lakes for datin

Heavy minerals are typically rare but important components of siliciclastic sediments and rocks. Their abundance, proportions, and variability carry valuable information on source rocks, climatic, environmental and transport conditions between source to sink, and diagenetic processes. They are important for practical purposes such as prospecting for mineral resources or the correlation and interpretation of geologic reservoirs. Despite the extensive use of heavy mineral analysis in sedimentary petrography and quite diverse methods for quantifying heavy mineral assemblages, there has never been a systematic comparison of results obtained by different methods and/or operators. This study provides the first interlaboratory test of heavy mineral analysis. Two synthetic heavy mineral samples were prepared with considerably contrasting compositions intended to resemble natural samples. The contributors were requested to provide (i) metadata describing methods, measurement conditions and experience of the operators and (ii) results tables with mineral species and grain counts. One hundred thirty analyses of the two samples were performed by 67 contributors, encompassing both classical microscopic analyses and data obtained by emerging automated techniques based on electron-beam chemical analysis or Raman spectroscopy. Because relatively low numbers of mineral counts (N) are typical for optical analyses while automated techniques allow for high N, the results vary considerably with respect to the Poisson uncertainty of the counting statistics. Therefore standard methods used in evaluation of round robin tests are not feasible. In our case the ‘true’ compositions of the test samples are not known. Three methods have been applied to determine possible reference values: (i) the initially measured weight percentages, (ii) calculation of grain percentages using estimates of grain volumes and densities, and (iii) the best-match average calculated from the most reliable analyses f

In 1755 CE, a strong earthquake followed by a transatlantic tsunami destroyed large coastal areas; it also left its sedimentary imprints in the Boca do Rio valley (western Algarve, Portugal). This tsunami layer is very well preserved and has been analysed in several studies. Deposits of preceding extreme wave events, however, have rarely been described for the entire Algarve coast. In this study, we present a multiproxy analysis of seven sediment cores from the Boca do Rio region, organized in two crossing transects, one parallel and the other perpendicular to the coastline. The geochronological framework has been established by combining radiocarbon and optically stimulated luminescence dating with sedimentological and geochemical analyses (XRF, C/N, magnetic susceptibility, granulometry, micropalaeontology), and covers the palaeogeographical evolution of that area for the last four millennia. As expected, the 1755 CE tsunami was easily identified at all coring sites, as a sandwiched stratum between fine-grained alluvium. This event layer presents several tsunami characteristics, such as erosive basal contact, rip-up clasts, a fining-upward sequence, and a mud cap. At one coring site, a second extreme wave event layer of marine origin was detected within floodplain deposits, due to its granulometric, XRF, magnetic susceptibility and micropalaeontological properties. It is stratigraphically located below the 1755 CE Lisbon tsunami layer and can be associated with another yet undocumented extreme wave event, most likely dating to the mid or late 1st millennium CE. (C) 2019 Elsevier B.V. All rights reserved.

The Tagus estuary is one of the larger estuaries of Europe (area of c.325km2). Lisbon is located in the northern margin of the estuary and despite the long diachrony of its occupation since the Palaeolithic, the city was founded during the Iron Age and grown continuously since then. The riverine front, containing archaeological evidences of occupation since the Iron Age, and clearly modified during the Roman Period, was successively enlarged at the end of the Middle Age by the construction of landfills, conquering area to the river that was used since then for the development of maritime-related activities and others. In 2014 a 7.5m-long core was collected from sediment below the landfill (-1m MSL) during the re-arrangement works of Ribeira das Naus (a Lisbon downtown riverine street built-up on a landfill constructed in the 1940¿s) in an area used as a dock - Doca da Caldeirinha - between the 18th and the 20th centuries. According to bibliography, the area was strongly affected by the 1755 earthquake and related tsunami. Several environmental proxies, combined with 14C dating, were analyzed at vertical high resolution. The sediment is essentially composed by mud (>90% of fine particles) with ca. 9% of organic matter and ca. 4% of CaCO3. ¿13C values are around -25¿, reflecting estuarine conditions. Sediments have accumulated between 2000 cal BP and 1362 cal BP, evidencing high sedimentation rates (SR) in this area during the Roman Period. SR were extrapolated using Clam 2.2 software and values of 0.9 cm yr-1 (-8.5m to -5.7m MSL; 2000 cal BP to 1600 cal BP) and 1.9-2cm yr-1 (-5.7m to -1m MSL; 1600 cal BP to 1362 cal BP) were determined. The high SR can result from both natural and anthropic causes; however, changes on the sedimentary pattern of the Tagus estuary over the last 2000 years are mainly due to human impact. The pollen record preserved in the core attests the existence of open landscape vegetation between 2000 cal BP and 1362 cal BP with the occurrence of h

[Abstract] Estuaries are sensitive to changes in global to regional sea level, to climate-driven variation in rainfall and to fluvial discharge. In this study, we use source and environmentally sensitive proxies together with radiocarbon dating to examine a 7-m-thick sedimentary record from the Sado estuary accumulated throughout the last 3.6 kyr. The lithofacies, geochemistry and diatom assemblages in the sediments accumulated between 3570 and 3240 cal. BP indicate a mixture between terrestrial and marine sources. The relative contribution of each source varied through time as sedimentation progressed in a low intertidal to high subtidal and low-energy accreting tidal flat. The sedimentation proceeded under a general pattern of drier and higher aridity conditions, punctuated by century-long changes of the rainfall regime that mirror an increase in storminess that affected SW Portugal and Europe. The sediment sequence contains evidence of two periods characterized by downstream displacement of the estuarine/freshwater transitional boundary, dated to 3570–3400 cal. BP and 3300–3240 cal. BP. These are intercalated by one episode where marine influence shifted upstream. All sedimentation episodes developed under high terrestrial sediment delivery to this transitional region, leading to exceptionally high sedimentation rates, independently of the relative expression of terrestrial/marine influences in sediment facies. Our data show that these disturbances are mainly climate-driven and related to variations in rainfall and only secondarily with regional sea-level oscillations. From 3240 cal. BP onwards, an abrupt change in sediment facies is noted, in which the silting estuarine bottom reaches mean sea level and continued accreting until present under prevailing freshwater conditions, the tidal flat changing to an alluvial plain. The environmental modification is accompanied by a pronounced change in sedimentation rate that decreased by two orders of magnitude, reflectin

As discussed in Part I, a large accumulation of mammalian faeces at the mire site in the upper Guil Valley near Mt. Viso, dated to 2168 cal 14C yr., provides the first evidence of the passage of substantial but indeterminate numbers of mammals within the time frame of the Punic invasion of Italia. Specialized organic biomarkers bound up in a highly convoluted and bioturbated bed constitute an unusual anomaly in a histosol comprised of fibric and hemist horizons that are usually expected to display horizontal bedding. The presence of deoxycholic acid and ethylcoprostanol derived from faecal matter, coupled with high relative numbers of Clostridia 16S rRNA genes, suggests a substantial accumulation of mammalian faeces at the site over 2000 years ago. The results reported here constitute the first chemical and biological evidence of the passage of large numbers of mammals, possibly indicating the route of the Hannibalic army at this time. Combined with the geological analysis reported in Part I, these data provide a background supporting the need for further historical archaeological exploration in this area.

Controversy over the alpine route that Hannibal of Carthage followed from the Rhône Basin into Italia has raged amongst classicists and ancient historians for over two millennia. The motivation for identifying the route taken by the Punic Army through the Alps lies in its potential for identifying sites of historical archaeological significance and for the resolution of one of history's most enduring quandaries. Here, we present stratigraphic, geochemical and microbiological evidence recovered from an alluvial floodplain mire located below the Col de la Traversette (~3000 m asl—above sea level) on the French/Italian border that potentially identifies the invasion route as the one originally proposed by Sir Gavin de Beer (de Beer 1974). The dated layer is termed the MAD bed (mass animal deposition) based on disrupted bedding, greatly increased organic carbon and key/specialized biological components/compounds, the latter reported in Part II of this paper. We propose that the highly abnormal churned up (bioturbated) bed was contaminated by the passage of Hannibal's animals, possibly thousands, feeding and watering at the site, during the early stage of Hannibal's invasion of Italia (218 bc).