Journal of Quaternary Science最新文献

Peat in the Pastaza–Marañón Foreland Basin (PMFB), northern Peru, forms beneath open wetlands, palm swamps, pole forests and seasonally flooded forests. These vegetation communities may represent different successional stages of peatlands, but the spatiotemporal patterns of peatland development in Amazonia are still poorly understood. We present a new geochemical and palaeoecological record spanning the last c. 4330 years from an open peatland (San Roque, core SAR_T3_03_B). Our results suggest the persistence of predominantly herbaceous vegetation communities at the core site since the start of peat accumulation (c. 3180 cal a bp). Micro-X-ray fluorescence core scanning provides evidence for episodes of fluvially derived minerogenic input and simultaneous increases in flood-tolerant taxa relating to intervals of increased frequency and depth of riverine flooding. The establishment of Mauritia flexuosa palms from around 440 cal a bp coincided with a shift to lower flooding depth and frequency which continues to the present day. This study reveals the role of flooding variability in shaping peatland development and influencing vegetation succession in the PMFB, underlining the need to understand natural environmental variability for the conservation of these ecosystems due to their vital contributions to ecosystem services and carbon storage.

Previous studies from the Iberian Central System and other mountains of the Iberian Peninsula and Europe suggest that deglaciation in this area occurred at the end or immediately after the global Last Glacial Maximum (LGM, 26.5–19 ka). In this research, we investigate the timing and speed of deglaciation of the palaeoglacier in La Vega gorge (Iberian Central system) since the global LGM, dating the outer moraines, glacially polished bedrock and glaciofluvial deposits by means of in situ cosmogenic ¹⁰Be and optically stimulated luminescence. The results show that one intermediate arc located at the outer frontal moraine system has an age of ~21 ka, being consistent with the global LGM. Deglaciation began at ~21–19 ka, speeding up at ~19 ka. We estimate that around 4–5 km of the palaeoglacier receded in ~1–2 kyrs since ~19 ka, leaving La Vega gorge probably ice-free at ~18 ka. Therefore, our data confirm that deglaciation in Sierra de Gredos began at the end of the global LGM, characterised by a rapid and massive retreat of glaciers.

The Holocene Storegga tsunami, 8120–8175 cal a bp, resulted in run-up heights of up to 3–6 m around mainland UK and coincided with a suggested large population decline in the coastally focused Mesolithic population in Northern Britain. At Howick, Northumberland, the site of a Mesolithic settlement, a nearby sediment deposit may be of tsunamigenic origin, but this is uncertain. Here, a numerical model was used to simulate the Storegga tsunami in Northumberland. Two scenarios of relative sea-level change, and a third incorporating high tide, were simulated with mortality estimated within the intertidal zone for the Mesolithic sites in the region. The results showed that only with the addition of high tide could the sediment deposit site have been inundated by the tsunami. At Howick, mortality estimates varied but were up to 100% within the resource-rich intertidal zone. The tsunami inundated a large area and would have led to the loss of key resources such as hazelnuts prior to the winter months. These combined effects would have probably been replicated throughout coastal settlements in Northern Britain, possibly leading to the contemporary population decline estimated to have occurred at this time.

Rapid sea-level rise during the Early Holocene around the North Sea coastal lowlands provided conditions under which estuarine and coastal features, with no modern equivalents, could be created. Investigation of nearshore sediments within the Outer Humber Estuary, UK, has identified a tidal lagoonal system, created between c. 9000 and 7800 cal a bp. These sequences show the initial flooding of a carr woodland, prior to the establishment of more saline conditions as the tidal lagoonal system developed. Inter-core comparisons, based on diatom and pollen analyses, suggest variations in the structure of a tidal lagoon setting, which probably lasted for only a brief period before being submerged by rising sea levels. The absence of an erosive contact in several of the sequences studied has permitted the creation of the oldest sea-level index points for the Outer Humber Estuary, providing validation for the current glacial isostatic adjustment models for the region.

The genus Equus was represented on the Iberian Peninsula by four species during the late Quaternary: the wild, now extinct, E. ferus (wild horse) and E. hydruntinus (European wild ass) and the extant, domestic E. caballus (horse) and E. asinus (donkey). The distribution and timing of the extinctions of the wild species and arrival of the domestic species is important to understand the changing environment and cultures through this dynamic period in one of the three southern Pleistocene glacial refugia in Europe. Here we collected data from all zooarchaeological studies that meet basic completeness criteria from the Palaeolithic to the Bronze Age (45–3.2 ka bp) and analysed the equine data in light of other large mammals at the same sites in order to document the species turnover and distributions through this culturally and ecologically dynamic period. The vast majority of Palaeolithic Equus were confidently identified as E. ferus, and by the Bronze age as E. caballus, with much uncertainty in between. Over time the larger equids (horses) were much more common than the smaller equids (asses). Equids were not common, but they were distributed across the southern Iberian peninsula through the Chalcolithic, and then appear to have become restricted to the drier eastern region in the Bronze Age. These analyses indicate that both E. ferus and E. hydruntinus went extinct by the end of the Pleistocene/Palaeolithic in Andalucia. Not all communities maintained equal numbers of equids, and their distribution changed with the changing climate through time, most notably between the Chalcolithic and the Bronze Age when confidence in species identification and local density of horses increase, but the distribution is restricted to the drier eastern region.

In areas of low uplift rate on the Pacific Coast of North America, reoccupation of emergent marine terraces by later high sea-stands has been hypothesised to explain the existence of thermally anomalous fauna (mixtures of warm and cool species) of last interglacial age. If uplift rates have been low for much of the Quaternary, it follows that higher (older) terraces should also show evidence of reoccupation. Strontium isotope analyses of fossils from a high-elevation marine terrace on Anacapa Island, California, yield ages ranging from ~2.4–2.3 Ma to ~1.4–1.5 Ma. These results indicate that terrace reoccupation and fossil mixing on Anacapa Island could have taken place over several interglacial periods in the early Pleistocene. Terrace reoccupation over this time period is likely a function of both a low uplift rate and the timing of orbital forcing of glacial–interglacial cycles. Climate change in the early Pleistocene was modulated by the 41 ka obliquity cycle, and glacial–interglacial cycles were much shorter than later in the Pleistocene. Nearby San Miguel Island also has evidence of terrace reoccupation, with Sr isotope ages of shells from several high-elevation terraces ranging from ~1.21–1.25 Ma to ~0.43–0.50 Ma. However, the frequency of terrace reoccupation was lower than on Anacapa Island. The uplift rate of San Miguel Island is higher than that of Anacapa Island and terraces formed when glacial–interglacial cycles were longer. The frequency of marine terrace reoccupation is controlled by the rate of tectonic uplift and the timing of orbital forcing of sea level change during glacial–interglacial cycles.

Combined natural processes and human activities shaped the late Holocene landscape history in many Mediterranean regions. This is especially true with areas subjected to specific human interest, such as coastal areas morphologically suitable to the establishment of harbours. Here, we test the hypothesis on the location of the Roman harbour Portus Trajectus in Peloro Cape (NE Sicily, Italy) and describe the evolution of the area over the last 3700 years through lithostratigraphic, geochemical, meiofauna and microfossil analyses performed on a new sediment core recovered from the coastal salt marsh Pantano Grande (aka Lago di Ganzirri). The age–depth model was developed on radiocarbon dates and geochemical fingerprinting of two tephra layers. Results indicate that the area underwent dramatic changes ca. 650 bce. The anthropogenic impact of Greek colonies may have contributed to modifying the coastal environment of Peloro Cape due to their widespread impact on natural resources. This happened at many localities in the Mediterranean, indicating the magnitude of impact of the Greek colonies over the landscape. According to our results, it is unlikely that the current Pantano Grande basin was used as a harbour in Roman times, although the presence of a harbour in the nearby Pantano Piccolo marsh cannot be excluded. Pantano Grande had been isolated from the sea for more than 2000 years. Human intervention in the 19^th century halted that isolation and provided the background for the ecological, economic and social functions the salt marsh performs today.