Multi-proxy evidence for early to mid-Holocene environmental and climatic changes in northeastern Poland

Abstract

Declakes participants : Soumaya Belmecheri, Marc Desmet, Helmut Erlenkeuser, Jérôme Nomade.International audienceWe investigated the sedimentary record of Lake Hańcza (northeastern Poland) using a multi-proxy approach, focusing on early to mid-Holocene climatic and environmental changes. AMS 14C dating of terrestrial macrofossils and sedimentation rate estimates from occasional varve thickness measurements were used to establish a chronology. The onset of the Holocene at c. 11 600 cal. a BP is marked by the decline of Lateglacial shrub vegetation and a shift from clastic-detrital deposition to an autochthonous sedimentation dominated by biochemical calcite precipitation. Between 10 000 and 9000 cal. a BP, a further environmental and climatic improvement is indicated by the spread of deciduous forests, an increase in lake organic matter and a 1.7‰ rise in the oxygen isotope ratios of both endogenic calcite and ostracod valves. Rising δ18O values were probably caused by a combination of hydrological and climatic factors. The persistence of relatively cold and dry climate conditions in northeastern Poland during the first one and a half millennia of the Holocene could be related to a regional eastern European atmospheric circulation pattern. Prevailing anticyclonic circulation linked to a high-pressure cell above the retreating Scandinavian Ice Sheet might have blocked the influence of warm and moist Westerlies and attenuated the early Holocene climatic amelioration in the Lake Hańcza region until the final decay of the ice sheet

Climate Change During the Holocene (Past 12,000 Years)

“…Warmer conditions ensued, and between 10,000 and 9000 cal year BP pollen spectra showed an increased content of pollen from broad-leaved trees. The organic content of the lake sediments also increased (Lauterbach et al 2011). Figure 2.6 shows the reconstructed annual mean air temperature for south-central Sweden based on pollen data from Lake Flarken (Seppä et al 2005).…”

“…At the same time, Alnus-and in mountainous regions, Picea-spread widely. Then, at about 5000 cal year BP, the climate became wetter and colder (Pazdur 2004;Lauterbach et al 2011). It should be noted that the first signs of anthropogenic deforestation are recorded at 6500 cal year BP in this region.…”

“…A shift from clastic-detrital deposition to an autochthonous sedimentation dominated by biochemical calcite precipitation was identified in the Early Holocene by accelerator mass spectrometer (AMS) 14 C dating *11,600 cal year BP of Lake Hańcza (north-eastern Poland) sediments (Lauterbach et al 2011). The accumulation of silt and clay was replaced by organic-rich gyttja at 11,650 cal year BP also in eastern Latvia (Veski et al 2012).…”

Holocene sediment record from Briaunis palaeolake, Eastern Lithuania: history of sedimentary environment and vegetation dynamics

“…10.000-9900 and 9600-9500 14 C BP (Björck et al 1996;. Dis cussing the environmental pattern of this time interval in the eastern Baltic, a regional delay in the response to the early Holocene climatic improvement must be taken into account (Wohlfarth et al 2007;Stančikaitė et al 2008;Lauterbach et al 2011).…”

The Late Vistulian and Holocene evolution of Jezioro Lake: a record of environmental change in southern Poland found in deposits and landforms

“…mesozoic limestone or morainic clays), cycles of increasing concentration of calcium carbonate in profiles usually coincide with warm and wet periods and with intensive development of aquatic vegetation (De Klerk et al 2008;Lauterbach et al 2011). In the case of the Jezioro Lake, calcium carbonate is scarce in local sandy-gravelly fluvioglacial and glacial sediments originating from the Oder glaciation.…”