Radiocarbon chronology of glacial lake sediments in the Retezat Mts (South Carpathians, Romania): a window to Late Glacial and Holocene climatic and paleoenvironmental changes

Abstract

As a first piece in a series of Late Quaternary paleoecological studies on the glacial lake sediments of the Retezat Mountains, this study discusses radiocarbon chronology and sediment accumulation rate changes in two sediment profiles in relation to lithostratigraphy, organic content, biogenic silica and major pollenstratigraphic changes. A total of 25 radiocarbon dates were obtained from sediments of two lakes, Lake Brazi (TDB-1; 1740 m a.s.l.) and Lake Gales (Gales-3; 1990 m a.s.l.). Age-depth modeling was performed on TDB-1 using calibrated age ranges from BCal and various curve-fitting methods in psimpoll. Our results suggest that sediment accumulation began between 15,124-15,755 cal yr BP in both lakes and was continuous throughout the Late Glacial and Holocene. We demonstrated that local ecosystem productivity showed delayed response to Late Glacial and Early Holocene climatic changes in the subalpine and alpine zones most likely attributable to the cooling effect of remnant glaciers and meltwater input. However, regional vegetation response was without time lag and indicated forestation and warming at 14,450 and 11,550 cal yr BP, and cooling at ca. 12,800 cal yr BP. In the Holocene one major shift was detected, starting around 6300 cal yr BP and culminating around 5200 cal yr BP. The various proxies suggested summer cooling, shorter duration of the winter ice-cover season and/or increasing size of the water body, probably in response to increasing available moisture.Addresses: E. K.

Limnological changes in South Carpathian glacier-formed lakes (Retezat Mountains, Romania) during the Late Glacial and the Holocene: A synthesis

“…Lake Gales is deeper than Lake Brazi with a maximum depth of 20 m and a surface area of 3.68 ha (Magyari et al, 2009a). Nowadays, the lake is oligotrophic, its summer pH is between 7.1-7.67 and its conductivity is about 16.2-16.4 µS/cm Kövér, 2016).…”

“…The first was obtained from Lake Brazi (Tăul dintre Brazi, 1740 m, 45°23'47"N, 22°54'06"E; Fig. 1), a small and shallow lake with maximum water depth of 1.1 m and a surface area of 0.4 ha (Magyari et al, 2009a). Nowadays, the lake is oligotrophic, its summer pH ranges between 6.1-6.7 and its conductivity between 10-16 µS cm -1 Kövér, 2016).…”

“…The sediment stratigraphy and organic content record of the lakes investigated were described in detail in Magyari et al (2009aMagyari et al ( , 2012, Buczkó et al (2013) and Hubay et al (2016).…”

“…The South Carpathian Mountains received relatively little attention in paleolimnological studies until recently when both local (e.g. Magyari et al, 2009a) and larger scale projects (e.g. Catalan et al, 2009;Heiri et al, 2014) started.…”

“…Catalan et al, 2009;Heiri et al, 2014) started. Within the multiproxy paleoecological project PROLONG (Magyari et al, 2009a) several biotic and abiotic proxies have been studied on sediment cores of four mountain lakes including sediment organic matter (as loss on ignition) and biogenic silica content, geochemical element concentrations, diatoms, chrysophycean cysts, cladocera, ostracods and chironomids (Korponai et al, 2011;Braun et al, 2012;Buczkó et al, 2012;Iepure et al, 2012;Tóth et al, 2012;Buczkó et al, 2013;Soróczki-Pintér et al, 2014;Tóth et al, 2015). In this study we concentrate on proxy records from two lakes on the northern slopes of the Retezat Mountains.…”