Search results for " planetary"

Dating Bulk Sediments from Limnic Deposits Using a Grain-Size Approach

2013

Radiocarbon measurements on bulk subaqueous sediments typically provide ages significantly older than actual time of deposition. This is generally caused by the presence of reworked organic compounds, which are depleted in 14C. To explore this issue of age heterogeneity, we collected 4 organic-rich samples from varying depths in a lake sediment core at the Gemündener Maar (Eifel, Germany), a lake of volcanic origin. We divided each sample into 5 standard grain-size fractions: gravel, sand, silt, clay, and 1 fraction smaller than 0.45 μm. These were cleaned separately using a standard acid-alkali-acid treatment. The highly organic gravel-size fraction provided the youngest 14C ages of all gr…

Potential Freshwater Reservoir Effects in a Neolithic Shell Midden at Riņņkalns, Latvia

2014

Riņņukalns is the only known prehistoric shell midden in the eastern Baltic, and is one of the few middens in northern Europe consisting mainly of freshwater mussel shells. Situated on the Salaca River at the outlet of Lake Burtnieks, in northeastern Latvia, the site was originally excavated in the 1870s, and reinvestigated several times over the following decades. A new excavation in 2011 showed that part of the midden remained intact. The new exposure, dated to the later 4th millennium cal BC, yielded rich fishbone and mollusk shell assemblages, herbivore, human and bird bones, and a wide range of artifacts typical of a subsistence economy based on fishing, hunting, and gathering. Human r…

Annual 14C Tree-Ring Data Around 400 AD: Mid- and High-Latitude Records

2019

ABSTRACTTwo tree-ring series, one from a high-latitude pine tree (located in northern Scandinavia) and one from a mid-latitude oak tree (located in eastern Germany) were analyzed for radiocarbon (14C) at annual resolution. The new records cover the calendar date ranges 290–460 AD and 382–486 AD, respectively, overlapping by 79 yr. The series show similar trends as IntCal13. However, some significant deviations around 400 AD are present with lower Δ14C (higher 14C ages). An average offset between the two new series and IntCal13 of about 20 years in conventional 14C age is observed. A latitudinal 14C offset between the tree sites in central and northern Europe, as would be expected due to the…

Tracing the Alkinoos Harbor of ancient Kerkyra, Greece, and reconstructing its paleotsunami history

2017

International audience

Palaeoenvironmental evidence for the impact of the crusades on the local and regional environment of medieval (13th–16th century) northern Latvia, ea…

2015

This paper evaluates the impact of the crusades on the landscape and environment of northern Latvia between the 13th–16th centuries (medieval Livonia). The crusades replaced tribal societies in the eastern Baltic with a religious state (Ordenstaat) run by the military orders and their allies, accompanied by significant social, cultural and economic developments. These changes have previously received little consideration in palaeoenvironmental studies of past land use in the eastern Baltic region, but are fundamental to understanding the development and expansion of a European Christian identity. Sediment cores from Lake Trikāta, located adjacent to a medieval castle and settlement, were s…

Broadleaf deciduous forest counterbalanced the direct effect of climate on Holocene fire regime in hemiboreal/boreal region (NE Europe)

2017

Abstract Disturbances by fire are essential for the functioning of boreal/hemiboreal forests, but knowledge of long-term fire regime dynamics is limited. We analysed macrocharcoal morphologies and pollen of a sediment record from Lake Lielais Svētiņu (eastern Latvia), and in conjunction with fire traits analysis present the first record of Holocene variability in fire regime, fuel sources and fire types in boreal forests of the Baltic region. We found a phase of moderate to high fire activity during the cool and moist early (mean fire return interval; mFRI of ∼280 years; 11,700–7500 cal yr BP) and the late (mFRI of ∼190 years; 4500–0 cal yr BP) Holocene and low fire activity (mFRI of ∼630 y…

Multi-archive summer temperature reconstruction for the European Alps, AD 1053–1996

2012

We present a multi-archive, multi-proxy summer temperature reconstruction for the European Alps covering the period AD 1053e1996 using tree-ring and lake sediment data. The new reconstruction is based on nine different calibration approaches and errors were estimated conservatively. Summer temperatures of the last millennium are characterised by two warm (AD 1053e1171 and 1823e1996) and two cold phases (AD 1172e1379 and 1573e1822). Highest pre-industrial summer temperatures of the 12th century were 0.3 � C warmer than the 20th century mean but 0.35 � C colder than proxy derived

New tree-ring evidence for the Late Glacial period from the northern pre-Alps in eastern Switzerland

2018

Abstract The rate and magnitude of temperature variability at the transition from the Last Glacial Maximum into the early Holocene represents a natural analog to current and predicted climate change. A limited number of high-resolution proxy archives, however, challenges our understanding of environmental conditions during this period. Here, we present combined dendrochronological and radiocarbon evidence from 253 newly discovered subfossil pine stumps from Zurich, Switzerland. The individual trees reveal ages of 41–506 years and were growing between the Allerod and Preboreal (∼13′900–11′300 cal BP). Together with previously collected pines from this region, this world's best preserved Late…

2020

To place recent hydroclimate changes, including drought occurrences, in a long-term historical context, tree-ring records serve as an important natural archive. Here, we evaluate 46 millennium-long ...

Concord and discord among Northern Hemisphere paleotemperature reconstructions from tree rings

2019

Abstract We review the current generation of large-scale, millennial-length temperature reconstructions derived from tree rings and highlight areas of agreement and disagreement among these state-of-the-art paleotemperature estimates. Although thousands of tree ring-width chronologies are now available from temperate and boreal forest sites across the Northern Hemisphere, only a small fraction of those records are suited as proxies for surface temperature. Maximum latewood density is clearly a superior temperature proxy but is less available, with few densitometric records that are both long and up-to-date. Compared to previous efforts, the newest generation of tree-ring reconstructions cor…