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Authigenic Mg‐calcite and dolomite are frequently observed in restricted, evaporative environments, such as lagoon or lake systems, but their formation is difficult to capture due to slow growth rates. Lake Neusiedl, an alkaline and subhaline lake with a mean water depth of 0.7 m in Austria, offers a natural system to study the precipitation of Ca‐Mg‐carbonate phases, which occur as fine‐grained, unconsolidated and largely homogenized mud. To elucidate the timing and formation mechanisms of these authigenic carbonate phases, the mineralogical and isotopic composition and radiocarbon age of different sediment grain‐size fractions from <0.2 to >3.0 μm were analysed. X‐ray diffraction analyses show two broad peaks of Mg‐calcite and protodolomite (lacking ordering peaks), suggesting that the carbonates are authigenic rather than detrital in origin. Calibrated carbon‐14 ages range between 200 cal yr bp and 3700 cal yr bp. The linear correlation of age and grain size suggests a very slow growth rate of single crystals of 0.23 to 0.60 μm/ka. These rates suggest an extremely slow sedimentation rate in a shallow lake that existed during most of the Holocene. The higher abundance of protodolomite in older grain fractions, in contrast to the presence of high‐Mg calcite in the youngest fractions, suggests a growth succession where high‐Mg calcite develops first and subsequently transforms into protodolomite. Much higher ages of 6 cal ka bp to 15 cal ka bp are measured in carbonates of lake deposits exposed on land, in a section north‐west of the recent lake, suggesting a growth rate of those carbonate minerals of 0.13 μm/ka. These time constraints further suggest that some carbonate grains could already have nucleated from lake water before or during the last glacial maximum, although under slightly different hydrochemical conditions. [ABSTRACT FROM AUTHOR]

Radiocarbon (14C) analyses are commonly used to determine the absolute age of floating tree-ring chronologies. At best, with the wiggle-matching method, a precision of 10 years could be achieved. For the early Middle Ages, this situation has been markedly improved by the discovery of rapid changes in atmospheric 14C concentrations in tree-rings dated to 774/775 and 993/994 AD. These high-resolution changes can be used to secure other floating tree-ring sequences to within 1-year accuracy. While a number of studies have used the 774 even to secure floating tree-ring sequences, the less abrupt 993 event has not been so well utilized. This study dates a floating pine chronology from Ujście in Wielkopolska (Greater Poland) (NW Poland), which covers the 10th century period and is critical for studies on the beginning of the Polish State to the calendar years 859–1085 AD using the changes in single year radiocarbon around 993/4 AD. [ABSTRACT FROM AUTHOR]

In 2008-2009, during construction of the ring road around the town of Sztabin in NE Poland, archaeological rescue excavations were carried out at site no. 12 in Horodnianka. The excavations revealed the remains of a defensive settlement from the Bronze Age, with a total surface of 3 ha. Concentric wooden palisades reinforcing the settlement were situated on sandy, elevated embankments of the Biebrza River. Altogether, 189 samples of archaeological wood, mainly oak (Quercus sp.), were collected. Dendrochronological analysis demonstrated that the trees were cut down within a relatively short period of only 22 yr. On the basis of 22 contemporaneous dendrochronological sequences, the average curve HOR_AA1 (89 yr long) was constructed. However, attempts at dating the average curve against the chronologies from adjacent areas were unsuccessful. Therefore, determination of the time interval represented by the palisade oaks was attempted with the wiggle- matching method. Radiocarbon dating using liquid scintillation counting (LSC) was conducted for 6 suitable samples selected from the average curve. The 14C results, after calibration, suggest the dates of cutting the oaks outlining the Horodnianka chronology most probably fall in the time interval 870-795 cal BC. This means that Horodnianka could be the furthest northeastern defensive fortification of the Lusatian culture. [ABSTRACT FROM AUTHOR]