Danuta J. Michczyńska

Progress in the holocene chrono-climatostratigraphy of Polish territory

The Holocene delivers a unique possibility to establish climatic stratigraphic boundaries based on detailed chronostratigraphy reflected in various facies of continental sediments, in their lithological parameters and organic remains. These sediments are dated by the 14C method in the case of organic remains, by counting annual laminations in lacustrine facies, and by dendrochronological method in the case of fluvial sediments.The existence of well dated profiles enables to reconstruct various climatic parameters like amplitudes of seasonal temperatures, types and frequency of extreme rainfalls and floods and, finally, to distinguish rare rapid changes and most frequent gradual ones. This reconstruction is based on the analogous effects of various types of present-day rainfalls.The current authors present a critical review of existing chronostratigraphic divisions starting from simple millennial division by Mangerud based on Scandinavian palynological stratigraphy of peat-bogs and Starkel’s concept based on fluctuations in rainfall and runoff regime reflected in fluvial and other facies of continental deposits.In the last decades, the calibration of 14C dates allowed a new approach to be used for the construction of the probability distribution function of these dates in various facies or types of sediments, which formed a background for distinguishing and correlating climatic phases and defining boundaries between them. These approaches have been creating new opportunities for revision of the existing chronostratigraphy.The aim of this paper is to present a revised version of chronostratigraphic division based on climatic fluctuations reflected in various facies of sediments on the territory of Poland and discuss their correlation with other European regions and global climatic changes.

SHAPE ANALYSIS OF CUMULATIVE PROBABILITY DENSITY FUNCTION OF RADIOCARBON DATES SET IN THE STUDY OF CLIMATE CHANGE IN THE LATE GLACIAL AND HOLOCENE

We report on a statistical analysis of a large set of radiocarbon dates for reconstruction of paleoclimate. Probability density functions were constructed by summing the probability distributions of individual (super 14) C dates. Our analysis was based on 2 assumptions: 1) The amount of organic matter in sediments depends on paleogeographical conditions; 2) The number of (super 14) C-dated samples is proportional to the amount of organic matter deposited in sediments in the examined time intervals. We quantified how many dates are required to give statistically reliable results. As an example, 785 peat dates from Poland were selected. The dates encompassed the Holocene and Late Glacial period. All dates came from the Gliwice Radiocarbon Laboratory. Results were compared with other paleoenvironmental records. Detailed analysis of the frequency distributions showed that preferential sampling plays an important part in the shape determination. The general rule to take samples from locations where visible changes of sedimentation are apparent (e.g. from the top and the bottom of the peat layer) results in narrow peaks in the probability density function near the limits of the Holocene subdivision.

A comparison of methods used for the calibration of radiocarbon dates.

Current calibration methods for single and replicate 14 C dates are compared. Various forms of tabular and graphic output are discussed. Results from all the methods show reasonable agreement but further methodological development and improvements in computer output are required. Comparison of existing techniques for a series of non-contemporaneous dates showed less agreement amongst participants on this issue. We recommend that calibrated dates should be presented as a combination of graphs and ranges, in preference to mean and standard deviation.

Improvement of the procedure for probabilistic calibration of radiocarbon dates.

A set of computer procedures for probabilistic calibration of 14C dates was developed at the Gliwice Radiocarbon Laboratory for the IBM PC compatible microcomputer. The program comprises three main options: 1) calibration of a single 14C date, 2) calibration of a set of arbitrary dates, 3) calibration of a set of related dates. Results of calibration are presented in the form of graphs and numeric data, including tables of selected quantiles and interquantile ranges of resulting probability distribution of cal age. In this paper, we present the aims of the program, with a short description of its structure, show examples of working with output data in terms of expected archaeological application, and consider the possibility of standardization of calibration procedures.

Frequency Distribution of Radiocarbon Dates as a Tool for Reconstructing Environmental Changes

Large sets of radiocarbon dates of 1019 peat, 155 speleothem, and 100 tufa samples, as well as dates of 330 flu- vial samples, were investigated in order to estimate environmental variability during the last 16,000 calendar years in Poland. All 14C dating was carried out in the Gliwice Radiocarbon Laboratory, and results are stored in the RoS database. Probability density functions (PDFs) were created by summing up (on the calendar timescale) individual age probability distributions of all dates for different types of material and for different regions of Poland. We used an updated version of the Gliwice Radio- carbon Laboratory calibration program GdCALIB. The 14C dates were calibrated using the IntCal04 calibration curve (Reimer et al. 2004), and results were compared with other paleoenvironmental records. The authors conclude that analyzing PDFs of different types of sediments can be helpful in the qualitative reconstruction of the past environment. The PDF for peat samples primarily reflects paleohydrological conditions; the PDFs for speleothem and tufa samples reflect changes in tem- perature and humidity, while analysis of the PDF created for fluvial data is in a general agreement with the PDFs constructed for peat samples.

Hydrological Changes after the Last Ice Retreat in Northern Poland Using Radiocarbon Dating

A simplified model of hydrological changes during the Late Glacial and Holocene is presented for the northern Polish regions that were ice covered during the Last Glacial. This reconstruction is based on a group of 197 radiocarbon dates from about 120 localities reflecting the sequence of alternating lake transgressions and regressions. The earliest transgressions were related to dead-ice melting (sometimes in 2–3 phases), while the later ones started during more humid phases. However, these were usually followed by regressions, which may have been connected with the formation of new drainage systems and with the overgrowing of shallow lakes by peat bogs.

Chronology of the Early Pre-Pottery Neolithic Settlement Tell Qaramel, Northern Syria, in the Light of Radiocarbon Dating

Archaeological excavations at the Syrian settlement of Tell Qaramel have been conducted since 1999. They are concentrated on remnants of the Protoneolithic and early stages of the Pre-Pottery Neolithic period. The settlement has revealed an extremely rich collection of everyday use of flint, bone, and mostly stone objects, such as decorated chlorite or limestone vessels; shaft straighteners used to stretch wooden arrow shafts, richly decorated in geometrical, zoomorphic, and anthropomorphic patterns; as well as different kinds of stones, querns, mortars, pestles, grinders, polishing plates, celts, and adzes. Excavations brought the discovery of 5 circular towers. Some 57 charcoal samples were collected during the excavations and dated in the GADAM Centre in Gliwice, Poland. The stratigraphy of the settlement and results of radiocarbon dating testify that these are the oldest such constructions in the world, older than the famous and unique tower in Jericho. They confirm that the Neolithic culture was formed simultaneously in many regions of the Near East, creating a farming culture and establishing settlements with mud and stone architecture and creating the first stages of a proto-urban being.

Kohonen Artificial Neural Networks and the IndVal Index as Supplementary Tools for the Quantitative Analysis of Palaeoecological Data

Abstract We applied two widely-used methods for data partitioning - constrained incremental sum-of-squares (CONISS) and Optimal Partitioning (OP) along with two supplementary methods, a Kohonen artificial neural network (self-organising map, SOM) and the indicator value (IndVal) index, for the quantitative analysis of subfossil chironomid assemblages from a palaeolake in Central Poland. The samples, taken from 79 core depths, were divided into 5-11 groups (five by SOM, seven by CONISS, 11 by OP), for which different numbers of indicator taxa were determined with the use of the IndVal index (18 for CONISS, 15 for SOM, 11 for OP). Only six indicator taxa were common to all three methods. The number of highly specific (p < 0.001) taxa was highest for SOM. Only the SOM analysis clearly reflected the rate of the changes in chironomid assemblages, which occurred rapidly in the Late Glacial (as a result of greater climate variability) and slowly in the Holocene (as a reflection of slow long-term changes in the local habitat, such as paludification). In summary, we recommend using SOM and the IndVal index in combination with CONISS and/or OP in order to detect different aspects of temporal variability in complex multivariate palaeoecological data.

Frequency Distribution of 14C Ages for Chronostratigraphic Reconstructions: Alaska Region Study Case

In this study, we test the possibility of using databases of radiocarbon ages to estimate boundaries of climatic chronozones. The Alaska region was chosen and compared with chronozones of 2 European countries: Poland and the Netherlands. The study included setting up a database of 14C ages published for climatic records from Alaska. Some 974 14C determinations on organic samples were selected and used to establish chronozones for the Late Glacial and the Holocene for the Alaska region. The selected data were calibrated and a summed probability density function (PDF) was calculated. The shape analysis of the constructed frequency distribution of 14C dates on calendar timescales together with the assumption about preferential sampling seems to be a useful tool for establishing calendar ages for boundaries of climatic periods, i.e. chronozones.

Reflection of climatic changes during interpleniglacial in the geoecosystems of South-Eastern Poland

Abstract About 70% of the last cold stage was taken by transitional phases of continuous fluctuations of climate and permafrost extension. All this is reflected especially well in slope types and the thickness of slope, fluvial and aeolian deposits. Very distinct and relatively fast changes took place around 33–30 ka BP: the aridification of climate with an ice sheet transgression, expansion of continuous permafrost and the onset of loess deposition. The greatest transformations of slopes and river valleys in the Carpathians and Subcarpathian Basins took place not in the coolest phases but during the Interpleniglacial. The authors exemplified a number of sites in Southern Poland documenting frequent fluctuations of climate and permafrost from that 25–30 ka long period. Calibrated dates of dated episodes correlate well with the δ18O curve from Greenland with frequent warmings. These rapid warmings are reflected in the higher rate of aggradation in valley floors and thick colluvial material deposited over slopes, both combined with a retreat of permafrost. The comparison with the Greenland 18O curve is valuable to establish a comparable chronology of events, even for such a distant area like Central-Eastern Europe.