New results of a palynological study of the Lake Doroninskoe sediments (Eastern Siberia, Transbaikalia)

This article presents the results of the study of the bottom sediments of the meromictic Lake Doroninskoe. For the study, the method of spore-pollen analysis was used. The record showed that during the accumulation of 65 cm of the sediment layer in the Chita-Ingodinskaya depression, pine and larch predominated along the ridges, with steppe and meadow associations in the lower parts of the depression. According to regional correlations, the distribution of light-coniferous-taiga vegetation in Transbaikalia occurred as early as the Middle Holocene, and it did not undergo cardinal changes until modern times. According to these data, sediments may have accumulated during this time period.

Late quaternary palaeoclimates of western India : A geoarchaeological approach

Western India comprises parts of the states of Rajasthan, Gujarat and Maharashtra. This region has varied climate and landscape. Northwestern Rajasthan is an area of internal drainage, with dunes, playas and rocky pediments. The Luni, Sabarmati and Mahi basins to the south of this zone show the influence of both aeolian and fluvial processes. Aeolian landforms are absent in the Nrmada, Tapi, Godavari and Bhima basins and fluvial aggradation has alternated with erosion in response to climatic change. Dominance of semi-arid to arid climate throughtout the Quaternary in the entire region has ment that Quaternary geological processes have been weak, preserving many features of the Tertiary in the present landscape. The variation in the geomorphic processes shaping the landscape and the complex links between geomorphic proceses and climate mean that our understanding of palaeoclimates in western India in far from complete. This paper gives an overview of the Late Quaternary palaeoclimate of western India, based primarily on recent work by the authors in Rajasthan and Maharashtra. Some issues in the palaeoclimatic interpretation of the geological record are discussed. Signatures of Late Pleistocene aridity, fluctuating climate during the Pleistocene Holocene transitional period, early Holocene humid climate and increased aridity from the middle Holocene onwards are reflected in different ways in the different landscape settings.

Past monsoons : A review of proxy data and modelling

Recent modelling studies have given insight into the role of internal feedback processes among components of the climate system on the evolution of monsoon strength since the Last Glacial Maximum (21,000 years ago). Here we present an overview of these modelling studies related to the summer monsoon over India and northern Africa. These studies indicate that the seasonal insolation changes alone do not explain the observed extent of hydrological changes during the early and middle Holocene over northern Africa. To simulate the extent of observed changes during this period incorporation of vegetation as an active component in climate models appears to be necessary. Over the Indian region, model results show that precipitation-soil moisture feedbacks play an important role in determining the response of the monsoon to changes in insolation and glacial-age surface boundary conditions. Indian monsoon strength from proxy records during the early and middle. Holocene have also been used in conjunction with coupled ocean atmosphere general circulation model experiments to refute the suggestion that semi-permanent warm surface conditions prevailed over equatorial Pacific ocean from 11 to 5ka.

Microfossil as proxy for palaeoclimate and palaeoceanography

Recent global warming has been addressed due to human activity that causes increased greenhouse gases. However, there are inherent uncertainties in the statement, one of them is the level of natural variability inherent in the climate system. Climate data from measuring instruments are not long enough to evaluate climate variability and current climate evolution. Therefore, we need climate data that has a long back span. To get adequate past climate data, we need natural phenomena which are climate dependent. This natural phenomenon provides a proxy record of the climate. This study of proxy data is the foundation of palaeoclimatology and paleoceanography. Microfossils (i.e., foraminifera, palynomorphs, nannofossils) which in geology are used as a standard tool in biostratigraphy for both age determination and paleoenvironment and correlation, can also be used as a proxy for obtaining paleoclimate and paleoceanography data. Using microfossil as a proxy to study past climate and paleoceanography, we need an understanding of the type of proxy data available and methods used in their analysis.In addition to the dating method (biostratigraphy), there are many climate and oceanography parameters that can be obtained from microfossil proxies such as: sea surface temperature (SST), sea surface salinity, (SST) climate (warm, cold, dry, wet), precipitation, productivity, oxygen content and organic carbon level, deep sea current and ventilation/upwelling, thermocline and mixed layer, variability deep water properties, CCD, bathymetry, sea level change and dissolution. The methods to obtain data fall into some categories e.g., faunal/floral displacement, morphology changes, transfer function/modern analog and isotopic content. Another method that can be used is observing microfossil assemblages and link them to ecological changes associated with climate change and its paleoceanography.A paleoclimate and paleoceanography study using microfossil proxies has been conducted in the Cendrawasih bay, Papua, Indonesia. The study shows that climate in the tropical west Pacific margin (Cendrawasih bay) during Late Pleistocene to Holocene shows high variability. There are nineteen climate changes occurred during Holocene. Early Holocene dated as ca. 11,800-year BP marked by rapid warming with SST differences to last glacial is about 4oC. Early to Middle Holocene (ca. 5960-year BP) marked by increasing temperature up to 2oC, interrupted by cooling at ca. 11230-, 8310- and 7120-years BP. At Middle Holocene temperature decreased rapidly and reached its peak at around ca. 3150-year BP. After cooling at ca. 3150-year BP, temperature increased and then decreased with its peak at ca. 1710-year BP. Since ca. 1710-year BP to Recent, temperature shows warming trend. SST from MAT indicates warming environment near to 1.5oC. The warming trend was interrupted by rapid cooling and warming at ca. 300-year BP. This last warming trend indicates that global warming had started before industrial era and rapid cooling, or warming can occur without anthropogenic gases influence. The typical Holocene climate of warm-wet, dry-cold reverse and become warm-dry, cold-wet during ca. 790-370-year BP and then reversed back to preceding state.Semi-restricted basin occurred since last glacial with anaerobic condition and estuarine circulation system. Warming during interstadial 1e-1a, causing reverse water circulation and basin become sub-aerobic with anti-estuarine circulation. A lot of terrestrial organic matter flow to the bay and increase acidity and carbonate dissolution. High sedimentation found occurred during glacial period especially at the end of glacial period. Rapid warming during late glacial to middle Holocene, rising relative sea level and the bay become more open marine with well oxygenated bottom water and high marine productivity. Warm temperature and deeper thermocline depth (~ 250 m) in west Pacific occurred up to ca. 5960-year BP. Decreasing Sea surface temperature at ca. 5960-year BP and drop of relative sea level causing sub-aerobic condition inside bay. The semi-restricted state with sub-aerobic condition occurred up to Recent.Distribution of Sphaeroidinella group in the tropical west Pacific shows strong correlation with thermocline depth and reflect El Niño frequency event. Early middle Holocene dominated by La Niña-like condition and since Middle Holocene (ca. 5960-year BP) frequent El Niño event began to occur.

The Middle Holocene ‘funerary avenues’ of north-west Arabia

The desert regions of the Arabian Peninsula and Levant are criss-crossed by innumerable pathways. Across large areas of north-west Arabia, many of these pathways are flanked by stone monuments, the vast majority of which are ancient tombs. Recent radiometric dating indicates that the most abundant of these monuments, elaborate and morphologically diverse ‘pendant’ structures, were constructed during the mid-to-late third millennium BCE. Thousands of kilometres of these composite path and monument features, ‘funerary avenues’, can be traced across the landscape, especially around and between major perennial water sources. By evidencing routes of human movement during this period, these features provide an emerging source for reconstructing important aspects of ancient mobility and social and economic connectivity. They also provide significant new evidence for human/environment interactions and subsistence strategies during the later Middle Holocene of north-west Arabia, and suggest the parallel existence of mobile pastoralist lifeways and more permanent, oasis-centred settlement. This paper draws upon the results of recent excavations and intensive remote sensing, aerial and ground surveys in Saudi Arabia to present the first detailed examination of these features and the vast cultural landscape that they constitute.