Paleoclimatology

Global climate cooled from the early Eocene hothouse (∼ 52-50 Ma) to the latest Eocene (∼ 34 Ma). At the same time, the tectonic evolution of the Southern Ocean was characterized by the opening and deepening of circum-Antarctic gateways, which affected both surface-and deep-ocean circulation. The Tasmanian Gateway played a key role in regulating ocean throughflow between Australia and Antarctica. Southern Ocean surface currents through and around the Tasmanian Gateway have left recognizable tracers in the spatiotemporal distribution of plankton fossils, including organic-walled dinoflagellate cysts. This spatiotemporal distribution depends on both the physicochemical properties of the water masses and the path of surface-ocean currents. The extent to which climate and tectonics have influenced the distribution and composition of surface currents and thus fossil assemblages has, however, remained unclear. In particular , the contribution of climate change to oceanographic changes, superimposed on long-term and gradual changes induced by tectonics, is still poorly understood.

It is possible to find out the continuity or discontinuity of the processes during the transitional periods with the involvement of the data of several related disciplines, in this case - the prehistoric archaeology and paleogeography. The dramatic changes in the landscape and climatic situation on the border of the Pleistocene - Holocene were undoubtedly a major factor in the process of settling the territory of the Middle Dnieper.

Biennial variations of marine palynomorph concentrations mirrored oceanographic conditions in the Magdalena Basin, Baja California Sur (Mexico), in the period from 1811 to 1907 (common era, CE), for which the sea surface temperature index (SSTI) showed predominantly negative anomalies. We analyzed 49 samples of laminated sediments taken from a core extracted at a water depth of 520 m. Changes in dinoflagellate assemblages and copepod egg abundances were compared to SSTI records and to El Niño Southern Oscillation (ENSO) and Pacific Decadal Oscillation (PDO) reconstructions. Copepods were the most abundant and showed a significant correlation with SSTI. Among the dinoflagellates, heterotrophs were the most abundant and did not correlate with SSTI. The lowest concentration of auto-trophs showed a significant and inverse correlation with SSTI. The canonical correlation analysis also indicated that copepods and autotrophs were modulated by variations in SSTI. Dinoflagellate richness and concentrations and copepod egg concentrations were low, indicating low productivity, and these values coincided with the negative SSTI anomalies. In contrast, the increase in concentrations from 1881 to 1907 CE coincided with positive SSTI anomalies. Also, even when marine palynomorphs showed no significant correlation with either ENSO or PDO, their concentrations increased during age intervals with combined negative conditions (La Niña, negative PDO) and decreased during combined warm conditions (El Niño, positive PDO).

Las variaciones bianuales de las concentraciones de palinomorfos marinos reflejaron las condiciones oceanográficas en la cuenca Magdalena, Baja California Sur (México), en el periodo de 1811 a 1907 (era común, EC), para el cual el índice de la temperatura superficial del mar (ITSM) demostró, predominantemente, anomalías negativas. Se analizaron 49 muestras de sedimentos laminados tomadas de un núcleo extraído a 520 m de profundidad del agua. Los cambios observados en los conjuntos de quistes de dinoflagelados y las abundancias de huevos de copépodos fueron comparadas con registros del ITSM y reconstrucciones de El Niño Oscilación del Sur (ENOS) y la Oscila-ción Decenal del Pacífico (ODP). Los copépodos fueron los más abundantes y presentaron una correlación significativa con el ITSM. Entre los dinoflagelados, los heterótrofos fueron los más abundantes y no se correlacionaron con el ITSM. La concentración más baja de autó-trofos mostró una correlación significativa e inversa con el ITSM. El análisis de correlación canónica también indicó que las abundancias de copépodos y autótrofos estuvieron modulados por las variaciones del ITSM. La riqueza y la concentración de dinoflagelados, así como las concentraciones de huevos de copépodos, fueron bajas, indicativo de baja productividad, y coincidieron con las anomalías negativas del ITSM. En contraste, se observó un incremento en las concentraciones de 1881 a 1907 EC, correspondiente a un aumento del ITSM. Además, aunque los palinomorfos marinos no mostraron una correlación significativa con ENOS ni con la ODP, las concentraciones aumentaron cuando se presentó la combinación de condiciones negativas de estos índices (La Niña, ODP negativa), pero disminuyeron en condiciones cálidas combinadas (El Niño, OPD positiva). Palabras clave: dinoflagelados, copépodos, temperatura superficial del mar, El Niño/Oscilación del Sur, Oscilación Decenal del Pacífico.

ABSTRACT Thick lake sediments discovered in the southern part of Czech Republic provide a high-resolution archive for detailed study of palaeoenvironmental changes during the Late Pleistocene to Holocene in eastern-central Europe. Until recently, no similar records were available for this important region in the transition from oceanic to continental macro-climatic settings. Using a multi-proxy approach that combines sedimentological, pollen-analytical, palaeozoological (Chironomids), geochemical and mineral-magnetic methods we demonstrate that major climatic events of the Late Glacial can be correlated with Atlantic rather than continental regimes as reported in palaeoclimatic literature for the area of the interest. The sensitivity of applied biological and abiological techniques to climatically-driven processes allows trans-regional comparisons and enables us to discuss the pattern of geographic variation in these processes. We are able to establish a clear relationship between vegetation cover, soil development and erosional processes. A short-term intra-Alleröd cool event has been correlated with the Gerzensee oscillation. Proxy evidence suggests that the early half of the Younger Dryas was rather humid, whereas the latter half was dry and had significant impact on vegetation, sedimentary dynamics and lake level status during the YD/Preboreal transition.

Investigations of chronology play a key role in the majority of archaeological research endeavors and are particularly pertinent to examinations of culture-environment relationships, especially during periods characterized by rapid and marked climatic variability and environmental reorganization. Rigorous evaluations of available data and robust methods are required if one wishes to reconstruct reliable chronologies, and this is especially the case when examining periods that are associated with a relatively few radiometric measurements. Such is the case for the Upper Paleolithic archaeological record documented in present-day France from 32,000 to 21,000 calibrated years BP. We take into account critically examined radiocarbon measurements from contextually secure archaeological contexts and employ a recently-developed method of Hierarchical Bayesian Modeling to reconstruct the chronology of archaeological cultures from the Middle Gravettian to the Badegoulian. The calculated chronological 2 intervals for each typo-technologically defined culture phase are compared to the Greenland ice core climatic record and a terrestrial paleoenvironmental record from Bergsee Lake (Southern Germany)-itself expressed in calendar years calculated with the same calibration curve employed in our age model-thereby permitting each archaeological culture to be correlated accurately with documented paleoclimatic variability.