Holocene

The article presents an analysis of archaeological, archaeozoological data and historical documents and evidences on infl uence of human activity over the natural environment in Prut–Dniester area. The collected data revealed the original forested character of natural landscape on the main part of the region and chronology of large mammal species extinction on the territory under consideration.

Keywords: triple oxygen isotopes gypsum hydration water relative humidity lake sediments Younger Dryas Late Glacial–Holocene transition Atmospheric relative humidity is an important parameter affecting vegetation yet paleo-humidity proxies are scarce and difficult to calibrate. Here we use triple oxygen (δ 17 O and δ 18 O) and hydrogen (δD) isotopes of structurally-bound gypsum hydration water (GHW) extracted from lacustrine gypsum to quantify past changes in atmospheric relative humidity. An evaporation isotope-mass-balance model is used together with Monte Carlo simulations to determine the range of climatological conditions that simultaneously satisfy the stable isotope results of GHW, and with statistically robust estimates of uncertainty. We apply this method to reconstruct the isotopic composition of paleo-waters of Lake Estanya (NE Spain) and changes in normalized atmospheric relative humidity (RH n) over the last glacial termination and Holocene (from ∼15 to 0.6 cal. kyrs BP...

El maar de la Crosa ha estat sempre al punt de mira de molts investigadors del quaternari. El perquè s’explica per
tractar-se d’un dipòsit lacustre a l’interior del cràter d’un volcà; i, sabent que d’altres referents sempre han aportat
bons resultats paleoecològics. A banda, sabem que aquestes zones eren freqüentades per la nostra espècie
prehistòrica, de manera que també s’hi solen trobar assentaments arqueològics a les seves riberes. Tot això, partint de la base de la cronologia de l’erupció que se li havia assignat (plio-plistocè), malgrat els pocs estudis realitzats,
doncs això ens donava la perspectiva d’un dipòsit continu al llarg de tot el quaternari.
Ara, després d’haver fet tres sondatges, una prospecció geofísica i quatre datacions (tres de 14C i una d’isòtops),
coneixem el tipus de rebliment que conté i ens hem acostat més a llur cronologia, malgrat que només podem dir
que és més antic de fa 43,5 ka (14C ) i una probable edat de 90 ka (isòtops). També, que no s’ha trobat cap mena de
sediments palustres, o anòxics de fons de llac, doncs com a màxim la part superficial d’argiles i llims, per sobre
dels piroclasts retreballats, podrien pertànyer a un estanyol d’aigües somes.
Per tant, les perspectives d’obtenir amplis i resolutius resultats paleoambientals, que ens haguessin permès
conèixer el medi en què es desenvoluparen les poblacions paleolítiques, i de més recents, de les comarques
gironines, resten de moment frustrades, doncs les anàlisis paleobotàniques han resultat estèrils. D’altra banda,
tampoc s’hi ha observat cap altra resta paleobiològica susceptible d’anàlisi.

The laser diffraction (LD) is one of the most widely applied grain size measurement methods. The main advantages of LD are: (1) relatively short time of single measurement, (2) low cost of analysis, (3) simplicity of sample preparation, (4) great amount of acquired numerical data. One of the less frequently obtained parameters, often provided only by application of dedicated external hardware, is so-called “elongation parameter”, “grain shape factor” or “grain shape parameter”.
Due to the inability of direct export of numerical grain shape data from the Malvern Hydro Sight camera, authors proposed own method of digitalization and recalculation
of grain shape graphs produced by the Malvern software.
Acquired sedimentological and geochemical data were analysed using statistical methods, such as correlation/regression analysis and principal components analysis (PCA).
Proposed method of data extraction and analysis of grain shape parameters may be especially useful tool during investigation of Quaternary sediments and reconstruction of environmental changes.

The article presents the results of soil and archaeological study of the pedo-sedimentation sequence formed in the floodplain of the Derkul River (West Kazakhstan). The aim of the study was to reconstruct the stages of the alluvial sedimentogenesis alternating with relatively prolonged spans of soil formation, corresponding to the periods of floodplain agricultural development. It was established that floodplain sediment layer started to form as a result of stream sedimentation in the early Holocene; then this stage was followed by the relatively long-term soil formation period (5.6–3.8 cal. yr BC) resulting in a humus quasi-gleyic soil in the low floodplain (120–200 cm). The last period of soil formation (4.6–3.6 cal. yr BC) the floodplain was developed by man, which is displayed by the identified cultural horizon containing artifacts and having increased phosphorus content. At the end of the Subboreal period the next stage of alluvial sedimentation, started by the changed river hydrology regime, was found to be chronologically separated from the stage of stationary development of the floodplain by settled humans.

Cone Pond, New Hampshire, is an acidic (pH = 4.5) clearwater lake that is currently fishless. Historical records indicate declining fish populations between 1951 and 1966, but paleolimnological work using diatoms failed to find evidence for further recent acidification of this naturally acid site. We initiated new paleolimnological studies using mallomonadacean chrysophytes to further our understanding of Cone Pond's recent past. Our stratigraphic analyses indicate recent striking changes in the chrysophyte flora of this lake, with Mallomonas hindonii, a species only common in recently acidified lakes, replacing M. crassisquama, a cosmopolitan species that dominated the flora over the preceding 8000 yr; this recent change parallels the declines in fish populations. Because chrysophytes often bloom in early spring and are known, in other lakes, to experience changes in community composition before those expressed by the diatom community, a possibility is that chrysophytes track t...

Dinoflagellate cysts and XRF core scanning data from two marine sediment cores from embayments north (Bonavista Bay) and south (Placentia Bay) of Newfoundland show significant changes in ocean and atmospheric conditions of the SW Labrador Sea region during the last 5700 years. Fresh and cold conditions, probably accompanied by seasonal sea ice, prevailed both north and south of Newfoundland from c. 5.7 to 4.0 cal. kyr BP. This may be linked to intensified Labrador Current export of cold meltwater and/or sea ice from the Arctic, presumably related to warmer conditions in the northernmost latitudes and the prevalence of strong (north)westerly winds. After c. 4.0 cal. kyr BP, sea-surface conditions warmed up and sea ice decreased northeast of Newfoundland, but conditions were still cold south of Newfoundland. This suggests a decrease in Arctic meltwater export and westerly wind strength. After 2.9—2.5 cal. kyr BP, only minor changes in sea-surface conditions affected the study sites. S...

The vegetation of the northern Upper Rhine Graben (southwestern Germany) is reconstructed for the end of the Lateglacial and the Holocene by means of palynological analyses in combination with AMS14c dating. Analogous to adjacent lowland areas, the Younger Dryas climatic deterioration didnotresult in a complete deforestation of the area and open pine woodlands with locally birch stands and shrubs persisted. A subdivision of the Younger Dryas period, into a humid first phase, followed by a dry second phase was also reflected in our records. For the Holocene, the pollen diagrams show two regionally different vegetation developments, related to substrate and variations in annual precipitation: in the south the ‘classical’ succession of pine then hazel is followed by other deciduous trees, whereas in the northern part, pine kept its dominance far into the Subboreal.

Copyright © 2015 Khoshravan and Jabbari, This is an open access article published under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Preferred citation for this article:

This report outlines the results of the academic research on historical evolution of the Ems-Dollard estuary. We analyzed the channel-bar patterns and changes in channel volume over the last 200 years and the role of resistant layers in the estuary’s substrate. For this, historical bathymetry was derived from historical maps and a new map with position of resistant layers in the substrate of the estuary was compiled. Holocene clays and peats are resistant layers that locally delay morphological development and form scour holes in the channel bed. Pleistocene resistant layers are more resistant and affect the entire estuary. They limit channel depth and consequently cause widening, resulting in mid-channel bar formation and increased channel curvature. Furthermore, deeper channel confluences preferentially form where resistant layers were absent. The combined effects force the position and dimensions of confluences and bars. Where future sea-level rise may cause channel volumes to increase, antecedent geology will be more exposed, which could lead to unexpected changes in the channel pattern. Based on the demonstrated importance of resistant layers in the past, we recommend to account for them in the likely response of estuaries to sea-level rise. Resistant layer maps could be further improved, when more geological data is incorporated around the watershed between the Eastern and Western Ems.
Over the last two centuries, channel volumes (below NAP ~MSL) have decreased by 1 to 4.6 Mm3 /yr on average, this trend was interrupted in the 1960ies and 1970ies when sediment was extracted from the system. Gas-extraction induced subsidence and especially sea-level rise will cause morphological changes the coming century. Assuming that channel and shoal morphology do not change, 1.5 to 5.3 Mm3/yr of sediment would be needed (for 0.25 and 1.2 m respectively sea-level rise in 2100). Although this is in the same order of magnitude as natural sediment import in the channels over the last two centuries, it is unknown whether the sediments can be provided. Because the estuary needs sediment, sand extraction can best be avoided. Stimulating saltmarsh growth, as has been done in the past, could help flood protection and at the same time reduce suspended sediment concentrations. We recommend to study the effect of this measure on the shoals and channels.