Palaeoclimates

https://web.rgzm.de/publikationen/details-neuerscheinungen/article/neuerscheinung-resilience-and-reorganisation-of-social-systems-during-the-weichselian-lateglacial-i/
At the end of the Pleistocene, hunters and gatherers had to adapt themselves and their social systems in North-West Europe to abrupt climate and significant environmental changes. This adaptation process is reconstructed in detail based on 25 archaeological sites and in connection with high-resolution climate and environmental archives.
Based on this rigorous correlation, a chronological relation between climatic, environmental, and cultural change is established that for the first time allows founded statements about cause and effect. This study reveals that the Pleistocene social systems could cope with the significant climate changes but that they were stretched beyond their limits by quickly changing environmental conditions.
For an Open Access PDF you can also go there: https://books.ub.uni-heidelberg.de/propylaeum/catalog/book/735?lang=de

Late Neolithic and Early Bronze Age Central China was the scene of important cultural developments, which impacted on agricultural practices and local vegetation. Using phytolith data from 4 archaeological -sites and a survey of a further 11 sites in Henan this project investigates changing crop choices, developments in crop processing and, to a lesser extent, differing local environments both temporally and spatially.

For analogues of global warming, the mid-Cretaceous is held up as both an archetype and a warning. Using a combination of theoretical models and geological evidence, a consensus is revealing that polar latitudes experience the greatest degree of warming during global greenhouse conditions. The Tupuangi Formation of the Chatham Islands, New Zealand, is the highest latitude (~ 75-80°S) floral assemblage ever discovered from the mid- Cretaceous; as such, the Chatham Islands provide an unprecedented perspective into the most extreme effects of global warming. This research has provided important climatic and evolutionary implications for the flora and fauna in both a regional (e.g. Zealandia, Australia and Antarctica) and global context. The Tupuangi Formation, and its fossil flora record, reveals a benign terrestrial polar environment amid the regional context of tectonic rifting, and a global context of extreme greenhouse conditions. Based on the timing of structural and sedimentological attributes of the Tupuangi Formation, the tectonic and palaeoenvironmental context of the region was established for the first time. It was concluded that these sediments were deposited in a terrestrial, failed-rift basin of Eastern Zealandia prior to the onset of seafloor spreading between Zealandia and Marie Byrd Land, West Antarctica. Without ongoing orogenesis in the region, a trend of fluvial aggradation and thermal subsidence followed this failed-rift event; this resulted in an upsequence transition from high to low fluvial flow-rate, with increasing prevalence of swamps, peats and paralic settings. This thesis includes a quantitative spore and pollen analysis to achieve comprehensive biostratigraphic correlations of the Tupuangi Formation and ecological interpretations of the mid-Cretaceous south polar region. As typical for terrestrial basins, the Tupuangi Formation features several age-old problems of spore and pollen biostratigraphy and ecological reconstructions, including preservation biases and the inclusion of older, reworked spores and pollen. This study demonstrates, that these variables can be minimised by employing a range of novel statistical measures, and the systematic removal of contaminated samples. This approach results in more reliable biostratigraphic correlations and ecological interpretations. This study documents seventy-seven distinct spore and pollen species, including five new pollen species (Araucariacites saganii, Balmeiopsis discus, Liliacidites exquisitus, Podocarpidites microradiatus and Trichotomosulcites hemisphaerius) and two fern spores (Klukisporites sphaerogoufus, Biretisporites labruplenus); a total of over one hundred spore-pollen species was found. Spore and pollen biostratigraphy was employed to derive the first island-wide stratigraphic correlation of the Tupuangi Formation. Three newly reported unconformities were identified; the uppermost of these is concurrent with the Zealandian ‘breakup unconformity,’ a time-gap of ~ 4-5 Ma demarcating the uplift phase of rifting between Zealandia and Antarctica. Aligning the spore and pollen assemblage into the global scheme, a Ngaterian to Mangaotanean (Cenomanian to Turonian; ~ 99-90 Ma) age was constrained for the sequence. The age of this sequence is concurrent with the initiation of two related global events: 1) the primary stage of flowering plant (angiosperm) diversification; and 2) the mid-Cretaceous thermal maximum. The palynological record of the Tupuangi Formation provides direct evidence for the first event, and indirect evidence of the second. Abundance data of spore and pollen species reveal an overall predominance of gymnosperm taxa in the floral ecology; conifers as the primary overstorey components, and an understorey comprised of smaller gymnosperms, ferns, angiosperms, bryophytes, lycopods and ‘seed-ferns’. A tentative analogy is drawn to the conifer-dominated boreal forests of the Northern Hemisphere. There is increasing angiosperm diversity and abundance upsequence, and this work corroborates that the angiosperms spread to the high latitudes instep with the warming global climate of the time. As such, the increasing diversity and abundance of angiosperm pollen of such a high palaeolatitude locality corroborate an increasing global temperature. However, contrary to previous findings, this study reveals that the angiosperm diversification at south polar latitudes did not result in an ecological replacement of understorey taxa, but instead increased the overall species richness. As such, it is interpreted that the angiosperms formed new ecological niches, rather than invade and outcompete the established flora in pre-existing niches.

New palynological evidence shows that the beginning of cereal use in central Europe probably started during the transition from the Boreal to Older Atlantic period in the region of Lake Zürich (Switzerland). This is about 2000 years before the first Neolithic lake dwellings there, and much earlier than previously reported. The pollen profiles of Wallisellen- Langachermoos and Zürich-Mozartstrasse reveal several phases of human impact between 6500 and 4500 BC cal. Pollen of cereals and of plants showing small-scale forest openings - possibly related to fire events - hint to a society of forager-farmers. We propose to connect these communities to the Late-Mesolithic, Early Neolithic (La Hoguette) and Middle Neolithic cultures of central Swiss Plateau. For the areas belonging to the zone of western mediterranean neolithisation we therefore have to reject the idea of a Neolithic revolution and 'landnam' by farmers. The neolithisation of the central Swiss Plateau was more probably a long-lasting process of subsequent and discontinuous acculturation of the local, Late-Mesolithic population. Neolithic elements such as the use of cereals were quickly distributed among them. Our results obtained from palynological and archaeological studies give new aspects for the process of neolithisation on the Swiss Plateau and in central and western Europe in general. (Abstract IPNA Basel)

The hydrography of the Indian-Atlantic Ocean gateway has been connected to high-latitude climate dynamics by oceanic and atmospheric teleconnections on orbital and suborbital timescales. A wealth of sedimentary records aiming at reconstructing the late Pleistocene paleoceanography around the southern African continent has been devoted to understanding these linkages. Most of the records are, however, clustered close to the southern South African tip, with comparatively less attention devoted to areas under the direct influence of frontal zones of the Southern Ocean/South Atlantic. Here we present data of the composition and concentration of the diatom assemblage together with bulk biogenic content and the alkenone-based sea surface temperature (SST) variations for the past 350 kyr in the marine sediment core MD02-2588 (approximately 41°S, 26°E) recovered from the southern Agulhas Plateau. Variations in biosiliceous productivity show a varying degree of coupling with Southern Hemisphere paleoclimate records following a glacial-interglacial cyclicity. Ecologically well-constrained groups of diatoms record the glacial-interglacial changes in water masses dynamics, nutrient availability, and stratification of the upper ocean. The good match between the glacial maxima of total diatoms concentration, Chaetoceros spores abundance, and opal content with the maximum seasonal cover of Antarctic ice and the atmospheric dust records points to a dominant Southern Hemisphere forcing of diatom production. Suborbital variability of SST suggests rapid latitudinal migrations of the Subtropical Front and associated water masses over the southern Agulhas Plateau, following millennial contractions and expansions of the subtropical gyres. Warmings of the upper ocean over site MD02-2588 during terminations IV to I occurred earlier than that in the Antarctic Vostok, which is indicative of a Northern Hemisphere lead. Our multiparameter reconstruction highlights how high-latitude atmospheric and hydrographic processes modulated orbital highs and lows in primary production and SST as triggered by northward transport of Si, eolian dust input, and latitudinal migrations of frontal zones.

The Paleocene flora from Seymour Island, Antarctica, is one of the most diverse floras of this age in the Southern Hemisphere. First collected on the Swedish South Polar Expedition (1901–1903), it was described by Dusén in 1908 as having 87 leaf taxa. Forty-seven angiosperm taxa were described and/or illustrated. Many species are based on single specimens, and the flora has not been re-examined in its entirety since it was first described. This study is the first reassessment of the flora updating the original research using current methodologies, and permitting evaluation of the flora in the context of modern ideas on plant evolution and palaeogeography. This paper continues the revision of the material first studied by Dusén; a previous paper described the ferns and gymnosperms; here we describe the angiosperms. The revision is based on the original collections held at the Swedish Museum of Natural History, together with the first major new collections held at the British Antarctic Survey. Among the taxa recognized by Dusén, we recognize only three entire-margined and 11 tooth-margined angiosperms. This revision to 14 species notably lacks the two tropical elements originally described from the flora, Mollinedia seymourensis and Miconiiphyllum austral. Hence, its status as a ‘Mixed Flora’ comes into question and influences climatic interpretations based on Gondwanan floras.

ABSTRACT:
There is a known bias in C/N, d13C and d15N values of organic matter (OM) due to pre-analysis acid treatment methods. We report here, for the first time, the results of a pre-analysis acid treatment method comparison of measured C/N, d13C and d15N values in bulk OM from a sedimentary sequence of samples to illustrate this bias. Here we show that acid treatment significantly reduces the accuracy (between method biases) and precision (within method bias) of C/N, d13C and d15N values of OM, suggesting a differential response of sample OM between methods and sample horizons, and in some cases inefficient removal of inorganic carbon. We show that different methods can significantly influence environmental interpretation in some of our sample horizons (i.e. interpretation of aquatic vs. terrestrial OM source; C3 vs. C4 vegetation). Specifically, there are unpredictable and non-linear differences between methods for C/N values in the range of ~ 1 – 100; d13C values in the range of 0.2 – 6.8 ‰ and; d15Nvalues in the range of 0.3 – 0.7 ‰. Importantly, these ranges are mostly much greater than the instrument precision (defined as the standard deviation of replicate analysis of standard reference materials; for this study, ± 0.5 for C/N values, ± 0.1 ‰ for d13C values and; ± 0.1 ‰ for d15N). The accuracy and precision of measured C/N, d13C and d15N values of bulk OM is not just dependent upon environmental variability, but on acid pre-treatment, residual inorganic carbon and organic matter state and composition. Collectively, this makes the correlation between samples prepared in different ways, including those from down core reconstructions, highly questionable.

Keywords: C/N ratios, δ13C, δ15N, organic matter; pre-analysis acid treatment methods, environmental interpretation, palaeoclimate.

Common models for modern calcite precipitation in and around caves, soils, springs and streams involve CO2 supplied by thick, high pCO2 biogenic soils which were probably thin or non-existent before vascular plants. Indeed plant-influenced chemical weathering might have caused accelerated terrestrial carbonate production from the Devonian onwards. However terrestrial carbonates have also been documented from the Archaean, Proterozoic, Cambrian, Ordovician and Silurian. Mechanisms which could have caused non-marine carbonates to precipitate without organic-rich soils are described, and some geological events likely to have influenced non-marine carbonate precipitation up to the origin of vascular plants are highlighted. As organisms have evolved, so have the petrographic characteristics of non-marine carbonates; some examples of this are also given here .

На основании палеокарпологических находок в верхнеплиоценовых - нижнеплейстоценовых диатомовых отложениях юго-восточной Армении приводятся описания двух видов ясеня: Fraxinus excelsior L. и F. oxycarpa Willd. Палеогеографический анализ этих видов позволил нам заключить, что в исследуемое время в бассейне реки Воротан климат был более влажным и сравнительно теплым.

Based on palcocarpological findings in upper Pliocene - lower Pleistocene diatom deposits in south-eastern Armenia two species of ash, Fraxinus excelsior L. and F. oxycarpa Willd, are described. Paleogeographical analysis of these species has allowed us to conclude that in the studied period the climate of Vorotan basin was warm and more humid.

In 2009, the GIA dug a trench alongside the Archaic to Roman temple sanctuary of Juno at Tratturo Canio in the ager of Setia in the Pontine plain (Lazio, Italy), in order to investigate the older Bronze and Iron Age remains that had been reported in Italian probing excavations in the mid-1980s. The trench, up to 2 m deep, yielded a wealth of stratigraphic and environmental data as well as much pottery and bone from a Middle Bronze Age habitation layer. This article describes the work, the finds, and the phased geoarchaeological interpretations and reconstructions that were based on the sedimontology and environmental samples. The work is part of the Hidden Landscapes project which aims to show that there is a well-preserved protohistoric landscape buried beneath the Pontine plain.

We present an ultrastructure-based revision (using light and electron microscopy) of the type species of the genus Cocconeis, C. scutellum var. scutellum, and four often-mentioned but poorly described, morphologically related varieties: C. scutellum var. baldjikiana, C. scutellum var. clinoraphis, C. scutellum var. parva, C. scutellum var. posidoniae. In addition, we introduce three new taxa, C. scutellum var. gorensis var. nov., C. scutellum var. posidoniae f. decussata f. nov. and C. scutellum var. sullivanensis var. nov. The taxonomic relationships between these varieties and the remaining validly described C. scutellum varieties are analyzed on the basis of their ultrastructural differences. We also provide additional information on the geographical distribution of all analyzed C. scutellum taxa.

Ultrastructural observations of one previously misidentified freshwater species of a Cocconeis (Bacillariophyceae) from the Crozet Archipelago, Indian Sector of the Southern Ocean, are presented. Cocconeis crozetensis sp. nov. possesses small valves (apical axis: 10–13μm; transapical axis: 6.7–8.4μm). The main frustule features that distinguish the proposed new species are: (1) the sternum valve (SV) areolae with an external vola and the internal vela, (2) the submarginal area of the raphe-sternum valve, and (3) the mor- phology of valvocopula and fimbriae of the SV. Possible morphological relationships with several other small Cocconeis, such as C. neodiminuta, C. neothumensis, C. placentula var. pseudolineata and C. pseudothumensis, as well as its morphological similarities with placentuloid Cocconeis are discussed. Reliable identification of C. crozetensis sp. nov. under light microscopy can prove diffi- cult for less-experienced diatomologists and ecologists, and the use of electron microscopy proves to be unavoidable for its correct identification.

Flux of siliceous plankton and taxonomic composition of diatom and silicoflagellate assemblages were determined from sediment trap samples collected in coastal upwelling-influenced waters off northern Chile (30°S, CH site) under ‘‘normal’’ or non-El Nino (1993–94) and El Nino conditions (1997–98). In addition, concentration of biogenic opal and siliceous plankton, and diatom and silicoflagellate assemblages preserved in surface sediments are provided for a wide area between 27° and 43°S off Chile. Regardless of the year, winter upwelling determines the maximum production pattern of siliceous microorganisms, with diatoms numerically dominating the biogenic opal flux. During the El Nino year the export is markedly lower: on an annual basis, total mass flux diminished by 60%, and diatom and silicoflagellate export by 75%. Major components of the diatom flora maintain much of their regular seasonal cycle of flux maxima and minima during both sampling periods. Neritic resting spores (RS) of Chaetoceros dominate the diatom flux, mirroring the influence of coastal-upwelled waters at the CH trap site. Occurrence of pelagic diatoms species Fragilariopsis doliolus, members of the Rhizosoleniaceae, Azpeitia spp. and Nitzschia interruptestriata, secondary components of the assemblage, reflects the intermingling of warmer waters of the Subtropical Gyre. Dictyocha messanensis dominates the silicoflagellate association almost year-around, but Distephanus pulchra delivers ca. 60% of its annual production in less than three weeks during the winter peak. The siliceous thanatocoenosis is largely dominated by diatoms, whose assemblage shows significant qualitative and quantitative variations from north to south. Between 27° and 35°S, the dominance of RS Chaetoceros, Thalassionema nitzschioides var. nitzschioides and Skeletonema costatum reflects strong export production associated with occurrence of coastal upwelling. Both highest biogenic opal content and diatom concentration at 351 and 411–431S coincide with highest pigment concentrations along the Chilean coast. Predominance of the diatom species Thalassiosira pacifica and T. poro-irregulata, and higher relative contribution of the silicoflagellate Distephanus speculum at 41°–43°S suggest the influence of more nutrient-rich waters and low sea surface temperatures, probably associated with the Antarctic Circumpolar Water.

A predicted rise in anthropogenic greenhouse gas emissions and associated effects on the Earth's climate system likely imply more frequent and severe weather extremes with alternations in hydroclimatic parameters expected to be most critical for ecosystem functioning, agricultural yield, and human health. Evaluating the return period and amplitude of modern climatic extremes in light of pre-industrial natural changes is, however, limited by generally too short instrumental meteorological observations. Here we introduce and analyze 11,873 annually resolved and absolutely dated ring width measurement series from living and historical fir (Abies alba Mill.) trees sampled across France, Switzerland, Germany, and the Czech Republic, which continuously span the AD 962e2007 period. Even though a dominant climatic driver of European fir growth was not found, ring width extremes were evidently triggered by anomalous variations in Central European AprileJune precipitation. Wet conditions were associated with dynamic low-pressure cells, whereas continental-scale droughts coincided with persistent high-pressure between 35 and 55 N. Documentary evidence independently confirms many of the dendro signals over the past millennium, and further provides insight on causes and consequences of ambient weather conditions related to the reconstructed extremes. A fairly uniform distribution of hydroclimatic extremes throughout the Medieval Climate Anomaly, Little Ice Age and Recent Global Warming may question the common believe that frequency and severity of such events closely relates to climate mean stages. This joint dendro-documentary approach not only allows extreme climate conditions of the industrial era to be placed against the backdrop of natural variations, but also probably helps to constrain climate model simulations over exceptional long timescales.

Leaf and cupule/nut remains belonging to Fagus (beech) have previously been reported from three plant-bearing formations on Iceland, the 15 Ma Selárdalur-Botn Formation, the 13.5 Ma Dufansdalur-Ketilseyri Formation, and the ca. 9-8 Ma SkarWstrfnd-Mó kollsdalur Formation, and have traditionally been assigned to various species. In this paper, we study Fagus leaves and cupules from the Miocene of Iceland based on unpublished and newly collected material and assess their taxonomic position. Leaves from Selárdalur (15 Ma) and Tafla (13.5 Ma) are described as a new species, Fagus friedrichii, on grounds of unique combinations of morphological features such as the large elliptical leaves with densely spaced secondary veins, the attenuate leaf apex, and the consistently craspedodromous venation.

The paper presents results of multidisciplinary studies on environmental archaeology under-taken on complex of prehistoric and early historic settlements located at Złotoria village in northeastern Poland. Relicts of settlements dated to the Stone Age, the Late Bronze Age, the Early Iron Age, the Ro-man Period and the Early Medieval Period have been uncovered at two sites at Złotoria. On both sites analysis including: archaeological research, geoarchaeological, palaeobotanical (i.e. pollen, macrofossils like fruits, seeds, wood and charcoal) and palaeozoological (Cladocera, bone remains from archaeological contexts) was performed. The profile of organic sediments of palaeochannel fillings has been collected and palaeoecological analyses of sediments have been elaborated as well. Both sites have been situated on sandy ground, one of them (site no. 53) on deluvial sediments, and the second (site no. 56) on river terrace and slope of the Narew River valley. The settlement complex has b...

A 144-cm-long core was obtained in Lake Petit (2200 m a.s.l., Mediterranean French Alps) in order to reconstruct past interactions between humans, the environment and the climate over the last five millennia using a multidisciplinary approach involving sedimentological, geochemical and botanical analyses. We show a complex pattern of environmental transformation. From 4800 to 4200 cal. BP, podzol-type soils progressively developed under forest cover. This stable situation was interrupted by a major detrital pulse at 4200 cal. BP that we consider as a tipping point in the environmental history. At this point, pedogenetic processes drastically regressed, leading to the development of moderately weathered soils. More frequent detrital inputs are recorded since 3000 cal. BP (ad 1050) as the human impact significantly increased in the catchment area. We conclude that destabilisation of the environment was triggered by climate and exacerbated by human activities to a stage beyond resilience.

The deep basins of the Baltic Sea are commonly anoxic, and finely laminated diatomaceous sediments have been deposited at intervals throughout the last 8000 yr. The origin and composition of individual laminae in Gotland Deep sediments have often proved difficult to characterise using traditional micropalaeontological and sedimentological studies. Here, we present a scanning electron microscope study in which lamina down to 0.03 mm in thickness with distinct mineralogical or micropalaeontological composition have been identified and described. Depositional laminae sequences in the form of couplets, triplets and quadruplets of diatomaceous and lithogenic laminae are observed with an average thickness of approximately 0.7 mm. Diagenetic Ca-rhodochrosite laminae also occur within these depositional sequences. Examination of the diatom assemblages suggests that these bundles of laminae represent annual deposits, or varves. Varves are relatively uncommon, and typically occur in small intervals of two to five varves, which are interrupted by more diffusely laminated and homogenous sediments. The origin of these more massive sediments probably relates to periodic re-oxygenation of the basin on inter-annual time scales and destruction of varves by bioturbation.

Dating the subsidence history of the North Atlantic Land Bridge (NALB) is crucial for understanding intercontinental disjunctions of northern temperate trees. Traditionally, the NALB has been assumed to have functioned as a corridor for plant migration only during the early Cenozoic, but recent fi ndings of plant fossils and inferences from molecular studies are challenging this view. Here, we report dispersed pollen of Quercus from Late Miocene sediments in Iceland that shows affi nities with extant northern hemispheric white oaks and North American red oaks. Older (15 to 10 Ma) sediments do not contain pollen of Quercus suggesting it arrived after that time. Pollen from the 9 -8 Ma Hr ú tagil locality is indistinguishable from morphotypes common among white and red oaks. In contrast, pollen from the 5.5 Ma Sel á rgil locality has a tectum that is at present confi ned to North American white and red oaks, indicating a second episode of migration to Iceland. These fi ndings suggest that transatlantic migration of temperate plant taxa may not have been limited by vast areas of sea or by cold climates during the Miocene. Furthermore, our results offer a plausible explanation for the remarkably low degree of genetic differentiation between modern disjunct European and North American oaks.

Woody plant performance in a changing global environment has always been at the centre of palaeoenvironmental and long-term climate reconstructions carried out by means of pollen analysis. In Mediterranean regions, Taxus constitutes the highest percentage in past pollen diagrams from cold or cool periods, and therefore it is generally considered a good index to infer climate features from past records. How- ever, a comparison of these inferences with the true current trends in pollen pro- duction has not been attemped until now. This study reports the decline of airborne pollen of Taxus observed in Emilia Romagna, a region of northern Italy, during the period 1990–2007. Phenological observations on four male specimens and microscopic examination of fresh pollen were made in order to check Taxus flowering time and pollen morphology. Airborne pollen was monitored through continuous sampling with a Hirst volumetric sampler. In the 18-year long period of investigation, Taxus pollen production has decreased, while total woody pollen abundance in air has increased. The trend of the Taxus pollen season shows a delay at the beginning, a shortening of the pollen period, and an advance of the end of the pollen season. This was interpreted as a response to climate warming. In partic- ular, Taxus follows the behaviour of winter-flowering plants, and therefore earlier pollination is favoured at low autumn temperatures, while late pollination occurs more often, most likely after warm autumn temperatures.