Search results for " systematic"
showing 10 items of 6683 documents
Growth-increment characteristics and isotopic (delta O-18) temperature record of sub- thermocline Aequipecten opercularis (Mollusca: Bivalvia): evide…
2021
Abstract The shell δ18O of young modern Aequipecten opercularis from the southern North Sea provides an essentially faithful record of seasonal variation in seafloor temperature. In this well-mixed setting, A. opercularis shell δ18O also serves as a proxy for seasonal variation in surface temperature. Individuals from less agitated (e.g. deeper) settings in a warm climate would not be expected to record the full seasonal range in surface temperature because of thermal stratification in summer. Such circumstances have been invoked to explain cool isotopic summer temperatures from early Pliocene A. opercularis of eastern England. Support for a sub-thermocline setting derives from high-amplitu…
Advances of sclerochronology research in the last decade
2021
Over the past decade, sclerochronological research has continued to develop rapidly and is diversifying with respect to methods, taxa, geographic coverage as well as temporal depth. Chonologically aligned environmental records from bivalves, gastropods, coralline algae, corals, and many other periodically formed biogenic hard parts are integrated to build networks across broad spatial domains and trophic levels. Replication and exact dating ensure that environmental signals are fully preserved and facilitate the integration among chronologies as well as observational records of climatic and biological phenomena. The proliferation of chronologies promises to usher in a new era of synthesis t…
Fire–vegetation relationships during the last glacial cycle in a low mountain range (Eifel, Germany)
2021
Abstract Lake sediments can provide useful archives to reconstruct past vegetation changes or fire history. To comprehend how vegetation and fire history have correlated during the last 130,000 years, we used two lake sediment records with known patterns of pollen and botanical macro remains and supplemented this data by analyses of lignin-derived phenols as markers for local vegetation inputs and by benzene polycarboxylic acids (BPCAs) as markers for total fire residue inputs (black carbon, BC). The two sediment archives originated from two maar lakes in the Eifel, which is part of the low mountain ranges in central Germany. A lignin-derived phenol index showed woody angiosperms and gymnos…
How warm? How wet? Hydroclimate reconstruction of the past 7500 years in northern Carpathians, Romania
2017
Abstract As natural and anthropogenic ecosystems are dependent on the local water availability, understanding past changes in hydroclimate represents a priority in research concerning past climate variability. Here, we used testate amoebae (TA) and chironomid analysis on a radiocarbon dated complex of small pond and peat bog sediment profiles from an ombrotrophic bog (Taul Muced, northern Carpathians, Romania) to quantitatively determine major hydrological changes and July air temperature over the last 7500 years. Wet mire surface conditions with a pH between 2.3 and 4.5 were inferred for the periods 4500–2700 and 1300–400 cal yr BP by the occurrence of Archerella flavum , Amphitrema wright…
Multistratigraphic records of the Lower Cretaceous (Valanginian–Cenomanian) Puez key area in N. Italy
2016
Abstract We present a stratigraphic investigation of a Hauterivian to Cenomanian hemipelagic succession from Col Puez, in the Dolomites (Southern Alps, northern Italy). A composite section of seven segments was studied with bio-, magneto-, and chemostratigraphy, which enabled detailed and robust age calibration of the Puez succession. It also revealed the paleoceanographic history and helped identify the important global climatic events of that period. The age of the Lower Cretaceous Puez Formation in the Dolomites is refined as late Hauterivian to early Cenomanian. Ammonoids provide a detailed biostratigraphic subdivision that forms the basis for analyses of the faunal distribution and the…
Subglacial topography and thickness of ice caps on the Argentine Islands
2019
AbstractThis study presents the first subglacial topography and ice thickness models of the largest ice caps of the Argentine Islands, Wilhelm Archipelago, West Antarctica. During this study, ground-penetrating radar was used to map the thickness and inner structure of the ice caps. Digital surface models of all studied islands were created from aerial images obtained with a small-sized unmanned aerial vehicle and used for the construction of subglacial topography models. Ice caps of the Argentine Islands cover ~50% of the land surface of the islands on average. The maximum thickness of only two islands (Galindez and Skua) exceeds 30 m, while the average thickness of all islands is only ~5 …
Paleoecological constraints on reef-coral morphologies in the Tortonian–early Messinian of the Lorca Basin, SE Spain
2004
Abstract Coral reefs represent one of the main carbonate factories that contributed to the control of the stratigraphic architecture of carbonate platforms, which had a widespread development during the late Miocene in the paleo-Mediterranean area. The late Miocene reef complexes of the Lorca Basin in southeastern Spain are composed of five mixed siliciclastic/carbonate units, middle Tortonian to early Messinian in age. The development of coral reefs probably ceased when the first evaporitic event occurred in the basin centre in the early Messinian. This study mainly focuses on the response of reef communities and the modifications of reef organisation to global and regional parameters. At …
Warming or cooling in the Pragian? Sedimentary record and petrophysical logs across the Lochkovian–Pragian boundary in the Spanish Central Pyrenees
2016
Abstract High-resolution petrophysical correlation methods were applied, for the first time, to mid-Paleozoic rocks of the Pyrenees. The methods included magnetic susceptibility measurements (MS), gamma-ray spectrometry (GRS), and alignment of MS logs using the dynamic time-warping (DTW) algorithm. Conodont biostratigraphy provided the basic framework necessary for work with the GRS and MS logs. Despite differences in the sediment patterns and accumulation/erosion rates, the logs from two selected sections in the Spanish Central Pyrenees show a striking symmetry that correlates well with the previously published logs from the Barrandian area in the Czech Republic. The high similarity betwee…
ISOTOPIC TEMPERATURES FROM THE EARLY AND MID-PLIOCENE OF THE US MIDDLE ATLANTIC COASTAL PLAIN, AND THEIR IMPLICATIONS FOR THE CAUSE OF REGIONAL MARIN…
2017
Mean seasonal extreme temperatures on the seafloor calculated from the shell d 18 Oofthescallop Placopecten clintonius from the basal part of the early Pliocene Sunken Meadow Member (Yorktown Formation) in Virginia are very similar to those from the same horizon at the latitude of Cape Hatteras in North Carolina ( ~ 210 km to the south). The lowest and highest temperatures calculated from each shell (using d 18 O seawater ¼þ 0.7 % )givemean values for winter and summer of 8.4 6 1.1 8 C( 6 1 r ) and 18.2 6 0.6 8 CinVirginia,and8.6 6 0.4 8 Cand16.5 6 1.1 8 C in North Carolina (respective median temperatures: 13.3 8 C and 12.6 8 C). Patterns of ontogenetic variation in d 18 O, d 13 C and micro…
Dietary evidence from Central Asian Neanderthals: A combined isotope and plant microremains approach at Chagyrskaya Cave (Altai, Russia).
2021
Neanderthals are known primarily from their habitation of Western Eurasia, but they also populated large expanses of Northern Asia for thousands of years. Owing to a sparse archaeological record, relatively little is known about these eastern Neanderthal populations. Unlike in their western range, there are limited zooarchaeological and paleobotanical studies that inform us about the nature of their subsistence. Here, we perform a combined analysis of carbon and nitrogen stable isotopes on bone collagen and microbotanical remains in dental calculus to reconstruct the diet of eastern Neanderthals at Chagyrskaya Cave in the Altai Mountains of Southern Siberia, Russia. Stable isotopes identify…