Search results for "Sediment"
showing 10 items of 1648 documents
Distribution of Albian clastic deposits in the Benguela basin (Angola): evidence of a Benguela palaeocurrent?
2009
Abstract The Albian clastic Tuenza Formation of the Benguela basin (south Angola) is described and its geographic distribution analysed in detail. From these observations, the existence of an Albian “PalaeoBenguela current” is proposed. This would imply that a marine longshore current reworked the sand transported by palaeorivers and settled it northward along the coast of the young Atlantic Ocean (during the Albian). A parallel between Albian clastic deposits and the modern sediments deposited by the Benguela current is drawn, focusing on the striking resemblance between the two currents, i.e. the actual Benguela current and the Albian marine current, and the associated sedimentary bodies.
Holocene hydrological changes in south-western mediterranean as recorded by lake-level fluctuations at lago Preola, a coastal lake in southern Sicily…
2011
This paper presents a high-resolution lake-level record for the Holocene at Lago Preola (Sicily, southern Italy) based on a specific sedimentological approach, with a chronology derived from AMS radiocarbon dates. It gives evidence of three major successive palaeohydrological periods, with (1) a pronounced dryness during the early Holocene until ca 10300 cal BP, (2) a highstand from ca 10300 to 4500 cal BP, and (3) a marked lowstand from 4500 cal BP to present. Large amplitude lake-level fluctuations characterise two transition phases at ca 10300e9000 and 6400e4500 cal BP. Period 2 was interrupted between 8300 and 7000 cal BP by a dry phase that was punctuated to ca 7300 cal BP by the depos…
Establishing a high-resolution surface sediment chronology with multiple dating methods – Testing 137Cs determination with Nurmijärvi clastic-biogeni…
2017
Abstract The uppermost 50 cm of sediments from the 23 m deep lacustrine basin of Nurmijarvi, a lake in south-central Finland, are composed of the clastic-biogenic type of varves. We use multiple dating methods to render a sediment chronology that is as precise and accurate as possible for future paleoenvironmental research on this high-fidelity sedimentary archive. The 250-year-long varve chronology contains a chronological error of ±2%, as estimated based on repeated varve counts. The varve-based chronology was verified with the vertical distribution of 137Cs by comparing variations in the paleomagnetic relative declination of the surface sediments with instrumental observations and a calc…
Measuring magnitude and rate of vertical movements in the offshore Capo Vaticano (W Calabria) using lowstand coastal prisms and wave-built terraces
2012
The magnitude and rate of vertical movements have been measured in the offshore Capo Vaticano (western Calabria) for the Late Pleistocene - Holocene on the basis of the depth of submerged coastal prism and associated wave-built terrace formed during the sea-level lowstand of the Last Glacial Maximum (LGM). Uplifted and submerged terraces have proved to be valuable recorders of vertical motion in many locations around the world (e.g. DICKINSON, 2001; WEBSTER et alii, 2004) as the depth of their tops appear to be controlled by the sea-level. In the eastern Tyrrhenian margins, depending on the hydraulic energy conditions (i.e. waves and wind-induced currents), the average water depth of terrac…
“Inner” and “outer” wedge-top sequences in the Late Miocene Sicilian Foreland Basin System; inferences from the Upper Tortonian – Lower Messinian Ter…
2010
First record of Mesopithecus (Cercopithecidae, Colobinae) from the Miocene of the Iberian Peninsula
2015
We report dental remains of the extinct colobine monkey Mesopithecus from the Turolian (MN13, Late Miocene, ca. 6.23 Ma) locality of Venta del Moro (Valencia, Spain). They include most of the deciduous dentition and the unerupted germs of the first molars of a single infantile individual, as well as two lower left lateral incisors from two additional individuals. On the basis of morphometric comparisons, mainly based on the Ms, these remains are attributed to the Late Miocene species Mesopithecus pentelicus. They represent a significant addition to the knowledge of the deciduous dentition of this taxon, much less well-known than the permanent dentition. Although this genus was widely distri…
Stable isotopic composition of three foraminifera species in ODP Hole 160-963D
2020
Carbon-rich layers exist at both sides of the Mediterranean Sea sedimentary record and are called sapropels and organic rich layers (ORLs), respectively in the eastern and western basins. They have different levels of organic carbon accumulation and seafloor oxygen deprivation. The most recent sapropel and ORL deposition have a different timing, 10.8-6.1 and 14.5-9.0 ka respectively. Here we investigate oxygen isotopic records of three foraminifera species that occupy different habitats within the Sicily Channel water column since ~ 12.0 ka, thus in the sill between the eastern and western Mediterranean basins. These data are ice volume-corrected, to get information on water masses density …
Järvisedimenttien iänmääritys lyijyajoituksella
2013
Radioaktiivisuudella tarkoitetaan epästabiilin ytimen hajoamista toiseksi ytimeksi. Käytännössä ydin voi hajota kolmella perusprosessilla; alfa-, beeta tai gammahajoamisella, joista gammahajoamisessa virittyneen ytimen viritystila purkautuu emittoimalla gammahiukkasen, fotonin, jonka energia vastaa viritystilan tai viritystilojen välistä energiaa. Lyijyn isotoopin 210Pb (puoliintumisaika noin 22 vuotta) gammahajoamiseen perustuvalla lyijyajoituksella voidaan määrittää järvenpohjien sedimenttikerrosten ikä syvyyden funktiona. Sedimentteihin 210Pb kertyy kahdella tavalla: hajoamalla radioaktiivisesti maaperässä olevasta radiumista sekä ilmakehästä suoraan esimerkiksi sateiden välityksellä tai…
Short-term occupations at high elevation during the Middle Paleolithic at Kalavan 2 (Republic of Armenia).
2021
The Armenian highlands encompasses rugged and environmentally diverse landscapes and is characterized by a mosaic of distinct ecological niches and large temperature gradients. Strong seasonal fluctuations in resource availability along topographic gradients likely prompted Pleistocene hominin groups to adapt by adjusting their mobility strategies. However, the role that elevated landscapes played in hunter-gatherer settlement systems during the Late Pleistocene (Middle Palaeolithic [MP]) remains poorly understood. At 1640 m above sea level, the MP site of Kalavan 2 (Armenia) is ideally positioned for testing hypotheses involving elevation-dependent seasonal mobility and subsistence strateg…
Effects of agricultural drainage systems on sediment connectivity in a small Mediterranean lowland catchment
2018
Traditional drainage systems combining man-made channels and subsurface tile drains have been used since Roman times to control water excess in Mediterranean lowland regions, favouring adequate soil water regime for agriculture purposes. However, mechanization of agriculture, abandonment or land use changes lead to a progressive deterioration of these drains in the last decades. The effects of these structures on hydrological and sediment dynamics have been previously analyzed in a small Mediterranean lowland catchment (Can Revull, Mallorca, Spain, 1.4 km2) by establishing an integrated sediment budget with a multi-technique approach. Moreover, the recent advances in morphometric techniques…