Accelerator Mass Spectrometer Radiocarbon Research Articles

Carbon Accumulation and the Possibility of Carbon Losses by Vertical Movement of Dissolved Organic Carbon in Western Siberian Peatlands

We studied the peat stratigraphy of the Mukhrino peatland, which is a typical ombrotrophic bog for the Middle Taiga zone of Western Siberia, to gain insights into its history, hydrology, and carbon fluxes. For the first time in Western Siberia, seven cores were collected from locations that were chosen to represent the typical present-day vegetation types, and this was performed for the dating of the separated dissolved (DOC) and particulate organic carbon (POC) fractions, which were determined using the Accelerator Mass Spectrometer (AMS) radiocarbon (14C) method. The oldest peat was found at the bottoms of an underlying lake (10,053 cal. year BP) and an ancient riverbed (10,989 cal. year BP). For the whole history of the peatland, the average peat accumulation rate was estimated to be 0.067 ± 0.018 cm yr−1 (ranging from 0.013 to 0.332 cm yr−1), and the carbon accumulation rate was 38.56 ± 12.21 g m−2 yr−1 (ranging from 28.46 to 57.91 g m−2 yr−1). There were clear age differences between the separated samples of the DOC and POC. The DOC was older than the POC in the uppermost 150 cm of the peat deposit and younger in the deeper layers. The difference in age increased with depth, reaching 2000–3000 years at the bottom of the peat deposit (depth of 430–530 cm). Following the consideration of a range of factors that could potentially cause the dating discrepancy, we hypothesised that the DOC continuously moves down into the mineral sediment beneath the peat, as an additional carbon flux that results in the mixing of younger and older carbon. On this basis, we estimated the apparent rate of the DOC’s downward movement and the associated rate of carbon loss. The first estimate of the average rate of the DOC’s downward movement in Western Siberia was 0.047 ± 0.019 cm yr−1, causing carbon loss in the range of 28–404 mg m−2 yr−1.

Environmental change inferred from multiple proxies from an 18 cal ka BP sediment record, Lake Barrine, NE Australia

Lake Barrine (17.25°S, 145.64°E), on the Atherton Tablelands in tropical northeast Australia, was formed as a maar lake in the late Pleistocene. The 65 m-deep stratified lake provides a detailed sediment record of climate and environmental change on the Tablelands. We reconstruct hydroclimate and vegetation change over the last ∼18,000 years from a 7.2 m long sediment core at 20-year resolution using multiple paleoenvironmental proxies (μ-XRF elements, δ13CTOC, TOC and C:N ratio). The data series are supported by a chronology based on 22 accelerator mass spectrometer (AMS) radiocarbon dates. The results suggest a distinct period of intense but highly seasonal rainfall coincident with the Antarctic Cold Reversal (14.7–13.0 cal ka BP). This period was followed by a trend into the early Holocene toward wetter, less seasonal conditions that allowed the progressive establishment of tropical forest in the catchment. The catchment was completely covered by closed forest by 7.3 cal ka BP. The inferred precipitation changes at Lake Barrine are consistent with other records on the Tablelands and in phase with the changes in tropical SE Africa, NW Australia and anti-phase with the East Asian summer monsoon region in the Holocene but not before that. This result supports previous conclusions that precipitation variations correlate (in phase or anti-phased) in these regions. This correlation results from a dynamic balance among intertropical convergence zone (ITCZ), the Indian Ocean Dipole (IOD) and El Niño Southern Oscillation (ENSO).

10Be depositional flux variation in the central Indian Ocean during the last 43 ka

The advent of Accelerator Mass Spectrometer (AMS) enhanced the application of meteoric 10Be (half-life of 1.39 Ma) as a tracer for understanding earth surface processes on thousand to million-year time scales. However, for the majority of applications, an adequate understanding of the 10Be depositional flux is a prerequisite. A number of efforts have been made to understand both spatial and temporal variation of 10Be depositional flux. Yet, due to the limited globally distributed dataset and modulation of the 10Be signal by local processes, a significant offset is observed between model-derived and measured deposition rates of 10Be. In this study, an attempt has been made to determine the 10Be depositional flux from a marine sediment core from the central Indian Ocean chronologically constrained with the AMS radiocarbon dating and 10Be concentration measured with AMS. The 10Be depositional flux estimates using weak leaching method are found to be nearly 44% lower compared to the strong leaching method. The calculated 10Be depositional flux during the Holocene varies between 9.63 and 13.01 × 105 atoms/cm2/yr, which is 2-28% lower compared to the modeled depositional flux for the region. The difference observed in 10Be depositional flux could be due to the local processes (such as boundary scavenging, changing rate of sediment deposition at the location) affecting 10Be deposition into the sediment column or offset associated with the model estimations. The changes in 10Be depositional flux and the 10Be/9Be ratio have been reconstructed up to 43 ka. An increase in the 10Be/9Be ratio during 28 to 43 ka is observed due to the lower geomagnetic field intensity during the period. A high-resolution 10Be/9Be ratio reconstruction shows a peak at 41.2 ka, which can be attributed to the Laschamp event.

Chemical characterization and radiocarbon dating of the rock art of Las Charcas caves, Cuba

There has been much debate over the decades amongst Cuban archaeologists about what group or groups may have created the rock art in the karst caves of Cuba. The complexities of Cuba's history made dating rock paintings an attractive method for determining their origins. Samples were collected from three caves in Mayabeque province, collectively referred to as Las Charcas. Chemical analyses were carried out along with plasma–chemical oxidation and accelerator mass spectrometric radiocarbon dating. The paintings in two caves contained bitumen, resulting in anomalously old dates, whilst the other cave's amorphous carbon‐based paintings fit within a pre‐Columbian context.

The paleoecology and extinction of endemic tortoises in the Bahamian Archipelago

No native species of tortoises ( Chelonoidis spp.) live today in the Bahamian (Lucayan) Archipelago (= The Bahamas + The Turks and Caicos Islands), although a number of species inhabited these islands at the first human contact in the late-Holocene. Until their extinction, tortoises were the largest terrestrial herbivores in the island group. We report 16 accelerator mass spectrometer (AMS) radiocarbon (14C) dates determined directly on individual bones of indigenous, extinct tortoises from the six Bahamian islands (Abaco, Eleuthera, Flamingo Cay, Crooked, Middle Caicos, Grand Turk) on five different carbonate banks. These 16 specimens probably represent six or seven species of tortoises, although only one ( Chelonoidis alburyorum on Abaco) has been described thus far. Tortoises seem to have survived on most Bahamian islands for only one or two centuries after initial human settlement, which took place no earlier than AD ~700–1000. The exception is Grand Turk, where we have evidence from the Coralie archeological site that tortoises survived for approximately three centuries after human arrival, based on stratigraphically associated14C dates from both tortoise bones and wood charcoal. The stable isotope values of carbon (σ13C) and nitrogen (σ15N) of dated tortoise fossils show a NW-to-SE trend in the archipelago that may reflect increasing aridity and more consumption of cactus.

Late Holocene climate changes from diatom records in the historical Reservoir Gonggeomji, Korea

The paleoenvironmental history of the artificial Reservoir Gonggeomji in Sangju City, Korea, was reconstructed using fossil diatom analysis of four sediment cores: GG01, 02, 03, and 04. Accelerator mass spectrometer (AMS) radiocarbon dating results suggest that Reservoir Gonggeomji was maintained from ca. 1350 to 150 cal year BP, and the diatom record in core sediment samples revealed well-defined hydrological changes and paleoenvironmental conditions during this period. The fossil diatom assemblages were predominantly benthic freshwater diatoms. The highest diatom concentrations in all cores were in diatom zone II, in which species richness and diversity were also very high. Cymbella, Eunotia, Gomphonema, Gyrosigma, Navicula, and Pinnularia were the dominant genera in all core sediments. The long-term trend in diatom species abundance and species diversity showed a stronger relationship to temperature anomalies in the northern hemisphere during the past 2000 years with changes in precipitation. These diatom changes could have been controlled by natural climate change, despite anthropogenic activities linked to construction of the dyke in the artificial reservoir.

Holocene vertebrates from a dry cave on Eleuthera Island, Commonwealth of The Bahamas

We report a mid- to late-Holocene, non-cultural vertebrate assemblage from Garden Cave (site EL-229), Eleuthera Island, The Bahamas, with 2450 fossils representing 26 species. The chronology is based on accelerator mass spectrometer (AMS) radiocarbon (14C) dates determined directly on individual bones of the hutia ( Geocapromys ingrahami), an extirpated species of rodent that dominates the bone assemblage at Garden Cave. Four AMS 14C dates from our excavation range from 1340 to 1280 cal. BP (surface of the site) to 4860 to 4830 cal. BP with depth. A hutia bone lying on the surface from elsewhere in the cave dated to 450 to 290 cal. BP, which is roughly the time of European and African contact on Eleuthera. Other extirpated species from Garden Cave are tortoise ( Chelonoidis sp.), rock iguana ( Cyclura sp.), skink ( Mabuya sp.), parrot ( Amazona leucocephala), crow ( Corvus nasicus), and southeastern myotis ( Myotis austroriparius). Each of these species may have survived on Eleuthera until sometime after the initial human occupation of the island (~1000 cal. BP), although we have direct AMS 14C dates for only the hutia. During the time of fossil deposition in Garden Cave, sea levels were approaching that of today, yet land areas were considerably larger than now, connecting Eleuthera to New Providence, and potentially to Exuma as well. Such relatively recent connections are important in explaining past and present distributions of terrestrial plants and animals.

Temporal changes of mixed millet and rice agriculture in Neolithic-Bronze Age Central Plain, China: Archaeobotanical evidence from the Zhuzhai site

Mixed millet and rice agriculture is a unique agricultural style of China, and is distributed in a broad band between the Yangtze and Yellow River basin. However, the development of this style during the Neolithic-Bronze Age has not been comprehensively clarified, owing to limited archaeobotanical data and imprecise chronology for most of the regions. Here, the Central Plain, a location where mixed agriculture may have first appeared, was selected as the area for research. Phytolith and macrofossil analyses from the Zhuzhai site, together with the accelerator mass spectrometer (AMS) radiocarbon dating of samples, reveal information about the temporal changes of mixed agriculture as well as the domestication and cultivation of crops in this region. The results indicate that mixed millet and rice agriculture formed in the Central Plain about 8000 years ago. Common millet was the principal crop in the Peiligang and Yangshao periods, with the domestication process beginning in the Peiligang period and continuing up to the Shang period, at which time it was replaced by foxtail millet. Foxtail millet may have gone through a significant degree of domestication by ca. 6000 cal. BC, but its domestication process was still unclear. Rice had appeared since the Peiligang period, but its proportions were always low. Rice assigned to the Peiligang and Yangshao Cultures was the domesticated japonica, and its cultivation was always performed in dry field systems through the Neolithic-Bronze time. Within the subsistence economy, mixed agriculture was a minor component during the Peiligang period, but has been dominant since the Yangshao period.

Determination and Radiocarbon Dating of Marine Mollusc Fossils in Ancient Sea Shelf of Central Java Indonesia

Mollusc phylum is one of the most adaptive animal groups on Earth. They occupy and thrive in incredibly diverse habitats. Their distribution in the fossil record is equally diverse. Indonesia is one of the country with marine mollusc fossil variety, such as in the archaeological site of Sangiran, Patiayam (Ancient Muria Strait) and Grobogan – Central Java. Radiocarbon Dating is the method for dating analysis using 14C. By measuring 14C content, we can estimate how long ago the fossils died. Radiocarbon dating is an extremely useful technique for determining the ages of geological materials (that have some organic-derived carbon in them). Field sampling had found variety of marine mollusc fossils such us 1) Sangiran: Dosinia sp., Telescopium telescopium, Anadara sp., and Dosinia insularum; 2) Patiayam (Ancient Muria Strait): Pseudodon vondenbuschianus, Elongaria orientalis, Conus (Pionoconus) sp., Ampullina bandongensis, Anadara pilula and Filopaludina javanica; 3) Grobogan: Antigona chemnitzii, Cultelus dilatatus, Plotia scabra and Tibia modesta. Mollusc fossils sample was analysed using Accelerator Mass Spectrometer (AMS) radiocarbon system. It is a good method for dating specific samples. The result showed that Sangiran as an ancient deepsea has fossils age 38710 – 31947 years, then Patiayam (Ancient Muria Strait) with fossils age 26248 – 11994. Mollusc fossils from Grobogan was the youngest area has fossils age 25692 – 6479 years.

Climatic or dietary change? Stable isotope analysis of Neolithic–Bronze Age populations from the Upper Ob and Tobol River basins

Dietary changes in the populations inhabiting southwest Siberia and northern Kazakhstan indicate concurrent changes in the economy, at the same time marking the beginnings of East–West interaction across northern Eurasia. The introduction of domestic animal species of Near Eastern origin, such as sheep and goat, dramatically changed the lives of the local population. Past palaeodietary research using stable isotope analysis has mainly focussed on pastoral populations of the Bronze Age period. It is crucial, however, to assess the diets of humans and animals from earlier periods (Neolithic/Chalcolithic) in order to understand the timing and nature of dietary change during the Bronze Age of southwest Siberia and northern Kazakhstan, in particular the possible contribution of environmental change influencing dietary shifts. In this paper, we report the results of stable isotope analysis on 55 human and 45 faunal samples from southwest Siberia (Upper Ob River) and northern Kazakhstan (Tobol River basin), ranging from the Neolithic to the Bronze Age. These data, combined with published human and faunal collagen results from the region as well as new accelerator mass spectrometer (AMS) radiocarbon dating results, indicate little change in animal diet over time, but a notable change in human diet at ca. 2500 cal. BC. The data allow us to determine the time when pastoralism came to the fore, with concomitant economic differences to the local population.

The Age and Origin of Olivella Beads from Oregon’s LSP-1 Rockshelter: The Oldest Marine Shell Beads in the Northern Great Basin

Beads manufactured from marine shells originating along the Pacific Coast have been found at numerous sites in the western United States. Because they were conveyed across substantial distances and widely exchanged during ethnographic times, researchers generally assume that shell beads were also traded prehistorically. By examining the spatial and temporal distribution of beads, researchers have reconstructed prehistoric exchange networks. In this article, we present stable isotope data and accelerator mass spectrometer (AMS) radiocarbon dates for six Callianax (previously Olivella) biplicata beads from the LSP-1 rockshelter in southcentral Oregon. Most of the beads were deposited during the early Holocene during a series of short-term occupations and the shells used to manufacture them were procured along the northern California, Oregon, or Washington coasts.

Microscale radiocarbon dating of paintings

In this paper, radiocarbon dating of paintings using minimal sample sizes has been investigated, in an effort to address the problem of limited access to sample material in paintings. 14C analyses were conducted on signed and dated paintings from two Swiss artists of the twentieth century. The selected paintings dated from the 1930s and 1960s, provided the opportunity to evaluate the dating accuracy on paintings realized before and after 1950 AD when the 14C bomb peak was created, as a result of the nuclear tests conducted in the 1950/1960s. The work focused on the one hand on minimizing the size of the canvas sample required for accelerator mass spectrometer radiocarbon measurement on the gas ion source of the MICADAS and, on the other hand, on testing the possibility of dating the organic binder of the paint. Following careful characterization of the paint composition by X-ray fluorescence spectroscopy, Fourier transformed infrared spectroscopy, and Raman spectroscopy, paints containing no other carbon source than the natural organic binder were identified and dated.

The implication of varying 14C concentrations in carbon samples extracted from Mongolian iron objects of the Mongol period

Accelerator mass spectrometric (AMS) radiocarbon measurements were performed with carbon samples extracted from cast iron and steel artifacts excavated in the 13th to 14th century Karakorum site of the Mongol period. The 14C levels in most specimens were too low to represent the real age of the given artifacts, particularly in cast iron objects, whose 14C concentrations were negligible. This discrepancy was much less pronounced in steel objects, but still quite significant. One notable exception was found, however, in a steel artifact whose radiocarbon date was consistent with its known age. These AMS data suggest that mineral coal was employed primarily for the smelting of cast iron while charcoal served as the major source of fuel for other iron and steelmaking processes. This can explain the significant variation in 14C concentrations for steel products that were fabricated by treating cast iron in a charcoal-fired environment, as confirmed in some of the artifacts examined. This variation may have important archaeological applications in characterizing technological transitions associated with the use of fossil fuels in preindustrial iron industry.

Post-glacial dispersal patterns of Northern pike inferred from an 8800 year old pike (Esox cf. lucius) skull from interior Alaska

The biogeography of freshwater fish species during and after late-Pleistocene glaciations relate to how these species are genetically organized today, and the management of these often disjunct populations. Debate exists concerning the biogeography and routes of dispersal for Northern pike (Esox lucius) after the last glaciation. A hypothesis to account for the relatively low modern genetic diversity for E. lucius is post-glacial radiation from refugia, including lakes from within the un-glaciated portions of eastern Beringia. We report the remains of a Northern pike (E. cf. lucius) skull, including bones, teeth, bone collagen and ancient DNA. The remains were preserved at a depth of between 440 and 446 cm in a 670 cm long core of sediment from Quartz Lake, which initiated at ∼11,200 cal yr BP in interior Alaska. A calibrated accelerator mass spectrometer (AMS) radiocarbon age of the collagen extracted from the preserved bones indicated that the organism was dated to 8820 cal yr BP and is bracketed by AMS values from analyses of terrestrial plant macrofossils, avoiding any potential aquatic reservoir effect that could have influenced the radiocarbon age of the bones. Scanning electron microscope images of the specimen show the hinged tooth anatomy typically of E. lucius. Molar C:N (3.5, 1σ = 0.1) value of the collagen from the specimen indicated well-preserved collagen and its mean stable nitrogen isotope value is consistent with the known predatory feeding ecology of E. lucius. Ancient DNA in the bones showed that the specimen was identical to modern E. lucius. Our record of E. lucius from interior Alaska is consistent with a biogeographic scenario involving rapid dispersal of this species from glacial refugia in the northern hemisphere after the last glaciation.

Holocene paleoclimatic variation in the Schirmacher Oasis, East Antarctica: A mineral magnetic approach

An analysis of remanent magnetism and radiocarbon ages in the dry lacustrine/sediment fills of the Schirmacher Oasis (SO) in East Antarctica was conducted to reconstruct past climatic condition. The statistically run mineral magnetic data on paleontological statistics software package (multivariate cluster analysis) placed on accelerator mass spectrometer radiocarbon chronology of the three sediment sections, trace 6 phases of climatic fluctuation between 13 and 3 ka, (Phases 1, 3 and 5 represent cold periods while Phases 2, 4, and 6 represent warm periods). One short warm period (Phase 2, ca. 12.5 ka) occurred in the late Pleistocene, and two marked warm periods (Phase 4, 11–8.7 ka; Phase 6, 4.4–3 ka) occurred in the Holocene. High magnetic susceptibility (χ), saturation isothermal remanent magnetism (SIRM), and soft isothermal remanent magnetism (soft IRM) values correspond to colder periods and low values reflect comparatively warmer lacustrine phases. Holocene Optima (Phase 4) and Mid Holocene Hypsithermal (Phase 6) are distinguished by decreased values of concentrations dependent parameters. Remanence is preserved in the low-coercive minerals. Heavy metals in the sediments include, Fe, Rb, Zn, Mo, Co, Pb, Mn, Cu, and As in order of decreasing abundance.

Prompt transgression and gradual salinisation of the Black Sea during the early Holocene constrained by amino acid racemization and radiocarbon dating

The restricted environment of the Black Sea is particularly sensitive to climatic and oceanographic fluctuations, owing to its connection with the Mediterranean Sea via the narrow Bosphorus Strait. The exact mechanism and timing of the most recent connection between these water bodies is controversial with debate on the post-glacial history of the Black Sea being dependent on radiocarbon dating for numerical ages. Here we present new 23 accelerator mass spectrometer (AMS) radiocarbon ages on peat and bivalve molluscs, supported by the first amino acid racemization (AAR) dating of bivalve molluscs ( n = 66) in the Black Sea. These data indicate infilling of the Black Sea during the early Holocene from an initial depth 107 m below sea-level, and 72 m below that of the Bosphorus Sill. These data combined with a review of previous radiocarbon ages has enabled a unique perspective on the post-glacial Black Sea. A sea-level curve based on conventional and AMS radiocarbon ages on peat and AMS-based ages on Dreissena sp. shells indicate the water-level in the earlier lake phase continued, until the early Holocene, to be lower than the Bosphorus Sill after the Younger Dryas ended. However, the absence of AMS-dated mollusc ages from the shelves of this basin older than the Younger Dryas is suggestive of sub-aerial exposure of the shelves, and comparatively lower water-levels when the Younger Dryas began. Thus post-glacial outflow from the Black Sea occurred through a lowered or open Bosphorus seaway. Basin-wide radiocarbon ages on peat indicate a prompt increase in water-level from that of the pre-existing and unconnected palaeo-lake during the earliest Holocene (9600–9200 cal a BP). Mass colonisation of the Black Sea by Mediterranean taxa did not occur until salinity had risen sufficiently, a process which took 1000 a or more from the initial transgressive event. This gradual change in salinity contrasts with the prompt transgression which would have taken ∼400 a to occur.

Rapid locking of tectonic magnetic fabrics in weakly deformed mudrocks

The anisotropy of magnetic susceptibility (AMS) has provided important insights into early deformation conditions in compressive settings through characterization of tectonic fabrics in mudrocks that appear otherwise undeformed. The validity of these insights relies on the assumption that tectonic fabrics are rapidly locked shortly after sediment deposition. However, the time lag between deposition and the tectonic overprint has yet to be quantified to verify this assumption. Here we present AMS data from Late Holocene sediments recovered in two cores from Lake Issyk-Kul in the Kyrgyz Tien Shan fold-and-thrust belt. These sediments, in which magnetic fabrics reflect the preferred orientation of phyllosillicates, have typical tectonic magnetic fabrics with varying degrees of tectonic overprint likely controlled by small-scale active faults. The mean orientation of the susceptibility maxima parallels neighbouring active thrust faults and is perpendicular to the geodetically-derived local shortening direction. The age model for one of the studied cores, which is based on 7 calibrated accelerator mass spectrometer radiocarbon dates, indicates that sediments as young as 25 yr record this clear tectonic fabric, which is locked within sediments older than 1180 cal. yr BP. Our demonstration of rapid locking of tectonic fabrics in weakly deformed mudrocks shortly after deposition provides the required validation of their reliability for tectonic studies, and opens new opportunities for providing quantitative insights into the relationship between magnetic ellipsoids, shortening rates, and stress directions in compressive settings.

Ice-stream retreat and ice-shelf history in Marguerite Trough, Antarctic Peninsula: Sedimentological and foraminiferal signatures

Research Article| May 01, 2011 Ice-stream retreat and ice-shelf history in Marguerite Trough, Antarctic Peninsula: Sedimentological and foraminiferal signatures Aoibheann A. Kilfeather; Aoibheann A. Kilfeather † 1Department of Geography, Durham University, Science Site, South Road, Durham, DH1 3LE, UK †E-mail: a.a.kilfeather@durham.ac.uk Search for other works by this author on: GSW Google Scholar Colm Ó Cofaigh; Colm Ó Cofaigh 1Department of Geography, Durham University, Science Site, South Road, Durham, DH1 3LE, UK Search for other works by this author on: GSW Google Scholar Jerry M. Lloyd; Jerry M. Lloyd 1Department of Geography, Durham University, Science Site, South Road, Durham, DH1 3LE, UK Search for other works by this author on: GSW Google Scholar Julian A. Dowdeswell; Julian A. Dowdeswell 2Scott Polar Research Institute, University of Cambridge, Cambridge, CB2 1ER, UK Search for other works by this author on: GSW Google Scholar Sheng Xu; Sheng Xu 3Scottish Universities Environmental Research Centre, Scottish Enterprise Technology Park, East Kilbride, G75 0QF, UK Search for other works by this author on: GSW Google Scholar Steven G. Moreton Steven G. Moreton 4NERC Radiocarbon Facility (Environment), Scottish Enterprise Technology Park, Rankine Avenue, East Kilbride, Glasgow, G75 0QF, UK Search for other works by this author on: GSW Google Scholar Author and Article Information Aoibheann A. Kilfeather † 1Department of Geography, Durham University, Science Site, South Road, Durham, DH1 3LE, UK Colm Ó Cofaigh 1Department of Geography, Durham University, Science Site, South Road, Durham, DH1 3LE, UK Jerry M. Lloyd 1Department of Geography, Durham University, Science Site, South Road, Durham, DH1 3LE, UK Julian A. Dowdeswell 2Scott Polar Research Institute, University of Cambridge, Cambridge, CB2 1ER, UK Sheng Xu 3Scottish Universities Environmental Research Centre, Scottish Enterprise Technology Park, East Kilbride, G75 0QF, UK Steven G. Moreton 4NERC Radiocarbon Facility (Environment), Scottish Enterprise Technology Park, Rankine Avenue, East Kilbride, Glasgow, G75 0QF, UK †E-mail: a.a.kilfeather@durham.ac.uk Publisher: Geological Society of America Received: 25 Feb 2010 Revision Received: 02 Jul 2010 Accepted: 08 Jul 2010 First Online: 08 Mar 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 © 2011 Geological Society of America GSA Bulletin (2011) 123 (5-6): 997–1015. https://doi.org/10.1130/B30282.1 Article history Received: 25 Feb 2010 Revision Received: 02 Jul 2010 Accepted: 08 Jul 2010 First Online: 08 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Aoibheann A. Kilfeather, Colm Ó Cofaigh, Jerry M. Lloyd, Julian A. Dowdeswell, Sheng Xu, Steven G. Moreton; Ice-stream retreat and ice-shelf history in Marguerite Trough, Antarctic Peninsula: Sedimentological and foraminiferal signatures. GSA Bulletin 2011;; 123 (5-6): 997–1015. doi: https://doi.org/10.1130/B30282.1 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract The timing, nature, and causes of grounded ice-sheet retreat following the Last Glacial Maximum (LGM) in Marguerite Trough, west Antarctic Peninsula, and subsequent early Holocene ice-shelf decay, are presented in this paper. We use sedimentological, foraminiferal, geotechnical, and accelerator mass spectrometer (AMS) radiocarbon data from marine cores from the mid-continental shelf, together with previously published AMS dates, to establish a sedimentological and chronological model.Initial ice-sheet retreat through the outer- and mid-shelf sectors of Marguerite Trough was under way by ca. 14 ka B.P., was rapid, and coincided with the sea-level rise of meltwater pulse 1a. An ice shelf formed during this retreat, and fine-grained, laminated muds reflecting meltwater-derived suspension settling and/or tidal pumping were deposited. During this time the ice sheet remained grounded on the inner shelf.Ice-shelf breakup and retreat of the calving front, from ca. 13.2 to 12.5 ka B.P., was slow (∼100 m a−1) across the outer- and mid-shelf, with calving bay conditions remaining for at least 3.5 ka. We interpret this ice-shelf decay to have been driven by an incursion of Weddell Sea Transitional Water onto the shelf. In contrast, grounding-line and ice-shelf retreat in the inner bay occurred from ca. 9.3 ka B.P. and was driven by Circumpolar Warm Deep Water encroaching onto the continental shelf. At this time the mid-shelf was an open-marine environment characterized by hemipelagic deposition. These findings highlight the importance of oceanographic controls in the breakup of Antarctic Peninsula ice shelves during the Holocene. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Changing hillslope and fluvial Holocene sediment dynamics in a Belgian loess catchment

AbstractFloodplain deposition is an essential part of the Holocene sediment dynamics of many catchments and a thorough dating control of these floodplain deposits is therefore essential to understand the driving forces of these sediment dynamics. In this paper we date floodplain and colluvial deposition in the Belgian Dijle catchment using accelerator mass spectrometric radiocarbon and optical stimulated luminescence dating. Relative mass accumulation curves for the Holocene were constructed for three colluvial sites and 12 alluvial sites. A database was constructed of all available radiocarbon ages of the catchment and this database was analysed using relative sediment mass accumulation rates and cumulative probability functions of ages and site‐specific sedimentation curves. Cumulative probability functions of ages were split into different depositional environments representing stable phases and phases of accelerated clastic deposition. The results indicate that there is an important variation between the different dated sites. After an initial stable early and middle Holocene phase with mainly peat growth in the floodplains, clastic sedimentation rates increased from 4000 BC on. This first phase was more pronounced and started somewhat earlier for colluvial deposits then for alluvial deposits. The main part of the Holocene deposits, both in colluvial and alluvial valleys, was deposited during the last 1 ka. The sedimentation pattern of the individual dated sites and the catchment‐wide pattern indicate that land use changes are responsible for the main variations in the Holocene sediment dynamics of this catchment, while the field data do not provide indications for a climatological influence on the sediment dynamics. Copyright © 2011 John Wiley & Sons, Ltd.

Late Pleistocene–Holocene sedimentation surrounding an active seafloor gas-hydrate and cold-seep field on the Northern Gulf of Mexico Slope

A chronostratigraphic framework is constructed from sediments surrounding an active gas-hydrate and cold-seep field, situated on the northern Gulf of Mexico slope within federal offshore lease block Mississippi Canyon 118 (MC118). Accelerator mass spectrometer (AMS) radiocarbon dating, foraminiferal biostratigraphy and nannofossil biostratigraphy are used to constrain the age of sediments from 10 gravity cores collected around the field. X-ray fluorescence (XRF) core scanning is employed to develop continuous down-core elemental profiles, which are used to evaluate biogenic calcium and siliciclastic titanium sediment inputs, and provide a means to correlate sediments across the study area and infer changes in sedimentation through time. Spatial reconstruction of sedimentation surrounding the field indicates the following: (1) a consistent pattern of stratigraphic thinning in close proximity to the field over the past 14,000 yrs and (2), temporal changes in sedimentation that primarily reflect deglacial sea-level rise as well as regional factors such as Mississippi delta lobe switching. These results highlight the variability of sedimentation along a continental slope setting where marine cold seeps and gas hydrate persist, yet do not suggest slope failure or destabilization of the seafloor at this site, at least during the past 14,000 yrs. The evaluation of sedimentation at this location provides an important context for ongoing biogeochemical and geophysical monitoring of the MC118 site, which has been designated the first National Gas Hydrate Seafloor Observatory by the Gulf of Mexico Hydrate Research Consortium.