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Sample records for holocene coastal dunefields

  1. Testing portable luminescence reader signals against late Pleistocene to modern OSL ages of coastal and desert dunefield sand in Israel

    NASA Astrophysics Data System (ADS)

    Roskin, Joel; Sivan, Dorit; Bookman, Revital; Porat, Naomi; López, Gloria I.

    2017-04-01

    Rapid assessment of luminescence signals of poly-mineral samples by a pulsed-photon portable OSL reader (PPSL) is useful for interpreting sedimentary sections during fieldwork, and can assist with targeted field sampling for later full OSL dating and prioritize laboratory work. This study investigates PPSL signal intensities in order to assess its usefulness in obtaining relative OSL ages from linear regressions created by interpolating newly generated PPSL values of samples with existing OSL ages from two extensive Nilotic-sourced dunefields. Eighteen OSL-dated sand samples from two quartz-dominated sand systems in Israel were studied:(1) the Mediterranean littoral-sourced coastal dunefields that formed since the middle Holocene; and (2) the inland north-western Negev desert dunefield that rapidly formed between the Last Glacial Maximum and the Holocene. Samples from three coastal dune profiles were also measured. Results show that the PPSL signals differ by several orders of magnitude between modern and late Pleistocene sediments. The coastal and desert sand have different OSL age - PPSL signal ratios. Coastal sand show better correlations between PPSL values and OSL ages. However, using regression curves for each dunefield to interpolate ages is less useful than expected as samples with different ages exhibit similar PPSL signals. The coastal dune profiles yielded low luminescence signal values depicting a modern profile chronology. This study demonstrates that a rapid assessment of the relative OSL ages across different and extensive dunefields is useful and may be achieved. However, the OSL ages obtained by linear regression are only a very rough age estimate. The reasons for not obtaining more reliable ages need to be better understood, as several variables can affect the PPSL signal such as mineral provenance, intrinsic grain properties, micro-dosimetry and moisture content.

  2. Late Holocene dune mobilization in the Horqin dunefield of northern China

    NASA Astrophysics Data System (ADS)

    Yang, LinHai; Wang, Tao; Long, Hao; He, Zhong

    2017-05-01

    The late Holocene environmental change and its relationship with climate and human activities in the Horqin dunefield of northern China are poorly understood. In the current study, we presented a new reconstruction of late Holocene dune mobilization in the Horqin dunefield based on 68 quartz OSL ages from 25 dune sections and interpretations of historical documents. These sections were selected from a variety of different geomorphological units across the studied region. The results show that at least four phases of dune mobilization were distinguished during the last 2000 years in Horqin dunefield, corresponding to ∼400-700 CE, ∼1200 CE, ∼1800 CE and after 1900 CE, respectively. By comparison with other well-dated paleoclimate records and analysis on human activity records, we infer that the cold-arid climate caused the dune mobilization around 400-700 CE; dune mobilization around 1200 CE can be attributed to the combinative impacts of cold climate and extensive human activities; increasing human activities play a dominate role in the latest two phases of dune mobilization at around 1800 CE and after 1900 CE, even though the climate warming and drying in 20th century may also contribute to the last phase of dune mobilization.

  3. Landscape metrics of coastal dunefields from LiDAR and hyper-spectral remote sensing

    NASA Astrophysics Data System (ADS)

    Zhang, L.; Baas, A. C.

    2010-12-01

    This paper presents an upscaling study extracting landscape metrics of coastal dunefields, calculated from local topography and vegetation-type abundance, from high-resolution LiDAR and collocated hyper-spectral remote-sensing imagery, at coastal sites in Wales, UK. The hyper-spectral data (Eagle & Hawk instruments on NERC’s ARSF aircraft in 2009) are analysed in combination with spectrometer ground-truthing to determine relative within-pixel (down-scaled) abundance maps of different vegetation types, using a novel method that combines linear spectral mixture modelling with a maximum likelihood classification. The resulting landscape metrics are the same state variables that have been used for classifying simulated dunefield landscapes in the DECAL model and for tracking the evolution of the ecogeomorphology in a 3D state space. The landscape metrics of the dunefields can now be plotted in the same space on the same ordinates to establish a direct and quantitative comparison beween simulated and real-world landscapes. For the Kenfig Dunefield in Wales, LiDAR and hyperspectral analysis has also been accomplished on archived (1997) data to investigate the changes in metrics over a 12-year period.

  4. Late Holocene dune mobilizations in the northwestern Negev dunefield, Israel: A response to combined anthropogenic activity and short-term intensified windiness

    NASA Astrophysics Data System (ADS)

    Roskin, Joel; Katra, Itzhak; Blumberg, Dan G.

    2013-04-01

    The study of the effects of past climates on ancient cultures is usually based on geologic records pertaining to rainfall and temperature fluctuations and shifts. This study proposes a paradigm of anthropogenic activity and windiness fluctuations to explain aeolian sedimentation and dune mobilization in the northwestern (NW) Negev Desert dunefield (Israel). The proposed paradigm contributes a different approach to estimating the effect of climate changes on the unprecedented agricultural and urban settlement expansion during the late Roman to Early Islamic period in the northern and central Negev Desert. This study builds upon the late Holocene cluster of luminescence ages of Roskin et al. (Age, origin and climatic controls on vegetated linear dunes in the northwestern Negev Desert (Israel), Quaternary Science Reviews 30 (2011), 1649-1674) coupled with analysis of archaeological finds and historical texts. We suggest that whereas the NW Negev dunefield was generally stable during the Holocene, intermittent dune mobilization during the late Holocene, at ~1.8 ka and mostly 1.4-1.1 ka (~600-900 CE), are linked to periods of human occupation. The idea that the last glacial dune encroachments alone that formed the NW Negev dunefield is connected to cold-event windy climates that may have intensified East Mediterranean cyclonic winter storms, cannot explain the late Holocene dune mobilizations. We conceptually model a connection between late Holocene dune mobilization, widespread anthropogenic occupation and activity, and windiness. We maintain that historic grazing and uprooting shrubs for fuel in the past by nomads and sedentary populations led to decimation of dune stabilizers, biogenic soil crusts and vegetation, causing dune erodibility and low-grade activity. Short-term events of amplified wind power in conjunction with periods of augmented anthropogenic activity that triggered major events of dune mobilization (elongation) and accretion have been preserved in the

  5. Early Islamic inter-settlement agroecosystems in coastal sand, Yavneh dunefield, eastern Mediterranean coast, Israel

    NASA Astrophysics Data System (ADS)

    Roskin, Joel; Taxel, Itamar

    2017-04-01

    This study reveals an attempt to condition agriculture in coastal aeolian sand holding a high water table. Twenty-six small sites, clustering in topographic lows of the Yavneh dunefield, southern Israeli coastal plain, yield surficial Early Islamic finds, and eroded 1-2 m high berms built of grey sand partially covered by parabolic and transverse dunes. Small winter ponds develop by some of the sites. A clay loam 2.5 m beneath the surface retains the water table at a depth of 2.2 m. Between the berms, a 10-50 cm thick grey sand unit dating by OSL to 0.9 ka (11th-12th century AD) underlays a loose aeolian sand cover and overlays sand whose upper parts date to 1.1 ka (9th-10th century AD). The grey unit displays slightly improved fertility (phosphate, potassium, nitrogen and calcium carbonate) in relation to the underlying sand suggesting an anthropogenic enrichment of ash and refuse. Particle size is similar to the sand. Organic carbon and magnetic susceptibility values (0-5 SI) values are quite low (0.4-0.8%) for both units. The artifact assemblage is mixed and comprised of small (<10 cm) pottery sherds, ceramic roof tiles, glass, marble and granite fragments, mosaic tesserae, pottery production waste, iron slag, animal bones, seashells, and coins dated between the 8th and 10th century. The artifacts pre-date the OSL age of the underlying grey sand. The pottery shares many characteristics with the rich ceramic assemblage of nearby inland Yavneh. The establishment of the sites may have been executed by the inhabitants of either Yavneh (or another major inland settlement) or the seashore Muslim military stronghold of Yavneh-Yam (Taxel, 2013). The density of the sites is remarkable compared with the paucity of Byzantine sites in the same region, indicating a distinct spatial pattern that served a specific purpose. The lack of buried artifacts and structures suggests that the sites did not serve for permanent/intensive occupation. The widespread utilization of the rich

  6. The Impact of Urbanization on the Regional Aeolian Dynamics of an Arid Coastal Dunefield

    NASA Astrophysics Data System (ADS)

    Smith, Alexander; Jackson, Derek; Cooper, Andrew

    2016-04-01

    The anthropogenic impact on the geomorphology of many landscapes are inextricably connected but are often neglected due to the difficulty in making a direct link between the quasi natural and human processes that impact the environment. This research focuses on the Maspalomas dunefield, located on the southern coast of Gran Canaria, in the Canary Island Archipelago. The tourism industry in Maspalomas has led to intensive urbanization since the early 1960's over an elevated alluvial terrace that extends into the dunefield. Urbanization has had a substantial impact on both the regional airflow conditions and the geomorphological development of this transverse dune system. As a result airflow and sediment has been redirected in response to the large scale construction efforts. In situ data was collected during field campaigns using high resolution three-dimensional anemometry to identify the various modifications within the dunefield relative to incipient regional airflow conditions. The goal is to analyse the flow conditions near the urbanized terrace in relation to areas that are located away from the influence of the buildings and to verify numerical modelling results. Computational Fluid Dynamics (CFD) modelling is used in order to expand the areal extent of analysis by providing an understanding of relevant flow dynamics (e.g. flow velocity, directionality, turbulence, shear stresses, etc.) at the mesoscale. An integrative three dimensional model for CFD simulations was created to address the impact of both the urban area (i.e. hotels, commercial centers, and residential communities) as well as the dune terrain on regional flow conditions. Early modelling results show that there is significant flow modification around the urban terrace with streamline compression, acceleration, and deflection of flow on the windward side of the development. Consequently downwind of the terrace there is an area of highly turbulent flow conditions and well developed separation and

  7. Characterization of the Soil Hydromorphic Conditions in a Paludified Dunefield during the Mid-Holocene Hemlock Decline near Québec City, Québec

    NASA Astrophysics Data System (ADS)

    Bhiry, Najat; Filion, Louise

    1996-11-01

    The mid-Holocene eastern hemlock [ Tsuga canadensisL. (Carr.)] decline has been recently attributed to the activity of insect defoliators. N. Bihiry and L. Filion, Quaternary Research45,312-320 (1996). In this study, soil hydromorphic conditions were investigated for the period 6800-3200 yr B.P. using micromorphological data from a peat section from a swale in a paludified dunefield in southern Québec. After a short period of plant colonization in shallow pools between 6800 and 6400 yr B.P., mesic conditions predominated in the interdune before the decline (6400-4900 yr B.P.), as evidenced by strong bioturbation and abundance of excrements from the soil fauna. During the decline, a shift from mesic to wet conditions occurred (4900-4100 yr B.P.), although xeric to mesic conditions persisted on dune ridges until at least 4200 yr B.P. Wetness culminated when beaver occupied the site (4100-3750 yr B.P.). Hemlock needles with chewing damage typical of hemlock looper ( Lambdina fiscellaria) feeding were identified at levels dated 4900, 4600, and 4200 yr B.P., respectively, implying that the hemlock decline was associated with at least three defoliation events. The ca. 400-yr interval between these events likely represents the time required for this late-sucessional tree species to recover.

  8. Holocene coastal paleoenvironmental record, Bay of Brest

    NASA Astrophysics Data System (ADS)

    Fernane, Assia; Gandouin, Emmanuel; Goslin, Jérôme; Penaud, Aurélie; Van Vliet lanoë, Brigitte

    2013-04-01

    Coastal areas are sensitive environments regarding the risk of submersion and the impact on biodiversity induced by salinity changes. These areas thus provide good palaeocecological archives to monitor palaeo sea level changes and the associated adaptation of different biological communities. The north-western coast of France has poorly been investigated regarding its Holocene palaeoecological signatures (Morzadec-Kerfourn, 1974; Naughton et al., 2007). Chironomids have been recognized to be an efficient tool for palaeoclimate and palaeosalinity reconstructions in lakes (Brooks, 2006), and more recently in river floodplains (Gandouin et al, 2006). In this study, environmental changes related to both climate processes and human disturbances, were reconstructed over the last 5000 years, based on pollen and chironomid assemblages from two coastal cores retrieved at Pors Milin (Brittany, NW France). The sedimentary sequences consist of terrestrial peaty layers interdigited with marine clastic deposits. The study area is composed by a sandy beach, truncating the peat, limited by a high sandy bar, and a back marsh developed at + 4 m NGF. Pollen and chironomid results reveal that anthropogenic factors would mainly control environmental changes that occurred in this sector. The disappearance of many chironomid taxa (inhabitants of main river channel) and the dramatic fall in diversity may have been induced by the development of the Merovingian forest clearance at Pors Milin. Indeed, we suggest that the development of agriculture, the river embankment and the draining of wetlands may explain the chironomid habitat loss and the subsequent fall of biodiversity. This change in faunal assemblages occurred synchronously with a decrease in the "arborean / non arborean" pollen ratio reflecting the land opening of the watershed. Several nitrophilous and anthropogenic pollen taxa reinforce our hypothesis concerning the development of agricultural and livestock farming activities at

  9. Holocene climate change evidence from high-resolution loess/paleosol records and the linkage to fire-climate change-human activities in the Horqin dunefield in northern China

    NASA Astrophysics Data System (ADS)

    Mu, Yan; Qin, Xiaoguang; Zhang, Lei; Xu, Bing

    2016-05-01

    The combination of high-resolution sedimentary paleoclimate proxies of total organic carbon and magnetic susceptibility of a loess/paleosol section with black carbon (BC) records provides us with information about climate change and the linkage of fire-climate change-vegetation-human activities in the Horqin dunefield over the past 11,600 cal yr BP. We found that during 11,600-8000 cal yr BP (the early Holocene), the area was dominated by a dry climate. The vegetation coverage was low, which limited the extent of fire. The Holocene optimum can be placed between 8000 and 3200 cal yr BP, and during this period, anthropogenic fire was a key component of total fire occurrence as the intensity of human activity increased. The development of agricultural activities and the growing population during this period increased the use of fire for cooking food and burning for cultivation and land fertilization purposes. During 2800-2600 cal yr BP, a warm/moister climate prevailed and was associated with a high degree of pedogenesis and vegetation cover density, evident at 2700 cal yr BP. Fires may have contributed to human survival by enabling the cooking of food in the warm and wet climate. In the period since 2000 cal yr BP, fires linked to agriculture may have led to increased biomass burning associated with agricultural activity.

  10. Holocene formation and evolution of coastal dunes ridges, Brittany (France)

    NASA Astrophysics Data System (ADS)

    Van Vliet-Lanoë, Brigitte; Goslin, Jérôme; Hénaff, Alain; Hallégouët, Bernard; Delacourt, Christophe; Le Cornec, Erwan; Meurisse-Fort, Murielle

    2016-07-01

    Holocene coastal dune formation under a continuously rising sea level (SL) is an abnormal response to increasing storm frequency. The aim of this work is to understand the coastal sedimentary budget and the present-day sand starvation, controlled by climate and man. Dating in Brittany shows that Aeolian deposition initiated from ca. 4000 cal BP, with the slowing down of the SL rise. Pre-historical dunes appeared here from ca. 3000 cal BP, without SL regression. After, further building phases recycled the same stock of sands. Historical dunes I developed from ca. 350 AD. Major storms between 900 and 1200 AD resulted in the construction of washover coastal ridges, the Historical dunes II. A part of the sand was evacuated offshore. From ca. 1350 AD, the pre-existing ridges are reworked forming the Historical dunes III, leading to rapid coastal erosion and inland drift. Holocene dunes with a rising SL constitute a temporary anomaly, mostly forced by man, soon erased by storms in Brittany.

  11. Regional flow in the Baltic Shield during Holocene coastal regression

    USGS Publications Warehouse

    Voss, Clifford I.; Andersson, Johan

    1993-01-01

    The occurrence of saline waters in the Baltic Shield in Sweden is consistent with ongoing but incomplete Holocene flushing and depends on the geometry and connectivity of conductive structures at both regional and local scales, and on the surface topography. Numerical simulation of regional variable-density fluid flow during Holocene land-rise and coastal regression shows that the existence of any old saline water, whether derived from submarine recharge in regions below Sweden's highest postglacial coastline or geochemical processes in the crystalline rock, is an indication either of slow fluid movements through the bedrock over long times, or of long travel distances through fracture systems before arriving at measurement points. During the land-rise period, regional flow is not affected by the variable density of fluids in the upper few kilometers of the shield, and the topography of the water table is the only driving force. The spatial distribution of meteoric flushing water and pre-Holocene waters may be complex, with the possibility of relatively fresh water in fracture zones below salty units even at depths of a few kilometers. The domination of the topographic driving force implies that deep saline water is not necessarily stagnant, and significant flow may be expected to occur in well-connected horizons even at depth. Local topography variation and fracture zone location combine to create a complex flow field in which local topographic driving forces extend to considerable depth in some areas, whereas regional topographic forces predominate in others. Thus, a pattern may be difficult to discern in measurements of the regional salinity distribution, although it is clear that the coastal region is the major zone of discharge for deeper pre-Holocene fluids. During the land-rise period, the regional flow field equilibrates with changing climatic conditions and coastal positions, while the distribution of flushing water and older water lags and will

  12. Terrestrial Evidence for Holocene Pluvials in Coastal Southern California

    NASA Astrophysics Data System (ADS)

    Reynolds, L.; Simms, A.; Rockwell, T. K.; Peters, R. B.

    2016-12-01

    In 1861 a series of large storms attributed to a prolonged atmospheric river event impacted the coast of California, inundated large regions of the state for weeks on end, stalled the government, and devastated the economy. A recent report by the USGS, the Arkstorm Report, predicted a similar sized event today could cost the state more than $700 billion in long-term economic losses. The high-resolution sedimentary record from the Santa Barbara Basin indicates 8 flooding events similar to or larger than the 1861 event have occurred in the past 2000 years. However, little terrestrial evidence for these events has been identified to determine coastal impacts or test the completeness of the Santa Barbara Channel record. Here we show evidence from coastal wetlands along the Santa Barbara Channel that alluvial fan progradation events have recurred at least 7 times over the last 7ka. Because most streams in the Transverse ranges flow only during storms, these alluvial fan building events are interpreted to represent large flooding events. We use a chronology derived from over 40 radiocarbon dates from 39 vibracores up to 4m in length, and 7 Geoprobe cores up to 13m in length from Carpinteria Marsh to test whether these alluvial fan progradation events and/or other abrupt stratigraphic changes are synchronous with regionally documented climatic events. We show that a compilation of biological, sedimentological, geochemical, and archeological proxies for flooding, storms, and/or wet climate conditions from sites throughout the southwestern United States demonstrates the difficulty in correlating and interpreting regional Holocene events across variable proxies and geographic regions. Despite this variation, isolating the purely sedimentological proxies (increase in sedimentation rates, increase in grain size, decrease in organic content, etc.) seems to demonstrate a correlation between alluvial fan progradation events in Carpinteria at 0.3-0.9 ka and 3.5 ka and records of

  13. Holocene coastal sea surface temperature changes in the northern South China Sea

    NASA Astrophysics Data System (ADS)

    Zhu, K.; Kong, D.; Wei, G.; Liu, Z.

    2016-12-01

    Holocene sea surface temperature (SST) changes in the northern South China Sea (SCS) coastal region are affected by complex factors. Previous studies have identified a long-term cooling trend, attributed to coastal mixing and intensified East Asian Winter Monsoon (EAWM), yet spatial patterns of coastal cooling along the southern China are still not well established. Here we reconstructed a Holocene Sea Surface Temperature (SST) record, derived from long-chain alkenone unsaturation index - UK'37, in the northern SCS. Our result reveals that a gentle cooling trend dominates the mid-late Holocene. The gradual warming trend occurring during the early Holocene might have resulted from the rising sea level or the rebound of "8.2 ka cold event". Besides, the C37-content also shows an extremely-low level before 8 ka. Later, both alkenone-derived SST and C37-content reach their highest levels during approximately 7-4.5 ka, corresponding to the Holocene Climate Optimum (HCO). Consistent with previous studies, the long-term cooling trend identified in coastal regions, but not offshore ones, presumably indicates intensified EAWM toward present. Further, during the late Holocene, coastal SST changes in the northern SCS show heterogeneous responses to global climatic conditions. In the Mirs Bay, SST was warmer during the Little Ice Age (LIA) than the Medieval Warm Period (WMP) and the current warm period, interpreted as reflecting intensified coastal mixing, due to strengthened East Asian Summer Monsoon (EASM) during warmer periods. However, SST records at other coastal sites, as well as offshore regions, show fluctuations consistent with global/northern hemisphere temperature changes, suggesting that these regions are less influenced by the EASM-induced coastal mixing, probably with the aid of Pearl River freshwater input.

  14. Mars: Morphology of Southern Hemisphere intracrater dunefields

    NASA Technical Reports Server (NTRS)

    Lancaster, N.; Greeley, R.

    1987-01-01

    Viking Orbiter images of intracrater dunefields in the Noachis Terra region were examined in order to study the morphology of these landforms and to assess their relationship to local geological settings. The sizes of the dunefields range from 40 to 3600 sq km and vary directly with crater size. Preliminary studies reveal dunefields of two varieties. The most common type is composed of massed straight to slightly wavy crescentic dunes similar to those described by Breed. Dunefields of this type occupy more than 20% of the area of the crater floor, with the dunefield margins often marked by a large dune wall or rampart. Dune spacing ranges between 0.7 and 1.2 km. The second type of dune accumulation consists of clusters of large, widely spaced straight or curved ridges, which often intersect to create rectilinear patterns. Dunes are typically spaced 1.6 to 4 km apart. Earth terrestrial analogs for these dunes are discussed.

  15. Middle to late Holocene coastal evolution along the south coast of Upolu Island, Samoa

    USGS Publications Warehouse

    Goodwin, I.D.; Grossman, E.E.

    2003-01-01

    Stratigraphic surveys and sedimentological analyses of coastal sediments and reef cores along the south coast of Upolu Island, Samoa, reveal that during the middle Holocene this coast was characterised by barrier spits, open lagoons, and estuaries. These estuarine systems matured during the late Holocene, with progressive sedimentation and inlet closure, leading to the dominance of mangrove swamps in the past 1000 years. Contemporaneous with the transition of open estuaries to mangrove swamps was the aggradation and progradation of coastal plains. The coastal progradation since 700-1000 years BP is best explained by increased sediment availability and reduced incident wave energy at the shore resulting from the shallowing and subsequent cessation of reef crest accretion following the mid-Holocene sea-level highstand ca. ???4500 yr BP. A small relative sea-level (RSL) lowering since 700-1000 years may have contributed to the positive sediment budget. This study highlights the need for island-wide coastal surveys to assess the relative roles of RSL, sediment budgets, and hydrodynamics on coastal evolution and stability. Differences in coastal evolution around Upolu Island may also be influenced by differential tectonic movements associated with late Holocene volcanism, coseismicity, and/ or submarine landslides. ?? 2003 Elsevier B.V. All rights reserved.

  16. Historic and Holocene environmental change in the San Antonio Creek Basin, mid-coastal California

    NASA Astrophysics Data System (ADS)

    Scott Anderson, R.; Ejarque, Ana; Rice, Johnathan; Smith, Susan J.; Lebow, Clayton G.

    2015-03-01

    Using a combination of pollen, non-pollen palynomorphs (NPPs) and charcoal particle stratigraphies from sediment cores from two sites, along with historical records, we reconstructed paleoenvironmental change in mid-coastal California. The San Antonio Creek section contains a discontinuous, Holocene-length record, while Mod Pond includes a continuous late Holocene record. Together the records allow for interpretation of most of the present interglacial. The longer record documents coastal sage scrub and chaparral dominated by woodland elements early in the Holocene to about 9000 yr ago, a potential decline in woodland communities with drying conditions during the middle Holocene to about 4800 yr ago, and an expansion of coastal sage scrub with grassland during the late Holocene. Evidence for climatic fluctuations during the last 1000 yr at Mod Pond is equivocal, suggesting that the Medieval Climate Anomaly-Little Ice Age had modest impact on the Mod Pond environment. However, evidence of significant environmental change associated with cultural transitions in the 18th-19th centuries is stark. Introduction of non-native plants, establishment of cattle and sheep grazing, missionization of the native population, changes in burning practices during the Spanish period and enhanced cropping activities during North American settlement worked together to substantially modify the mid-California coastal landscape in about a century's time.

  17. Reconstruction of Redox Conditions and Productivity in Coastal Waters of the Bothnian Sea during the Holocene

    NASA Astrophysics Data System (ADS)

    Dijkstra, N.; Quintana Krupinski, N. B.; Slomp, C. P.

    2014-12-01

    Hypoxia is a growing problem in coastal waters worldwide, and is a well-known cause of benthic mortality. The semi-enclosed Baltic Sea is currently the world's largest human-induced dead zone. During the early Holocene, it experienced several periods of natural hypoxia following the intrusion of seawater into the previous freshwater lake. Recent studies suggest that at that time, the hypoxia expanded north to include the deep basin of the Bothnian Sea. In this study, we assess whether the coastal zone of the Bothnian Sea was also hypoxic during the early Holocene. We analysed a unique sediment record (0 - 30 mbsf) from the Ångermanälven estuary, which was retrieved during the International Ocean Discovery Programme (IODP) Baltic Sea Paleoenvironment Expedition 347 in 2013. Using geochemical proxies and foraminifera abundances, we reconstruct the changes in redox conditions, salinity and productivity in the estuary. Our preliminary results suggest that bottom waters in this coastal basin became anoxic upon the intrusion of brackish seawater in the early Holocene and that the productivity was elevated. The presence of benthic foraminifera in this estuary during the mid-Holocene suggests more saline conditions in the Bothnian Sea than today. Due to isostatic uplift, the estuary likely gradually became more isolated from the Bothnian Sea, which itself became more isolated from the Baltic Sea. Both factors likely explain the subsequent re-oxygenation of bottom waters and gradual refreshening of the estuary as recorded in the sediments. Interestingly, the upper meters of sediment are enriched in minerals that contain iron, phosphorus and manganese. We postulate that the refreshening of the estuary triggered the formation of these minerals, thereby increasing the phosphorus retention in these sediments and further reducing primary productivity. This enhanced retention linked to refreshening may contribute to the current oligotrophic conditions in the Bothnian Sea.

  18. A new GIS approach for reconstructing and mapping dynamic late Holocene coastal plain palaeogeography

    NASA Astrophysics Data System (ADS)

    Pierik, H. J.; Cohen, K. M.; Stouthamer, E.

    2016-10-01

    The geomorphological development of Holocene coastal plains around the world has been studied since the beginning of the twentieth century from various disciplines, resulting in large amounts of data. However, the overwhelming quantities and heterogeneous nature of this data have caused the divided knowledge to remain inconsistent and fragmented. To keep improving the understanding of coastal plain geomorphology and geology, cataloguing of data and integration of knowledge are essential. In this paper we present a GIS that incorporates the accumulated data of the Netherlands' coastal plain and functions as a storage and integration tool for coastal plain mapped data. The GIS stores redigitised architectural elements (beach barriers, tidal channels, intertidal flats, supratidal flats, and coastal fresh water peat) from earlier mappings in separate map layers. A coupled catalogue-style database stores the dating information of these elements, besides references to source studies and annotations regarding changed insights. Using scripts, the system automatically establishes palaeogeographical maps for any chosen moment, combining the above mapping and dating information. In our approach, we strip the information to architectural element level, and we separate mapping from dating information, serving the automatic generation of time slice maps. It enables a workflow in which the maker can iteratively regenerate maps, which speeds up fine-tuning and thus the quality of palaeogeographical reconstruction. The GIS currently covers the late Holocene coastal plain development of the Netherlands. This period witnessed widespread renewed flooding along the southern North Sea coast, coinciding with large-scale reclamation and human occupation. Our GIS method is generic and can be expanded and adapted to allow faster integrated processing of growing amounts of data for many coastal areas and other large urbanising lowlands around the world. It allows maintaining actual data

  19. The archaeological record and mid-Holocene marginal coastal palaeoenvironments around Liverpool Bay

    NASA Astrophysics Data System (ADS)

    Huddart, David; Gonzalez, Silvia; Roberts, Gordon

    1999-10-01

    The available published and unpublished archaeological record (human and animal bones, artefacts, footprints) is collated and reviewed in relation to the stratigraphic succession and palaeoecology for Mid-Holocene marginal coastal environments around Liverpool Bay. Two stratigraphic levels with human and animal footprint trails are described from Formby Point and whilst the upper level was formed between c 4000-3600 years B.P. (during the later Neolithic-early Bronze Age), the lower level is older. The animal and bone assemblages and the archaeological artefact evidence for this coastal region are reviewed. The implications of these finds for inter-tidal zone archaeology for this region are assessed but it appears that there is no evidence for major Mesolithic coastal human or animal activity, except for the North Wales coast, although there are major concentrations of Neolithic animal, human and artefacts remains. During the Bronze to Iron Age dunes were present and probably grazed. Metal artefacts have been located from several sites but there is a lack of associated pottery evidence throughout the Holocene. This may mean that settlements were inland and coastal areas were only visited for grazing, hunting and fishing.

  20. Holocene coastal dune fields used as indicators of net littoral transport: West Coast, USA

    USGS Publications Warehouse

    Peterson, C.D.; Stock, E.; Hart, R.; Percy, D.; Hostetler, S.W.; Knott, J.R.

    2010-01-01

    Between Point Grenville, Washington, and Point Conception, California (1500 km distance) 21 dune fields record longshore transport in 20 littoral cells during the late Holocene. The direction of predominant littoral transport is established by relative positions of dune fields (north, central, or south) in 17 representative littoral cells. Dune field position is north of cell midpoints in northernmost Oregon and Washington, but is south of cell midpoints in southern Oregon and California. Downdrift sand trapping occurs at significant changes in shoreline angle and/or at bounding headlands that project at least 2.5 km seaward from the general coastal trend. Sand bypassing occurs around small headlands of less than 0.5 km in projection distance. A northward shift of the winter low-pressure center in the northeast Pacific Ocean is modeled from 11 ka to 0 ka. Nearshore current forcing in southern Oregon and northern California switched from northward in earliest Holocene time to southward in late Holocene time. The late Holocene (5-0 ka) is generally characterized by net northward littoral drift in northernmost Oregon and Washington and by net southward littoral drift in southernmost Oregon and California. A regional divergence of net transport direction in central Oregon, i.e. no net drift, is consistent with modeled wind and wave forcing at the present time (0 ka). ?? 2009 Elsevier B.V.

  1. Late Holocene sedimentation in a high Arctic coastal setting: Simpson Lagoon and Colville Delta, Alaska

    NASA Astrophysics Data System (ADS)

    Hanna, Andrea J. M.; Allison, Mead A.; Bianchi, Thomas S.; Marcantonio, Franco; Goff, John A.

    2014-02-01

    Arctic coastal environments near major river outfalls, like Simpson Lagoon, Alaska and the adjacent Colville River Delta, potentially contain high-resolution sediment records useful in elucidating late Holocene Arctic sediment transport pathways and coupled terrestrial-ocean evidence of paleoclimate variability. This study utilizes a multi-tracer geochronology approach (137Cs, 239,240Pu, and 14C) tailored for high-latitude environments to determine the age models for cores collected from Simpson Lagoon, and to date seismic boundaries in shallow acoustic reflection data (CHIRP) to examine late Holocene infill patterns. Modern (~100 y) sediment accumulation rates range from <0.02 to 0.46±0.04 cm y-1, with a primary depocenter in western Simpson Lagoon adjacent to the Colville Delta and a secondary depocenter in eastern Simpson Lagoon. CHIRP reflectors, age-constrained by 14C analysis, reveal rapid late Holocene (0-3500 y BP) transgression consistent with high modern shoreline retreat rates. The western depocenter contains >5 m of late Holocene interbedded sediments, likely derived primarily from the Colville River, with onset of accumulation occurring prior to ~3500 y BP. A paleo-high in central Simpson Lagoon, separating the two depocenters, was subaerially exposed prior to ~600 y BP. The millimeters-per-year sedimentation rates across the lagoon, coupled with the undisturbed, interbedded sediment record, indicate that these settings hold great potential to develop new Arctic paleoenvironmental records.

  2. Holocene coastal dune fields used as indicators of net littoral transport: West Coast, USA

    NASA Astrophysics Data System (ADS)

    Peterson, Curt D.; Stock, Errol; Hart, Roger; Percy, David; Hostetler, Steve W.; Knott, Jeffrey R.

    2010-03-01

    Between Point Grenville, Washington, and Point Conception, California (1500 km distance) 21 dune fields record longshore transport in 20 littoral cells during the late Holocene. The direction of predominant littoral transport is established by relative positions of dune fields (north, central, or south) in 17 representative littoral cells. Dune field position is north of cell midpoints in northernmost Oregon and Washington, but is south of cell midpoints in southern Oregon and California. Downdrift sand trapping occurs at significant changes in shoreline angle and/or at bounding headlands that project at least 2.5 km seaward from the general coastal trend. Sand bypassing occurs around small headlands of less than 0.5 km in projection distance. A northward shift of the winter low-pressure center in the northeast Pacific Ocean is modeled from 11 ka to 0 ka. Nearshore current forcing in southern Oregon and northern California switched from northward in earliest Holocene time to southward in late Holocene time. The late Holocene (5-0 ka) is generally characterized by net northward littoral drift in northernmost Oregon and Washington and by net southward littoral drift in southernmost Oregon and California. A regional divergence of net transport direction in central Oregon, i.e. no net drift, is consistent with modeled wind and wave forcing at the present time (0 ka).

  3. Holocene melt-water variations recorded in Antarctic coastal marine benthic assemblages

    SciTech Connect

    Berkman, P.A.

    1992-03-01

    Climate changes can influence the input of meltwater from the polar ice sheets. In Antarctica, signatures of meltwater input during the Holocene may be recorded in the benthic fossils which exist at similar altitudes above sea level in emerged beaches around the continent Interpreting the fossils as meltwater proxy records would be enhanced by understanding the modern ecology of the species in adjacent marine environments. Characteristics of an extant scallop assemblage in West McMurdo Sound, Antarctica, have been evaluated across a summer meltwater gradient to provide examples of meltwater records that may be contained in proximal scallop fossils. Integrating environmental proxies from coastal benthic assemblages around Antarctica, over ecological and geological time scales, is a necessary step in evaluating the marginal responses of the ice sheets to climate changes during the Holocene.

  4. Long-Term Resilience of Late Holocene Coastal Subsistence System in Southeastern South America

    PubMed Central

    Colonese, André Carlo; Collins, Matthew; Lucquin, Alexandre; Eustace, Michael; Hancock, Y.; de Almeida Rocha Ponzoni, Raquel; Mora, Alice; Smith, Colin; DeBlasis, Paulo; Figuti, Levy; Wesolowski, Veronica; Plens, Claudia Regina; Eggers, Sabine; de Farias, Deisi Scunderlick Eloy; Gledhill, Andy; Craig, Oliver Edward

    2014-01-01

    Isotopic and molecular analysis on human, fauna and pottery remains can provide valuable new insights into the diets and subsistence practices of prehistoric populations. These are crucial to elucidate the resilience of social-ecological systems to cultural and environmental change. Bulk collagen carbon and nitrogen isotopic analysis of 82 human individuals from mid to late Holocene Brazilian archaeological sites (∼6,700 to ∼1,000 cal BP) reveal an adequate protein incorporation and, on the coast, the continuation in subsistence strategies based on the exploitation of aquatic resources despite the introduction of pottery and domesticated plant foods. These results are supported by carbon isotope analysis of single amino acid extracted from bone collagen. Chemical and isotopic analysis also shows that pottery technology was used to process marine foods and therefore assimilated into the existing subsistence strategy. Our multidisciplinary results demonstrate the resilient character of the coastal economy to cultural change during the late Holocene in southern Brazil. PMID:24718458

  5. Long-term resilience of late holocene coastal subsistence system in Southeastern South america.

    PubMed

    Colonese, André Carlo; Collins, Matthew; Lucquin, Alexandre; Eustace, Michael; Hancock, Y; de Almeida Rocha Ponzoni, Raquel; Mora, Alice; Smith, Colin; Deblasis, Paulo; Figuti, Levy; Wesolowski, Veronica; Plens, Claudia Regina; Eggers, Sabine; de Farias, Deisi Scunderlick Eloy; Gledhill, Andy; Craig, Oliver Edward

    2014-01-01

    Isotopic and molecular analysis on human, fauna and pottery remains can provide valuable new insights into the diets and subsistence practices of prehistoric populations. These are crucial to elucidate the resilience of social-ecological systems to cultural and environmental change. Bulk collagen carbon and nitrogen isotopic analysis of 82 human individuals from mid to late Holocene Brazilian archaeological sites (∼6,700 to ∼1,000 cal BP) reveal an adequate protein incorporation and, on the coast, the continuation in subsistence strategies based on the exploitation of aquatic resources despite the introduction of pottery and domesticated plant foods. These results are supported by carbon isotope analysis of single amino acid extracted from bone collagen. Chemical and isotopic analysis also shows that pottery technology was used to process marine foods and therefore assimilated into the existing subsistence strategy. Our multidisciplinary results demonstrate the resilient character of the coastal economy to cultural change during the late Holocene in southern Brazil.

  6. Paleo-modeling of coastal saltwater intrusion during the Holocene: an application to the Netherlands

    NASA Astrophysics Data System (ADS)

    Delsman, J. R.; Hu-a-ng, K. R. M.; Vos, P. C.; de Louw, P. G. B.; Oude Essink, G. H. P.; Stuyfzand, P. J.; Bierkens, M. F. P.

    2014-10-01

    Coastal groundwater reserves often reflect a complex evolution of marine transgressions and regressions, and are only rarely in equilibrium with current boundary conditions. Understanding and managing the present-day distribution and future development of these reserves and their hydrochemical characteristics therefore requires insight into their complex evolution history. In this paper, we construct a paleo-hydrogeological model, together with groundwater age and origin calculations, to simulate, study and evaluate the evolution of groundwater salinity in the coastal area of the Netherlands throughout the last 8.5 kyr of the Holocene. While intended as a conceptual tool, confidence in our model results is warranted by a good correspondence with a hydrochemical characterization of groundwater origin. Throughout the modeled period, coastal groundwater distribution never reached equilibrium with contemporaneous boundary conditions. This result highlights the importance of historically changing boundary conditions in shaping the present-day distribution of groundwater and its chemical composition. As such, it acts as a warning against the common use of a steady-state situation given present-day boundary conditions to initialize groundwater transport modeling in complex coastal aquifers or, more general, against explaining existing groundwater composition patterns from the currently existing flow situation. The importance of historical boundary conditions not only holds true for the effects of the large-scale marine transgression around 5 kyr BC that thoroughly reworked groundwater composition, but also for the more local effects of a temporary gaining river system still recognizable today. Model results further attest to the impact of groundwater density differences on coastal groundwater flow on millennial timescales and highlight their importance in shaping today's groundwater salinity distribution. We found free convection to drive large-scale fingered infiltration

  7. Alimini Lakes Project (PAL). Human-environment interaction during the Holocene in Mediterranean coastal wetlands

    NASA Astrophysics Data System (ADS)

    Balbo, Andrea; Primavera, Milena; Fiorentino, Girolamo; Simone, Oronzo; Caldara, Massimo; Quarta, Gianluca; Calcagnile, Lucio

    2010-05-01

    A diachronical understanding of the co-evolution of people and Mediterranean wetlands requires the combined study of archaeological and palaeoenvironmental records. By focusing on an extended chronology, and relying on the update of known and new archaeological and palaeonvironmental sequences, PAL investigates how the Alimini Lakes disctrict (Apulia, S Italy) has changed over the past 10ka (the Holocene), a period witnessing great climatic environmental and social change. Holocene climate change is amplified in coastal wetlands, greatly affecting hydrology vegetation and people. Likewise, socio-economical changes (e.g. the introduction of agriculture) play a fundamental role in the shaping of wet landscapes. Under the combined action of environmental and human factors, coastal wetlands are prone to rapid and drastic ecological shifts and constitute ideal locations for developing a geoarchaeological approach. The results of the first year of research are presented here and include (1) the visit, description and GPS positioning of previously and newly discovered archaeological areas (cave and open air sites), (2) sampling of two Holocene sedimentary sequences from the Alimini Lakes disctict, (3) the results of the preliminary analyses (including AMS radiocarbon dating) carried out on the samples. The relocation of new and previously found archaeological sites was necessary to overcome some confusions caused by the contrasting published information. Relocated archaeological sites were normalized in a GIS environment. Two main Pleistocene/Holocene palaeoenvironmental sequences were sampled within the Alimini Lakes district: (1) the Frassanito dune reference sequence, obtained from a portion of the coastal dune (up to 10 m high) bordering the trait of the Adriatic coast situated in front of the Alimini lakes, (2) the ALI G 1 core (9m long) sampled on the W shore of Alimini Grande Lake. The multiproxy study of these sedimentary sequences provides a record of Holocene

  8. Sudden, probably coseismic submergence of Holocene trees and grass in coastal Washington State

    USGS Publications Warehouse

    Atwater, B.F.; Yamaguchi, D.K.

    1991-01-01

    Growth-position plant fossils in coastal Washington State imply a suddenness of Holocene submergence that is better explained by coseismic lowering of the land than by decade- or century-long rise of the sea. Growth-position fossils implying sudden submergence include the stems and leaves of salt-marsh grass entombed in tide-flat mud close to 300 yr ago and roughly 1700 and 3100 yr ago. In some places the stems and leaves close to 300 yr old are surrounded by sand left by an extraordinary, landward-directed surge - probably a tsunami from a great thrust earthquake on the Cascadia subduction zone. -from Authors

  9. Holocene environmental conditions in South Georgia - a multi-proxy study on a coastal marine record

    NASA Astrophysics Data System (ADS)

    Berg, Sonja; Jivcov, Sandra; Groten, Sonja; Viehberg, Finn; Rethemeyer, Janet; Melles, Martin

    2014-05-01

    The Holocene environmental history of the sub-Antarctic island of South Georgia so far has been reconstructed from lake sediments, peat records and geomorphological observations. The data available indicate a postglacial ice retreat, which reached the coastal areas around the early Holocene. Climate reconstructions for the Holocene, on the other hand, provide a more complex picture, which may partly result from the influence of local effects. We present preliminary results of a multi-proxy study on a sediment core recovered in early 2013 from a coastal marine inlet (Little Jason Lagoon) in Cumberland West Bay. The results include elemental data (high resolution XRF-scans, total organic carbon (TOC), nitrogen, and sulphur, lipid biomarkers, and macrofossil data. The sediment core comprises a c. 11m long sequence, which contains a complete record of postglacial sedimentation in the inlet. Its base is formed by a diamicton, indicating a former glaciation of the site, which is overlain by well-stratified sediments passing over into more massive muds in the upper past. A radiocarbon age from the organic-rich sediments above the diamicton provides a first estimate of 9700 14C years BP for a minimum age of ice retreat. We use the elemental data to infer changes in clastic input (e.g., K/Ti ratios), productivity (TOC) and water salinity (Cl counts) in the course of the Holocene. While Little Jason Lagoon has a connection to the sea today (sill depth c. 1 m), a decrease in Cl counts downcore points to fresher conditions in the early part of the record. This could be an indicator for changing relative sea level and/or changes in the amounts of freshwater inflow from the catchment. Macroscopic plant remains and lipid biomarkers (n-alkanes, n-fatty acids and sterols) provide information on the terrestrial vegetation in the catchment and its changes through time as well as on the influence of marine conditions in the lagoon. We suggest that the record from Little Jason Lagoon

  10. Proxy records of Holocene storm events in coastal barrier systems: Storm-wave induced markers

    NASA Astrophysics Data System (ADS)

    Goslin, Jérôme; Clemmensen, Lars B.

    2017-10-01

    Extreme storm events in the coastal zone are one of the main forcing agents of short-term coastal system behavior. As such, storms represent a major threat to human activities concentrated along the coasts worldwide. In order to better understand the frequency of extreme events like storms, climate science must rely on longer-time records than the century-scale records of instrumental weather data. Proxy records of storm-wave or storm-wind induced activity in coastal barrier systems deposits have been widely used worldwide in recent years to document past storm events during the last millennia. This review provides a detailed state-of-the-art compilation of the proxies available from coastal barrier systems to reconstruct Holocene storm chronologies (paleotempestology). The present paper aims (I) to describe the erosional and depositional processes caused by storm-wave action in barrier and back-barrier systems (i.e. beach ridges, storm scarps and washover deposits), (ii) to understand how storm records can be extracted from barrier and back-barrier sedimentary bodies using stratigraphical, sedimentological, micro-paleontological and geochemical proxies and (iii) to show how to obtain chronological control on past storm events recorded in the sedimentary successions. The challenges that paleotempestology studies still face in the reconstruction of representative and reliable storm-chronologies using these various proxies are discussed, and future research prospects are outlined.

  11. Holocene palaeoDEMs for lowland coastal and delta plain landscape reconstructions

    NASA Astrophysics Data System (ADS)

    Cohen, Kim M.; Koster, Kay; Pierik, Harm-Jan; Van der Meulen, Bas; Hijma, Marc; Schokker, Jeroen; Stafleu, Jan

    2017-04-01

    Geological mapping of Holocene deposits of coastal plains, such as that of The Netherlands can reach high resolution (dense population, diverse applied usage) and good time control (14C dating, archaeology). The next step is then to create time sliced reconstructions for stages in the Holocene, peeling of the subrecent and exposing past relief situation. This includes winding back the history of sea-level rise and delta progradation etc. etc. So far, this has mainly be done as 2D series of landscape maps, or as sea-level curve age-depth plots. In the last decade, academic and applied projects at Utrecht University, TNO Geological Survey of The Netherlands and Deltares have developed palaeoDEMs for the Dutch low lands, that are a third main way of showing coastal plain evolution. Importantly, we produce two types of palaeoDEMs: (1) geological surface mapping using deposit contacts from borehole descriptions (and scripted 3D processing techniques - e.g. Van der Meulen et al. 2013) and (2) palaeogroundwater surfaces, using sea-level and inland water-level index-points (and 3D kriging interpolations - e.g. Koster et al. 2016). The applications for the combined palaeoDEMs range from relative sea-level rise mapping and assessment of variation in rate of GIA across the coastal plain, to quantification of soft soil deformation, to analysis of pre-embankment extreme flood levels. Koster, K., Stafleu, J., & Cohen, K.M. (2016). Generic 3D interpolation of Holocene base-level rise and provision of accommodation space, developed for the Netherlands coastal plain and infilled palaeovalleys. Basin Research. DOI 10.1111/bre.12202 Van der Meulen, M.J., Doornenbal, J.C., Gunnink, J.L., Stafleu, J., Schokker, J., Vernes, R.W., Van Geer, F.C., Van Gessel, S.F., Van Heteren, S., Van Leeuwen, R.J.W. & Bakker, M.A.J. (2013). 3D geology in a 2D country: perspectives for geological surveying in the Netherlands. Netherlands Journal of Geosciences, 92, 217-241. DOI 10.1017/S0016774600000184

  12. Quantifying Holocene Coastal Retreat From River Morphology in Southern England and Wales

    NASA Astrophysics Data System (ADS)

    Attal, M.; Mudd, S. M.; Hurst, M. D.; Crickmore, B. A.

    2013-12-01

    Southern England and Wales have been undergoing subsidence since the end of the Last Glacial Maximum, with average rates varying between 0.5 and 1.2 mm/yr over the last 10 ka (Shennan and Horton, 2002). Rivers typically respond to subsidence by aggrading (e.g., Ishihara et al., 2012), yet many English and Welsh rivers incise into bedrock at their outlet and exhibit river profiles convexities typical of systems experiencing a drop in base level (e.g., Snyder et al., 2002; Attal et al., 2011). Scientists have proposed that coastal erosion could result in such river morphology (Snyder et al., 2002; Leyland & Darby, 2008, 2009). We combine modelling with topographic analysis of a series of basins along the coast of Southern England and Wales to test whether coastal erosion could explain the occurrence of rivers incising into bedrock at the coast. We further assess whether the distribution of such rivers and the shape of river profiles could be used to constrain amounts of coastal erosion during the Holocene. Within zones characterized by similar lithologies and coastal exposure (i.e. the orientation of the coast and the type of water body it faces), we find that rivers with the smallest basins incise into bedrock at their mouth while rivers with the largest basins experience aggradation. The transition between these two types of basins occurs at a consistent basin size. This signal conforms to model predictions, assuming that the slope of rivers at the coast decreases with increasing basin size. Whereas rivers in basins comprising igneous and/or metamorphic rocks tend to be steeper than rivers flowing on sedimentary bedrock, we find that the critical drainage area does not vary significantly with varying lithology, suggesting that other factors such as spatial variations in coastal retreat exert a stronger control on the spatial distribution of the two types of rivers throughout the study area. Reconstruction of river profiles prior to base level rise allows estimates

  13. Holocene coastal and palaeoenvironmental evolution in the surroundings of the Rioni Delta (Kolkheti lowlands, W Georgia)

    NASA Astrophysics Data System (ADS)

    Laermanns, Hannes; Kelterbaum, Daniel; Elashvili, Mikheil; May, Matthias; Opitz, Stephan; Hülle, Daniela; Rölkens, Julian; Brückner, Helmut

    2016-04-01

    0.0.1 The Kolkheti (Colchis) lowlands form the central part of the extensive coastal lowlands along the Black Sea coast of Georgia. Situated between the Greater and the Lesser Caucasus, favourable climatic conditions resulted in a constant human occupation of the region during the Holocene. However, due to continuous deltaic sedimentation and progradation of the Rioni River, considerable changes of the coastal configuration and the palaeoenvironmental conditions in its hinterland are considered, which also were related to sea-level fluctuations of the Black Sea and modifications in sediment supply. Because there is a paucity of data regarding the Holocene coastal evolution of Western Georgia, this study aims to (i) determine the stratigraphy of the Kolkheti lowlands; (ii) elucidate the palaeogeographical and palaeoenvironmental changes along the Georgian Black Sea coastline; and (iii) reconstruct the (relative) sea-level (RSL) evolution in the study area, and compare these results with other regional studies. 0.0.2 Our research is based on ten sediment cores and two sediment outcrops which from the northern part of the Rioni delta area, i.e. the northern part of the Kolkheti lowlands. The sediment cores were analysed for geochemical and geophysical parameters (X-ray fluorescence spectroscopy, granulometry, loss on ignition, CN analysis) and for their microfaunal content (foraminifera, ostracoda), in order to deduce different depositional environments and their succession throughout the Holocene. The chronostratigraphy is based on 13 14C and 4 IRSL ages. Our results show that significant palaeoenvironmental changes have taken place in the surroundings of the Rioni delta during the last eight millennia. The sedimentary record indicates shallow marine conditions dominating most of the research area during the 6th millennium BC. These deposits are covered by brackish/lagoonal sediments. Lateron and floodplain-related fine-grained alluvial deposits accumulated since the

  14. Holocene coastal morphologies and shoreline reconstruction for the southwestern coast of the Bohai Sea, China

    NASA Astrophysics Data System (ADS)

    Liu, Yanxia; Huang, Haijun; Qi, Yali; Liu, Xiao; Yang, Xiguang

    2016-09-01

    Ground-penetrating radar (GPR) reflection profiles were interpreted and combined with sedimentological data to highlight the morpho-evolutionary history of the southwestern sector of the Bohai Sea. The internal structures in GPR images obtained near the Holocene maximum transgression boundary revealed concave-upward and onlap types of transgressive paleo-topography. The relationship between historical courses of the Yellow River and the distribution of shell ridges at three periods (6 ka, 2 ka, and recent times) showed that the concave-upward types derived from the marine sediments overlap the fluvial sediments, and the onlap types from the marine sediments cover the coastal lagoon sediments. Based on the above paleo-geographical setting, previous sea-level markers were corrected, taking into account uncertainties of their relationship to former water levels. The rates of vertical tectonic displacement, evaluated through comparison of the relative sea level (RSL) data from the GPR images and the Holocene predicted sea-level elevation, markedly affected RSL changes. The fitted RSL curves from the corrected sea-level indicators showed that the accuracy of former sea-level determinations can be improved by comparing with the maximum transgressive position of GPR detection. A topographic digital elevation model (DEM) for 6 ka is reconstructed based on the corrected data.

  15. Coastal barrier stratigraphy for Holocene high-resolution sea-level reconstruction

    PubMed Central

    Costas, Susana; Ferreira, Óscar; Plomaritis, Theocharis A.; Leorri, Eduardo

    2016-01-01

    The uncertainties surrounding present and future sea-level rise have revived the debate around sea-level changes through the deglaciation and mid- to late Holocene, from which arises a need for high-quality reconstructions of regional sea level. Here, we explore the stratigraphy of a sandy barrier to identify the best sea-level indicators and provide a new sea-level reconstruction for the central Portuguese coast over the past 6.5 ka. The selected indicators represent morphological features extracted from coastal barrier stratigraphy, beach berm and dune-beach contact. These features were mapped from high-resolution ground penetrating radar images of the subsurface and transformed into sea-level indicators through comparison with modern analogs and a chronology based on optically stimulated luminescence ages. Our reconstructions document a continuous but slow sea-level rise after 6.5 ka with an accumulated change in elevation of about 2 m. In the context of SW Europe, our results show good agreement with previous studies, including the Tagus isostatic model, with minor discrepancies that demand further improvement of regional models. This work reinforces the potential of barrier indicators to accurately reconstruct high-resolution mid- to late Holocene sea-level changes through simple approaches. PMID:27929122

  16. Coastal barrier stratigraphy for Holocene high-resolution sea-level reconstruction

    NASA Astrophysics Data System (ADS)

    Costas, Susana; Ferreira, Óscar; Plomaritis, Theocharis A.; Leorri, Eduardo

    2016-12-01

    The uncertainties surrounding present and future sea-level rise have revived the debate around sea-level changes through the deglaciation and mid- to late Holocene, from which arises a need for high-quality reconstructions of regional sea level. Here, we explore the stratigraphy of a sandy barrier to identify the best sea-level indicators and provide a new sea-level reconstruction for the central Portuguese coast over the past 6.5 ka. The selected indicators represent morphological features extracted from coastal barrier stratigraphy, beach berm and dune-beach contact. These features were mapped from high-resolution ground penetrating radar images of the subsurface and transformed into sea-level indicators through comparison with modern analogs and a chronology based on optically stimulated luminescence ages. Our reconstructions document a continuous but slow sea-level rise after 6.5 ka with an accumulated change in elevation of about 2 m. In the context of SW Europe, our results show good agreement with previous studies, including the Tagus isostatic model, with minor discrepancies that demand further improvement of regional models. This work reinforces the potential of barrier indicators to accurately reconstruct high-resolution mid- to late Holocene sea-level changes through simple approaches.

  17. Late Holocene sedimentation in coastal areas of the northwestern Ross Sea (Antarctica)

    NASA Astrophysics Data System (ADS)

    Colizza, Ester; Finocchiaro, Furio; Kuhn, Gerhard; Langone, Leonardo; Melis, Romana; Mezgec, Karin; Severi, Mirko; Traversi, Rita; Udisti, Roberto; Stenni, Barbara; Braida, Martina

    2013-04-01

    Sediment cores and box cores collected in two coastal areas of the northwestern Ross Sea (Antarctica) highlight the possibility of studying the Late Holocene period in detail. In this work we propose a study on two box cores and two gravity cores collected in the Cape Hallett and Wood Bay areas during the 2005 PNRA oceanographic cruise. The two sites are feed by Eastern Antarctic Ice Shelf (EAIS) and previous studies have highlighted a complex postglacial sedimentary sequence, also influenced by local morphology. This study is performed within the framework of the PNRA-ESF PolarCLIMATE HOLOCLIP (Holocene climate variability at high-southern latitudes: an integrated perspective) Project. The data set includes: magnetic susceptibility, X-ray analyses, 210Pb, 14C dating, diatoms and foraminifera assemblages, organic carbon, and grain-size analyses. Furthermore XRF core scanner analyses, colour analysis from digital images, and major, minor and trace element concentration analyses (ICP-AES) are performed. Data show that the box core and upper core sediments represent a very recent sedimentation in which it is possible to observe the parameter variability probably linked to climate variability/changes: these variation will be compared with isotopic record form ice cores collected form the same Antarctic sector.

  18. Holocene Coastal Environments near Pompeii before the A.D. 79 Eruption of Mount Vesuvius, Italy

    NASA Astrophysics Data System (ADS)

    Pescatore, Tullio; Senatore, Maria Rosaria; Capretto, Giovanna; Lerro, Gaia

    2001-01-01

    Studies of some 70 bore holes around ancient Pompeii, on the southwestern slope of the Somma-Vesuvius volcano, allow the reconstruction of Holocene environments earlier than the A.D. 79 eruption. This eruption produced about 10 km3 of pyroclastic material that buried the Roman cities of Pompeii, Herculaneum, and Stabiae and promoted a shoreline progradation of 1 km. The Sarno coastal plain, in a post-Miocene sedimentary basin, has been affected by Somma-Vesuvius volcanic activity since the late Pleistocene. At the Holocene transgressive maximum, the sea reached an area east of ancient Pompeii and formed a beach ridge (Messigno, 5600 and 4500 14C yr B.P.) more than 2 km inland from the present shore. Progradation of the plain due to high volcanic supply during the following highstand resulted in a new beach ridge (Bottaro-Pioppaino, 3600 14C yr B.P.) 0.5 km seaward of the Messigno ridge. Ancient Pompeii was built as the shoreline continued to prograde toward its present position. Deposits of the A.D. 79 eruption blanketed the natural levees of the Sarno River, marshes near the city and on the Sarno's floodplain, the morphological highs of Messigno and Bottaro-Pioppaino beach ridges, and the seashore. That shore was probably 1 km landward of the present one.

  19. Coastal barrier stratigraphy for Holocene high-resolution sea-level reconstruction.

    PubMed

    Costas, Susana; Ferreira, Óscar; Plomaritis, Theocharis A; Leorri, Eduardo

    2016-12-08

    The uncertainties surrounding present and future sea-level rise have revived the debate around sea-level changes through the deglaciation and mid- to late Holocene, from which arises a need for high-quality reconstructions of regional sea level. Here, we explore the stratigraphy of a sandy barrier to identify the best sea-level indicators and provide a new sea-level reconstruction for the central Portuguese coast over the past 6.5 ka. The selected indicators represent morphological features extracted from coastal barrier stratigraphy, beach berm and dune-beach contact. These features were mapped from high-resolution ground penetrating radar images of the subsurface and transformed into sea-level indicators through comparison with modern analogs and a chronology based on optically stimulated luminescence ages. Our reconstructions document a continuous but slow sea-level rise after 6.5 ka with an accumulated change in elevation of about 2 m. In the context of SW Europe, our results show good agreement with previous studies, including the Tagus isostatic model, with minor discrepancies that demand further improvement of regional models. This work reinforces the potential of barrier indicators to accurately reconstruct high-resolution mid- to late Holocene sea-level changes through simple approaches.

  20. Lake-sediment record of late Holocene hurricane activities from coastal Alabama

    NASA Astrophysics Data System (ADS)

    Liu, Kam-Biu; Fearn, Miriam L.

    1993-09-01

    Coastal lake sediments contain a stratigraphically and chronologically distinct record of major hurricane strikes during late Holocene time. Frederic—a category 3 hurricane that struck the Alabama coast on the Gulf of Mexico in 1979—left a distinct sand layer in the nearshore sediments of Lake Shelby as a result of storm-tide overwash of beaches and dunes. Sediment cores taken from the center of Lake Shelby contain multiple sand layers, suggesting that major hurricanes of category 4 or 5 intensity directly struck the Alabama coast at ca. 3.2-3.0, 2.6, 2.2, 1.4, and 0.8 ka (14C yr), with an average recurrence interval of ˜600 yr. The Alabama coast is likely to be struck by a category 4 or 5 hurricane within the next century.

  1. Holocene development of the eastern Gulf of Finland coastal zone (Baltic Sea)

    NASA Astrophysics Data System (ADS)

    Ryabchuk, Daria; Sergeev, Alexander; Gusentsova, Tatiana; Gerasimov, Dmitry; Zhamoida, Vladimir; Amantov, Aleksey; Kulkova, Marianna; Sorokin, Peter

    2014-05-01

    In 2011-2013 geoarcheological and marine geological research of the eastern Gulf of Finland coasts and near-shore bottom were undertaken. Researches were concentrated within several key-areas (Sestroretskaya Lowland, Narva-Luga Klint Bay and southern coastal zone of the Gulf (near Bolshaya Izhora village). Study areas can provide important information about Gulf of Finland Holocene coastal development as since Ancylus time (about 10000 cal.BP). Development of numerous sand accretion forms (spits, bars, dunes) of different shape, age and genesis caused formation of lagoon systems, situated now on-land due to land uplift. Coasts of lagoons in Sestroretskaya Lowland and Narva-Luga Klint Bay were inhabited by Neolithic and Early Metal people. Analysis of coastal morphology and results of geological research (GIS relief analyses, ground penetrating radar, drilling, grain-size analyses, radiocarbon dating) and geoarcheological studies allowed to reconstruct the mechanism of large accretion bodies (bars and spits) and lagoon systems formation during last 8000 years. Geoarcheological studies carried out within eastern Gulf of Finland coasts permitted to find some features of the Neolithic - Early Metal settlements distribution. Another important features of the eastern Gulf of Finland coastal zone relief are the series of submarine terraces found in the Gulf bottom (sea water depths 10 to 2 m). Analyses of the submarine terraces morphology and geology (e.g. grain-size distribution, pollen analyses and organic matter dating) allow to suppose that several times during Holocene (including preAncylus (11000 cal.BP) and preLittorina (8500 cal.BP) regressions) the sea-water level was lower than nowadays. During the maximal stage of the Littorina transgression (7600-7200 cal. BP) several open bays connected with the Littorina Sea appeared in this area. The lagoon systems and sand accretion bodies (spits and bars) were formed during the following decreasing of the sea level. Late

  2. Optically stimulated luminescence age controls on late Pleistocene and Holocene coastal lithosomes, North Carolina, USA

    USGS Publications Warehouse

    Mallinson, D.; Burdette, K.; Mahan, S.; Brook, G.

    2008-01-01

    Luminescence ages from a variety of coastal features on the North Carolina Coastal Plain provide age control for shoreline formation and relative sea-level position during the late Pleistocene. A series of paleoshoreline ridges, dating to Marine Isotope Stage (MIS) 5a and MIS 3 have been defined. The Kitty Hawk beach ridges, on the modern Outer Banks, yield ages of 3 to 2??ka. Oxygen-isotope data are used to place these deposits in the context of global climate and sea-level change. The occurrence of MIS 5a and MIS 3 shorelines suggests that glacio-isostatic adjustment (GIA) of the study area is large (ca. 22 to 26??m), as suggested and modeled by other workers, and/or MIS 3 sea level was briefly higher than suggested by some coral reef studies. Correcting the shoreline elevations for GIA brings their elevation in line with other sea-level indicators. The age of the Kitty Hawk beach ridges places the Holocene shoreline well west of its present location at ca. 3 to 2??ka. The age of shoreline progradation is consistent with the ages of other beach ridge complexes in the southeast USA, suggesting some regionally contemporaneous forcing mechanism. ?? 2007 University of Washington.

  3. Trace metal proxies in the Oregon coastal zone- identifying Holocene hypoxic events

    NASA Astrophysics Data System (ADS)

    Erhardt, A. M.; Paytan, A.

    2009-12-01

    Coastal shelf hypoxic events, such as that recently observed off the Oregon coast, are toxic environments for the benthic community. Since 2000, hypoxic (<0.5ml l-1 oxygen) to anoxic conditions have been observed, though historical records from 1950 to 1999 show no record of these conditions. While other hypoxic events (i.e. the Gulf of Mexico) have been attributed to anthropogenic nutrient pollution, it has been postulated that this shelf hypoxia is driven by basin-scale fluctuations in atmosphere-ocean processes. These fluctuations have altered the oxygen content and intensity of upwelling in the region, corresponding to increases in productivity. This study seeks to construct past records of oxygen level to determine if human influence, changes in ocean circulation, or long term climatic cycles are at play. Sediment cores have been collected at multiple locations within the region currently impacted by hypoxia, as well as farther offshore. To identify past anoxic events, trace metal concentrations, specifically redox-sensitive metals such as uranium, vanadium, and molybdenum, have been analyzed. These preliminary results will provide a baseline for identifying the cyclicity and extent of hypoxia in this coastal region throughout the Holocene. The ability to predict the recurrence and evolution of these events will be critical for the formulation of appropriate mitigation measures.

  4. Holocene environmental and climatic changes at Gorgo Basso, a coastal lake in southern Sicily, Italy

    NASA Astrophysics Data System (ADS)

    Tinner, Willy; van Leeuwen, Jacqueline F. N.; Colombaroli, Daniele; Vescovi, Elisa; van der Knaap, W. O.; Henne, Paul D.; Pasta, Salvatore; D'Angelo, Stefania; La Mantia, Tommaso

    2009-07-01

    We used a new sedimentary record to reconstruct the Holocene vegetation and fire history of Gorgo Basso, a coastal lake in south-western Sicily (Italy). Pollen and charcoal data suggest a fire-prone open grassland near the site until ca 10,000 cal yr BP (8050 cal BC), when Pistacia shrubland expanded and fire activity declined, probably in response to increased moisture availability. Evergreen Olea europaea woods expanded ca 8400 to decline abruptly at 8200 cal yr BP, when climatic conditions became drier at other sites in the Mediterranean region. Around 7000 cal yr BP evergreen broadleaved forests ( Quercus ilex, Quercus suber and O. europaea) expanded at the cost of open communities. The expansion of evergreen broadleaved forests was associated with a decline of fire and of local Neolithic ( Ficus carica-Cerealia based) agriculture that had initiated ca 500 years earlier. Vegetational, fire and land-use changes ca 7000 cal yr BP were probably caused by increased precipitation that resulted from (insolation-forced) weakening of the monsoon and Hadley circulation ca 8000-6000 cal yr BP. Low fire activity and dense coastal evergreen forests persisted until renewed human activity (probably Greek, respectively Roman colonists) disrupted the forest ca 2700 cal yr BP (750 BC) and 2100 cal yr BP (150 BC) to gain open land for agriculture. The intense use of fire for this purpose induced the expansion of open maquis, garrigue, and grassland-prairie environments (with an increasing abundance of the native palm Chamaerops humilis). Prehistoric land-use phases after the Bronze Age seem synchronous with those at other sites in southern and central Europe, possibly as a result of climatic forcing. Considering the response of vegetation to Holocene climatic variability as well as human impact we conclude that under (semi-)natural conditions evergreen broadleaved Q. ilex- O. europaea (s.l.) forests would still dominate near Gorgo Basso. However, forecasted climate change and

  5. Middle East coastal ecosystem response to middle-to-late Holocene abrupt climate changes.

    PubMed

    Kaniewski, D; Paulissen, E; Van Campo, E; Al-Maqdissi, M; Bretschneider, J; Van Lerberghe, K

    2008-09-16

    The Holocene vegetation history of the northern coastal Arabian Peninsula is of long-standing interest, as this Mediterranean/semiarid/arid region is known to be particularly sensitive to climatic changes. Detailed palynological data from an 800-cm alluvial sequence cored in the Jableh plain in northwest Syria have been used to reconstruct the vegetation dynamics in the coastal lowlands and the nearby Jabal an Nuşayriyah mountains for the period 2150 to 550 B.C. Corresponding with the 4.2 to 3.9 and 3.5 to 2.5 cal kyr BP abrupt climate changes (ACCs), two large-scale shifts to a more arid climate have been recorded. These two ACCs had different impacts on the vegetation assemblages in coastal Syria. The 3.5 to 2.5 cal kyr BP ACC is drier and lasted longer than the 4.2 to 3.9 cal kyr BP ACC, and is characterized by the development of a warm steppe pollen-derived biome (1100-800 B.C.) and a peak of hot desert pollen-derived biome at 900 B.C. The 4.2 to 3.9 cal kyr BP ACC is characterized by a xerophytic woods and shrubs pollen-derived biome ca. 2050 B.C. The impact of the 3.5 to 2.5 cal kyr BP ACC on human occupation and cultural development is important along the Syrian coast with the destruction of Ugarit and the collapse of the Ugarit kingdom at ca. 1190 to 1185 B.C.

  6. Middle East coastal ecosystem response to middle-to-late Holocene abrupt climate changes

    PubMed Central

    Kaniewski, D.; Paulissen, E.; Van Campo, E.; Al-Maqdissi, M.; Bretschneider, J.; Van Lerberghe, K.

    2008-01-01

    The Holocene vegetation history of the northern coastal Arabian Peninsula is of long-standing interest, as this Mediterranean/semiarid/arid region is known to be particularly sensitive to climatic changes. Detailed palynological data from an 800-cm alluvial sequence cored in the Jableh plain in northwest Syria have been used to reconstruct the vegetation dynamics in the coastal lowlands and the nearby Jabal an Nuşayriyah mountains for the period 2150 to 550 B.C. Corresponding with the 4.2 to 3.9 and 3.5 to 2.5 cal kyr BP abrupt climate changes (ACCs), two large-scale shifts to a more arid climate have been recorded. These two ACCs had different impacts on the vegetation assemblages in coastal Syria. The 3.5 to 2.5 cal kyr BP ACC is drier and lasted longer than the 4.2 to 3.9 cal kyr BP ACC, and is characterized by the development of a warm steppe pollen-derived biome (1100–800 B.C.) and a peak of hot desert pollen-derived biome at 900 B.C. The 4.2 to 3.9 cal kyr BP ACC is characterized by a xerophytic woods and shrubs pollen-derived biome ca. 2050 B.C. The impact of the 3.5 to 2.5 cal kyr BP ACC on human occupation and cultural development is important along the Syrian coast with the destruction of Ugarit and the collapse of the Ugarit kingdom at ca. 1190 to 1185 B.C. PMID:18772385

  7. Have the northwest Negev dunefield sands reddened since their deposition?

    NASA Astrophysics Data System (ADS)

    Roskin, Joel; Tsoar, Haim; Blumberg, Dan G.; Porat, Naomi; Rozensten, Ofer

    2010-05-01

    Sand grain coating redness has been extensively both in coastal and inland desert dunes. In Israel, sand redness has been quantified by calculating a spectral redness index (RI) using single RGB bands (RI= R2/(B*G3)) from reflectance spectroscopy. The RI values have been correlated to ferric oxide mass that was dissolved from sand grain coatings (Ben Dor et al., 2006; Tsoar et al., 2008). Five main requirements have been proposed to enhance sand grain reddening: iron source from the weathering of iron-bearing minerals originating from parent rock or aeolian dust, minimum moisture content, oxidizing interstitial conditions, sediment stability and time. Thus, as many researches have suggested, when the source factors and climatic conditions are homogenous, redder sands indicate increased maturity. The northwest Negev dunefield has been classified by Tsoar et al. (2008) into 3 incursion units based upon contouring a grid of RI values for surface sand samples. The central incursion unit has been suggested to be younger due to relatively lower RI values that decrease to the east. This work tests the relationship between RI values and optically stimulated luminescence (OSL) ages of aeolian sand sampled from the near surface down to dune substrate throughout the NW Negev dunefield. Room-dried sand samples were measured in the laboratory with an ASD FieldSpec spectrometer and RI was calculated. Dune sections have been found to usually have similar RI values throughout their vertical profile despite OSL ages ranging between recent and Late Pleistocene. Along a W-E transect, RI values also tend to be similar. The central (Haluzza) part of the dunefield exhibits significantly lower RI values than RI of sands south of the Qeren Ridge. Dune base OSL ages possibly representing burial/stabilization of an initial incursion are slightly more mature in the south and may be evidence of the earliest dune incursion into the Negev. Thus the increased redness may be attributed to an

  8. Holocene groundwater turnover in an coastal aquifer in Albania - mirrored by isotopes

    NASA Astrophysics Data System (ADS)

    Jacks, G.; Kumanova, Xh; Marku, S.

    2012-04-01

    Holocene groundwater turnover in a coastal aquifer in Albania - mirrored by isotopes Jacks G 1, Kumanova Xh 2 and Marku S 2 1) Dept. of Land and Water Resources Engineering, KTH, SE-114 29 Stockholm, Sweden 2) Albanian Geological Survey, Tirana, Albania Mati River has formed a coastal aquifer in N. Albania serving as a water source for 220 000 people. The near shore portions of the aquifer have a brackish groundwater. A crucial question is to what extent the aquifer is recharged from the alluvial cone at the entrance of the river into the coastal plain and to what extent the brackish water is drawn into a large well-field supplying Durres, the second largest town in Albania. The brackish water was dated by 14C, resulting in ages between 4-7000 years BP. ^18O data showed that the brackish water was not a mixture between sea water and fresh water but had freshwater signature of -5 to -10 o/oo. The low values are caused by the oxidation of sulphides in a copper mining area upstream in the Mati River catchment (Demi 2003). Most likely the salinity is derived from diffusion from saline pore water in intercalated clay layers. A similar condition is found in the coastal Kerala aquifers in Southern India (Jacks et al., 2007). The water extracted in the large well-field has low salinity. ^34S data show that the pumped groundwater has a typical river signature with ^34S = 4-5 o/oo while the brackish near shore water has a sea water signature around 20-21 o/oo. Thus the extracted water is almost entirely supplied by current recharge from the alluvial cone. The salinity now restricted to pore water in the intercalated clay layers might be derived from the Flandrian transgression. A shore line has been observed close to the foothills in the plane by Fouache (2006). The paleo-levels of the sea is very variable along the Adriatic coast as this is a tectonic active areas along the seam between the African and the European plates (Allaj et al. 2001; Fouache 2006; Mathers et al

  9. Sudden, probably coseismic submergence of Holocene trees and grass in coastal Washington State

    SciTech Connect

    Atwater, B.F. ); Yamaguchi, D.K. )

    1991-07-01

    Growth-position plant fossils in coastal Washington State imply a suddenness of Holocene submergence that is better explained coseismic lowering of the land than be decade- or century-long rise of the sea. These fossils include western red cedar and Sitka spruce whose death probably resulted from estuarine submergence close to 300 years ago. Rings in eroded, bark-free trunks of the red cedar show that growth remained normal within decades of death. Rings in buried, bark-bearing stumps of the spruce further show normal growth continuing until the year of death. Other growth-position fossils implying sudden submergence include the stems and leaves of salt-marsh grass entombed in tide-flat mud close to 300 years ago and roughly 1,700 and 3,100 years ago. The preservation of these stems and leaves shows that submergence and initial burial outpaced decomposition, which appears to take just a few years in modern salt marshes. In some places the stems and leaves close to 300 year old are surrounded by sand left by an extraordinary, landward-directed surge-probably a tsunami from a great thrust earthquake on the Cascadia subduction zone.

  10. Wet early to middle Holocene conditions on the upper Coastal Plain of North Carolina, USA

    NASA Astrophysics Data System (ADS)

    Goman, Michelle; Leigh, David S.

    2004-05-01

    A peat core from a cutoff paleochannel of Little River on the upper Coastal Plain of North Carolina provides a continuous pollen record of environmental change for the past 10,500 years and includes a sedimentary record of overbank floods. Palynological and sedimentary data indicate that the early to middle Holocene was wetter than previously suggested from lake sites in the southeastern United States. The period from 9000 to 6100 cal yr B.P. is characterized by high pollen percentages of Nyssa and Quercus, but low percentages of Pinus. Fifteen large overbank flood events are present within this period (5 floods/1000 yr). In contrast, only 6 large overbank flood events occurred since 6100 cal yr B.P. (1 flood/1000 yr). The increases in moisture and flood events probably were controlled by changes in atmospheric circulation related to shifts in the position of the Bermuda High, sea surface temperatures, and El Niño activity that together may have affected the frequency of large floods generated from tropical storms in the region.

  11. Rapid Holocene coastal change revealed by high-resolution micropaleontological analysis, Pamlico Sound, North Carolina, USA

    NASA Astrophysics Data System (ADS)

    Grand Pre, Candace; Culver, Stephen J.; Mallinson, David J.; Farrell, Kathleen M.; Corbett, D. Reide; Horton, Benjamin P.; Hillier, Caroline; Riggs, Stanley R.; Snyder, Scott W.; Buzas, Martin A.

    2011-11-01

    Foraminiferal analyses of 404 contiguous samples, supported by diatom, lithologic, geochronologic and seismic data, reveal both rapid and gradual Holocene paleoenvironmental changes in an 8.21-m vibracore taken from southern Pamlico Sound, North Carolina. Data record initial flooding of a latest Pleistocene river drainage and the formation of an estuary 9000 yr ago. Estuarine conditions were punctuated by two intervals of marine influence from approximately 4100 to 3700 and 1150 to 500 cal yr BP. Foraminiferal assemblages in the muddy sand facies that accumulated during these intervals contain many well-preserved benthic foraminiferal species, which occur today in open marine settings as deep as the mid shelf, and significant numbers of well-preserved planktonic foraminifera, some typical of Gulf Stream waters. We postulate that these marine-influenced units resulted from temporary destruction of the southern Outer Banks barrier islands by hurricanes. The second increase in marine influence is coeval with increased rate of sea-level rise and a peak in Atlantic tropical cyclone activity during the Medieval Climate Anomaly. This high-resolution analysis demonstrates the range of environmental variability and the rapidity of coastal change that can result from the interplay of changing climate, sea level and geomorphology in an estuarine setting.

  12. Holocene coastal notches in the Mediterranean region: Indicators of palaeoseismic clustering?

    NASA Astrophysics Data System (ADS)

    Boulton, S. J.; Stewart, I. S.

    2015-05-01

    Marine tidal notches are developed by bioerosion in the intertidal zones of rocky coasts, but a combination of sea-level change and crustal movements can result in them being raised above or submerged below the water line. For that reason, the present-day elevation of these former shorelines relative to the mean sea level has long been used to quantify relative coastal uplift and subsidence in tectonically active areas, assuming that the sea-level (eustatic) change component is known. Along the microtidal Mediterranean littoral, it is generally assumed that notches develop during relative stillstands of sea level, when tectonic and eustatic trends are in unison, and that discrete notch levels record abrupt shoreline changes caused by local seismic displacements. Recently, however, a climatic model for notch formation has been proposed, in which stable periods of Holocene climate favour enhanced erosion; in this competing model, the rate of sea-level rise is lower than the tectonic uplift rate and individual notches are not specific seismic indicators. Because marine notches are widely used as geomorphic markers of tectonic, and in some cases palaeoseismic, movements, a reappraisal of the geological significance of these strandlines is warranted. In this paper, we explore the two conflicting notch models using a database of Eastern Mediterranean palaeoshorelines. Although we conclude that the spatial and temporal distribution of the notches supports a dominantly tectonic control on notch genesis as a result of earthquake clustering, we highlight how the diachronous timing of notch development tempers their value as tectonic markers.

  13. Rapid Holocene coastal change revealed by high-resolution micropaleontological analysis, Pamlico Sound, North Carolina, USA

    USGS Publications Warehouse

    Grand, Pre C.; Culver, S.J.; Mallinson, D.J.; Farrell, K.M.; Corbett, D.R.; Horton, B.P.; Hillier, C.; Riggs, S.R.; Snyder, S.W.; Buzas, M.A.

    2011-01-01

    Foraminiferal analyses of 404 contiguous samples, supported by diatom, lithologic, geochronologic and seismic data, reveal both rapid and gradual Holocene paleoenvironmental changes in an 8.21-m vibracore taken from southern Pamlico Sound, North Carolina. Data record initial flooding of a latest Pleistocene river drainage and the formation of an estuary 9000. yr ago. Estuarine conditions were punctuated by two intervals of marine influence from approximately 4100 to 3700 and 1150 to 500. cal. yr BP. Foraminiferal assemblages in the muddy sand facies that accumulated during these intervals contain many well-preserved benthic foraminiferal species, which occur today in open marine settings as deep as the mid shelf, and significant numbers of well-preserved planktonic foraminifera, some typical of Gulf Stream waters. We postulate that these marine-influenced units resulted from temporary destruction of the southern Outer Banks barrier islands by hurricanes. The second increase in marine influence is coeval with increased rate of sea-level rise and a peak in Atlantic tropical cyclone activity during the Medieval Climate Anomaly. This high-resolution analysis demonstrates the range of environmental variability and the rapidity of coastal change that can result from the interplay of changing climate, sea level and geomorphology in an estuarine setting. ?? 2011 University of Washington.

  14. A Holocene pollen and diatom record from Vanderlin Island, Gulf of Carpentaria, lowland tropical Australia

    NASA Astrophysics Data System (ADS)

    Prebble, Matiu; Sim, Robin; Finn, Jan; Fink, David

    2005-11-01

    Sedimentary, palynological and diatom data from a dunefield lake deposit in the interior of Vanderlin Island in the Gulf of Carpentaria are presented. Prior to the formation of present perennial lake conditions, the intensified Australian monsoon associated with the early Holocene marine transgression allowed Cyperaceae sedges to colonise the alluvial margins of an expansive salt flat surrounded by an open Eucalyptus woodland. As sea level stabilised between 7500 and 4500 cal yr B.P. coastal dunes ceased to develop allowing dense Melaleuca forest to establish in a Restionaceae swamp. Dune-sand input into the swamp was diminished further as the increasingly dense vegetation prevented fluvial and aeolian transported sand arriving from coastal sources. This same process impounded the drainage basin allowing a perennial lake to form between 5500 and 4000 cal yr B.P. Myriophyllum and other aquatic taxa colonised the lake periphery under the most extensive woodland recorded for the Holocene. The palynological data support an effective precipitation model proposed for northern Australia that suggests more variable conditions in the late Holocene. A more precise measure of effective precipitation change is provided by diatom-based inferences that indicate few changes in lake hydrology. Such interpretations are explained in terms of palynological sensitivity to adjustments in local fire regimes where regional precipitation change may only be recorded indirectly through fire promoting mechanisms, including intensified ENSO periodicity and human impact.

  15. Coastal evidence for Holocene subduction-zone earthquakes and tsunamis in central Chile

    USGS Publications Warehouse

    Dure, Tina; Cisternas, Marco; Horton, Benjamin; Ely, Lisa; Nelson, Alan R.; Wesson, Robert L.; Pilarczyk, Jessica

    2015-01-01

    The ∼500-year historical record of seismicity along the central Chile coast (30–34°S) is characterized by a series of ∼M 8.0–8.5 earthquakes followed by low tsunamis (<4 m) occurring on the megathrust about every 80 years. One exception is the AD 1730 great earthquake (M 9.0–9.5) and high tsunami (>10 m), but the frequency of such large events is unknown. We extend the seismic history of central Chile through a study of a lowland stratigraphic sequence along the metropolitan coast north of Valparaíso (33°S). At this site, higher relative sea level during the mid Holocene created a tidal marsh and the accommodation space necessary for sediment that preserves earthquake and tsunami evidence. Within this 2600-yr-long sequence, we traced six laterally continuous sand beds probably deposited by high tsunamis. Plant remains that underlie the sand beds were radiocarbon dated to 6200, 5600, 5000, 4400, 3800, and 3700 cal yr BP. Sediment properties and diatom assemblages of the sand beds—for example, anomalous marine planktonic diatoms and upward fining of silt-sized diatom valves—point to a marine sediment source and high-energy deposition. Grain-size analysis shows a strong similarity between inferred tsunami deposits and modern coastal sediment. Upward fining sequences characteristic of suspension deposition are present in five of the six sand beds. Despite the lack of significant lithologic changes between the sedimentary units under- and overlying tsunami deposits, we infer that the increase in freshwater siliceous microfossils in overlying units records coseismic uplift concurrent with the deposition of five of the sand beds. During our mid-Holocene window of evidence preservation, the mean recurrence interval of earthquakes and tsunamis is ∼500 years. Our findings imply that the frequency of historical earthquakes in central Chile is not representative of the greatest earthquakes and tsunamis that the central Chilean subduction zone has

  16. Coastline orientation, aeolian sediment transport and foredune and dunefield dynamics of Moçambique Beach, Southern Brazil

    NASA Astrophysics Data System (ADS)

    Miot da Silva, Graziela; Hesp, Patrick

    2010-08-01

    This paper examines the role of coastline orientation on foredune and dunefield development at Moçambique Beach, Southern Brazil. The beach displays significant alongshore variations in exposure to the prevailing winds and waves, grain size, beach/surfzone morphodynamic type, foredune volume, and type and dimensions of the Holocene dune systems. Two wind analyses and calculation of aeolian drift potentials were carried out, one based on 1 year of wind record and another based on a record of 34 years. Monthly topographic surveys of beach and foredunes on 5 profiles along Moçambique beach were conducted over one year to obtain data on beach mobility and width, aeolian sediment transport and foredune development. Southerly winds dominate, and aeolian sediment supply is minimal in the south, moderate in the central portion and high in the northern portion of the embayment. The relationship between actual sediment supply, foredune building and potential sediment supply is relatively poor over one year due to factors such as beach type and mobility, beach moisture levels, rainfall, storm surge and wave scarping. The intermediate term (34 year) record indicates a strong relationship between foredune size and volume, winds and shoreline orientation: foredune volume is minimum in the southern part of the beach and greatest in the northern part of the beach. The Holocene barrier and dunefield development also reflects the long term control of shoreline orientation and increasing longshore gradient in exposure to southerly winds: for the last 6000-7000 years a small foredune developed in the southern portion, parabolics and small transgressive dunes in the central portion, and a large-scale transgressive dunefield in the northern portion.

  17. Large-scale coastal and fluvial models constrain the late Holocene evolution of the Ebro Delta

    NASA Astrophysics Data System (ADS)

    Nienhuis, Jaap H.; Ashton, Andrew D.; Kettner, Albert J.; Giosan, Liviu

    2017-09-01

    The distinctive plan-view shape of the Ebro Delta coast reveals a rich morphologic history. The degree to which the form and depositional history of the Ebro and other deltas represent autogenic (internal) dynamics or allogenic (external) forcing remains a prominent challenge for paleo-environmental reconstructions. Here we use simple coastal and fluvial morphodynamic models to quantify paleo-environmental changes affecting the Ebro Delta over the late Holocene. Our findings show that these models are able to broadly reproduce the Ebro Delta morphology, with simple fluvial and wave climate histories. Based on numerical model experiments and the preserved and modern shape of the Ebro Delta plain, we estimate that a phase of rapid shoreline progradation began approximately 2100 years BP, requiring approximately a doubling in coarse-grained fluvial sediment supply to the delta. River profile simulations suggest that an instantaneous and sustained increase in coarse-grained sediment supply to the delta requires a combined increase in both flood discharge and sediment supply from the drainage basin. The persistence of rapid delta progradation throughout the last 2100 years suggests an anthropogenic control on sediment supply and flood intensity. Using proxy records of the North Atlantic Oscillation, we do not find evidence that changes in wave climate aided this delta expansion. Our findings highlight how scenario-based investigations of deltaic systems using simple models can assist first-order quantitative paleo-environmental reconstructions, elucidating the effects of past human influence and climate change, and allowing a better understanding of the future of deltaic landforms.

  18. The relationship between Holocene cultural site distribution and marine terrace uplift on the coast fringing Coastal Range, Taiwan

    NASA Astrophysics Data System (ADS)

    Yang, Hsiaochin; Chen, Wenshan

    2013-04-01

    According to the collision of Philippine Sea plate and Eurasia plate, a series of left-lateral active faults with reverse sense exists in the Longitudinal Valley of east Taiwan. The Holocene marine terraces along the east coast of the Coastal Range in Taiwan are well known for their very rapid uplift and record tectonic history of this active collision boundary. The Holocene marine terrace sequence resulting from successive sea level change and tectonic activation is subdivided into several steps where the highest and oldest terrace, back to ca 13,000yr BP, reaches up to ca 80 m above sea level, and the lower terraces are mostly erosional ones, overlain by less than 1m thick coral beds in situ. The uplift of the coast is very high, ranging from 5 to 10 m/ka. According to the fabrics of potsherds and geochronological data, the prehistoric cultures in eastern Taiwan could be classified into three stages: Fushan (ca 5000-3500yr BP), Peinan/Chilin (ca3500-2000yr BP), Kweishan (ca2000-1000 yr BP) and Jinpu (ca 1000-400yr BP) cultural assemblages respectively. A great difference exists between the various cultural stage, not only the pottery making techniques, but also the distributions of archaeological sites. Combined with the dynamic geomorphic evolution of marine terraces and the distribution of prehistoric culture sites on the east coast of the Coastal Range, a coastal migration trend could be established.

  19. Reconstructing Holocene sea-level change from coastal freshwater peat: A combined empirical and model-based approach

    NASA Astrophysics Data System (ADS)

    Anderson, William; Gehrels, Roland

    2014-05-01

    Freshwater environments have long been considered to be unsuitable for the reconstruction of Holocene sea-level changes as they provide limiting, rather than precise, sea-level index points. We recorded the stratigraphy of a small beach and backbarrier coastal Phragmites marsh at Hallsands, south Devon, southwest England, using hand-drilled cores and ground penetrating radar, and collected five new sea-level index points from the base of a Holocene peat sequence to refine the regional Holocene relative sea-level curve. We demonstrate that the samples, despite their freshwater origin, represent accurate sea-level index points due to the quantifiable relationship between tide levels and groundwater. By means of water-table monitoring and groundwater modelling we show that the primary controls on the water table in the marsh are: (1) stratigraphy; (2) peat permeability; and (3) recharge rates in the backbarrier marsh. The five index points document relative sea-level positions between 7200 and 2400 cal yr BP. Three points are in good agreement with previously collected regional data from intertidal deposits and two points usefully fill gaps in the existing reconstruction. We present an amended Holocene relative sea-level curve for south Devon, based on 30 data points. We conclude that the base of Holocene freshwater peat sequences in small backbarrier systems provide reliable index points for the reconstruction of relative Holocene sea-level changes provided that: (1) the backbarrier stratigraphy show uninterrupted peat sequences demonstrating that the barrier has remain closed; (2) the water table in the backbarrier marsh is controlled by the tidally-oscillating sea level; (3) values of recharge and peat permeability are such that ponding and drying of the backbarrier marsh is limited; and (4) the beach is relatively thin and its permeability is not the primary control of water-table elevations in the backbarrier marsh. The combined approach of data collection and

  20. Holocene vegetational and coastal environmental changes from the Lago Crispim record in northeastern Pará State, eastern Amazonia.

    PubMed

    Behling, H; Lima da Costa, M

    2001-04-01

    Vegetational and coastal environmental changes have been interpreted from a 600cm long and 764014C yr B.P. old sediment core from Lago Crispim located in the northeastern Pará State in northern Brazil. The radiocarbon dated sediment core was studied by multi-element geochemistry, pollen and charcoal analysis.Holocene Atlantic sea-level rise caused an elevation of local water table, which allowed the formation of organic deposits in a probably former inter-dune valley. Dense, diverse and tall Amazon rain forest, and some restinga (coastal vegetation) covered the study area at the beginning of the record at 764014C yr B.P. Mangrove vegetation developed along rivers close to the core site at that time. Subsequent decrease in less mangrove vegetation near the study site indicates a sea-level regression, beginning since around 700014C yr B.P. Lower sea-levels probably favoured the formation of a local Mauritia/Mauritiella palm swamp at 662014C yr B.P. Oscillations of higher and lower sea-level stands probably changed the size of the local palm swamp area several times between 6620 and 363014C yr B.P. Sea-level transgression at around 363014C yr B.P., caused marked coastal environmental changes: the development of mangroves near the site, the replacement of the local palm swamp by a Cyperaceae swamp, the substitution of the surrounding former Amazon rain forest and some restinga vegetation mainly by salt marshes. High amount carbonised particles suggest a strong human impact by burning on the coastal ecosystems during this late Holocene period.Highest concentrations of NaCl and also Ca, Mg and K in the upper sediment core indicate that the Atlantic was close during the late Holocene period. The core site, which is today 500m from the coastline and only 1-2m above modern sea-level, was apparently never reached by marine excursions during the Holocene.Less representation of mangrove since ca. 184014C yr B.P., may be related due to a slightly lower sea-level or to human

  1. The Fulong coastal area in northeast Taiwan: Late Holocene sedimentary phases including destruction and aggradation

    NASA Astrophysics Data System (ADS)

    Boese, Margot; Luethgens, Christopher; Bauersachs, Marc

    2014-05-01

    -grained sediments yielded ages supporting the results from the coastline The sedimentological records and the geomorphological situation give evidence of a short time period with one or several destructive events that destroyed an older dune system at the coast and may be linked to the deposition of the coarse gravels in the river profile. If the existing age estimates are interpreted in this sense, the time window for such an event is about 660 to 600 years ago. The coast afterwards entered a phase of resilience: the new dune ridge system came into existence, and since then the process of a prograding coastline has been active and was supported by an uplift of about 2mm/a, which was calculated on the base of marine deposits found in two outcrops. Dörschner, N., Reimann, T., Wenske, D., Lüthgens, C., Tsukamoto, S., Frechen, M., Böse, M., 2012: Reconstruction of the Holocene coastal development at Fulong Beach in northeastern Taiwan using optically stimulated luminescence (OSL) dating. Quaternary International, 263, 3-13.

  2. Late Holocene coastal wetlands change, Mississippi Sound, Alabama: Short-term vs. long-term patterns and processes

    SciTech Connect

    Davies, D.J.; Smith, W.E. . Environmental Geology Div.)

    1994-03-01

    Wetlands occupy much of the low-lying mainland coast in Mississippi Sound, Alabama, grading from Spartina salt marsh (48.8 km[sup 2]) to fresh water marshes (13.5 km[sup 2]) to forested wetlands (123.4 km[sup 2]) (Rathbun et al, 1987). These wetlands are undergoing rapid short-term (years to decades) net acreage loss due to headland shoreline erosion. In contrast, long-term (centuries to millennia) change in marsh area is largely due to submergence from Holocene transgression and local subsidence. The Sound overlies drowned Pleistocene-Holocene coastal sediments; existing salt marshes likely developed after inundation of paleomarshes cored at a MHW depth of [minus]3 to [minus]7 m in the mid-Sound (C[sup 14] dates of 4--7,000 Y.B.P.). Geomorphic evidence indicates the primary cause of short-term loss of salt marsh is localized erosion of its seaward edge, rather than submergence. A low (< 1 m) intertidal scarp and narrow sandy beach on open Sound shorelines indicate episodic storm erosion. Linear open Sound shorelines formed by wave modification, in contrast to typically less modified protected shores; nearshore Sound bathymetry shows a gently seaward sloping possible wave-cut terrace. Marsh erosion rates are due to several processes including water energy (background as well as seasonal storms); cohesiveness of marsh sediments; and health of marsh flora. Orientation of the shoreline relative to southerly wind-forced waves during passage of winter cold fronts may be the primary factor. While today's short-term rates of overall vertical coastal inundation are relatively low, the development of new marsh acreage is also negligible. As sediment influx from coastal streams is low, it may be difficult to sustain present marsh acreage should sea level rise accelerate.

  3. Holocene soil-geomorphic surfaces influence the role of salmon-derived nutrients in the coastal temperate rainforest of Southeast Alaska

    Treesearch

    David V. D' Amore; Nicholas S. Bonzey; Jacob Berkowitz; Janine Rüegg; Scott. Bridgham

    2011-01-01

    The influence of salmon-derived nutrients (SDN) is widely accepted as a potential factor in the maintenance of aquatic and terrestrial productivity in North American Coastal rainforests. Holocene alluvial landforms are intimately connected with the return of anadromous salmon, but the influence of the soils that occupy these landforms and support this important...

  4. Do dune sands redden with age? The case of the northwestern Negev dunefield, Israel

    NASA Astrophysics Data System (ADS)

    Roskin, Joel; Blumberg, Dan G.; Porat, Naomi; Tsoar, Haim; Rozenstein, Offer

    2012-08-01

    The redness index of aeolian sand has been shown to be a promising qualitative spectroscopic method to define sand grain redness intensity, which reflects the extent of iron-oxide quartz grain coatings. This study investigates the relationship between redness intensity and optically stimulated luminescence (OSL) based depositional ages of sand samples taken from exposed and fully-drilled vegetated linear dunes in the northwestern Negev dunefield, Israel. Sand redness intensity did not vary greatly along the Negev sand transport paths and dune sections dated to be active during the Late Pleistocene (˜18-11.5 ka), Late Holocene, and modern times. No correlation was found between RI intensity (i.e., redness) and the depositional age of the sand. The relatively uniform RI values and sedimentological properties along most of the dunes suggest that sand grain coating development, and consequent rubification, have probably been minimal since the Late Pleistocene. Although it is possible that RI developed rapidly following deposition in a wetter Late Pleistocene climate, the drier and less stormy Holocene does not seem conducive to sand-grain rubification. Based on analyses of northern Sinai sand samples, remote sensing, and previous studies, we suggest that the attributes of the sand grain RI have been inherited from upwind sources. We propose that the sand grain coatings are early diagenetic features that have been similarly red since their suggested aeolian departure from the middle and upper Nile Delta.

  5. Mineralogical maturity in dunefields of North America, Africa and Australia

    USGS Publications Warehouse

    Muhs, D.R.

    2004-01-01

    Studies of dunefields in central and western North America show that mineralogical maturity can provide new insights into the origin and evolution of aeolian sand bodies. Many of the world's great sand seas in Africa, Asia and Australia are quartz-dominated and thus can be considered to be mineralogically mature. The Algodones (California) and Parker (Arizona) dunes in the southwestern United States are also mature, but have inherited a high degree of mineralogical maturity from quartz-rich sedimentary rocks drained by the Colorado River. In Libya, sediments of the Zallaf sand sea, which are almost pure quartz, may have originated in a similar fashion. The Fort Morgan (Colorado) and Casper (Wyoming) dunefields in the central Great Plains of North America, and the Namib sand sea of southern Africa have an intermediate degree of mineralogical maturity because their sources are large rivers that drained both unweathered plutonic and metamorphic rocks and mature sedimentary rocks. Mojave Desert dunefields in the southwestern United States are quite immature because they are in basins adjacent to plutonic rocks that were their sources. Other dunefields in the Great Plains of North America (those in Nebraska and Texas) are more mature than any possible source sediments and therefore reflect mineralogical evolution over time. Such changes in composition can occur because of either of two opposing long-term states of the dunefield. In one state, dunes are stable for long periods of time and chemical weathering depletes feldspars and other weatherable minerals in the sediment body. In the other state, which is most likely for the Great Plains, abrasion and ballistic impacts deplete the carbonate minerals and feldspars because the dunes are active for longer periods than they are stable. ?? 2003 Elsevier B.V. All rights reserved.

  6. Mineralogical maturity in dunefields of North America, Africa and Australia

    NASA Astrophysics Data System (ADS)

    Muhs, Daniel R.

    2004-04-01

    Studies of dunefields in central and western North America show that mineralogical maturity can provide new insights into the origin and evolution of aeolian sand bodies. Many of the world's great sand seas in Africa, Asia and Australia are quartz-dominated and thus can be considered to be mineralogically mature. The Algodones (California) and Parker (Arizona) dunes in the southwestern United States are also mature, but have inherited a high degree of mineralogical maturity from quartz-rich sedimentary rocks drained by the Colorado River. In Libya, sediments of the Zallaf sand sea, which are almost pure quartz, may have originated in a similar fashion. The Fort Morgan (Colorado) and Casper (Wyoming) dunefields in the central Great Plains of North America, and the Namib sand sea of southern Africa have an intermediate degree of mineralogical maturity because their sources are large rivers that drained both unweathered plutonic and metamorphic rocks and mature sedimentary rocks. Mojave Desert dunefields in the southwestern United States are quite immature because they are in basins adjacent to plutonic rocks that were their sources. Other dunefields in the Great Plains of North America (those in Nebraska and Texas) are more mature than any possible source sediments and therefore reflect mineralogical evolution over time. Such changes in composition can occur because of either of two opposing long-term states of the dunefield. In one state, dunes are stable for long periods of time and chemical weathering depletes feldspars and other weatherable minerals in the sediment body. In the other state, which is most likely for the Great Plains, abrasion and ballistic impacts deplete the carbonate minerals and feldspars because the dunes are active for longer periods than they are stable.

  7. Holocene coastal change in the ancient harbor of Yenikapı-İstanbul and its impact on cultural history

    NASA Astrophysics Data System (ADS)

    Algan, Oya; Yalçın, M. Namık; Özdoğan, Mehmet; Yılmaz, Yücel; Sarı, Erol; Kırcı-Elmas, Elmas; Yılmaz, İsak; Bulkan, Özlem; Ongan, Demet; Gazioğlu, Cem; Nazik, Atike; Polat, Mehmet Ali; Meriç, Engin

    An extensive rescue excavation has been conducted in the ancient harbor of İstanbul (Yenikapı) by the Sea of Marmara, revealing a depositional sequence displaying clear evidence of transgression and coastal progradation during the Holocene. The basal layer of this sequence lies at 6 m below the present sea level and contains remains of a Neolithic settlement known to have been present in the area, indicating that the sea level at ~ 8-9 cal ka BP was lower than 6 m below present. Sea level advanced to its maximum at ~ 6.8-7 cal ka BP, drowning Lykos Stream and forming an inlet at its mouth. After ~ 3 cal ka BP, coastal progradation became evident. Subsequent construction of the Byzantine Harbor (Theodosius; 4th century AD) created a restricted small basin and accumulation of fine-grained sediments. The sedimentation rate was increased due to coastal progradation and anthropogenic factors during the deposition of coarse-grained sediments at the upper parts of the sequence (7th-9th centuries AD). The harbor was probably abandoned after the 11th century AD by filling up with Lykos Stream detritus and continued seaward migration of the coastline.

  8. Mid-Holocene coastal hydrology and salinity changes in the east Taihu area of the lower Yangtze wetlands, China

    NASA Astrophysics Data System (ADS)

    Zong, Yongqiang; Innes, James B.; Wang, Zhanghua; Chen, Zhongyuan

    During the mid-Holocene the eastern Taihu area, on China's Yangtze delta plain, was populated by advanced late Neolithic cultures supported by intensive domesticated rice cultivation. This agricultural system collapsed around 4200 cal yr BP, with severe population decline, the end of the Liangzhu culture, and about half a millennium of very low-scale human activity in the area before the re-establishment of agricultural production. Microfossil analyses from six sedimentary sequences, supported by AMS 14C dating, has allowed reconstruction of mid-Holocene hydrological conditions and salinity changes which would have had a major influence on agricultural viability and cultural history in the coastal wetlands. These data, allied to existing stratigraphic and sea-level records, show that chenier ridges that developed after ca. 7000 cal yr BP in the east of the area sheltered it from marine inundation and, although still connected to the sea through tidal creeks, low-salinity conditions persisted throughout the Neolithic period. There is no evidence that marine flooding caused the collapse of Liangzhu culture. Marine influence was stable and evolved slowly. Social and cultural causes may also have been important, but if environmental change triggered the collapse of Neolithic agricultural society here, other natural forces must be sought to explain this event.

  9. Late Holocene Hydrologic Variability Reconstruction of the Coastal Southwestern United States Using Lake Sediments from Crystal Lake, CA

    NASA Astrophysics Data System (ADS)

    Palermo, J. A.; Kirby, M. E.; Hiner, C.; Leeper, R. J.

    2014-12-01

    This study aims to reconstruct a high resolution, late Holocene record of precipitation variability for the coastal southwestern United States region using sediment cores from Crystal Lake, CA. This region is especially susceptible to droughts and episodic floods, making it of particular importance to understand past hydrologic variability. Crystal Lake is a small, alpine landslide dammed lake in the Angeles National Forest of the San Gabriel Mountains. The lake is the only permanent, freshwater lake located in the range. It is hydrologically closed, meaning all lake level changes are controlled by changes in precipitation: evaporation. To reconstruct past hydrologic variability, two Livingston piston cores were taken 15 m apart in the depocenter of the lake in May 2014. A multi-proxy methodology was utilized including: magnetic susceptibility, total organic matter and total carbonate content, grain size, and bulk d13Corg of sediments. All analyses were conducted at 1 cm contiguous intervals except bulk d13Corg (at 2 cm). Seismic reflection profiles were also generated to examine the basin's stratigraphic features in the context of the individual sediment cores. A working age model was provided by multiple AMS 14C dates from discrete organic matter (i.e., seeds, charcoal). Results from this study are compared to preexisting records of late Holocene hydrologic variability from coastal, central, and southern California. Further, the forcing mechanisms that drive hydrologic change (wet vs. dry episodes) in Southern California, such as ocean-atmosphere interactions including El Niño Southern Oscillation or the Pacific Decadal Oscillation, are discussed.

  10. Late Pleistocene to Holocene environmental changes as recorded in the sulfur geochemistry of coastal plain sediments, southwestern Taiwan

    USGS Publications Warehouse

    Chen, Y.-G.; Liu, J.C.-L.; Shieh, Y.-N.; Liu, T.-K.

    2004-01-01

    A core, drilled at San-liao-wan in the southwestern coastal plain of Taiwan, has been analyzed for total sulfur contents, isotopic values, as well as ratios of pyritic sulfur to organic carbon. Our results demonstrate a close relationship between late Pleistocene sea-level change and the proxies generated in this study. The inorganic sulfur contents indicate that at our study site, the Holocene transgression started at ???11 ka and remained under seawater for thousands of years until the late Holocene, corresponding to a depth of 20 m in the study core. The uppermost 20 m of core shows relatively high total organic carbon (TOC) and ??34S of inorganic sulfur, suggesting a transitional environment such as muddy lagoon or marsh, before the site turned into a modern coastal plain. In the lower part of the core, at depths of 110-145 m (corresponding ages of ???12-30 ka), low sulfur contents are recorded, probably indicating fluvial sediments deposited during the oceanic isotope stage (OIS) 2, a sea-level lowstand. The lower part of the core, roughly within OIS 3, records at least two transgressions, although the transgressional signals may be somewhat obscured by subsequent weathering. The reworked origin of organic matter reported in previous studies is confirmed by our organic sulfur data; however, the marine organic source was periodically dominant. The modern high sulfate concentrations in pore water have no correlation to the other sulfur species in the sediments, probably indicating that the sulfate migrated into the site subsequent to early diagenesis. ?? 2003 Elsevier Ltd. All rights reserved.

  11. Origin and dynamics of the northern South American coastal savanna belt during the Holocene - the role of climate, sea-level, fire and humans

    NASA Astrophysics Data System (ADS)

    Alizadeh, Kamaleddin; Cohen, Marcelo; Behling, Hermann

    2015-08-01

    Presence of a coastal savanna belt expanding from British Guiana to northeastern Brazil cannot be explained by present-day climate. Using pollen and charcoal analyses on an 11.6 k old sediment core from a coastal depression in the savanna belt near the mouth of the Amazon River we investigated the paleoenvironmental history to shed light on this question. Results indicate that small areas of savanna accompanied by a forest type composed primarily by the genus Micropholis (Sapotaceae) that has no modern analog existed at the beginning of the Holocene. After 11,200 cal yr BP, savanna accompanied by few trees replaced the forest. In depressions swamp forest developed and by ca 10,000 cal yr BP replaced by Mauritia swamps. Between 8500 and 5600 cal yr BP gallery forest (composed mainly of Euphorbiaceae) and swamp forest succeeded the treeless savanna. The modern vegetation with alternating gallery forest and savanna developed after 5600 cal yr BP. We suggest that the early Holocene no-analog forest is a relict of previously more extensive forest under cooler and moister Lateglacial conditions. The early Holocene savanna expansion indicates a drier phase probably related to the shift of the Intertropical Convergence Zone (ITCZ) towards its northernmost position. The mid-Holocene forest expansion is probably a result of the combined influence of equatorwards shift of ITCZ joining the South Atlantic Convergence Zone (SACZ). The ecosystem variability during the last 5600 cal yr BP, formed perhaps under influence of intensified ENSO condition. High charcoal concentrations, especially during the early Holocene, indicate that natural and/or anthropogenic fires may have maintained the savanna. However, our results propose that climate change is the main driving factor for the formation of the coastal savanna in this region. Our results also show that the early Holocene sea level rise established mangroves near the study site until 7500 cal yr BP and promoted swamp formation in

  12. Late Wisconsin and Holocene tectonic stability of the United States mid-Atlantic coastal region.

    USGS Publications Warehouse

    Blackwelder, B. W.

    1980-01-01

    Deposits that formed in the intertidal zone during sea-level rise 12 000 to 9000 yr ago have undergone very little differential vertical deformation in the area between New York City and South Carolina. The lack of north-south vertical deformation contrasts with tide-gauge and with precise leveling measurements that have been used to indicate that considerable differential vertical movement is occurring along the coast. Probably, present rates of deformation cannot be extrapolated to early Holocene. Depths of dated in-place intertidal deposits and estimates that suggest the US mid-Atlantic shelf was downwarped during Holocene glacio-isostatic adjustment are used to indicate that eustatic sea levels were not substantially below 30m depth about 12 000 yr BP. -Author

  13. Recent and Holocene climate change controls on vegetation and carbon accumulation in Alaskan coastal muskegs

    NASA Astrophysics Data System (ADS)

    Peteet, Dorothy M.; Nichols, Jonathan E.; Moy, Christopher M.; McGeachy, Alicia; Perez, Max

    2016-01-01

    Pollen, spore, macrofossil and carbon data from a peatland near Cordova, Alaska, reveal insights into the climate-vegetation-carbon interactions from the initiation of the Holocene, c. the last 11.5 ka, to the present (1 ka = 1000 calibrated years before present where 0 = 1950 CE). The Holocene period is characterized by early deposition of gyttja in a pond environment with aquatics such as Nuphar polysepalum and Potamogeton, and a significant regional presence of Alnus crispa subsp. sinuata. Carbon accumulation (50 g/m2/a) was high for a short interval in the early Holocene when Sphagnum peat accumulated, but was followed by a major decline to 13 g/m2/a from 7 to 3.7 ka when Cyperaceae and ericads such as Rhododendron (formerly Ledum) groenlandicum expanded. This shift to sedge growth is representative of many peatlands throughout the south-central region of Alaska, and indicates a drier, more evaporative environment with a large decline in carbon storage. The subsequent return to Sphagnum peat after 4 ka in the Neoglacial represents a widespread shift to moister, cooler conditions, which favored a resurgence of ericads, such as Andromeda polifolia, and increased carbon accumulation rate. The sustained Alnus expansion visible in the top 10 cm of the peat profile is correlative with glacial retreat and warming of the region in the last century, and suggests this colonization will continue as temperature increases and ice melts.

  14. Palynological reconstruction of environmental changes in coastal wetlands of the Florida Everglades since the mid-Holocene

    NASA Astrophysics Data System (ADS)

    Yao, Qiang; Liu, Kam-biu; Platt, William J.; Rivera-Monroy, Victor H.

    2015-05-01

    Palynological, loss-on-ignition, and X-ray fluorescence data from a 5.25 m sediment core from a mangrove forest at the mouth of the Shark River Estuary in the southwestern Everglades National Park, Florida were used to reconstruct changes occurring in coastal wetlands since the mid-Holocene. This multi-proxy record contains the longest paleoecological history to date in the southwestern Everglades. The Shark River Estuary basin was formed 5700 cal yr BP in response to increasing precipitation. Initial wetlands were frequently-burned short-hydroperiod prairies, which transitioned into long-hydroperiod prairies with sloughs in which peat deposits began to accumulate continuously about 5250 cal yr BP. Our data suggest that mangrove communities started to appear after 3800 cal yr BP; declines in the abundance of charcoal suggested gradual replacement of fire-dominated wetlands by mangrove forest over the following 2650 yr. By 1150 cal yr BP, a dense Rhizophora mangle dominated mangrove forest had formed at the mouth of the Shark River. The mangrove-dominated coastal ecosystem here was established at least 2000 yr later than has been previously estimated.

  15. High Holocene coastal uplift gives insight into the seismic behavior at the Arica Bend (Peru-Chile subduction zone)

    NASA Astrophysics Data System (ADS)

    Madella, Andrea; Delunel, Romain; Szidat, Sönke; Schlunegger, Fritz

    2016-04-01

    KEYWORDS: northern Chile, coastal uplift, plate coupling, seismic cycle The Peru-Chile subduction zone offshore of the Arica Bend (18.3° S) is characterized by a seaward-concave geometry, which represents a very uncommon tectonic setting. Several published estimates of plate coupling suggest that the locking degree in the curved segment may be significantly lower than to the north and south of it, however, the lack of historical slip events hinders a full understanding of the seismic behavior in this particular portion of plate interface. We have mapped a terrace located at 35 m a.s.l. ca. 3 km onshore from the mouth of the Lluta river, which debouches immediately to the north of Arica. The sedimentology of the terrace has been described and three wood fragments embedded therein have been collected for radiocarbon dating. In addition, we compared the long stream profile of the Lluta river with its modeled steady-state profile, aiming to detect any possible tectonic perturbation along the trunk stream. Results show that the dated terrace consists of a thin storm deposit embedded within fluvial delta conglomerates, which have been most likely deposited near sea-level at ~10 ka. We thus infer that the coast of the Arica Bend, although characterized by long-term quiescence, has undergone remarkable uplift (~5 mm/y) throughout the Holocene. The vertical displacement has been inferred at roughly 175 km from the trench, which corresponds to the landward termination of the locked zone. Considering this structural position and the long-term absence of coseismic events in this trench segment, we propose that the inferred uplift signal might be related to interseismic flexural buckling, which does not result in permanent crustal deformation. Contrariwise, in the adjacent coastal regions north and south of the Arica Bend, repeated seismic cycles have resulted in long-term permanent crustal deformation, as observable in the uplifted Coastal Cordillera.

  16. Holocene coastal regression and facies patterns in a subtropical arid carbonate environment - The sabkha of Al-Zareq, Qatar

    NASA Astrophysics Data System (ADS)

    Engel, Max; Peis, Kim T.; Strohmenger, Christian J.; Pint, Anna; Rivers, John M.; Brückner, Helmut

    2017-04-01

    The Arabian Gulf is a semi-enclosed, shallow sea, which became flooded some 12,500 years ago. Current relative sea level was first reached c. 7000 to 6500 years ago, while a relative sea-level highstand of c. 2-4 m dates to around 6000-4500 years ago. Supratidal coastal sabkhas (former lagoons), stranded beach ridges and foredune sequences as well as abandoned tidal channels along the coasts of Qatar and the UAE witness this mid-Holocene peak in sea level. Regression since then triggered shoreline migration of up to several kilometers along the low-lying coasts of Qatar, for which, however, detailed reconstructions in space and time are scarce. This study presents facies changes and a scenario for the spatio-temporal evolution of the coastal area of Al Zareq in the inner Gulf of Salwa (SW Qatar), thereby also contributing to a better understanding of reservoirs that formed under arid climatic conditions. Ten vibracores (up to 8 m), two deep drillings (up to 20.5 m) and two trenches covering the entire transgression-regression cycle were investigated. In order to characterize and interpret facies types at Al-Zareq as well as to reconstruct sabkha formation in space and time, grain size and shape distribution (laser diffraction, camsizer), XRD, micro- and macrofossil contents and thin sections were analysed by applying qualitative interpretation, descriptive and multivariate statistics (PCA, MDA, end-member modelling), and RIR (XRD). Thirty-seven samples were radiocarbon dated and four samples were dated by optically stimulated luminescence (OSL). Depositional environments include the following types: eolian dune and interdune (in-situ or reworked), coastal sabkha (diagenetic), saline lake (salina), protected lagoon (sand- or carbonate-dominated), beach and beach spit, tidal channel and tidal bar, as well as open lagoon (low-energy, shallow-subtidal lagoon and low-energy deeper-subtidal).

  17. 3D modelling of mechanical peat properties in the Holocene coastal-deltaic sequence of the Netherlands

    NASA Astrophysics Data System (ADS)

    Koster, Kay; Stouthamer, Esther; Cohen, Kim; Stafleu, Jan; Busschers, Freek; Middelkoop, Hans

    2016-04-01

    Peat is abundantly present within the Holocene coastal-deltaic sequence of the Netherlands, where it is alternating with clastic fluvial, estuarine and lagoonal deposits. The areas that are rich in peat are vulnerable to land subsidence, resulting from consolidation and oxidation, due to loading by overlying deposits, infrastructure and buildings, as well as excessive artificial drainage. The physical properties of the peat are very heterogeneous, with variable clastic admixture up to 80% of its mass and rapid decrease in porosity with increasing effective stress. Mapping the spatial distribution of the peat properties is essential for identifying areas most susceptible to future land subsidence, as mineral content determines volume loss by oxidation, and porosity influences the rate of consolidation. Here we present the outline of a study focusing on mapping mechanical peat properties in relation to density and amount of admixed clastic constituents of Holocene peat layers (in 3D). In this study we use a staged approach: 1) Identifying soil mechanical properties in two large datasets that are managed by Utrecht University and the Geological Survey. 2) Determining relations between these properties and palaeogeographical development of the area by evaluating these properties against known geological concepts such as distance to clastic source (river, estuary etc.). 3) Implementing the obtained relations in GeoTOP, which is a 3D geological subsurface model of the Netherlands developed by the Geological Survey. The model will be used, among others, to assess the susceptibility of different areas to peat related land subsidence and load bearing capacity of the subsurface. So far, our analysis has focused stage 1, by establishing empirical relations between mechanical peat properties in ~70 paired (piezometer) cone penetration tests and continuously cored boreholes with LOI measurements. Results show strong correlations between net cone resistance (qn), excess pore

  18. Holocene coastal carbonates and evaporites of the southern Arabian Gulf and their ancient analogues

    NASA Astrophysics Data System (ADS)

    Alsharhan, A. S.; Kendall, C. G. St. C.

    2003-06-01

    The Holocene sediments of the coast of the United Arab Emirates in the southeastern Arabian Gulf are frequently cited in the literature as type examples for analogous assemblages of carbonates, evaporites and siliciclastics throughout the geologic record. This paper is intended as a convenient single source for the description of sediments of this region, providing information on how to reach the classic localities and some of the analogs. The Holocene sediments of the region accumulate over an area that is 500 km long and up to 60 km wide. The sediments collecting offshore are predominantly pelecypod sands mixed with lime and argillaceous mud, with these latter fine sediments increasing as the water deepens. The pelecypod-rich sediments also collect east of Abu Dhabi Island both in the deeper tidal channels between the barrier island lagoons and in deeper portions of the protected lagoons. West of Abu Dhabi Island the shallow water margin is the site of coral reefs and coralgal sands, whereas to the east oolites accumulate on the tidal deltas of channels located between barrier islands. Grapestones accumulate to the lee of the reefs and the oolite shoals where cementation becomes more common. They are particularly common on the less protected shallow water margins of the lagoons west of Abu Dhabi Island. Pelleted lime muds accumulate in the lagoons in the lee of the barrier islands of the eastern Abu Dhabi. Lining the inner shores of the protected lagoons of Abu Dhabi and on other islands to the west are cyano-bacterial mats and mangrove swamps. Landward of these, a prograding north facing shoreline is formed by supratidal salt flats (sabkhas), in which evaporite minerals are accumulating. This paper describes the localities associated with (1) the mangrove swamps of the west side of the Al Dhabaiya peninsula; (2) the indurated cemented carbonate crusts, cyanobacterial flats and sabkha evaporites on the shore of the Khor al Bazam south of Qanatir Island; (3) the

  19. Holocene history of the El Nino phenomenon as recorded in flood sediments of northern coastal Peru

    SciTech Connect

    Wells, L.E. )

    1990-11-01

    Significant precipitation along the north-central coast of Peru (lat 5{degree}-10{degree}S) occurs exclusively during El Nino incursions of warm water into the Peruvian littoral. Flood deposits from this region therefore provide a proxy record of extreme El Nino events. The author presents a 3,500 yr chronology of the extreme events based on radiocarbon dating of overbank flood sediments from the Rio Casma (lat 9.2{degree}S). The flood-plain stratigraphy suggests that the El Nino phenomenon has occurred throughout the Holocene and that flood events much larger than that which occurred during 1982-1983 occur here at least once very 1,000 yr.

  20. Morphodynamics, boundary conditions and pattern evolution within a vegetated linear dunefield

    NASA Astrophysics Data System (ADS)

    Telfer, M. W.; Hesse, P. P.; Perez-Fernandez, M.; Bailey, R. M.; Bajkan, S.; Lancaster, N.

    2017-08-01

    The controls on the evolution of linear dunefields are poorly understood, despite the potential for reactivation of dunefields, which are currently stabilized by vegetation, under the influence of 21st century climate change. The relative roles of local influences (i.e. boundary conditions) and morphodynamic influences (i.e. emergent properties) remain unclear. Chronostratigraphic and sedimentological analyses were conducted on two pairs of linear dunes exhibiting different spatial patterning in the Strzelecki Desert of central Australia. It was hypothesized that morphodynamic influences, via pattern-coarsening, would mean that dunes from the simpler pattern, defined in terms of the frequency of defects (i.e. junctions and terminations), would be more mature, older landforms. Optically Stimulated Luminescence (OSL) dating of full-depth, regularly-sampled profiles was used to establish accumulation histories for the four dunes, and supported by sedimentological analysis to investigate possible compositional differences and similarities between the dunes. Whilst three of the dunes (the two more simply-patterned dunes, and one of the more complex dunes) have accumulation histories beginning between 100 ka and 150 ka, and document sporadic net accumulation throughout the last interglacial/glacial cycle to the late Holocene, one of the dunes (with relatively complex patterning) reveals that the majority of the dune accumulation (> 7 m) at that site occurred during a relatively short window at 50 ka. There is no clear sedimentological reason for the different behaviour of the younger dune. The data suggest that small-scale and essentially stochastic nature of the aeolian depositional/erosional system can overprint any large-scale morphodynamic controls. The concept of dating landscape change by pattern analysis is thus not supported by this study, and would require very careful interpretation of the scales being considered. This further suggests caution when interpreting

  1. Definition and interpretation of Holocene shorelines in the south Atlantic coastal zone, southeast Florida

    SciTech Connect

    Finkl, C.W. Jr.

    1985-01-01

    There is a wide variety of contemporary shorelines in southeastern Florida. Distinctive types range from rocky platforms, tidal flats, mangroves and marshes, to sand and gravel beaches. Because the natural sequence of shorelines in the urban coastal corridor from Miami to Palm Beach is partly obscured by dredge and fill operations initiated in the early 1920's, some coastal segments are subject to re-interpretation. Analysis of early aerial photographs, old coastal charts and bore log data indicates a much more complicated sequence of Recent coastlines than is generally appreciated. Before development, much of the coastal zone contained complicated networks of fresh-water marshes and lakes with lagoons, bays, and sounds lying behind extensively developed spits. The larger spits prograded southward (downdrift) forming long coastwise sounds that eventually led into fresh-water marshes such as Lake Mabel (now Port Everglades). When new inlets were cut to link the ICW with the sea, the spits were beheaded to form what are now called barrier islands. After subsequent inlet stabilization with inadequate sand bypassing, some spits became welded to the shore and others eroded away. Extension of boundaries marking the back sides of barriers landward into the marshes, to the position of the ICW, is not only an erroneous definition of barrier island width but dangerous for emergency (storm surge) planning because the barriers were never this wide. Beach ridge plains, ridge and swale topography, dune-covered limestone ridges, and some fossil reefs such as Key Biscayne have in addition been mistakenly identified as barrier islands.

  2. Coastal Lake Record of Holocene Paleo-Storms from Northwest Florida

    NASA Astrophysics Data System (ADS)

    Donoghue, J. F.; Coor, J. L.; Wang, Y.; Das, O.; Kish, S.; Elsner, J.; Hu, X. B.; Niedoroda, A. W.; Ye, M.

    2009-12-01

    The northwest Florida coast of the Gulf of Mexico has an unusually active storm history. Climate records for a study area in the mid-region of the Florida panhandle coast show that 29 hurricanes have made landfall within a 100-km radius during historic time. These events included 9 major storms (category 3 or higher). A longer-term geologic record of major storm impacts is essential for better understanding storm climatology and refining morphodynamic models. The Florida panhandle region contains a series of unique coastal lakes which are long-lived and whose bottom sediments hold a long-term record of coastal storm occurrence. The lakes are normally isolated from the open Gulf, protected behind a near-continuous dune barrier. Lake water is normally fresh to brackish. Lake bottom sediments consist of organic-rich muds. During major storms the dunes are breached and the lakes are temporarily open to marine water and the possibility of sandy overwash. Both a sedimentologic and geochemical signature is imparted to the lake sediments by storm events. Bottom sediment cores have been collected from the lakes. The cores have been subsampled and subjected to sedimentologic, stable isotopic and geochronologic analyses. The result is a sediment history of the lakes, and a record of storm occurrence during the past few millennia. The outcome is a better understanding of the long-term risk of major storms. The findings are being incorporated into a larger model designed to make reliable predictions of the effects of near-future climate change on natural coastal systems and on coastal infrastructure, and to enable cost-effective mitigation and adaptation strategies.

  3. Simple technologies and diverse food strategies of the Late Pleistocene and Early Holocene at Huaca Prieta, Coastal Peru.

    PubMed

    Dillehay, Tom D; Goodbred, Steve; Pino, Mario; Vásquez Sánchez, Víctor F; Tham, Teresa Rosales; Adovasio, James; Collins, Michael B; Netherly, Patricia J; Hastorf, Christine A; Chiou, Katherine L; Piperno, Dolores; Rey, Isabel; Velchoff, Nancy

    2017-05-01

    Simple pebble tools, ephemeral cultural features, and the remains of maritime and terrestrial foods are present in undisturbed Late Pleistocene and Early Holocene deposits underneath a large human-made mound at Huaca Prieta and nearby sites on the Pacific coast of northern Peru. Radiocarbon ages indicate an intermittent human presence dated between ~15,000 and 8000 calendar years ago before the mound was built. The absence of fishhooks, harpoons, and bifacial stone tools suggests that technologies of gathering, trapping, clubbing, and exchange were used primarily to procure food resources along the shoreline and in estuarine wetlands and distant mountains. The stone artifacts are minimally worked unifacial stone tools characteristic of several areas of South America. Remains of avocado, bean, and possibly cultivated squash and chile pepper are also present, suggesting human transport and consumption. Our new findings emphasize an early coastal lifeway of diverse food procurement strategies that suggest detailed observation of resource availability in multiple environments and a knowledgeable economic organization, although technologies were simple and campsites were seemingly ephemeral and discontinuous. These findings raise questions about the pace of early human movement along some areas of the Pacific coast and the level of knowledge and technology required to exploit maritime and inland resources.

  4. Simple technologies and diverse food strategies of the Late Pleistocene and Early Holocene at Huaca Prieta, Coastal Peru

    PubMed Central

    Dillehay, Tom D.; Goodbred, Steve; Pino, Mario; Vásquez Sánchez, Víctor F.; Tham, Teresa Rosales; Adovasio, James; Collins, Michael B.; Netherly, Patricia J.; Hastorf, Christine A.; Chiou, Katherine L.; Piperno, Dolores; Rey, Isabel; Velchoff, Nancy

    2017-01-01

    Simple pebble tools, ephemeral cultural features, and the remains of maritime and terrestrial foods are present in undisturbed Late Pleistocene and Early Holocene deposits underneath a large human-made mound at Huaca Prieta and nearby sites on the Pacific coast of northern Peru. Radiocarbon ages indicate an intermittent human presence dated between ~15,000 and 8000 calendar years ago before the mound was built. The absence of fishhooks, harpoons, and bifacial stone tools suggests that technologies of gathering, trapping, clubbing, and exchange were used primarily to procure food resources along the shoreline and in estuarine wetlands and distant mountains. The stone artifacts are minimally worked unifacial stone tools characteristic of several areas of South America. Remains of avocado, bean, and possibly cultivated squash and chile pepper are also present, suggesting human transport and consumption. Our new findings emphasize an early coastal lifeway of diverse food procurement strategies that suggest detailed observation of resource availability in multiple environments and a knowledgeable economic organization, although technologies were simple and campsites were seemingly ephemeral and discontinuous. These findings raise questions about the pace of early human movement along some areas of the Pacific coast and the level of knowledge and technology required to exploit maritime and inland resources. PMID:28560337

  5. Holocene sea-level changes in King George Island, West Antarctica, by virtue of geomorphological coastal evidences and diatom assemblages of sediment sections.

    NASA Astrophysics Data System (ADS)

    Poleshchuk, Ksenia; Verkulich, Sergey; Pushina, Zina; Jozhikov, Ilya

    2015-04-01

    A new curve of relative sea-level change is presented for the Fildes peninsula, King George Island, West Antarctic. This work is based on renewed paleogeography data, including coastal geomorphological evidence, diatom assemblages of lakes bottom sediments and radiocarbon datings of organics. The new data were obtained in several sections of quaternary sediments and groups of terraces, and allows us to expand and improve relevant conception about relative sea level changes in the King George Island region. The new radiocarbon datings of organics (mosses and shells) allows reconstructing Holocene conditions that maintain and cause the sea-level changes. Sea diatom assemblages of Dlinnoye lake bottom sediment core (that complies period about 8000 years B.P.) mark altitude of marine water penetrated into the lake. The altitudes of shell remains, which have certain life habits and expect specific salinity and depth conditions, coupled with their absolute datings, indicate the probable elevation of the past sea level. The Mid-Holocene marine transgression reached its maximum level of 18-20 m by 5760 years B.P. The transgression influenced the deglaciation of the Fildes peninsula and environment conditions integrally. The ratio of glacio-isostatic adjustment velocity and Holocene transgression leaded to the decrease of relative sea level during the Late Holocene excluding the short period of rising between 2000 and 1300 years B.P. Comparing this data with the curve for Bunger oasis, East Antarctica, introduced earlier gives an interesting result. Despite the maximum altitudes of relative sea-level rise in King George region were higher and occurred later than in Bunger oasis region, the short-term period of Late Holocene sea-level rising contemporizes. Besides that, this work allow to realize a correlation between regions of Antarctica and adjacent territory. That, in turn, lets answer the question of tectonic and eustatic factors ratio and their contribution to the

  6. The Tsitsikamma coastal shelf, Agulhas Bank, South Africa: example of an isolated Holocene sediment trap

    NASA Astrophysics Data System (ADS)

    Flemming, Burg W.; Keith Martin, A.

    2017-04-01

    Under certain geomorphological conditions, sandy sediments supplied to a coast may become trapped in nearshore sedimentary compartments because these are laterally confined by bedload boundaries or convergences. Where sediment supply is small or the shoreface very steep, and accommodation space as a consequence large, the trapping mechanism may be very efficient. The Tsitsikamma coast along the South African south coast is a case in point, the sediment supplied by local rivers over the past 12 ka having been trapped in a nearshore sediment wedge extending at least 5 km offshore. On the basis of high-resolution seismic surveys, the volume of the sediment wedge has been estimated at 1,354×106 m3. As 5% of this volume is considered to have been contributed by bioclastic material of marine origin, the terrestrial input would be 1,286×106 m3. This amounts to an average annual terrestrial sediment input of 0.1072×106 m3. Using a detailed sediment yield map, the modern mean annual sediment supply to the Tsitsikamma coast by local rivers has been estimated at 0.1028×106 m3. Unless coincidental, the remarkable similarity of the two values suggests that the current climatic conditions along the Tsitsikamma coast correspond to the Holocene mean. This conclusion is supported by the currently available climate data for the South African south coast.

  7. Evolution of Holocene tidal systems along the Dutch coast: effects of rivers, coastal boundary conditions, eco-engineering species, inherited relief and human interference

    NASA Astrophysics Data System (ADS)

    Haas, T. D.; Pierik, H. J.; van der Spek, A.; Cohen, K.; van Maanen, B.; Kleinhans, M. G.

    2016-12-01

    Estuaries and tidal basins are partly enclosed coastal bodies of water with a free connection to the open sea at their tidal inlet and with no to marginal riverine input (tidal basins) or substantial riverine input (estuaries). Their tidal inlets can only remain open over Holocene timescales when (1) the formation of accommodation space exceeds infilling or (2) the inlet system is in dynamic equilibrium (sediment input equals output). Physical and numerical modelling suggest that estuaries and tidal basins develop toward a dynamic equilibrium under constant boundary conditions and remain open over long timescales, whereas many natural estuaries and tidal basins have filled up and were closed off or became deltas during the Holocene. This raises the question if and how tidal inlets can remain open over long timescales? And what is the effect of river inflow and sediment supply thereon? Here we compare the Holocene evolution of tidal systems along the Dutch coast to empirically identify the most important factors that control their long-term evolution. Along the coast of the Netherlands estuaries and tidal basins were formed during the middle Holocene driven by rapid relative sea-level rise and during the late Holocene driven by natural and human-induced subsidence in coastal plain peatlands. During the Holocene tidal inlets connected to rivers (estuaries) were able to persist and attain dynamic equilibrium while tidal basins without or with a very marginal riverine inflow were unstable and closed off under abundant sediment supply. There are many examples of long-lived tidal inlets that rapidly closed off after upstream river avulsion leading to a decrease and finally loss of riverine input. Long-term net import of sediment from the sea into Dutch tidal basins is favoured by strong, flood-dominated, tidal asymmetry along the Dutch coast, the shallow sand-rich floor of the North Sea and the abundance of mud in the coastal area supplied by the Rhine and Meuse rivers

  8. HOLOCENE AND LATE PLEISTOCENE(? ) EARTHQUAKE-INDUCED SAND BLOWS IN COASTAL SOUTH CAROLINA.

    USGS Publications Warehouse

    Obermeier, S.F.; Jacobson, R.B.; Powars, D.S.; Weems, R.E.; Hallbick, D.C.; Gohn, G.S.; Markewich, H.W.

    1986-01-01

    Multiple generations of prehistoric sand blows, interpreted as earthquake induced, have been discovered throughout coastal South Carolina. These sand blows extend far beyond 1886 earthquake induced sand blows, in sediments having approximately the same liquefaction susceptibility. The seismic source zone for the prehistoric sand blows is unknown. The different distributions of prehistoric and 1886 sand blows have two possible explanations: (1) moderate to strong earthquakes originated in different seismic source locations through time or (2) at least one earthquake much stronger than the 1886 event also originated from the same seismic source as the 1886 earthquake.

  9. A simple cellular model to quantify controls on aeolian dune-field pattern development

    NASA Astrophysics Data System (ADS)

    Eastwood, E. N.; Nield, J. M.; Baas, A. C.; Kocurek, G.

    2009-12-01

    A second-generation, source-to-sink cellular automaton model captures and quantifies many of the factors controlling the evolution of aeolian dune-field patterns by varying only a small number of parameters. Our model quantifies the role of sediment supply, sediment availability, and transport capacity in the development and evolution of an aeolian dune-field pattern over long time scales. Simulation results produced by varying the sediment supply and transport capacity identified seven dune-field patterns. A new clustered dune-field pattern is identified and used to propose an alternative mechanism for the formation of superimposed dunes. Bedforms are hypothesized to cluster together, simultaneously forming two spatial scales of bedforms without first developing a large basal dune and small superimposed dunes. Sediment supply and transport capacity control the type and frequency of dune interactions, the sediment availability of the system, and ultimately the development of dune-field patterns. Our model allows predictions about the range of sediment supply and wind strengths required to produce many of the dune-field patterns seen in the real world. This simple model demonstrates the dominant control of aeolian sediment state on the construction and evolution of aeolian dune-field patterns.

  10. Holocene sea surface temperatures in the East African Coastal Current region and their relationship with North Atlantic climate

    NASA Astrophysics Data System (ADS)

    Kuhnert, Henning; Kuhlmann, Holger; Mohtadi, Mahyar; Pätzold, Jürgen

    2013-04-01

    The East African Coastal Current (EACC) is one of the western boundary currents of the Indian Ocean and represents the only pathway for southern water masses to enter the Arabian Sea. Today, sea surface temperatures (SST) in the western boundary currents region covary with those in large parts of the central tropical Indian Ocean. The latter play an important role in global climate by influencing the mean state of the North Atlantic Oscillation (NAO) and associated Atlantic SST anomalies (Hoerling et al., 2001). In the EACC region paleoclimate data are sparse and its Holocene temperature history is unexplored. We present data from a 5 m long sediment core retrieved off northern Tanzania where the EACC flows northward year-round. Proximity to the Pangani River mouth provides a steady sediment supply. We have reconstructed SST from Mg/Ca and stable oxygen isotope ratios (^18O) of the surface-dwelling planktonic foraminifera species Globigerinoides ruber (sensu stricto). Our record spans the time period from 9700 to 1400 years BP at an average temporal resolution of 40 years. The Holocene is characterized by a sequence of intervals representing cool, warm, cool, and intermediate SST, with boundaries at 7.8, 5.6, and 4.4 ka BP. SST anomalies relative to the series mean range from -0.6 to +0.75 ° C. This pattern strikingly resembles a Northwest Atlantic foraminiferal ^18O record (Cléroux et al., 2012), with warm Indian SST corresponding to low Atlantic foraminiferal ^18O (indicating low sea surface density). This matches the modern situation on the interdecadal time-scale, where a warm Indian Ocean leads to a shift of the NAO towards a positive mean state, which is accompanied by SST warming over much of the low- and mid-latitude western Atlantic and a displacement of the Gulf Stream path. We hypothesize that this mechanism also operates on millennial time-scales to explain the obvious similarities in the SST patterns observed in the Northwest Atlantic and western

  11. Supergroup stratigraphy of the Atlantic and Gulf Coastal Plains (Middle? Jurassic through holocene, Eastern North America)

    USGS Publications Warehouse

    Weems, R.E.; ,; Edwards, L.E.

    2004-01-01

    An inclusive supergroup stratigraphic framework for the Atlantic and Gulf Coastal Plains is proposed herein. This framework consists of five supergroups that 1) are regionally inclusive and regionally applicable, 2) meaningfully reflect the overall stratigraphic and structural history of the Coastal Plains geologic province of the southeastern United States, and 3) create stratigraphic units that are readily mappable and useful at a regional level. Only the Marquesas Supergroup (Lower Cretaceous to lowest Upper Cretaceous) has been previously established. The Trent Supergroup (middle middle Eocene to basal lower Miocene) is an existing name here raised to supergroup rank. The Minden Supergroup (Middle? through Upper Jurassic), the Ancora Supergroup (Upper Cretaceous to lower middle Eocene), and the Nomini Supergroup (lower Miocene to Recent) are new stratigraphic concepts proposed herein. In order to bring existing groups and formations into accord with the supergroups described here, the following stratigraphic revisions are made. 1) The base of the Shark River Formation (Trent Supergroup) is moved upward. 2) The Old Church Formation is removed from the Chesapeake Group (Nomini Supergroup) and moved to the Trent Supergroup without group placement. 3) The Tiger Leap and Penney Farms formations are removed from the Hawthorn Group (Nomini Supergroup) and moved to the Trent Supergroup without group placement. 4) The Piney Point and Chickahominy formations are removed from the Pamunkey Group (Ancora Supergroup) and moved to the Trent Supergroup without group placement. 5) the Tallahatta Formation is removed from the Claiborne Group (Trent Supergroup) and placed within the Ancora Supergroup without group placement.

  12. Paleolimnological reconstruction of Holocene environments in wetland ponds of the Upper Atlantic Coastal Plain

    SciTech Connect

    Gaiser, E.E.; Taylor, B.E.

    1995-06-01

    The paleohydrology and paleoecology of Carolina bays and upland wetland ponds on the Savannah River Site (SRS), Aiken, South Carolina are being investigated to reconstruct environmental changes brought about by long-term variation in the climate of the Upper Atlantic Coastal Plain. Cores were taken in transacts through Flamingo Bay, a temporary pond on the SRS, to determine the vertical and horizontal sediment particle size and diatom, plant phytolith and sponge spicule microfossils. Stratigraphic data were used to construct a 3-dimensional map of the basin. In conjunction with archaeological data from the rim of the pond, physical stratigraphic data indicate a decrease in pond size and depth during the past 10,000 years. In order to infer past ecological settings from the fossil record, a survey to determine microhabitat requirements of regional diatom flora was undertaken in 43 temporary ponds throughout the coastal plain of South Carolina. The relationships between diatom assemblages and environmental variables were assessed using canonical correspondence analysis. Variables contributing significantly to the diatom-environment relationship included surface core location (near shore or pelagic), water depth, hydroperiod, microhabitat substrate, and sampling date, in order of decreasing influence. Strong relationships of diatom assemblages to drought frequency within and among basins provides a reliable basis for water level reconstruction in upland temporary ponds.

  13. Evidence of episodic coastal change during the Late Holocene: The Dungeness barrier complex, SE England

    NASA Astrophysics Data System (ADS)

    Plater, A. J.; Stupples, P.; Roberts, H. M.

    2009-03-01

    The sediments of the Dungeness gravel foreland and, in particular, the back-barrier marshland of Romney Marsh are studied in an investigation of (i) temporal and spatial changes in the relative importance of factors driving drift-aligned barrier evolution and (ii) non-linear coastal change. Evidence from palaeomagnetic secular variation (PSV) dating of six marshland cores coupled with particle size data and statistical analysis of heterolithic tidal rhythmites reveals a phase of rapid tidal sedimentation in both inter- and back-barrier 'lows' during the period of c. 1100 to 500 years ago, driven primarily by changing coastal morphology, accommodation space and tidal dynamics. Variations in particle size and layer thickness can be related directly to tidal cyclicity, from which accretion rates of the order of 0.3 m/year are determined. Once shoreface emergence occurred, it is apparent that gravel barrier and marshland deposition were both episodic and rapid. Within this non-linear response, two periods of episodic marshland accretion are identified: an earlier one 1100-600 years ago resulting from cannibalisation of the southern shore of Dungeness foreland and inundation of the exposed inter-ridge lows, and a later period about 600-500 years ago in a true back-barrier setting created by eastward extension of the shoreface spit and foreland ness. A high level of inter-dependence between shoreface, barrier and back- (and inter-) barrier environments is confirmed, as well as marked non-linearity directly related to this inter-dependence. Here, drift-aligned gravel foreland evolution takes place through lateral (down-drift) rollover controlled by shoreface topography and continued sediment supply through cannibalisation (sediment recycling).

  14. Rapid late Pleistocene/Holocene uplift and coastal evolution of the southern Arabian (Persian) Gulf

    NASA Astrophysics Data System (ADS)

    Wood, Warren W.; Bailey, Richard M.; Hampton, Brian A.; Kraemer, Thomas F.; Lu, Zhong; Clark, David W.; James, Rhodri H. R.; Al Ramadan, Khalid

    2012-03-01

    The coastline along the southern Arabian Gulf between Al Jubail, Kingdom of Saudi Arabia, and Dubai, UAE, appears to have risen at least 125 m in the last 18,000 years. Dating and topographic surveying of paleo-dunes (43-53 ka), paleo-marine terraces (17-30 ka), and paleo-marine shorelines (3.3-5.5 ka) document a rapid, > 1 mm/a subsidence, followed by a 6 mm/a uplift that is decreasing with time. The mechanism causing this movement remains elusive but may be related to the translation of the coastal area through the backbasin to forebulge hinge line movement of the Arabian plate or, alternatively, by movement of the underlying Infracambrian-age Hormuz salt in response to sea-level changes associated with continental glaciation. Independent of the mechanism, rapid and episodic uplift may impact the design of engineering projects such as nuclear power plants, airports, and artificial islands as well as the interpretation of sedimentation and archeology of the area.

  15. A Holocene record of climate-driven shifts in coastal carbon sequestration

    USGS Publications Warehouse

    Mitra, Siddhartha; Zimmerman, A.R.; Hunsinger, G.B.; Willard, D.; Dunn, J.C.

    2009-01-01

    A sediment core collected in the mesohaline portion of Chesapeake Bay was found to contain periods of increased delivery of refractory black carbon (BC) and polycyclic aromatic hydrocarbons (PAHs). The BC was most likely produced by biomass combustion during four centennialscale dry periods as indicated by the Palmer Drought Severity Index (PDSI), beginning in the late Medieval Warm Period of 1100 CE. In contrast, wetter periods were associated with increased non-BC organic matter influx into the bay, likely due to greater runoff and associated nutrient delivery. In addition, an overall increase in both BC and non-BC organic matter deposition during the past millennium may reflect a shift in climate regime. The finding that carbon sequestration in the coastal zone responds to climate fluctuations at both centennial and millennial scales through fire occurrence and nutrient delivery has implications for past and future climate predictions. Drought-induced fires may lead, on longer timescales, to greater carbon sequestration and, therefore, represent a negative climate feedback. Copyright 2009 by the American Geophysical Union.

  16. Stratigraphic Evidence for Environmental Change in a Bermudian Coastal Underwater Cave (Palm Cave System) in Response to Holocene Sea-level Rise

    NASA Astrophysics Data System (ADS)

    Cresswell, J. N.; van Hengstum, P. J.; Iliffe, T. M.

    2016-12-01

    Unique environments exist worldwide in coastal underwater caves, including those from Bermuda, which has been a global epicenter for interdisciplinary cave research. However, the development of environments, ecosystems, and sedimentary deposits in coastal underwater caves, particularly over millennial timescales is poorly understood, with previous research from Bermuda indicating a critical role for sea-level rise in driving environmental change. A multi-proxy stratigraphic analysis of 14 sediment cores that were collected from the Palm Cave System in Bermuda from 2 m to 20 m water depths was conducted to better understand Holocene-scale environmental change in coastal underwater caves (e.g., textural analysis, x-radiographs, microfossil analysis, radiocarbon dating). The rate of deposition was found to be variable throughout time and dependent upon the proximity of core locations to cave openings (`karst windows') and conduit geometry. The oldest recovered sediment was likely Pleistocene-aged, terra-rosa soil deposits that predate the Holocene inundation. By 9500 Cal yrs BP, deposition was dominated by organic-rich facies (gyttja), with agglutinated brackish foraminifera (Trochammina, Polysaccammina) and bivalves indicating brackish aquatic conditions in the system by 9200 Cal yrs BP. A system-wide shift to carbonate deposition occurred 8500 Cal yrs BP, which indicates the onset of oxygenated marine water entering the cave and development of a marine-dominated (i.e., submarine) cave environment. Comparison with local maximum sea-level indicators shows that inundation of the Bermuda platform by Holocene sea-level rise likely drove environmental change in the Palm Cave System.

  17. Stratigraphy of divers pleistocene dunefields of carbonate sands on Fuerteventura (Spain)

    NASA Astrophysics Data System (ADS)

    Roettig, Christopher-B.; Kolb, Thomas; Wolf, Daniel; Baumgart, Philipp; Richter, Christiane; Zöller, Ludwig; Faust, Dominik

    2016-04-01

    Correlating Quaternary dunefields in Northern Fuerteventura is a scientific challenge as reliable stratigraphic findings are only available for the Lajares-Dunefields (Faust et al., 2015). Over the last few years we added further important sites to better understand the system dynamics and characteristics. A detailed stratigraphy of dune-paleosol-sequences in four dunefields spanning the entire region of Northern Fuerteventura will be proposed. This study aims at correlating marker horizons across all investigated dunefields. The correlation is based on environmental magnetic findings, geochemical and granulometric analyses, elemental composition and finally on mollusk assemblages. We could identify guide assemblages of mollusks that enable us to trace marker horizons over long distances in all studied dune-paleosol-sequences. A first chronological assessment will be presented. Furthermore the question of soil forming intensity will be discussed considering the background of climate change vs. exposition duration.

  18. Holocene beach buildup and coastal aeolian sand incursions off the Nile littoral cell

    NASA Astrophysics Data System (ADS)

    Roskin, Joel; Sivan, Dorit; Shtienberg, Gilad; Porat, Naomi; Bookman, Revital

    2017-04-01

    Israel's coastal plain is abundant with sand originating from the Nile littoral cell. The inland windblown loose sand has formed 3-6 km wide lobe-like sand and dune fields currently comprised of foredunes, linear and northeasterly facing transverse and parabolic dunes that are currently stabilized by vegetation. This study reviews the architecture and history of the these dune fields aiming to: (a) Date the timings of beach accretion, and sand and dune incursions. (b) Discriminate between natural and human-induced forcing factors of sand mobilization and stabilization in time and space. (c) Present a model of the dunescape development. (d) Assess scenarios of sand transport in the future charcaterized by intense human impact and climate change. Luminescence ages, radiocarbon dates and relative ages from previously published geological and archaeological reports, historical texts, together with new optically stimulated luminescence (OSL) ages and stratigraphic and sedimentological data are analyzed. The deposition, mobilizations and preservation of the sand bodies, initially induced by the decline in sea level rise at 6-4 ka, were later controlled by historic land-use intensity and modern land-use/negligence practices. At 6 ka, beach sand buildup rapidly started. Where aeolianite ridges bordered the coast, pulses of sand with biogenic carbonate grains unconformably draped the ridges and rapidly consolidated into a distinct sandy calcarenite unit. Further east, sand sheets and low dunes partly pedogenized following their incursion, but did not cement. The water retention capacities of the sand sheets enabled the establishment of a sand-stabilizing vegetation cover that probably became an attractive environment for fuel and grazing. The growing Hellenistic-Roman-Byzantine ( 2.4-1.3 ka) populations probably led to increased consumption and massive destruction of sand stabilizing vegetation, enabling sand erodibility and mobilization during winter storms. The sand

  19. Long-term analysis of the role of Traganum moquinii plants in the foredune formation of an arid dunefield (Maspalomas, Gran Canaria, Canary Islands).

    NASA Astrophysics Data System (ADS)

    García-Romero, Leví; Hernández-Cordero, Antonio; Hernández-Calvento, Luis; Hesp, Patrick A.

    2017-04-01

    In recent decades, important environmental changes have been detected in dune systems around the world. Vegetation on the foredune provides stability to the coastal dunefields, capturing and accumulating sediments, which is an important function among other ecosystem services. For this reason, vegetation has been used as an indicator when studying anthropogenic and natural processes in the foredunes, especially when an increase of the vulnerability has been detected. Foredunes of arid dunefields have been little studied. They present significant differences with respect to the foredune of other climatic zones. Traganum moquinii is the predominant plant species in the foredune of arid dunefields around the Canary Islands (including South Morocco, Mauritania and other close archipelagos, like Cape Verde). This bush species plays an important geomorphological role: its interaction with the aeolian sedimentary processes generates nebkhas, shadow dunes and arid parabolic shaped dunes. The objective of this work is to show the morphometric evolution of the foredune of an arid dunefield of the Canary Islands, Maspalomas (Gran Canaria), as well as explaining the function of Traganum moquinii on it. One morphometric variable (number of nebkhas) and six morphologic variables of Traganum moquinii species (density, mean distance between Traganum moquinii individuals, number of Traganum moquinii individuals in line one, mean diameter of Traganum moquinii individuals in line one, mean distance between Traganum moquinii individuals in line one, density Traganum moquinii individuals in line one) have been measured in ten observation plots, from the 1960s to the present, through detailed historical aerial photographs and orthophotos, using GIS. The morphometric changes have been identified, and the variables have been related from statistical analysis to detect the function exerted by Traganum moquinii species in the foredune. The change in the number of nebkhas enables the

  20. Granulometric characterization and evaluation of annually banded mid-Holocene estuarine silts, Welsh Severn Estuary (UK): coastal change, sea level and climate

    NASA Astrophysics Data System (ADS)

    Allen, J. R. L.; Haslett, S. K.

    2006-07-01

    Holocene silts (salt marshes) and highest intertidal-supratidal peats are superbly exposed on a 15 km coastal transect which reveals two laterally extensive units of annually banded silts (Beds 3, 7) associated with three transgressive-regressive silt-peat cycles (early sixth-early fourth millennium BC). Bed 3 in places is concordantly and gradationally related to peats above and below, but in others transgresses older strata. Bed 7 also grades up into peat, but everywhere overlies a discordance. The banding in Bed 3 at three main and two minor sites was resolved and characterized texturally at high-resolution (2.5/5 mm contiguous slices) using laser granulometry (LS230 with PIDS) and a comprehensive scheme of data-assessment. Most of Bed 3 formed very rapidly, at peak values of several tens of millimetres annually, in accordance with modelled effects of sea-level fluctuations on mature marshes (bed concordant and gradational) and on marshes growing up after coastal erosion and retreat (bed with discordant base). Using data from the modern Severn Estuary, the textural contrast within bands, and its variation between bands, points to a variable but overall milder mid-Holocene climate than today. The inter-annual variability affected marsh dynamics, as shown by the behaviour of the finely divided plant tissues present. Given local calibration, the methodology is applicable to other tidal systems with banded silts in Britain and mainland northwest Europe.

  1. Automated mapping of linear dunefield morphometric parameters from remotely-sensed data

    NASA Astrophysics Data System (ADS)

    Telfer, M. W.; Fyfe, R. M.; Lewin, S.

    2015-12-01

    Linear dunes are among the world's most common desert dune types, and typically occur in dunefields arranged in remarkably organized patterns extending over hundreds of kilometers. The causes of the patterns, formed by dunes merging, bifurcating and terminating, are still poorly understood, although it is widely accepted that they are emergent properties of the complex system of interactions between the boundary layer and an often-vegetated erodible substrate. Where such dunefields are vegetated, they are typically used as extensive rangeland, yet it is evident that many currently stabilized dunefields have been reactivated repeatedly during the late Quaternary. It has been suggested that dunefield patterning and the temporal evolution of dunefields are related, and thus there is considerable interest in better understanding the boundary conditions controlling dune patterning, especially given the possibility of reactivation of currently-stabilized dunefields under 21st century climate change. However, the time-consuming process of manual dune mapping has hampered attempts at quantitative description of dunefield patterning. This study aims to develop and test methods for delineating linear dune trendlines automatically from freely-available remotely sensed datasets. The highest resolution free global topographic data presently available (Aster GDEM v2) proved to be of marginal use, as the topographic expression of the dunes is of the same order as the vertical precision of the dataset (∼10 m), but in regions with relatively simple patterning it defined dune trends adequately. Analysis of spectral data (panchromatic Landsat 8 data) proved more promising in five of the six test sites, and despite poor panchromatic signal/noise ratios for the sixth site, the reflectance in the deep blue/violet (Landsat 8 Band 1) offers an alternative method of delineating dune pattern. A new edge detection algorithm (LInear Dune Optimized edge detection; LIDO) is proposed, based on

  2. Reconstruction of Holocene coastal foredune progradation using luminescence dating — An example from the Świna barrier (southern Baltic Sea, NW Poland)

    NASA Astrophysics Data System (ADS)

    Reimann, Tony; Tsukamoto, Sumiko; Harff, Jan; Osadczuk, Krystyna; Frechen, Manfred

    2011-09-01

    Two sandy spits on the Świna barrier (Wolin and Uznam) provide a very detailed succession of Holocene coastal foredunes and dunes and are regarded as key sites along the southern Baltic Sea coast. Optically Stimulated Luminescence (OSL) dating is proven to be a powerful tool for the reconstruction of Holocene coastal spit evolution and foredune accretion; quartz extracted from the coastal sediments in the study area provides excellent properties for OSL dating. The OSL age from the innermost dune indicates that spit development of the Świna barrier started immediately after rapid sea-level rise of the Littorina transgression decelerated at ~ 6.6 ka. A significant change in the foredune progradation rate occurred during the late Subatlantic transgression at ~ 1.2 ka (800 AD), when migration rates decreased from 2.6 ± 0.7 m a - 1 to 1.3 ± 0.4 m a - 1 . Progradation accelerated again during the "Little Ice Age" between 1550 and 1850 AD. The systematic dating of 28 samples reveals six hiatuses during foredune succession, at ~ 2100 BC, ~ 900 BC, 200 BC-200 AD, ~ 600 AD, ~ 1000 AD, and ~ 1600 AD. The timing of these hiatuses correlates with the phases of transgressive dune development in the surrounding area (Troszyn and Świna) and with phases of increased aeolian activity in other parts of North- and West-Europe. We conclude that four of these phases of foredune erosion/instability and aeolian sediment mobilisation were caused by general climate shifts to cooler and stormier conditions at ~ 2200 BC, ~ 900 BC, ~ 600 AD, and at ~ 1600 AD, the latter corresponding to the "Little Ice Age". The period of increased aeolian activity around 1000 AD is probably to a phase of intensive forest clearance in Central Europe. In contrast, the systematic foredune accretion and foredune plain growth correlates to periods of positive sediment budget, milder and calmer climate, and an intact vegetation cover.

  3. Spatial and Temporal Complexities of Current Great Plains Dunefield Chronological Data

    NASA Astrophysics Data System (ADS)

    Halfen, A. F.; Johnson, W. C.

    2012-12-01

    The North American Great Plains span nearly 2.8 million km2, of which nearly half is mantled by aeolian sediments (loess deposits, sand sheets, and dunefields). Stratigraphies of these sediments contain a rich history of late-Quaternary climate change, in particular aeolian dunefields, which provide a record of drought. During arid conditions in the Great Plains, stabilizing vegetation is diminished, leaving dunefields susceptible to aeolian erosion; during periods of increased moisture, conversely, vegetation re-establishes and dunefields stabilize. Using radiometric dating techniques, researchers can extract from the stratigraphy of dunefields the timing of past activity, and, therefore, periods of past drought. To date, more than 50 chronologies, comprised of over 700 ages, have established a detailed record of past dunefield activity in the Great Plains. Despite this extensive dataset, correlating periods of past droughts across the region remains problematic, in large part due to the spatial and temporal limitations in the data. In this poster, we present a spatial and temporal synthesis of current Great Plains dunefield chronologies, followed by an analysis of the complexities of these data, in particular when used to determine periods of past drought. To illustrate these complexities, we present a bicentennial, 1 x 1 degree gridded model of dune activity (e.g., active, stable, no data) spanning the last 2000 years. Our model clearly illustrates gaps in spatial coverage and temporal biases of chronologies. To further highlight the complexities of using current Great Plains datasets as proxies for prehistoric drought, we compare a 2.5 x 2.5 degree gridded model of dune activity during the Medieval Climatic Anomaly (A.D. 1000-1400) and historic time (A.D. 1800-2000) to Palmer Drought Severity Index (PDSI)-reconstructed droughts for the same time intervals. In general, dunefield activity is in good agreement with PDSI-reconstructed drought, however, unlike tree

  4. High-resolution reconstruction of extreme storm events over the North Sea during the Late Holocene: inferences from aeolian sand influx in coastal mires, Western Denmark.

    NASA Astrophysics Data System (ADS)

    Goslin, Jerome; Clemmensen, Lars B.

    2017-04-01

    Possessing long and accurate archives of storm events worldwide is the key for a better understanding of the atmospheric patterns driving these events and of the response of the coastal systems to storms. To be adequately addressed, the ongoing and potential future changes in wind regimes (including in particular the frequency and magnitude of storm events) have to be replaced in the context of long-time records of past storminess, i.e. longer than the century-scale records of instrumental weather data which do not allow the calculation of reliable return periods. During the last decade, several Holocene storminess chronologies have been based on storm-traces left by aeolian processes within coastal lakes, mires and peat bogs, (e.g. Björck and Clemmensen, 2004; De Jong et al., 2006; Clemmensen et al., 2009; Nielsen et al.; 2016; Orme et al., 2016). These data have shown to adequately complement the records which can be derived from the study of records related to wave-induced processes including e.g. washover deposits. Previous works along the west coast of Jutland, Denmark have revealed four main periods of dune building during the last 4200 yrs (Clemmensen et al., 2001; 2009). These were shown to be in phase with periods of climate deterioration (cold periods) recognized elsewhere in Europe and the North Atlantic region and suggest periods of increased aeolian activity. Yet, doubts remain on whether these periods where characterized by several big short-lived storm events or rather by an overall increase in wind energy. This study aims at constructing a high-resolution (centennial to multi-decadal) history of past storminess over the North Sea for the last millenaries. Plurimeter sequences of peat and gyttja have been retrieved from two coastal mires and were analyzed for their sand content. The quartz grains were systematically counted within centimetric slices (Aeolian Sand Influx method, Björck & Clemmensen, 2004), while the palaeo-environmental context and

  5. Coastal lagoon systems as indicator of Holocene sea-level development in a periglacial soft-sediment setting: Samsø, Denmark

    NASA Astrophysics Data System (ADS)

    Sander, Lasse; Fruergaard, Mikkel; Johannessen, Peter N.; Morigi, Caterina; Nielsen, Lars Henrik; Pejrup, Morten

    2014-05-01

    lagoon systems a valuable archive for the reconstruction of Holocene sea-level and coastal evolution.

  6. Sediment connectivity at source-bordering aeolian dunefields along the Colorado River in the Grand Canyon, USA

    NASA Astrophysics Data System (ADS)

    Sankey, Joel; Kasprak, Alan; Caster, Joshua; East, Amy; Fairley, Helen

    2017-04-01

    Aeolian dunefields that are primarily built and maintained with river-derived sediment are found in many river valleys throughout the world and are impacted by changes in climate, land use, and river regulation. Quantifying the dynamic response of these aeolian dunefields to alterations in river flow is especially difficult given the highly correlated nature of the interacting geomorphic and sediment transport processes that drive their formation and maintenance. We characterize the effects of controlled river floods on changes in sediment connectivity at source-bordering aeolian dunefields in the Grand Canyon, USA. Controlled floods from the Glen Canyon Dam are used to build sandbars along the Colorado River in Grand Canyon which provide the main sediment source for aeolian dunefields. Aeolian dunefields are a primary resource of concern for land managers in the Grand Canyon because they often contain buried archaeological features. To characterize dunefield response to controlled floods, we use a novel, automated approach for the mechanistic segregation of geomorphic change to discern the geomorphic processes responsible for driving topographic change in very high resolution digital elevation models-of-difference (DODs) that span multiple, consecutive controlled river floods at source-bordering dunefields. We subsequently compare the results of mechanistic segregation with modelled estimates of aeolian dunefield evolution in order to understand how dunefields respond to contemporary, anthropogenically-driven variability in sediment supply and connectivity. These methods provide a rapid technique for sediment budgeting and enable the inference of spatial and temporal patterns in sediment flux between the fluvial and aeolian domains. We anticipate that this approach will be adaptable to other river valleys where the interactions of aeolian, fluvial, and hillslope processes drive sediment connectivity for the maintenance of source-bordering aeolian dunefields.

  7. Holocene soil-geomorphic surfaces influence the role of salmon-derived nutrients in the coastal temperate rainforest of Southeast Alaska

    NASA Astrophysics Data System (ADS)

    D'Amore, David V.; Bonzey, Nicholas S.; Berkowitz, Jacob; Rüegg, Janine; Bridgham, Scott

    2011-03-01

    The influence of salmon-derived nutrients (SDN) is widely accepted as a potential factor in the maintenance of aquatic and terrestrial productivity in North American Coastal rainforests. Holocene alluvial landforms are intimately connected with the return of anadromous salmon, but the influence of the soils that occupy these landforms and support this important terrestrial-aquatic ecological coupling have not been examined in SDN studies. We used paleo-ecologic information, soil resource inventories and measurements of soil morphology to construct a soil-geomorphic model for alluvial landforms along salmon spawning channels on Prince of Wales Island, Southeast Alaska, USA. Post-glacial sea-level rise, crustal uplift and subsidence combined with Holocene sediment deposition have formed alluvial terraces and floodplains along rivers on Prince of Wales Island. These alluvial landforms have soils that are mapped as Entisols (Tonowek soil series) and Spodosols (Tuxekan soil series). We propose a soil-geomorphic model where the Spodosols located on terraces are estimated to derive from sediments deposited after the stabilization of landscape approximately 8 kybp to 6 kybp. The stability of these soils is reflected through mature soil development with organic matter accumulation and podzolization. Our model identifies Entisols on floodplains developed from alluvial deposition in the latter Holocene that have soil morphologic features consistent with recent deposition and limited soil development. We used this soil-geomorphic model to test the hypothesis that the terrestrial end-member value commonly used to quantify nitrogen (N) loading on soils through stable isotope analysis differs by soil type and found that the two soil types had significantly different N isotopic ( δ15N) values more consistent with soil development than SDN loading. The use of a soil-geomorphic model provides a means to stratify alluvial landforms and constrain the natural variability encountered

  8. Late-Holocene to recent evolution of Lake Patria, South Italy: An example of a coastal lagoon within a Mediterranean delta system

    NASA Astrophysics Data System (ADS)

    Sacchi, M.; Molisso, F.; Pacifico, A.; Vigliotti, M.; Sabbarese, C.; Ruberti, D.

    2014-06-01

    Lake Patria is a mesoaline coastal lagoon that develops along the coastal zone of the Volturno River plain (Campania, South Italy). The lagoon is a saline to brackish water body, ca. 2.0 long, and 1.5 km wide, with an average water depth of 1.5 m, reaching a maximum of ca. 3.0 m. The freshwater input into the lagoon is provided by a series of fresh to brackish water channels and small springs, landwards, while a permanent connection with the Tyrrhenian Sea is provided by a channel, 1.5 km long and a few meters wide. Drilling data from 12 boreholes acquired in the study area indicate that Lake Patria is a man-modified remnant of a larger lagoonal area that developed during the last millennia along the Campania coastal zone within an alluvial delta system at the mouth of the paleo-Volturno River. Sedimentological and stratigraphic analyses of drill cores suggest that the lower Volturno delta plain developed in the last 6000 years. Depositional conditions during this period were dominated by flood-plain and alluvial plain settings, with transition to coastal bars and associated back-barrier coastal lagoons. Lake Patria started evolving at an early stage of the Volturno delta plain formation as a consequence of foreshore deposits damming-up by littoral drift. The first marine layers display a radiocarbon age of ca. 4.8 ka BP and overlie a substrate represented by volcaniclastic deposits, originated by the Campi Flegrei, and associated paleosols. The lagoonal succession cored at Lake Patria may be interpreted as the result of a dynamic equilibrium between marine influence and riverine input into the lagoonal system through time, and has been tentatively correlated with the major climatic changes that occurred during Mid-Late Holocene. Insights into the recentmost evolution of the coastal lagoon of Lake Patria are provided by the GIS-based analysis of the physiographic changes of the region conducted on a series of historical topographic maps dating back to the early

  9. Continuous coastal subsidence during the Holocene along a source region of the 2011 great Tohoku-oki, Japan, earthquake revealed from new paleo-geodetic data

    NASA Astrophysics Data System (ADS)

    Niwa, Y.; Toda, S.; Sugai, T.

    2015-12-01

    Time-dependent inconsistency of crustal movement is suggested in the Sanriku coast, northeast Japan. In northern Sanriku, coseismic subsidence up to 0.4 m of the 2011 M=9.0 Tohoku-oki earthquake and a century-long subsidence apparently contradict to long-term uplift estimated from Pleistocene marine terraces. To explain the inconsistency, the following hypotheses have been proposed: 1) the 2011 event was typical, contributing long-term (104 yr) subsidence, 2) a significant interseismic contribution to long-term uplift, or 3) unknown huge events may have occurred to uplift the coastal region. However, in the southern Sanriku, closer to the 2011 source, poorly distributed marine terraces do not allow us to confirm the long-term uplift. We instead focus on the coastal plains that preserve sediments recording the tectonic history with better age constraints. We extracted 40 m-long samples of the Holocene sediments in the Rikuzen-takata and Kesennuma-Okawa plains, along the southern Sanriku. The two plains share sedimentary facies of river, estuary, and delta. At both sites, relative sea-level (RSL) from 10 to 9.0 ka estimated from altitude of intertidal deposits is significantly lower than the theoretical none-tectonic RSL. We interpret that this discrepancy is attributed to Holocene tectonic subsidence. Observed Holocene subsidence is consistent with 2011 coseismic and a century-long subsidence. This long-term subsidence possibly suggests that the southern Sanriku has been submerged by both the 2011 type coseismic and interseismic deformation on the 104 yr time-scale. A significant difference is their rates: long-term subsidence rate of ~1 mm/yr is slower than a century-long rate of 1-10 mm/yr. However, it may be accommodated with the recovery from the ongoing postseismic and continuous potential interseismic uplift. We thus argue that there is no reason to include tectonic contribution from unknown, different type megathrust earthquakes to form the southern Sanriku.

  10. The origin and disappearance of the late Pleistocene-early Holocene short-lived coastal wetlands along the Carmel coast, Israel

    NASA Astrophysics Data System (ADS)

    Sivan, Dorit; Greenbaum, Noam; Cohen-Seffer, Ronit; Sisma-Ventura, Guy; Almogi-Labin, Ahuva

    The formation of short-lived backswamps along the Carmel coast of Israel coincides with the rapid global sea-level rise during the late Pleistocene-early Holocene transition. The current study shows that the wetland phenomena originated around 10,000 yr ago and dried up shortly before the local Pre-Pottery Neolithic humans settled on the wetland dark clay sediments 9430 cal yr BP. Palaeontological and stable-isotope data were used in this study to elucidate previously published sedimentological reconstruction obtained from a core drilled into the western trough of the Carmel coastal plain. The water body contained typical brackish calcareous fauna, with variable numerical abundance and low species richness of ostracods and foraminifera. The δ 18O and δ 13C of the ostracod Cyprideis torosa show close similarity to the present Pleistocene coastal aquifer isotopic values. This study therefore concludes that the wetlands were shallow-water bodies fed by groundwater, with no evidence of sea-water mixing. It seems that they developed as the result of high groundwater levels, transportation of sediments landward, and deposition of sand bars at the paleo-river mouths. It is still not fully understood why these wetlands deteriorated abruptly and disappeared within less than 1000 yr.

  11. Trickle-down boundary conditions in aeolian dune-field pattern formation

    NASA Astrophysics Data System (ADS)

    Ewing, R. C.; Kocurek, G.

    2015-12-01

    One the one hand, wind-blown dune-field patterns emerge within the overarching boundary conditions of climate, tectonics and eustasy implying the presence of these signals in the aeolian geomorphic and stratigraphic record. On the other hand, dune-field patterns are a poster-child of self-organization, in which autogenic processes give rise to patterned landscapes despite remarkable differences in the geologic setting (i.e., Earth, Mars and Titan). How important are climate, tectonics and eustasy in aeolian dune field pattern formation? Here we develop the hypothesis that, in terms of pattern development, dune fields evolve largely independent of the direct influence of 'system-scale' boundary conditions, such as climate, tectonics and eustasy. Rather, these boundary conditions set the stage for smaller-scale, faster-evolving 'event-scale' boundary conditions. This 'trickle-down' effect, in which system-scale boundary conditions indirectly influence the event scale boundary conditions provides the uniqueness and richness of dune-field patterned landscapes. The trickle-down effect means that the architecture of the stratigraphic record of dune-field pattern formation archives boundary conditions, which are spatially and temporally removed from the overarching geologic setting. In contrast, the presence of an aeolian stratigraphic record itself, reflects changes in system-scale boundary conditions that drive accumulation and preservation of aeolian strata.

  12. Quantifying the role of urbanization on airflow perturbations and dunefield evolution

    NASA Astrophysics Data System (ADS)

    Smith, Alexander B.; Jackson, Derek W. T.; Cooper, J. Andrew G.; Hernández-Calvento, L.

    2017-05-01

    Rapid urban development has been widespread in many arid regions of the world during the Anthropocene. Such development has the potential to affect, and be affected by, local and regional dunefield dynamics. While urban design often includes consideration of the wind regime, the potential impact of construction on the surrounding environment is seldom considered and remains poorly understood. In this study, regional airflow modeling during successive stages of urbanization at Maspalomas, Gran Canaria, Spain, indicates significant and progressive flow perturbations that have altered the adjacent dunefield. Significant modifications to the boundary layer velocity, mean wind directionality, turbulence intensity, and sediment flux potential are attributed to the extension of the evolving urban geometry into the internal boundary layer. Two distinct process/response zones were identified: (1) the urban shadow zone where widespread dune stabilization is attributed to the sheltering effect of the urban area on surface wind velocity; and (2) the acceleration zone where airflow is deflected away from the urbanized area, causing an increase in sediment transport potential and surface erosion. Consistent coherent turbulent structures were identified at landform and dunefield scales: counter-rotating vortices develop in the lee-side flow of dune crests and shedding off the buildings on the downwind edge of the urban area. This study illustrates the direct geomorphic impact of urbanization on aeolian dunefield dynamics, a relationship that has received little previous attention. The study provides a template for investigations of the potential impact of urbanization in arid zones.

  13. Preservation of Paleoseismic and Paleogeodetic Records of mid to late Holocene Subduction Zone Earthquakes in Different Coastal Settings

    NASA Astrophysics Data System (ADS)

    Kelsey, H. M.; Horton, B.; Rubin, C. M.; Grand Pre, C.; Hawkes, A. D.; Dura, T.; Daryono, M.; Ladinsky, T.

    2009-12-01

    Dynamic variations in sea level and solid Earth properties along active subduction zones predetermine the duration and when paleoseismic and paleogeodetic records will be preserved in coastal regions. The most direct, reliable way to chronicle the history of past subduction zone earthquakes is through coastal stratigraphic sequences that preserve abrupt and gradual relative sea level changes caused by great subduction earthquake cycles. Specifically, paleoseismic timing and paleo geodetic determination of vertical displacement can be obtained through the application of litho-, bio- and chronostratigraphic analyses of selected coastal stratigraphic sequences. Such stratigraphic sequences are only preserved under a specific set of conditions wherein sea level rise, crustal loading, local crustal thickness and imposed strain accumulation and release from megathrust and upper plate faults and folds collectively conspire to provide a long-term, gradual relative sea level rise over millenia that span at least two or three subduction earthquake cycles. Given the conditions necessary to preserve stratigraphic sequences recording multiple great subduction earthquake cycles, it is not surprising that robust paleoseismic records from coastal marsh stratigraphies are rare. To illustrate the conditions under which coastal marshes preserve paleoseismic records of great subduction zone earthquakes, we present two sites with different combinations of sea level rise, crustal loading, crustal thickness and local tectonics. Although both sites preserve a paleoseismic record of subduction zone earthquakes, the length of the records and the specific time range of the records are notably different. The coastal, equatorial, island tropical setting in the Indian Ocean preserves tidal-marsh stratigraphic records of great subduction zone earthquakes in the time window 7-5 ka. In contrast, mid-latitude, North American, northeast Pacific coastal settings preserve tidal-marsh stratigraphic

  14. Systematic vertical and lateral changes in quality and time resolution of the macrofossil record: insights from Holocene transgressive deposits, Po coastal plain, Italy

    NASA Astrophysics Data System (ADS)

    Azzarone, Michele; Scarponi, Daniele; Kusnerik, Kristopher; Amorosi, Alessandro; Bohacs, Kevin M.; Drexler, Tina M.; Kowalewski, Michał

    2017-04-01

    In siliciclastic marine settings, skeletal concentrations are a characteristic feature of transgressive intervals that provide insights into paleobiology and sequence stratigraphy. To investigate taphonomic signatures of transgressive intervals, we analyzed three cores from a Holocene depositional profile of the Po coastal plain, in northern Italy. Coupled multivariate taphonomic and bathymetric trends delineate spatial and temporal gradients in sediment starvation/bypassing, suggesting that quality and resolution of the fossil record vary predictably along the studied depositional profile. Moreover, joint consideration of taphonomic, bathymetric, and fossil density trends across the study area reveals distinctive signatures that are useful in characterizing facies associations and recognizing surfaces and intervals of sequence stratigraphic significance. Within the southern Po plain succession, taphonomic degradation of macroskeletal remains increases from proximal—nearshore to distal—offshore locations. This trend is discernible for both biologically-driven (bioerosion) and chemically/physically-driven (e.g., dissolution, abrasion) shell alterations. Compared to the up-dip (most proximal) core, the down-dip core is distinguished by shell-rich lithosomes affected by ecological condensation (co-occurrence of environmentally non-overlapping taxa) and by higher taphonomic alteration. The onshore-offshore taphonomic trend likely reflects variation in sediment-supply along the depositional profile of the Holocene Northern Adriatic shelf, with surface/near-surface residence-time of macroskeletal remains increasing down dip due to lower accumulation rates. These results indicate that, during transgressive phases, changes in sea-level (base level) are likely to produce down-dip taphonomic gradients across shelves, where the quality and resolution of the fossil record both deteriorate distally. The amino acid radiometrically calibrated dates on bivalves and the

  15. Redox Effects on Organic Matter Storage in Coastal Sediments During the Holocene: A Biomarker/Proxy Perspective

    NASA Astrophysics Data System (ADS)

    Bianchi, Thomas S.; Schreiner, Kathryn M.; Smith, Richard W.; Burdige, David J.; Woodard, Stella; Conley, Daniel J.

    2016-06-01

    Coastal margins play a significant role in the burial of organic matter (OM) on Earth. These margins vary considerably with respect to their efficiency in OM burial and to the amounts and periodicity of their OM delivery, depending in large part on whether they are passive or active margins. In the context of global warming, these coastal regions are expected to experience higher water temperatures, changes in riverine inputs of OM, and sea level rise. Low-oxygen conditions continue to expand around the globe in estuarine regions (i.e., hypoxic zones) and shelf regions (i.e., oxygen minimum zones), which will impact the amounts and sources of OM stored in these regions. In this review, we explore how these changes are impacting the storage of OM and the preservation of sedimentary biomarkers, used as proxies to reconstruct environmental change, in coastal margins.

  16. Natural and human controls of the Holocene evolution of the beach, aeolian sand and dunes of Caesarea (Israel)

    NASA Astrophysics Data System (ADS)

    Roskin, J.; Sivan, D.; Shtienberg, G.; Roskin, E.; Porat, N.; Bookman, R.

    2015-12-01

    The study focuses on the Holocene appearance, chronology and drivers of beach sand deposition and inland aeolian sand transport around the Roman-Byzantine ruins of Caesarea, Israel. Beach sand, sand sheets, nebkha, linear and transverse dunes as well as parabolic and transverse interdunes along two transects were sampled in the current study down to their substrate. Sixteen new optically stimulated luminescence ages cluster at ∼5.9-3.3 ka, ∼1.2-1.1 ka (800-900 AD) and ∼190-120 years ago (1825-1895 AD) indicating times of middle and late Holocene sand sheet depositions and historical dune stabilization. The first age cluster indicates that beach sand accumulated when rates of global sea level rise declined around 6-5 ka. Until ∼4 ka sand sheets encroached up to 2.5 km inland. Historical and archaeological evidence points to sand mobilization since the first century AD. Sand sheets dating to 1.2-1.1 ka, coevally found throughout the dunefield represent sand stabilization due to vegetation reestablishment attributed to gradual and fluctuating decline in human activity from the middle Early Islamic period until the 10th century. Historical and chronological evidence of the existence of transverse and coppice dunes from the 19th century suggest that dunes only formed in the last few centuries. The study illustrates the initial role of natural processes, in this case decline in global sea level rise and the primary and later role of fluctuating human activity upon coastal sand mobility. The study distinguishes between sand sheets and dunes and portrays them as sensors of environmental changes.

  17. Amino acid racemization analysis (AAR) as a successful tool for dating Holocene coastal sediments: Stratigraphy of a barrier island spit (Southern Sylt/North Sea)

    NASA Astrophysics Data System (ADS)

    Tillmann, Tanja; Ziehe, Daniel

    2014-05-01

    Dating of Holocene sediments in shallow coastal areas of the German North Sea by conventional techniques is commonly problematic. In particular the marine reservoir effect of radiocarbon means that radiocarbon dating cannot be applied to sediments younger than about 400 years. Amino acid racemization dating (AAR) is a viable alternative for dating young sediments. The method is based on the determination of ratios of D and L amino acid enantiomers in organic matrices of biogenic carbonates. In this study we use AAR as a tool for dating Holocene barrier islands sediments. Based on an AAR derived chronological framework we develop a model of barrier spit accretion which describes the interaction between extreme events, fair weather coastal processes and sedimentary development that constrains the major episodes of barrier island evolution. The stratigraphy was defined using ground-penetrating radar (GPR) surveys complemented by sedimentological coring data. The stratigraphy is then conceptualised in a AAR chronostratigraphic framework to define a chronological order and allow the development of a stratigraphic model of the evolution of Southern Sylt. The AAR data provide high temporal resolution and have been used for dating stages of barrier spit accretion. The time lines are marked as storm surge generated erosion unconformities in the stratigraphic profile. Individual shells and shell fragments of Cerastoderma edule, Mya arenaria, Mytilus edulis and Scrobicularia plana have been accumulated by short-term storm events as shell layers associated with the erosion unconformities and have been dated by AAR. Time lines reveal that the barrier spit accretion occurred episodically, and is dependant on the provided rate of sand delivery. The general trend is that sequences young to the. South. The AAR derived time lines have been verified and correlated by historic maps and sea charts. It is apparent that spit enlargement at this site increased significantly during the

  18. Holocene palaeoclimate and sea level fluctuation recorded from the coastal Barker Swamp, Rottnest Island, south-western Western Australia

    NASA Astrophysics Data System (ADS)

    Gouramanis, C.; Dodson, J.; Wilkins, D.; De Deckker, P.; Chase, B. M.

    2012-10-01

    The Holocene palaeoclimatic history of south-western Western Australia (SWWA) has received little attention compared to south-eastern Australia, and this has resulted in conflicting views over the impact of climate variability in the region. We present here a well-dated, high-resolution record from two overlapping sediment cores obtained from the centre of Barker Swamp, Rottnest Island, offshore Perth. The records span the last 8.7 ka, with the main lacustrine phase occurring after 7.4 ka. This site preserves both pollen and several ostracod taxa. The pollen record suggests a long-term shift from the early-mid Holocene to the late Holocene to drier conditions with less shrubland and more low-ground cover and less fire activity. A salinity transfer function was developed from ostracod faunal assemblage data and trace metal ratios (Mg/Ca, Sr/Ca and Na/Ca) and stable isotopes (δ18O and δ13C) analysed on selected ostracod valves. These provide a detailed history of evaporation/precipitation (E/P) differences that clearly shows that the SWWA region was subjected to significant climatic shifts over the last 7.4 ka, with a broad shift towards increased aridity after 5 ka. The swamp ranged from fresh to saline as recorded in the ostracod valve chemistry and the independently-derived salinity transfer function. The ostracod record also indicates that a sea-level highstand occurred between ca. 4.5 and 4.3 ka, with probable step-wise increases at 6.75, 6.2, and 5.6 ka, with the last vestiges of salt water intrusion at ca. 1 ka. After about 2.3 ka, the fresh, groundwater lens that underlies the western portion of the island intersected the swamp depression, influencing the hydrology of the swamp. The broad climatic changes recorded in Barker Swamp are also compared with data from southern South Africa, and it is suggested that the Southern Annular Mode appears to have been the dominant driver in the climate of these regions and that the Indian Ocean Dipole is of little

  19. Coastal response to accelerated sea-level rise (>4 mm/yr) based on early-mid Holocene coastal evolution in the northwestern Gulf of Mexico

    NASA Astrophysics Data System (ADS)

    Anderson, J. B.; Rodriguez, A. B.; Simms, A.

    2009-12-01

    There is growing consensus that the rate of sea level rise by the end of this century will reach, and possibly exceed, 5 mm/yr. Predictions as to how sea-level rise will impact coasts often rely on passive inundation models that simply flood the coastal landscape. However, the geological record clearly shows that coastal response to past sea-level rise was more complex, mainly due to differences in sediment supply and subsidence. Ultimately, coastal submergence and erosion depend on whether coastal environments are capable of aggrading as fast as sea-level rises, and this is largely dependent on sediment supply and, in the case of wetlands, vegetation growth. It has been 7000 years since sea level was rising at a rate of 5 mm/yr in the northern Gulf of Mexico. After approximately 4000 cal yrs BP the rate of rise decreased to less than 1 mm/yr. The rate has more than doubled in historical time. An analysis of shoreline and bayline change in Texas and western Louisiana during the past 9000 years shows that coastal retreat was quite episodic, with episodes of widespread and pronounced change that lasted a few centuries. During these episodes, the larger bays of the region (Calcasieu Lake, Sabine Lake, Galveston Bay, Matagorda Bay and Corpus Christi Bay) experienced major re-organization of estuarine environments. Within the limits of radiocarbon precision (a few centuries due to poorly constrained regional carbon reservoir variations) these events appear to have been contemporaneous. This begs the question, where these events caused by short-lived increases in the rate of rise or do they reflect a threshold response of coastal systems to an overall rise that averaged 4.0 mm/yr? This was a time when the West Antarctic ice sheet was experiencing its final stages of retreat from the inner continental shelf and inland passages, which could have resulted in rapid sea-level events of a few decimeters, below the resolution of Gulf of Mexico sea-level curves. These results

  20. Evolution of the siliciclastic-carbonate shelf system of the northern Kenyan coastal belt in response to Late Pleistocene-Holocene relative sea level changes

    NASA Astrophysics Data System (ADS)

    Accordi, Giovanni; Carbone, Federico

    2016-11-01

    A classification of depositional environments of the Lamu Archipelago is proposed based on a sedimentary facies analysis of unconsolidated and hard bottoms of the study area. The genesis of the siliciclastic-carbonate depositional pattern, typical of this East African region, is closely related both to the presence of a quartz-dominate Pleistocene riverine net-flooded during the Holocene sea level rise-and to the coeval development on the shallow shelf of a coral ecosystem producing vast skeletal sediments. The present facies pattern originates from the variable contribution in time and space of three sediment types: skeletal carbonate, quartz and palimpsest debris. The facies analysis allowed to distinguish 10 depositional facies and to differentiate them into three main types of substratum: soft bottom, reefal hard bottom and non-reefal hard bottom. These three types define both the loose facies typical of the channelized coastal belt and several facies of the shallow shelf. In the first, the amounts and textures of the stored sediment are strictly related to three major geomorphic types of substratum: sheltered mangal flat, shallow channel and deep channel. In the second and the third, a wide range of textures is related to coastal flats, benches, islets and emerging rocks. This modern facies pattern is implemented through a series of evolutionary phases: i-during the Last Interglacial Period, since isotope substage 5b, the shallow shelf-above -20 m-is permanently exposed for about 80 ka, with erosion, karstification and cuts of river channels through the shelf; ii-after the Last Glacial Maximum, when the sea level fell to about 110-115 m b.p.s.l. (below present sea level) at 18-17 ka BP, the sea level rose at -20 m for about 9 ka, flooding the shallow shelf area and gradually drowning the riverine net; iii-the maximum flooding of the coastal belt was reached at about 4.5 ka BP, when a gradual moisture reduction caused a decrease of siliciclastic sediment supply

  1. A review of the chronologies and geomorphology of the aeolian landforms in the northwestern Negev dunefield (Israel)

    NASA Astrophysics Data System (ADS)

    Roskin, Joel

    2015-04-01

    The northwestern (NW) Negev Desert dunefield covering an area of only 1,300 km2, comprises the eastern end of the northern Sinai Peninsula - NW Negev erg and is probably the most densely dated dune body in the INQUA Dunes Atlas chronologic database. Over 230 luminescence ages (TL, IRSL, and mainly OSL) and radiocarbon dates have been retrieved over the past course of 20 years from calcic and sandy palaeosols serving as dune substrates, sand sheets, vegetated linear dunes (VLDs), fluvial deposits, and archaeological sites. Despite being from different deposit types and aeolian morphologies, and based on different methodologies, the chronologies usually show good compatibility. By reviewing and reassessing the significance of the Eastern Mediterranean INQUA Dunes Atlas chronologies, along with detailed stratigraphic, structural and geomorphologic data and understandings, the major, and possibly extreme, episodes of aeolian activity and stability are outlined. Repetitive chronostratigraphic sequences in VLDs indicate that this dune type, at least in the Negev, comprises a reliable recorder of main dune mobilization periods. This presentation demonstrates that certain combinations of research finds, using different OSL dating strategies and other regional and local late Quaternary records and in particular aeolian ones, are required assets for providing for acceptable local and regional palaeoclimatic interpretations. The distribution of the VLD chronologies points to rapid mobilization during the Heinrich 1 and Younger Dryas, characterized by powerful winds, though VLDs also form in late Holocene palaeoenvironments. Time slices illustrate the different sensitivities of the studied aeolian landforms to the source, availability, and supply of sediment; long- and short-term climate change, local human-induced environmental changes and also their joint effects, that enable evaluation of aeolian responses to future environmental and climate changes.

  2. Middle Holocene coastal environment and the rise of the Liangzhu City complex on the Yangtze delta, China

    NASA Astrophysics Data System (ADS)

    Liu, Yan; Sun, Qianli; Thomas, Ian; Zhang, Li; Finlayson, Brian; Zhang, Weiguo; Chen, Jing; Chen, Zhongyuan

    2015-11-01

    The large prehistoric city of Liangzhu and its associated earthen dike emerged on the Yangtze delta-coast after two millennia of occupation in this area by scattered communities. Details of its development have been widely discussed in the literature. Our results reveal that the city was selectively built at the head of an embayment backed by hills, with close access to food, freshwater and timber, and with protection from coastal hazards. Radiocarbon and optically stimulated luminescence (OSL) dating shows that it was built around 4.8-4.5 ka, and the earthen dike was constructed a little later at 4.1 ka. During this time, saltwater wetlands were changing to freshwater in response to rapid coastal progradation as the postglacial sea-level rise stabilized. This facilitated rice farming and furthered the development of the city with elaborate city planning. The younger large-scale earthen dike and artificial ponds possibly suggest increasing demand for flood mitigation and irrigation.

  3. Holocene marine hardground formation in the Arabian Gulf: Shoreline stabilisation, sea level and early diagenesis in the coastal sabkha of Abu Dhabi

    NASA Astrophysics Data System (ADS)

    Paul, Andreas; Lokier, Stephen W.

    2017-05-01

    This study provides the first comparison between a seaward and a landward section of the same diachronous hardground surface observed in the coastal sabkha of Abu Dhabi. This hardground is described here in terms of its mode of formation, its diagenetic environment and its impact on shoreline stabilisation during transgression. The hardground is exposed in the intertidal zone and buried by a late Holocene prograding succession of carbonates, evaporites and microbial sediments in the supratidal zone. The hardground itself is composed of bioclastic grains, primarily of aragonitic composition, that originate from intertidal depositional environments. Aeolian silt to sand-sized quartz grains are also observed. Lithification occurred through the precipitation of pore-filling aragonite, high-Mg calcite and dolomite cements from sea and interstitial water that was marked by high salinities and temperatures, as confirmed by stable isotope analyses. High-Mg calcite and non-stoichiometric dolomite are also observed as secondary recrystallisation products. The formation of these two mineral phases as recrystallisation products was possibly microbially-mediated. Lithification progressed in two phases, the older phase of which is marked by higher amounts of non-stoichiometric dolomite and high-magnesium calcite as compared to the younger phase. Transgressive reworking of precursor siliciclastic sands was inhibited by the development of transgressive pore-filling gypsum cements in the supratidal zone.

  4. Holocene sedimentation and coastal wetlands response to rising sea level at the Aucilla river mouth, a low energy coast in the Big Bend area of Florida

    USGS Publications Warehouse

    Garrett, Connie; Hertler, Heidi; Hoenstine, Ronald; Highley, Brad

    1993-01-01

    The shallow dip of the Florida carbonate platform results in low wave energy on Florida ???Big Bend??? coasts. Therefore sedimentation is dominated by river-and tidal-hydrodynamics near the Aucilla River mouth. Where present, Holocene sediments are thin and unconformably overlie Oligocene-aged Suwannee Limestone. The oldest unlithified sediments include reworked carbonate rubble with clay and wood fragments (seven thousand years old or less, based on wood radio-carbon dating). Although this basal sequence is observed in most areas, the sediments that overlie it vary. Sediment sequences from the outer littoral to submarine environments include organic-rich sands, oyster biotherm remains, and cleaner sands with organic-filled burrows. Inner littoral (salt-marsh) sequences generally consist of sandy, fining-upwards sequences in which dry weights of fine-grained clastics and organic components increase up-sequence at similar rates. Offshore sediments preserve greatly attenuated fluvial and salt-marsh facies, if these facies are preserved at all. With sea-level rise, erosion can result from insufficient sediment supply and down-cutting by tidal currents (Dolotov, 1992; and Dalrymple et al., 1992). Dolotov (1992) attributes displacement of original coastal stratigraphy to insufficient sediments for beach profile maintenance, while Dalrymple et al. (1992) attribute erosional truncation (ravinement) or complete removal of portions of typical estuarine sequences to headward migration of tidal channels.

  5. Holocene evolution of coastal chalk cliffs in Normandy (NW France) as evidenced by onshore-offshore high resolution geomorphology

    NASA Astrophysics Data System (ADS)

    Duguet, Timothée; Duperret, Anne; Costa, Stéphane; Regard, Vincent; Maillet, Grégoire

    2017-04-01

    Key words: erosion, rocky coast, cliffs, shore platform, watersheds, cosmogenic dating The chalk cliffs coastline extends to 120 km long in Normandy. It suffers from high erosion rates with a mean of about 0.15 m/y. The shore platforms extending from the cliff base to the sea, keep structural marks of the cliff erosion during long periods, i.e. the Holocene. Therefore it is essential to take an active interest in their morphology and their evolution to better understand cliff erosion timing. A land-sea Digital Elevation Model (DEM) has been produced for Mesnil-Val and Criel-sur-Mer sites (Seine Maritime), with the merge of topographic data (RGE alti, IGN) and shallow bathymetric data from three oceanographic Cruises, CROCOLIT-1 and 3 (Duperret, 2013) and SPLASHALIOT-2 (Maillet, 2014). Valleys that have more or less incised Turonian-Coniacian chalk cliffs occupy the landward part of study sites. The N130E V-shaped incised Mesnil-Val dry valley is elevated at 29 m high above the shore platform level, whereas the N175E Criel-sur-Mer flat valley, extending on 700 m wide and occupied by the Yères river, is directly connected to the shore platform. Offshore, the shore platform morphology varies from Criel-sur-Mer (North) to Mesnil-Val (South). Northern part of the study site is characterized by 1 km wide shore platform made of an overlay of flat steps controlled by normal faults. Southern part highlights a shore platform with a seaward edge located at about 500 m from the cliff face and strictly parallel oriented to the present-day coastline over a minimum distance of 5 km, without fracture control. The shore platform seaward edge is more or less steep and is always localized below the limit of the lowest tide level. Its origin could be related to the in-depth waves influence or to a past sea level stagnation. We aim to identify the origin of this seaward edge, using cosmogenic 10Be dating in order to develop a chalky shore platform evolution model. It is necessary to

  6. The Holocene evolution of the beach and inland aeolian sand of the north-central Mediterranean coast of Israel

    NASA Astrophysics Data System (ADS)

    Roskin, Joel; Sivan, Dorit; Bookman, Revital; Shteinberg, Gilad

    2015-04-01

    Israel's coastal geomorphology, situated within a Mediterranean climate zone, is characterized by parallel Pleistocene aeolianite ridges, coastal cliffs of aeolianite, and sandy beaches. Lobe-like fields of predominantly stable transverse and parabolic quartz sand dunes protrude 2-7 km inland from the current Mediterranean Sea coastline. However, their migration and accumulation history is still not well-defined. This study focuses on the Holocene appearance, chronology and drivers of beach sand deposition and inland aeolian sand transport along the Caesarea-Hadera dunefield in the north-central coastal plain of Israel. In order to achieve these goals, a detailed field survey and sampling campaign was carried out along a west-east and southwest-northeast transect, loyal to the advancement orientations of the currently stable dunes and directions of dominant sand transporting winds. Beach sand, a foredune, a linear dune, and interdunes of parabolic and transverse dunes were sampled down to their aeolianite or red loam (locally named hamra) palaeosol substrate by drilling and analyzing exposed sections. The sampled sediments were sedimentologically analyzed and twenty-five were dated by optically stimulated luminescence (OSL). The results indicate that beach sand started to accumulate rapidly around 6 ka probably in response to global sea level stabilization. Until around 4 ka, thin sand sheets encroached 2-3 km inland. Sand ages in the range of 1.2-1.1 ka (8th-9th century CE -- Early Moslem period) were found throughout the study area, suggesting a major mobilization of sand, followed by stabilization around 0.6 ka and pedogenesis. By 1.2 ka, the sands had reached their current extent of 5-7 km inland, suggesting transport in a southwest-northeast orientation similar to the advancement orientation of the current transverse and parabolic dunes. The particle-size distributions of the fine to medium-sized aeolian sand showed minor variation linked to inland transport

  7. late Pleistocene and Holocene pollen record from Laguna de las Trancas, northern coastal Santa Cruz County, California

    USGS Publications Warehouse

    Adam, David P.; Byrne, Roger; Luther, Edgar

    1981-01-01

    A 2.1-m core from Laguna de las Trancas, a marsh atop a landslide in northern Santa Cruz County, California, has yielded a pollen record for the period between about 30,000 B. P. and roughly 5000 B. P. Three pollen zones are recognized. The earliest is characterized by high frequencies of pine pollen and is correlated with a mid-Wisconsinan interstade of the mid-continent. The middle zone contains high frequencies of both pine and fir (Abies, probably A. grandis) pollen and is correlated with the last full glacial interval (upper Wisconsinan). The upper zone is dominated by redwood (Sequoia) pollen and represents latest Pleistocene to middle Holocene. The past few thousand years are not represented in the core. The pollen evidence indicates that during the full glacial period the mean annual temperature at the site was about 2°C to 3°C lower than it is today. We attribute this small difference to the stabilizing effect of marine upwelling on the temperature regime in the immediate vicinity of the coast. Precipitation may have been about 20 percent higher as a result of longer winter wet seasons.

  8. Marine water from mid-Holocene sea level highstand trapped in a coastal aquifer: Evidence from groundwater isotopes, and environmental significance.

    PubMed

    Lee, Stephen; Currell, Matthew; Cendón, Dioni I

    2016-02-15

    A multi-layered coastal aquifer in southeast Australia was assessed using environmental isotopes, to identify the origins of salinity and its links to palaeo-environmental setting. Spatial distribution of groundwater salinity (electrical conductivity values ranging from 0.395 to 56.1 mS/cm) was examined along the coastline along with geological, isotopic and chemical data. This allowed assessment of different salinity sources and emplacement mechanisms. Molar chloride/bromide ratios range from 619 to 1070 (621 to 705 in samples with EC >15 mS/cm), indicating salts are predominantly marine. Two distinct vertical salinity profiles were observed, one with increasing salinity with depth and another with saline shallow water overlying fresh groundwater. The saline shallow groundwater (EC=45.4 to 55.7 mS/cm) has somewhat marine-like stable isotope ratios (δ(18)O=-2.4 to -1.9 ‰) and radiocarbon activities indicative of middle Holocene emplacement (47.4 to 60.4pMC). This overlies fresher groundwater with late Pleistocene radiocarbon ages and meteoric stable isotopes (δ(18)O=-5.5 to -4.6‰). The configuration suggests surface inundation of the upper sediments by marine water during the mid-Holocene (c. 2-8 kyr BP), when sea level was 1-2m above today's level. Profiles of chloride, stable isotopes, and radiocarbon indicate mixing between this pre-modern marine water and fresh meteoric groundwater to varying degrees around the coastline. Mixing calculations using chloride and stable isotopes show that in addition to fresh-marine water mixing, some salinity is derived from transpiration by halophytic vegetation (e.g. mangroves). The δ(13)C ratios in saline water (-17.6 to -18.4‰) also have vegetation/organic matter signatures, consistent with emplacement by surface inundation and extensive interaction between vegetation and recharging groundwater. Saline shallow groundwater is preserved only in areas where low permeability sediments have slowed subsequent downwards

  9. Changes in mid-late Holocene hurricane activity influence coastal dynamics in northeastern Gulf of Mexico - A case study in the Choctawhatchee Bay, Destin FL

    NASA Astrophysics Data System (ADS)

    Ranasinghage, P. N.; Donnelly, J. P.; Evans, R. L.; Ashton, A. D.; Condon, K.; Sullivan, R.; Beltzer, A.; Coastal Systems Group

    2011-12-01

    Hurricanes greatly influence coastal changes in the northern Gulf of Mexico. Sedimentological, geochemical, and productivity indicators show that Choctawhatchee Bay, Destin, FL underwent a series of hydrological changes during the mid-late Holocene period. Sedimentological evidence suggests that these changes were, at least in part, driven by variations in the frequency of intense hurricane landfalls in the area. Based on CHIRP seismic reflectance images, a total of 12 sediment cores, ranging in length from 2-5 m, were extracted from Choctawhatchee Bay. Stratigraphy of these cores was studied using X radiograph and elemental composition was measured at 1mm resolution using an XRF core scanner. Grain size and color reflectance were measured at 0.5-1 cm resolution. Principal component analysis (PCA) was performed on the first derivatives of the combined visible - nIR color reflectance data base to derive compositional data. Environmental proxies (Ca/Ti, Sr/Ti and grain size) indicate that Choctawhatchee Bay was a high energy environment with marine influence between ~6000 yrs BP and ~ 3200 yrs BP and also between ~ 2500 - ~1000 yrs BP. Decreases in gain size, Ca/Ti, and Sr/Ti ratios and an increase in blue-green and eukaryotic algae, as shown by the PCA, indicate gradual isolation and greater freshwater influence in the bay between ~3200 - ~2500 yrs BP. Since sea level has been relatively stable during the mid-late Holocene in the Gulf of Mexico, these changes are most likely related to changes in barrier morphology across the mouth of the bay. During periods of higher hurricane activity, frequent barrier breaching opens the bay, whereas barrier growth during quiescent periods isolates the bay from direct marine influence. The high energy environment between ~2500 - ~ 1000 yrs BP begins with a coarse storm sand layer, This period is also marked by an unconformity, formed by the erosion of a possible strong storm event occurred ~1000 yrs BP . The presence of a number

  10. The impact of Holocene soil-geomorphic riparian development on the role of salmon- derived nutrients in the coastal temperate rainforest of southeast Alaska

    NASA Astrophysics Data System (ADS)

    D'Amore, D. V.; Bonzey, N.; Berkowitz, J.; Ruegg, J.; Bridgham, S.

    2008-12-01

    Salmon and riparian systems are linked in an ecological cycle that is important to both salmon life histories and riparian ecological functions in the coastal temperate rainforest (CTR) of southeast Alaska. Glacial rebound after the last glacial maximum during the Pleistocene expanded riparian zones by uplifting former estuaries in the CTR. The development of these lower river systems enhanced the movement of salmon into stream channels adjacent to terrestrial vegetation and increased the supply of salmon derived nutrients (SDN) to terrestrial ecosystems during the late Holocene. The flow of SDN to and from river systems has been the focus of recent research due to the potential for enhanced aquatic and terrestrial ecosystem productivity. However, there is very little known about the geomorphic development of the terrestrial and aquatic system that supports this important ecological coupling. Mass-spawning species of salmon are most often found in alluvial-fan and floodplain-channel process groups associated with specific soil geomorphic associations in southeast Alaska. We have developed an integrated model of geological controls over stream channel formation combined with soil geomorphology to provide a template for integrating studies of nutrient cycles associated with SDN in CTR streams. River systems and fish populations started to stabilize in their present configuration approximately 6ky ago, which established the primary template for soil and vegetation development in riparian zones along salmon spawning channels. Subsequent sediment delivery from the watershed formed at least two terraces on top of the estuarine base-level. A lower, younger floodplain terrace and an older terrace were identified and described and provide a range of characteristics associated with soil development in riparian zones of these distal portions of large watersheds in the CTR. Many SDN studies have not been able to distinguish the impact of SDN on terrestrial nutrient cycles due

  11. Coastal lake sediments from the southern Cape, South Africa - Implications for sea level and climate variations during the Holocene

    NASA Astrophysics Data System (ADS)

    Wündsch, M.; Haberzettl, T.; Kirsten, K. L.; Meschner, S.; Frenzel, P.; Baade, J.; Daut, G.; Mäusbacher, R.; Kasper, T.; Quick, L. J.; Meadows, M. E.; Zabel, M.

    2015-12-01

    Within the RAIN project (Regional Archives for Integrated iNvestigations) interdisciplinary investigations on climate evolution and environmental change in southern Africa during the Late Quaternary are being conducted. For this purpose, spatial and temporal variations of the three major rainfall zones covering South Africa (winter-, summer- and year-round rainfall zone) are studied using both marine and terrestrial archives. Here we present results inferred from sediment records from lakes Groenvlei and Eilandvlei located on the southern Cape coast within the year-round rainfall zone. From Eilandvlei, a brackish lake that is connected to the Indian Ocean via an estuary, a 30.5 m sediment core was recovered. Reservoir-corrected radiocarbon ages reveal a continuous sedimentation and a maximum age of about 8,900 cal BP. This ultra-high-resolution record of environmental change during the Holocene represents a unique discovery for entire southern Africa. Geochemical data reveal different phases of marine and terrestrial sediment deposition throughout the covered time span. Hence, this record reflects changes in sea level, but also variations in terrestrial sediment transport and thus changing climatic conditions. The sediment core from Groenvlei, which today is isolated from the Indian Ocean, covers the past 4,200 cal BP. Sediments from this lake are predominantly composed of autochthonous carbonates. Mineralogical investigations reveal alternating deposition of calcite and aragonite/dolomite, pointing to variable Mg/Ca ratios and thus variations in lake water salinity. These changes can be linked to sea level variations as well as to changes in the precipitation/evaporation balance, and hence climate. Based on these results, the Groenvlei record reveals a decreasing marine influence and a trend from generally drier to wetter conditions within the last 4,200 yrs. Moreover, several layers of enhanced allochtonous input were detected in this record, which can be

  12. Sediment facies and Holocene deposition rate of near-coastal fluvial systems: An example from the Nobi Plain, Japan

    NASA Astrophysics Data System (ADS)

    Hori, Kazuaki; Usami, Shogo; Ueda, Hiroki

    2011-05-01

    Floodplains are a major component of present near-coastal fluvial systems that have evolved in response to postglacial changes in climate and sea level. Knowledge of sedimentary facies and deposition rates on a centennial to millennial time scale is required for considering floodplain evolution. Two cores, AP1 and AP2, were acquired from an abandoned channel of the Ibi River and its natural levee on the Nobi Plain, central Japan. Sediment facies analysis, electrical conductivity, and radiocarbon dating of borehole samples showed that in both cores organic-rich dark gray floodbasin mud overlies deltaic deposits dating to after approximately 3200 years calibrated radiocarbon age (cal BP) in relation to delta progradation. The accumulation of floodbasin mud continued at the both sites until about 400 cal BP. Around 400 cal BP, the mud was eroded by the overlying channel sand and gravel at AP1 and was covered by fine-grained natural levee deposits at AP2 with an abrupt contact. This timing is concordant with the historical record of avulsion of the Ibi River during the Keicho Era (AD 1596-1615). Averaged aggradation rates at the AP1 and AP2 sites were approximately 2.2 and 3.2 mm/yr, respectively. Faulting-related subsidence along the western edge of the plain has influenced these rates by creating accommodation. Averaged deposition rates differed greatly between the floodbasin and the levee, suggesting that rapid aggradation of the natural levee also occurred on a centennial to millennial scale. These empirical data may be useful for testing models of the architecture and evolution of near-coastal fluvial systems.

  13. Upper-plate deformation following megathrust earthquakes: Holocene slip along the El Yolki Fault in central Chile inferred from deformed coastal sediments

    NASA Astrophysics Data System (ADS)

    Hillemann, Christian; Melnick, Daniel; Jara-Muñoz, Julius; Strecker, Manfred R.

    2015-04-01

    Great subduction earthquakes are commonly accompanied by motion of upper-plate faults, either during the megathrust event or in the weeks to months that follow. One of the best documented examples of such coupled behavior is probably the 2010 Pichilemu earthquake sequence of central Chile with MW 6.9 and 7.0 events sourced by a shallow normal fault 11 days after the MW 8.8 Maule earthquake that originated offshore Chile. Similarly, normal faults ruptured the surface after the 2011 Tohoku earthquake in Japan, and additional examples may exist in other subduction environments. Static stress transfer on optimally oriented faults located at the periphery of high-slip sectors has been suggested as the trigger mechanism for these earthquakes following major plate-boundary earthquakes. Numerous normal and reverse faults have been mapped along the ~500-km-long rupture zone of the 2010 Maule earthquake, but post-seismic upper-plate seismicity was concentrated only at the Pichilemu normal fault, which is immediately to the north of the area where slip reached its maximum of 17 m. To gain insight into the relation between megathrust ruptures and associated motion of upper-plate faults, we studied the El Yolki Fault (ELYF), a normal fault located near the region of lowest megathrust slip in 2010. We attempted to obtain the slip rate of the ELYF integrating field mapping of Holocene coastal landforms and combined airborne and terrestrial LiDAR data. In addition, paleoseismological trenches were dug along the uplifted footwall block where marine lagoonal sediments were back-tilted and uplifted by inferred slip along the ELYF. The trenches reveal basal metamorphic rocks and overlying fluvial sediments into which a stepped sequence of four distinct, decimeter-scale scarps had been sculpted at successively higher positions above bedrock. These erosional scarps are covered by a sequence of onlapping silty and clayey organic-rich intertidal sediments. In turn, these units are

  14. A Tale of Two Limpets (Patella vulgata and Patella stellaeformis): Evaluating a New Proxy for Late Holocene Climate Change in Coastal Areas

    NASA Astrophysics Data System (ADS)

    Fenger, T. L.; Surge, D. M.; Schoene, B. R.; Carter, J. G.; Milner, N.

    2006-12-01

    Shells of the European limpet, Patella vulgata, from Late Holocene archaeological deposits potentially contain critical information about climate change in coastal areas. Before deciphering climate information preserved in these zooarchaeological records, we studied the controls on oxygen isotope ratios (δ18O) in modern specimens. We tested the hypothesis that P. vulgata precipitates its shell in isotopic equilibrium with ambient water by comparing δ18OSHELL with expected values. Expected δ18OSHELL was constructed using the calcite-water fractionation equation, observed sea surface temperature (SST), and assuming δ18OWATER is +0.10‰ (VSMOW). Comparison between expected and measured δ18OSHELL revealed a +1.51±0.21‰ (VPDB) offset from expected values. Consequently, estimated SST calculated from δ18OSHELL was 6.50±2.45°C lower than observed SST. However, because the offset was relatively uniform, an adjustment can be made to account for this predictable vital effect and past SST can be reliably reconstructed. To further investigate the source of offset in this genus, we analyzed a fully marine tropical species (Patella stellaeformis) to minimize seasonal variation in environmental factors that influence δ18OSHELL. P. stellaeformis was evaluated to determine whether it has a similar offset from equilibrium as P. vulgata. We tested the hypotheses that: (1) δ18OSHELL in tropical species also displays vital effects; and (2) the offset from equilibrium (if any) would be constant and predictable. Our results indicated: (1) aragonite comprises most of P. stellaeformis' shell; and (2) δ18OSHELL is statistically indistinguishable from expected values calculated using the aragonite-water fractionation equation (Kolmogorov-Smirnov test statistic=0.61, D0.05[56, 57]=1.36) in contrast with our observations in P. vulgata. Differences in mineralogy or growth rates at different latitudes may play a role in mechanisms that influence vital effects.

  15. Seismic or hydrodynamic control of rapid late-holocene sea-level rises in Southern coastal Oregon, USA?

    USGS Publications Warehouse

    Nelson, A.R.; Ota, Y.; Umitsu, M.; Kashima, K.; Matsushima, Y.

    1998-01-01

    Intertidal stratigraphy has been instrumental in demonstrating the hazard posed by great earthquakes at the Cascadia subduction zone, but inferring an earthquake history from interbedded sequences of peat and mud is complicated by many factors that influence sedimentation and relative sea-level change on both tectonic and nontectonic coasts. Rapid-to-sudden rises in relative sea level marked by sharp contacts between intertidal peat and overlying mud or sand may reflect coseismic coastal subsidence and tsunami deposition or, alternatively, nonseismic hydrodynamic changes in estuaries. Reconnaissance coring at 16 sites in the marshes fringing a narrow, protected tidal inlet of Coos Bay, supplemented by diatom and 14C analyses at four sites, reveals a stratigraphic record too fragmentary and ambiguous to distinguish seismic from hydrodynamic causes for more than three of the 10 rises in relative sea-level identified. Only three sharp contacts have the wide extent and evidence of substantial (>0.5 m) submergence that distinguish them from similar contacts produced by nonseismic processes. Correlation with stratigraphic sequences at other estuaries shows that the fringing marshes suddenly subsided and were partially buried by tsunami sand during a great plate-boundary earthquake about 300 years ago. Similar contacts were produced by earthquakes about 1500-1800 years ago, and perhaps about 2400-2700 years ago. Other earthquakes with substantially less subsidence may also have occurred, but evidence is too ambiguous to reconstruct a more complete history.

  16. Late Holocene glacial history of the Copper River Delta, coastal south-central Alaska, and controls on valley glacier fluctuations

    NASA Astrophysics Data System (ADS)

    Barclay, David J.; Yager, Elowyn M.; Graves, Jason; Kloczko, Michael; Calkin, Parker E.

    2013-12-01

    Fluctuations of four valley glaciers in coastal south-central Alaska are reconstructed for the past two millennia. Tree-ring crossdates on 216 glacially killed stumps and logs provide the primary age control, and are integrated with glacial stratigraphy, ages of living trees on extant landforms, and historic forefield photographs to constrain former ice margin positions. Sheridan Glacier shows four distinct phases of advance: in the 530s to c.640s in the First Millennium A.D., and the 1240s to 1280s, 1510s to 1700s, and c.1810s to 1860s during the Little Ice Age (LIA). The latter two LIA advances are also recorded on the forefields of nearby Scott, Sherman and Saddlebag glaciers. Comparison of the Sheridan record with other two-millennia long tree-ring constrained valley glacier histories from south-central Alaska and Switzerland shows the same four intervals of advance. These expansions were coeval with decreases in insolation, supporting solar irradiance as the primary pacemaker for centennial-scale fluctuations of mid-latitude valley glaciers prior to the 20th century. Volcanic aerosols, coupled atmospheric-oceanic systems, and local glacier-specific effects may be important to glacier fluctuations as supplemental forcing factors, for causing decadal-scale differences between regions, and as a climatic filter affecting the magnitude of advances.

  17. Response of surface processes to climatic change in the dunefields and Loess Plateau of North China during the late Quaternary

    USGS Publications Warehouse

    Lu, H.; Mason, J.A.; Stevens, T.; Zhou, Y.; Yi, S.; Miao, X.

    2011-01-01

    This paper draws on recent optically stimulated luminescence (OSL) dating to evaluate the long-held assumption that dust accumulation rates in the Loess Plateau and the extent of active aeolian sand in the dunefields to the north have varied together over time, because both are controlled by the strength of the Asian monsoons and also possibly because the dunefields are proximal loess sources. The results show there is little evidence that high rates of loess accumulation coincided with well-dated episodes of extensive dune activity in the Mu Us, Otindag, and Horqin dunefields, at 11-8ka and 1-0ka. Explanations for the apparent lack of coupling include local variation in the trapping of dust and post-depositional preservation of the loess and dune sediments, in response to varying local environmental conditions. In addition, a substantial portion of the loess may be transported directly from source areas where dust emission has somewhat different climatic and geomorphic controls than aeolian sand activity within the dunefields. The results of this study cast doubt on the use of loess accumulation rate as a palaeoclimatic proxy at millennial timescale. The dunefield and loess stratigraphic records are interpreted as primarily recording changes in effective moisture at a local scale, but the timing of late Quaternary dune activity, along with a variety of other evidence, indicates that moisture changes in many of the drylands of northern China may not be in phase with precipitation in core regions of the Asian monsoons. ?? 2011 John Wiley & Sons, Ltd.

  18. Late Holocene climate and land-use impacts on ecology and carbon cycling in Atlantic coastal plain tidal freshwater wetlands

    NASA Astrophysics Data System (ADS)

    Jones, M.; Bernhardt, C. E.

    2013-12-01

    Tidal freshwater wetlands are vulnerable to degradation from changing climate, land-use practices, and sea level. Their position between fully tidal and fully non-tidal ecosystems and sensitivity to minor fluctuations in salinity makes them ideal candidates to record the effects of climate and sea-level variability. These wetlands also act as a substantial carbon (C) sink, and paleoclimate studies provide important evidence not only on the long-term impact of perturbations on their ecological structure and function, but also on their ability to store C. Here we examine the late Holocene impacts of climate, land-use change, and sea level rise on four tidal freshwater wetlands in the Waccamaw River and Turkey Creek, South Carolina. A transect of four sites that range from an almost completely fresh forested swamp at the most upstream site to a higher salinity oligohaline marsh downstream. The two intermediate sites are forested swamps at different stages of degradation. We analyzed pollen assemblages, plant macrofossils, and carbon accumulation rates from sediment cores spanning the last ~1500-2000 years. Overall, higher rates of C accumulation are associated with woody swamp peat than with herbaceous peat, as determined from peat macrofossils and pollen assemblages. All sites show decreased C accumulation rates with the onset of the Medieval Climate Anomaly (MCA), which remained low through the Little Ice Age (LIA) (~1500 to 150 cal yr BP). These changes are accompanied by a switch from woody swamp peat to a graminoid-dominated peat lithology in the two uppermost forested swamp locations, as well as in the oligohaline marsh located farthest south along the transect. The switch from swamp to the modern oligohaline marsh during the MCA suggests that both sea level and land-use change permanently transformed the wetland. Rice cultivation beginning ~300 cal yr BP may be responsible for an apparent hiatus in several of the cores and may explain a Poaceae spike in the

  19. Holocene Depositional History of Shad Pond, a Hypersaline Coastal Lagoon, Eleuthera, Bahamas and Its Influence on Lucayan Occupation

    NASA Astrophysics Data System (ADS)

    Boush, L. E.; Fentress, S.; Conroy, M.; Cook, A.; Miseridina, D.; Buynevich, I. V.; Myrbo, A.; Brown, E. T.; Berman, M.; Gnivecki, P.; Kjellmark, E.; Savarese, M.; Brady, K.

    2013-12-01

    Shad Pond, an enclosed hypersaline lagoon on the southeastern tip of Eleuthera, Bahamas reveals a ~5000-year record of hurricane activity, as well as sea-level and climate change history. Three sediment cores recovered 1.04-2.54 m of sediment over bedrock along a transect perpendicular to shoreline. Sediment composition and grain size, loss on ignition, X-ray fluorescence (XRF) measurements of the cores along with dune transects and ground-penetrating radar (GPR) profiles adjacent to the lake provide a comprehensive dataset to interpret the history of this coastal basin. The sedimentary sequence was composed of alternating lithofacies that included microbial mats, sand, and peat. Laminated mats often alternated with sandy layers in thin to medium-bedded units. Two peat layers were found in the basal part of the shore-distal core (Site 1) between 1.82-2.40 m and 2.53-2.54 m and were separated by a 13-cm-thick gray mud layer. In general, organic matter and carbonate content tracked granulometry and composition in all cores. High-resolution XRF scans of Ca and Sr at Site 1 show elevated levels ~3,700 cal yBP, which correlate with the top of the peat layer, but these elemental concentrations vary at Site 3. XRF measurements of Fe indicate a dust flux that has been recorded regionally throughout the Caribbean. Dune transects and GPR profiles indicate a phased history of the pond, beginning with initial stages as an open lagoon dominated by red mangrove, with black mangrove and buttonwood also present. The lake likely closed at approximately 3,700 cal yBP indicated by the transition between the upper peat and microbial mat layers. This could have been due to increased storm events in a regime of rising sea level. Aeolian aggradation continued to heighten the barrier between the bedrock headlands to its present position. Hurricane overwash deposits punctuated the algal mat accumulation throughout this time period. Present-day hypersaline conditions sustain algal mats

  20. Palaeoclimate interpretations of Late Pleistocene vegetated linear dune mobilization episodes: evidence from the northwestern Negev dunefield, Israel

    NASA Astrophysics Data System (ADS)

    Roskin, J.; Tsoar, H.; Porat, N.; Blumberg, D. G.

    2012-04-01

    The northern Sinai - northwestern (NW) Negev erg stretches east out of the Nile Delta that is believed to be the erg's sand source. The vegetated linear dune (VLD) field of the NW Negev Desert, situated at the downwind eastern end of the erg, constitutes an ideal setting for dating and interpreting its Late Quaternary dune encroachment episodes. This study builds upon the results of Roskin et al. (Age, origin and climatic controls on vegetated linear dunes in the northwestern Negev Desert (Israel), Quaternary Science Reviews 30 (2011), 1649-1674) that presented the stratigraphy of 35 sections and 97 optically stimulated luminescence (OSL) ages from the NW Negev dunefield. Here we analyze Late Pleistocene dune mobilizations and stabilizations and interpret their palaeoclimatic controls in light of regional and global dune ages, sediment records and proxies. While initial dune encroachment into, and stabilization in, the NW Negev took place during the Last Glacial Maximum (LGM) at ~23-18 ka, spatial and statistical analyses of the OSL dataset suggest that since the LGM, Negev dune activity was concentrated in two significant mobilization-stabilization episodes: a main episode at ~16-13.7 ka and a minor one at ~12.4-11.6 ka when the dunes reached their maximum spatial extent and stabilized. These episodes include rapid dune encroachment and accretion events and coincide with the Heinrich 1 and Younger Dryas cold events, respectively. The Late Pleistocene sand-transporting winds were characterized by a westerly direction that resulted in west-east VLD elongation. Dune mobilizations may have occurred in response to wintertime East Mediterranean cyclonic systems that brought storms of rainfall and strong winds. The rapid dune mobilization events and their concurrence with the Heinrich 1 and Younger Dryas cold events suggest a more global control. Despite the rainfall, the elongating VLDs were probably sparsely vegetated because of the high wind power; their stabilization

  1. Definition and origin of the dune-field pattern at White Sands, New Mexico

    NASA Astrophysics Data System (ADS)

    Baitis, Elke; Kocurek, Gary; Smith, Virginia; Mohrig, David; Ewing, Ryan C.; Peyret, A.-P. B.

    2014-12-01

    A LiDAR-derived digital elevation model (DEM) of a representative portion of the White Sands Dune Field, New Mexico, allows for characterization of an unprecedented range of dune-field parameters and serves as a basis for pattern analysis. Dune-field parameters were measured and statistically analyzed for populations of dunes selected at random and occurring along transects. Populations sampled by these two different methods are comparable, but highlight the sensitivity of transect placement in a dune field that has pattern heterogeneity. Based upon coefficients of variation, pattern emerges at White Sands primarily because of a strong fabric of crestline orientation, and secondarily because of the regularity of spacing between dunes of similar shape as defined by sinuosity, height and length. Linear regression of dune parameters shows that dune geometric relationships vary primarily with crestline length, but there is little correlation between other parameters, including dune spacing and height. This result highlights the sensitivity of identifying topographic heterogeneity in a LiDAR-derived DEM, given that mean ratios conform to global averages. Stripping off the dunes in Matlab shows a terraced surface, which is interpreted to represent paleo-shorelines formed during relative still stands in the overall retreat of Lake Otero. Elevated bands of higher, more closely spaced dunes occur just leeward of the paleo-shorelines. A revised model for the White Sands Dune Field consists of the basinward progradation of successive dune-field segments. Each segment is associated with a paleo-shoreline, and consists of an upwind dune ridge, represented by the elevated bands, and a leeward dune field.

  2. Geomorphology context and characterization of dunefields developed by the southern westerlies at drying Colhué Huapi shallow lake, Patagonia Argentina

    NASA Astrophysics Data System (ADS)

    Montes, Alejandro; Rodríguez, Silvana Soledad; Domínguez, Carlos Eduardo

    2017-10-01

    Patagonia is the only continental territory exposed to the southern westerlies. The speed and frequency of these westerly winds generate a landscape strongly influenced by aeolian processes. This research shows a characterization of depositional and erosive aeolian landforms developed in dunefields associated to Lake Colhué Huapi, in the Extra-Andean Patagonia. Dunefields are located at 45°-46°S and moved in west-east direction due to the southern westerlies. We identified two big groups of active dunefields, one migrating through the dry lakebed of Colhué Huapi and the other migrating eastwards from the lakeshore. The dunefields mainly consist of transverse dunes, barchans, sand shadows and sand sheets. Yardangs, desert pavements, exhumed roots and decapitated soils were recognized in interdune areas. Longitudinal sand ridges, parallel to the prevailing wind direction, often remain preserved after the dunefields have passed. This allows to recognize the path of the dunes in the past. Sand ridges are recognized up to 28 km east from the present coast of the lake and evidenced former dunefields development. We describe the geomorphology context, landforms and sediments supply of dunefields related to the lake dynamics subject to clear tendency to desiccation.

  3. The use of Landsat-ETM Data, Digital Elevation Models and GIS Analyses for Quantification of Holocene Thermokarst: An Example From the Lena-Anabar Coastal Region (NE Siberia)

    NASA Astrophysics Data System (ADS)

    Grosse, G.; Schirrmeister, L.

    2004-12-01

    Ice super-saturated permafrost deposits, formed syn-genetically during the Late Pleistocene, are widely distributed in coastal lowland regions of Arctic NE Siberia. The ice content of the silty deposits (up to 160 weight-percent compared to dry mass) makes them very susceptible for large-area thawing and surface subsidence under warmer climate conditions. Hence, extensive thermokarst developed in this region during the Holocene. Generally, thermokarst is a significant factor in periglacial relief generation and landscape evolution. Additionally, the analysis of thermokarst-related transformation processes in periglacial landscapes is very important regarding the expected deep thawing of permafrost and the release of formerly frozen organic carbon in form of green house gases under a global warming scenario. To evaluate the Holocene thermokarst development and estimate possible future developments in the region, it is necessary to calculate and understand its actual extent. For this investigation, Landsat-ETM remote sensing data from the Lena-Anabar coastal lowland is used as an instrument for up-scaling local field data. Classes of different geomorphological units are discriminated with supervised classification algorithms based on various surface parameters like vegetation, relief, and soil moisture. These classes allow the characterization and quantification of periglacial landscape units with a focus on thermokarst features in the investigated area. The spatial distribution of identified thermokarst structures and their relationship to other geomorphological and hydrological features are analysed within a geographical information system using a digital elevation model and geomorphological parameters derived from the DEM. As result, quantitative and qualitative parameters for thermokarst structures in this Laptev Sea coastal region are derived.

  4. Dinocysts and other palynomorphs from the Holocene record of the Adélie coastal margin, Antarctica (IODP Site U1357)

    NASA Astrophysics Data System (ADS)

    Hartman, Julian; Sangiorgi, Francesca; Bijl, Peter; Brinkhuis, Henk

    2016-04-01

    During International Ocean Drilling Program Expedition 318, about 170 meters of Holocene core have been retrieved from Site U1357, near the Adélie Coast, East-Antarctica. This core provides a high resolution marine record of Holocene climate variability close to the Antarctic margin. Palynomorphs in this core are extremely well-preserved due to the high sedimentation rates of diatom ooze. One of these exceptionally well-preserved finds is the first account of cysts of a sea-ice dwelling suessoid dinoflagellate (Polarella glacialis). Furthermore, a new species of dinoflagellate cyst, large amounts of tintinnid loricae, copepod remains, and various kinds of unknown/undescribed acritarch species have been found. Although the composition of the palynomorphs assemblage is highly variable throughout the record, this record potentially gives insight into ecological and/or environmental changes in a polynya-controlled environment since the last deglaciation. For example, the dinocyst assemblage seems to indicate that the sea-ice season was shorter in the early Holocene.

  5. Water management during climate change using aquifer storage and recovery of stormwater in a dunefield in western Saudi Arabia

    NASA Astrophysics Data System (ADS)

    Lopez, O.; Stenchikov, G.; Missimer, T. M.

    2014-07-01

    An average of less than 50 mm yr-1 of rainfall occurs in the hyperarid region of central Western Saudi Arabia. Climate change is projected to create greater variation in rainfall accumulation with more intense rainfall and flood events and longer duration droughts. To manage climate change and variability in ephemeral stream basins, dams are being constructed across wadi channels to capture stormwater, but a large percentage of this stored water is lost to evaporation. A dam/reservoir system located in Wadi Al Murwani in Western Saudi Arabia was recently constructed and is expected to contain a maximum stored water volume of 150 million m3. A hydrologic assessment of a dunefield lying 45 km downstream was conducted to evaluate its potential use for aquifer storage and recovery of the reservoir water. A 110 m elevation difference between the base of the dam and the upper level of the dunefield occurs, allowing conveyance of the water from the reservoir to the dunefield storage site by gravity feed without pumping, making the recharge system extremely energy efficient. Aquifer storage and recovery coupled with dams would allow water management during extreme droughts and climate change and has widespread potential application in arid regions.

  6. Development of spatially diverse and complex dune-field patterns: Gran Desierto Dune Field, Sonora, Mexico

    USGS Publications Warehouse

    Beveridge, C.; Kocurek, G.; Ewing, R.C.; Lancaster, N.; Morthekai, P.; Singhvi, A.K.; Mahan, S.A.

    2006-01-01

    The pattern of dunes within the Gran Desierto of Sonora, Mexico, is both spatially diverse and complex. Identification of the pattern components from remote-sensing images, combined with statistical analysis of their measured parameters demonstrate that the composite pattern consists of separate populations of simple dune patterns. Age-bracketing by optically stimulated luminescence (OSL) indicates that the simple patterns represent relatively short-lived aeolian constructional events since ???25 ka. The simple dune patterns consist of: (i) late Pleistocene relict linear dunes; (ii) degraded crescentic dunes formed at ???12 ka; (iii) early Holocene western crescentic dunes; (iv) eastern crescentic dunes emplaced at ???7 ka; and (v) star dunes formed during the last 3 ka. Recognition of the simple patterns and their ages allows for the geomorphic backstripping of the composite pattern. Palaeowind reconstructions, based upon the rule of gross bedform-normal transport, are largely in agreement with regional proxy data. The sediment state over time for the Gran Desierto is one in which the sediment supply for aeolian constructional events is derived from previously stored sediment (Ancestral Colorado River sediment), and contemporaneous influx from the lower Colorado River valley and coastal influx from the Bahia del Adair inlet. Aeolian constructional events are triggered by climatic shifts to greater aridity, changes in the wind regime, and the development of a sediment supply. The rate of geomorphic change within the Gran Desierto is significantly greater than the rate of subsidence and burial of the accumulation surface upon which it rests. ?? 2006 The Authors. Journal compilation 2006 International Association of Sedimentologists.

  7. Climatic and palaeoecological changes during the mid- to Late Holocene transition in eastern China: high-resolution pollen and non-pollen palynomorph analysis at Pingwang, Yangtze coastal lowlands

    NASA Astrophysics Data System (ADS)

    Innes, James B.; Zong, Yongqiang; Wang, Zhanghua; Chen, Zhongyuan

    2014-09-01

    The transition to the Late Holocene/Neoglacial occurred as a worldwide process of climatic deterioration from the optimum thermal conditions of the mid-Holocene, culminating in an abrupt decline around 4200 cal yr ago, in a period of severe climatic deterioration that lasted for two or three centuries. This sudden climatic event has been recorded in many proxy data archives from around the world, and its effects were manifest in different ways depending on the reaction of regional weather systems and conditions, but often as greatly increased aridity and/or cold temperatures. It has been regarded as causing or contributing to the sudden collapse of several well-established human societies at that time, including advanced agricultural Late Neolithic cultures in eastern China. We have used high-resolution pollen and non-pollen palynomorph analysis to examine the nature of this climatic transition through its impacts on the vegetation and hydrology at Pingwang, a site in the Yangtze coastal lowlands which has no evidence of complicating environmental influences such as sea-level rise or significant human land-use activity, factors previously suggested as alternative reasons for changes in forest composition. Our results show two phases of forest alteration, one gradual from about 5500 cal BP and one sudden at about 4200 cal BP., in which the frequencies of subtropical forest elements fall and are replaced by those of conifers and cold-tolerant trees. Total arboreal pollen frequencies do not decline and the proportion of temperate forest trees, tolerant of a wide range of temperatures, remains unchanged throughout, both ruling out human land clearance as a cause of the change in forest composition. As these dates accord very well with the known timings of climate deterioration established from other proxy archives in the region, we conclude that climate was the main driver of vegetation change in eastern China at the mid- to Late Holocene transition. Our hydrological

  8. Coastal landscape evolution on the western margin of the Bahía Blanca Estuary (Argentina) mirrors a non-uniform sea-level fall after the mid-Holocene highstand

    NASA Astrophysics Data System (ADS)

    Pratolongo, Paula; Piovan, María Julia; Cuadrado, Diana G.; Gómez, Eduardo A.

    2017-08-01

    Sedimentary descriptions and radiocarbon ages from two cores obtained from coastal plains along the western margin of the Bahía Blanca Estuary (Argentina) were integrated with previous information on landscape patterns and plant associations to infer landscape evolution during the mid-to-late Holocene. The study area comprises at least two marine terraces of different elevations. The old marine plain (OMP), at an average elevation of 5 m above mean tidal level (MTL), is a nearly continuous flat surface. The Recent marine plain (RMP), 2 to 3 m above MTL, is a mosaic of topographic highs and elongated depressions that may correspond to former tidal channels. Mollusks at the base of the OMP core (site elevation 5.09 m above MTL), with ages between 5,660 ± 30 and 5,470 ± 30 years BP, indicate a subtidal setting near the inland limits of the marine ingression. The sandy bottom of the core is interpreted as the last stage of the transgressive phase, followed by a tight sequence of dark laminated muds topped by a thick layer of massive gray muds. The RMP core (site elevation 1.80 m above MTL) has a similar sedimentary sequence, but unconformities appear at lower elevations and the massive mud deposits are less developed. The thickness of the grayish mud layer is a major difference between the OMP and RMP cores, but deeper layers have similar ages, suggesting a common origin at the end of the transgressive phase. The overlying massive muds would correspond to rapid sedimentation during a high sea-level stillstand or slow regression. It is proposed that, after a rapid sea-level drop to about 3 m above MTL, a flat and continuous surface corresponding to the OMP emerged, and more recent coastal dynamics shaped the dissected landscape of the RMP. For the Bahía Blanca Estuary, smooth regressive trends have been proposed after the mid-Holocene highstand, but also stepped curves. A stillstand or slowly dropping sea level was described around 3,850 ± 100 years BP, as well as

  9. Coastal landscape evolution on the western margin of the Bahía Blanca Estuary (Argentina) mirrors a non-uniform sea-level fall after the mid-Holocene highstand

    NASA Astrophysics Data System (ADS)

    Pratolongo, Paula; Piovan, María Julia; Cuadrado, Diana G.; Gómez, Eduardo A.

    2016-11-01

    Sedimentary descriptions and radiocarbon ages from two cores obtained from coastal plains along the western margin of the Bahía Blanca Estuary (Argentina) were integrated with previous information on landscape patterns and plant associations to infer landscape evolution during the mid-to-late Holocene. The study area comprises at least two marine terraces of different elevations. The old marine plain (OMP), at an average elevation of 5 m above mean tidal level (MTL), is a nearly continuous flat surface. The Recent marine plain (RMP), 2 to 3 m above MTL, is a mosaic of topographic highs and elongated depressions that may correspond to former tidal channels. Mollusks at the base of the OMP core (site elevation 5.09 m above MTL), with ages between 5,660 ± 30 and 5,470 ± 30 years BP, indicate a subtidal setting near the inland limits of the marine ingression. The sandy bottom of the core is interpreted as the last stage of the transgressive phase, followed by a tight sequence of dark laminated muds topped by a thick layer of massive gray muds. The RMP core (site elevation 1.80 m above MTL) has a similar sedimentary sequence, but unconformities appear at lower elevations and the massive mud deposits are less developed. The thickness of the grayish mud layer is a major difference between the OMP and RMP cores, but deeper layers have similar ages, suggesting a common origin at the end of the transgressive phase. The overlying massive muds would correspond to rapid sedimentation during a high sea-level stillstand or slow regression. It is proposed that, after a rapid sea-level drop to about 3 m above MTL, a flat and continuous surface corresponding to the OMP emerged, and more recent coastal dynamics shaped the dissected landscape of the RMP. For the Bahía Blanca Estuary, smooth regressive trends have been proposed after the mid-Holocene highstand, but also stepped curves. A stillstand or slowly dropping sea level was described around 3,850 ± 100 years BP, as well as

  10. A mid-Holocene record of sediment dynamics and high resolution accretion rates in a coastal salt marsh from Northern California

    NASA Astrophysics Data System (ADS)

    Brown, L. N.; Holmquist, J. R.; MacDonald, G. M.

    2013-12-01

    Sediment accretion rates in coastal salt marshes are the critical determining factor in terms of ecosystem stability in the face of accelerated sea level rise (SLR), projected to rise by up to 1.4 m by 2100 in Southern California (National Research Council, 2012). However, high resolution studies of accretion rates in coastal salt marshes over the past several millennia have not yet been conducted for most of the US west coast. We collected multiple sediment records from small salt marshes surrounding Humboldt Bay, California. Due to this unique tectonic setting, many suspect cores from these marshes have evidence of coastal subsidence due to earthquake activity or large tsunami deposits (Jacoby et al., 1995). These records therefore are one of the best proxy measures for how salt marshes in California may respond to accelerated SLR. We analyzed all cores for magnetic susceptibility, % organic matter, and select cores for particle size. High resolution, millennial and centennial scale, radiocarbon dating for these sediment records reveals a detailed history of marsh accretion rates.

  11. Holocene climate change in Arctic Canada and Greenland

    NASA Astrophysics Data System (ADS)

    Briner, Jason P.; McKay, Nicholas P.; Axford, Yarrow; Bennike, Ole; Bradley, Raymond S.; de Vernal, Anne; Fisher, David; Francus, Pierre; Fréchette, Bianca; Gajewski, Konrad; Jennings, Anne; Kaufman, Darrell S.; Miller, Gifford; Rouston, Cody; Wagner, Bernd

    2016-09-01

    This synthesis paper summarizes published proxy climate evidence showing the spatial and temporal pattern of climate change through the Holocene in Arctic Canada and Greenland. Our synthesis includes 47 records from a recently published database of highly resolved Holocene paleoclimate time series from the Arctic (Sundqvist et al., 2014). We analyze the temperature histories represented by the database and compare them with paleoclimate and environmental information from 54 additional published records, mostly from datasets that did not fit the selection criteria for the Arctic Holocene database. Combined, we review evidence from a variety of proxy archives including glaciers (ice cores and glacial geomorphology), lake sediments, peat sequences, and coastal and deep-marine sediments. The temperature-sensitive records indicate more consistent and earlier Holocene warmth in the north and east, and a more diffuse and later Holocene thermal maximum in the south and west. Principal components analysis reveals two dominant Holocene trends, one with early Holocene warmth followed by cooling in the middle Holocene, the other with a broader period of warmth in the middle Holocene followed by cooling in the late Holocene. The temperature decrease from the warmest to the coolest portions of the Holocene is 3.0 ± 1.0 °C on average (n = 11 sites). The Greenland Ice Sheet retracted to its minimum extent between 5 and 3 ka, consistent with many sites from around Greenland depicting a switch from warm to cool conditions around that time. The spatial pattern of temperature change through the Holocene was likely driven by the decrease in northern latitude summer insolation through the Holocene, the varied influence of waning ice sheets in the early Holocene, and the variable influx of Atlantic Water into the study region.

  12. AMS-dated mollusks in beach ridges and berms document Holocene sea-level and coastal changes in northeastern Kuwait Bay

    NASA Astrophysics Data System (ADS)

    Reinink-Smith, Linda M.

    2015-09-01

    In northeastern Kuwait, ancient beach ridges and associated berms are separated from the present shoreline by a 4-6 km-wide sabkha. A diverse mollusk fauna in the beach ridges attests to a former open marine environment. A total of 21 AMS dates were obtained in this study. Thirteen mollusk samples from beach ridges yielded AMS dates ranging from ~ 6990 cal yr BP in the southeast to ~ 3370 cal yr BP in the northwest, suggesting a southeast to northwest age progression during the Holocene transgression. In contrast, four samples from berms throughout the study area yielded AMS dates of 5195-3350 cal yr BP showing no age progression; these berms consist largely of Conomurex persicus gastropods that aggregated by storms during a highstand at ~ 5000-3500 cal yr BP. The berms are presently at ~ + 6 m above sea level, 2-3 m above the beach ridges. Human settlements were common on the ridge crests before and after the highstand. Regression to present-day sea level commenced after the highstand, which is when the sabkha began forming. A landward, marine-built terrace, which yielded AMS dates > 43,500 14C yr BP, probably formed during Marine Oxygen Isotope Stage 5e and hence is not genetically related to the beach ridges.

  13. Mg/Ca, Sr/Ca, and stable isotopes in modern and Holocene Protothaca staminea shells from a northern California coastal upwelling region

    NASA Astrophysics Data System (ADS)

    Takesue, Renee K.; van Geen, Alexander

    2004-10-01

    This study explores the potential of intertidal Protothaca staminea shells as high-resolution geochemical archives of environmental change in a coastal upwelling region. Mg/Ca and Sr/Ca ratios were analyzed by excimer laser ablation-inductively coupled plasma mass spectrometry (LA-ICP-MS) at sub-weekly temporal resolution in shells growing ˜1 mm per month. Growth patterns of a modern P. staminea shell from Humboldt Bay, California, collected in December 1999 made it possible to infer a lifespan from 1993 to 1998. Growth hiatuses in the shell may have excluded records of extreme events. Mg/Ca ratios appeared to be partly controlled by water temperature; the correlation coefficient between temperature and Mg/Ca was r = 0.71 in one of four growth increments. Significant year-to-year differences in the sensitivity of Mg/Ca to temperature in P. staminea could not be explained, however. Sr/Ca ratios appeared to be more closely related to shell growth rate. Oxygen isotopes, measured at 2-week temporal resolution in the same shell, did not show a clear relation to local temperature in summer, possibly because temperatures were higher and less variable at the King Salmon mudflat, where the shell was collected, than in the main channel of Humboldt Bay, where water properties were monitored. Negative shell δ 13C values (<-0.5‰) marked spring and summer coastal upwelling events. The Mg contents of P. staminea midden shells dated to ˜3 ka and ˜9 ka were significantly lower than in the modern shell. This may have resulted from degradation of a Mg-rich shell organic matrix and precluded quantitative interpretation of the older high-resolution records. Elevated δ 13C values in the ˜3 ka shell suggested that the individual grew in highly productive or stratified environment, such as a shallow coastal embayment or lagoon.

  14. Mg/Ca, Sr/Ca, and stable isotopes in modern and Holocene Protothaca staminea shells from a northern California coastal upwelling region

    USGS Publications Warehouse

    Takesue, R.K.; VanGeen, A.

    2004-01-01

    This study explores the potential of intertidal Protothaca staminea shells as high-resolution geochemical archives of environmental change in a coastal upwelling region. Mg/Ca and Sr/Ca ratios were analyzed by excimer laser ablation-inductively coupled plasma mass spectrometry (LA-ICP-MS) at sub-weekly temporal resolution in shells growing ???1 mm per month. Growth patterns of a modern P. staminea shell from Humboldt Bay, California, collected in December 1999 made it possible to infer a lifespan from 1993 to 1998. Growth hiatuses in the shell may have excluded records of extreme events. Mg/Ca ratios appeared to be partly controlled by water temperature; the correlation coefficient between temperature and Mg/Ca was r = 0.71 in one of four growth increments. Significant year-to-year differences in the sensitivity of Mg/Ca to temperature in P. staminea could not be explained, however. Sr/Ca ratios appeared to be more closely related to shell growth rate. Oxygen isotopes, measured at 2-week temporal resolution in the same shell, did not show a clear relation to local temperature in summer, possibly because temperatures were higher and less variable at the King Salmon mudflat, where the shell was collected, than in the main channel of Humboldt Bay, where water properties were monitored. Negative shell ??13C values (<-0.5???) marked spring and summer coastal upwelling events. The Mg contents of P. staminea midden shells dated to ???3 ka and ???9 ka were significantly lower than in the modern shell. This may have resulted from degradation of a Mg-rich shell organic matrix and precluded quantitative interpretation of the older high-resolution records. Elevated ??13C values in the ???3 ka shell suggested that the individual grew in highly productive or stratified environment, such as a shallow coastal embayment or lagoon. Copyright ?? 2004 Elsevier Ltd.

  15. Mid-Holocene Hemlock Decline in Eastern North America Linked with Phytophagous Insect Activity

    NASA Astrophysics Data System (ADS)

    Bhiry, Najat; Filion, Louise

    1996-05-01

    Macrofossil evidence indicates that the mid-Holocene hemlock [ Tsuga canadensisL. (Carr.)] decline that occurred over a wide area in eastern North America was associated with phytophagous insect activity. In situhemlock macrofossils and insect remains found in a paludified dunefield at the northern limit of hemlock testify that two defoliation events occurred at 4910 ± 90 and 4200 ± 100 yr B.P., respectively. The sharp coincidence of remains from hemlock needles with chewing damage typical of hemlock looper feeding, head capsules from the hemlock looper ( Lambdina fiscellaria) and the spruce budworm ( Choristoneura fumiferana), absence of hemlock fruiting remains, and tree-ring anomalies in fossil hemlocks that died prematurely (<165 yr) suggest that defoliation affected hemlock reproductive capacity and pollen productivity, or more likely caused mass mortality. Our findings indicate that defoliation can affect ecosystems for centuries, especially when long-lived tree species are involved.

  16. Holocene Climate Change in Arctic Canada and Greenland

    NASA Astrophysics Data System (ADS)

    Briner, J. P.; McKay, N.; Axford, Y.; Bennike, O.; Bradley, R. S.; de Vernal, A.; Fisher, D. A.; Francus, P.; Fréchette, B.; Gajewski, K. J.; Jennings, A. E.; Kaufman, D. S.; Miller, G. H.; Rouston, C.; Wagner, B.

    2015-12-01

    We summarize the spatial and temporal pattern of climate change through the Holocene in Arctic Canada and Greenland. Our synthesis includes 47 records from a recent database of highly resolved, quantitative Holocene climate records from the Arctic (Sundqvist et al., 2014). We plot the temperature histories represented by the records in the database and compare them with paleoclimate information based on 53 additional records. Combined, the records include a variety of climate proxy types that range from ice (ice cores), land (lake and peat sequences) and marine (ocean sediment cores and coastal sediments) environments. The temperature-sensitive records indicate more consistent and earlier Holocene warmth in the north and east, and a more diffuse and later Holocene thermal maximum in the south and west. Principal components analysis reveals two dominant Holocene trends, one with early Holocene warmth followed by cooling in the middle Holocene, the other with a broader period of warmth in the middle Holocene followed by cooling in the late Holocene. The temperature decrease from the warmest to the coolest portions of the Holocene is 3.0±1.0°C on average (n=11 records). The Greenland Ice Sheet retracted to its minimum extent between 5 and 3 ka, consistent with many sites from around Greenland depicting a switch from warm to cool conditions around that time. The spatial pattern of temperature change through the Holocene was likely driven by the decrease in northern latitude summer insolation through the Holocene, the varied influence of waning ice sheets in the early Holocene, and the variable influx of Atlantic Water into the study region.

  17. Spectroscopy, morphometry, and photoclinometry of Titan's dunefields from Cassini/VIMS

    USGS Publications Warehouse

    Barnes, J.W.; Brown, R.H.; Soderblom, L.; Sotin, C.; Le, Mouelic S.; Rodriguez, S.; Jaumann, R.; Beyer, R.A.; Buratti, B.J.; Pitman, K.; Baines, K.H.; Clark, R.; Nicholson, P.

    2008-01-01

    Fine-resolution (500 m/pixel) Cassini Visual and Infrared Mapping Spectrometer (VIMS) T20 observations of Titan resolve that moon's sand dunes. The spectral variability in some dune regions shows that there are sand-free interdune areas, wherein VIMS spectra reveal the exposed dune substrate. The interdunes from T20 are, variously, materials that correspond to the equatorial bright, 5-??m-bright, and dark blue spectral units. Our observations show that an enigmatic "dark red" spectral unit seen in T5 in fact represents a macroscopic mixture with 5-??m-bright material and dunes as its spectral endmembers. Looking more broadly, similar mixtures of varying amounts of dune and interdune units of varying composition can explain the spectral and albedo variability within the dark brown dune global spectral unit that is associated with dunes. The presence of interdunes indicates that Titan's dunefields are both mature and recently active. The spectrum of the dune endmember reveals the sand to be composed of less water ice than the rest of Titan; various organics are consistent with the dunes' measured reflectivity. We measure a mean dune spacing of 2.1 km, and find that the dunes are oriented on the average in an east-west direction, but angling up to 10?? from parallel to the equator in specific cases. Where no interdunes are present, we determine the height of one set of dunes photoclinometrically to be between 30 and 70 m. These results pave the way for future exploration and interpretation of Titan's sand dunes. ?? 2007 Elsevier Inc. All rights reserved.

  18. Coastal dynamics under conditions of rapid sea-level rise: Late Pleistocene to Early Holocene evolution of barrier lagoon systems on the northern Adriatic shelf (Italy)

    NASA Astrophysics Data System (ADS)

    Storms, Joep E. A.; Weltje, Gert Jan; Terra, Guido J.; Cattaneo, Antonio; Trincardi, Fabio

    2008-06-01

    This multidisciplinary case study of two preserved barrier systems combined the analysis of radiocarbon datings, grain-size distributions, high-resolution seismics, and shelf bathymetry with reconstructions of palaeo-environmental conditions (tides, waves, sea-level change) and forward modelling of barrier-lagoon systems, to provide an integrated view of the coastal transgressive evolution of a large sector of the northern Adriatic shelf between 15 and 8 ka BP. Palaeo-environmental reconstructions point to increased tidal amplitude, low-energy wave climate and high rates of sea-level rise (up to 60 mm/a) during the formation of the oldest preserved barrier system (˜90 m water depth; 14.3 cal ka BP). A younger barrier system (42 m water depth; 10.5 cal ka BP) formed under conditions of lower tidal amplitude, higher wave energy and a lower rate of sea-level rise (10 mm/a). Forward modelling suggests that the probability of barrier-island overstepping during transgression is inversely proportional to tidal amplitude, if all other factors are assumed equal. The oldest barrier-lagoon system developed under conditions of large tidal amplitude, which permitted rapid transgression. However, this system apparently failed to keep up with the anomalously high rate of sea-level rise resulting from melt-water pulse 1A. The youngest barrier system appears to have drowned in place due to antecedent topography. As the barrier system transgressed over an ancient Pleistocene alluvial plain, the rapid increase in backbarrier accommodation caused an abrupt disequilibrium between shoreface and backbarrier sedimentation, which led to barrier overstepping. Although BarSim modelling indicates that tidal deposition can reduce the probability of barrier overstepping, there are other driving mechanisms (in our case extremely rapid sea-level rise and antecedent topography), which are more determinative in explaining the transgressive coastal evolution of barrier-lagoon systems in the

  19. Coastal resilience and late Holocene tidal inlet history: The evolution of Dungeness Foreland and the Romney Marsh depositional complex (U.K.)

    NASA Astrophysics Data System (ADS)

    Long, A. J.; Waller, M. P.; Plater, A. J.

    2006-12-01

    Dungeness Foreland is a large sand and gravel barrier located in the eastern English Channel that during the last 5000 years has demonstrated remarkable geomorphological resilience in accommodating changes in relative sea-level, storm magnitude and frequency, variations in sediment supply as well as significant changes in back-barrier sedimentation. In this paper we develop a new palaeogeographic model for this depositional complex using a large dataset of recently acquired litho-, bio- and chrono-stratigraphic data. Our analysis shows how, over the last 2000 years, three large tidal inlets have influenced the pattern of back-barrier inundation and sedimentation, and controlled the stability and evolution of the barrier by determining the location of cross-shore sediment and water exchange, thereby moderating sediment supply and its distribution. The sheer size of the foreland has contributed in part to its resilience, with an abundant supply of sediment always available for ready redistribution. A second reason for the landform's resilience is the repeated ability of the tidal inlets to narrow and then close, effectively healing successive breaches by back-barrier sedimentation and ebb- and/or flood-tidal delta development. Humans emerge as key agents of change, especially through the process of reclamation which from the Saxon period onwards has modified the back-barrier tidal prism and promoted repeated episodes of fine-grained sedimentation and channel/inlet infill and closure. Our palaeogeographic reconstructions show that large barriers such as Dungeness Foreland can survive repeated "catastrophic" breaches, especially where tidal inlets are able to assist the recovery process by raising the elevation of the back-barrier area by intertidal sedimentation. This research leads us to reflect on the concept of "coastal resilience" which, we conclude, means little without a clearly defined spatial and temporal framework. At a macro-scale, the structure as a whole

  20. A 700 year record of combustion-derived pollution in northern Spain: tools to identify the Holocene/Anthropocene transition in coastal environments.

    PubMed

    Leorri, Eduardo; Mitra, Siddhartha; Irabien, María Jesús; Zimmerman, Andrew R; Blake, William H; Cearreta, Alejandro

    2014-02-01

    There is an uneven geographical distribution of historic records of atmospheric pollutants from SW Europe and those that exist are very limited in temporal extent. Alternative data source is required to understand temporal trends in human impacts on atmospheric pollution. Polycyclic aromatic hydrocarbons (PAHs), heavy metal content and stable Pb isotopic ratios in a sediment core from a salt marsh in northern Spain were used to reconstruct the regional history of contaminant inputs over the last 700 years. Pre-1800s concentrations of Pb and PAHs represented baseline concentrations, i.e. pre-Industrial, conditions. During the initial stages of the Industrial Revolution, 1800s to 1860s, PAH concentrations increased by a factor of about two above baseline levels in the sediment column. By the 1930s, PAH levels reached ca. 10 times pre-Industrial levels and, along with Pb, reached a peak at ca. 1975 CE. Since then, sedimentary PAH and Pb concentrations decreased significantly. A combination of PAH isomer and Pb stable isotope ratios suggests that the contaminant sources are regional, likely derived partially from wood, but mainly coal used by the metallurgic industry in the Basque country since the 1800s and until the 1970s when leaded petrol saw increased use. This chronology of regional atmosphere-derived pollution expands current southwest Europe emission records and shows coastal salt marsh sediments to be useful in reconstructing the Anthropocene. © 2013.

  1. Coastal Evolution in a Mediterranean Microtidal Zone: Mid to Late Holocene Natural Dynamics and Human Management of the Castelló Lagoon, NE Spain

    PubMed Central

    Ejarque, Ana; Julià, Ramon; Reed, Jane M.; Mesquita-Joanes, Francesc; Marco-Barba, Javier; Riera, Santiago

    2016-01-01

    We present a palaeoenvironmental study of the Castelló lagoon (NE Spain), an important archive for understanding long-term interactions between dynamic littoral ecosystems and human management. Combining geochemistry, mineralogy, ostracods, diatoms, pollen, non-pollen palynomorphs, charcoal and archaeo-historical datasets we reconstruct: 1) the transition of the lagoon from a marine to a marginal environment between ~3150 cal BC to the 17th century AD; 2) fluctuations in salinity; and 3) natural and anthropogenic forces contributing to these changes. From the Late Neolithic to the Medieval period the lagoon ecosystem was driven by changing marine influence and the land was mainly exploited for grazing, with little evidence for impact on the natural woodland. Land-use exploitation adapted to natural coastal dynamics, with maximum marine flooding hampering agropastoral activities between ~1550 and ~150 cal BC. In contrast, societies actively controlled the lagoon dynamics and become a major agent of landscape transformation after the Medieval period. The removal of littoral woodlands after the 8th century was followed by the expansion of agrarian and industrial activities. Regional mining and smelting activities polluted the lagoon with heavy metals from the ~11th century onwards. The expansion of the milling industry and of agricultural lands led to the channelization of the river Muga into the lagoon after ~1250 cal AD. This caused its transformation into a freshwater lake, increased nutrient load, and the infilling and drainage of a great part of the lagoon. By tracking the shift towards an anthropogenically-controlled system around ~750 yr ago, this study points out Mediterranean lagoons as ancient and heavily-modified systems, with anthropogenic impacts and controls covering multi-centennial and even millennial timescales. Finally, we contributed to the future construction of reliable seashell-based chronologies in NE Spain by calibrating the Banyuls-sur-Mer

  2. A Four Lake Latitudinal Comparison Along Coastal Southern to Central California: A Late-Holocene Perspective on the Western US Precipitation Dipole.

    NASA Astrophysics Data System (ADS)

    Kirby, M.; Nichols, K. E.; Ramezan, R.; Palermo, J. A.; Hiner, C.; Bonuso, N.; Patterson, W. P.; Silveira, E.

    2016-12-01

    One of the dominant hydroclimatic features of the western United States is the winter season precipitation dipole. The dipole is characterized by a N-S antiphased precipitation regime presently centered on 40° N latitude (Cayan et al., 1998; Dettinger et al., 1998; Wise, 2010). For example, the position of the dipole dictates where CA receives its winter precipitation; thus, it is critical to understand the dipole from a paleoperspective, which at present is poorly known. Here, we present four lake sites spanning 33°-36° N latitude along coastal CA. These sites include: Lake Elsinore, Crystal Lake, Zaca Lake, and Abbott Lake. All four of these sites are located south of the dipole's average historic (since 1950 AD) latitude. The predominant hydroclimatic indicator is similar for each basin (i.e., grain size); although, several other indicators are used for independent verification/assessment of the grain size interpretation. Notably, these lakes contain varied age control, which limits site-to-site correlation without consideration of age model dependence. Following a Bayesian framework, MCMC algorithms in conjuction with radiocarbon dating will be used to estimate timestamps of sediment deposits with a degree of statistical uncertainty. Samples from the posterior distribution will be used to correlate hydroclimatic features between sites. Included in this analysis are tree ring records from the region to assess the similarities and differences as recorded in annually resolved tree ring drought reconstructions and decadally resolved lake sediment hydroclimatic records. Finally, the four sites are assessed in the context of tropical and north Pacific SST forcing.

  3. Coastal Evolution in a Mediterranean Microtidal Zone: Mid to Late Holocene Natural Dynamics and Human Management of the Castelló Lagoon, NE Spain.

    PubMed

    Ejarque, Ana; Julià, Ramon; Reed, Jane M; Mesquita-Joanes, Francesc; Marco-Barba, Javier; Riera, Santiago

    2016-01-01

    We present a palaeoenvironmental study of the Castelló lagoon (NE Spain), an important archive for understanding long-term interactions between dynamic littoral ecosystems and human management. Combining geochemistry, mineralogy, ostracods, diatoms, pollen, non-pollen palynomorphs, charcoal and archaeo-historical datasets we reconstruct: 1) the transition of the lagoon from a marine to a marginal environment between ~3150 cal BC to the 17th century AD; 2) fluctuations in salinity; and 3) natural and anthropogenic forces contributing to these changes. From the Late Neolithic to the Medieval period the lagoon ecosystem was driven by changing marine influence and the land was mainly exploited for grazing, with little evidence for impact on the natural woodland. Land-use exploitation adapted to natural coastal dynamics, with maximum marine flooding hampering agropastoral activities between ~1550 and ~150 cal BC. In contrast, societies actively controlled the lagoon dynamics and become a major agent of landscape transformation after the Medieval period. The removal of littoral woodlands after the 8th century was followed by the expansion of agrarian and industrial activities. Regional mining and smelting activities polluted the lagoon with heavy metals from the ~11th century onwards. The expansion of the milling industry and of agricultural lands led to the channelization of the river Muga into the lagoon after ~1250 cal AD. This caused its transformation into a freshwater lake, increased nutrient load, and the infilling and drainage of a great part of the lagoon. By tracking the shift towards an anthropogenically-controlled system around ~750 yr ago, this study points out Mediterranean lagoons as ancient and heavily-modified systems, with anthropogenic impacts and controls covering multi-centennial and even millennial timescales. Finally, we contributed to the future construction of reliable seashell-based chronologies in NE Spain by calibrating the Banyuls-sur-Mer

  4. Palaeoenvironmental reconstructions from linear dunefields: recent progress, current challenges and future directions

    NASA Astrophysics Data System (ADS)

    Telfer, M. W.; Hesse, P. P.

    2013-10-01

    This paper reviews recent progress in the use of linear dunes as ‘geoproxies' of late Quaternary environmental change, summarises the challenges facing their use, and explores some potential solutions to these challenges. Large areas of the swathes of linear dunes which occupy the continental interior of southern Africa, Australia, and parts of central Asia and southern America currently have limited or negligible aeolian activity. They have been recognised as offering potential information about past environments for more than a century, but only with the widespread application of luminescence dating during the 1990s did they realistically start to offer the prospect of being an extensive, dateable proxy of late Quaternary palaeoenvironments and, possibly, palaeoclimates. Dating aeolian dune sands with luminescence methods is generally (although not always) relatively straightforward. Over the past twenty years, a large number (>1000) of luminescence ages have been added to the global dataset, yet there has also been significant criticism of some of the rationale underpinning much of the interpretation of the records derived. At the landscape scale, developments of arguably equal importance have come from improved geomorphological understanding based on the wider availability of remotely-sensed data and the paradigm of dunefield evolution as a self-organising complex system. Current challenges are identified in three key regions: incomplete understanding of how the process geomorphology of linear dunes affect the accumulation and preservation of sediment, a lack of clarity regarding the temporal and spatial scale of the response in a dynamic environmental setting and uncertainty surrounding the drivers of changing rates of net accumulation. Solutions to these challenges lie within diverse research methodologies. Certainly, further field study is required, with improvement required in understanding system responses to changing environmental stimuli at scales from

  5. Linking restoration ecology with coastal dune restoration

    NASA Astrophysics Data System (ADS)

    Lithgow, D.; Martínez, M. L.; Gallego-Fernández, J. B.; Hesp, P. A.; Flores, P.; Gachuz, S.; Rodríguez-Revelo, N.; Jiménez-Orocio, O.; Mendoza-González, G.; Álvarez-Molina, L. L.

    2013-10-01

    Restoration and preservation of coastal dunes is urgently needed because of the increasingly rapid loss and degradation of these ecosystems because of many human activities. These activities alter natural processes and coastal dynamics, eliminate topographic variability, fragment, degrade or eliminate habitats, reduce diversity and threaten endemic species. The actions of coastal dune restoration that are already taking place span contrasting activities that range from revegetating and stabilizing the mobile substrate, to removing plant cover and increasing substrate mobility. Our goal was to review how the relative progress of the actions of coastal dune restoration has been assessed, according to the ecosystem attributes outlined by the Society of Ecological Restoration: namely, integrity, health and sustainability and that are derived from the ecological theory of succession. We reviewed the peer reviewed literature published since 1988 that is listed in the ISI Web of Science journals as well as additional references, such as key books. We exclusively focused on large coastal dune systems (such as transgressive and parabolic dunefields) located on natural or seminatural coasts. We found 150 articles that included "coastal dune", "restoration" and "revegetation" in areas such as title, keywords and abstract. From these, 67 dealt specifically with coastal dune restoration. Most of the studies were performed in the USA, The Netherlands and South Africa, during the last two decades. Restoration success has been assessed directly and indirectly by measuring one or a few ecosystem variables. Some ecosystem attributes have been monitored more frequently (ecosystem integrity) than others (ecosystem health and sustainability). Finally, it is important to consider that ecological succession is a desirable approach in restoration actions. Natural dynamics and disturbances should be considered as part of the restored system, to improve ecosystem integrity, health and

  6. The Holocene temperature conundrum

    PubMed Central

    Liu, Zhengyu; Zhu, Jiang; Rosenthal, Yair; Zhang, Xu; Otto-Bliesner, Bette L.; Timmermann, Axel; Smith, Robin S.; Lohmann, Gerrit; Zheng, Weipeng; Elison Timm, Oliver

    2014-01-01

    A recent temperature reconstruction of global annual temperature shows Early Holocene warmth followed by a cooling trend through the Middle to Late Holocene [Marcott SA, et al., 2013, Science 339(6124):1198–1201]. This global cooling is puzzling because it is opposite from the expected and simulated global warming trend due to the retreating ice sheets and rising atmospheric greenhouse gases. Our critical reexamination of this contradiction between the reconstructed cooling and the simulated warming points to potentially significant biases in both the seasonality of the proxy reconstruction and the climate sensitivity of current climate models. PMID:25114253

  7. The Holocene temperature conundrum.

    PubMed

    Liu, Zhengyu; Zhu, Jiang; Rosenthal, Yair; Zhang, Xu; Otto-Bliesner, Bette L; Timmermann, Axel; Smith, Robin S; Lohmann, Gerrit; Zheng, Weipeng; Elison Timm, Oliver

    2014-08-26

    A recent temperature reconstruction of global annual temperature shows Early Holocene warmth followed by a cooling trend through the Middle to Late Holocene [Marcott SA, et al., 2013, Science 339(6124):1198-1201]. This global cooling is puzzling because it is opposite from the expected and simulated global warming trend due to the retreating ice sheets and rising atmospheric greenhouse gases. Our critical reexamination of this contradiction between the reconstructed cooling and the simulated warming points to potentially significant biases in both the seasonality of the proxy reconstruction and the climate sensitivity of current climate models.

  8. A linear dune dam - a unique late Pleistocene aeolian-fluvial archive bordering the northwestern Negev Desert dunefield, Israel

    NASA Astrophysics Data System (ADS)

    Roskin, Joel; Bookman, Revital; Friesem, David; Vardi, Jacob

    2016-04-01

    Interactions between aeolian and fluvial processes, known as aeolian-fluvial (A-F) interactions, play a fundamental role in shaping the surface of the Earth especially in arid zones. The blocking of wadis by dunes (dune-damming) is an A-F interaction that is perceived to be an archive of periods of aeolian 'superiority' on fluvial transport power and has had a strong impact on arid landscapes and prehistoric man since the late Quaternary. The southern fringes of the northwestern Negev dunefield are lined with discontinuous surfaces of light-colored, playa-like, low-energy, fine-grained fluvial deposits (LFFDs). Abundant Epipalaeolithic camp sites mainly border the LFFDs. The LFFDs are understood to be reworked loess-like sediment deposited in short-lived shallow water bodies during the late Pleistocene. These developed adjacently upstream of hypothesized dune dams of wadis that drain the Negev highlands. However, no dune dam structures by the LFFDs have been explicitly identified or analyzed. This paper presents for the first time the morphology, stratigraphy and sedimentology of a hypothesized dune dam. The studied linear-like dune dam structure extends west-east for several hundred meters, has an asymmetric cross-section and is comprised of two segments. In the west, the structure is 3-5 m high, 80 m wide, with a steep southern slope, and is covered by pebbles. Here, its morphology and orientation resembles the prevailing vegetated linear dunes (VLDs) of the adjacent dunefield though its slope angles differ from VLDs. To the south of the structure extends a thick LFFD sequence. In the east the structure flattens and is covered by nebkhas with its southern edge overlapped by LFFD units. The structures' stratigraphy is found to be comprised of a thick LFFD base, overlaid by aeolian and fluvially reworked sand, a thin middle LFFD unit, and a crest comprised of LFFDs, fluvial sand and pebbles. Carbonate contents and particle size distributions of the sediments easily

  9. A late Pleistocene linear dune dam record of aeolian-fluvial dynamics at the fringes of the northwestern Negev dunefield

    NASA Astrophysics Data System (ADS)

    Roskin, Joel; Bookman, Revital; Friesem, David E.; Vardi, Jacob

    2017-05-01

    A late Pleistocene aeolian-fluvial record within a rare vegetated linear dune-like structure at the fringe of the northwestern Negev dunefield, Israel, provides direct evidence of dune-damming dynamics within the structure and its environs. Study methods included high resolution morphology and stratigraphy, micromorphology and sedimentological analyses. Chronology was based on eight archaeological sites from the structure and the INQUA Dune Atlas chronologic database. Low-energy fine-grained fluvial deposits underlying the structure and extending from its flanks indicate deposition by low energy hyper-concentrated flows in a floodplain environment and later in water bodies that formed by dune-damming of a mid-sized drainage basin. Interbedded sand with fine-grained deposits within the linear structure indicates interchanging dominances between aeolian sand incursion and seasonal floods. Sand deposition during dune elongation led to structure growth and dune-damming of its drainage system that in turn formed water bodies and upstream fine-grained deposition following seasonal floods. Calculations of current sediment yields indicate that fine-grained deposits accretion up to the structure's brim could possibly have rapidly occurred over a total time span of decades. However, artifacts dating to the Geometric Kebaran ( 17.5-12.9 cal kyr BP) and Harifian (12.9-11.2 cal kyr BP) archaeological periods on the structure's surface indicates intermittent, repetitive, and short-term camping, utilizing adjacent water bodies over a time period of 4000-5000 years. Fluctuating high winds and precipitation during a time window of increased fluvial availability of fine-grained sediment from the hinterland generated ample fine-grained deposition. After 11 cal kyr BP, the abundance and recurrence of dammed water bodies decreased when reduced wind power constrained dune-dam maintenance. After sediment accommodation space dissipated, fluvial flow of the drainage basin led to dune

  10. New data on the Holocene evolution of the Dvina Bay (White Sea)

    NASA Astrophysics Data System (ADS)

    Novichkova, Ye. A.; Reikhard, L. Ye.; Lisitzin, A. P.; Rybalko, A. Ye.; de Vernal, A.

    2017-05-01

    The Holocene sediments from the inner part of the Dvina Bay of the White Sea (core no. 6042) were analyzed with multidisciplinary methods for the first time. The age of the sediments was determined using biostratigraphy and AMS 14C method. The result of analytical studies indicate two major stages of sedimentation in the bay during the Holocene. The water masses parameters were reconstructed and the results were compared with the modern data on the coastal sediments of the White Sea region.

  11. Facies characterization and sequential evolution of an ancient offshore dunefield in a semi-enclosed sea: Neuquén Basin, Argentina

    NASA Astrophysics Data System (ADS)

    Veiga, Gonzalo D.; Schwarz, Ernesto

    2017-08-01

    This study analyses a 30-m-thick, sand-dominated succession intercalated between offshore mudstones in the Lower Cretaceous record of the Neuquén Basin, Argentina, defining facies associated with unidirectional currents as sand dunes (simple and compound), rippled sand sheets and heterolithic sheets. These facies associations are related to the development of an offshore, forward-accreting dunefield developed as a response to the onset of a tidal-transport system. The reported stratigraphic record results from the combination of the gradual downcurrent decrease of the current speed together with the long-term climbing of the entire system. Maximum amplification of the tidal effect associated with incoming oceanic tides to this epicontinental sea would develop at the time of more efficient connection between the basin and the open ocean. Thus, the onset of the offshore tidal system approximately corresponds to the time of maximum flooding conditions (or immediately after). The short-term evolution of the tidal-transport system is more complex and characterized by the vertical stacking of small-scale cycles defined by the alternation of episodes of construction and destruction of the dunefield. The development of these cycles could be the response to changes in tidal current speed and transport capacity.

  12. Facies characterization and sequential evolution of an ancient offshore dunefield in a semi-enclosed sea: Neuquén Basin, Argentina

    NASA Astrophysics Data System (ADS)

    Veiga, Gonzalo D.; Schwarz, Ernesto

    2016-08-01

    This study analyses a 30-m-thick, sand-dominated succession intercalated between offshore mudstones in the Lower Cretaceous record of the Neuquén Basin, Argentina, defining facies associated with unidirectional currents as sand dunes (simple and compound), rippled sand sheets and heterolithic sheets. These facies associations are related to the development of an offshore, forward-accreting dunefield developed as a response to the onset of a tidal-transport system. The reported stratigraphic record results from the combination of the gradual downcurrent decrease of the current speed together with the long-term climbing of the entire system. Maximum amplification of the tidal effect associated with incoming oceanic tides to this epicontinental sea would develop at the time of more efficient connection between the basin and the open ocean. Thus, the onset of the offshore tidal system approximately corresponds to the time of maximum flooding conditions (or immediately after). The short-term evolution of the tidal-transport system is more complex and characterized by the vertical stacking of small-scale cycles defined by the alternation of episodes of construction and destruction of the dunefield. The development of these cycles could be the response to changes in tidal current speed and transport capacity.

  13. Geometry and evolution of Holocene transgressive and regressive barriers on the semi-arid coast of NE Brazil

    NASA Astrophysics Data System (ADS)

    Henrique de Oliveira Caldas, Luciano; Gomes de Oliveira, Josibel; Eugênio de Medeiros, Walter; Stattegger, Karl; Vital, Helenice

    2006-11-01

    An integrated study based on ground penetrating radar (GPR) profiles, vibracore descriptions, water-well logs, and radiocarbon dating in a coastal deposit located in the northern region of Rio Grande do Norte State, northeastern Brazil, allowed us to identify Holocene transgressive and regressive barriers. The construction process for the studied coastal barrier is different from that proposed for the Holocene coastal plains along the eastern Brazilian coast, where the hydraulic barrier set up by large rivers for sediments transported by longshore currents has caused a strongly positive longshore sediment imbalance. In the study area, interpretation of the GPR images, within the constraints of vibracores data, allowed us to interpret five radar facies and four radar boundary sequences for these coastal deposits, which were built up during the Holocene coastal evolution of the region. As a result, the geometry of the coastal barrier was reconstructed. Based on barrier geometry, sediment ages, stratigraphic records, and sedimentation patterns, we propose a barrier evolutionary model for the Holocene for the study region. During the Holocene highstand, a transgressive barrier was deposited and a lagoon extended landward. During the sea-level fall soon after the Holocene highstand, the deposition of a regressive barrier (forced regression) started. This deposition was induced by the coastal geometry and high amounts of eolian sediments supplied by east-northeast winds. Also during this period of sea-level fall, the beach face became wider, and thus more subjected to wind action, facilitating the deposition of the first eolian deposits. These sediments were transported to the nearly formed embayment, providing a surplus for the construction of the regressive barrier. During the regressive phase, tidal channels closed and the lagoon became isolated from the open sea. The geometry of both the regressive and transgressive barriers as well as the stratigraphic relation

  14. A Late Pleistocene linear dune dam record of aeolian-fluvial dynamics at the fringes of the northwestern Negev dunefield

    NASA Astrophysics Data System (ADS)

    Roskin, Joel; Bookman, Revital; Friesem, David; Vardi, Jacob

    2017-04-01

    The paper presents a late Pleistocene aeolian-fluvial record within a linear dune-like structure that partway served as a dune dam. Situated along the southern fringe of the northwestern Negev desert dunefield (Israel) the structure's morphology, orientation, and some of its stratigraphic units partly resemble adjacent west-east extending vegetated linear dunes. Uneven levels of light-colored, fine-grained fluvial deposits (LFFDs) extend to the north and south from the flanks of the studied structure. Abundant Epipalaeolithic sites line the fringes of the LFFDs. The LFFD microstructures of fine graded bedding and clay blocky peds indicate sorting and shrinking of saturated clays in transitional environments between low energy flows to shallow standing water formed by dunes damming a mid-sized drainage system. The structure's architecture of interchanging units of sand with LFFDs indicates interchanging dominances between aeolian sand incursion and winter floods. Sand mobilization associated with powerful winds during the Heinrich 1 event led to dune damming downstream of the structure and within the structure to in-situ sand deposition, partial fluvial erosion, reworking of the sand, and LFFD deposition. Increased sand deposition led to structure growth and blockage of its drainage system that in turn accumulated LFFD units up stream of the structure. Extrapolation of current local fluvial sediment yields indicate that LFFD accretion up to the structure's brim occurred over a short period of several decades. Thin layers of Geometric Kebaran (c. 17.5-14.5 ka cal BP) to Harifian (12-11 ka BP) artifacts within the structure's surface indicates intermittent, repetitive, and short term camping utilizing adjacent water along a timespan of 4-6 kyr. The finds directly imply that the NW Negev LFFDs formed in dune-dammed water bodies which themselves were formed following events of vegetated linear dune elongation. LFFD accumulation persisted as a result of dune dam

  15. Geomorphic Process from Topographic Form: Automating the Interpretation of Repeat Survey Data to Understand Sediment Connectivity for Source-Bordering Aeolian Dunefields in River Valleys

    NASA Astrophysics Data System (ADS)

    Sankey, J. B.; Kasprak, A.; Caster, J.

    2016-12-01

    Aeolian geomorphologists can readily describe landscape change by contrasting repeat topographic surveys, a method termed geomorphic change detection, thanks to the ubiquity of high resolution topographic data. However, change detection alone does not attribute changes to geomorphic processes; that is, the reasons why change occurred are not explicitly revealed. This process attribution, known as `mechanistic segregation' is typically completed via manual attribution, a method that is time consuming and may be quite subjective. Here we present a novel, automated, two-part method for mechanistic segregation of changes in DEMs of Difference (DoDs) that is both reproducible and computationally efficient. Part 1 employs a landscape-based approach (LBA), wherein we use topographic characteristics from repeat surveys to predict primary and secondary geomorphic transport mechanisms for an area of interest. Part 2 uses morphometry of geomorphic change in a DoD-based approach (DBA) to predict a single geomorphic mechanism. The results of both methods are then evaluated for commonality to assess our confidence in each prediction. We evaluated this approach at 113 discrete sample points within seven source-bordering aeolian dunefields undergoing a combination of fluvial, aeolian, and hillslope geomorphic processes along the Colorado River in Grand Canyon, Arizona. The LBA and DBA performed well independently, but the combined results provided the greatest degree of agreement with field observations (>90%). These methods have proved useful for sediment budgeting, where we confirm spatial and temporal patterns in sediment flux consistent with previously published results. We anticipate that this approach will be reproducible at multiple spatial scales (e.g., 102-106 m2) and adaptable to other river valleys where the interactions of aeolian, fluvial, and hillslopes processes drives sediment connectivity for source-bordering aeolian dunefields.

  16. The history of the mangrove vegetation in Bénin during the Holocene: A palynological study

    NASA Astrophysics Data System (ADS)

    Tossou, M. G.; Akoègninou, A.; Ballouche, A.; Sowunmi, M. A.; Akpagana, K.

    2008-11-01

    Pollen analysis of three core samples,YEV-I, GOHO.00 and DO.00, taken in the coastal area of Bénin shows the existence of mangrove during the Holocene. This mangrove underwent many physiognomic changes from the middle to the late Holocene. In the course of the middle Holocene (from 7500 to 2500 years before present (BP)), it stretched over a large area from the littoral inland. It was tightly closed and almost monospecific, dominated by Rhizophora. During the late Holocene, this mangrove started to regress around 3000 years BP and disappeared about 2500 years BP from the studied sites. It has been replaced by swamp meadows dominated by Paspalum vaginatum Sw. and a fresh water environment colonised by taxa such as Persicaria, Typha, Ludwigia, and Nymphaea.

  17. Holocene aridification of India

    USGS Publications Warehouse

    Ponton, C.; Giosan, L.; Eglinton, T.I.; Fuller, D.Q.; Johnson, J.E.; Kumar, P.; Collett, T.S.

    2012-01-01

    Spanning a latitudinal range typical for deserts, the Indian peninsula is fertile instead and sustains over a billion people through monsoonal rains. Despite the strong link between climate and society, our knowledge of the long-term monsoon variability is incomplete over the Indian subcontinent. Here we reconstruct the Holocene paleoclimate in the core monsoon zone (CMZ) of the Indian peninsula using a sediment core recovered offshore from the mouth of Godavari River. Carbon isotopes of sedimentary leaf waxes provide an integrated and regionally extensive record of the flora in the CMZ and document a gradual increase in aridity-adapted vegetation from ???4,000 until 1,700 years ago followed by the persistence of aridity-adapted plants after that. The oxygen isotopic composition of planktonic foraminifer Globigerinoides ruber detects unprecedented high salinity events in the Bay of Bengal over the last 3,000 years, and especially after 1,700 years ago, which suggest that the CMZ aridification intensified in the late Holocene through a series of sub-millennial dry episodes. Cultural changes occurred across the Indian subcontinent as the climate became more arid after ???4,000 years. Sedentary agriculture took hold in the drying central and south India, while the urban Harappan civilization collapsed in the already arid Indus basin. The establishment of a more variable hydroclimate over the last ca. 1,700 years may have led to the rapid proliferation of water-conservation technology in south India. Copyright 2012 by the American Geophysical Union.

  18. Holocene aridification of India

    NASA Astrophysics Data System (ADS)

    Ponton, Camilo; Giosan, Liviu; Eglinton, Tim I.; Fuller, Dorian Q.; Johnson, Joel E.; Kumar, Pushpendra; Collett, Tim S.

    2012-02-01

    Spanning a latitudinal range typical for deserts, the Indian peninsula is fertile instead and sustains over a billion people through monsoonal rains. Despite the strong link between climate and society, our knowledge of the long-term monsoon variability is incomplete over the Indian subcontinent. Here we reconstruct the Holocene paleoclimate in the core monsoon zone (CMZ) of the Indian peninsula using a sediment core recovered offshore from the mouth of Godavari River. Carbon isotopes of sedimentary leaf waxes provide an integrated and regionally extensive record of the flora in the CMZ and document a gradual increase in aridity-adapted vegetation from ˜4,000 until 1,700 years ago followed by the persistence of aridity-adapted plants after that. The oxygen isotopic composition of planktonic foraminifer Globigerinoides ruber detects unprecedented high salinity events in the Bay of Bengal over the last 3,000 years, and especially after 1,700 years ago, which suggest that the CMZ aridification intensified in the late Holocene through a series of sub-millennial dry episodes. Cultural changes occurred across the Indian subcontinent as the climate became more arid after ˜4,000 years. Sedentary agriculture took hold in the drying central and south India, while the urban Harappan civilization collapsed in the already arid Indus basin. The establishment of a more variable hydroclimate over the last ca. 1,700 years may have led to the rapid proliferation of water-conservation technology in south India.

  19. Holocene estuary development in the Algarve Region (Southern Portugal)

    NASA Astrophysics Data System (ADS)

    Schneider, Heike; Höfer, Dana; Trog, Carmen; Hempel, Rita; Daut, Gerhard; Mäusbacher, Roland

    2010-05-01

    Former coastal estuaries in the Algarve region of South Portugal are used for reconstruction coastal evolution since first marine transgression processes at about 8.000 years before. The sediments of these archives allow high resolution analyses of geochemical and palynological signals. Drillings in different lagoons of the Algarve region contain the sequences from the fluvial sediments during the early Holocene, marine transgression facies during the middle Holocene and the marine/fluvial sediment deposits until present. The results of the sedimentological, geochemical and palynological analyses show that each estuary developed differently, depending on the morphology of the paleovalley, environmental conditions and especially the influence of the sea and the formation of barrier systems. The estuaries were flooded between 7500 and 5500 cal a BP by sea level rise and were almost completely filled by sediment by the beginning of the Roman occupation (226 y BC / 2176 cal a BP). A clear change in sedimentological processes is evident in the estuaries between 5500 and 3000 cal a BP and is interpreted as a result of high energy events such as storms or tsunamis (Schneider et al. 2009, Hilbich et al. 2008 ). Palynological as well as archaeological investigations show distinct anthropogenic influences since 3500 cal. BP by increasing values in maquies, cereals and open land communities. References Hilbich, C., Mügler, I., Daut, G., Frenzel, P., van der Borg, K., Mäusbacher, R. (2008): Reconstruction of the depositional history of the former coastal lagoon of Vilamoura (Algarve, Portugal): A sedimentological, microfaunal and geophysical approach.- Journal of Coastal Research 24(2B), 83-91. Schneider, H., Höfer, D., Trog, C., Busch, S., Schneider, M., Baade, J., Daut, G. & R. Mäusbacher (2009): Holocene estuary development in the Algarve Region (Southern Portugal) - A reconstruction of sedimentological and ecological evolution. - Quaternary International (In Press

  20. Tropical Peat and Peatland Development in the Floodplains of the Greater Pamba Basin, South-Western India during the Holocene

    PubMed Central

    Padmalal, Damodaran; Limaye, Ruta B.; S., Vishnu Mohan; Jennerjahn, Tim; Gamre, Pradeep G.

    2016-01-01

    Holocene sequences in the humid tropical region of Kerala, South-western (SW) India have preserved abundance of organic—rich sediments in the form of peat and its rapid development in a narrow time frame towards Middle Holocene has been found to be significant. The sub—coastal areas and flood plains of the Greater Pamba Basin have provided palaeorecords of peat indicating that the deposits are essentially formed within freshwater. The combination of factors like stabilized sea level and its subsequent fall since the Middle Holocene, topographic relief and climatic conditions led to rapid peat accumulation across the coastal lowlands. The high rainfall and massive floods coupled with a rising sea level must have inundated > 75% of the coastal plain land converting it into a veritable lagoon—lake system that eventually led to abrupt termination of the forest ecosystem and also converted the floodplains into peatland where accumulation of peat almost to 2.0–3.0 m thickness in coastal lowlands and river basins during the shorter interval in the Middle Holocene. Vast areas of the coastal plains of Kerala have been converted into carbon rich peatland during the Middle Holocene and transforming the entire coastal stretch and associated landforms as one of the relatively youngest peatlands in the extreme southern tip of India. Unlike the uninterrupted formation of peatlands of considerable extent during the Holocene in Southeast Asia, the south Peninsular Indian region has restricted and short intervals of peatlands in the floodplains and coastal lowlands. Such a scenario is attributed to the topographic relief of the terrain and the prevailing hydrological regimes and environmental conditions as a consequence of monsoon variability since Middle Holocene in SW India. Considering the tropical coastal lowlands and associated peatlands are excellent repositories of carbon, they are very important for regional carbon cycling and habitat diversity. The alarming rate of

  1. Tropical Peat and Peatland Development in the Floodplains of the Greater Pamba Basin, South-Western India during the Holocene.

    PubMed

    Kumaran, Navnith K P; Padmalal, Damodaran; Limaye, Ruta B; S, Vishnu Mohan; Jennerjahn, Tim; Gamre, Pradeep G

    2016-01-01

    Holocene sequences in the humid tropical region of Kerala, South-western (SW) India have preserved abundance of organic-rich sediments in the form of peat and its rapid development in a narrow time frame towards Middle Holocene has been found to be significant. The sub-coastal areas and flood plains of the Greater Pamba Basin have provided palaeorecords of peat indicating that the deposits are essentially formed within freshwater. The combination of factors like stabilized sea level and its subsequent fall since the Middle Holocene, topographic relief and climatic conditions led to rapid peat accumulation across the coastal lowlands. The high rainfall and massive floods coupled with a rising sea level must have inundated > 75% of the coastal plain land converting it into a veritable lagoon-lake system that eventually led to abrupt termination of the forest ecosystem and also converted the floodplains into peatland where accumulation of peat almost to 2.0-3.0 m thickness in coastal lowlands and river basins during the shorter interval in the Middle Holocene. Vast areas of the coastal plains of Kerala have been converted into carbon rich peatland during the Middle Holocene and transforming the entire coastal stretch and associated landforms as one of the relatively youngest peatlands in the extreme southern tip of India. Unlike the uninterrupted formation of peatlands of considerable extent during the Holocene in Southeast Asia, the south Peninsular Indian region has restricted and short intervals of peatlands in the floodplains and coastal lowlands. Such a scenario is attributed to the topographic relief of the terrain and the prevailing hydrological regimes and environmental conditions as a consequence of monsoon variability since Middle Holocene in SW India. Considering the tropical coastal lowlands and associated peatlands are excellent repositories of carbon, they are very important for regional carbon cycling and habitat diversity. The alarming rate of land

  2. Paleoshoreline record of relative Holocene sea levels on Pacific islands

    NASA Astrophysics Data System (ADS)

    Dickinson, William R.

    2001-11-01

    -oceanic island groups of both the northwestern and southwestern Pacific Ocean followed close on the heels of the mid-Holocene sea-level highstand, and took advantage of newly attractive coastal environments engendered by sea-level drawdown. The effects of the mid-Holocene highstand were modified to varying degrees in different island groups by geodynamic uplift or subsidence.

  3. Photo-Geomorphology of Coastal Landforms, Cat Island, Bahamas. Volume II,

    DTIC Science & Technology

    The report provides the aerial imagery used in the analysis of the coastal landforms of Cat Island in the east-central Bahama Islands. Interpretive...published volume Coastal Landform of Cat Island, Bahamas: A Study of Holocene Accretionary Topography and Sea-Level Change but may also serve as an

  4. Late Pleistocene-early Holocene karst features, Laguna Madre, south Texas: A record of climate change

    SciTech Connect

    Prouty, J.S.

    1996-09-01

    A Pleistocene coquina bordering Laguna Madre, south Texas, contains well-developed late Pleistocene-early Holocene karst features (solution pipes and caliche crusts) unknown elsewhere from coastal Texas. The coquina accumulated in a localized zone of converging longshore Gulf currents along a Gulf beach. The crusts yield {sup 14}C dates of 16,660 to 7630 B.P., with dates of individual crust horizons becoming younger upwards. The karst features provide evidence of regional late Pleistocene-early Holocene climate changes. Following the latest Wisconsinan lowstand 18,000 B.P. the regional climate was more humid and promoted karst weathering. Partial dissolution and reprecipitation of the coquina formed initial caliche crust horizons; the crust later thickened through accretion of additional carbonate laminae. With the commencement of the Holocene approximately 11,000 B.P. the regional climate became more arid. This inhibited karstification of the coquina, and caliche crust formation finally ceased about 7000 B.P.

  5. Holocene sea-level changes in the Falkland Islands

    NASA Astrophysics Data System (ADS)

    Newton, Tom; Gehrels, Roland; Daley, Tim; Long, Antony; Bentley, Mike

    2014-05-01

    In many locations in the southern hemisphere, relative sea level (RSL) reached its maximum position during the middle Holocene. This highstand is used by models of glacial isostatic adjustment (GIA) to constrain the melt histories of the large ice sheets, particularly Antarctica. In this paper we present the first Holocene sea-level record from the Falkland Islands (Islas Malvinas), an archipelago located on the Patagonian continental shelf about 500 km east of mainland South America at a latitude of ca. 52 degrees. Unlike coastal locations in southernmost South America, Holocene sea-level data from the Falklands are not influenced by tectonics, local ice loading effects and large tidal ranges such that GIA and ice-ocean mass flux are the dominant drivers of RSL change. Our study site is a salt marsh located in Swan Inlet in East Falkland, around 50 km southwest of Stanley. This is the largest and best developed salt marsh in the Falkland Islands. Cores were collected in 2005 and 2013. Lithostratigraphic analyses were complemented by analyses of foraminifera, testate amoebae and diatoms to infer palaeoenvironments. The bedrock, a Permian black shale, is overlain by grey-brown organic salt-marsh clay, up to 90 cm thick, which, in a landward direction, is replaced by freshwater organic sediments. Overlying these units are medium-coarse sands with occasional pebbles, up to 115 cm thick, containing tidal flat foraminifera. The sandy unit is erosively overlain by a grey-brown organic salt-marsh peat which extends up to the present surface. Further away from the sea this unit is predominantly of freshwater origin. Based on 13 radiocarbon dates we infer that prior to ~9.5 ka sea level was several metres below present. Under rising sea levels a salt marsh developed which was suddenly drowned around 8.4 ka, synchronous with a sea-level jump known from northern hemisphere locations. Following the drowning, RSL rose to its maximum position around 7 ka, less than 0.5 m above

  6. Coastal sedimentation

    NASA Technical Reports Server (NTRS)

    Schubel, J. R.

    1980-01-01

    Several important coastal sedimentation problems are identified. Application of existing or anticipated remote sensing techniques to examine these problems is considered. Specifically, coastal fine particle sediment systems, floods and hy hurricanes and sedimentation f of coastal systems, routes and rates of sediment transport on continental shelves, and dredging and dredged material disposal are discussed.

  7. Inception of a global atlas of Holocene sea levels

    NASA Astrophysics Data System (ADS)

    Khan, Nicole; Rovere, Alessio; Engelhart, Simon; Horton, Benjamin

    2017-04-01

    Determining the rates, mechanisms and geographic variability of sea-level change is a priority science question for the next decade of ocean research. To address these research priorities, the HOLocene SEA-level variability (HOLSEA) working group is developing the first standardized global synthesis of Holocene relative sea-level data to: (1) estimate the magnitudes and rates of global mean sea-level change during the Holocene; and (2) identify trends in spatial variability and decipher the processes responsible for geographic differences in relative sea-level change. Here we present the preliminary efforts of the working group to compile the database, which includes sea-level index points and limiting data from a range of different indicators across seven continents from the Last Glacial Maximum to present. We follow a standard protocol that incorporates full consideration of vertical and temporal uncertainty for each sea-level index point, including uncertainties associated with the relationship of each indicator to past sea-level and the methods used to date each indicator. We describe the composition of the global database, identify gaps in data availability, and highlight our effort to create an online platform to access the data. These data will be made available in a special issue of Quaternary Science Reviews and archived on NOAA's National Centers for Environmental Information (NCEI) in early 2018. We also invite researchers who collect or model Holocene sea-level data to participate. Long-term, this effort will enhance predictions of 21st century sea-level rise, and provide a vital contribution to the assessment of natural hazards with respect to sea-level rise and coastal response.

  8. Sedimentary proxy evidence of a mid-Holocene hypsithermal event in the location of a current warming hole, North Carolina, USA

    NASA Astrophysics Data System (ADS)

    Tanner, Benjamin R.; Lane, Chad S.; Martin, Elizabeth M.; Young, Robert; Collins, Beverly

    2015-03-01

    A wetland deposit from the southern Appalachian mountains of North Carolina, USA, has been radiocarbon dated and shows continuous deposition from the early Holocene to the present. Non-coastal records of Holocene paleoenvironments are rare from the southeastern USA. Increased stable carbon isotope ratios (δ13C) of sedimentary organic matter and pollen percentages indicate warm, dry early- to mid-Holocene conditions. This interpretation is also supported by n-alkane biomarker data and bulk sedimentary C/N ratios. These warm, dry conditions coincide with a mid-Holocene hypsithermal, or altithermal, documented elsewhere in North America. Our data indicate that the southeastern USA warmed concurrently with much of the rest of the continent during the mid-Holocene. If the current "warming hole" in the southeastern USA persists, during a time of greenhouse gas-induced warming elsewhere, it will be anomalous both in space and time.

  9. Reconstruction of Holocene Seismic Events Along Kamchatka's Pacific Coast

    NASA Astrophysics Data System (ADS)

    Pinegina, T.; Bourgeois, J.

    2004-12-01

    Since 1995 we have been conducting detailed neotectonic and paleoseismological field studies of the Holocene at more than 15 localities along the east coast of Kamchatka. Specific methods of these investigations include 1) application of tephra chronology and tephra stratigraphy for dating and correlation of various types of coastal deposits and landforms; 2) study of paleotsunami deposits in order to determine their ages and recurrence rate and to estimate the magnitude of large tsunamis and tsunamigenic earthquakes along the Kurile-Kamchatka subduction zone and north of the latter during Holocene time; 3) analysis of the geologic structure, age, and modern and paleo-topography of marine terraces and beach ridges in order to determine the direction and scale of seismotectonic movements over different time intervals; and 4) identification and dating of inferred seismogenic landslides along the coast. Eastern Kamchatka's short history (since about 1730 A.D.) includes many large and several great earthquakes, although historical coverage of these events is scarce because of both low population density, and also military secrecy. Nevertheless, we can use historical earthquakes and tsunami deposits as benchmarks for pre-historic events. Moreover, our studies have helped elucidate historic cases, including co-seismic deformation, tsunami runup, and tsunami source mechanism. As a result of these studies we have reconstructed key events in coastal evolution during the Holocene, and determined the ages of marine accumulative landforms on various segments of the coast. A combination of all our data enables us to get an idea about spatial and temporal distribution of strong subduction-type earthquakes along the Kuril-Kamchatka trench and 'non-subduction' earthquakes north of the trench terminus.

  10. Coastal Prairie

    USGS Publications Warehouse

    ,

    2000-01-01

    The coastal prairie, located along the coastal plain of southwestern Louisiana and southcentral Texas, is the southernmost tip of the tallgrass prairie ecosystem so prevalent in the Midwest. The coastal prairie ecosystem once covered as much as 3.8 million ha (9 million acres); today, more than 99% of this land has been lost to agriculture, range improvement, and urbanization. The remainder is highly fragmented and severely threatened by invasions of exotic species and urban sprawl. In Louisiana, the former 1 million ha of coastal prairie have now been reduced to about 100 ha. In Texas, only about 100,000 ha of coastal prairie remain intact.

  11. Global Change in the Holocene

    NASA Astrophysics Data System (ADS)

    Alverson, Keith

    2004-05-01

    Many people, even perhaps the occasional Eos reader, associate the term ``global change'' with warming caused by mankind's recent addiction to fossil fuels. Some may also be well aware of enormous global changes in the distant past uninfluenced by humans; for example, Pleistocene ice ages. But was there any ``global change'' between the end of the last ice age and the onset of industrialization? The answer to this question is addressed early-in the title, even-in the new book Global Change in the Holocene. I don't suggest anyone stop reading after the title, though; the rest of the book is both highly informative and a real pleasure to read. The opening chapter tells us that the Holocene is certainly not, as sometimes charged, a ``bland, pastoral coda to the contrasted movements of a stirring Pleistocene symphony.'' Rather, it is a ``period of continuous change.'' Melodious language aside, the combination of sustained and high-amplitude climatic variability and a wealth of well-preserved, precisely datable paleoclimate archives make the Holocene unique. Only by studying the Holocene can we hope to unravel the low-frequency workings of the Earth system and the degree to which humans have changed our world. This book sets out to teach the reader how to obtain the relevant data and how to use it to do much more than showing static analogues of possible future climate states. It challenges researchers to discern in their data the effects of the dynamic processes underlying coupled variability in the Earth's climate and ecosystems. These processes continue to act today, and it is through providing an understanding of these system dynamics in the Holocene that paleo-environmental studies can make the greatest contribution to future-oriented concerns.

  12. A Holocene Sediment Record From Lake Elsinore, Southern California: Evidence for Relative Lake Level Change and the Onset of ENSO.

    NASA Astrophysics Data System (ADS)

    Kirby, M. E.; Lund, S. P.; Poulsen, C. J.

    2003-12-01

    There are very few complete terrestrial, Holocene paleoclimate records from coastal southwestern North America. Lake Elsinore, located 120km southeast of Los Angeles, represents one of the only natural, non-playa lakes in the region. Furthermore, it is well documented that coastal southwestern North America is highly sensitive to changes in atmospheric circulation and its affect on regional hydrodynamics. As shown by Kirby et al. (in press), modern lake levels at Lake Elsinore respond directly to total annual precipitation, particularly winter season amounts. The lake is also located along the eastern Pacific Ocean where changes in ocean circulation and its thermal structure modulate the overlying atmosphere, and thus the adjacent continental climate. Here, we present two 7 meter sediment core records from Lake Elsinore spanning the entire Holocene. Although the cores are from the lake's littoral zone, they show surprisingly complete records with very little lithologic evidence for major hiatuses. A combination of sedimentological analyses (e.g., mass magnetic susceptibility (CHI); total percent carbonate; total organic matter) and lithologic descriptions provide insight to lake dynamics over the Holocene. Using the historical calibration between magnetic susceptibility and relative lake level (i.e., high lake levels = high CHI values and vice versa) from Kirby et al. (in press), we developed a first-order estimate of Holocene relative lake levels for Lake Elsinore. The historic calibration is extrapolated through the sediment record based on the assumption that, like today, first order lake level change is directly related to precipitation amount. Both total percent carbonate and total organic matter support our historical calibration between CHI and lake level. Our data suggest a relative increase in lake levels during the mid-Holocene (ca. 8,000 cal yr BP) and through to the present day. From this observation, we hypothesize that regional hydrology as linked to

  13. Latest Pleistocene and Holocene glaciation of Baffin Island, Arctic Canada: key patterns and chronologies

    NASA Astrophysics Data System (ADS)

    Briner, Jason P.; Davis, P. Thompson; Miller, Gifford H.

    2009-10-01

    Melting glaciers and ice caps on Baffin Island contribute roughly half of the sea-level rise from all ice in Arctic Canada, although they comprise only one-fourth of the total ice in the region. The uncertain future response of arctic glaciers and ice caps to climate change motivates the use of paleodata to evaluate the sensitivity of glaciers to past warm intervals and to constrain mechanisms that drive glacier change. We review the key patterns and chronologies of latest Pleistocene and Holocene glaciation on Baffin Island. The deglaciation by the Laurentide Ice Sheet occurred generally slowly and steadily throughout the Holocene to its present margin (Barnes Ice Cap) except for two periods of rapid retreat: An early interval ˜12 to 10 ka when outlet glaciers retreated rapidly through deep fiords and sounds, and a later interval ˜7 ka when ice over Foxe Basin collapsed. In coastal settings, alpine glaciers were smaller during the Younger Dryas period than during the Little Ice Age. At least some alpine glaciers apparently survived the early Holocene thermal maximum, which was several degrees warmer than today, although data on glacier extent during the early Holocene is extremely sparse. Following the early Holocene thermal maximum, glaciers advanced during Neoglaciation, beginning in some places as early as ˜6 ka, although most sites do not record near-Little Ice Age positions until ˜3.5 to 2.5 ka. Alpine glaciers reached their largest Holocene extents during the Little Ice Age, when temperatures were ˜1-1.5 °C cooler than during the late 20th century. Synchronous advances across Baffin Island throughout Neoglaciation indicate sub-Milankovitch controls on glaciation that could involve major volcanic eruptions and solar variability. Future work should further elucidate the state of glaciers and ice caps during the early Holocene thermal maximum and glacier response to climate forcing mechanisms.

  14. Holocene Tectonic and Sedimentary Evolution of Coastal San Diego

    NASA Astrophysics Data System (ADS)

    Maloney, J. M.; Driscoll, N. W.; Brothers, D. S.; Babcock, J. M.; Kent, G.

    2010-12-01

    The shelf and nearshore region of San Diego, California, between La Jolla cove in the north and the U.S.- Mexico border in the south, is an important ecological and economic resource. It contains two of the largest kelp forests in southern California and lies offshore miles of popular beaches. Understanding the interplay between tectonic and sedimentary processes in this area is critical because it will allow us to assess how other forcing functions such as the rapid sea level rise (2 - 3 mm/yr) and predicted climate change associated with global warming are impacting the kelp and nearshore environments. The fault architecture and sedimentary deposits offshore San Diego have been mapped using high-resolution seismic CHIRP profiling. The mapped area lies within the inner California Continental Borderland (CCB), which is characterized by a system of basins and ridges and extensive strike-slip faulting. The CHIRP data clearly images several splays of the Coronado Bank Fault Zone (CBFZ), a major fault in the area, which show recent activity in the upper 30 m of sediment with the most recent deformation at ~4 m below seafloor. Several sediment packages as deep as 50 m below the seafloor are imaged and place important constraints on tectonic deformation and sediment dispersal in the region as well as the earthquake recurrence interval on the CBFZ. Exposed and buried wavecut terraces identified on numerous CHIRP profiles, which can be correlated to terraces mapped regionally, provide insight into tectonic uplift rates and sea-level fluctuations. Finally, the extensive kelp forests offshore Mount Soledad and Point Loma occur where hardgrounds are exposed at the seafloor as a consequence of tectonic uplift. High resolution mapping offshore San Diego is providing new insight into the complex interplay between tectonics, sedimentation, and biology in this ecologically diverse region.

  15. Holocene paleoclimate inferred from salinity histories of adjacent lakes in southwestern Sicily (Italy)

    NASA Astrophysics Data System (ADS)

    Curry, Brandon; Henne, Paul D.; Mesquita-Joanes, Francesc; Marrone, Federico; Pieri, Valentina; La Mantia, Tommaso; Calò, Camilla; Tinner, Willy

    2016-10-01

    Marked uncertainties persist regarding the climatic evolution of the Mediterranean region during the Holocene. For instance, whether moisture availability gradually decreased, remained relatively constant, or increased during the last 7000 years remains a matter of debate. To assess Holocene limnology, hydrology and moisture dynamics, the coastal lakes Lago Preola and Gorgo Basso, located in southwestern Sicily, were investigated through several stratigraphic analyses of ostracodes, including multivariate analyses of assemblages, transfer functions of salinity, and biochemical analyses of valves (Sr/Ca, δ18O and δ13C). During the early Holocene, the Gorgo Basso and Lago Preola ostracode records are similar. After an initial period of moderate salinity (1690-6100 mg/l from ca. 10,000-8190 cal yr BP), syndepositional or diagenetic dissolution of ostracode valves suggests that salinity declined to <250 mg/L from ca. 8190 to 7000 cal yr BP at both sites. After ca. 6250 cal yr BP, the ostracode records are strikingly different. Lago Preola became much more saline, with paleosalinity values that ranged from 2270 to about 24,420 mg/L. We suggest that Lago Preola's change from a freshwater to mesosaline lake at about 6250 cal yr BP was related to sea level rise and resulting intrusion of seawater-influenced groundwater. In contrast, Gorgo Basso remained a freshwater lake. The salinity of Gorgo Basso declined somewhat after 6250 cal yr BP, in comparison to the early Holocene, ranging from about 550 to 1680 mg/L. Cypria ophtalmica, a species capable of rapid swimming and flourishing in waters with low dissolved oxygen levels, became dominant at approximately the time when Greek civilization took root in Sicily (2600 cal yr BP), and it completely dominates the record during Roman occupation (roughly 2100 to 1700 cal yr BP). These freshwater conditions at Gorgo Basso suggest high effective moisture when evergreen olive-oak forests collapsed in response to increased Greco

  16. Early to middle Holocene valley glaciations on northernmost Greenland

    NASA Astrophysics Data System (ADS)

    Möller, Per; Larsen, Nicolaj K.; Kjær, Kurt H.; Funder, Svend; Schomacker, Anders; Linge, Henriette; Fabel, Derek

    2010-12-01

    This paper presents the glacial stratigraphy and palaeoenvironmental evolution around Constable Bugt, Johannes V. Jensen Land, located on the north coast of Greenland. This is a land of extreme climate: polar desert conditions and a coast bound by a permanent sea ice cover. Our data covers the period from the Last Glacial Maximum (LGM, 18-22 cal ka BP) into the Holocene. It records the history of a shelf-based glaciation with ice flowing eastward along the coast as well as two local valley glacier advances from the south during the Holocene. With ice on the coastal plain during the LGM, glaciolacustrine basins formed in marginal positions and in ice-dammed valleys to the south into the mountainous area of Peary Land. With the break-up of shelf-based ice there was a gradual marine inundation at which the marine limit formed at ˜45 m a.s.l. This initial early Holocene ice advance from the south formed prominent valley mouth moraines, especially in Sifs valley. Here, both glaciolacustrine and marine sediments were remoulded and/or dislocated as thrust blocks into a moraine ridge spanning more than 1 km in width and >60 m in height. Radiocarbon ages of sediments incorporated in this moraine, as well as from on-lapping sediments, suggest that the moraine formed between 9.6 and 6.3 cal ka BP. Based on 14C dating results, the youngest ice advance phase can be narrowed down to 14C ages between ˜5.5-5.0 cal ka BP. The recorded ice advances took place during the Holocene Thermal Maximum (HTM) for North Greenland, the last one close to the beginning of the Neoglacial cooling. During the HTM we have recorded a period of ˜2500 years during which the north coast of Greenland - as opposed to today - experienced an absence to very restricted occurrence of land-fast or multi-year sea ice. This observation can be explained by the altitudinal and temporal distribution of beach-ridge complexes that must have formed by wave action and thus requiring at least partial open

  17. Holocene Lake Records on Kamchatka

    NASA Astrophysics Data System (ADS)

    Diekmann, Bernhard; Biskaborn, Boris; Chapligin, Bernhard; Dirksen, Oleg; Dirksen, Veronika; Hoff, Ulrike; Meyer, Hanno; Nazarova, Larisa

    2014-05-01

    The availibility of terrestrial records of Holocene palaeoenvironmental changes in eastern Siberia still is quite limited, compared to other regions on the northern hemisphere. In particular, the Kamchatka Peninsula as an important climate-sensitive region is very underrepresented. Situated at the border of northeastern Eurasia, the maritime-influenced terrestrial setting of Kamchatka offers the potential to pinpoint connections of environmental changes between the periglacial and highly continental landmasses of eastern Siberia and the sub-Arctic Pacific Ocean and Sea of Okhotsk. The study region lies at the eastern end-loop of the global thermohaline ocean conveyor belt and is strongly affected by atmospheric teleconnections. Volcanic, tectonic, and glacial processes overprint palaeoenvironmental changes in addition to primary climate forcing. In order to widen our understanding of plaeoclimate dynamics on Kamchatka, sediment cores from different lake systems and peat sections were recovered and analysed by a multi-proxy approach, using sedimentological and geochemical data as well as fossil bioindicators, such as diatoms, pollen, and chironomids. Chronostratigraphy of the studied records was achieved through radiocarbon dating and tephrostratigraphy. Sediment cores with complete Holocene sedimentary sequences were retrieved from Lake Sokoch, an up to six metre deep lake of proglacial origin, situated at the treeline in the Ganalsky Ridge of southern central Kamchatka (53°15,13'N, 157°45.49' E, 495 m a.s.l.). Lacustrine sediment records of mid- to late Holocene age were also recovered from the up to 30 m deep Two-Yurts Lake, which occupies a former proglacial basin at the eastern flank of the Central Kamchatka Mountain Chain, the Sredinny Ridge (56°49.6'N, 160°06.9'E, 275 m a.s.l.). In addition to sediment coring in the open and deep Two-Yurts Lake, sediment records were also recovered from peat sections and small isolated forest lakes to compare

  18. Holocene climate of New England

    NASA Astrophysics Data System (ADS)

    Davis, Margaret B.; Spear, Ray W.; Shane, Linda C. K.

    1980-09-01

    Stratigraphic studies of pollen and macrofossils from six sites at different elevations in the White Mountains of New Hampshire demonstrate changes in the distributions of four coniferous tree species during the Holocene. Two species presently confined to low elevations extended farther up the mountain slopes during the early Holocene: white pine grew 350 m above its present limit beginning 9000 yr B.P., while hemlock grew 300-400 m above its present limit soon after the species immigrated to the region 7000 yr. B.P. Hemlock disappeared from the highest sites about 5000 yr B.P., but both species persisted at sites 50-350 m above their present limits until the Little Ice Age began a few centuries ago. The history of the two main high-elevation conifers is more difficult to interpret. Spruce and fir first occur near their present upper limits 9000 or 10,000 yr B.P. Fir persisted in abundance at elevations similar to those where it occurs today throughout the Holocene, while spruce became infrequent at all elevations from the beginning of the Holocene until 2000 yr B.P. These facts suggest a more complex series of changes than a mere upward shift of the modern environmental gradient. Nevertheless, we conclude that the minimum climatic change which would explain the upward extensions of hemlock and white pine is a rise in temperature, perhaps as much as 2°C. The interval of maximum warmth started 9000 yr B.P. and lasted at least until 5000 yr B.P., correlative with the Prairie Period in Minnesota.

  19. Late Pleistocene and Holocene Fire History of the California Islands

    NASA Astrophysics Data System (ADS)

    Scott, A. C.; Hardiman, M.; Pinter, N.; Anderson, R.

    2013-12-01

    Charcoal has been recovered from a range of late Pleistocene and Holocene sites on Santa Cruz Island and Santa Rosa Island, both islands part of California's Northern Channel Islands, U.S.A. Sediments have been dated using radiocarbon measurements based on wood charcoal, fungal sclerotia, glassy carbon and fecal pellets and are given as calendar years BP. This charcoal has been used to interpret the fire history of the Islands. Charcoal assemblages from samples dating from 24,690 to 12,900 years are dominated by coniferous wood charcoal. Little angiosperm charcoal was recovered in any of the samples. Fungal sclerotia are frequent in a number of samples from a range of ages both on Santa Cruz and Santa Rosa. Fecal pellets are common in most samples and abundant in others. Some of the fecal pellets have hexagonal sides and are likely to represent termite frass. The sediments are fluvial in origin and the distribution of charcoal is irregular making interpretation of fire return intervals and fire frequency difficult. The charcoal indicates a significant record of fire before the earliest documented human arrival on the islands. Charcoal reflectance data shows the occurrence of predominantly low temperature charcoals suggesting common surface fires in the coniferous forest. Soledad Pond sediments from Santa Rosa Island (Anderson et al., 2010) dating from 11,800 cal years BP show a distinctively different vegetation dominated by angiosperms and showing a very different fire history. Pinus stands, coastal sage scrub dominated by Baccharis sp. and grassland replaced the conifer forest as the climate warmed. The early Holocene became increasingly drier, particularly after ca. 9150 cal yr BP. By ca. 6900 cal yr BP grasslands recovered. Introduction of non-native species by ranchers occurred subsequent to AD 1850. Charcoal influx is high early in the Soledad Pond record, but declines during the early Holocene when minimal biomass suggests extended drought. A general

  20. Recurrence of postseismic coastal uplift, Kuril subduction zone, Japan

    USGS Publications Warehouse

    Kelsey, H.; Satake, K.; Sawai, Y.; Sherrod, B.; Shimokawa, K.; Shishikura, M.

    2006-01-01

    Coastal stratigraphy of eastern Hokkaido indicates that decimeters of coastal uplitt occurred repeatedly m the late Holocene. Employing radiocarbon dating and tephrochronology, we identify along a 100 km length of the Kuril subduction zone six uplift events since ???2,800 years B.P. Uplift events occur at the same frequency as unusually high tsunamis. Each coastal uplift event, which occurs on average every 500 years, is the product of decade-long post seismic deep slip on the down dip extension of the seismogenic plate boundary following an offshore multi-segment earthquake that generates unusually high tsunamis. Copyright 2006 by the American Geophysical Union.

  1. Geologic records of Pleistocene, Holocene and Anthropocene beach profiles?

    NASA Astrophysics Data System (ADS)

    Dougherty, Amy; Choi, Jeong-Heon; Dosseto, Anthony

    2017-04-01

    The Anthropocene Working Group recently concluded that we have entered a new Epoch; starting during the last century when carbon dioxide, temperatures, and sea level all exceeding previous Holocene measurements. Climate change models predict a 1m rise in sea-level by 2100 coupled with increased storm intensity. Determining how vulnerable coasts will respond to global warming in the future, requires past records of sea-level and storm impacts to be deciphered. Paying specific attention to any changes prior to, and since, the onset of the Industrial Revolution. Coastal change over centennial time-scales has long fallen within a knowledge gap that exists between our understanding of shoreline behaviour measured over decades and that inferred from the landscape over millennia. Insight on shoreline behaviour across spatial and temporal scales is gained using computers to integrate models of short-term morphodynamics along beaches with longer-term coastal landscape evolution models. However, limitations exist as process-based engineering models depend on wave climate and beach profile data that is restricted to regional/historical records, while large-scale coastal behaviour models are based on general chronostratographic data from topographic profiles, interpolated cores, and isochrons extrapolated from deep radiocarbon ages. Here we demonstrate a unique methodology combining state-of-the-art geophysics, luminescence, and remote sensing techniques on prograded barriers to extract comprehensive chronostratigraphic records. Ground Penetrating Radar (GPR) data document beach and dune stratigraphy at decimetre resolution. Optically Stimulated Luminescence (OSL) directly date the formation of paleo-beachfaces and dunes. Light Detection and Ranging (LiDAR) image the lateral extent of strandplain ridge morphology. The resulting record of paleo-beach profiles spanning from the present-day beach through Holocene and Pleistocene barriers, enables our in-depth understanding of

  2. Mid-Holocene paleoceanographic conditions in the Limfjord region from gastropod (Littorina littorea) oxygen and carbon isotopes

    NASA Astrophysics Data System (ADS)

    Burman, J.; Schmitz, B.

    2003-04-01

    Stable oxygen and carbon isotope intrashell transects of common intertidal gastropods Littorina littorea have been used to reconstruct environmental conditions in the Limfjord region during the mid-Holocene (late Atlantic time). The subfossil specimens studied are from the excavated Stone Age Kitchenmidden in Ertebølle, northern Denmark, dated between 5970±95 to 5070±90 B.P. In addition recent specimens were studied from different coastal localities within the Limfjord, along a salinity gradient from the west to east. These modern shells were used as control samples, in order to construct an oceanographic model for the Limfjord, in which the seasonal isotopic range from the Littorina subfossils could be interpreted. The coastal marine climate in the Ertebølle region during the mid-Holocene indicates summer-SST close to 22^oC and 4-5 ppm reduced salinity compared to fully marine conditions. The mid-Holocene central Limfjord can be described as a coastal area, which experienced similar salinity conditions (c. 30.5 PSU) that prevail in the western part (Odden area) today. In terms of summer-SST as compared with a 10-year average (1989-1998) for the Limfjord region, temperatures were 2-3^oC above recent climatic settings. These results point towards a mid-Holocene Limfjord in contact with the North Sea/Skagerrak with possibly more pronounced water exchange with the North Sea than today.

  3. Holocene evolution of the western Orinoco Delta, Venezuela

    USGS Publications Warehouse

    Aslan, A.; White, W.A.; Warne, A.G.; Guevara, E.H.

    2003-01-01

    The pristine nature of the Orinoco Delta of eastern Venezuela provides unique opportunities to study the geologic processes and environments of a major tropical delta. Remote-sensing images, shallow cores, and radiocarbon-dating of organic remains form the basis for describing deltaic environments and interpreting the Holocene history of the delta. The Orinoco Delta can be subdivided into two major sectors. The southeast sector is dominated by the Rio Grande-the principal distributary-and complex networks of anastomosing fluvial and tidal channels. The abundance of siliciclastic deposits suggests that fluvial processes such as over-bank flooding strongly influence this part of the delta. In contrast, the northwest sector is represented by few major distributaries, and overbank sedimentation is less widespread relative to the southeast sector. Peat is abundant and occurs in herbaceous and forested swamps that are individually up to 200 km2 in area. Northwest-directed littoral currents transport large volumes of suspended sediment and produce prominent mudcapes along the northwest coast. Mapping of surface sediments, vegetation, and major landforms identified four principal geomorphic systems within the western delta plain: (1) distributary channels, (2) interdistributary flood basins, (3) fluvial-marine transitional environments, and (4) marine-influenced coastal environments. Coring and radiocarbon dating of deltaic deposits show that the northern delta shoreline has prograded 20-30 km during the late Holocene sea-level highstand. Progradation has been accomplished by a combination of distributary avulsion and mudcape progradation. This style of deltaic progradation differs markedly from other deltas such as the Mississippi where distributary avulsion leads to coastal land loss, rather than shoreline progradation. The key difference is that the Orinoco Delta coastal zone receives prodigious amounts of sediment from northwest-moving littoral currents that transport

  4. Holocene aridity and storm phases, Gulf and Atlantic coasts, USA

    NASA Astrophysics Data System (ADS)

    Otvos, Ervin G.

    2005-05-01

    A bottomland flora that prevailed between ˜9900 and 6000 cal yr B.P. in a North Carolina stream valley may not reflect a regionally much wetter Atlantic climate, coeval with record drought in the Great Plains region and assumed dry Gulf coastal conditions. Such conditions were inferred for 6000 ± 1000 yr ago when the Bermuda High may have consistently occupied summer positions far to the NE. Arid episodes coeval with the Little River local wet interval are known from eolian sediments and pollen spectra in the Atlantic and the Gulf coastal plain. For multiple reasons, the regional extent, intensity, and duration of coastal aridity and alternating wet phases and the Bermuda High positions are not yet adequately constrained. The climate and edaphic causes for the steadily growing predominance of southern pines over hardwoods, achieved between ˜8900 and 4200 cal yr B.P. at different sites at different times are similarly still unresolved. New data from Shelby Lake, AL, reconfirms that no credible field or other proxy evidence exists for a previously postulated "catastrophic Gulf hurricane phase" in the late Holocene.

  5. Enhanced Late Holocene ENSO/PDO expression along the margins of the eastern North Pacific

    USGS Publications Warehouse

    Barron, J.A.; Anderson, L.

    2011-01-01

    Pacific climate is known to have varied during the Holocene, but spatial patterns remain poorly defined. This paper compiles terrestrial and marine proxy data from sites along the northeastern Pacific margins and proposes that they indicate 1) suppressed ENSO conditions during the middle Holocene between ~8000 and 4000 cal BP with a North Pacific that generally resembled a La Ni??a-like or more negative PDO phase and 2) a climate transition between ~4200 and 3000 cal BP that appears to be the teleconnected expression to a more modern-like ENSO Pacific. Compared to modern day conditions, the compiled data suggest that during the middle Holocene, the Aleutian Low was generally weaker during the winter and/or located more to the west, while the North Pacific High was stronger during the summer and located more to the north. Coastal upwelling off California was more enhanced during the summer and fall but suppressed during the spring. Oregon and California sea surface temperatures (SSTs) were cooler. The Santa Barbara Basin had an anomalous record, suggesting warmer SSTs.Late Holocene records indicate a more variable, El Ni??o-like, and more positive PDO Pacific. The Aleutian Low became more intensified during the winter and/or located more to the east. The North Pacific High became weaker and/or displaced more to the south. Coastal upwelling off California intensified during the spring but decreased during the fall. Oregon and California SSTs became warmer, recording the shoreward migration of sub-tropical gyre waters during the fall, while spring upwelling (cooler SST) increased in the Santa Barbara Basin. The high-resolution proxy records indicate enhanced ENSO and PDO variability after ~4000 cal BP off southern California, ~3400 cal BP off northern California, and by ~2000 cal BP in southwestern Yukon. A progressively northward migration of the ENSO teleconnection during the late Holocene is proposed. ?? 2010.

  6. Paleolandscape Reconstruction of Holocene Fluvial Drainage, Narragansett Bay, Rhode Island.

    NASA Astrophysics Data System (ADS)

    Hearn, C. K.

    2016-12-01

    The Narragansett Bay System (NBS) located in eastern Rhode Island, United States, formed as a drowned river valley that began its most recent inundation at approximately the start of the Holocene Era. The earliest regional evidence for human occupation predates the inundation of the NBS, which would have existed as a network of streams and lakes. An abundance of artifacts recovered from the shoreline of the modern NBS provide a record of continuous habitation throughout the Holocene. A paleolandscape reconstruction of the lower NBS is in development to aid in assessing the archaeological sensitivity of the region regarding ancient Native American sites of cultural significance that are now submerged. The degree of potential preservation for such sites is closely linked to the extent of sediment removal during inundation, which is a function of the wave energy and rate of shoreface advancement. Accurate reconstructions of the paleolandscape are then critical for archaeological assessments. The West Passage (WP) of the NBS, the likely location for an early-Holocene freshwater lake, is bounded to the south by a large sill, which may have forced the basin to drain to the North before joining the East Passage drainage. The advancing shore may likewise have followed this northern route and gradually flooded the WP while maintaining a low-energy wave environment favorable to preservation until late in the inundation process. Dense sub-bottom sonar profiles were analyzed in the WP of the NBS in an attempt to locate paleochannels and test the theory of a northern fluvial drainage pathway prior to inundation. Evidence for the presence or absence of paleochannels through the sill would significantly affect the archaeological preservation potential for the WP. These results will be incorporated with a reconstruction for the entire lower bay and outer coastal shelf as part of large-scale novel effort to merge modern scientific investigations with Native American historical

  7. Review of the late-Holocene storm events along the European Atlantic coasts

    NASA Astrophysics Data System (ADS)

    Pouzet, Pierre; Maanan, Mohamed; Piotrowska, Natalia; Baltzer, Agnès; Stephan, Pierre

    2017-04-01

    The chronology of the mid- to late-Holocene coastal storms was reconstructed from vibracore samplings, 14C dating and sedimentary analysis from Yeu island (French Atlantic coast). The methodology used is based on the identification of disturbing sedimentary events recognized within three Holocene sedimentary transgressive sequences selected along the northern coast of the island. These sequences correspond to the present-day coastal salt-marshes and swamps. The sediment cores were centimeter-sampled and studied from several sedimentological proxies (Loss of Ignition, sand fraction, mean grain size) with a high temporal resolution. Chronology was built by age-depth model based on eleven 14C measures of organic sediments and shell samples. Ten paleo-storm events were recorded: a 2100-1950 calBP interval as a deeply stormy-disturbed period; five others major impacted times: 600-500 calBP, 2850-2350 calBP, 3500-3270 calBP, 5400-5370 calBP and 6650-6510 calBP; and four final less meaningful storminess hypothesis near 1590 calBP, 6000 calBP, 7000 calBP, and between 7670 and 7470 calBP. This chronology was compared with enhanced storminess periods recognized along the European Atlantic coast. Four stormy periods stand out from the last 4000 years: 600-300 BP, 1100-1700 BP, 2500-2900 BP and 3300-3500 BP, corresponding to late Holocene global cold events. These results suggests that these changes in coastal hydrodynamics were in phase with those identified over the North-eastern Atlantic and seem to correspond to Holocene cooling first shown in the North Atlantic and associated with decreases in sea surface temperature.

  8. A Holocene record of ocean productivity and upwelling from the northern California continental slope

    NASA Astrophysics Data System (ADS)

    Addison, J. A.; Barron, J. A.; Finney, B.; Kusler, J. E.; Bukry, D.; Heusser, L. E.; Alexander, C. R., Jr.

    2016-12-01

    The Holocene upwelling history of the northern California continental slope is examined using a 7-m-long marine sediment core (TN062-O550; 40.9°N, 124.6°W, 550 m water depth) collected offshore from Eureka, CA, that spans the last 7,400 calibrated years before present (cal yrs BP). A combination of biogenic sediment concentrations (opal, total organic C, and total N), stable isotopes (organic matter δ13C and bulk sedimentary δ15N), and key microfossil indicators of upwelling were used to test the hypothesis that marine productivity in the California Current System (CCS) driven by coastal upwelling has co-varied with global Holocene millennial-scale warm intervals. Results show biogenic sediment accumulation in TN062-O550 varied considerably during the Holocene, despite being located within 50 km of the mouth of the Eel River, one of the largest sources of terrigenous sediment to the Northeast Pacific Ocean margin. A key time interval beginning at 2900 cal yr BP indicates the onset of modern upwelling in the CCS, and that this period also corresponds to the most intense period of upwelling in the last 7,400 years. When these results are placed into a regional CCS context during the Holocene, it was found that the timing of upwelling intensification as recorded in TN062-O550 corresponds closely to that seen at nearby ODP Site 1019 as well as in the Santa Barbara Basin of southern California. Other CCS records with less high-quality age control show similar results, which suggest late Holocene upwelling intensification may be synchronous throughout the CCS. Based on the strong correspondence between the alkenone-derived sea surface temperature record at ODP Site 1019 and the onset of late Holocene upwelling in northern California, we tentatively suggest that regional CCS warming may be conducive to upwelling intensification in the future.

  9. Holocene fire dynamics in Fennoscandia

    NASA Astrophysics Data System (ADS)

    Clear, Jennifer; Seppa, Heikki; Kuosmanen, Niina; Molinari, Chiara; Lehsten, Veiko; Allen, Katherine; Bradshaw, Richard

    2015-04-01

    Prescribed burning is advocated in Fennoscandia to promote regeneration and to encourage biodiversity. This method of forest management is based on the perception that fire was much more frequent in the recent past and over a century of active fire suppression has created a boreal forest ecosystem almost free of natural fire. The absence of fire is thought to have contributed to the widespread dominance of Picea abies (Norway spruce) with the successive spruce dominated forest further reducing fire ignition potential. However, humans have altered the natural fire dynamics of Fennoscandia since the early- to mid-Holocene and disentangling the anthropogenic driven fire dynamics from the natural fire dynamics is challenging. Through palaeoecology and sedimentary charcoal deposits we are able to explore the Holocene spatial and temporal variability and changing drivers of fire and vegetation dynamics in Fennoscandia. At the local-scale, two forest hollow environments (<20km apart) were analysed for high resolution macroscopic charcoal and pollen analysis and their fire and vegetation history are compared to identify unique and mutual changes in disturbance history. Pollen derived quantitative reconstruction of vegetation at both the local- and regional-scale identifies local-scale disturbance dynamics and large-scale ecosystem response. Spatio-temporal heterogeneity and variability in biomass burning is explored throughout Fennoscandia and Denmark to identify the changing drives of fire dynamics throughout the Holocene. Palaeo-vegetation reconstructions are compared to process-based, climate driven dynamic vegetation model output to test the significance of fire frequency as a driver of vegetation composition and dynamics. Early-Holocene fire regimes in Fennoscandia are driven by natural climate variations and fuel availability. The establishment and spread of Norway spruce is driven by an increase in continentality of climate, but local natural and anthropogenic

  10. The fluvial evolution of the Holocene Nile Delta

    NASA Astrophysics Data System (ADS)

    Pennington, B. T.; Sturt, F.; Wilson, P.; Rowland, J.; Brown, A. G.

    2017-08-01

    The evolution of the Nile Delta, the largest delta system in the Mediterranean Sea, has both high palaeoenvironmental and archaeological significance. A dynamic model of the landscape evolution of this delta system is presented for the period c.8000-4500 cal BP. Analysis of sedimentary data and chronostratigraphic information contained within 1640 borehole records has allowed for a redefinition of the internal stratigraphy of the Holocene delta, and the construction of a four-dimensional landscape model for the delta's evolution through time. The mid-Holocene environmental evolution is characterised by a transition from an earlier set of spatially varied landscapes dominated by swampy marshland, to better-drained, more uniform floodplain environments. Archaeologically important Pleistocene inliers in the form of sandy hills protruding above the delta plain surface (known as ;turtlebacks;), also became smaller as the delta plain continued to aggrade, while the shoreline and coastal zone prograded north. These changes were forced by a decrease in the rate of relative sea-level rise under high rates of sediment-supply. This dynamic environmental evolution needs to be integrated within any discussion of the contemporary developments in the social sphere, which culminated in the emergence of the Ancient Egyptian State c.5050 cal BP.

  11. Diagenetic dolomite formation in a Holocene evaporitic lake

    SciTech Connect

    Coshell, L.; Scott, J. ); Rosen, M.; Turner, J.V. )

    1991-03-01

    Holocene dolomite forms in the sediment of Lake Hayward, a small, permanent, hypersaline lake in the Clifton-Preston Lakeland System, Western Australia. The Clifton-Preston Lakeland System is similar in climate, geography, and sedimentology to the Coorong Region of South Australia. However, dolomite in Lake Hayward is not a primary precipitate as in the Coorong but is of diagenetic origin. The diagenetic origin can be deduced from the combination of the following criteria: (1) the dolomite occurs only between 60-70 cm from the sediment water interface; (2) dolomite occurs as luminescing cement; and (3) dolomite has pristine well-formed rhomb-shaped crystals. The source of magnesium for dolomitization is probably from the concentration of inflowing groundwater by evaporation and the selective removal of calcium by aragonite/calcite precipitation. Although the mechanisms of dolomite formation in Lake Hayward are slightly different than in the Coorong, the presence of Holocene dolomite in an almost identical setting illustrates the importance of the 'Coorong model' for dolomite formation in modern coastal areas.

  12. Western equatorial African forest-savanna mosaics: a legacy of late Holocene climatic change?

    NASA Astrophysics Data System (ADS)

    Ngomanda, A.; Chepstow-Lusty, A.; Makaya, M.; Favier, C.; Schevin, P.; Maley, J.; Fontugne, M.; Oslisly, R.; Jolly, D.

    2009-02-01

    Past vegetation and climate changes reconstructed using two pollen records from Lakes Maridor and Nguène, Gabon, provide new insights into the environmental history of western equatorial African rainforests during the last 4500 cal yr BP. The Lake Maridor pollen record indicates that the coastal savannas of western equatorial Africa did not exist during the mid-Holocene and instead the region was covered by evergreen rainforests. In the Lake Nguène pollen record, a rapid decline of hygrophilous evergreen rainforest occurred around 4000 cal yr BP, synchronously with grassland expansion around Lake Maridor. The establishment of coastal savannas in Gabon suggests decreasing humidity at the onset of the late Holocene. The marked reduction in evergreen rainforest and subsequent savanna expansion was associated with the colonization of secondary forests dominated by the palm, Elaeis guineensis, in the coastal region and the shrub, Alchornea cordifolia, further inland. A return to wetter climatic conditions from about 1400 cal yr BP led to the renewed spread of evergreen rainforest inland, whereas a forest-savanna mosaic still persists in the coastal region. There is no evidence to suggest that the major environmental changes observed are driven by human impact.

  13. Holocene paleoenviroments of northwest Iowa

    SciTech Connect

    Baker, R.G.; Bettis, E.A. III; Schwert, D.P.

    1996-05-01

    This paper presents the biotic, sedimentary, geomorphic, and climatic history of the upper part of the Roberts Creek Basin, northeastern Iowa for the late-glacial and Holocene, and compares these records with a C-O isotopic sequence from Coldwater Cave, 60 km northwest of Roberts Creek. the biotic record (pollen, vascular plant and bryophyte macrofossils, and insects) is preserved in floodplain alluvium that underlies three constructional surfaces separated by low scarps. Each surface is underlain by a lithologically and temporally distinct alluvial fill. The highest surface is underlain by the Gunder Member of the Deforest Formation, dating from 11,000 to 4000 yr BP; beneath the intermediate level is the Roberts Creek Member, dating from 4000 to 400 yr BP; and the lowest level is underlain by the Camp Creek Member, deposited during the last 380 yr. Pollen and plant macrofossils in the alluvial fill show that a typical late-glacial spruce forest was replaced by Quercus and Ulmus in the early Holocene. This early-to-middle Holocene forest became dominated by medic elements such as Acer saccharum, Tila americana, Ostyra virginiana, and Carpinus caroliniana as late as 5500 yr BP; in contrast, the closest sites to the west and north were at their warmest and driest were covered by prairie vegetation between 6500 and 5500 yr BP. After 5500 yr BP, the forest in the roberts Creek area was replaced by prairie, as indicated by a rich assemblage of plant macrofossils, although only Ambrosia and Poaceae became abundant in the pollen record. The return of Quercus {approx} 3000 BP (while nonarboreal pollen percentages remained relatively high) indicates the oak savanna prevailed with little change until settlement time. 83 refs., 17 figs., 5 tabs.

  14. Coastal wetlands

    SciTech Connect

    Prince, H.H.; d'Itri, F.M.

    1986-01-01

    This book presents an overview of coastal wetlands, mainly focusing on the Great Lakes ecosystem. Topics covered include the following: the effects of water level fluctuations on Great Lakes coastal marshes; environmental influences on the distribution and composition of wetlands in the Great Lakes Basin; vegetation dynamics, buried seeds, and water level fluctuations on the shorelines of the Great Lakes; preliminary observations on the flux of carbon, nitrogen, and phosphorous in a Great Lakes coastal marsh; nutrient cycling by wetlands and possible effects of water levels; and Avain wetland habitat functions affected by water level fluctuations.

  15. A model for the Holocene extinction of the mammal megafauna in Ecuador

    NASA Astrophysics Data System (ADS)

    Ficcarelli, G.; Coltorti, M.; Moreno-Espinosa, M.; Pieruccini, P. L.; Rook, L.; Torre, D.

    2003-03-01

    This paper presents the results of multidisciplinary research in the Ecuadorian coastal regions, with particular emphasis on the Santa Elena Peninsula. The new evidence, together with previous data gathered on the Ecuadorian cordillera during the last 12 years, allows us to formulate a model that accounts for most of the mammal megafauna extinction at the Pleistocene/Holocene transition. After the illustration of geomorphological and paleontological evidences of the area of the Santa Elena Peninsula (and other sites), and of a summary of the paleoclimatic data, the main results and conclusions of this work are: (1) Late Pleistocene mammal assemblages survived in the Ecuadorian coast until the Early Holocene sea level rise; (2) Prior to the extinction of most of the megafauna elements (mastodons, ground sloths, equids, sabre-tooth felids), the mammal communities at Santa Elena Peninsula comprise elements with differing habitat requirements, attesting conditions of high biological pressure; (3) At the El Cautivo site (Santa Elena Peninsula), we have discovered Holocene sediments containing the first known occurrences in Ecuador of lithic artifacts that are associated with mammal megafauna remains; (4) During the last 10,000 years, the coastal region of Ecuador underwent significant changes in vegetation cover. At the Pleistocene/Holocene transition the climate changed from very arid conditions to humid conditions. Our data indicates that the megafauna definitively abandoned the Cordillera areas around 12,000 yr BP due to t he increasing aridity, and subsequently migrated to coastal areas where ecological conditions still were suitable, Santa Elena Peninsula and mainly Amazonian areas being typical. We conclude that the unusual high faunal concentrations and the change to dense vegetation cover (due to a rapid increase in precipitation in the lower Holocene) at 8000-6000 yr BP, caused the final collapse and extinction of most elements of the mammal megafauna

  16. The geological framework of coastal land loss in Louisiana

    SciTech Connect

    Penland, S. ); Roberts, H.H. ); Williams, S.J. )

    1990-09-01

    The Mississippi River delta and chenier plains in Louisiana are experiencing catastrophic coastal land loss rates exceeding 100 km{sup 2}/ yr. Louisiana's coastal zone contains 40% of the US wetlands and 80% of the nation's loss occurs here. The origin and stability of these coastal environments are tied to the sediments discharged by the Mississippi River through the delta cycle process. Sediments accumulate in well-defined delta complexes at approximately 800-1,000 year intervals followed by abandonment and barrier island formation. The delta-cycle process, which builds new deltas and barrier islands, has been stopped by flood control structures. These harness the flow of the Mississippi River within a massive levee system, channeling most of the sediments off of the continental shelf. Deprived of sediments and subsiding rapidly, Louisiana's wetlands are disintegrating and the shoreline is eroding. Subsidence is a key critical process driving the submergence of Louisiana's sediment-starved coastal zone. The thickness of the Holocene sequence controls the subsidence rate. Where the Holocene delta plain sequence is greater than 50 m, the submergence rates are 1- 1.25 cm/yr and the land loss rates are 80 km{sup 2}/yr. In contrast, where the Holocene chenier plain thickness is less than 15 m, the submergence rates are 0.4-0.6 cm/yr, and the land loss rate is 10 km{sup 2}/yr.

  17. Coastal Center

    NASA Astrophysics Data System (ADS)

    The U.S. Geological Survey dedicated its new Center for Coastal Geology June 12 at the University of South Florida in St. Petersburg. Robert Halley leads the staff of nine USGS scientists studying coastal erosion and pollution and underwater mineral resources in cooperation with the university's Marine Science Department. Current research is on erosion along Lake Michigan and the Gulf Coast of Louisiana. The number of USGS scientists at the center should increase to 30 over five years.

  18. Holocene geoarchaeology of the Sixteen Mile Beach barrier dunes in the Western Cape, South Africa

    NASA Astrophysics Data System (ADS)

    Compton, John S.; Franceschini, Giuliana

    2005-01-01

    Holocene evolution and human occupation of the Sixteen Mile Beach barrier dunes on the southwest coast of South Africa between Yzerfontein and Saldanha Bay are inferred from the radiocarbon ages of calcareous dune sand, limpet shell ( Patella spp.) manuports and gull-dropped white mussel shells ( Donax serra). A series of coast-parallel dunes have prograded seaward in response to an overall marine regression since the mid-Holocene with dated shell from relict foredunes indicating periods of shoreline progradation that correspond to drops in sea level at around 5900, 4500 and 2400 calibrated years before the present (cal yr B.P.). However, the active foredune, extensively covered by a layer of gull-dropped shell, has migrated 500 m inland by the recycling of eroded dune sand in response to an approximate 1 m sea level rise over the last 700 yr. Manuported limpet shells from relict blowouts on landward vegetated dunes indicate human occupation of coastal dune sites at 6200 and 6000 cal yr B.P. and help to fill the mid-Holocene gap in the regional archaeological record. Coastal midden shells associated with small hearth sites exposed in blowouts on the active foredune are contemporaneous (1600-500 cal yr B.P.) with large midden sites on the western margin of Langebaan Lagoon and suggest an increase in marine resource utilisation associated with the arrival of pastoralism in the Western Cape.

  19. Using Holocene relative sea-level data to inform future sea-level predictions: An example from southwest England

    NASA Astrophysics Data System (ADS)

    Gehrels, W. Roland; Dawson, David A.; Shaw, Jon; Marshall, William A.

    2011-08-01

    Holocene relative sea-level data contain information on vertical land movements along coasts and, hence, can provide vital input for predictions of future sea-level change. At Thurlestone, in southwest England, late Holocene coastal sediments were cored and sampled in coastal back-barrier marshes. The presence of a basal sedimentary unit containing salt-marsh microfossils made it possible to obtain precise estimates of late Holocene relative sea-level change from the sediments. This is important because previous studies have suggested that the southwest of England is experiencing the fastest rates of land subsidence in the British Isles. Ten new late Holocene basal sea-level index points fill an important gap in the palaeosea-level data set for southwest England. Another 15 early and middle Holocene sea-level index points are available from previous work. The data show that relative sea level rose by about 10 m between 9000 and 7000 cal. yr BP and a further 8 m in the last 7000 yr. In the last 2000 yr, relative sea level rose on average by 0.9 mm/yr. The coast is currently subsiding by 1.1 mm/yr due to ongoing glacial isostatic adjustment (GIA). The Bradley et al. (2009) GIA model, which is used in the United Kingdom to determine land-motion rates for input into future sea-level predictions, underestimates the rate of coastal subsidence by about 0.16 mm/yr, but performs better than other models. Our data validate the land-motion rates currently used in regional sea-level projections.

  20. Holocene paleoenvironments of Northeast Iowa

    USGS Publications Warehouse

    Baker, R.G.; Bettis, E. Arthur; Schwert, D.R.; Horton, D.G.; Chumbley, C.A.; Gonzalez, Luis A.; Reagan, M.K.

    1996-01-01

    This paper presents the biotic. sedimentary, geomorphic, and climatic history of the upper part of the Roberts Creek Basin, northeastern Iowa for the late-glacial and Holocene, and compares these records with a C-O isotopic sequence from Coldwater Cave. 60 km northwest of Roberts Creek. The biotic record (pollen, vascular plant and bryophyle macrofossils. and insects) is preserved in floodplain alluvium that underlies three constructional surfaces separated by low scarps. Each surface is underlain by a lithologically and temporally distinct alluvial fill. The highest surface is underlain by the Gunder Member of the Deforest Formation, dating from 11 000 to 4000 yr BP; beneath the intermediate level is the Roberts Creek Member, dating from 4000 to 400 yr BP; and the lowest level is underlain by the Camp Creek Member, deposited during the last 380 yr. Pollen and plant macrofossils in the alluvial fill show that a typical late-glacial spruce forest was replaced by Quercus and Ulmus in the early Holocene. This early-to-middle Holocene forest became dominated by mesic elements such as Acer saccharum, Tilia americana, Ostrya virginiana, and Carpinus caroliniana as late as 5500 yr BP; in contrast, the closest sites to the west and north were at their warmest and driest and were covered by prairie vegetation between 6500 and 5500 yr BP. After 5500 yr BP, the forest in the Roberts Creek area was replaced by prairie, as indicated by a rich assemblage of plant macrofossils, although only Ambrosia and Poaceae became abundant in the pollen record. The return of Quercus ??? 3000 BP (while nonarboreal pollen percentages remained relatively high) indicates that oak savanna prevailed with little change until settlement time. The bryophyte assemblages strongly support the vascular plant record. Rich fen species characteristic of boreal habitats occur only in the late-glacial. They are replaced by a number of deciduous-forest elements when early-to-middle Holocene forests were

  1. Holocene loess and paleosols in central Alaska: A proxy record of Holocene climate change

    SciTech Connect

    Bigelow, N.H.; Beget, J.E.

    1992-03-01

    Episodic Holocene loess deposition and soil formation in the sediments of the Nenana valley of Central Alaska may reflect Holocene climate change. Periods of loess deposition seem to correlate with times of alpine glacier activity, while paleosols correspond to times of glacial retreat These variations may reflect changes in solar activity Stuiver and Braziunas, 1989. Other mechanisms, such as orbitally forced changes in seasonality, volcanism, and atmospheric C02 variability may also have affected Holocene climates and loess deposition.

  2. The Holocene Isolation of Dalma Island

    NASA Astrophysics Data System (ADS)

    Lokier, Stephen

    2010-05-01

    Dalma Island can be broadly defined as an emergent salt diapir formed through the halokinetic emplacement of the Precambrian-Cambrian Hormuz Complex. The outline of the island, as seen today, has been much modified by anthropogenic dredge-and-fill activities. The lithofacies of Dalma Island can be subdivided into three distinct geological and geographical provinces. The core of the island is dominated by the sedimentary, evaporitic and volcanic lithologies of the Hormuz Complex. These chaotically distributed units are unconformably overlain by sediments and evaporites of the Miocene Fars Formation. The island's coastline is dominated by Recent bioclastic sediments, primarily derived from reefs at the island's northern coast. Following exposure of the Arabian Gulf floor during the Last Glacial Maximum, marine waters entered the Strait of Hormuz in the latest Pleistocene and the Gulf once again became a shallow epicontinental seaway. Bathymetric surveys reveal that the sea floor surrounding Dalma Island and separating it from the mainland lies at a depth shallower than 40 m. The Holocene transgression would not have had any effect on this area until after 10.2 Ka. After this time, rising ground water levels, associated with the advancing shoreline, may have resulted in the localised formation of shallow lakes or marshes in depressions. As sea level continued to rise, these lakes coalesced and the Dalma Salt Dome became increasingly isolated from the mainland. Once the transgression had reached the -15 m contour, by 8.5 Ka, Dalma would have been completely isolated from the mainland. By 6 ka sea level had reached present levels with continued rise eventually peaking between 1-2 m higher than today. At this time the area of the island would have been much reduced with wide areas of the island's low-lying coastal plain being either submerged or lying in the intertidal environment. The above figures for the isolation of Dalma make two assumptions. Firstly, it is

  3. Enhanced Late Holocene ENSO/PDO expression along the margins of the eastern North Pacific

    USGS Publications Warehouse

    Barron, John A.; Anderson, Lesleigh

    2011-01-01

    Late Holocene records indicate a more variable, El Niño-like, and more positive PDO Pacific. The Aleutian Low became more intensified during the winter and/or located more to the east. The North Pacific High became weaker and/or displaced more to the south. Coastal upwelling off California intensified during the spring but decreased during the fall. Oregon and California SSTs became warmer, recording the shoreward migration of sub-tropical gyre waters during the fall, while spring upwelling (cooler SST) increased in the Santa Barbara Basin. The high-resolution proxy records indicate enhanced ENSO and PDO variability after ∼4000 cal BP off southern California, ∼3400 cal BP off northern California, and by ∼2000 cal BP in southwestern Yukon. A progressively northward migration of the ENSO teleconnection during the late Holocene is proposed.

  4. Holocene history of ENSO variance and asymmetry in the eastern tropical Pacific.

    PubMed

    Carré, Matthieu; Sachs, Julian P; Purca, Sara; Schauer, Andrew J; Braconnot, Pascale; Falcón, Rommel Angeles; Julien, Michèle; Lavallée, Danièle

    2014-08-29

    Understanding the response of the El Niño-Southern Oscillation (ENSO) to global warming requires quantitative data on ENSO under different climate regimes. Here, we present a reconstruction of ENSO in the eastern tropical Pacific spanning the past 10,000 years derived from oxygen isotopes in fossil mollusk shells from Peru. We found that ENSO variance was close to the modern level in the early Holocene and severely damped ~4000 to 5000 years ago. In addition, ENSO variability was skewed toward cold events along coastal Peru 6700 to 7500 years ago owing to a shift of warm anomalies toward the Central Pacific. The modern ENSO regime was established ~3000 to 4500 years ago. We conclude that ENSO was sensitive to changes in climate boundary conditions during the Holocene, including but not limited to insolation.

  5. Multiple thermal maxima during the Holocene

    SciTech Connect

    Davis, O.K.

    1984-08-10

    The astronomical theory of climatic change provides an alternative to the traditional chronology for Holocene climatic change, which calls for one thermal maximum about 6000 years ago. The theory predicts a series of maxima during the Holocene, one for each season. Because the relation of the perihelion to the spring equinox changes with a 22,000-year period, late summer insolation would have been greatest 5000 years ago, whereas early summer insolation would have been greatest 13,000 years ago. Climatic reconstructions based on the response of ecosystems to late summer climate indicate a later Holocene thermal maximum than paleoclimatic data sensitive to early summer climate. In southern Idaho, three different vegetation types indicate thermal maxima at different times during the Holocene, depending on the climatic variable controlling each type. 28 references, 2 figures.

  6. Faunal histories from Holocene ancient DNA.

    PubMed

    de Bruyn, Mark; Hoelzel, A Rus; Carvalho, Gary R; Hofreiter, Michael

    2011-08-01

    Recent studies using ancient DNA have been instrumental in advancing understanding of the impact of Holocene climate change on biodiversity. Ancient DNA has been used to track demography, migration and diversity, and is providing new insights into the long-term dynamics of species and population distributions. The Holocene is key to understanding how the past has impacted on the present, as it bridges the gap between contemporary phylogeographic studies and those with inference on Pleistocene patterns, based on ancient DNA studies. Here, we examine the major patterns of Holocene faunal population dynamics and connectivity; highlighting the dynamic nature of species and population responses to Holocene climatic change, thereby providing an 'analogue' for understanding potential impacts of future change.

  7. Middle Holocene thermal maximum in eastern Beringia

    NASA Astrophysics Data System (ADS)

    Kaufman, D. S.; Bartlein, P. J.

    2015-12-01

    A new systematic review of diverse Holocene paleoenvironmental records (Kaufman et al., Quat. Sci. Rev., in revision) has clarified the primary multi-centennial- to millennial-scale trends across eastern Beringia (Alaska, westernmost Canada and adjacent seas). Composite time series from midges, pollen, and biogeochemical indicators are compared with new summaries of mountain-glacier and lake-level fluctuations, terrestrial water-isotope records, sea-ice and sea-surface-temperature analyses, and peatland and thaw-lake initiation frequencies. The paleo observations are also compared with recently published simulations (Bartlein et al., Clim. Past Discuss., 2015) that used a regional climate model to simulate the effects of global and regional-scale forcings at 11 and 6 ka. During the early Holocene (11.5-8 ka), rather than a prominent thermal maximum as suggested previously, the newly compiled paleo evidence (mostly sensitive to summer conditions) indicates that temperatures were highly variable, at times both higher and lower than present, although the overall lowest average temperatures occurred during the earliest Holocene. During the middle Holocene (8-4 ka), glaciers retreated as the regional average temperature increased to a maximum between 7 and 5 ka, as reflected in most proxy types. The paleo evidence for low and variable temperatures during the early Holocene contrasts with more uniformly high temperatures during the middle Holocene and agrees with the climate simulations, which show that temperature in eastern Beringia was on average lower at 11 ka and higher at 6 ka than at present (pre-industrial). Low temperatures during the early Holocene can be attributed in part to the summer chilling caused by flooding the continental shelves, whereas the mid-Holocene thermal maximum was likely driven by the loss of the Laurentide ice sheet, rise in greenhouse gases, higher-than-present summer insolation, and expansion of forest over tundra.

  8. Methane turnover and environmental change from Holocene biomarker records in a thermokarst lake in Arctic Alaska

    USGS Publications Warehouse

    Elvert, Marcus; Pohlman, John; Becker, Kevin W.; Gaglioti, Benjamin V.; Hinrichs, Kai-Uwe; Wooller, Matthew J.

    2016-01-01

    Arctic lakes and wetlands contribute a substantial amount of methane to the contemporary atmosphere, yet profound knowledge gaps remain regarding the intensity and climatic control of past methane emissions from this source. In this study, we reconstruct methane turnover and environmental conditions, including estimates of mean annual and summer temperature, from a thermokarst lake (Lake Qalluuraq) on the Arctic Coastal Plain of northern Alaska for the Holocene by using source-specific lipid biomarkers preserved in a radiocarbon-dated sediment core. Our results document a more prominent role for methane in the carbon cycle when the lake basin was an emergent fen habitat between ~12,300 and ~10,000 cal yr BP, a time period closely coinciding with the Holocene Thermal Maximum (HTM) in North Alaska. Enhanced methane turnover was stimulated by relatively warm temperatures, increased moisture, nutrient supply, and primary productivity. After ~10,000 cal yr BP, a thermokarst lake with abundant submerged mosses evolved, and through the mid-Holocene temperatures were approximately 3°C cooler. Under these conditions, organic matter decomposition was attenuated, which facilitated the accumulation of submerged mosses within a shallower Lake Qalluuraq. Reduced methane assimilation into biomass during the mid-Holocene suggests that thermokarst lakes are carbon sinks during cold periods. In the late-Holocene from ~2700 cal yr BP to the most recent time, however, temperatures and carbon deposition rose and methane oxidation intensified, indicating that more rapid organic matter decomposition and enhanced methane production could amplify climate feedback via potential methane emissions in the future.

  9. Relationship between species diversity and reef growth in the Holocene at Ishigaki Island, Pacific Ocean

    NASA Astrophysics Data System (ADS)

    Hongo, Chuki; Kayanne, Hajime

    2010-01-01

    Coral reefs are influenced by global and local factors, and living corals are currently faced with a potential loss of species diversity. Knowledge of the relationship between species diversity and reef growth during the Holocene is important in terms of accurately reconstructing natural conditions prior to recent disturbances (e.g., human impact, pollution, and over-harvesting) and in predicting future scenarios (e.g., abrupt sea-level rise, coastal change, and economic services). This study seeks to characterize the Holocene and present-day reef at Ishigaki Island in the Ryukyu Islands, focusing on spatial and temporal variations in the relationship between species diversity and reef growth. The analysis is based on a drilling core obtained for the Holocene reefs and quantitative species-diversity data (Shannon and Weaver's diversity index, H') obtained for the present-day reef. H' was calculated for four coral communities surveyed at the Ibaruma and Fukido reefs. The Holocene sequence was dominated by the corymbose coral community (e.g., Acropora digitifera, A. hyacinthus, Goniastrea retiformis, and Platygyra ryukyuensis), yielding an H' value of 1.6. The encrusting coral community (e.g., Echinopora lamellose and Pachyseris rugosa) showed the highest diversity at the reef ( H' = 2.2); however, this community was not one of the main reef builders during the Holocene. The massive coral community (e.g., Porites lutea and Favites chinensis) showed the lowest diversity ( H' = 0.6). It also made a minor contribution to reef building; this community appeared in a shallow lagoon once sea level had stabilized. The arborescent coral community (e.g., A. formosa and A. nobilis) was one of the main reef builders, although yielding an H' value of much less than 1.0. Species diversity is not a prerequisite in terms of Holocene reef growth. Thus, a few species (e.g., A. digitifera, A. hyacinthus, A. formosa, A. nobilis, G. retiformis, and P. ryukyuensis) from two main reef

  10. Holocene elephant seal distribution implies warmer-than-present climate in the Ross Sea.

    PubMed

    Hall, B L; Hoelzel, A R; Baroni, C; Denton, G H; Le Boeuf, B J; Overturf, B; Töpf, A L

    2006-07-05

    We show that southern elephant seal (Mirounga leonina) colonies existed proximate to the Ross Ice Shelf during the Holocene, well south of their core sub-Antarctic breeding and molting grounds. We propose that this was due to warming (including a previously unrecognized period from approximately 1,100 to 2,300 (14)C yr B.P.) that decreased coastal sea ice and allowed penetration of warmer-than-present climate conditions into the Ross Embayment. If, as proposed in the literature, the ice shelf survived this period, it would have been exposed to environments substantially warmer than present.

  11. Carbon sequestration in Southeast Asian tropical peatlands over the Holocene period: large-scale hydrological controls

    NASA Astrophysics Data System (ADS)

    Dommain, R.; Couwenberg, J.; Cobb, A.; Gandois, L.; Kai, F.; Su'ut, N.; Abu Salim, K.; Harvey, C. F.; Glaser, P. H.; Joosten, H.

    2012-12-01

    Tropical peatlands are recognized as a significant sink of carbon dioxide and an important source of methane. Low latitude peatlands contain an estimated pool of 90 Pg C, of which ca. 70 Pg C is stored in Southeast Asian peatlands. However, the Holocene development of this carbon reservoir is poorly established. Here we provide a synthesis of carbon uptake rates by tropical peatlands in Southeast Asia across millennial timescales for the past 11,000 years. Our reconstruction of the carbon accumulation history for Borneo, Sumatra and Peninsular Malaysia is based on a synthesis of radiocarbon dated peat profiles, modeling of peatland extent, and a new carbon accumulation record from Brunei (NW-Borneo). During the early Holocene the first peatlands formed in southern Borneo under the influence of a strong monsoon and rapid rise in sea-level. The carbon accumulation rate (CAR) in these peatlands was on average 60 g C m-2 yr-1 at this time. Peatlands started to spread across the coastal lowlands of Borneo, Sumatra and Peninsular Malaysia after 8000 cal BP only when the rate of rising sea-level decreased. The major phase of coastal peatland initiation lasted from 7000 to 4000 cal BP. This period was marked by a Holocene precipitation maximum, suppressed El Niño activity, and the Holocene maximum in sea-level on the Sunda Shelf. The mean CAR of coastal peatlands at this time was 80 g C m-2 yr-1, with a Holocene peak of ~100 g C m-2 yr-1 from 4900 to 4500 cal BP. Significantly, atmospheric CO2 concentrations measured in the Taylor Dome Antarctic ice core indicate a plateau during this period of otherwise rising CO2 concentrations. During the Late Holocene CAR declined both in coastal peatlands (ca. 70 g C m-2 yr-1) and in southern Borneo (ca. 20 g C m-2 yr-1) in response to falling sea-levels and increased El Niño frequency and intensity. In fact, several peatlands in southern Borneo have stopped accumulating peat-carbon under higher El Niño activity. These results

  12. Holocene glacial fluctuations in southern South America

    NASA Astrophysics Data System (ADS)

    Reynhout, S.; Sagredo, E. A.; Kaplan, M. R.; Aravena, J. C.; Martini, M. A.; Strelin, J. A.; Schaefer, J. M.

    2016-12-01

    Understanding the timing and magnitude of former glacier fluctuations is critical to decipher long-term climatic trends and to unravel both natural cycles and human impact on the current glacial behavior. Despite more than seven decades of research efforts, a unifying model of Holocene glacial fluctuations in Southern South America remains elusive. Here, we present the state-of-the-art regarding the timing of Holocene glacial fluctuation in southern Patagonia-Tierra del Fuego, with a focus on a new generation of high-resolution radiocarbon and 10Be surface exposure dating chronologies. Recently acquired evidence suggest that after receding from advanced Late Glacial positions, Patagonian glaciers were for the most part close to, or even behind, present ice margins during the Early Holocene. On the other hand, emerging chronologies indicate that in some areas there were extensive expansions (century scale?) that punctuated the warm interval. Subsequently, we have evidence of multiple millennial timescale glacial advances starting in the middle Holocene. Several glacial maxima are defined by moraines and other landforms from 7000 years ago to the 19th century, with a gap sometime between 4,500 and 2,500 years ago. The last set of advances began around 800-600 years ago. Although glacial activity is documented in Patagonia at the same time as the European Little Ice Age, the extent of these glacial events are less prominent than those of the mid-Holocene. The causes that may explain these glacial fluctuations remain elusive. Finally, we discuss ongoing efforts to better define the timing and extent of Holocene glaciations in southern South America, and to establish the basis to test competing hypothesis of regional Holocene climate variability.

  13. Onshore-offshore coastal lithofacies of Polis basin, NW Cyprus

    SciTech Connect

    Ward, L.C. )

    1988-08-01

    The Polis basin, northwest Cyprus, is located between the Akamas Peninsula and the main Troodos ophiolite massif. The basin contains sediments of Miocene-Holocene age and allows detailed study of a range of onshore-offshore coastal lithofacies which represent potential reservoirs. Coastal sediments of Messinian age characterized by algal mats and fluvial channel fill are found in the basin. Following very late Miocene rifting and Pliocene transgression, steep, narrow, faulted coastlines were produced, and several coastal facies were generated. These include coastal alluvial fans, offshore reefs, and tectonically generated cliff deposits as olistolith blocks. The steep, faulted coastline generated fan-delta deposits in early Pliocene time, superseded during late Pliocene regression by carbonate fan deltas. Offshore coastal lithofacies include storm-generated deposits, consisting of rip-up clasts and hummocky cross-stratification in sand-silt sequences, and mass-flow and channelized conglomerates and debris flows in this tectonically active basin. Shoreline sands are dominated by long-shore drift which generated longitudinal sandbars and offshore gravel bars. Pleistocene-age deposits show several suites of coastal deposits, formed in response to oscillations in Pleistocene sea level. These include beach deposits demonstrating beach-crest and planar bimodal back-beach deposits, together with coastal lagoons transected by cross-bedded fluvial conglomerate deposits. In addition, lowstands produced large channelized braided fluvial deposits which formed part of a broad coastal plain. Certain Pleistocene channels are deformed by continuing synsedimentary tectonic activity.

  14. Pleistocene and Holocene Iberian flora: a complete picture and review

    NASA Astrophysics Data System (ADS)

    González Sampériz, Penélope

    2010-05-01

    A detailed analysis of the location and composition of Iberian vegetation types during the whole Pleistocene and Holocene periods shows a complex patched landscape with persistence of different types of ecosystems, even during glacial times. In addition, recent, high-resolution palaeoecological records are changing the traditional picture of post-glacial vegetation succession in the Iberian Peninsula. The main available charcoal and pollen sequences include, coniferous and deciduous forest, steppes, shrublands, savannahs and glacial refugia during the Pleistocene for Meso-thermophytes (phytodiversity reservoirs), in different proportions. This panorama suggests an environmental complexity that relates biotic responses to climate changes forced by Milankovitch cycles, suborbital forcings and by the latitudinal and physiographic particularities of the Iberian Peninsula. Thus, many factors are critical in the course of vegetational developments and strong regional differences are observed since the Early Pleistocene. Currently, the flora of Iberia is located in two biogeographical/climatic regions: the Eurosiberian and the Mediterranean. The first one includes northern and northwestern areas of the peninsula, where post-glacial responses of vegetation are very similar to Central Europe, although with some particularities due to its proximity to both the Atlantic Ocean and the Mediterranean region. The second one comprises the main territory of Iberia and shows more complex patterns and singularities, now and in the past. Steppe landscapes dominated extensive areas over all the territory during the cold spells of the Quaternary, especially during the Late Pleistocene up to the Last Glacial Maximum, but differences in composition of the dominant taxa (Compositae versus Artemisia) are observed since the Early Pleistocene, probably related to moisture regional gradients. Coastal shelves and intramountainous valleys, even in continental areas, are spots of floristic

  15. Climate and vegetation change during the Holocene in southern Iberia

    NASA Astrophysics Data System (ADS)

    Jiménez Moreno, Gonzalo; Anderson, R. Scott; Ramos-Roman, María J.; Camuera, Jon; Garcia-Alix, Antonio; Jimenez-Espejo, FranciscoJ.; Toney, Jaime L.; Mesa-Fernandez, Jose Manuel; Manzano, Saul; Carrion, Jose S.

    2017-04-01

    Detailed pollen analysis has been carried out on several sediment cores taken from high-elevation alpine lakes and bog areas located in Sierra Nevada and coastal and offshore environments from southern Spain. The early Holocene is characterized in these records by the highest abundance of arboreal pollen, indicating the warmest and wettest conditions in the area at that time. The pollen records show a progressive aridification trend since the beginning of the middle Holocene through a decrease in forest species and the increase in xerophytes. The progressive aridification is punctuated by millennial-scale periodically enhanced droughts that coincide in timing and duration with well-known arid events in the Mediterranean and other areas. A relatively humid period occurred during the Iberian-Roman Humid Period. The Medieval Climate Anomaly (900-1300 AD) was characterized by a wet phase at first, coinciding with a solar minimum, and a later arid phase, coinciding with the Medieval solar Maximum and a positive NAO. The Little Ice Age (1300-1850 AD) was markedly wetter than earlier, as shown by the increase in tree pollen, coinciding with a phase of negative NAO and the Maunder solar minimum. This study shows that vegetation and climate in the Western Mediterranean are modulated by solar and atmospheric factors. Out-of-trend vegetation changes are observed in the last centuries, which probably indicate the high-impact of humans in the Sierra Nevada, with pasturing leading to nutrient enrichment and eutrophication of the wetlands, Olea cultivation at lower elevations and Pinus reforestation.

  16. Composition, age and habitat conditions of the meso-holocene malacofauna of the boisman 2 neolithic site in the maritime territory

    SciTech Connect

    Jull, A.J.T.; Kuz`min, Ya.V.; Lutaenko, K.A.; Orlova, L.A.; Popov, A.N.; Rakov, V.A.; Sulerzhitskii, L.D.

    1994-11-01

    A study of the coastal malocofauna of the climatically optimal Holocene of the Maritime territory is important for understanding the formation of the malocofauna of the region and for predicting the possible consequences of a global warming trend and an increase in the ocean level in the 21st century. The authors studied the paleontological material in the lower layer of Boisman 2 site from the first meso-Holocen `shell pile` in Russia`s far east region. Contemporary beach thanotocenoses of shore molluscs and a collection of molluscs from Boisman Bay were studied for comparison. 7 refs., 2 figs., 1 tab.

  17. Early Holocene Great Salt Lake

    USGS Publications Warehouse

    Oviatt, Charles G.; Madsen, David B.; Miller, David; Thompson, Robert S.; McGeehin, John P.

    2015-01-01

    Shorelines and surficial deposits (including buried forest-floor mats and organic-rich wetland sediments) show that Great Salt Lake did not rise higher than modern lake levels during the earliest Holocene (11.5–10.2 cal ka BP; 10–9 14C ka BP). During that period, finely laminated, organic-rich muds (sapropel) containing brine-shrimp cysts and pellets and interbedded sodium-sulfate salts were deposited on the lake floor. Sapropel deposition was probably caused by stratification of the water column — a freshwater cap possibly was formed by groundwater, which had been stored in upland aquifers during the immediately preceding late-Pleistocene deep-lake cycle (Lake Bonneville), and was actively discharging on the basin floor. A climate characterized by low precipitation and runoff, combined with local areas of groundwater discharge in piedmont settings, could explain the apparent conflict between evidence for a shallow lake (a dry climate) and previously published interpretations for a moist climate in the Great Salt Lake basin of the eastern Great Basin.

  18. Western equatorial African forest-savanna mosaics: a legacy of late Holocene climatic change?

    NASA Astrophysics Data System (ADS)

    Ngomanda, A.; Chepstow-Lusty, A.; Makaya, M.; Favier, C.; Schevin, P.; Maley, J.; Fontugne, M.; Oslisly, R.; Jolly, D.

    2009-10-01

    Past vegetation and climate changes reconstructed using two pollen records from Lakes Maridor and Nguène, located in the coastal savannas and inland rainforest of Gabon, respectively, provide new insights into the environmental history of western equatorial African rainforests during the last 4500 cal yr BP. These pollen records indicate that the coastal savannas of western equatorial Africa did not exist during the mid-Holocene and instead the region was covered by evergreen rainforests. From ca. 4000 cal yr BP a progressive decline of inland evergreen rainforest, accompanied by the expansion of semi-deciduous rainforest, occurred synchronously with grassland colonisation in the coastal region of Gabon. The contraction of moist evergreen rainforest and the establishment of coastal savannas in Gabon suggest decreasing humidity from ca. 4000 cal yr BP. The marked reduction in evergreen rainforest and subsequent savanna expansion was followed from 2700 cal yr BP by the colonization of secondary forests dominated by the palm, Elaeis guineensis, and the shrub, Alchornea cordifolia (Euphorbiaceae). A return to wetter climatic conditions from about 1400 cal yr BP led to the renewed spread of evergreen rainforest inland, whereas a forest-savanna mosaic still persists in the coastal region. There is no evidence to suggest that the major environmental changes observed were driven by human impact.

  19. Holocene thinning of the Greenland ice sheet.

    PubMed

    Vinther, B M; Buchardt, S L; Clausen, H B; Dahl-Jensen, D; Johnsen, S J; Fisher, D A; Koerner, R M; Raynaud, D; Lipenkov, V; Andersen, K K; Blunier, T; Rasmussen, S O; Steffensen, J P; Svensson, A M

    2009-09-17

    On entering an era of global warming, the stability of the Greenland ice sheet (GIS) is an important concern, especially in the light of new evidence of rapidly changing flow and melt conditions at the GIS margins. Studying the response of the GIS to past climatic change may help to advance our understanding of GIS dynamics. The previous interpretation of evidence from stable isotopes (delta(18)O) in water from GIS ice cores was that Holocene climate variability on the GIS differed spatially and that a consistent Holocene climate optimum-the unusually warm period from about 9,000 to 6,000 years ago found in many northern-latitude palaeoclimate records-did not exist. Here we extract both the Greenland Holocene temperature history and the evolution of GIS surface elevation at four GIS locations. We achieve this by comparing delta(18)O from GIS ice cores with delta(18)O from ice cores from small marginal icecaps. Contrary to the earlier interpretation of delta(18)O evidence from ice cores, our new temperature history reveals a pronounced Holocene climatic optimum in Greenland coinciding with maximum thinning near the GIS margins. Our delta(18)O-based results are corroborated by the air content of ice cores, a proxy for surface elevation. State-of-the-art ice sheet models are generally found to be underestimating the extent and changes in GIS elevation and area; our findings may help to improve the ability of models to reproduce the GIS response to Holocene climate.

  20. Tracking Nile Delta vulnerability to Holocene change.

    PubMed

    Marriner, Nick; Flaux, Clément; Morhange, Christophe; Stanley, Jean-Daniel

    2013-01-01

    Understanding deltaic resilience in the face of Holocene climate change and human impacts is an important challenge for the earth sciences in characterizing the full range of present and future wetland responses to global warming. Here, we report an 8000-year mass balance record from the Nile Delta to reconstruct when and how this sedimentary basin has responded to past hydrological shifts. In a global Holocene context, the long-term decrease in Nile Delta accretion rates is consistent with insolation-driven changes in the 'monsoon pacemaker', attested throughout the mid-latitude tropics. Following the early to mid-Holocene growth of the Nile's deltaic plain, sediment losses and pronounced erosion are first recorded after ~4000 years ago, the corollaries of falling sediment supply and an intensification of anthropogenic impacts from the Pharaonic period onwards. Against the backcloth of the Saharan 'depeopling', reduced river flow underpinned by a weakening of monsoonal precipitation appears to have been particularly conducive to the expansion of human activities on the delta by exposing productive floodplain lands for occupation and irrigation agriculture. The reconstruction suggests that the Nile Delta has a particularly long history of vulnerability to extreme events (e.g. floods and storms) and sea-level rise, although the present sediment-starved system does not have a direct Holocene analogue. This study highlights the importance of the world's deltas as sensitive archives to investigate Holocene geosystem responses to climate change, risks and hazards, and societal interaction.

  1. Holocene climate less stable than previously thought

    NASA Astrophysics Data System (ADS)

    deMenocal, Peter; Bond, Gerard

    Until recently, Holocene climate was thought to be extremely stable with none of the abrupt variations that characterize the cold climates of glacial times [Dansgaard et al., 1993]. New terrestrial, marine, and ice core data, however, document abrupt changes during the warm interglacial climate of the last 12,000 years. These newly developed Holocene paleoclimate records indicate that the Holocene was punctuated by a series of millennial-scale (1000-2000 year) cooling events, the most recent of which was the Little Ice Age (LIA) between approximately 1500 and 1800 A.D. Historical evidence indicates that the estimated ˜1°-2°C LIA ooling was ufficient to choke European ports with sea ice, freeze European rivers (as graphically recorded in the 1565 painting “Winter Landscape” by Pieter Bruegel), force abandonment of Viking colonies in Greenland, and cause glaciers to overrun alpine villages [Bradley and Jones, 1995]. Although these Holocene cooling events were not as large as the well-known glacial Heinrich events and Dansgaard-Oeschger climate instabilities [Bond et al., 1996; Dansgaard et al., 1993], they nonetheless document dramatic climate swings during the “climatically stable” Holocene.

  2. Coastal Navigation Portfolio Management

    DTIC Science & Technology

    2015-02-19

    CIRP.aspx Coastal Inlets Research Program Coastal Navigation Portfolio Management The Coastal Navigatoin Portfolio Management work unit...across the vast coastal navigation portfolio of projects. The USACE maintains a vast infrastructure portfolio of deep-draft coastal entrance...the Corps needs to be able to direct resources at the navigation projects that are most critical to overall marine transportation system performance

  3. Holocene sedimentation processes and environmental changes along the Namibian coastline

    NASA Astrophysics Data System (ADS)

    Schüller, Irka; Belz, Lukas; Wilkes, Heinz; Wehrmann, Achim

    2016-04-01

    The regional oceanic and atmospheric circulation patterns strongly control environmental conditions in southern Africa. Changes in the system may have significant consequences on climate and related processes. The hyper arid coast of Namibia is mainly influenced by (1) the cold Benguela upwelling, (2) the Benguela current and (3) the Angola current. The Benguela current transports the cool, upwelling water from south to north and interacts with the warm, contrary flowing Angola current at the Angola-Benguela Front (ABF). Today the ABF is located around the Namibian-Angolan border with minor seasonal changes. Therefore, climate and environment at the Namibian coast are affected by the cold water conditions. It is known evidently that the location of the ABF changed during the Holocene over several latitudes and enabled warm water species to expand their range farther south. Several (paleo-) lagoons (coastal salt pans) exist along the Namibian coastline. Most of them are already barred and filled by longshore sediment transport processes. Tidal flooding and active sedimentation processes are restricted to the southernmost lagoons. Two different types of sediments occur. The northern pans contain well sorted, siliciclastic medium sands. Fine-layered alternation refers to changes in mineral composition. The southern pans are dominated by typical tidal sediments with a high amount of benthic fauna (mainly bivalves and gastropods). At Cape Cross the distinct shift between both facies is documented in the cores. Age determinations of core material prove a very fast sediment filling of the distinct lagoons with high sedimentation rates. However, the age of closure differs from lagoon to lagoon. Northern pan sediments are much older (Cape Cross: ~ 5000 a BP) than southern (Sandwich Bay and Conception Bay: 1800 - 300 a BP). Additional information are supported by river clay deposits (~ 36600 a BP) and fossil reed systems (~ 47900 a BP) in Conception Bay and peat deposits at

  4. Distribution of albatross remains in the Far East regions during the Holocene, based on zooarchaeological remains.

    PubMed

    Eda, Masaki; Higuchi, Hiroyoshi

    2004-07-01

    Many albatross remains have been found in the Japanese Islands and the surrounding areas, such as Sakhalin and South Korea. These remains are interesting for two reasons: numerous sites from which albatross remains have been found are located in coastal regions of the Far East where no albatrosses have been distributed recently, and there are some sites in which albatross remains represent a large portion of avian remains, although albatrosses are not easily preyed upon by human beings. We collected data on albatross remains from archaeological sites in the Far East regions during the Holocene and arranged the remains geographically, temporally and in terms of quantity. Based on these results, we showed that coastal areas along the Seas of Okhotsk and Japan have rarely been used by albatrosses in Modern times, though formerly there were many albatrosses. We proposed two explanations for the shrinkage of their distributional range: excessive hunting in the breeding areas, and distributional changes of prey for albatrosses.

  5. Holocene paleoclimate inferred from salinity histories of adjacent lakes in southwestern Sicily (Italy)

    USGS Publications Warehouse

    Curry, B Brandon; Henne, Paul; Mezquita-Joanes, Francesc; Marrone, Federico; Pieri, Valentina; La Mantia, Tommaso; Calo, Camilla; Tinner, Willy

    2016-01-01

    Marked uncertainties persist regarding the climatic evolution of the Mediterranean region during the Holocene. For instance, whether moisture availability gradually decreased, remained relatively constant, or increased during the last 7000 years remains a matter of debate. To assess Holocene limnology, hydrology and moisture dynamics, the coastal lakes Lago Preola and Gorgo Basso, located in southwestern Sicily, were investigated through several stratigraphic analyses of ostracodes, including multivariate analyses of assemblages, transfer functions of salinity, and biochemical analyses of valves (Sr/Ca, δ18O and δ13C). During the early Holocene, the Gorgo Basso and Lago Preola ostracode records are similar. After an initial period of moderate salinity (1690–6100 mg/l from ca. 10,000–8190 cal yr BP), syndepositional or diagenetic dissolution of ostracode valves suggests that salinity declined to <250 mg/L from ca. 8190 to 7000 cal yr BP at both sites. After ca. 6250 cal yr BP, the ostracode records are strikingly different. Lago Preola became much more saline, with paleosalinity values that ranged from 2270 to about 24,420 mg/L. We suggest that Lago Preola's change from a freshwater to mesosaline lake at about 6250 cal yr BP was related to sea level rise and resulting intrusion of seawater-influenced groundwater. In contrast, Gorgo Basso remained a freshwater lake. The salinity of Gorgo Basso declined somewhat after 6250 cal yr BP, in comparison to the early Holocene, ranging from about 550 to 1680 mg/L. Cypria ophtalmica, a species capable of rapid swimming and flourishing in waters with low dissolved oxygen levels, became dominant at approximately the time when Greek civilization took root in Sicily (2600 cal yr BP), and it completely dominates the record during Roman occupation (roughly 2100 to 1700 cal yr BP). These freshwater conditions at Gorgo Basso suggest high effective moisture when evergreen olive-oak forests collapsed in response

  6. El Nino influence on Holocene reef accretion in Hawai'i

    USGS Publications Warehouse

    Rooney, J.; Fletcher, C.; Grossman, E.; Engels, M.; Field, M.

    2004-01-01

    New observations of reef accretion from several locations show that in Hawai'i accretion during early to middle Holocene time occurred in areas where today it is precluded by the wave regime, suggesting an increase in wave energy. Accretion of coral and coralline algae reefs in the Hawaiian Islands today is largely controlled by wave energy. Many coastal areas in the main Hawaiian Islands are periodically exposed to large waves, in particular from North Pacific swell and hurricanes. These are of sufficient intensity to prevent modern net accretion as evidenced by the antecedent nature of the seafloor. Only in areas sheltered from intense wave energy is active accretion observed. Analysis of reef cores reveals patterns of rapid early Holocene accretion in several locations that terminated by middle Holocene time, ca. 5000 yr ago. Previous analyses have suggested that changes in Holocene accretion were a result of reef growth "catching up" to sea level. New data and interpretations indicate that the end of reef accretion in the middle Holocene may be influenced by factors in addition to sea level. Reef accretion histories from the islands of Kaua'i, O'ahu, and Moloka'i may be interpreted to suggest that a change in wave energy contributed to the reduction or termination of Holocene accretion by 5000 yr ago in some areas. In these cases, the decrease in reef accretion occurred before the best estimates of the decrease in relative sea-level rise during the mid-Holocene high stand of sea level in the main Hawaiian Islands. However, reef accretion should decrease following the termination of relative sea-level rise (ca. 3000 yr ago) if reef growth were "catching up" to sea level. Evidence indicates that rapid accretion occurred at these sites in early Holocene time and that no permanent accretion is occurring at these sites today. This pattern persists despite the availability of hard substrate suitable for colonization at a wide range of depths between -30 m and the

  7. Carbonate-evaporite cycles in the Miocene to Holocene of Abu Dhabi, United Arab Emirates

    SciTech Connect

    Whittle, G.L.; Alsharhan, A.S.; Takezaki, H.

    1995-08-01

    The coastal sabkhas of the United Arab Emirates provide a Holocene analog for the study of evaporite formation. Carbonate-evaporite sequences are common throughout geologic history and, in the Arabian Gulf region in particular, create the reservoir-seal relationship of some of the most prolific hydrocarbon reservoirs in the world. Detailed core description, thin section study and geochemical analysis of Miocene to Holocene cores from the sabkha of Abu Dhabi have been performed in order to characterize modern sabkha diagenetic patterns. Two primary lithologies, dolomite and anhydrite were identified and subdivided into lithofacies. Based on these lithofacies, deposition is interpreted to have occurred in shallow open marine, lagoonal, tidal channel, tidal/algal flats and supratidal sabkha settings. The primary diagenetic effects are dolomitization, anhydritc formation and leaching. As anhydrite precipitated (in the form of gypsum), the Mg:Ca ratio increased to the point where rapid dolomitization of original limestone occurred. Leaching was pervasive, as subaerial exposure led to the formation of moldic porosity in dolomitized packstones and grainstones. Dolomitic cements in these pores, and leached zones in some of these crystals suggests that leaching continued after dolomitization. By comparing the Holocene sabkha sediments to ancient ones, insight may be gained into the extent of dolomilization both with depth and distance for in the high water mark, the zonation of the stratigraphy from upper supratidal to shallow shelf, the preservation potential of algal mats after burial, the compaction effects after shallow burial, and other diagenetic alterations.

  8. Salinity and hydrodynamics of the Holocene and upper Pleistocene beneath the Louisiana wetlands from electrical measurements

    SciTech Connect

    McGinnis, L.D.; Thompson, M.D.; Kuecher, G.J.; Wilkey, P.L.; Isaacson, H.R.

    1995-06-01

    A conceptual hydrodynamic model in the Holocene and upper Pleistocene beneath the Louisiana wetlands is described in terms of safety distributions. Porewater safety is calculated from electrical measurements, including resistivity soundings, electric logs, and electromagnetic profiling. Electrical measurements support the primary, basin-wide groundwater flow model; however, the data also indicate secondary contributions from expulsion of fluids under geopressure along active growth faults and from original waters of deposition. Expulsion of water from growth faults has been described previously for deeper sections of the Pleistocene, but has not been reported for the Holocene or upper Pleistocene beneath the Louisiana wetlands. Porewater chemistry variations beneath the coastal wetlands are a consequence of the following (in order of importance): (1) environment of deposition; (2) a basin-wide, regional flow system; (3) expulsion from deep-seated growth faults; and (4) pore water extrusion due to compaction. Water chemistry in Holocene clays and muds is influenced primarily by the deposition environment In Pleistocene sands, the chemistry is a function of the other three factors.

  9. Holocene relative sea level rise and subsidence in northern Gulf of Mexico

    SciTech Connect

    Penland, S.; Sutter, J.R.; Ramsey, K.E.; McBride, R.D.

    1988-01-01

    The analysis of more than 90 tidal gauge records, 10,000-km high resolution seismic profiles, 500 vibracores, and 250 radiocarbon dates led to the development of a new sea level history for the Louisiana coastal zone and adjacent continental shelf for the last 8,000 years. Now reinterpreted, the original single delta plain is seen as actually two individual, imbricated shelf-phase delta plains deposited at different sea levels. Termed the modern and late Holocene, these two delta plains are separated by a regional shoreface refinement surface, which can be traced updip to the relict-transgressive Teche shoreline. The Late Holocene delta plain was deposited during a sea level stillstand 6 m below the present, 3,000-7,2000 years ago. A 5 to 6-m eustatic-enhanced relative rise in sea level, 2,5000-3,000 years ago at a rate of 1-1.2 cm/yr led to the complete transgresive submergence of the lower late Holocene delta plain. Sea level reached its approximate position about 2,500 years ago, and since then the Mississippi River has built the modern delta plain consisting of the abandoned St. Bernard and Lafourche delta complexes and the active Balize and Atchafalaya delta complexes.

  10. Holocene depositional history of a large glaciated estuary, Penobscot Bay, Maine

    SciTech Connect

    Knebel, H.J.

    1985-01-01

    Data from seismic-reflection profiles, sidescan-sonar images, and sediment samples reveal the Holocene depositional history of the large (1100 km/sup 2/) Penobscot Bay estuary of coastal Maine. Isostatic recovery of the crust caused the bay to emerge during the immediate postglacial period, and relative sea level stood at about -40 m sometime between 9000 and 11,000 years ago. During the postglacial low stand, the ancestral Penobscot River flowed across the subaerially exposed head of the bay and debouched into Middle Passage. Organic-matter-rich silty clays form the river were deposited in the glacially eroded lower reaches of Middle and West Passages behind a shallow bedrock sill at the mouth of the bay. East Passage was isolated from the rest of the system and received only small amounts of locally derived sediment. During the ensuing Holocene transgression, the locus of sedimentation shifted to the head of the bay. Here, fluvial sediments filled the ancestral channels of the Penobscot River as base level rose, and the migrating surf zone created a gently dipping erosional unconformity, marked by a thin, reworked lag deposit of coarse sand and gravel. As sea level continued to rise, a relatively thick layer (as much as 15 m) of silty clay was deposited at the head of West Passage. During and since the transgression, tidal currents and waves have eroded and reworked Holocene deposits along the shore, within restricted channels, around topographic highs, and over the shallow bay-mouth sill.

  11. Sedimentary evolution of the Holocene subaqueous clinoform off the southern Shandong Peninsula in the Western South Yellow Sea

    NASA Astrophysics Data System (ADS)

    Qiu, Jiandong; Liu, Jian; Saito, Yoshiki; Yang, Zigeng; Yue, Baojing; Wang, Hong; Kong, Xianghuai

    2014-10-01

    Based on the stratigraphic sequence formed since the last glaciation and revealed by 3000 km long high-resolution shallow seismic profiles and the core QDZ03 acquired recently off the southern Shandong Peninsula, we addressed the sedimentary characteristics of a Holocene subaqueous clinoform in this paper. Integrated analyses were made on the core QDZ03, including sedimentary facies, sediment grain sizes, clay minerals, geochemistry, micro paleontology, and AMS 14C dating. The result indicates that there exists a Holocene subaqueous clinoform, whose bottom boundary generally lies at 15-40 m below the present sea level with its depth contours roughly parallel to the coast and getting deeper seawards. The maximum thickness of the clinoform is up to 22.5 m on the coast side, and the thickness contours generally spread in a banded way along the coastline and becomes thinner towards the sea. At the mouths of some bays along the coast, the clinoform stretches in the shape of a fan and its thickness is evidently larger than that of the surrounding sediments. This clinoform came into being in the early Holocene (about 11.2 cal kyr BP) and can be divided into the lower and upper depositional units (DU 2 and DU 1, respectively). The unit DU 2, being usually less than 3 m in thickness and formed under a low sedimentation rate, is located between the bottom boundary and the Holocene maximum flooding surface (MFS), and represents the sediment of a post-glacial transgressive systems tract; whereas the unit DU 1, the main body of the clinoform, sits on the MFS, belonging to the sediment of a high-stand systems tract from middle Holocene (about 7-6 cal kyr BP) to the present. The provenance of the clinoform differs from that of the typical sediments of the Yellow River and can be considered as the results of the joint contribution from both the Yellow River and the proximal coastal sediments of the Shandong Peninsula, as evidenced by the sediment geochemistry of the core. As is

  12. Coastal Modeling System

    DTIC Science & Technology

    2015-11-04

    and Hydrology - Coastal Community of Practice (CoP) as a Preferred model for Coastal Engineering and Coastal Navigation studies. The work unit...Coastal Inlets Research Program Coastal Modeling System The work unit develops the Coastal Modeling System (CMS) and conducts basic research to... models for simulations of waves, hydrodynamics, salinity and sediment transport, and morphology change. The CMS was identified by the USACE Hydraulics

  13. Coastal alert

    SciTech Connect

    Holing, D.

    1990-01-01

    This book explains: how offshore drilling affects the environment and the quality of life; how the government auctions off our threatened coast to the oil industry; how offshore oil and gas are developed; how the lease sale process works; how energy alternatives can replace offshore drilling; how citizen action works and how one can become involved; letters and press announcements; important contacts. The author believes that America needs to get off the energy consumption treadmill and onto the track that leads to reliance on renewable resources and energy efficiency. This book is intended to tell citizens how they can help bring about this transition and protect unique coastal resources.

  14. Evaluating mid-Holocene precipitation over Australasia and the Maritime Continent in climate models

    NASA Astrophysics Data System (ADS)

    Ackerley, Duncan; Reeves, Jessica

    2015-04-01

    The Australasian INTIMATE (INTegration of Ice-core, Marine and Terrestrial records) initiative (INQUA project #0809) was undertaken to develop a consistent chronological assessment of the climate of the past 30000 years over Australia, New Zealand and the Maritime Continent. Work has continued as part of SHAPE initiative (INQUA project #1302), but there has currently been little use of this comprehensive resource for evaluating the available climate model data. Therefore, this work presents the initial assessment of model simulations of the mid-Holocene over the Australasian and Maritime Continents (taken from the Paleoclimate Modelling Intercomparison Project, PMIP) in relation to those available data. The mid-Holocene (6 ka) encompasses a period after sea level stabilisation (around 8-7.5 ka) and before the onset of strong ENSO-related variability (post 4 ka). There is some evidence of possibly drier conditions over northern Australia with increased coastal dune activity, along with slightly wetter conditions over Borneo and Papua New Guinea. Weakening of the Southern Hemisphere mid-latitude westerlies (relative to the early Holocene) is also likely to have occurred, as evidenced by drier conditions in Western Tasmania and Victoria. The modelled results from the mid-Holocene simulations indicate that conditions were approximately 1-6% drier over much of continental Australia than at present. There is also evidence of slightly wetter conditions (1-3%) over the northern tip of Australia and parts of Papua New Guinea and Borneo. The Southern Hemisphere westerlies in the mid-latitudes (around 50S) are also weaker by 1-2 m s-1 in the model simulations. There are also differences in the seasonal cycle of precipitation and circulation in these models in response to the changes in the orbital parameters in the mid-Holocene relative to present day. The precipitation in the early half of the monsoon season (October, November and December-OND) is typically 10% higher in the

  15. Holocene evolution and sedimentation rate of Alikes Lagoon, Zakynthos island, Western Greece - preliminary results

    NASA Astrophysics Data System (ADS)

    Avramidis, P.; Kontopoulos, N.

    2009-03-01

    In the present study we present preliminary results of Zakynthos Alikes lagoon, which is one of the most seismically active regions of Greece. In order to estimate - interpret the Holocene evolution of the area and to reconstruct the palaeonvironmental changes, we based on the data of a 21 m sediment core. Sediment types, structure, colour, as well as contact depths and bed characteristics, were recorded in the field. Standarised sedimentological analysis were carried out, on 46 samples including grain size analysis, calculation of moment measures, and micro- and molluscan fossils of 17 selected samples. Moreover, radiocarbon age determinations have been made on individual Cardium shells from two horizons and whole - core Magnetic Susceptibility (MS) measurements were taken. The interpretation of depositional environments suggests a coastal environment (restricted-shallow) with reduced salinity such as a lagoon margin and in a tidal flat and/or marsh particularly. The maximum age of the study sediments is about 8500 BP. The rate of sedimentation between 8280 BP and 5590 BP was 5.3 mm/yr and between 5590 BP and modern times 1.03 mm/yr. The rate of sedimentation was higher until mid-Holocene while decrease after to 1.03 mm/yr, results which are similar to other coastal areas of western Greece.

  16. Middle Holocene aridity, eolian-dune accretion, and the formation of Lake Mattamuskeet, eastern North Carolina

    NASA Astrophysics Data System (ADS)

    Rodriguez, A. B.; Waters, M. N.; Piehler, M. F.

    2009-12-01

    The stratigraphic record of Lake Mattamuskeet, eastern North Carolina, shows an interval of eolian activity in the middle Holocene. There are about 500,000 elliptical lakes, wetlands, and depressions with elevated rims located on the Atlantic Coastal Plain named Carolina Bays. Lake Mattamuskeet is the largest (162 km2; mean depth 1.0 m), and formed when a blowout depression of a parabolic dune flooded 1540-1635 cal yr. BP. The parabolic dune is up to 2.0-m thick, contains sedimentary structures that indicate rapid deposition, and is composed of a coarsening-upward sequence of silt at the base to sandy silt at the top. Below the dune is an 8420-8605 cal yr. BP paleosol, which corresponds to a wet period in the area. The bottom half of the dune deposit contains abundant charcoal beds and laminae dated at ~6600 cal yr. BP, indicating fire was associated with initial formation of the parabolic dune. Middle Holocene climate of the southeast Atlantic coastal plain is not well constrained. Deposition of the eolian dune could be a local response to fire; or indicate a time of reduced effective moisture in the area. Given that pedogenesis on the dune did not initiate until ~2780-2965 cal yr. BP and flooding of the Lake basin did not occur for ~1000 years after that, effective moisture may have been low for approximately 3600 years after initial dune accretion.

  17. Overview of Recent Coastal Tectonic Deformation in the Mexican Subduction Zone

    NASA Astrophysics Data System (ADS)

    Ramírez-Herrera, M. Teresa; Kostoglodov, Vladimir; Urrutia-Fucugauchi, Jaime

    2011-08-01

    Holocene and Pleistocene tectonic deformation of the coast in the Mexico subudction margin is recorded by geomorphic and stratigraphic markers. We document the spatial and temporal variability of active deformation on the coastal Mexican subduction margin. Pleistocene uplift rates are estimated using wave-cut platforms at ca. 0.7-0.9 m/ka on the Jalisco block coast, Rivera-North America tectonic plate boundary. We examine reported measurements from marine notches and shoreline angle elevations in conjunction with their radiocarbon ages that indicate surface uplift rates increasing during the Holocene up to ca. 3 ± 0.5 m/ka. In contrast, steady rates of uplift (ca. 0.5-1.0 m/ka) in the Pleistocene and Holocene characterize the Michoacan coastal sector, south of El Gordo graben and north of the Orozco Fracture Zone (OFZ), incorporated within the Cocos-North America plate boundary. Significantly higher rates of surface uplift (ca. 7 m/ka) across the OFZ subduction may reflect the roughness of subducting plate. Absence of preserved marine terraces on the coastal sector across El Gordo graben likely reflects slow uplift or coastal subsidence. Stratigraphic markers and their radiocarbon ages show late Holocene (ca. last 6 ka bp) coastal subsidence on the Guerrero gap sector in agreement with a landscape barren of marine terraces and with archeological evidence of coastal subsidence. Temporal and spatial variability in recent deformation rates on the Mexican Pacific coast may be due to differences in tectonic regimes and to localized processes related to subduction, such as crustal faults, subduction erosion and underplating of subducted materials under the southern Mexico continental margin.

  18. Geomorphological & Geoarchaeological Indicators of the Holocene Sea-Level Changes on Ras El Hekma Area, NW Coast of Egypt

    NASA Astrophysics Data System (ADS)

    Torab, Magdy

    2016-02-01

    Ras El Hekma area is a part of the NW coast of Egypt. It is located on the Egyptian Mediterranean Coast, approximately 220 km West of Alexandria City. It is shaped as a triangle with its headland extending into the Mediterranean sea for about 15 km, and is occupied by sedimentary rocks belonging to the Tertiary and Quaternary Eras. Its western coastline consists of Pleistocene Oolitic limestone ridges with separated steep scarps, while the eastern coastline consists of sandy beaches, coastal spits, coastal bars, tombolos and bays. The objective of this paper is to define some geomorphological and geoarchaelological indicators of The Holocene sea-level changes in the study area, especially the geomorphic landforms such as: marine notches, cliffs, sea caves and benches. This is to add to some archaeological remains that have been discovered by the paper's author under the current sea level. These remains include: submerged ruins of Greek and Roman harbors, wells and fish tanks near the coastline (Leuke Akte, Hermaea, Phoinikous and Zygris), in addition to an ancient Roman harbor used during the World War II in Tell El Zaytun area (Site #6). Evaluations of the discovered archaeological remains help our understanding of the evolution of the sea level during the Holocene. This study is based on observation of the relative sea-level curves drawn of the Holocene, detailed geomorphological and Geoarchaelogical surveying, sampling, dating and mapping as well as satellite image interpretation and GIS techniques.

  19. Postglacial development of the eastern Gulf of Finland: from Pleistocene glacial lake basins to Holocene lagoon systems

    NASA Astrophysics Data System (ADS)

    Ryabchuk, Daria; Sergeev, Alexander; Kotilainen, Aarno; Hyttinen, Outi; Grigoriev, Andrey; Gerasimov, Dmitry; Anisimov, Mikhail; Gusentsova, Tatiana; Zhamoida, Vladimir; Amantov, Aleksey; Budanov, Leonid

    2016-04-01

    Despite significant amount of data, there are still lots of debatable questions and unsolved problems concerning postglacial geological history of the Eastern Gulf of Finland, the Baltic Sea. Among these problems are: 1) locations of the end moraine and glacio-fluvial deposits; 2) time and genesis of the large accretion forms (spits, bars, dunes); 3) basinwide correlations of trangression/regression culminations with the other parts of the Baltic Sea basin; 4) study of salinity, timing, frequency and intensity of Holocene saline water inflows and their links of sedimentation processes associated with climate change. Aiming to receive new data about regional postglacial development, the GIS analyses of bottom relief and available geological and geophysical data was undertaken, the maps of preQuaternary relief, moraine and Late Pleistocene surfaces, glacial moraine and Holocene sediments thicknesses were compiled. High-resolution sediment proxy study of several cores, taken from eastern Gulf of Finland bottom, allows to study grain-size distribution and geochemical features of glacial lake and Holocene sediments, to reveal sedimentation rates and paleoenvironment features of postglacial basins. Interdisciplinary geoarcheological approaches offer new opportunities for studying the region's geological history and paleogeography. Based on proxy marine geological and coastal geoarcheological studies (e.g. off-shore acoustic survey, side-scan profiling and sediment sampling, on-shore ground-penetrating radar (GPR SIR 2000), leveling, drilling, grain-size analyses and radiocarbon dating and archeological research) detailed paleogeographical reconstruction for three micro-regions - Sestroretsky and Lahta Lowlands, Narva-Luga Klint Bay and Southern Ladoga - were compiled. As a result, new high resolution models of Holocene geological development of the Eastern Gulf of Finland were received. Model calibration and verification used results from proxy geoarcheological research

  20. Ages, distributions, and origins of upland coastal dune sheets in Oregon, USA

    USGS Publications Warehouse

    Peterson, C.D.; Stock, E.; Price, D.M.; Hart, R.; Reckendorf, F.; Erlandson, J.M.; Hostetler, S.W.

    2007-01-01

    A total of ten upland dune sheets, totaling 245??km in combined length, have been investigated for their origin(s) along the Oregon coast (500??km in length). The ages of dune emplacement range from 0.1 to 103??ka based on radiocarbon (36 samples) and luminescence (46 samples) dating techniques. The majority of the emplacement dates fall into two periods of late-Pleistocene age (11-103??ka) and mid-late-Holocene age (0.1-8??ka) that correspond to marine low-stand and marine high-stand conditions, respectively. The distribution of both the late-Pleistocene dune sheets (516??km2 total surface area) and the late-Holocene dune sheets (184??km2) are concentrated (90% of total surface area) along a 100??km coastal reach of the south-central Oregon coast. This coastal reach lies directly landward of a major bight (Heceta-Perpetua-Stonewall Banks) on the continental shelf, at depths of 30-200??m below present mean sea level (MSL). The banks served to trap northward littoral drift during most of the late-Pleistocene conditions of lowered sea level (- 50 ?? 20??m MSL). The emerged inner-shelf permitted cross-shelf, eolian sand transport (10-50??km distance) by onshore winds. The depocenter sand deposits were reworked by the Holocene marine transgression and carried landward by asymmetric wave transport during early- to mid-Holocene time. The earliest dated onset of Holocene dune accretion occurred at 8??ka in the central Oregon coast. A northward migration of Northeast Pacific storm tracks to the latitude of the shelf depocenter (Stonewall, Perpetua, Heceta Banks) in Holocene time resulted in eastward wave transport from the offshore depocenter. The complex interplay of coastal morphology, paleosea-level, and paleoclimate yielded the observed peak distribution of beach and dune sand observed along the south-central Oregon coast. ?? 2007 Elsevier B.V. All rights reserved.

  1. Holocene fire activity and vegetation response in South-Eastern Iberia

    NASA Astrophysics Data System (ADS)

    Gil-Romera, Graciela; Carrión, José S.; Pausas, Juli G.; Sevilla-Callejo, Miguel; Lamb, Henry F.; Fernández, Santiago; Burjachs, Francesc

    2010-05-01

    Since fire has been recognized as an essential disturbance in Mediterranean landscapes, the study of long-term fire ecology has developed rapidly. We have reconstructed a sequence of vegetation dynamics and fire changes across south-eastern Iberia by coupling records of climate, fire, vegetation and human activities. We calculated fire activity anomalies (FAAs) in relation to 3 ka cal BP for 10-8 ka cal BP, 6 ka cal BP, 4 ka cal BP and the present. For most of the Early to the Mid-Holocene uneven, but low fire events were the main vegetation driver at high altitudes where broadleaved and coniferous trees presented a highly dynamic post-fire response. At mid-altitudes in the mainland Segura Mountains, fire activity remained relatively stable, at similar levels to recent times. We hypothesize that coastal areas, both mountains and lowlands, were more fire-prone landscapes as biomass was more likely to have accumulated than in the inland regions, triggering regular fire events. The wet and warm phase towards the Mid-Holocene (between ca 8 and 6 ka cal BP) affected the whole region and promoted the spread of mesophytic forest co-existing with Pinus, as FAAs appear strongly negative at 6 ka cal BP, with a less important role of fire. Mid and Late Holocene landscapes were shaped by an increasing aridity trend and the rise of human occupation, especially in the coastal mountains where forest disappeared from ca 2 ka cal BP. Mediterranean-type vegetation (evergreen oaks and Pinus pinaster- halepensis types) showed the fastest post-fire vegetation dynamics over time.

  2. Mississippi River delta plain, Louisiana coast, and inner shelf Holocene geologic framework, processes, and resources

    USGS Publications Warehouse

    Williams, S. Jeffress; Kulp, Mark; Penland, Shea; Kindinger, Jack L.; Flocks, James G.; Buster, Noreen A.; Holmes, Charles W.

    2009-01-01

    Extending nearly 400 km from Sabine Pass on the Texas-Louisiana border east to the Chandeleur Islands, the Louisiana coastal zone (Fig. 11.1) along the north-central Gulf of Mexico is the southern terminus of the largest drainage basin in North America (>3.3 million km2), which includes the Mississippi River delta plain where approximately 6.2 million kilograms per year of sediment is delivered to the Gulf of Mexico (Coleman 1988). The Mississippi River, active since at least Late Jurassic time (Mann and Thomas 1968), is the main distributary channel of this drainage system and during the Holocene has constructed one of the largest delta plains in the world, larger than 30,000 km2 (Coleman and Prior 1980; Coleman 1981; Coleman et al. 1998). The subsurface geology and geomorphology of the Louisiana coastal zone reffects a complex history of regional tectonic events and fluvial, deltaic, and marine sedimentary processes affected by large sea-level fluctuations. Despite the complex geology of the north-central Gulf basin, a long history of engineering studies and Scientific research investigations (see table 11.1) has led to substantial knowledge of the geologic framework and evolution of the delta plain region (see also Bird et al., chapter 1 in this volume). Mississippi River delta plain, Louisiana coast, and inner shelf Holocene geologic framework, processes, and resources. Available from: https://www.researchgate.net/publication/262802561_Mississippi_River_delta_plain_Louisiana_coast_and_inner_shelf_Holocene_geologic_framework_processes_and_resources [accessed Sep 13, 2017].

  3. Holocene Tree Line and Climate Change on the Queen Charlotte Islands, Canada

    NASA Astrophysics Data System (ADS)

    Pellatt, Marlow G.; Mathewes, Rolf W.

    1997-07-01

    Palynological study of two subalpine ponds on the Queen Charlotte Islands reveals changes in tree line and climate during the Holocene. The findings agree with previous reconstructions, from nearby Louise Pond on the Queen Charlotte Islands, that suggest a warmer-than-present climate and higher-than-present tree lines in the early Holocene (ca. 9600-6600 14C yr B.P.). Basal ages at SC1 Pond and Shangri-La Bog indicate that the basins did not hold permanent water before 7200 14C yr B.P., consistent with a warmer and drier early Holocene previously inferred from Louise Pond. Pollen and plant macrofossils indicate the initial establishment of subalpine conditions by 6090 ± 90 14C yr B.P., similar to the 5790 ± 130 14C yr B.P. age for cooling inferred from Louise Pond. Conditions similar to present were established at SC1 Pond by 3460 ± 100 14C yr B.P., confirming the previous estimate of 3400 14C yr B.P. at Louise Pond. This 3400 14C yr B.P. vegetation shift on the Queen Charlotte Islands corresponds with the beginning of the Tiedemann glacial advance in the south-coastal mountains of British Columbia (ca. 3300 14C yr B.P.), the Peyto and Robson glacial advances between 3300 and 2800 14C yr B.P. in the Rocky Mountains, and climatic cooling inferred from palynological studies throughout southern British Columbia, northern Washington, and southeast Alaska. These findings confirm that changes in regional climate influenced changes in vegetation in coastal British Columbia.

  4. Holocene evolution of a wave-dominated fan-delta: Godavari delta, India

    NASA Astrophysics Data System (ADS)

    Saito, Y.; Nageswara Rao, K.; Nagakumar, K.; Demudu, G.; Rajawat, A.; Kubo, S.; Li, Z.

    2013-12-01

    The Godavari delta is one of the world's largest wave-dominated deltas. The Godavari River arises in the Western Ghats near the west coast of India and drains an area of about 3.1x10^5 km^2, flowing about 1465 km southeast across the Indian peninsula to the Bay of Bengal. The Godavari delta consists of a gentle seaward slope from its apex (12 m elevation) at Rajahmundry and a coastal beach-ridge plain over a distance of about 75 km and covers ~5200 km^2 as a delta plain. The river splits into two major distributary channels, the Gautami and the Vasishta, at a barrage constructed in the mid-1800s. The coastal environment of the deltaic coast is microtidal (~1 m mean tidal range) and wave-dominated (~1.5 m mean wave height in the June-September SW monsoon season, ~0.8 m in the NE monsoon season). Models of the Holocene evolution of the Godavari delta have changed from a zonal progradation model (e.g. Nageswara Rao & Sadakata, 1993) to a truncated cuspate delta model (Nageswara Rao et al., 2005, 2012). Twelve borehole cores (340 m total length), taken in the coastal delta plain during 2010-2013, yielded more than 100 C-14 dates. Sediment facies and C-14 dates from these and previous cores and remote-sensing data support a new delta evolution model. The Holocene coastal delta plain is divided into two parts by a set of linear beach ridges 12-14 km landward from the present shoreline in the central part of the delta. The location of the main depocenter (lobe) has shifted during the Holocene from 1) the center to 2) the west, 3) east, 4) center, 5) west, and 6) east. The linear beach ridges separate the first three from the last three stages. These lobe shifts are controlled by river channel shifts near the apex. Just as the current linear shoreline of the central part of the delta and the concave-up nearshore topography are the result of coastal erosion of a cuspate delta, the linear beach ridges indicate a former eroded shoreline. An unconformity within the deltaic

  5. On Early Holocene Ice-Sheet/Sea-Level Interactions

    NASA Astrophysics Data System (ADS)

    Tornqvist, T. E.; Hijma, M.

    2011-12-01

    conundrum. Given the potentially large freshwater fluxes involved, this issue clearly needs to be resolved. Future progress as envisioned above will require more sophisticated sea-level studies worldwide, with decimeter-scale vertical resolution and sub-centennial scale temporal resolution. A particular challenge for the early Holocene is the diminishing role of coral records - compared to earlier stages of deglaciation - due to a lack of vertical resolution. On the other hand, the sparseness of coastal peat records before 6 to 8 ka presents another obstacle. A combination of increased prospecting offshore and targeting new types of sea-level indicators therefore deserves to be encouraged. Finally, all new field studies should be conducted in tandem with efforts to further refine glacial isostatic adjustment (GIA) models. Within this context, we foresee a primary focus on (1) optimizing site selection for the collection of new RSL records by means of GIA model predictions; (2) converting local observations of RSL rise into eustatic signals, including volumes and sources of meltwater discharge; and (3) capitalizing on gravitational fingerprint theory as outlined above.

  6. Late Cenozoic stages and molluscan zones of the U.S. Middle Atlantic Coastal Plain.

    USGS Publications Warehouse

    Blackwelder, B. W.

    1981-01-01

    Pliocene to Holocene deposits of the U.S.Atlantic Coastal Plain from Maryland to Georgia are divided into four stages and four substages using molluscan biostratigraphic data. These divisions are the Wiltonian and Burwellian Stages (early Pliocene), Gouldian and Windyan Substages of the Colerainian Stage (late Pliocene to early Pleistocene), and Myrtlean and Yongesian Substages of the Longian Stage (late Pleistocene to Holocene). These stages may be recognized from Florida to as far north as Massachusetts and will facilitate correlation with other regions.-Author

  7. Climatic fluctuations during the Holocene based on eastern Mediterranean continental shelf sediment cores

    NASA Astrophysics Data System (ADS)

    Mor-Federman, Tsofit; Bookman, Revital; Almogi-Labin, Ahuva; Herut, Barak

    2013-04-01

    .7074 in the southern core compared to ~0.7080 in the northern core, reflect a strong finger print of the Blue Nile on the sediments adjacent to the Nile cone that rapidly disappear northwards. The changes in the geochemical and sedimentary proxies are connected to Holocene climatic fluctuations. Change of provenances and decrease of fluvial input to the basin and in water column productivity around 5,500 years BP occur simultaneously with changes in the intensity of the monsoonal system over the headwaters of the Nile. These changes, that are present both at southern and central inner shelf, can be connected to the end of the African humid period. In the late Holocene, as the influence of the Nile on the central part of the shelf decreases, the Mediterranean climate system that originates in the northern hemisphere climate system is more evident. Cycles of ~1,500 years of coarse sediments probably originating from erosion in the coastal environment correlate with cold events known as the north Atlantic Bond cycles. Our results show the potential of shelf sediments to record and understand the control of climatic global systems on inner shelf sediment records.

  8. Lineaments in coastal plain sediments as seen in ERTS imagery

    NASA Technical Reports Server (NTRS)

    Withington, C. F.

    1973-01-01

    Examination of satellite imagery over the Atlantic Coastal Plain near Washington, D. C. shows numerous lineaments, which cannot be accounted for by any known cultural or natural features. At least some of these lineaments represent the surface expression of faults, for one of them has been correlated with the outcrop of a fault that had been traced for several miles in southern Prince Georges County, Maryland. If a substantial number of these lineaments do indeed represent fault traces, the fact that they show on the surface suggests that the geologic history of the Coastal Plain is much more complex than has previously been recognized, and that faulting may have occurred in the Holocene, much later than has generally been recognized. The importance that such recent movements could have on future development of the Coastal Plain should be emphasized.

  9. Tracking Nile Delta Vulnerability to Holocene Change

    PubMed Central

    Marriner, Nick; Flaux, Clément; Morhange, Christophe; Stanley, Jean-Daniel

    2013-01-01

    Understanding deltaic resilience in the face of Holocene climate change and human impacts is an important challenge for the earth sciences in characterizing the full range of present and future wetland responses to global warming. Here, we report an 8000-year mass balance record from the Nile Delta to reconstruct when and how this sedimentary basin has responded to past hydrological shifts. In a global Holocene context, the long-term decrease in Nile Delta accretion rates is consistent with insolation-driven changes in the ‘monsoon pacemaker’, attested throughout the mid-latitude tropics. Following the early to mid-Holocene growth of the Nile’s deltaic plain, sediment losses and pronounced erosion are first recorded after ~4000 years ago, the corollaries of falling sediment supply and an intensification of anthropogenic impacts from the Pharaonic period onwards. Against the backcloth of the Saharan ‘depeopling’, reduced river flow underpinned by a weakening of monsoonal precipitation appears to have been particularly conducive to the expansion of human activities on the delta by exposing productive floodplain lands for occupation and irrigation agriculture. The reconstruction suggests that the Nile Delta has a particularly long history of vulnerability to extreme events (e.g. floods and storms) and sea-level rise, although the present sediment-starved system does not have a direct Holocene analogue. This study highlights the importance of the world’s deltas as sensitive archives to investigate Holocene geosystem responses to climate change, risks and hazards, and societal interaction. PMID:23922692

  10. Hydrogeologic framework of the Virginia coastal plain

    USGS Publications Warehouse

    Meng, Andrew A.; Harsh, John F.

    1988-01-01

    This report defines the hydrogeologic framework of the Virginia Coastal Plain and is a product of a comprehensive regional study to define the geology, hydrology, and geochemistry of the northern Atlantic Coastal Plain aquifer system extending from North Carolina to Long Island, New York. The Virginia Coastal Plain consists of an eastward-thickening wedge of generally unconsolidated, interbedded sands and clays, ranging in age from Early Cretaceous to Holocene. These sediments range in thickness from more than 6,000 feet beneath the northeastern part of the Eastern Shore Peninsula to nearly 0 feet along the Fall Line. Eight confined aquifers, eight confining units, and an uppermost water table aquifer are delineated as the hydrogeologic framework of the Coastal Plain sediments in Virginia. The nine regional aquifers, from oldest to youngest, are lower, middle, and upper Potomac, Brightseat, Aquia, Chickahominy-Piney Point, St. Marys-Choptank, Yorktown-Eastover, and Columbia. The Brightseat is a newly identified and correlated aquifer of early Paleoceneage. This study is one of other, similar studies of the Coastal Plain areas in North Carolina, Maryland-Delaware, New Jersey, and Long Island, New York. These combined studies provide a system of hydrogeologic units that can be identified and correlated throughout the northern Atlantic Coastal Plain. Data for this study were collected and analyzed from October 1979 to May 1983. The nine aquifers and eight confining units are identified and delineated by use of geophysical logs, drillers' information, and stratigraphic and paleontologic data. By correlating geophysical logs with hydrologic, stratigraphic, and paleontologic data throughout the Coastal Plain, a comprehensive multilayered framework of aquifers and confining units, each with distinct lithologic properties, was developed. Cross sections show the stratigraphic relationships of aquifers and confining units in the hydrogeologic framework of the Virginia

  11. Fossil mollusc-faunas: Their bearing on the Holocene evolution of the Lower Central Plain of Bangkok (Thailand)

    NASA Astrophysics Data System (ADS)

    Negri, Mauro Pietro

    2009-08-01

    In this work, fossil molluscan assemblages are analyzed in order to reconstruct the evolution of the Northern Gulf of Thailand during the Holocene. The marine sediments (Bangkok Clay Formation) of the Lower Central Plain of Bangkok and the coastal plain of Phetchaburi were sampled at 16 localities, obtaining fossil shells and mangrove peat whose 14C ages range from 9000 to 2000 CYBP. A statistical treatment of abundance data returned four major groups, namely the Dendostrea rosacea association (intertidal mud), the Corbula fortisulcata- Mactra luzonica association (shallow infralittoral sandy mud), the Nuculana mauritiana- Timoclea scabra association (infralittoral sand spit) and the Timoclea scabra- Arcopagia pudica association (infralittoral mud). The data allowed both a stratigraphic correlation along two transects covering all of the Holocene basin and the creation of digitalized maps showing the presumable extension of the Thai paleogulf around the apex of Flandrian transgression event (about 5500 CYBP).

  12. Natural variability in ocean carbon chemistry on the California margin during the Holocene

    NASA Astrophysics Data System (ADS)

    Chrystal, A. E.; Paytan, A.

    2011-12-01

    Limited information is available to understand the potential magnitude and consequences of ocean acidification in temperate coastal environments. Some regions, such as the California margin, are influenced both by terrestrial runoff and by a strong upwelling system, which brings nutrient-rich, but corrosive, low-pH and low [CO_{3}^{2-}] water to the surface. Coastal upwelling areas may therefore be particularly sensitive to additional carbon input due to anthropogenic carbon emissions. Regions with strong coastal upwelling are among the most biologically productive marine sites in the world and are fundamental to the integrity of oceanic food webs and economic fisheries. Thus, it is important that we understand how anthropogenic acidification will affect these coastal ecosystems. A critical step in understanding the influence of reduced pH and [CO_{3}^{2-}] on coastal environments is to quantify the natural variability in ocean pH over long timescales (thousands of years) and to constrain the components that impact carbon chemistry in coastal systems; these include terrestrial freshwater input, upwelling, circulation changes, productivity, and anthropogenic CO_{2} flux. We propose to create a baseline against which to compare anthropogenic change via an integrative study of these variables over the past 10,000 years (Holocene). As a preliminary step, we will measure Mg/Ca, B/Ca and U/Ca in benthic foraminifera from the Santa Monica Basin (ODP 1015) and compare these with existing radio-carbon measurements and high-resolution δ^{18}O and δ^{13}C records from the same site to evaluate pH changes in the context of variability in salinity, upwelling and circulation changes.

  13. Early Holocene estuary development of the Hesselø Bay area, southern Kattegat, Denmark and its implication for Ancylus Lake drainage

    NASA Astrophysics Data System (ADS)

    Bendixen, Carina; Boldreel, Lars Ole; Jensen, Jørn Bo; Bennike, Ole; Hübscher, Christian; Clausen, Ole Rønø

    2017-06-01

    High-resolution shallow seismic data, sediment core information, radiocarbon dating and sequence stratigraphy have been used to interpret the late glacial to early Holocene geological evolution of Hesselø Bay in the southern Kattegat, Denmark. A reconstruction of the early Holocene coastal environment and a description of coastal processes associated with a river outlet into the bay are presented. Weichselian glacial deposits form the lowermost interpreted unit, covered by late glacial (LG) and postglacial (PG, Holocene) sediments. A funnel-shaped estuary existed at the mouth of channels in the period 10.3-9.2 cal. ka BP; the channels drained water from south to north. The early PG is characterised by estuarine and coastal deposits. The early Holocene bars that developed in the estuary are preserved as morphological features on the present-day seabed, possibly as a result of rapid relative sea-level rise. The estuary existed simultaneously with the occurrence and drainage of the Ancylus Lake. The drainage of this lake occurred through the Dana River (palaeo-Great Belt channel) into the southern Kattegat and then into the study area. The level of the Ancylus Lake in the Baltic Sea region dropped significantly at about 10.2 cal. ka BP at the same time as the estuary developed in the Kattegat region. One outcome of the present study is an enhanced understanding of the Ancylus Lake drainage path. No evidence of major erosion is seen, which indicates non-catastrophic continuous water flow from the south without major drainage events of the Ancylus Lake to the southern Kattegat. During the Littorina transgression, coastal estuarine conditions characterized the Hesselø Bay area where elongated ridges formed a bar system. As the Littorina transgression continued, back-stepping of the bar system and coastline occurred. When the transgression breached the Great Belt threshold, flooding caused major erosion throughout the study area.

  14. Sea level changes in the Holocene

    SciTech Connect

    Tanner, W.F. )

    1993-03-01

    Beach ridge data provide much information on the history of sea level changes through all of Holocene time. Two data sets start at about 12,000 B.P., one of them essentially continuous to now with data every 40--50 yrs. Another starting at 7,600 B.P. is continuous to the present. Others span the last 3,200 years. These records agree reasonably closely, and show the Little Ice Age (since 1,200 A.D.). The sea level changes in these data include the following: (a) Early Holocene crisis, about 8,000 B.P. The Swedish (Baltic Sea) record ends about this time, the Hudson Bay record starts at roughly this time, and the Danish record has a 300--500-year gap at about this time. From the latter, it appears that sea level rose sharply, shortly before 8,000 B.P., and fell again shortly after 8,000 B.P. These were the largest changes in Holocene time. The vertical change may have been as much as 12--18 meters, and the rate of change as much as 5--8 cm/yr, perhaps the maximum possible. In stable areas, evidence for these changes are now 25--30 meters below sea level. (b) Early Holocene general rise, up to about 8,000 B.P. Evidence for this is now known only on uplifted coasts. (c) Middle Holocene high, 2 m above present MSL 7,000--5,500 B.P. (d) Middle Holocene low, 3--4 m below present MSL 5,000--3,500 B.P. (e) Several changes up to 2 meters, especially since 3,000 B.P. In general, rates of change have been close to 1 cm/yr (major exceptions noted above). The only persistent interval was that between beach ridges; each ridge and its associated swale seem to have been built by a sea-level rise-and-fall couplet, having dimensions so small (perhaps 5--30 cm) that they could be overlooked easily on tide-gauge records. The average apparent time interval was 35--50 years.

  15. Holocene sea-level change and the emergence of Neolithic seafaring in the Fuzhou Basin (Fujian, China)

    NASA Astrophysics Data System (ADS)

    Rolett, Barry V.; Zheng, Zhuo; Yue, Yuanfu

    2011-04-01

    Neolithic seafaring across the Taiwan Strait began approximately 5000 years ago and involved open-sea voyages over distances of at least 130 km. Rapid sea-level rise preceded the emergence of open-sea voyaging, but the possible role of environmental change as a stimulus for the development of seafaring is poorly understood. We investigate this problem by presenting a record of Holocene sea-level change and coastal transformation based on sediment cores obtained from the Fuzhou Basin on the coast of Fujian, China. The cores are located in direct proximity to archaeological sites of the Tanshishan Neolithic culture (5000-4300 cal BP), which is significant for its similarity to the earliest Neolithic cultures of Taiwan. Multiple lines of evidence record the early Holocene inundation of the Fuzhou Basin around 9000 cal BP, the mid-Holocene sea-level highstand, and the final Holocene marine transgression. This final transition is precisely documented, with AMS dates showing the change occurred close to 1900 cal BP. Our paleogeographic reconstruction shows that a large estuary filled the Fuzhou Basin during the mid-Holocene. Tanshishan and Zhuangbianshan, two of the major Fuzhou Basin Neolithic sites, are located today on hills nearly 80 km from the modern coastline. However, when the sites were settled around 5500-5000 cal BP, the marine transgression had transformed these hills into islands in the upper estuary. We suggest that the Neolithic era estuary setting, together with the lack of land suitable for rice paddy agriculture, inhibited intensive food production but favored a maritime orientation and the development of seafaring.

  16. Holocene deceleration of the Greenland Ice Sheet.

    PubMed

    MacGregor, Joseph A; Colgan, William T; Fahnestock, Mark A; Morlighem, Mathieu; Catania, Ginny A; Paden, John D; Gogineni, S Prasad

    2016-02-05

    Recent peripheral thinning of the Greenland Ice Sheet is partly offset by interior thickening and is overprinted on its poorly constrained Holocene evolution. On the basis of the ice sheet's radiostratigraphy, ice flow in its interior is slower now than the average speed over the past nine millennia. Generally higher Holocene accumulation rates relative to modern estimates can only partially explain this millennial-scale deceleration. The ice sheet's dynamic response to the decreasing proportion of softer ice from the last glacial period and the deglacial collapse of the ice bridge across Nares Strait also contributed to this pattern. Thus, recent interior thickening of the Greenland Ice Sheet is partly an ongoing dynamic response to the last deglaciation that is large enough to affect interpretation of its mass balance from altimetry. Copyright © 2016, American Association for the Advancement of Science.

  17. Holocene fault scarps near Tacoma, Washington, USA

    USGS Publications Warehouse

    Sherrod, B.L.; Brocher, T.M.; Weaver, C.S.; Bucknam, R.C.; Blakely, R.J.; Kelsey, H.M.; Nelson, A.R.; Haugerud, R.

    2004-01-01

    Airborne laser mapping confirms that Holocene active faults traverse the Puget Sound metropolitan area, northwestern continental United States. The mapping, which detects forest-floor relief of as little as 15 cm, reveals scarps along geophysical lineaments that separate areas of Holocene uplift and subsidence. Along one such line of scarps, we found that a fault warped the ground surface between A.D. 770 and 1160. This reverse fault, which projects through Tacoma, Washington, bounds the southern and western sides of the Seattle uplift. The northern flank of the Seattle uplift is bounded by a reverse fault beneath Seattle that broke in A.D. 900-930. Observations of tectonic scarps along the Tacoma fault demonstrate that active faulting with associated surface rupture and ground motions pose a significant hazard in the Puget Sound region.

  18. Introduction to Holocene environmental change in Kamchatka

    NASA Astrophysics Data System (ADS)

    Brooks, S. J.; Diekmann, B.; Jones, V. J.; Hammarlund, D.

    2015-11-01

    This volume brings together a collection of papers on Holocene environmental change in the Kamchatka Peninsula, in the Russian Far East. Much of the work that appears in these papers was completed under the auspices of two major research activities: a UK NERC-funded project Influence of global teleconnections on Holocene climate in Kamchatka, which dealt with the analysis of lake records collected during the Swedish Beringia 2005 expedition organised by the Swedish Polar Research Secretariat; and a Russian-German multidisciplinary research project KALMAR - Kurile-Kamchatka and Aleutian Marginal Sea-Island Arc Systems: Geodynamic and Climate Interaction in Space and Time, funded by the German Federal Ministry of Education and Research (BMBF).

  19. Holocene deceleration of the Greenland Ice Sheet

    NASA Astrophysics Data System (ADS)

    MacGregor, Joseph A.; Colgan, William T.; Fahnestock, Mark A.; Morlighem, Mathieu; Catania, Ginny A.; Paden, John D.; Gogineni, S. Prasad

    2016-02-01

    Recent peripheral thinning of the Greenland Ice Sheet is partly offset by interior thickening and is overprinted on its poorly constrained Holocene evolution. On the basis of the ice sheet’s radiostratigraphy, ice flow in its interior is slower now than the average speed over the past nine millennia. Generally higher Holocene accumulation rates relative to modern estimates can only partially explain this millennial-scale deceleration. The ice sheet’s dynamic response to the decreasing proportion of softer ice from the last glacial period and the deglacial collapse of the ice bridge across Nares Strait also contributed to this pattern. Thus, recent interior thickening of the Greenland Ice Sheet is partly an ongoing dynamic response to the last deglaciation that is large enough to affect interpretation of its mass balance from altimetry.

  20. The Holocene History of Placentia Bay, Newfoundland

    NASA Astrophysics Data System (ADS)

    Sheldon, Christina; Seidenkrantz, Marit-Solveig; Reynisson, Njáll; Juncker Hansen, Mette; Zilmer Christensen, Eva; Kuijpers, Antoon

    2013-04-01

    Marine sediments analyzed from cores taken in Placentia Bay, Newfoundland, located in the Labrador Sea, captured oceanographic and climatic changes from the end of the Younger Dryas through the Holocene. Placentia Bay is an ideal site to capture changes in both the south-flowing Labrador Current and the north-flowing Gulf Stream, currents which are closely tied to the strength of the North Atlantic sub-polar gyre and the North Atlantic Oscillation. Changes in the atmospheric and oceanographic circulation patterns in the North Atlantic after the last glacial period are inferred from faunal assemblages, mineralogy and dinoflagellate analyses. During the 2007 Akademik Ioffe cruise, three cores were taken from Placentia Bay: AI07-14G, representing the time period 12.7 to 9.8 cal kyr BP, AI07-10G, covering the period ca. 10.4 cal kya BP to the present, and AI07-12G, representing the last 5.7 cal kya. These cores have been analyzed using several climate proxies, including benthic foraminifera, diatoms, IP25, dinoflagellate cysts and XRF. Together, these cores provide high-resolution records of the changes in climatic conditions over the last ca. 13,000 years in the southern Labrador Sea. After the Younger Dryas ended, the beginning of the warmer early Holocene was recorded by an increase in productivity-linked foraminiferal and diatom assemblages, as well as a drop in the presence of the sea-ice indicator IP25 in core 14G (Pearce et al., 2012). Variability in atmospheric circulation during the Holocene was analyzed in core 12G and used to reconstruct changes in the mode of the North Atlantic Oscillation during the late Holocene by analysis of exotic pollen grains. Sea-surface conditions during the late Holocene in Placentia Bay reflect a decrease in the strength of the Labrador Current, based on warmer sea-surface temperatures and a simultaneous decline in Arctic water export, from ~4000 cal years to ~3000 cal years BP, which falls into the overall large-scale trend of

  1. Reconstruction of early Holocene paleoclimate and environment in the SW Kola region, Russian Arctic

    NASA Astrophysics Data System (ADS)

    Grekov, Ivan; Kolka, Vasiliy; Syrykh, Liudmila; Nazarova, Larisa

    2016-04-01

    , et al., 2013). Reconstruction of the Early Holocene average July air temperatures based on chironomid analysis showed that in the middle of the Peninsula air T July were around + 10.3oC which is below the modern values. A sharp warming took place then during the Mid Holocene optimum (Ilyashuk, 2000; Ilyashuk, 2013). The reconstructed Early Holocene T July of the southern part of the Peninsula are similar to the modern T July + 12oC. For a detailed reconstruction of paleogeographic environments of the south-western part of the Kola Peninsula in Holocene we studied the valley of Kolvica river and the southern shore of lake Kolvitsa (67.01-67.11 N; 33.17-33.48 E). Analysis of lithological sequences and radiocarbon dating of sediments of small lakes present a clear outline of the development of the studied region from 9.3 14C ka (10.5 cal. ka BP) to the present day. Based on micro-paleontological analyzes we performed a qualitative reconstruction of climatic conditions during the Holocene, which shows a clear change of cooling and warming in the studied area, as well as the dynamics of the White Sea coastal zone and the development of the studied lake basins. This project was financed by RFBR 15-35-50479 mol_nr.

  2. The Role of Middle and Late Holocene North Pacific Sea Surface Temperatures on Precipitation Patterns in the Western United States

    NASA Astrophysics Data System (ADS)

    Barron, J. A.; Anderson, L.; Starratt, S.; Wahl, D.; Anderson, L.; Addison, J. A.

    2015-12-01

    Comparative analyses of marine and terrestrial proxy records reveal regional changes in precipitation seasonality and relationships with sea surface temperatures (SSTs) as indicators of ocean-atmosphere dynamics. Enhanced La Niña-like conditions and cooler SSTs characterized the middle Holocene (~8.O to 4.0 ka) waters off northern California and in the eastern equatorial Pacific. Terrestrial records suggest that winters in the western US were generally dry, although wetter intervals attributed to winter precipitation beginning at ~5.5 ka are documented in coastal Oregon and Washington and in the northern Great Basin. Proxy studies suggest that the North American Monsoon (NAM) intensified beginning at ~7.5 ka, coinciding with warming Gulf of California SSTs coupled with a more northerly position of the Intertropical Convergence Zone (ITCZ). If monsoonal precipitation spread northward into the eastern Great Basin and the western Rockies of Colorado, it is possible that wetter intervals of the middle Holocene in Nevada, Utah, and western Colorado may reflect increases in both summer and winter precipitation. El Niño event frequency and intensity began increasing between 4.0 and 3.0 ka, when modern ocean-atmosphere dynamics appear to have been established along the California coastal margin. Effects included cool, wet winters, enhanced spring coastal upwelling that extended into the summer, and higher September-October SSTs corresponding with the end of the coastal upwelling season. Winters became wetter in both the coastal and interior regions of the western US, while spring and summers generally became drier. The intensity of NAM precipitation also declined due to a more southerly mean position of the ITCZ. By ~3.0 cal ka the modern climatology of the margins of eastern North Pacific was established, resulting in intensification of the northwest-southwest precipitation dipole and the development of distinct Pacific Decadal Oscillation cycles.

  3. Influence of Holocene stratigraphic architecture on ground surface settlements: A case study from the City of Pisa (Tuscany, Italy)

    NASA Astrophysics Data System (ADS)

    Sarti, Giovanni; Rossi, Veronica; Amorosi, Alessandro

    2012-12-01

    The Holocene stratigraphic architecture of modern coastal and deltaic plains has peculiar characteristics that may influence ground surface settlements. In the Pisa urban area, the inhomogeneous spatial distribution of geotechnically weak layers, typically formed during the mid-late Holocene (highstand) coastal progradation, is inferred to be responsible for urban ground settlement and building damage, as evidenced by the tilt of several surface structures, among which the famous Leaning Tower of Pisa is the most prominent. On the basis of integrated stratigraphic, sedimentological and geotechnical data from a wide georeferenced database, three facies associations with high deformability potential (Units 1-3) are identified in the uppermost 30 m as opposed to depositional facies (Units 4-5) with higher geotechnical strength. Whereas Unit 1 represents a thick, laterally extensive lagoonal clay deposit, the overlying highly deformable units (Units 2-3) show more discontinuous spatial distribution controlled by the Holocene paleohydrographic evolution of the Arno coastal plain. Unit 2, dated between the Neolithic and the Etruscan age (ca. 5000-2000 yr BP), is composed of swamp clays and silty clays recording lagoon infilling due to Arno Delta progradation. Units 3 and 4, which consist of wet levee deposits and stiff floodplain clays, respectively, formed during the subsequent phases of alluvial plain construction started around the Roman age (from ca. 2000 yr BP). Whereas Units 3 and 4 are recorded within the uppermost 5 m, fluvial and distributary channel sands (Unit 5) cut the underlying deltaic-alluvial succession at various stratigraphic levels, down to Unit 1. The spatial distribution of these units gives rise to three, locally juxtaposed, stratigraphic motifs in Pisa underground, reflecting different potential risks for settlement under building loads. We show how lateral changes in stratigraphic architecture account for the irregular spatial distribution of

  4. Glacial discharge, upwelling and productivity off the Adélie coast, Antarctica: results from a 171 m Holocene sediment core from IODP Expedition 318

    NASA Astrophysics Data System (ADS)

    Newton, Kate; Bendle, James; McKay, Robert; Albot, Anya; Moossen, Heiko; Seki, Osamu; Willmott, Veronica; Schouten, Stefan; Riesselman, Christina; Dunbar, Robert

    2016-04-01

    Antarctica's coastal oceans play a vital role in controlling both the global carbon cycle and climate change, through variations in primary production, ocean stratification and ice melt. Yet, the Southern Ocean remains the least studied region on Earth with respect to Holocene climate variability. The few Antarctic proximal marine sedimentary records available tend to be short, low resolution, and discontinuous. However, sediments recovered from the Adélie drift during IODP Expedition 318 present a new opportunity to study East Antarctic Holocene climatic evolution, at a resolution that facilitates direct comparison with ice-cores. A 171m core of Holocene laminated diatom ooze was recovered from site U1357, representing continuous Holocene accumulation in a climatically-sensitive coastal polynya. We present results of biomarker analyses (TEX86-L and compound specific fatty acid delta-D and delta-13C, and sterol delta-D) and grain size from throughout the Holocene, revealing the complexities of this climatically sensitive environment. Carbon isotopes are interpreted predominantly as a productivity signal via CO2 drawdown, whilst hydrogen isotopes reflect inputs of isotopically-depleted glacial meltwater from the large Mertz glacier tongue and other proximal glaciers. Both upwelling, as shown by TEX86-L and grain size, and glacial meltwater inputs, indicated by biomarker delta-D, appear to have an important control on productivity on various time scales. The latter may be forced by warm subsurface temperatures through basal melting of the Mertz glacier tongue, indicating both direct and indirect effects of upwelling on productivity. The post-glacial, Early Holocene appears to be characterized by a highly variable system, due to both strong upwelling and meltwater inputs, followed by a more stable and highly productive Middle Holocene under a warmer climate. During the Late Holocene, characterized by a sea-ice expansion, temperature-induced sea-ice melt may have

  5. Late Holocene climate: Natural or anthropogenic?

    NASA Astrophysics Data System (ADS)

    Ruddiman, W. F.; Fuller, D. Q.; Kutzbach, J. E.; Tzedakis, P. C.; Kaplan, J. O.; Ellis, E. C.; Vavrus, S. J.; Roberts, C. N.; Fyfe, R.; He, F.; Lemmen, C.; Woodbridge, J.

    2016-03-01

    For more than a decade, scientists have argued about the warmth of the current interglaciation. Was the warmth of the preindustrial late Holocene natural in origin, the result of orbital changes that had not yet driven the system into a new glacial state? Or was it in considerable degree the result of humans intervening in the climate system through greenhouse gas emissions from early agriculture? Here we summarize new evidence that moves this debate forward by testing both hypotheses. By comparing late Holocene responses to those that occurred during previous interglaciations (in section 2), we assess whether the late Holocene responses look different (and thus anthropogenic) or similar (and thus natural). This comparison reveals anomalous (anthropogenic) signals. In section 3, we review paleoecological and archaeological syntheses that provide ground truth evidence on early anthropogenic releases of greenhouse gases. The available data document large early anthropogenic emissions consistent with the anthropogenic ice core anomalies, but more information is needed to constrain their size. A final section compares natural and anthropogenic interpretations of the δ13C trend in ice core CO2.

  6. Changing sedimentation in tidal flat sediments of the southern North Sea from the Holocene to the present: a geochemical approach

    NASA Astrophysics Data System (ADS)

    Dellwig, O.; Hinrichs, J.; Hild, A.; Brumsack, H.-J.

    2000-12-01

    This study presents geochemical evidence for a change in depositional energy conditions of tidal flat sediments (southern North Sea) from the Holocene, i.e. human unaffected, to present-day conditions. We investigated Holocene and present tidal flat sediments and suspended particulate matter (SPM) from the NW German coastal area (Spiekeroog Island back-barrier area and Jade Bay), as well as sediments from the Helgoland Island mud hole area. Samples were analysed for bulk parameters (TC, TIC), major (Al, Ca, Fe, Mg, K, P, Si, Ti), and trace elements (Ba, Pb, Rb, Sr, V, Zn, Zr). Enrichment factors versus average shale reveal four groups of elements for the investigated Holocene and present sediments. Fe, Mg, K, Ba, Rb, and V show a shale-like behaviour and enrichments of Ca and Sr reflect the occurrence of carbonate, whereas higher levels of P, Pb, and Zn in the present samples are due to pollution. The fourth group consists of Si, Ti, and Zr, which may be used as indicators of depositional energy because these elements are concentrated by particle sorting effects. The most pronounced geochemical difference between the Holocene and present tidal flat sediments is an enrichment of Zr in the present samples. As Zr is commonly associated with heavy minerals, this enrichment indicates a higher depositional energy environment in the present sediments, which can be traced to modern dike building. The same effect, i.e. increasing current velocities, is responsible for a general depletion of fine-grained, Al-rich, material in the present sediments. The examination of SPM shows that large amounts of this fine-grained material are present in the water column and may be transported from the intertidal system into the open North Sea. The comparison of a calculated Holocene clay accumulation rate with modern estimates of SPM deposition in the German Bight reveals about a two-fold higher deposition of fine material in the Holocene tidal flats. As the sediments from the Helgoland

  7. East meets West: Differing views of the Aleutian Low's role in affecting Holocene productivity in the Subarctic North Pacific Ocean

    NASA Astrophysics Data System (ADS)

    Addison, J. A.; Finney, B. P.; Harada, N.

    2012-12-01

    Modern instrumental and monitoring observations indicate strong multi-decadal changes and spatial heterogeneities affect climate and marine ecosystems in the North Pacific Ocean. Networks of high-resolution paleoclimate archives from this dynamic region are therefore required to describe changes prior to historical records. We present new decadally-resolved marine sediment core data from the Kuril Islands in the Sea of Okhotsk, together with sub-decadal data from the temperate fjords of the Gulf of Alaska (GoAK). These distant sites are located along the western (Kuril) and eastern (GoAK) boundaries of the Subarctic North Pacific Ocean, where micronutrient-rich coastal waters interact with North Pacific high-nutrient-low-chlorophyll (HNLC) waters to drive highly productive marine ecosystems. In the Sea of Okhotsk, a notable increase in opal concentrations (a proxy for past siliceous primary productivity) occurs during the middle Holocene between ~5000 and 6000 yrs ago, while alkenone-based warm season SST proxies either decline or remain relatively constant. A similar middle Holocene increase in opal concentrations is also observed in the GoAK during an interval of declining warm season coastal SAT as inferred from pollen transfer functions [Heusser et al., 1985]. Declining summer solar insolation during the middle Holocene can explain the overall decline in warm-season SST in both the Sea of Okhotsk and the Gulf of Alaska. However, as the increase in opal likely reflects an improvement in North Pacific phytoplankton growing conditions during the spring/summer bloom season, then the opal increase seems unlikely to be related directly to summer solar insolation. We propose a middle Holocene intensification of the Aleutian Low (AL) pressure cell and concomitant changes in North Pacific circulation may be responsible. In both regions, several potential mechanisms related to an intensified AL could result in greater productivity including: (i) increased advection

  8. High-resolution climatic evolution of coastal northern California during the past 16,000 years

    USGS Publications Warehouse

    Barron, J.A.; Heusser, L.; Herbert, T.; Lyle, M.

    2003-01-01

    Holocene and latest Pleistocene oceanographic conditions and the coastal climate of northern California have varied greatly, based upon high-resolution studies (ca. every 100 years) of diatoms, alkenones, pollen, CaCO3%, and total organic carbon at Ocean Drilling Program (ODP) Site 1019 (41.682??N, 124.930??W, 980 m water depth . Marine climate proxies (alkenone sea surface temperatures [SSTs] and CaCO3%) behaved remarkably like the Greenland Ice Sheet Project (GISP)-2 oxygen isotope record during the B??lling-Allerod, Younger Dryas (YD), and early part of the Holocene. During the YD, alkenone SSTs decreased by >3??C below mean B??lling-Allerod and Holocene SSTs. The early Holocene (ca. 11.6 to 8.2 ka) was a time of generally warm conditions and moderate CaCO3 content (generally >4%). The middle part of the Holocene (ca. 8.2 to 3.2 ka) was marked by alkenone SSTs that were consistently 1-2??C cooler than either the earlier or later parts of the Holocene, by greatly reduced numbers of the gyre-diatom Pseudoeunotia doliolus (<10%), and by a permanent drop in CaCO3% to <3%. Starting at ca. 5.2 ka, coastal redwood and alder began a steady rise, arguing for increasing effective moisture and the development of the north coast temperate rain forest. At ca. 3.2 ka, a permanent ca. 1??C increase in alkenone SST and a threefold increase in P. doliolus signaled a warming of fall and winter SSTs. Intensified (higher amplitude and more frequent) cycles of pine pollen alternating with increased alder and redwood pollen are evidence that rapid changes in effective moisture and seasonal temperature (enhanced El Nin??o-Southern Oscillation [ENSO] cycles) have characterized the Site 1019 record since about 3.5 ka.

  9. Holocene Tsunami deposits associated with earthquakes along Pacific coast, northeast Japan

    NASA Astrophysics Data System (ADS)

    Suzuki, H.; Imaizumi, T.; Ishiyama, T.; Miyauchi, T.; Kagohara, K.; Haraguchi, T.; Marushima, N.; Omachi, T.

    2009-12-01

    We investigated Holocene tsumami deposits along the Pacific coast of northeast Japan in order to define the ages and source areas of earthquakes generating large tsunamis. Sediment cores were collected by using geoslicers and hand augers at alluvial lowlands interpreted by aerial photographs, and ages of deposits were dated by radiocarbon methods and tephrochronology. Pacific coast of northeast Japan faces the Japan trench where Pacific plate subducts beneath the Eurasian plate, so that the coast has repeatedly experienced some large tsunamis following historical interplate earthquakes (the 1896 Meiji Sanriku Tsunami, the 1793 Kansei Tsunami, the 1611 Keicho Sanriku Tsunami and the 869 Jogan Tsunami). While the southern part along the Pacific coast (from the Sendai Plain to the Joban coastal region) has nearly straight shorelines and well developed coastal lowlands, the northern part (the Sanriku coastal region) has typical ria shorelines and poorly developed coastal lowlands. Multiple sand layers are identified between muddy or peaty sediments in drilled core samples to a depth of 1-5.5 m at several coastal areas, which is located at backlands of beach ridges and natural levees. In the southern part along the Pacific coast, sand layers corresponding to the 869 Jogan Tsunami are identified, and the older sand layers suggest that tsunamis which are as large as the 869 tsunami have occurred at few hundred years intervals over the past 5000 years. On the other hand, in the northern part along the Pacific coast, multiple sand layers which indicate the arrival of large tsunamis are also found at the similar intervals to the southern coast during 6000-2000 years ago, but most of the depositional ages of the sand layers do not coincide with those of the southern coast. We suggest that earthquakes generating large tsunamis along northern and southern Pacific coast of northeast Japan have both occurred at few hundred years intervals during the late Holocene, but in most

  10. The Anthropocene - and International Law of the Holocene

    NASA Astrophysics Data System (ADS)

    Vidas, D.

    2012-12-01

    may become necessary. First, with few exceptions, today's Law of the Sea regulates human impacts on the ocean and submarine components of the Earth System in terms of the political boundaries of sovereignty and jurisdiction, translated into law: basically, this is what is expressed through the various maritime zones and the division of jurisdictional competences among coastal and flag states. However, prospects of rising sea-levels and the consequences for the current law-of-the-sea architecture will eventually necessitate deep-going changes in that legal framework. Second, also the ultimate objectives of the current international regulations will need to be re-formulated, and crafted so as to enable us to better channel and confine human impacts on the Earth System. Moreover, some fundamentals of International Law - not least the concept of 'territory' and state control over territory as a constituent element of statehood in international law - may, as we leave the Holocene and enter the Anthropocene, require profound re-examination. REFERENCES: Vidas, D., 2011. The Anthropocene and the International Law of the Sea, Philosophical Transactions of the Royal Society - A, Vol. 369, pp. 909-925. Zalasiewicz, J., M. Williams, W. Steffen and P.J. Crutzen, 2010. The New World of the Anthropocene, Environmental Science & Technology, Vol. 44, pp. 2228-2231.

  11. National Coastal Condition Assessment

    EPA Pesticide Factsheets

    It is important to monitor coastal waters for potentially harmful trends and to identify areas in good condition. That is the purpose of the National Coastal Condition Assessment, which EPA conducts every few years.

  12. Fire regimes and vegetation change in tropical northern Australia during the late-Holocene

    NASA Astrophysics Data System (ADS)

    Mackenzie, Lydia; Moss, Patrick; Ulm, Sean; Sloss, Craig; Heijnis, Henk; Jacobsen, Geraldine

    2016-04-01

    This study explores the impact of human occupation and abandonment on fire regimes and vegetation communities in the South Wellesley Islands, Gulf of Carpentaria, tropical northern Australia, using charcoal and pollen analysis from four sediment records. Pollen analysis from wetland sediments reveal vegetation succession from mangrove communities to hypersaline mudflats and open woodlands occurred during the late-Holocene. Aquatic species replaced salt tolerant species as the prograding shoreline and dune development formed the Marralda wetlands by 800 cal a BP on the south east coast of Bentinck Island. Wetlands developed on the north and west coast by 500 and 450 cal a BP, respectively. The timing of wetland initiation indicates localised late-Holocene sea level regression, stabilisation and coastal plain development in the Gulf of Carpentaria. Wetland initiation encouraged permanent human occupation of the South Wellesley archipelago, with ongoing archaeological research finding permanent occupation in the last 1500 years, followed by a significant increase in sites from 700 years ago, which peaks over the last 300 years. Macro-charcoal (>125μm) accumulation rates provide a record of fire intensity and frequency across the Island. Both local and regional fire events increase in the last 700 years as traditional owners occupied the Island, with local fires occurring every 104 and 74 years on average (N= 4 and 5 respectively). In the 1950's traditional Indigenous Kaiadilt fire management practices ceased, with the frequency and peak magnitude of fire events significantly increasing and vegetation communities becoming more open. The South Wellesley Islands were unoccupied until the 1980's and were not influenced by European occupation. This study of an Island ecosystem during the late-Holocene provides insight into the effect of human presence and fire regimes on vegetation composition and distribution in a fire resilient environment.

  13. 'Cape capture': Geologic data and modeling results suggest the holocene loss of a Carolina Cape

    USGS Publications Warehouse

    Thieler, E.R.; Ashton, A.D.

    2011-01-01

    For more than a century, the origin and evolution of the set of cuspate forelands known as the Carolina Capes-Hatteras, Lookout, Fear, and Romain-off the eastern coast of the United States have been discussed and debated. The consensus conceptual model is not only that these capes existed through much or all of the Holocene transgression, but also that their number has not changed. Here we describe bathymetric, lithologic, seismic, and chronologic data that suggest another cape may have existed between Capes Hatteras and Lookout during the early to middle Holocene. This cape likely formed at the distal end of the Neuse-Tar-Pamlico fiuvial system during the early Holocene transgression, when this portion of the shelf was fiooded ca. 9 cal (calibrated) kyr B.P., and was probably abandoned by ca. 4 cal kyr B.P., when the shoreline attained its present general configuration. Previously proposed mechanisms for cape formation suggest that the large-scale, rhythmic pattern of the Carolina Capes arose from a hydrodynamic template or the preexisting geologic framework. Numerical modeling, however, suggests that the number and spacing of capes can be dynamic, and that a coast can self-organize in response to a high-angle-wave instability in shoreline shape. In shoreline evolution model simulations, smaller cuspate forelands are subsumed by larger neighbors over millennial time scales through a process of 'cape capture.' The suggested former cape in Raleigh Bay represents the first interpreted geological evidence of dynamic abandonment suggested by the self-organization hypothesis. Cape capture may be a widespread process in coastal environments with large-scale rhythmic shoreline features; its preservation in the sedimentary record will vary according to geologic setting, physical processes, and sea-level history. ?? 2011 Geological Society of America.

  14. Holocene Deglaciation of the Scandinavian Ice Sheet: Preliminary 10Be Ages

    NASA Astrophysics Data System (ADS)

    Cuzzone, J. K.; Clark, P. U.; Marcott, S. A.; Pekka Lunka, J.; Wohlfarth, B.; Carlson, A. E.

    2012-12-01

    The response of ice sheets to a warming climate is not well understood. Because we are limited in our understanding of present dynamics, reconstructing the deglaciation of former ice sheets allows for a better understanding of how past ice sheets responded to a warming climate along with their contribution to sea-level rise. These reconstructions also serve as critical constraints for ice sheet modeling efforts. Here, we present a suite of new 10Be ages from erratic boulders along three transects spanning southern to northern Sweden and Finland, that improve our understanding of the deglaciation of the Scandinavian Ice Sheet (SIS) beginning ~ 11.7ka through its final demise during the early Holocene. Preliminary dates from southern Finland, beginning at the Salpausselka Youngers Dryas moraine (11.5 ± 0.7 ka, n=2), inland southern Finland near Jyvaskyla (11.5 ± 0.5ka, n=2), and coastal Finland (~60km from Gulf of Bothnia) near Vimpeli (11.5 ± 0.4ka, n=1) indicate a rapid retreat following the Younger Dryas for Southern Finland (~500km within uncertainty of ages). Preliminary dates also exist for Northern Finland, near Inari (10.3 ± 0.5ka, n=2). Additional ages now being processed at PRIME Lab, Purdue University, which will establish a basis for SIS retreat from all sampled sites, will also be presented. These new data will help to constrain the Holocene deglaciation of the SIS and its associated retreat rates, and establish the SIS contribution to Holocene sea level rise, which will improve our understanding of ice-sheet response to a warming climate.

  15. Vegetation Response and Landscape Dynamics of Indian Summer Monsoon Variations during Holocene: An Eco-Geomorphological Appraisal of Tropical Evergreen Forest Subfossil Logs

    PubMed Central

    Kumaran, Navnith K. P.; Padmalal, Damodaran; Nair, Madhavan K.; Limaye, Ruta B.; Guleria, Jaswant S.; Srivastava, Rashmi; Shukla, Anumeha

    2014-01-01

    The high rainfall and low sea level during Early Holocene had a significant impact on the development and sustenance of dense forest and swamp-marsh cover along the southwest coast of India. This heavy rainfall flooded the coastal plains, forest flourishing in the abandoned river channels and other low-lying areas in midland.The coastline and other areas in lowland of southwestern India supply sufficient evidence of tree trunks of wet evergreen forests getting buried during the Holocene period under varying thickness of clay, silty-clay and even in sand sequences. This preserved subfossil log assemblage forms an excellent proxy for eco-geomorphological and palaeoclimate appraisal reported hitherto from Indian subcontinent, and complements the available palynological data. The bulk of the subfossil logs and partially carbonized wood remains have yielded age prior to the Holocene transgression of 6.5 k yrs BP, suggesting therein that flooding due to heavy rainfall drowned the forest cover, even extending to parts of the present shelf. These preserved logs represent a unique palaeoenvironmental database as they contain observable cellular structure. Some of them can even be compared to modern analogues. As these woods belong to the Late Pleistocene and Holocene, they form a valuable source of climate data that alleviates the lack of contemporaneous meteorological records. These palaeoforests along with pollen proxies depict the warmer environment in this region, which is consistent with a Mid Holocene Thermal Maximum often referred to as Holocene Climate Optimum. Thus, the subfossil logs of tropical evergreen forests constitute new indices of Asian palaeomonsoon, while their occurrence and preservation are attributed to eco-geomorphology and hydrological regimes associated with the intensified Asian Summer Monsoon, as recorded elsewhere. PMID:24727672

  16. Vegetation response and landscape dynamics of Indian Summer Monsoon variations during Holocene: an eco-geomorphological appraisal of tropical evergreen forest subfossil logs.

    PubMed

    Kumaran, Navnith K P; Padmalal, Damodaran; Nair, Madhavan K; Limaye, Ruta B; Guleria, Jaswant S; Srivastava, Rashmi; Shukla, Anumeha

    2014-01-01

    The high rainfall and low sea level during Early Holocene had a significant impact on the development and sustenance of dense forest and swamp-marsh cover along the southwest coast of India. This heavy rainfall flooded the coastal plains, forest flourishing in the abandoned river channels and other low-lying areas in midland.The coastline and other areas in lowland of southwestern India supply sufficient evidence of tree trunks of wet evergreen forests getting buried during the Holocene period under varying thickness of clay, silty-clay and even in sand sequences. This preserved subfossil log assemblage forms an excellent proxy for eco-geomorphological and palaeoclimate appraisal reported hitherto from Indian subcontinent, and complements the available palynological data. The bulk of the subfossil logs and partially carbonized wood remains have yielded age prior to the Holocene transgression of 6.5 k yrs BP, suggesting therein that flooding due to heavy rainfall drowned the forest cover, even extending to parts of the present shelf. These preserved logs represent a unique palaeoenvironmental database as they contain observable cellular structure. Some of them can even be compared to modern analogues. As these woods belong to the Late Pleistocene and Holocene, they form a valuable source of climate data that alleviates the lack of contemporaneous meteorological records. These palaeoforests along with pollen proxies depict the warmer environment in this region, which is consistent with a Mid Holocene Thermal Maximum often referred to as Holocene Climate Optimum. Thus, the subfossil logs of tropical evergreen forests constitute new indices of Asian palaeomonsoon, while their occurrence and preservation are attributed to eco-geomorphology and hydrological regimes associated with the intensified Asian Summer Monsoon, as recorded elsewhere.

  17. Source, transport, and evolution of saline groundwater in a shallow Holocene aquifer on the tidal deltaplain of southwest Bangladesh

    NASA Astrophysics Data System (ADS)

    Worland, Scott C.; Hornberger, George M.; Goodbred, Steven L.

    2015-07-01

    Deltaic groundwater resources are often vulnerable to degradation from seawater intrusion or through interaction with saline paleowaters. The Ganges-Brahmaputra-Meghna River delta, in Bangladesh and West Bengal, India, is a particularly vulnerable area with an estimated 20 million coastal inhabitants directly affected by saline drinking water. The shallow groundwater of the coastal regions is primarily brackish with pockets of fresher water. A small-scale hydrologic investigation of groundwater salinity beneath an embanked tidal channel island was undertaken to explore possible hydrogeological explanations of the distribution of water salinities in the shallow aquifer. This study employs a combination of 3H and 14C dating, electromagnetic subsurface mapping, and a 2-D solute transport model. The authors conclude that the shallow groundwater salinity can best be explained by the slow infiltration of meteoric water into paleo-brackish estuarine water that was deposited during the early-mid Holocene.

  18. The linkage between marine sediment records and changes in Holocene Saharan landscape: simulating the dust cycle

    NASA Astrophysics Data System (ADS)

    Egerer, Sabine; Claussen, Martin; Reick, Christian; Stanelle, Tanja

    2016-04-01

    Marine sediment records reveal an abrupt and strong increase in dust deposition in the North Atlantic at the end of the African Humid Period about 4.9 ka to 5.5 ka ago (deMenocal et al., 2000; McGee et al., 2013). The change in dust flux has been attributed to varying Saharan land surface cover. Alternatively, the enhanced dust accumulation is linked to enhanced surface winds and a consequent intensification of coastal upwelling. We present simulation results from a recent sensitivity study, where we demonstrate for the first time the direct link between dust accumulation in marine cores and changes in Saharan land surface during the Holocene. We have simulated timeslices of he mid-Holocene (6 ka BP) and pre-industrial (1850 AD) dust cycle as a function of Saharan land surface cover and atmosphere-ocean conditions using the coupled atmosphere-aerosol model ECHAM6.1-HAM2.1. We prescribe mid-Holocene vegetation cover based on a vegetation reconstruction from pollen data (Hoelzmann et al., 1998) and mid-Holocene lake surface area is determined using a water routing and storage model (Tegen et al., 2002). In agreement with data from marine sediment cores, our simulations show that mid-Holocene dust deposition fluxes in the North Atlantic were two to three times lower compared with pre-industrial fluxes. We identify Saharan land surface characteristics to be the main control on dust transport from North Africa to the North Atlantic. We conclude that the variation in dust accumulation in marine cores is likely related to a transition of the Saharan landscape during the Holocene and not due to changes in atmospheric or ocean conditions alone. Reference: deMenocal, P., Ortiz, J., Guilderson, T., Adkins, J., Sarnthein, M., Baker, L., and Yarusinsky, M.: Abrupt onset and termination of the African Humid Period:: rapid climate responses to gradual insolation forcing, Quaternary Science Reviews, 19, 347-361, 2000. Hoelzmann, P., Jolly, D., Harrison, S. P., Laarif, F

  19. A mid-Holocene candidate tsunami deposit from the NW Cape (Western Australia)

    NASA Astrophysics Data System (ADS)

    May, Simon Matthias; Falvard, Simon; Norpoth, Maike; Pint, Anna; Brill, Dominik; Engel, Max; Scheffers, Anja; Dierick, Manuel; Paris, Raphaël; Squire, Peter; Brückner, Helmut

    2016-03-01

    Although extreme-wave events are frequent along the northwestern coast of Western Australia and tsunamis in 1994 and 2006 induced considerable coastal flooding locally, robust stratigraphical evidence of prehistoric tropical cyclones and tsunamis from this area is lacking. Based on the analyses of X-ray computed microtomography (μCT) of oriented sediment cores, multi-proxy sediment and microfaunal analyses, optically stimulated luminescence (OSL) and 14C-AMS dating, this study presents detailed investigations on an allochthonous sand layer of marine origin found in a back-barrier depression on the NW Cape Range peninsula. The event layer consists of material from the adjacent beach and dune, fines and thins inland, and was traced up to ~ 400 m onshore. Although a cyclone-induced origin cannot entirely be ruled out, the particular architecture and fabric of the sediment, rip-up clasts and three subunits point to deposition by a tsunami. As such, it represents the first stratigraphical evidence of a prehistoric, mid-Holocene tsunami in NW Western Australia. It was OSL-dated to 5400-4300 years ago, thus postdating the regional mid-Holocene sea-level highstand.

  20. Sources and characteristics of terrestrial carbon in Holocene-scale sediments of the East Siberian Sea

    NASA Astrophysics Data System (ADS)

    Keskitalo, Kirsi; Tesi, Tommaso; Bröder, Lisa; Andersson, August; Pearce, Christof; Sköld, Martin; Semiletov, Igor P.; Dudarev, Oleg V.; Gustafsson, Örjan

    2017-09-01

    Thawing of permafrost carbon (PF-C) due to climate warming can remobilise considerable amounts of terrestrial carbon from its long-term storage to the marine environment. PF-C can be then be buried in sediments or remineralised to CO2 with implications for the carbon-climate feedback. Studying historical sediment records during past natural climate changes can help us to understand the response of permafrost to current climate warming. In this study, two sediment cores collected from the East Siberian Sea were used to study terrestrial organic carbon sources, composition and degradation during the past ˜ 9500 cal yrs BP. CuO-derived lignin and cutin products (i.e., compounds solely biosynthesised in terrestrial plants) combined with δ13C suggest that there was a higher input of terrestrial organic carbon to the East Siberian Sea between ˜ 9500 and 8200 cal yrs BP than in all later periods. This high input was likely caused by marine transgression and permafrost destabilisation in the early Holocene climatic optimum. Based on source apportionment modelling using dual-carbon isotope (Δ14C, δ13C) data, coastal erosion releasing old Pleistocene permafrost carbon was identified as a significant source of organic matter translocated to the East Siberian Sea during the Holocene.

  1. Chronology of Holocene Cheniers and Oyster Reefs on the Coast of Bohai Bay, China

    NASA Astrophysics Data System (ADS)

    Wang, Hong; Van Strydonck, Mark

    1997-03-01

    Cheniers and oyster reefs are two essential components of Holocene strata on the coast of Bohai Bay, China. The existing nonconventional 14C dates, often with unsuitable sample positions, less-tested samples, and unreasonable data comparisons, limit the refined analysis of the local chronostratigraphy. On the basis of a number of pretreatment routines, including geological investigations, X-ray diffraction analysis (XRD), δ 13C measurement of shells, selection of appropriate shell species ( Umboniumsp. and Terebridae) for 14C dating, and determination of the local mean δ 13C value (-2.68‰ PDB) for the common shells, a set of samples was radiocarbon-dated by Accelerator Mass Spectrometry (AMS). These new ages, obtained from the lower part of cheniers, enable us to estimate the initiation of the cheniers, and confirm that the existing nonconventional dates are often questionable due to unsuitable sample positions. Another two AMS ages, dated for two different microgrowth layers, precipitated in a varying water body, of the same Crassostrea gigasshell are statistically identical within 2σ error. This implies that the different water masses in the coastal environment would be rapidly in balance with the contemporaneous atmospheric CO 2. Both MARINE93 and INTERCAL93 were used for calibration of radiocarbon dates. These amended the time frame of the local Holocene history.

  2. Pleistocene To Holocene Human, Climatic and Environmental Changes In Central and Eastern Java (indonesia)

    NASA Astrophysics Data System (ADS)

    Sémah, A.-M.; Sémah, F.; Simanjuntak, H. T.

    The period between 21,000 and 6000 BP, which includes the Pleistocene-Holocene boundary, is likely to have known drastic environmental changes in the Indones ian archipelago, as seen from various sedimentary, pollen analytic, and archaeological records. In a low altitude swampy basin of central Java which yielded a thick clay and peat stratigraphy, several steps can be pointed between the driest period noticed prior 15,000 BP up to a climatic optimum c. 8,000 BP: a significant increase in humidity from c. 15,000 BP onwards, an extension of the forest after 10,500 BP, completion of almost everwet conditions c. 8,500 BP before a forest regression at c.6000 BP. Correlative excavations of the cave fillings near the coast of the Indian ocean, in the Southern Mountains of Java island, reflect conspicuous changes in the archaeological record: a more or less occasional human occupation of the caves during the late Plaistocene is followed by an intensive one in the early Holocene. Human groups, who brought new technologies (like sophisticated bone tools) had to adapt to and get their subsistence in an extending rain forest like environment, with a faunal turnover (Macaca and Presbytis dominance) or in the numerous flooded basins which formed during that period (fresh water molluscs gathering and smaller tortoise hunting). They carried out close contacts with the coastal area and used also the caves as burial places.

  3. Late Holocene vegetation changes in relation with climate fluctuations and human activity in Languedoc (southern France)

    NASA Astrophysics Data System (ADS)

    Azuara, J.; Combourieu-Nebout, N.; Lebreton, V.; Mazier, F.; Müller, S. D.; Dezileau, L.

    2015-12-01

    Holocene climate fluctuations and human activity since the Neolithic have shaped present-day Mediterranean environments. Separating anthropogenic effects from climatic impacts to better understand Mediterranean paleoenvironmental changes over the last millennia remains a challenging issue. High-resolution pollen analyses were undertaken on two cores from the Palavasian lagoon system (Hérault, southern France). These records allow reconstruction of vegetation dynamics over the last 4500 years. Results are compared with climatic, historical and archeological archives. A long-term aridification trend is highlighted during the late Holocene, and three superimposed arid events are recorded at 4600-4300, 2800-2400 and 1300-1100 cal BP. These periods of high-frequency climate variability coincide in time with the rapid climatic events observed in the Atlantic Ocean (Bond et al., 2001). From the Bronze Age (4000 cal BP) to the end of the Iron Age (around 2000 cal BP), the spread of sclerophyllous taxa and loss of forest cover result from anthropogenic impact. Classical Antiquity is characterized by a major reforestation event related to the concentration of rural activity and populations in coastal plains leading to forest recovery in the mountains. A major regional deforestation occurred at the beginning of the High Middle Ages. Around 1000 cal BP, forest cover is minimal while the cover of olive, chestnut and walnut expands in relation to increasing human influence. The present-day vegetation dominated by Mediterranean shrubland and pines has been in existence since the beginning of the 20th century.

  4. Late Holocene vegetation changes in relation with climate fluctuations and human activities in Languedoc (Southern France)

    NASA Astrophysics Data System (ADS)

    Azuara, J.; Combourieu-Nebout, N.; Lebreton, V.; Mazier, F.; Müller, S. D.; Dezileau, L.

    2015-09-01

    Holocene climate fluctuations and human activities since the Neolithic have shaped present-day Mediterranean environments. Separating anthropogenic effects from climatic impacts to reconstruct Mediterranean paleoenvironments over the last millennia remains a challenging issue. High resolution pollen analyses were undertaken on two cores from the Palavasian lagoon system (Hérault, southern France). These records allow reconstruction of vegetation dynamics over the last 4500 years. Results are compared with climatic, historical and archeological archives. A long-term aridification trend is highlighted during the Late Holocene and three superimposed arid events are recorded at 4600-4300, 2800-2400 and 1300-1100 cal BP. These periods of climatic instability coincide in time with the rapid climatic events depicted in the Atlantic Ocean (Bond et al., 2001). From the Bronze Age (4000 cal BP) to the end of the Iron Age (around 2000 cal BP), the spread of evergreen taxa and loss of forest cover result from anthropogenic impact. The Antiquity is characterized by a major reforestation event related to the concentration of rural activities and populations in coastal plains leading to forest recovery in the mountains. A major regional deforestation occurred at the beginning of the High Middle Ages. Around 1000 cal BP, forest cover is minimal while cover of olive, chestnut and walnut expands in relation to increasing human influence. The present day vegetation dominated by Mediterranean shrubland and pines has been in existence since the beginning of the 20th century.

  5. Pre-transgression morphology and Holocene stratigraphy of the Delaware estuarine and Atlantic coasts

    SciTech Connect

    Chrzastowski, J.J.; Kraft, J.C.

    1985-01-01

    The Holocene stratigraphic sequences of the ocean and estuarine coasts of Delaware record the marine transgression and sedimentary infill of deeply incised valleys of the ancestral Delaware River and its tributaries. Suspended sediment of the Delaware estuary has played an important role in the antecedent valley infill. Fine-grained deposition marginal to the ocean coast occurs in lagoonal, tidal stream and marsh environments. The stratigraphy of the lagoonal and estuarine shore areas show that a 1-2 m depth ravinement process is operative in these low energy coastal environments producing an eroded surface which precedes and is stratigraphically separate from the deeper (10 m depth) Atlantic shoreface ravinement. As the transgression continues, preservation of the Holocene sedimentary sequences is dependent on rate of sea-level rise and depth of ravinement. Relief on the antecedent topography is equally important, with maximum preservation occurring in antecedent valleys. At interglacial peak sea levels, lithosomes of all the paralic environments (including barriers and spits) may be preserved in lateral and vertical relationships unmodified by the ravinement process.

  6. Holocene deposits of reservoir-quality sand along the Central South Carolina coastline

    SciTech Connect

    Sexton, W.J.; Hayes, M.O.

    1996-06-01

    The Holocene coastal sand deposits of the central South Carolina coastline were investigated to estimate volumes of reservoir-quality (RQ) sediments. These sand bodies, which vary considerably in size, thickness, shape, and continuity, were deposited in a variety of depositional settings including barrier islands, ebb-tidal deltas, exposed sand flats, tidal sand ridges, and tidal point bars. To identify the RQ sediment for each sand-body type, a conservative mud cutoff value of 15% was chosen. Average thickness values ranged from 6 m for barrier island deposits to 15 m for ebb-tidal deltas. Of the six most significant RQ sand depositional environments on the central portion of the South Carolina coast, ebb-tidal delta complexes accounted for 77% of all RQ sediments. This dominance of the ebb-tidal delta deposits is attributed to the relatively large tidal range in the area (up to 3 m) and to the presence of a number of large, incised alluvial valleys, which are host to estuarine complexes with large tidal prisms. If the Holocene sand deposits along the central 115 km of the South Carolina coast were preserved in the rock record, a total of 1.3 X 10{sup 6} ac-ft of RQ sands would be present, a significant amount considering the short time interval of approximately 5000 yr.

  7. The Posidonia oceanica marine sedimentary record: A Holocene archive of heavy metal pollution.

    PubMed

    Serrano, O; Mateo, M A; Dueñas-Bohórquez, A; Renom, P; López-Sáez, J A; Martínez Cortizas, A

    2011-10-15

    The study of a Posidonia oceanica mat (a peat-like marine sediment) core has provided a record of changes in heavy metal abundances (Fe, Mn, Ni, Cr, Cu, Pb, Cd, Zn, As and Al) since the Mid-Holocene (last 4470yr) in Portlligat Bay (NW Mediterranean). Metal contents were determined in P. oceanica. Both, the concentration records and the results of principal components analysis showed that metal pollution in the studied bay started ca. 2800yr BP and steadily increased until present. The increase in Fe, Cu, Pb, Cd, Zn and As concentrations since ca. 2800yr BP and in particular during Greek (ca. 2680-2465cal BP) and Roman (ca. 2150-1740cal BP) times shows an early anthropogenic pollution rise in the bay, which might be associated with large- and short-scale cultural and technological development. In the last ca. 1000yr the concentrations of heavy metals, mainly derived from anthropogenic activities, have significantly increased (e.g. from ~15 to 47μg g(-1) for Pb, ~23 to 95μg g(-1) for Zn and ~8 to 228μg g(-1) for As). Our study demonstrates for the first time the uniqueness of P. oceanica meadows as long-term archives of abundances, patterns, and trends of heavy metals during the Late Holocene in Mediterranean coastal ecosystems.

  8. Holocene climate and climate variability of the northern Gulf of Mexico and adjacent northern Gulf Coast: A review

    USGS Publications Warehouse

    Poore, Richard Z.

    2008-01-01

    Marine records from the northern Gulf of Mexico indicate that significant multidecadal- and century-scale variability was common during the Holocene. Mean annual sea-surface temperature (SST) during the last 1,400 years may have varied by 3°C, and excursions to cold SST coincide with reductions in solar output. Broad trends in Holocene terrestrial climate and environmental change along the eastern portion of the northern Gulf Coast are evident from existing pollen records, but the high-frequency details of climate variability are not well known. Continuous and well-dated records of climate change and climate variability in the western portion of the northern Gulf Coast are essentially lacking.Information on Holocene floods, droughts, and storm frequency along the northern Gulf Coast is limited. Records of floods may be preserved in continental shelf sediments, but establishing continuity and chronologies for sedimentary sequences on the shelf presents challenges due to sediment remobilization and redeposition during storms. Studies of past storm deposits in coastal lakes and marshes show promise for constructing records of past storm frequency. A recent summary of sea-level history of the northern Gulf Coast indicates sea level was higher than modern sea level several times during the last few thousand years.

  9. Mid-Holocene climate and land-sea interaction along the southern coast of Saurashtra, western India

    NASA Astrophysics Data System (ADS)

    Banerji, Upasana S.; Pandey, Shilpa; Bhushan, Ravi; Juyal, Navin

    2015-11-01

    The relict mudflat from the southern Saurashtra coast of Gujarat was investigated using geochemical and palynological analyses supported by radiocarbon dating to understand whether climate fluctuations and sea-level operated in tandem during mid-Holocene. The study revealed that the Saurashtra coast experienced relatively wet climatic conditions with simultaneous occurrence of marginally high sea-level between 4710 and 2825 cal yr BP. Subsequently, a gradual onset of aridity and lowering of the sea-level was observed between 2825 and 1835 cal yr BP, and further a slight decrease in aridity is observed after 1835 cal yr BP. The present day coastal configuration was probably achieved after around 1500 cal yr BP. Considering the tectonic instability of Saurashtra coast (land level changes), the effective mid-Holocene sea-level was estimated to be ∼1 m higher than the present. The study demonstrates that sea-level changes, climate variability and land-level changes were coupled during the mid-Holocene.

  10. Revised Ages for Laminated Sediment and a Holocene-Marker Diatom from the Northern California Continental Slope

    USGS Publications Warehouse

    Hemphill-Haley, E.; Gardner, J.V.

    1994-01-01

    Conventional and accelerator mass spectrometry 14C ages indicate that laminated sediment in three cores from the northern California continental slope near 38??N and 39??N were deposited between 42,000 and 25,000 yr B.P. This revises and refines our previous estimates that laminated sediment accumulated during the late Pleistocene to early Holocene (J. V. Gardner and E. Hemphill-Haley, 1986, Geology 14, 691-694). Preservation of laminated sediment on the upper slope in this area suggests a period of intense coastal upwelling, high primary productivity, and resultant depletion of oxygen in bottomwaters preceding the onset of global glacial conditions. The transition from Pleistocene to Holocene conditions, and the establishment of a modern climatic regime driven by the California Current, included the incursion of the subtropical diatom, Pseudoeunotia doliola. P. doliola is common in sediment younger than about 10,000 yr and thus is a reliable marker species for identifying Holocene deposits off northern California.

  11. Land-level changes from a late Holocene earthquake in the northern Puget lowland, Washington

    USGS Publications Warehouse

    Kelsey, H.M.; Sherrod, B.; Johnson, S.Y.; Dadisman, S.V.

    2004-01-01

    An earthquake, probably generated on the southern Whidbey Island fault zone, caused 1-2 m of ground-surface uplift on central Whidbey Island ???2800-3200 yr ago. The cause of the uplift is a fold that grew coseismically above a blind fault that was the earthquake source. Both the fault and the fold at the fault's tip are imaged on multichannel seismic refection profiles in Puget Sound immediately east of the central Whidbey Island site. Uplift is documented through contrasting histories of relative sea level at two coastal marshes on either side of the fault. Late Holocene shallow-crustal earthquakes of Mw = 6.5-7 pose substantial seismic hazard to the northern Puget Lowland. ?? 2004 Geological Society of America.

  12. Late holocene vegetation change on Andros Island, Bahamas: Evidence of Caribbean climate change and human colonization

    SciTech Connect

    Kjhellmark, E. )

    1994-06-01

    Sediment cores from blue holes on Andros Island, Bahamas, contain a remarkably detailed record of the past vegetation. A Holocene dry period from at least 2000 to 1500 yr bp is evidenced by sedimentological and palynological facies from the basal portion of one core. The coincides with a suggested dry period in Central America and the Caribbean region, but it has never been found this far north and east. A hardwood vegetation is established at ca. 1500 yr bp and remains a dominant vegetation component until [approximately]900 yr bp when pine and charcoal begin to increase in abundance. At 750 yr bp, pinewoods replace the hardwoods and charcoal peaks indicating human disturbance. The 900 yr bp date for the onset of significant human disturbance is relatively late, compared with other estimates of human colonization of the Caribbean region, suggesting that the occupation of island interiors may have lagged behind that of the coastal regions.

  13. Middle Holocene Unconformity in Seneca Lake, NY

    NASA Astrophysics Data System (ADS)

    Curtin, T. M.; Crocker, M.; Loddengaard, K.

    2008-12-01

    The post-glacial history of the Finger Lakes, NY have involved several changes in lake levels throughout the latest Pleistocene and Holocene, resulting from the changing position of the retreating Laurentide ice sheet, river outlet position, glacial rebound, and water balance. Previous studies of high-resolution seismic reflection profiles from three Finger Lakes define a middle Holocene erosional surface at water depths as great as 26 m in the northern end of each of lake. There are two proposed hypotheses to explain the origin of the observed erosional surfaces: 1) subaerial erosion during a lake lowstand and 2) erosion resulting from increased internal seiche activity. To evaluate these hypotheses, we examined a series of 2 to 5 m long piston cores collected along a north-south transect from one of the Finger Lakes, Seneca Lake. Cores were correlated using distinctive changes in the profiles of grain size, loss-on-ignition, and magnetic susceptibility. We recognize a significant erosional unconformity of early to middle Holocene sediment at modern depths <60 m because portions of the normal deepwater sediment sequence were missing in cores and were commonly replaced by a thin zone of sand and abraded shells (bivalves, gastropods). At water depths >60 m, the unconformity continues as a conformable zone. We attribute the unconformity to wave abrasion and nearshore current winnowing of the shoreface during a lowstand. With an assumption of an effective 20 m wave base, the depth to the low level lake surface responsible for the unconformity is estimated to be 40 m. The age of the unconformity is ~6 ka, based on radiocarbon ages of lithologic boundaries in the sediment cores. Because the unconformity grades into a conformable zone in deepwater cores that display no change in lithology, we hypothesize that the large-scale lake level drop is likely not the result of climate change, but rather a change in accommodation space in the northern portion of the lake basin due

  14. Holocene peatland initiation in the Greater Everglades

    NASA Astrophysics Data System (ADS)

    Dekker, Stefan; de Boer, Hugo; Dermody, Brian; Wagner-Cremer, Friederike; Wassen, Martin; Eppinga, Maarten

    2015-04-01

    The mechanisms involved in the initiation and development of the Greater Everglades peatland ecosystems in South Florida (USA) remain a topic of discussion. In this study, we present an overview of basal ages of peat deposits in South Florida, which shows two major episodes of peatland initiation between 7.0-4.5 kyr and 3.5-2.0 kyr. Our analysis of regional climate proxy datasets led to three alternative hypotheses that may explain the timing and duration of these two peatland initiation episodes: (1) decreased drainage due to relative sea level (RSL) rise during the Holocene (2) gradual increase in precipitation throughout the Holocene, and (3) a combination of increasing precipitation, rising RSL and oscillations in the climate system. We test whether these three hypotheses can explain the pattern of initiation and development of the Greater Everglades peatlands using models that simulate the non-linear processes involved in peat production and decomposition in combination with the local drainage conditions of Southern Florida. The model results suggest that RSL-rise alone cannot predict the onset of peat initiation in the Greater Everglades using our model setup. The model also implies that the climate was wet enough for peat development also during the early Holocene. The first two hypothesized mechanisms in combination with climate oscillations may explain the onset of peat accumulation at 8.2 kyr BP. The two-phased character of peat land initiation may be explained by the spatial distribution of local drainage conditions. As peatland development is highly non-linear, our model uncovers a mechanistic way how peats can suddenly shift from a dry high equilibrium to a wet low equilibrium resulting in lake formation as observed in paleo-ecological studies in the Greater Everglades.

  15. Holocene peatland initiation in the Greater Everglades

    NASA Astrophysics Data System (ADS)

    Dekker, Stefan C.; de Boer, Hugo J.; Dermody, Brian J.; Wagner-Cremer, Friederike; Wassen, Martin J.; Eppinga, Maarten B.

    2015-02-01

    The mechanisms involved in the initiation and development of the Greater Everglades peatland ecosystems remain a topic of discussion. In this study, we first present an overview of basal ages of peat deposits in South Florida, which shows two major episodes of peatland initiation between 7.0-4.5 kyr and 3.5-2.0 kyr. Our analysis of regional climate proxy data sets led to three alternative hypotheses that may explain the timing and duration of these two peatland initiation episodes: (1) decreased drainage due to relative sea level (RSL) rise during the Holocene, (2) gradual increase in precipitation throughout the Holocene, and (3) a combination of increasing precipitation, rising RSL, and oscillations in the climate system. We test whether these three hypotheses can explain the pattern of initiation and development of the Greater Everglades peatlands using models that simulate the nonlinear processes involved in peat production and decomposition. The model results suggest that RSL rise could explain the onset of peatland initiation and imply that the climate was wet enough for peat development also during the early Holocene. The first two hypothesized mechanisms in combination with climate oscillations may explain the onset of peat accumulation at 8.2 kyr B.P. The two-phased character of peatland initiation maybe explained by the spatial distribution of local drainage conditions. As peatland development is highly nonlinear, our model uncovers a mechanistic way how peats can suddenly shift from a dry high equilibrium to a wet low equilibrium resulting in lake formation as observed in paleoecological studies in the Greater Everglades.

  16. Solar pacing of storm surges, coastal flooding and agricultural losses in the Central Mediterranean

    NASA Astrophysics Data System (ADS)

    Kaniewski, David; Marriner, Nick; Morhange, Christophe; Faivre, Sanja; Otto, Thierry; van Campo, Elise

    2016-04-01

    Storm surges, leading to catastrophic coastal flooding, are amongst the most feared natural hazards due to the high population densities and economic importance of littoral areas. Using the Central Mediterranean Sea as a model system, we provide strong evidence for enhanced periods of storminess leading to coastal flooding during the last 4500 years. We show that long-term correlations can be drawn between storminess and solar activity, acting on cycles of around 2200-yr and 230-yr. We also find that phases of increased storms and coastal flooding have impacted upon mid- to late Holocene agricultural activity on the Adriatic coast. Based on the general trend observed during the second half of the 20th century, climate models are predicting a weakening of Mediterranean storminess. By contrast, our new data suggest that a decrease in solar activity will increase and intensify the risk of frequent flooding in coastal areas.

  17. Solar pacing of storm surges, coastal flooding and agricultural losses in the Central Mediterranean.

    PubMed

    Kaniewski, David; Marriner, Nick; Morhange, Christophe; Faivre, Sanja; Otto, Thierry; Van Campo, Elise

    2016-04-29

    Storm surges, leading to catastrophic coastal flooding, are amongst the most feared natural hazards due to the high population densities and economic importance of littoral areas. Using the Central Mediterranean Sea as a model system, we provide strong evidence for enhanced periods of storminess leading to coastal flooding during the last 4500 years. We show that long-term correlations can be drawn between storminess and solar activity, acting on cycles of around 2200-yr and 230-yr. We also find that phases of increased storms and coastal flooding have impacted upon mid- to late Holocene agricultural activity on the Adriatic coast. Based on the general trend observed during the second half of the 20(th) century, climate models are predicting a weakening of Mediterranean storminess. By contrast, our new data suggest that a decrease in solar activity will increase and intensify the risk of frequent flooding in coastal areas.

  18. Solar pacing of storm surges, coastal flooding and agricultural losses in the Central Mediterranean

    PubMed Central

    Kaniewski, David; Marriner, Nick; Morhange, Christophe; Faivre, Sanja; Otto, Thierry; Van Campo, Elise

    2016-01-01

    Storm surges, leading to catastrophic coastal flooding, are amongst the most feared natural hazards due to the high population densities and economic importance of littoral areas. Using the Central Mediterranean Sea as a model system, we provide strong evidence for enhanced periods of storminess leading to coastal flooding during the last 4500 years. We show that long-term correlations can be drawn between storminess and solar activity, acting on cycles of around 2200-yr and 230-yr. We also find that phases of increased storms and coastal flooding have impacted upon mid- to late Holocene agricultural activity on the Adriatic coast. Based on the general trend observed during the second half of the 20th century, climate models are predicting a weakening of Mediterranean storminess. By contrast, our new data suggest that a decrease in solar activity will increase and intensify the risk of frequent flooding in coastal areas. PMID:27126207

  19. Holocene environmental change in Kamchatka: A synopsis

    NASA Astrophysics Data System (ADS)

    Brooks, S. J.; Diekmann, B.; Jones, V. J.; Hammarlund, D.

    2015-11-01

    We present a synthesis of the results of a multiproxy, multisite, palaeoecological study of Holocene environmental change in Kamchatka, Far East Russia, details of which are presented elsewhere in the volume. We summarise the results of the analyses of pollen, diatom, chironomid, and testate amoebae assemblages, together with stable isotopes of oxygen and carbon, and sediment characteristics from the sediments of five lakes and a peat succession on a latitudinal gradient of the Kamchatka Peninsula, to infer environmental change and establish the major climate forcers and climatic teleconnections. There are synchronous shifts in the assemblage composition of most of the biota and across most sites at 6.5-6.2 ka BP, 5.2 ka BP, 4.0 ka BP, and 3.5 ka BP, suggesting a response to strong regional climate forcing at these times. These dates correspond to the warmest part of the Holocene Thermal Maximum (HTM) (6.5-6.2 ka BP), the beginning of the Neoglacial cooling (5.2 ka BP), the coolest and wettest part of the Neoglacial (4.0 ka BP), and a switch to warmer and drier conditions at 3.5 ka BP. Our results provide evidence for the penetration and domination of different air masses at different periods during the Holocene. Cool and dry periods in winter (e.g., at 6.0 ka BP) were driven by a relatively weak pressure gradient between the Siberian High and the Aleutian Low, whereas cool, wet periods in winter (e.g., the Neoglacial and during the LIA) developed when these two systems increased in strength. Warm, dry, continental periods in summer (e.g., at 2.5 ka BP) were driven by a weakening of the Siberian High. We find that the timing of the HTM in Kamchatka is later than in the Eurasian arctic but similar to northern Europe and the sub-arctic part of eastern Siberia. This progressive onset of the HTM was due to the effects of postglacial ice-sheet decay that modulated the routes of westerly storm tracks in Eurasia. A major ecosystem driver was the Siberian dwarf pine Pinus

  20. The Birougou Mountains: Forested throughout the Holocene

    NASA Astrophysics Data System (ADS)

    Pietsch, S. A.; Tanga, J.-J.; Ngok-Banak, L.

    2009-04-01

    The Congo basin with an area of ~400 million ha harbours the second largest tropical forest complex of the world which covers ~60% of the area. Besides tropical rain forest the savannah biome comprises the second naturally abundant ecosystem type. During the Holocene (20.000 yrs. BP - Modern Times) the distribution of forest and savannas changed with changing climate and during the last glacial maximum (~20.000 yrs. BP) most of the Congo basin was covered by savannas and the Congolian rain forests were confined to refuge areas. Later the distribution between savannas and rainforest changed with changing climate, whereby in some regions rainforest and savannas replaced each other while on some sites one vegetation type persisted. During drier periods of the Holocene the rain forest biome was confined to refuge areas, which formed a conservation reservoir for forest re-extension during more humid, i.e. forest favourable, climatic periods. In order to understand the dynamics of the forest/savannah replacement process reference states of patches of stable savannah or stable rain forest are needed. Within this paper we will describe a patch of stable rain forest vegetation located at the Birougou Mountains in Gabon, and demonstrate that rain forest vegetation has continuously persisted since the Holocene climate optimum dated at around ~6.000 yrs. B.P. by using the signature of stable Carbon isotope discrimination of photosynthesis. Savannah grasses follow the C4-type of photosynthesis while forest vegetation exhibits C3 photosynthesis. Accordingly they differ in the d13C ratios of carbon incorporated into biomass. Soil organic Carbon originates from decomposition of litter inputs. d13C values along a vertical soil profile thus indicate persistence or past changes in vegetation cover. 14C age of soil humic acids, indicate the mean residence time of soil organic carbon. Results indicate that at the Birougou mountains (in contrast to other parts of the Congo basin) litter

  1. Mediterranean Holocene climate, environment and human societies

    NASA Astrophysics Data System (ADS)

    Holmgren, Karin; Gogou, Alexandra.; Izdebski, Adam.; Luterbacher, Juerg.; Sicre, Marie-Alexandrine; Xoplaki, Elena

    2016-03-01

    This paper introduces the reader to a special issue of articles that explores links and processes behind societal change, climate change and environmental change in a Holocene perspective in the Mediterranean region. All papers are, by purpose, co-authored by scientists representing different disciplines. The cross-cutting theme has been to reach beyond simple explanations of potential climate-society relationships and advance our understanding on how to improve research methods and theories in the field. The thirteen papers in this issue address these questions in three different ways, by i) conceptual/methodological approaches; ii) review papers; and iii) case studies.

  2. Late Holocene morphodynamics in the littoral zone of the Iwik Peninsula area (Banc d'Arguin — Mauritania)

    NASA Astrophysics Data System (ADS)

    Barusseau, J. P.; Certain, R.; Vernet, R.; Saliège, J. F.

    2010-09-01

    In the littoral zone of the Banc d'Arguin both littoral sedimentary units and man-made deposits (shell-middens) abound. They were formed during the Late Holocene after the final onset of the post-glacial transgression. Here, a geo-archaeological approach is used to study them. The geomorphological and sedimentological characteristics of the coastal features define two distinct coastal sedimentary units in the Iwik-Aouatil zone between an ancient shoreline which formed on the Tafaritian substratum ca 6.7-5.7 cal. ka BP and the present one: (i) very extensive sand flats and (ii) linear relief features, both covered by a thin veneer of anthropogenic Anadara senilis shell-middens. They developed under a stable sea-level regime. The sand flats expanded at variable rates throughout the period. The linear relief features represent beach barriers and coastal dunes which can be dated archaeologically thanks to the superimposed shell-middens, supplemented by 14C dating. Two series of linear sedimentary units are identified. First, a complex north-south system of dunes and hook-ended sand barriers developed from 4.8 to 4.1 cal. ka BP and, secondly, two regular and linear beach barriers developed between 3.7 and 3.3 cal. ka BP. Their morphological characteristics suggest that they were generated through littoral drift processes. Directional changes observed between the first and the second groups demonstrate that the wave refraction pattern was dramatically modified after the closure of the strait between the former Iwik Island and the land. A comparison with the nearby Jerf el Oustani coastal area in the Late Holocene shows that both sites shared similarities in depositional patterns but also differences in the chronology of the sedimentary units. Processes involved in the development of the linear units are indicative of the enhancement of both sand influx and longshore drift due to climatic change.

  3. Magnitude and variability of Holocene sediment accumulation in Santa Monica Bay, California

    USGS Publications Warehouse

    Sommerfield, C.K.; Lee, H.J.

    2003-01-01

    The spatial variability of Holocene (past 10,000 years) sediment accumulation in Santa Monica Bay (California) was examined to identify controls sediment trapping in a bathymetrically complex coastal embayment and to provide geologic context for the post-industrial sedimentary record and associated pollution gradients. Sediment chronologies based on downcore AMS 14C dates were used to quantify long-term (millennia) accumulation rates in an effort to elucidate particle-transport pathways and sinks. Sediment accumulation rates for the full range of bayfloor environments (50-630 m water depths) range from 22 to 102 mg/cm2/year (15-88 mm/100 year), have an overall mean of 51??21 mg/cm2/year (1??, n=11), and are comparable to rates reported for adjacent borderland basins. Maximal accumulation rates on the Malibu shelf and within a reentrant to Redondo canyon are interpreted to reflect (1) proximity to sediment sources and (2) localized oceanographic and topographic conditions conducive to sediment trapping and deposition. The 14C-derived accumulation rates are 2-10 times lower than rates determined through 210Pb geochronology for the same sites in a related study, revealing that Holocene sediment accumulation has been non-steady-state. Santa Monica Bay is an important sink for suspended matter; averaged over the past several millennia a mass of sediment equivalent to 10-80% of the modern annual river supply is sequestered yearly. Net influx of suspended matter derived from the adjacent Palos Verdes shelf is evinced by a concentration gradient of p,p???-DDE in bayfloor sediments, whereas the distribution of anthropogenic silver suggests transport from Santa Monica shelf to the southeastern boundary of the bay. The results of this study provide new insight to the long-term fates of particulate matter in Los Angeles coastal waters. ?? 2003 Elsevier Science Ltd. All rights reserved.

  4. Outlet glaciers of southeast Greenland: rapid, synchronised regional retreat at the start of the Holocene?

    NASA Astrophysics Data System (ADS)

    Dyke, L. M.; Hughes, A. L.; Murray, T.; Ródes

    2012-12-01

    We report new in-situ cosmogenic isotope (10Be) exposure dates from two major fjord systems in southeast (SE) Greenland. Low elevation erratic pairs from Kangerdlugssuaq Fjord reveal the onset of coastal deglaciation at ~11 ky BP. Overlapping exposure ages from a fjord axis transect show this was followed by a period of rapid deglaciation to a position at least 50 km from the mouth. The rapid deglaciation of Kangerdlugssuaq Fjord taken together with similar dates from Sermilik Fjord situated ~350 km southwards (Hughes et al., 2012), shows synchronous coastal deglaciation. This regional synchronicity implies a common regional driving mechanism. Ice sheet retreat from the continental shelf was underway by 15 ky BP, probably in response to long term climate amelioration following the Last Glacial Maximum (LGM). We suggest that the 'fjord phase' of deglaciation occurred rapidly due to significant climatic amelioration and changing oceanic conditions at the end of the Younger Dryas stadial. To test the synchronicity of regional deglaciation further, we will report exposure ages and retreat rates from Bernstorffs Isfjord, 650 km south of Kangerdlugssuaq and 300 km south of Sermilik Fjord. Bathymetric data and geomorphological evidence from Bernstorffs Isfjord hint at a still-stand or re-advance during the Holocene: exposure dates will be used to test this hypothesis. Widespread changes have been reported in the marine terminating glaciers of the southeast sector of the Greenland Ice Sheet (GrIS) during the early 2000s. Our results show retreat rates that are either significantly faster or persist for much longer than those observed recently, and demonstrate the great sensitivity of these marine-terminating glaciers to climatic change. References: Hughes, A.L.C., Rainsley, E., Murray T., Fogwill, C.J., Schnabel, C. and Xu, S. (2012) Rapid response of Helheim Glacier, southeast Greenland, to early Holocene climate warming. Geology, 40, 427-430.

  5. Potential and limits of luminescence dating for establishing late-Holocene cyclone and tsunami chronologies

    NASA Astrophysics Data System (ADS)

    Brill, Dominik; May, Simon Matthias; Jankaew, Kruawun; Engel, Max; Brückner, Helmut

    2014-05-01

    Long-term recurrence intervals of coastal hazards such as tropical cyclones and tsunamis can be reconstructed on the basis of geological evidence of prehistoric events. These geological records have the potential to extend the period under observation beyond historical time scales. In addition to radiocarbon datings, optically stimulated luminescence (OSL) dating is used for the establishment of late-Holocene event chronologies. Here we discuss the potential and limits of applying OSL to sandy storm and tsunami deposits based on case studies from SW Thailand and NW Australia, where quartz luminescence properties (i.e., high sensitivity, thermally stable signal components dominated by the easily bleachable fast component, no mineralogical impurities) are favourable. Potential uncertainties and age offsets due to (i) incomplete signal resetting and (ii) spatial and temporal variations of dose rates that are supposed to be characteristic for deposits of coastal flooding events are evaluated. Incomplete bleaching of the OSL signal is evident in most deposits but can be corrected by statistical analysis of small aliquots or single grains using the minimum age model. Although the dating of modern analogues such as deposits from the 2004 Indian Ocean Tsunami revealed residuals, these uncertainties are insignificant compared to the respective local recurrence intervals. Further potential uncertainties arise from the complex coastal stratigraphies recording tsunami and cyclone deposits, such as variations between peat layers and sand sheets as well as differing concentrations of heavy minerals, but are comparably small if the geometry of different strata is adequately addressed. In contrast, errors introduced by temporal variations of environmental radiation fields may be much more significant. Especially changing water contents or radioactive disequilibria due to element mobility in marine carbonates are frequent in coastal settings and may lead to large uncertainties

  6. Rapid anthropogenic response to short-term aeolian-fluvial palaeoenvironmental changes during the Late Pleistocene-Holocene transition in the northern Negev Desert, Israel

    NASA Astrophysics Data System (ADS)

    Roskin, Joel; Katra, Itzhak; Agha, Nuha; Goring-Morris, A. Nigel; Porat, Naomi; Barzilai, Omry

    2014-09-01

    Archaeological investigations along Nahal Sekher on the eastern edge of Israel's northwestern Negev Desert dunefield revealed concentrations of Epipalaeolithic campsites associated respectively with ancient water bodies. This study, aimed at better understanding the connections between these camps and the water bodies, is concerned with a cluster of Natufian sites. A comprehensive geomorphological study integrating field mapping, stratigraphic sections, sedimentological analysis and optically stimulated luminescence (OSL) ages was conducted in the vicinity of a recently excavated Natufian campsite of Nahal Sekher VI whose artifacts directly overlay aeolian sand dated by OSL to 12.4 ± 0.7 and 11.7 ± 0.5 ka. Residual sequences of diagnostic silty sediments, defined here as low-energy fluvial fine-grained deposits (LFFDs), were identified within the drainage system of central Nahal Sekher around the Nahal Sekher VI site. LFFD sections were found to represent both shoreline and mid-water deposits. The thicker mid-water LFFD deposits (15.7 ± 0.7-10.7 ± 0.5 ka) date within the range of the Epipalaeolithic campsites, while the upper and shoreline LFFD units that thin out into the sands adjacent to the Nahal Sekher VI site display slightly younger ages (10.8 ± 0.4 ka-7.6 ± 0.4 ka). LFFD sedimentation by low-energy concentrated flow and standing-water developed as a result of proximal downstream dune-damming. These water bodies developed as a result of encroaching sand that initially crossed central Nahal Sekher by 15.7 ± 0.7 ka and probably intermittently blocked the course of the wadi. LFFD deposition was therefore a response to a unique combination of regional sand supply due to frequent powerful winds and does not represent climate change in the form of increased precipitation or temperature change. The chronostratigraphies affiliate the Natufian sites to the adjacent ancient water bodies. These relations reflect a rapid, but temporary anthropogenic response to a

  7. Alder Expansion as a Coastal Warming Signal - Linking Coastal Alaskan Carbon to Vegetation Change with Climate

    NASA Astrophysics Data System (ADS)

    Peteet, D. M.; Nichols, J. E.; Moy, C. M.; McGeachy, A.

    2014-12-01

    Corser Bog (60.5296364oN, 145.453858oW), 21 km east of Cordova, AK is a sphagnum-dominated peatland 42 m asl. adjacent to Sheridan Glacier and the Copper River Delta. Deglaciation at 11.5 ka began with shallow pond deposition, reflecting regional warmth with the pioneers Alnus crispa subsp. sinuata, Salix, and ferns colonizing the fresh, mineral soils on the landscape. Continued early Holocene warming/melting of glaciers led to the foundation species Alnus dominance and peatland formation, surrounded by shrubs such as Rubus spectabilis, Sambucus racemosa, and wetland species such as Myrica gale and Potentilla palustris. As Sphagnum peat accumulated, the highest rates of carbon accumulation for a few centuries are represented at 50 g/m2/a, similar to short-term very high rates in the early Holocene throughout the circumboreal region but varying within the early Holocene due to development of local wet, bryophytic environments. A shift to sedge peat regionally along the South-Central Alaskan coast 7.6 - 3.7 ka is paralleled by a more evaporative, drier climate with Rhododendron groenlandicum presence, lower carbon accumulation (13 g/m2/a), and minimal macrofossil preservation, which is paralleled regionally in coastal muskegs both to the northwest and southeast and by a hiatus in a nearby lake record. A cooler, moister climate is evident in Corser Bog with the shift to Sphagnum peat at 3.7 ka, regional shifts from sedge to Sphagnum peat throughout the entire coastline from Yakutat to Girdwood, AK and the demonstration of glacial advances in the region. Alnus pollen markedly increases to 60% in the uppermost sample, indicative of a major signal for glacial recession in this region.

  8. The importance of radiocarbon dates and tephra for developing chronologies of Holocene environmental changes from lake sediments, North Far East

    DOE PAGES

    Lozhkin, Anatoly V.; Brown, Thomas A.; Anderson, Patricia M.; ...

    2016-08-12

    One problem with developing continuous chronologies of paleoenvironmental change in northern areas of the Far East using 14C is the low organic content in lake sediments. However, Holocene age-models can be supplemented by widespread tephra deposits reported in the Magadan region. The best documented of these tephras has been correlated to the KO tephra from southern Kamchatka dated to 7600 BP. Though a key chronostratigraphic marker, no detailed compendium of the distribution of this tephra and its associated 14C dates has been available from sites in the northern Far East. We provide such a summary. Known locally as the Elikchanmore » tephra, lake cores indicate an ash fall that extended ~1800 km north of the Kamchatkan caldera with a ~500 km wide trajectory in the Magadan region. Other Holocene tephras preserved in lake sediments have poorer age control and possibly date to ~2500 BP, ~2700 BP and ~6000 BP. These ashes seem to be restricted to coastal or near-coastal sites. Finally, a single record of a ~25,000 BP tephra has also been documented ~100 km to the northeast of Magadan.« less

  9. The importance of radiocarbon dates and tephra for developing chronologies of Holocene environmental changes from lake sediments, North Far East

    SciTech Connect

    Lozhkin, Anatoly V.; Brown, Thomas A.; Anderson, Patricia M.; Glushkova, Olga Yu; Melekestsev, Ivan V.

    2016-08-12

    One problem with developing continuous chronologies of paleoenvironmental change in northern areas of the Far East using 14C is the low organic content in lake sediments. However, Holocene age-models can be supplemented by widespread tephra deposits reported in the Magadan region. The best documented of these tephras has been correlated to the KO tephra from southern Kamchatka dated to 7600 BP. Though a key chronostratigraphic marker, no detailed compendium of the distribution of this tephra and its associated 14C dates has been available from sites in the northern Far East. We provide such a summary. Known locally as the Elikchan tephra, lake cores indicate an ash fall that extended ~1800 km north of the Kamchatkan caldera with a ~500 km wide trajectory in the Magadan region. Other Holocene tephras preserved in lake sediments have poorer age control and possibly date to ~2500 BP, ~2700 BP and ~6000 BP. These ashes seem to be restricted to coastal or near-coastal sites. Finally, a single record of a ~25,000 BP tephra has also been documented ~100 km to the northeast of Magadan.

  10. The importance of radiocarbon dates and tephra for developing chronologies of Holocene environmental changes from lake sediments, North Far East

    SciTech Connect

    Lozhkin, Anatoly V.; Brown, Thomas A.; Anderson, Patricia M.; Glushkova, Olga Yu; Melekestsev, Ivan V.

    2016-08-12

    One problem with developing continuous chronologies of paleoenvironmental change in northern areas of the Far East using 14C is the low organic content in lake sediments. However, Holocene age-models can be supplemented by widespread tephra deposits reported in the Magadan region. The best documented of these tephras has been correlated to the KO tephra from southern Kamchatka dated to 7600 BP. Though a key chronostratigraphic marker, no detailed compendium of the distribution of this tephra and its associated 14C dates has been available from sites in the northern Far East. We provide such a summary. Known locally as the Elikchan tephra, lake cores indicate an ash fall that extended ~1800 km north of the Kamchatkan caldera with a ~500 km wide trajectory in the Magadan region. Other Holocene tephras preserved in lake sediments have poorer age control and possibly date to ~2500 BP, ~2700 BP and ~6000 BP. These ashes seem to be restricted to coastal or near-coastal sites. Finally, a single record of a ~25,000 BP tephra has also been documented ~100 km to the northeast of Magadan.

  11. Subsidence along the Atlantic Coast of the United States: Insights from GPS and late Holocene relative sea level data

    NASA Astrophysics Data System (ADS)

    A Karegar, M.; Engelhart, S. E.; Dixon, T. H.

    2015-12-01

    Subsidence along the Atlantic coast of the United States is the largest amplitude collapse of a pro-glacial forebulge on Earth. High-quality geological records of late Holocene Relative Sea Level (RSL) are now available for this region. These data provide an independent constraint on Glacial Isostatic Adjustments (GIA), for comparison to continuous GPS measurements that directly measure net vertical crustal motion from GIA and other processes. Installation of more than 130 permanent GPS stations since 2006 represents an improvement towards precise determination of present-day subsidence rates along the coastal plain. We present an improved vertical velocity field for the eastern seaboard of the U.S. and parts of Atlantic Canada with uncertainty estimates that incorporate time-correlated noise. We use the geologic rates of RSL as an independent constraint to separate the long-term GIA-induced displacement (average motion over past 4 ka) from the GPS vertical displacement (average of one or two decades). Differences between the two are important for mitigating coastal land loss and predicting future storm surge inundation. Our results indicate that for most areas of the U.S. eastern seaboard there is no difference between GPS rates and late Holocene RSL rates. Exceptions are related to areas of recent excessive groundwater extraction in Virginia and South Carolina. The present-day subsidence rates in these areas are approximately double the long-term geologic rates.

  12. Central Greenland Holocene Deuterium Excess Variability

    NASA Astrophysics Data System (ADS)

    Masson-Delmotte, V.; Jouzel, J.; Falourd, S.; Cattani, O.; Dahl-Jensen, D.; Johnsen, S.; Sveinbjornsdottir, A. E.; White, J. W. C.

    Water stable isotopes (oxygen 18 and deuterium) have been measured along the Holocene part of two deep ice cores from central Greenland, GRIP and North GRIP. Theoretical studies have shown that the second-order isotopic parameter, the deu- terium excess (d=dD-8d18O), is an indicator of climatic changes at the oceanic mois- ture source reflecting at least partly changes in sea-surface-temperature. The two deu- terium excess records from GRIP and North GRIP show a long term increasing trend already observed in Antarctic deep ice cores and related to changes in the Earth's obliquity during the Holocene : an decreased obliquity is associated with a larger low to high latitude annual mean insolation gradient, warmer tropics, colder poles, and a more intense atmospheric transport from the tropics to the poles, resulting in a higher moisture source temperature and higher deuterium excess values. Superimposed onto this long term trend, central Greenland deuterium excess records also exhibit small abrupt events (8.2 ka BP and 4.5 ka BP) and a high frequency variability.

  13. Sea level changes in the holocene

    NASA Astrophysics Data System (ADS)

    Kidson, C.

    Over the last 30 years the emphasis in studies of the recovery from low last glaciation sea levels has changed significantly. The search for a eustatic sea level curve having global relevance has ended. Studies into the rheology of the earth's crust, and recognition that the geoid has not remained stable over time, have resulted in the recognition that there must have been regional differences in eustatic response to deglaciation. As a part of this re-appraisal there has been a growing appreciation that crustal isostatic response to the removal of the weight of ice sheets has been accompanied by a consequential hydro-isostatic response, particularly in the areas of the shelf seas. In the later part of the post-war period attention has additionally been focussed on the much greater potential for error over the whole field of palaeoenvironmental reconstruction in the Holocene, including not only errors in dating, but also a large number of possible sources of errors in heighting. As a result of this, an increasing number of scientists are withholding judgement on the nature of sea level rise and, more particularly, on the problem of higher than present late Holocene eustatic sea levels. The problems outstanding in the early 1960s have not yet been resolved but the bases of uncertainty have changed.

  14. Mid to late Holocene environmental changes along the coast of western Sardinia (Mediterranean Sea)

    NASA Astrophysics Data System (ADS)

    Melis, Rita T.; Depalmas, Anna; Di Rita, Federico; Montis, Francesca; Vacchi, Matteo

    2017-08-01

    Multiproxy analysis composed of biostratigraphy and pollen analysis allowed reconstructing the palaeoecological and palaeoenvironmental evolution of the Tirso river coastal plain in Sardinia (NW Mediterranean) in the last 6 millennia. We demonstrated that interplay between littoral and fluvial processes have significantly controlled the environmental evolution of the area and have played a key role in the pattern of historical and prehistorical settlements of this wide portion of western Sardinian coastline. At the end of Neolithic period (ca. 6.0 to 5.5 cal. ka BP) the area close to the shoreline was most likely characterized by large coastal lagoons intermittently connected to the open sea. Such saltwater influence is corroborated by faunal and pollen assemblages found in the landward portion of the Tirso coastal plain up to 2 km inland from the modern shoreline. Our data robustly document the end of the transgressive trend at ca. 5.5 cal. ka BP, and a dominant fluvial sedimentation since Final Neolithic period. At this time, a progradational trend started, causing the seaward migration of shoreline and, consequently, of the barrier-lagoon system. The major landscape modification tracked along the last 6 millennia may also explain the low density of historical and prehistorical remains in the Tirso coastal plain, especially if compared to the nearby rocky area of Sinis Peninsula densely inhabited since the Neolithic. Our data further provide new insights into the Relative Sea Level (RSL) evolution in this sector of the Mediterranean. In particular, we improved the mid-Holocene RSL record in Sardinia, where only scarce data were previously available.

  15. Late Holocene sea level changes along the coast of Southwestern Turkey

    NASA Astrophysics Data System (ADS)

    Kızıldaǧ, Nilhan; Özdaş, Harun; Özel, Erdeniz

    2014-05-01

    A multi-disciplinary survey has been performed along the coast of southwestern Turkey in order to determine relative sea level changes during the Late Holocene. Especially, the submergence of harbour structures of the ancient coastal settlements provides noticeable evidence for eustatic sea level rise and/or tectonic subsidence. In addition, the traces of bioerosion produced by some organisms along the limestone coasts formed at mean sea level position represent a remarkable data of paleoshorelines. These traces can be found below the current sea level nowadays due to relative sea level rise. Both archaeological and biological data provide an important source on the amount and period of relative sea level rise along the coasts of southwestern Turkey-southeastern Aegean Sea. This region is under the influence of active tectonism as a result of the collision of the Arab-African and Eurasian plates. Thus, a large number of earthquakes have occurred in this zone which must have been an impact on submergence of ancient harbour structures and geomorphological formations. This area is located very important zone in terms of being tectonically active, having a large number of ancient coastal settlements, and consisting of limestone lithology. A number of submerged archaeological structures and bioerosion formations have been investigated by measuring the depths of remains with respect to the present sea level. By comparing the eustatic sea level change, current elevations and construction time of archaeological remains, which dated taking into account construction techniques and ceramic findings, we determine the amount of relative sea level change. In addition, numerous active faults have been detected by performing seismic survey. The results indicate that the vertical tectonic movement has much more effect on submergence of archaeological and geomorphological features than eustatic sea level rise. Uncovering the role of the tectonic movement and sea level changes on the

  16. Holocene environmental change of the northern Caribbean inferred from the sediments of a flooded sinkhole, Cayo Coco, Cuba

    NASA Astrophysics Data System (ADS)

    Peros, M. C.; Agosta G'meiner, A. M.; Collins, S.

    2016-12-01

    We present new data on the Holocene environments of the northern Caribbean inferred from the sediments of a flooded sinkhole (Cenote Jennifer) on the island of Cayo Coco in north-central Cuba. Cenote Jennifer is located several meters above sea level and has an average depth of 13 meters. Water chemistry measurements indicate that the water in the sinkhole is highly stratified with a halocline at about 8 meters depth and an anoxic base. A series of sediment cores collected at the center of the sinkhole were analyzed for fossil pollen, microcharcoal, dinoflagellate cysts, elemental geochemistry (by high-resolution XRF core-scanning), and grain size and were dated by Pb-210 and AMS radiocarbon techniques (using well-preserved macrofossils of leaves, bark, and twigs). The results show that sediments first began to accumulate in Cenote Jennifer approximately 9000 years ago and continued until the present. The elemental geochemistry results record increases in elements such as Br, Cl, Ni, and Cu during the 8.2 kyr event which may reflect enhanced deep-ocean upwelling at this time. The fossil pollen data record a succession in vegetation that included cattail marsh, thorny coastal scrubland, dry evergreen forest, and secondary forest communities over the course of the Holocene. Changes in vegetation were driven mostly by relative sea level rise in the early Holocene but climate change was more important by the middle to late Holocene. Hundreds of mm- to cm-scale laminations are also present in the core, many of which represent past hurricane strikes. The microcharcoal and pollen evidence also suggests that prehistoric humans may have settled the area and practiced agriculture as early as 2800 cal yr BP. The findings from Cenote Jennifer highlight the utility of flooded sinkholes as paleoenvironmental archives in tropical kart regions and provide important new data on the hydroclimatology of the northern Caribbean.

  17. Relationship between geohydrology and Upper Pleistocene-Holocene evolution of the eastern region of the Province of Buenos Aires, Argentina

    NASA Astrophysics Data System (ADS)

    Capítulo, Leandro Rodrigues; Kruse, Eduardo E.

    2017-07-01

    The Upper Pleistocene-Holocene geological evolution, which is characterized by its landscape-forming energy and is related to geological and geomorphological complexity, has an impact on the groundwater dynamics of coastal aquifers. The geological configuration of a sector of the east coast of the Province of Buenos Aires was analyzed, as well as its connection with the geological and geomorphological history of the region during the Late Pleistocene and Holocene, and its influence on the regional and local geohydrological behaviour. This analysis was based on the application of the concept of hydrofacies. Boreholes were drilled and sampled (with depths of up to 40 m), and vertical electrical sounding, electrical tomography and pumping tests were undertaken. The description of the cutting samples by means of a stereo microscope, the interpretation of satellite images, and the construction of lithological and hydrogeological profiles and flow charts were carried out in the laboratory, and then integrated in a GIS. The identification of the lithological units and their distribution in the area allowed the construction of an evolutionary geological model for the Late Pleistocene and Holocene. Three aquifer units can be recognized: one of Late Pleistocene age (hydrofacies E) and the other two of Holocene age (hydrofacies A and C); their hydraulic connection depends on the occurrence and thickness variation of the aquitard units (hydrofacies B and D). The approach adopted allows the examination of the possibilities for groundwater exploitation and constitutes an applied conceptual framework to be taken into consideration when developing conceptual and numerical models at the local and regional scales.

  18. Past circulation along the western Iberian margin: a time slice vision from the Last Glacial to the Holocene

    NASA Astrophysics Data System (ADS)

    Salgueiro, E.; Naughton, F.; Voelker, A. H. L.; de Abreu, L.; Alberto, A.; Rossignol, L.; Duprat, J.; Magalhães, V. H.; Vaqueiro, S.; Turon, J.-L.; Abrantes, F.

    2014-12-01

    Fifteen Iberian margin sediment cores, distributed between 43°12‧N and 35°53‧N, have been used to reconstruct spatial and temporal (sub)surface circulation along the Iberian margin since the Last Glacial period. Time-slice maps of planktonic foraminiferal derived summer sea surface temperature (SST) and export productivity (Pexp) were established for specific time intervals within the last 35 ky: the Holocene (Recent and last 8 ky), Younger Dryas (YD), Heinrich Stadials (HS) 1, 2a, 2b, 3, and the Last Glacial Maximum (LGM). The SST during the Holocene shows the same latitudinal gradient along the western Iberian margin as present-day with cold but productive areas that reflect the influence of coastal upwelling centers. The LGM appears as a slightly less warm, but more productive period relative to the Holocene and present-day conditions, suggesting that sea-level minima forced a westward displacement of the coastal upwelling centers possibly accompanied by a strengthening of northward winds. During the YD, a longitudinal thermal front is depicted at 10°W, with cold polar waters offshore and warmer subtropical waters inshore, suggesting that the subtropical Paleo-Iberian Poleward Current more likely flowed at a more inshore location masking the local SST signal and amplitude of variation. A substantial cooling and drop in productivity is observed during all HS, in particular HS1 and HS3, reflecting the penetration of icebergs-derived meltwater. These most extreme southward extensions of very cold waters define a strong SST gradient that marks a possible Paleo-Azores Front. Higher production south of this front was likely fed by frontal nutrient advection.

  19. Multiproxy Reduced-Dimension Reconstruction of Holocene Tropical Pacific SST Fields and Indian Monsoon Variability

    NASA Astrophysics Data System (ADS)

    Gill, E.; Rajagopalan, B.; Molnar, P. H.; Marchitto, T. M., Jr.; Kushnir, Y.

    2016-12-01

    We develop a multiproxy reduced-dimension methodology that blends magnesium calcium (Mg/Ca) and alkenone (UK'37) paleo sea surface temperature (SST) records from the eastern and western equatorial Pacific to recreate snapshots of full field SSTs and zonal wind anomalies from 10 to 2 ka BP in 2000-year increments. In the reconstruction, the zonal SST difference (average west Pacific SST minus average east Pacific SST) is largest at 10 ka (0.26°C), with coldest SST anomalies of -0.9°C in the eastern equatorial Pacific and concurrent easterly maximum zonal wind anomalies of 7 m s-1 throughout the central Pacific. From 10 to 2 ka, the entire equatorial Pacific warms, but at a faster rate in the east than in the west. These patterns are broadly consistent with previous inferences of reduced El Niño-Southern Oscillation variability associated with a cooler and/or "La Niña-like" state during the early to middle Holocene. At present there is a strong negative correlation between tropical pacific SSTs and Indian summer monsoon strength. Assuming ENSO-monsoon teleconnections were the same during early Holocene, we would expect a cooler tropical Pacific to enhance the summer Indian monsoon. To test this idea, we used the same tropical Pacific SST proxy records and a similar reduced-dimension technique to reconstruct fields of Arabian Sea wind-stress curl and Indian summer monsoon precipitation. Reconstructions for 10 ka reveal wind-stress curl anomalies of 30% greater than present day off the coastlines of Oman and Yemen, which suggest greater coastal upwelling and an enhanced monsoon jet during this time. Spatial rainfall reconstructions reveal the greatest difference in precipitation at 10 ka over the core monsoon region ( 20-60% greater than present day). Specifically, reconstructions from 10 ka reveal 40-60% greater rainfall over North West India, a region home to abundant paleo-lake records spanning the Holocene but is at present remarkably dry ( 200-450 mm of annual

  20. Reconstruction of late Holocene flooding events in the Gulf of Genoa, Ligurian Sea

    NASA Astrophysics Data System (ADS)

    Lamy, Frank; Kaiser, Jerome; Arz, Helge; Ruggieri, Nicoletta

    2014-05-01

    The area of the Gulf of Genoa contains a large potential for studying past rainfall variability as it is one of the major Mediterranean centers for cyclogenesis. The strongest depressions form when cold arctic/subarctic air outbreaks flow through the Rhone valley into the Gulf of Lions and the Ligurian Sea during late autumn when sea surface temperatures are still relatively high. The cyclones are more frequent during negative Arctic Oscillation / North Atlantic Oscillation (AO/NAO). As well, significant negative correlations exist between AO/NAO and winter/spring precipitation and river discharge in northwestern Italy. Related autumn flooding events occur at interannual time-scales and may cause substantial damage in the region. Moreover, the "Genoa Cyclones" sometimes move northeastwards into eastern/central Europe (the so-called "Vb" cyclone track) and contributed for example substantially to the Elbe flooding in 2002. During R/V Poseidon cruise P413 (May 2011), ca. 60 sediment cores were taken along the Ligurian shelf, continental slope and in the basin between off Livorno and the French border. Coring profiles from the coastal area to the deep basin allow reconstructing past environmental variability over the last ca. 90000 years with sedimentation rates varying between ca. 0.5 cm*yr-1 for the latest Holocene to ca. 10 cm*kyr-1 for the last glacial. On the shelf, mud lenses with exceptionally high sedimentation rates reaching several m/kyr provide detailed Holocene records of changes in terrigenous sediment input primarily related to autumn rainfall events. We performed high resolution (mm) analyses of major elements using XRF core-scanning on two cores with extremely high resolution (0.2-0.4 cm/year) over the last 2.5 kyr BP. Typical elements of detrital origin (i.e. Ti, Fe) present a very high variability, probably related to flooding events during the late Holocene. Spectral analysis on these records reveals significant periodicities around 4-5 and 7

  1. Late Holocene Russian Arctic climate variability - spatial and seasonal aspects inferred from glacier and ground ice

    NASA Astrophysics Data System (ADS)

    Opel, T.; Meyer, H.; Fritzsche, D.; Laepple, T.; Alexander, D.

    2014-12-01

    The Arctic currently experiences an unprecedented warming. This dynamic response to changes in climate forcing as well as corresponding feedbacks as sea ice retreat make the Arctic a key region to study past and future climate changes. Recent Arctic-wide temperature reconstructions indicate a long-term cooling prior to the ongoing warming. However, they are based mostly on proxies that record summer information and hence are assumed to be seasonally biased towards the summer. Moreover, the Russian Arctic is significantly underrepresented in these Arctic-wide reconstructions. Here we present glacier and ground ice records from Northern Siberia that provide valuable information for a better spatial and seasonal understanding of Holocene climate variability in the Arctic. The high-resolution Akademii Nauk δ18O ice core record (Severnaya Zemlya) proves the Late Holocene cooling and the pronounced warming after 1800. It shows neither a prominent Medieval Climate Anomaly nor a Little Ice Age but gives evidence of several abrupt warming and cooling events during the last centuries, also found in ice-core records from Svalbard and Franz Josef Land. They may be related to the regional internal climate variability, i.e. atmosphere-sea ice feedbacks in the Barents and Kara seas region. Ice wedges were studied at several study sites in the Lena River Delta and the coastal permafrost lowlands of the Laptev Sea region. They are formed by the repeated filling of wintertime thermal contraction cracks by snow melt water in spring. Radiocarbon dating of organic matter enables the generation of centennial scale δ18O records that are indicative of temperatures in the cold period of the year (winter and spring). Our ice wedge records show general increasing δ18O trends over the Mid and Late Holocene and an unprecedented recent warming. Both may be related to the changes in orbital forcing during the cold season as well as in greenhouse gas concentrations over the last millennia

  2. Optical dating of late Holocene storm surges from Schokland (Noordoostpolder, the Netherlands)

    NASA Astrophysics Data System (ADS)

    van den Biggelaar, Don; Kluiving, Sjoerd; van Balen, Roland; Kasse, Cronelils; Troelstra, Simon; Prins, Maarten; Wallinga, Jakob; Versendaal, Alice

    2015-04-01

    Storm surges have a major impact on land use and human habitation in coastal regions. Our understanding of this impact can be improved by correlating long-term historical storm records with sedimentary evidence of storm surges, but so far few studies use such an approach. Here we present detailed geological and historical data on late Holocene storm surges from the former island Schokland, located in the northern part of Flevoland (central Netherlands). During the late Holocene, Schokland transformed from a peat area that gradually inundated (~1200 yr ago) via an island in a marine environment (~400 yr ago) to a land-locked island in the reclaimed Province of Flevoland (~70 yr ago). Deposits formed between 1200 and 70 year ago on lower parts of the island, consist of a stacked sequence of clay and sand layers, with the latter being deposited during storm surges. We dated the sandy laminae of late Holocene storm surges in the clay deposit on Schokland to improve the age model of the island's flooding history during the last 1200 years. Samples for dating were obtained from a mechanical core at Schokland. The top of the peat underlying the clay and sand deposits was dated using 14C accelerator mass spectrometry (AMS) of terrestrial plant and seed material. Sandy intervals of the flood deposits were dated using a series of ten quartz OSL ages, which were obtained using state-of-the-art methods to deal with incomplete resetting of the OSL signal. These new dates, together with laboratory analyses on the clay deposit (thermogravimetric analysis, grain-size analyses, foraminifera, bivalves and ostracods) and a literature study show that storm surges had a major impact on both the sedimentary and the anthropogenic history of Schokland. The results show that the stacked clay sequence is younger than expected, indicating either an increasing sedimentation rate or reworking of the clay by storm surges. Furthermore, the results indicate that a correlation can be made between

  3. Holocene floodplain evolution in the Shiribeshi-Toshibetsu River lowland, northern Japan

    NASA Astrophysics Data System (ADS)

    Ishii, Yuji

    2017-09-01

    The influence of sea-level and climate changes on the evolution of coastal floodplains is an important problem in fluvial geomorphology and geology. However, few studies have constructed detailed chronologies of floodplain evolution, and the influence of sea-level and climate changes at submillennial time scales is not clear. This study investigated the Holocene evolution of the floodplain in the Shiribeshi-Toshibetsu River lowland, Hokkaido, northern Japan, based on 13 auger cores, 15 radiocarbon ages, and 2 cross sections made using existing columnar sections. In the study area, peat beds 3-6 m thick in the uppermost Holocene sediments are underlain by fluvial sediment that mainly consists of sand beds resulting from crevassing or progradational avulsion. Age-elevation plots of the bases of these peat beds suggest that fluvial aggradation was continuous until peat formation began, which in turn suggests that peat beds began to form with the cessation of fluvial deposition. The chronology of floodplain sediments based on radiocarbon ages indicates that peatlands began to develop locally before ca. 6500 cal BP and became moderately widespread before 5600 cal BP. Peatlands then became more extensive after two periods of rapid expansion during ca. 5300-5000 and 4100-3900 cal BP. Comparison with sea-level and regional climate changes suggests that the initiation of these peat beds before 5600 cal BP was associated with the deceleration of sea-level rise at ca. 7000 cal BP. The two later periods of peatland expansion may have been strongly influenced by reduced fluvial activity due to decreased precipitation from a weakened East Asian summer monsoon. This interpretation suggests that floodplain evolution was controlled by sea-level and climate changes and that the response to climate change occurred at submillennial time scales. A comparison with the Ishikari lowland on Hokkaido showed that the two floodplains have slightly different histories, possibly because of

  4. Holocene vegetation, environment and anthropogenic influence in the Fuzhou Basin, southeast China

    NASA Astrophysics Data System (ADS)

    Yue, Yuanfu; Zheng, Zhuo; Rolett, Barry V.; Ma, Ting; Chen, Cong; Huang, Kangyou; Lin, Gongwu; Zhu, Guangqi; Cheddadi, Rachid

    2015-03-01

    A ∼40 m sediment core (FZ4) was collected from the Fuzhou Basin, near the lower reaches of the Min River, in Fujian Province on the southeast coast of China. The sediment and pollen record contributes to our understanding of Holocene paleogeography, including local changes in vegetation and climate in the context of Neolithic cultural developments. The sediment record reveals a fluvial environment in the Fuzhou Basin during the late Pleistocene, and it demonstrates that a change from fluvial to estuarine conditions at ∼9000 cal yr BP resulted from postglacial sea level rise. Evidence of abundant marine diatoms and tidal flat laminations observed in the FZ4 sediments, implies that the Fuzhou Basin was under marine influence between ∼9000 and ∼2000 cal yr BP. After 2000 cal yr BP, a rapid retreat in coastline associated with fluvial aggradation and coastal progradation produced more shallow water for wetlands and initiated formation of the floodplain landscape. The pollen record reveals the presence of a dense subtropical forest between ca. 9000 and 7000 cal yr BP, representing the Holocene thermal maximum, which is linked with rising sea level and marine transgression in the Fuzhou Basin. Between ca. 5500 and 2000 cal yr BP, the thermophilous forest dominated by Castanopsis retreated and coniferous forest expanded, reflecting moderate climatic cooling during this period. Timing of the high frequencies for Pinus and ferns correspond with the mid-late Holocene cooling trend recorded in local mountain peatland and coastal regions of the lower Yangtze and Hanjiang deltas. Anthropogenically induced land cover change was negligible prior to the Tanshishan cultural period, which marks the beginning of Neolithic era sedentary village life on the Fujian coast around 5500 BP. The pollen transition at ca. 3000-1500 cal yr BP, distinguished by rising frequencies of Poaceae and taxa (including Cyperaceae and Artemisia) closely associated with agricultural land cover

  5. Reconstructing the Holocene depositional environments along the northern coast of Sfax (Tunisia): Mineralogical and sedimentological approaches

    NASA Astrophysics Data System (ADS)

    Lamourou, Ali; Touir, Jamel; Fagel, Nathalie

    2017-05-01

    A sedimentological and mineralogical study of sedimentary cores allowed reconstructing the evolution of depositional environments along the Northern coast of Sfax (Tunisia). The aim of this research work is to identify the factors controlling the sedimentation from the Holocene to the Present time. Three 30-m sediment cores collected by drilling at 30 m water depth were analyzed for their color, magnetic susceptibility signal, grain size by laser diffraction, organic matter content by loss of ignition, carbonate content by calcimetry and mineralogy by X-ray diffraction on bulk powder and clay <2 μm. They broadly present the same sedimentological and mineralogical features. Microscopical observations of petrographic slides allowed identifying six main sedimentary facies. Bulk mineralogical assemblages comprised clay minerals, quartz, calcite, gypsum and K-feldspars were examined. Considerable change was observed in the carbonate content that mimicked the bioclaste abundance and diluted the detrital minerals (clay minerals, quartz and feldspars). The gypsum mainly occurred in the lower sedimentary columns (SC12 and SC9) and in the upper/middle of core SC6. The clay fraction was made of a mixture of kaolinite, illite, smectite and palygorskite with no clear variation through core depth. Both grain-size parameters and magnetic susceptibility profile showed a sharp transition in the upper 2-5 m of the sedimentological columns. Coarse, sandy to gravely sediments characterized by a low magnetic susceptibility signal were replaced by fine bioclastic-rich clayey sediments. The analysis of vertical succession of depositional facies revealed a fluvial depositional environment (coastal plain) basically marked by fluvial channels and inundation plains at the bottom of all cores. However, core-top sediments recorded a littoral marine environment with sand depositions rich in gastropods, lamellibranches and algæ. Depositional facies, sedimentological and mineralogical

  6. New constraints on late Holocene eustatic sea-level changes from Mahé, Seychelles

    NASA Astrophysics Data System (ADS)

    Woodroffe, Sarah A.; Long, Antony J.; Milne, Glenn A.; Bryant, Charlotte L.; Thomas, Alexander L.

    2015-05-01

    This study provides new estimates of globally integrated ice sheet melt during the late Holocene (since 4 ka BP) from Seychelles in the western Indian Ocean, a tectonically stable, far field location where the necessary Glacial-Isostatic Adjustment (GIA) correction is small and is relatively insensitive to predictions using different Earth viscosity profiles. We compare sea level data from Seychelles to estimates of eustasy from two GIA models, ICE-5G and EUST3, which represent end-members in the quantity of global melt during the late Holocene. We use data from a range of coastal environments including fringing reef, present day beaches, fossil plateau and mangrove deposits on the largest island of the Seychelles archipelago, Mahé to reconstruct relative sea-level changes. Our data suggest that extensive coastal deposits of carbonate-rich sands that fringe the west coast formed in the last 2 ka and the horizontal nature of their surface topography suggests RSL stability during this period. Mangrove sediments preserved behind these deposits and in river mouths date to c. 2 ka and indicate that RSL was between -2 m and present during this interval. Correcting the reconstructed sea level data using a suite of optimal GIA models based on the two ice models mentioned above and a large number (c. 350) of Earth viscosity models gives a result that is consistent with the sedimentological constraints. When uncertainties in both model results and data are considered, it is possible to rule out eustatic sea levels below c. 2 m and more than a few decimetres above present during the past two millennia. This uncertainty is dominated by error in the reconstructions rather than the model predictions. We note, however, that our estimates of eustasy are more compatible with the EUST3 model compared to the ICE-5G model during the late Holocene (2-1 ka BP). Our evidence from Seychelles shows that the timing of when eustatic sea level first rose close to present is between the

  7. Late Pleistocene-Holocene phytoplankton productivity in the Gulf of Alaska, IODP Site U1419

    NASA Astrophysics Data System (ADS)

    LeVay, L. J.; Romero, O. E.; McClymont, E.; Müller, J.; Penkrot, M. L.; Jaeger, J. M.; Mix, A.; Walczak, M.

    2016-12-01

    The modern Gulf of Alaska (GoA) is a high-nutrient, low-chlorophyll region that is iron-limited; however, the coastal region of Alaska is macronutrient-limited. Vertical mixing of these shallow coastal and deep basinal waters produce high seasonal productivity across the shelf. Previous studies on the Alaskan shelf showed that productivity varied across the Pleistocene-Holocene transition, likely related to climate and sea level change that brought nutrients from estuaries into the Gulf. Here we explore an extended record through the Late Pleistocene-Holocene to reconstruct the productivity of phytoplankton groups in the GoA and to understand the impact of glacial/interglacial climates on primary production and nutrient availability near the shelf. International Ocean Discovery Program (IODP) Site U1419 was cored during Expedition 341 on the upper continental slope in the GoA. A high-resolution sedimentary sequence was recovered that records Late Pleistocene-Holocene glacial and paleoceanographic dynamics. Both calcareous nannoplankton and diatoms are well-represented at Site U1419. Very few studies have explored the competition of these two phytoplankton groups in the geologic record. Because calcareous nannoplankton and diatoms favor differing nutrient conditions, changes in their abundance can aid in reconstructing shifts in primary productivity as well as the causes, such as stratification or nutrient limitation. We present a multi-proxy record, including the group and species abundance of diatoms and calcareous nannoplankton, biogenic bulk components content, alkenone-based sea surface temperatures, and XRF core scanning elemental composition, which is used to interpret fluctuations in phytoplankton and identify the underlying causes. Initial results show the group abundance of nannoplankton and diatoms fluctuates greatly and appears to covary. Calcareous nannoplankton abundance increases with sea surface temperature and is related to higher alkenone

  8. Constructing a High-Resolution Holocene Interpolar Methane Gradient

    NASA Astrophysics Data System (ADS)

    Sowers, Todd; Vladimirova, Diana; Blunier, Thomas

    2017-04-01

    The concentration of methane (CH4) in the northern hemisphere is elevated relative to the southern hemisphere primarily because of enhanced northern hemisphere CH4 emissions. During the preAnthropogenic era (prior to 1600AD) the interpolar CH4 gradient (IPG) is effectively dictated by the ratio of tropical to Pan Arctic CH4 emissions. IPG records from ice cores in Greenland and Antarctica therefore provide fundamental information for assessing the latitudinal distribution of CH4 emissions and their relation to global climate change. We recently constructed a high-resolution (100yr) record of IPG changes throughout the Holocene using the ReCAP (E. Greenland) and WAIS (W. Antarctica) ice cores. Contemporaneous samples from both cores were analyzed on the same day to minimize analytical uncertainties associated with IPG reconstructions. CH4 results from the WAIS core were indistinguishable from previous results suggesting our analytical scheme was intact (± 3ppb). Our reconstructed IPG showed early Holocene IPG values of ˜65ppb declining throughout the Holocene to values approximating ˜45 ppb during the latest portion of the Holocene (preAnthropogenic). Our results are consistent with the idea that early Holocene peatland development in the PanArctic regions followed glacier retreat near the end of the last glacial termination. These newly formed PanArctic peatlands contributed an additional 20Tg of CH4/yr during the Early Holocene relative to the late Holocene.

  9. Holocene climatic variations in the Western Cordillera of Colombia: A multiproxy high-resolution record unravels the dual influence of ENSO and ITCZ

    NASA Astrophysics Data System (ADS)

    Muñoz, Paula; Gorin, Georges; Parra, Norberto; Velásquez, Cesar; Lemus, Diego; Monsalve-M., Carlos; Jojoa, Marcela

    2017-01-01

    The Páramo de Frontino (3460 m elevation) in Colombia is located approximately halfway between the Pacific and Atlantic oceans. It contains a 17 kyr long, stratigraphically continuous sedimentary sequence dated by 30 AMS 14C ages. Our study covers the last 11,500 cal yr and focuses on the biotic (pollen) and abiotic (microfluorescence-X or μXRF) components of this high mountain ecosystem. The pollen record provides a proxy for temperature and humidity with a resolution of 20-35 yr, and μXRF of Ti and Fe is a proxy for rainfall with a sub-annual (ca. 6-month) resolution. Temperature and humidity display rapid and significant changes over the Holocene. The rapid transition from a cold (mean annual temperature (MAT) 3.5 °C lower than today) and wet Younger Dryas to a warm and dry early Holocene is dated at 11,410 cal yr BP. During the Holocene, MAT varied from ca. 2.5 °C below to 3.5° above present-day temperature. Warm periods (11,410-10,700, 9700-6900, 4000-2400 cal yr BP) were separated by colder intervals. The last 2.4 kyr of the record is affected by human impact. The Holocene remained dry until 7500 cal yr BP. Then, precipitations increased to reach a maximum between 5000 and 4500 cal yr BP. A rapid decrease occurred until 3500 cal yr BP and the late Holocene was dry. Spectral analysis of μXRF data show rainfall cyclicity at millennial scale throughout the Holocene, and at centennial down to ENSO scale in more specific time intervals. The highest rainfall intervals correlate with the highest activity of ENSO. Variability in solar output is possibly the main cause for this millennial to decadal cyclicity. We interpret ENSO and ITCZ as the main climate change-driving mechanisms in Frontino. Comparison with high-resolution XRF data from the Caribbean Cariaco Basin (a proxy for rainfall in the coastal Venezuelian cordilleras) demonstrates that climate in Frontino was Pacific-driven (ENSO-dominated) during the YD and early Holocene, whereas it was Atlantic

  10. Coastal Modeling System

    DTIC Science & Technology

    2014-09-04

    Coastal Inlets Research Program Coastal Modeling System The work unit develops the Coastal Modeling System ( CMS ) and conducts basic research to...further understanding of sediment transport under mixed forcing from waves and currents. The CMS is a suite of coupled two- dimensional numerical...models for simulating waves, hydrodynamics, salinity and sediment transport, and morphology change. The CMS was identified by the USACE Hydraulics and

  11. Holocene depositional history of a large glaciated estuary, Penobscot Bay, Maine

    USGS Publications Warehouse

    Knebel, H. J.

    1986-01-01

    Data from seismic-reflection profiles, sidescan sonar images, and sediment samples reveal the Holocene depositional history of the large (1100 km2) glaciated Penobscot Bay estuary of coastal Maine. Previous work has shown that the late Wisconsinan ice sheet retreated from the three main passages of the bay between 12,700 and 13,500 years ago and was accompanied by a marine transgression during which ice and sea were in contact. Isostatic recovery of the crust caused the bay to emerge during the immediate postglacial period, and relative sea level fell to at least -40 m sometime between 9000 and 11,500 years ago. During lowered sea level, the ancestral Penobscot River flowed across the subaerially exposed head of the bay and debouched into Middle Passage. Organic-matter-rich mud from the river was deposited rapidly in remnant, glacially scoured depressions in the lower reaches of Middle and West Passages behind a shallow (???20 m water depth) bedrock sill across the bay mouth. East Passage was isolated from the rest of the bay system and received only small amounts of locally derived fine-grained sediments. During the Holocene transgression that accompanied the eustatic rise of sea level, the locus of sedimentation shifted to the head of the bay. Here, heterogeneous fluvial deposits filled the ancestral valley of the Penobscot River as base level rose, and the migrating surf zone created a gently dipping erosional unconformity, marked by a thin (<2 m) lag deposit of coarse sand and gravel. As sea level continued to rise, a thin (???9 m) layer of acoustically transparent muddy sediments accumulated over a shallow platform in the eastern half of the bay head. Graded sediments within this stratum began to accumulate early in the transgression, and they record both the decrease in energy conditions and the waning influence of the Penobscot River at the head of the bay. In contrast, relatively thick (up to 25 m) silty clays accumulated within a subbottom trough in the

  12. Past and Future Ecosystem Change in the Coastal Zone

    NASA Astrophysics Data System (ADS)

    Gell, P.

    2017-02-01

    The coastal zone is in a constant state of flux. Long term records of change attest to high amplitude sea level changes. Relative stability though the Late Holocene has allowed for the evolution of barrier dune systems, estuaries and coastal lakes with associated plant and faunal associations. This evolution has been interspersed with changes in the balance between climate driven changes in outflow from catchments. These interactions have been considerably disturbed through the impacts of industrialised people who have diverted and consumed water and invested in infrastructure that has impacted on river flows and the tidal prism in estuaries. This has impacted their provisioning services to humans. It has also impacted their regulating services in that development along the coastline has impacted on the resilience of the littoral zone to absorb natural climate extremes. Looking from the past we can see the pathway to the future and more easily recognise the steps needed to avoid further coastal degradation. This will increasingly need to accommodate the impacts of future climate trends, increased climate extremes and rising seas. Coastal societies would do well to identify their long term pathway to adaptation to the challenges that lie ahead and plan to invest accordingly.

  13. Stature in Holocene foragers of North India.

    PubMed

    Lukacs, John R; Pal, J N; Nelson, Greg C

    2014-03-01

    The Ganga Plain of North India provides an archaeological and skeletal record of semi-nomadic Holocene foragers in association with an aceramic Mesolithic culture. Prior estimates of stature for Mesolithic Lake Cultures (MLC) used inappropriate equations from an American White reference group and need revision. Attention is given to intralimb body proportions and geo-climatic provenance of MLC series in considering the most suitable reference population. Regression equations from ancient Egyptians are used in reconstructing stature for MLC skeletal series from Damdama (DDM), Mahadaha (MDH), and Sarai Nahar Rai (SNR). Mean stature is estimated at between 174 (MDH) and 178 cm (DDM and SNR) for males, and between 163 cm (MDH) and 179 cm (SNR) for females. Stature estimates based on ancient Egyptian equations are significantly shorter (from 3.5 to 7.1 cm shorter in males; from 3.2 to 7.5 cm shorter in females) than estimates using the American White reference group. Revised stature estimates from tibia length and from femur + tibia more accurately estimate MLC stature for two reasons: a) these elements are highly correlated with stature and have lower standard estimates of error, and b) uncertainty regarding methods of measuring tibia length is avoided. When compared with Holocene samples of native Americans and Mesolithic Europeans, MLC series from North India are tall. This aspect of their biological variation confirms earlier assessments and results from the synergistic influence of balanced nutrition from broad-spectrum foraging, body-proportions adapted to a seasonally hot and arid climate, and the functional demands of a mobile, semi-nomadic life-style.

  14. Controls on fire activity over the Holocene

    NASA Astrophysics Data System (ADS)

    Kloster, S.; Brücher, T.; Brovkin, V.; Wilkenskjeld, S.

    2014-11-01

    Changes in fire activity over the last 8000 years are simulated with a global fire model driven by changes in climate and vegetation cover. The changes were separated into those caused through variations in fuel availability, fuel moisture or wind speed which react differently to changes in climate. Disentangling these controlling factors helps to understand the overall climate control on fire activity over the Holocene. Globally the burned area is simulated to increase by 2.5% between 8000 and 200 cal yr BP with larger regional changes compensating on a global scale. Despite the absence of anthropogenic fire ignitions, the simulated trends in fire activity agree reasonably well with continental scale reconstructions from charcoal records, with the exception of Europe. For some regions the change in fire activity is predominantly controlled through changes in fuel availability (Australia-Monsoon, American Tropics/Subtropics). For other regions changes in fuel moisture are more important for the overall trend in fire activity (North America, Sub-Saharan Africa, Europe, Asia-Monsoon). In Sub-Saharan Africa, for example, changes in fuel moisture alone lead to an increase in fire activity between 8000 and 200 cal yr BP, while changes in fuel availability lead to a decrease. Overall, the fuel moisture control is dominating the simulated fire activity for Sub-Saharan Africa. The simulations clearly demonstrate that both changes in fuel availability and changes in fuel moisture are important drivers for the fire activity over the Holocene. Fuel availability and fuel moisture do, however, have different climate controls. As such observed changes in fire activity can not be related to single climate parameters such as precipitation or temperature alone. Fire models, as applied in this study, in combination with observational records can help to understand the climate control on fire activity, which is essential to project future fire activity.

  15. Controls on fire activity over the Holocene

    NASA Astrophysics Data System (ADS)

    Kloster, S.; Brucher, T.; Brovkin, V.; Wilkenskjeld, S.

    2015-05-01

    Changes in fire activity over the last 8000 years are simulated with a global fire model driven by changes in climate and vegetation cover. The changes were separated into those caused through variations in fuel availability, fuel moisture or wind speed, which react differently to changes in climate. Disentangling these controlling factors helps in understanding the overall climate control on fire activity over the Holocene. Globally the burned area is simulated to increase by 2.5% between 8000 and 200 cal yr BP, with larger regional changes compensating nearly evening out on a global scale. Despite the absence of anthropogenic fire ignitions, the simulated trends in fire activity agree reasonably well with continental-scale reconstructions from charcoal records, with the exception of Europe. For some regions the change in fire activity is predominantly controlled through changes in fuel availability (Australia monsoon, Central America tropics/subtropics). For other regions changes in fuel moisture are more important for the overall trend in fire activity (North America, Sub-Saharan Africa, Europe, Asia monsoon). In Sub-Saharan Africa, for example, changes in fuel moisture alone lead to an increase in fire activity between 8000 and 200 cal yr BP, while changes in fuel availability lead to a decrease. Overall, the fuel moisture control is dominating the simulated fire activity for Sub-Saharan Africa. The simulations clearly demonstrate that both changes in fuel availability and changes in fuel moisture are important drivers for the fire activity over the Holocene. Fuel availability and fuel moisture do, however, have different climate controls. As such, observed changes in fire activity cannot be related to single climate parameters such as precipitation or temperature alone. Fire models, as applied in this study, in combination with observational records can help in understanding the climate control on fire activity, which is essential to project future fire

  16. NATIONAL COASTAL CONDITION REPORT III

    EPA Science Inventory

    Coastal waers in the US include estuaries, coastal wetlands, coral reefs, ,mangrove and kelp forests, seagrass meadows, and upwelling areas. Critical coastal habitats provide spawning grounds, nurseries, shelter, and food for finfish, shellfish, birds, and other wildlife. The n...

  17. NATIONAL COASTAL CONDITION REPORT III

    EPA Science Inventory

    Coastal waers in the US include estuaries, coastal wetlands, coral reefs, ,mangrove and kelp forests, seagrass meadows, and upwelling areas. Critical coastal habitats provide spawning grounds, nurseries, shelter, and food for finfish, shellfish, birds, and other wildlife. The n...

  18. Holocene evolution and sedimentation rate of Alikes Lagoon, Zakynthos island, Western Greece: preliminary results

    NASA Astrophysics Data System (ADS)

    Avramidis, P.; Kontopoulos, N.

    2009-07-01

    In the present study we present preliminary results from Alikes lagoon in Zakynthos island, an area that is one of the most seismically active regions of Greece. In order to estimate - interpret the Holocene evolution of the area and to reconstruct the palaeoenvironmental changes, we based on data derived from a 21 m sediment core. Sediment types, structure, colour, as well as contact depths and bed characteristics were recorded in the field. Standarised sedimentological analysis was carried out, on 46 samples including grain size analysis, calculation of moment measures, and micro- and molluscan fossils of 17 selected samples. Moreover, radiocarbon age determinations have been made on individual Cardium shells from two horizons and whole - core Magnetic Susceptibility (MS) measurements were taken. The interpretation of depositional environments suggests a coastal environment (restricted-shallow) with reduced salinity such as a lagoon margin and in a tidal flat and/or marsh particularly. The maximum age of the studied sediments is about 8500 BP. The rate of sedimentation between 8280 BP while 5590 BP was 5.3 mm/yr and between 5590 BP and modern times is on the order of 1.03 mm/yr. These sedimentation rates results are similar to other coastal areas of western Greece.

  19. Macrofossil records of West Antarctic Ice Sheet retreat during the Holocene

    NASA Technical Reports Server (NTRS)

    Berkman, Paul Arthur

    1993-01-01

    Marine macrofossils in emerged beaches around Antarctica represent a geochemical framework for interpreting meltwater signatures associated with variations in the adjacent ice sheet margins during the last 10,000 years. In particular, mollusc species provide ideal experimental templates for assessing hydrochemical variations in Antarctic coastal marine environments because of their excellent preservation, high abundances, circumpolar distributions, and carbonate shells, which incorporate trace elements and stable isotopes. Modern samples of the bivalve Adamussium colbecki, which were collected across a depth gradient in the vicinity of a glacial meltwater stream in West McMurdo Sound, revealed shell trace element concentrations that were significantly higher above 10 meters because of their exposure to meltwater runoff. This meltwater signature also was reflected by the shell oxygen isotopic composition, which was in equilibrium with the ambient seawater, as demonstrated by the overlap between the predicted and actual O-(delta-18)sub w values. These modern samples provide analogs for interpreting the geochemical records in their fossils, which were based solely on molluscan fossils, complement the above geochemical data by suggesting that the rate of beach emergence fluctuated around Antarctica during the mid-Holocene. Paleoenvironmental analysis of macrofossils from emerged beaches represents a new direction in Antarctic research that can be used to assess changes in the margins of the ice sheets since the Last Glacial Maximum. The resolution of these analyses will be enhanced by collaborations that are developing with scientists who are conducting comparable studies in other coastal regions around the continent.

  20. Macrofossil records of West Antarctic Ice Sheet retreat during the Holocene

    NASA Technical Reports Server (NTRS)

    Berkman, Paul Arthur

    1993-01-01

    Marine macrofossils in emerged beaches around Antarctica represent a geochemical framework for interpreting meltwater signatures associated with variations in the adjacent ice sheet margins during the last 10,000 years. In particular, mollusc species provide ideal experimental templates for assessing hydrochemical variations in Antarctic coastal marine environments because of their excellent preservation, high abundances, circumpolar distributions, and carbonate shells, which incorporate trace elements and stable isotopes. Modern samples of the bivalve Adamussium colbecki, which were collected across a depth gradient in the vicinity of a glacial meltwater stream in West McMurdo Sound, revealed shell trace element concentrations that were significantly higher above 10 meters because of their exposure to meltwater runoff. This meltwater signature also was reflected by the shell oxygen isotopic composition, which was in equilibrium with the ambient seawater, as demonstrated by the overlap between the predicted and actual O-(delta-18)sub w values. These modern samples provide analogs for interpreting the geochemical records in their fossils, which were based solely on molluscan fossils, complement the above geochemical data by suggesting that the rate of beach emergence fluctuated around Antarctica during the mid-Holocene. Paleoenvironmental analysis of macrofossils from emerged beaches represents a new direction in Antarctic research that can be used to assess changes in the margins of the ice sheets since the Last Glacial Maximum. The resolution of these analyses will be enhanced by collaborations that are developing with scientists who are conducting comparable studies in other coastal regions around the continent.

  1. A Glacial Isostatic Model for Early- mid Holocene Iron Fertilization of Antarctic Peninsula Shelf Waters

    NASA Astrophysics Data System (ADS)

    Leventer, A.; Domack, E. W.; King, M. A.

    2016-02-01

    Diatom-based proxy records from a dozen marine sediment cores recovered from the Antarctic Peninsula continental shelf document a geographically widespread episode of iron fertilization of shelf waters, that developed gradually, beginning 8,000 years before present (ybp), and ending relatively quickly, at 5500 ybp. We propose that a short, culminating period of post-glacial rebound and iceberg scouring served to resuspend littoral marine sediment, releasing soluble, bioavailable iron that induced high productivity. The timing and duration of the rebound event is well constrained by the chronology of near-coastal glacial recession and a very well constrained mantle viscosity, the latter determined by modern rebound associated with ice mass loss. The diatom data also document a longer open water season, characterized by a later advance of sea ice in the fall. We suggest that changes in the Southern Hemisphere westerly winds resulted in enhanced upwelling of Upper Circumpolar Deep Water (UCDW) onto the newly exposed and relatively shallow continental shelf. Warm UCDW may have driven the longer open water season, while iron may have been supplied from the re-suspension of shelf sediment, through upwelling and/or upward mixing from late season storms. A new glacial reconstruction for the Antarctic Peninsula suggests the delayed demise of ice domes and coastal deglaciation provided the final large post-glacial rebound event that is correlative to this unusual period of littoral sediment resuspension and consequent Fe-replete productivity that characterizes the early- mid Holocene.

  2. Stratigraphic and sedimentologic response to Late Quaternary climate change and glacio-eustasy, Colorado River, Gulf Coastal Plain of Texas

    SciTech Connect

    Blum, M.D. . Dept. of Geology)

    1992-01-01

    This paper summarizes results of investigations of the Colorado River, Gulf Coastal Plain of Texas, which provides a detailed record of fluvial response to late Quaternary climatic change and glacio-eustatic sea level rise. Four allostratigraphic units of late Pleistocene through modern age are differentiated in the bedrock-confined lower Colorado valley on the Inner Coastal Plain. Here up to 10 meters of late Pleistocene sediments underlie a terrace at 17--20 meters above the present-day channel. Two distinct allostratigraphic units underlie an extensive Holocene terrace at 12--14 meters above the present-day channel. Allostratigraphic units and bounding disconformities correlate with climatic changes that have been identified from paleobiological data, and represent stratigraphic response to changes in the relationship between discharge and sediment supply. In addition, changes in sedimentary facies through time represents a response to changes in climate coupled with a protracted degradation of upland soil mantles. This degradation of soils altered the rate at which precipitation inputs were transferred to stream channels as runoff, which led to increases in the peakedness of flood hydrographs and changes in the relative importance of channel versus floodplain depositional environments. Increased flood stages during the late Holocene promoted the increasing importance of floodplain construction by vertical accretion, and late Holocene to modern allostratigraphic units contain thick vertical accretion facies. These same allostratigraphic units and component facies persist downvalley to the Outer Coastal Plain, but stratigraphic architecture changes as a result of the last glacio-eustatic cycle. Here late Holocene and modern sediments onlap and bury late Pleistocene and early to middle Holocene stratigraphic units that were emplaced during the last sea level lowstand and the transgression that followed.

  3. The Holocene palaeogeography and relative sea level for two tidal basins of the German North Sea coast

    NASA Astrophysics Data System (ADS)

    Bungenstock, Friederike; Wartenberg, Wolfram; Mauz, Barbara; Freund, Holger; Frechen, Manfred; Weerts, Henk J. T.; Berner, Heinrich

    2014-05-01

    The response of coasts to global sea-level rise is highly variable. Knowledge of driving coastal parameters alongside the regional sea-level history is therefore indispensable when the response to global sea-level rise is to be assessed. Here, we study the Holocene relative sea-level of the south coast of the North Sea which is controlled by a number of very local parameters, as well as by regional glacio-isostatic adjustments. It is therefore crucial to restrict the data acquisition and evaluation to small coastal sections, ideally to single tidal basins, to minimize the sources of uncertainties (Bungenstock & Weerts 2010, 2012). We present data from two tidal basins, Langeoog and Jade Bay. For Langeoog a database derived from 600 cores, 68 km of Boomer seismic data, 33 radiocarbon ages and 8 OSL dates is available. (Bungenstock & Schäfer 2009, Mauz & Bungenstock 2007). For the Jade bay, the database comprises sedimentary markers, pollen and macro remains derived from 68 cores. The sedentary chronology is based on 54 radiocarbon ages and pollen constraints (Wartenberg & Freund 2011, Wartenberg et al. 2013). For both tidal basins the sedimentological record was interpreted in terms of the local paleogeographical development since about 7000 cal BP and its influence on the local relative sea-level curve. While the trend of the relative sea level is similar for both tidal basins, it shows a different altitude. The timing of the main marine transgression within the Langeoog area takes place ~3000 cal. BP whereas the sedimentological record of the Jade Bay shows two prominent transgressions, one for ~5000 cal. BP and one for ~3000 cal. BP. The Langeoog palaeo-environment is continuously characterised by marine influence. Within the Jade Bay two different palaeo-environments could be identified, documenting that from the West to the centre the landscape development in the Jade Bay was drainage driven feeding the associated fen peat with minerogenic water but being

  4. The Pleistocene-Holocene Unconformity in California Prehistory

    NASA Astrophysics Data System (ADS)

    Jones, T. L.

    2007-05-01

    The earliest archaeological record from California shows a dramatic unconformity or cultural hiatus between the terminal Pleistocene and the early Holocene. Clovis-like fluted projectile points which mark initial human colonization ca. 13,300-12,900 cal BP, are relatively common and have been found throughout the state, but almost exclusively as isolates. Early Holocene sites are abundant as well, particularly on the coast where at least 23 deposits show occupation as old as ca. 10,000-9000-cal BP. Only one of these, Daisy Cave, extends back into the terminal Pleistocene, but the remainder mark occupations that began only at the onset of the Holocene. There are almost no archaeological sites in California that date between 12,900 and 10,300 cal BP or that exhibit superimposed terminal Pleistocene and early Holocene components. This pattern is consistent with a significant disruptive event during the Younger-Dryas.

  5. Rapid deglacial and early Holocene expansion of peatlands in Alaska

    PubMed Central

    Jones, Miriam C.; Yu, Zicheng

    2010-01-01

    Northern peatlands represent one of the largest biospheric carbon (C) reservoirs; however, the role of peatlands in the global carbon cycle remains intensely debated, owing in part to the paucity of detailed regional datasets and the complexity of the role of climate, ecosystem processes, and environmental factors in controlling peatland C dynamics. Here we used detailed C accumulation data from four peatlands and a compilation of peatland initiation ages across Alaska to examine Holocene peatland dynamics and climate sensitivity. We find that 75% of dated peatlands in Alaska initiated before 8,600 years ago and that early Holocene C accumulation rates were four times higher than the rest of the Holocene. Similar rapid peatland expansion occurred in West Siberia during the Holocene thermal maximum (HTM). Our results suggest that high summer temperature and strong seasonality during the HTM in Alaska might have played a major role in causing the highest rates of C accumulation and peatland expansion. The rapid peatland expansion and C accumulation in these vast regions contributed significantly to the peak of atmospheric methane concentrations in the early Holocene. Furthermore, we find that Alaskan peatlands began expanding much earlier than peatlands in other regions, indicating an important contribution of these peatlands to the pre-Holocene increase in atmospheric methane concentrations. PMID:20368451

  6. Holocene winter climate variability in Central and Eastern Europe.

    PubMed

    Perșoiu, Aurel; Onac, Bogdan P; Wynn, Jonathan G; Blaauw, Maarten; Ionita, Monica; Hansson, Margareta

    2017-04-26

    Among abundant reconstructions of Holocene climate in Europe, only a handful has addressed winter conditions, and most of these are restricted in length and/or resolution. Here we present a record of late autumn through early winter air temperature and moisture source changes in East-Central Europe for the Holocene, based on stable isotopic analysis of an ice core recovered from a cave in the Romanian Carpathian Mountains. During the past 10,000 years, reconstructed temperature changes followed insolation, with a minimum in the early Holocene, followed by gradual and continuous increase towards the mid-to-late-Holocene peak (between 4-2 kcal BP), and finally by a decrease after 0.8 kcal BP towards a minimum during the Little Ice Age (AD 1300-1850). Reconstructed early Holocene atmospheric circulation patterns were similar to those characteristics of the negative phase of the North Atlantic Oscillation (NAO), while in the late Holocene they resembled those prevailing in the positive NAO phase. The transition between the two regimes occurred abruptly at around 4.7 kcal BP. Remarkably, the widespread cooling at 8.2 kcal BP is not seen very well as a temperature change, but as a shift in moisture source, suggesting weaker westerlies and increased Mediterranean cyclones penetrating northward at this time.

  7. Large Holocene lakes and climate change in the Chihuahuan Desert

    NASA Astrophysics Data System (ADS)

    Castiglia, Peter J.; Fawcett, Peter J.

    2006-02-01

    Lake-level variations preserved as beach ridges in the Laguna El Fresnal and Laguna Santa María subbasins, northern Mexico, record millennially spaced episodes of increased precipitation during the Holocene epoch. We find that the early, middle, and late Holocene were punctuated by periods wet enough to establish large pluvial lakes in currently dry basins in the Chihuahuan Desert; the largest dated pluvial lake covered ˜5650 km2 during the early Holocene. Constructional beach ridges in these subbasins are 221 ± 33 14C yr B.P. (Little Ice Age equivalent), 3815 ± 52 to 4251 ± 59 14C yr B.P. (early Neoglacial), 6110 ± 80 to 6721 ± 68 14C yr B.P. (mid-Holocene), and 8269 ± 64 to 8456 ± 97 14C yr B.P. (early Holocene), dates that correlate with other millennially spaced wet or cold events in the Northern Hemisphere. We attribute these wet episodes to increased precipitation, cooler temperatures, and reduced evaporation following southward shifts in winter storm tracks, which are related to long-term El Niño Southern Oscillation variability during the Holocene.

  8. Rapid deglacial and early Holocene expansion of peatlands in Alaska.

    PubMed

    Jones, Miriam C; Yu, Zicheng

    2010-04-20

    Northern peatlands represent one of the largest biospheric carbon (C) reservoirs; however, the role of peatlands in the global carbon cycle remains intensely debated, owing in part to the paucity of detailed regional datasets and the complexity of the role of climate, ecosystem processes, and environmental factors in controlling peatland C dynamics. Here we used detailed C accumulation data from four peatlands and a compilation of peatland initiation ages across Alaska to examine Holocene peatland dynamics and climate sensitivity. We find that 75% of dated peatlands in Alaska initiated before 8,600 years ago and that early Holocene C accumulation rates were four times higher than the rest of the Holocene. Similar rapid peatland expansion occurred in West Siberia during the Holocene thermal maximum (HTM). Our results suggest that high summer temperature and strong seasonality during the HTM in Alaska might have played a major role in causing the highest rates of C accumulation and peatland expansion. The rapid peatland expansion and C accumulation in these vast regions contributed significantly to the peak of atmospheric methane concentrations in the early Holocene. Furthermore, we find that Alaskan peatlands began expanding much earlier than peatlands in other regions, indicating an important contribution of these peatlands to the pre-Holocene increase in atmospheric methane concentrations.

  9. Holocene vegetation history from fossil rodent middens near Arequipa, Peru

    USGS Publications Warehouse

    Holmgren, C.A.; Betancourt, J.L.; Rylander, K.A.; Roque, J.; Tovar, O.; Zeballos, H.; Linares, E.; Quade, Jay

    2001-01-01

    Rodent (Abrocoma, Lagidium, Phyllotis) middens collected from 2350 to 2750 m elevation near Arequipa, Peru (16??S), provide an ???9600-yr vegetation history of the northern Atacama Desert, based on identification of >50 species of plant macrofossils. These midden floras show considerable stability throughout the Holocene, with slightly more mesophytic plant assemblages in the middle Holocene. Unlike the southwestern United States, rodent middens of mid-Holocene age are common. In the Arequipa area, the midden record does not reflect any effects of a mid-Holocene mega drought proposed from the extreme lowstand (100 m below modern levels, >6000 to 3500 yr B.P.) of Lake Titicaca, only 200 km east of Arequipa. This is perhaps not surprising, given other evidence for wetter summers on the Pacific slope of the Andes during the middle Holocene as well as the poor correlation of summer rainfall among modern weather stations in the central AndesAtacama Desert. The apparent difference in paleoclimatic reconstructions suggests that it is premature to relate changes observed during the Holocene to changes in El Nin??o Southern Oscillation modes. ?? 2001 University of Washington.

  10. Coastal zone management

    NASA Technical Reports Server (NTRS)

    Tilton, E. L., III

    1975-01-01

    A panel of federal and state representatives concerned with coastal zone affairs discussed their problems in this area. In addition, several demonstrations of the application of remote sensing technology to coastal zone management were described. These demonstrations were performed by several agencies in a variety of geographical areas.

  11. NATIONAL COASTAL ASSESSMENT

    EPA Science Inventory

    The purpose of the National Coastal Assessment (NCA) is to estimate the status and trends of the condition of the nation's coastal resources on a state, regional and national basis. Based on NCA monitoring from 1999-2001, 100% of the nation's estuarine waters (at over 2500 locati...

  12. NATIONAL COASTAL CONDITION REPORT

    EPA Science Inventory

    The National Coastal Condition report compiles several available data sets from different agencies and areas of the country and summarizes them to present a broad baseline picture of the condition of coastal waters. Although data sets presented in this report do not cover all coa...

  13. NATIONAL COASTAL CONDITION REPORT

    EPA Science Inventory

    The National Coastal Condition report compiles several available data sets from different agencies and areas of the country and summarizes them to present a broad baseline picture of the condition of coastal waters. Although data sets presented in this report do not cover all coa...

  14. NATIONAL COASTAL ASSESSMENT

    EPA Science Inventory

    The purpose of the National Coastal Assessment (NCA) is to estimate the status and trends of the condition of the nation's coastal resources on a state, regional and national basis. Based on NCA monitoring from 1999-2001, 100% of the nation's estuarine waters (at over 2500 locati...

  15. Resilience from coastal protection.

    PubMed

    Ewing, Lesley C

    2015-10-28

    Coastal areas are important residential, commercial and industrial areas; but coastal hazards can pose significant threats to these areas. Shoreline/coastal protection elements, both built structures such as breakwaters, seawalls and revetments, as well as natural features such as beaches, reefs and wetlands, are regular features of a coastal community and are important for community safety and development. These protection structures provide a range of resilience to coastal communities. During and after disasters, they help to minimize damages and support recovery; during non-disaster times, the values from shoreline elements shift from the narrow focus on protection. Most coastal communities have limited land and resources and few can dedicate scarce resources solely for protection. Values from shore protection can and should expand to include environmental, economic and social/cultural values. This paper discusses the key aspects of shoreline protection that influence effective community resilience and protection from disasters. This paper also presents ways that the economic, environmental and social/cultural values of shore protection can be evaluated and quantified. It presents the Coastal Community Hazard Protection Resilience (CCHPR) Index for evaluating the resilience capacity to coastal communities from various protection schemes and demonstrates the use of this Index for an urban beach in San Francisco, CA, USA. © 2015 The Author(s).

  16. On the application of contemporary bulk sediment organic carbon isotope and geochemical datasets for Holocene sea-level reconstruction in NW Europe

    NASA Astrophysics Data System (ADS)

    Wilson, Graham P.

    2017-10-01

    Bulk organic stable carbon isotope (δ13C) and element geochemistry (total organic carbon (TOC) and organic carbon to total nitrogen (C/N)) analysis is a developing technique in Holocene relative sea-level (RSL) research. The uptake of this technique in Northern Europe is limited compared to North America, where the common existence of coastal marshes with isotopically distinctive C3 and C4 vegetation associated with well-defined inundation tolerance permits the reconstruction of RSL in the sediment record. In Northern Europe, the reduced range in δ13C values between organic matter sources in C3 estuaries can make the identification of elevation-dependent environments in the Holocene sediment record challenging and this is compounded by the potential for post-depositional alteration in bulk δ13C values. The use of contemporary regional δ13C, C/N and TOC datasets representing the range of physiographic conditions commonly encountered in coastal wetland sediment sequences opens up the potential of using absolute values of sediment geochemistry to infer depositional environments and associated reference water levels. In this paper, the application of contemporary bulk organic δ13C, C/N and TOC to reconstruct Holocene RSL is further explored. An extended contemporary regional geochemical dataset of published δ13C, C/N and TOC observations (n = 142) from tidal-dominated C3 wetland deposits (representing tidal flat, saltmarsh, reedswamp and fen carr environments) in temperate NW Europe is compiled, and procedures implemented to correct for the 13C Suess effect on contemporary δ13C are detailed. Partitioning around medoids analysis identifies two distinctive geochemical groups in the NW European dataset, with tidal flat/saltmarsh and reedswamp/fen carr environments exhibiting characteristically different sediment δ13C, C/N and TOC values. A logistic regression model is developed from the NW European dataset in order to objectively identify in the sediment record

  17. Characteristics of Southern California coastal aquifer systems

    USGS Publications Warehouse

    Edwards, B.D.; Hanson, R.T.; Reichard, E.G.; Johnson, T.A.

    2009-01-01

    , litany of names for the various formations, lithofacies, and aquifer systems identified within these basins. Despite these nomenclatural problems, available data show that most basins contain similar sequences of deposits and share similar geologic histories dominated by glacio-eustatic sea-level fluctuations, and overprinted by syndepositional and postdepositional tectonic deformation. Impermeable, indurated mid-Tertiary units typically form the base of each siliciclastic groundwater basin. These units are overlain by stacked sequences of Pliocene to Holocene interbedded marine, paralic, fluvial, and alluvial sediment (weakly indurated, folded, and fractured) that commonly contain the historically named "80-foot sand," "200-foot sand," and "400-foot gravel" in the upper part of the section. An unconformity, cut during the latest Pleistocene lowstand (??18O stage 2; ca. 18 ka), forms a major sequence boundary that separates these units from the overlying Holocene fluvial sands and gravels. Unconfined aquifers occur in amalgamated coarse facies near the bounding mountains (forebay area). These units are inferred to become lithologically more complex toward the center of the basins and coast line, where interbedded permeable and low-permeability alluvial, fluvial, paralic, and marine facies contain confined aquifers (pressure area). Coastal bounding faults limit intrabasin and/or interbasin flow in parts of many basins. ?? 2009 Geological Society of America.

  18. Holocene Glacial Fluctuation Reconstructed From Glacio-marine Sediments at Skallen in the Lüzow-Holm Bay, East Antarctica

    NASA Astrophysics Data System (ADS)

    Maemoku, H.; Miura, H.; Iwasaki, S.; Yokoyama, Y.; Matsuzaki, H.

    2006-12-01

    The history of glacial fluctuation in a fringe of Antarctica since LGM is able to be reconstructed from relative sea level change with raised marine sediments or coastal terraces due to isostatic rebound. In the Terra Nova bay, west Antarctica, ages of abandoned penguin rookeries were concentrated from 5,000 to 4,000 BP and warming event corresponding to that period could be recognized as " Penguin Optimum" (Baroni and Oronbelli, 1994). Concentration of ages of abandoned rookeries in almost same period is also reported in Windmill Islands, east Antarctica (Goodwin, 1993). Miura et al.(2002) revealed that the rate of coastal emergence due to isostatic rebound changed during mid Holocene by observing the stratigraphy of raised beach which had seventeen tidal steps in Lützow-Holm bay, east Antarctica and indicated the occurrence of warming event in mid Holocene. This study aims to reconstruct the history of glacial fluctuation in the east Antarctica since mid Holocene by mapping of glacio-marine sediments and geomorphological evidence of glacial advance or transgressional marine environment. The preliminary results of this study are as follows. 1) We could discriminate two periods of glacial advance since mid Holocene. The present belongs to the last retreat period. The fist period of glacial advance occurred in between 5,000 BP and 3,000 BP. The next one began at least since 1,950 BP and lasted for 200 years. The extent and duration of glacial advance was smaller than the first period. 2) The transitional period from the first glacial advance to the following retreat period possibly accords with the timing of other warming events reported in the antarctic area. We would like to indicate that the period of warming events in Antarctica apparently seems to be consistent with dry and cold period which is usually correlated with with the fluctuation of sunspots number reported in many areas such as Lake Chad (Rognon, 1979) or South Africa (Deacon and Lancaster, 1988

  19. Diatom-inferred hydrological changes and Holocene geomorphic transitioning of Africa's largest estuarine system, Lake St Lucia

    NASA Astrophysics Data System (ADS)

    Gomes, M.; Humphries, M. S.; Kirsten, K. L.; Green, A. N.; Finch, J. M.; de Lecea, A. M.

    2017-06-01

    The diverse lagoons and coastal lakes along the east coast of South Africa occupy incised valleys that were flooded during the rise and subsequent stabilisation of relative sea-level during the Holocene. Sedimentary deposits contained within these waterbodies provide an opportunity to investigate complex hydrological and sedimentological processes, and examine sea-level controls governing system geomorphic evolution. In this paper, we combine diatom and sulfur isotope analyses from two sediment cores extracted from the northern sub-basins of Lake St Lucia, a large shallow estuarine lake that is today largely isolated from direct ocean influence behind a Holocene-Pleistocene barrier complex. Analyses allow the reconstruction of hydrological changes associated with the geomorphic development of the system over the mid-to late Holocene. The sedimentary sequences indicate that St Lucia was a shallow, partially enclosed estuary/embayment dominated by strong tidal flows prior to ∼6200 cal. BP. Infilling was initiated when sea-level rise slowed and stabilised around present day levels, resulting in the accumulation of fine-grained sediment behind an emergent proto-barrier. Diatom assemblages, dominated by marine benthic and epiphytic species, reveal a system structured by marine water influx and characterised by marsh and tidal flat habitats until ∼4550 cal. BP. A shift in the biological community at ∼4550 cal. BP is linked to the development of a back-barrier water body that supported a brackish community. Marine planktonics and enrichments in δ34S suggest recurrent, large-scale barrier inundation events during this time, coincident with a mid-Holocene sea-level highstand. Periodic marine incursions associated with episodes of enhanced storminess and overwash remained prevalent until ∼1200 cal. BP, when further barrier construction ultimately isolated the northern basins from the ocean. This study provides the first reconstruction of the palaeohydrological

  20. Oysters, estuaries, and Late Pleistocene-Holocene sea level, northeastern Gulf of Mexico

    SciTech Connect

    Schroeder, W.W. . Marine Science Program); Shultz, A.W. )

    1993-03-01

    The timing and magnitude of global sea level fluctuations over the past 35 kyr remain nondum ostenduntur after three decades of study. The construction of local relative sea level histories is often complicated by the need to assess regional tectonic and climatic components together. The authors attempt to contribute to an understanding of sea level fluctuations in the northeastern Gulf of Mexico through the application of faunal tracking, using fossil oyster shells as indicators of paleoestuarine environments. They assume that sites on the continental shelf where oysters have been collected were coastal and therefore are reasonable approximations of past shoreline locations and sea-level elevations. They acknowledge that this assumption is a leap of faith for some observers, but is justified as a provisional step toward an independent determination. Insights into Quaternary coastal paleogeography are gathered from locations and radiocarbon ages of American oyster (Crassostrea virginica) shells collected from the Alabama continental shelf. Prior to the onset of the last Wisconsinan glaciation (35 to 26 kyr BP), estuaries occupied a zone 20 to 25 km seaward of today's coastline. As glaciation increased and sea level was lowered (23 to 21 kyr BP), open coastal estuarine conditions developed southward. Oysters dating from the lowstand period (20 to 16 kyr BP) have not been collected. As sea level rose over the next 10 kyr (16 to 6 kyr BP), estuaries were displaced northward in steps. This data on depths and ages can be viewed as supporting an interpretation of fluctuating Holocene sea level, rather than a steady sea-level rise.

  1. Holocene sea ice history and climate variability along the main axis of the Northwest Passage, Canadian Arctic

    NASA Astrophysics Data System (ADS)

    Ledu, David; Rochon, André; de Vernal, Anne; Barletta, Francesco; St-Onge, Guillaume

    2010-06-01

    Palynological, geochemical, and physical records were used to document Holocene paleoceanographic changes in marine sediment core from Dease Strait in the western part of the main axis of the Northwest Passage (core 2005-804-006 PC latitude 68°59.552‧N, longitude 106°34.413‧W). Quantitative estimates of past sea surface conditions were inferred from the modern analog technique applied to dinoflagellate cyst assemblages. The chronology of core 2005-804-006 PC is based on a combined use of the paleomagnetic secular variation records and the CALS7K.2 time-varying spherical harmonic model of the geomagnetic field. The age-depth model indicates that the core spans the last ˜7700 cal years B.P., with a sedimentation rate of 61 cm ka-1. The reconstructed sea surface parameters were compared with those from Barrow Strait and Lancaster Sound (cores 2005-804-004 PC and 2004-804-009 PC, respectively), which allowed us to draw a millennial-scale Holocene sea ice history along the main axis of the Northwest Passage (MANWP). Overall, our data are in good agreement with previous studies based on bowhead whale remains. However, dinoflagellate sea surface based reconstructions suggest several new features. The presence of dinoflagellate cysts in the three cores for most of the Holocene indicates that the MANWP was partially ice-free over the last 10,000 years. This suggests that the recent warming observed in the MANWP could be part of the natural climate variability at the millennial time scale, whereas anthropogenic forcing could have accelerated the warming over the past decades. We associate Holocene climate variability in the MANWP with a large-scale atmospheric pattern, such as the Arctic Oscillation, which may have operated since the early Holocene. In addition to a large-scale pattern, more local conditions such as coastal current, tidal effects, or ice cap proximity may have played a role on the regional sea ice cover. These findings highlight the need to further

  2. Proxy-Derived Reconstructions of Holocene Paleoclimate for the Hudson Bay Lowlands, an Extensive Peatland in Northern Canada

    NASA Astrophysics Data System (ADS)

    Finkelstein, S. A.; Bunbury, J.; Friel, C.; O'Reilly, B.

    2013-12-01

    The Hudson Bay Lowlands (HBL) is an extensive peatland in northern Canada where an estimated 31 Pg of carbon have accumulated during the Holocene. Given the large size of this carbon pool and the rapid rate of climate warming at high latitudes, quantifying the responses of this peatland to climate change is a critical research priority. Comparing Holocene paleoclimate reconstructions and paleo-vegetation and carbon dynamics in HBL peatlands through analyses of sediment cores is an effective approach to understanding the sensitivity of the carbon pool to climate. Robust paleoclimate reconstructions for the Holocene are needed for such comparisons. Until recently, there have been few paleoclimate reconstructions available for the HBL. Owing to the unique geographic setting of this low lying region to the west of Hudson Bay, reconstructions from adjacent subarctic regions are not directly applicable. We synthesize in this paper a series of paleoenvironmental records derived from biological proxies preserved in lake and wetland sediment cores collected from within the HBL with the goal of improving available paleoclimate information for the region. Our available pollen records document a series of vegetation changes during the Holocene, beginning with the establishment of coastal or salt marsh communities after emergence of the HBL from the Tyrrell Sea, followed by establishment of vegetation typical of poor fens or bogs. These local vegetation changes are apparently primarily related to hydrological changes driven by isostatic rebound and autogenic processes. Regional assemblages composed of tree pollen, which may be more directly tied to climate, show less variability during the Holocene. Reconstructions using modern analogs suggest minimal variation in temperature during the period of record, although these reconstructions show a moderate increase in precipitation following 3000 yrs BP, corresponding to Neoglacial climates reported at other northern high latitude

  3. Coastal evolution between two giant rivers: The Chan May embayment in central Vietnam

    NASA Astrophysics Data System (ADS)

    Gouramanis, C.; Switzer, A.; Bristow, C.; Pham, D. T.; Mauz, B.; Pile, J.; Doan, L. D.; Hoang, Q. D.; Ngo, C. K.; Dao, N.; Polivka, P.; Soria, L.; Lee, Y.; Sloss, C.; Hoang, L. V.

    2015-12-01

    The coastal landscapes of Vietnam are dominated in the north and south by the very large Red and Mekong rivers. Central Vietnam, in contrast, has few large rivers that flow to the coastal zone. This coupled with the high relief (>1500 m) of the granitic Truong Son Range and shallow gradient continental shelf, has produced two different coastal geomorphologies. The first is a shallow basin infilled with a sequence of parallel, arcuate beach ridges, and the second includes the development of shore-parallel spits and coastal lagoons. All systems are Holocene in age and we present evidence of the Holocene evolution of the northward-facing, beach ridge strandplain located in the Chan May embayment, approximately 35 km north of Danang. This embayment is relatively small (5 km long at the beach and with a beach ridge sequence that spans 11 km from the modern beach to the base of the Truong Son Range) compared to other beach ridge strandplains to the north and south and serves as an analogue for the evolution of these larger systems. The Holocene evolution of the embayment was resolved using Ground Penetrating Radar (GPR), high-resolution sedimentological analysis and quartz Optically Stimulated Luminescence were used to investigate the internal stratigraphy and chronological development of the beach ridges at Chan May. The strandplain contains uniform, clean quartz-rich sediment interspersed by thin heavy mineral rich bands forming shallow-gradient beach ridges that have steadily prograded seaward during the regression after the mid-Holocene sea level highstand. As the beach ridges prograded seaward, a small river feeding directly from the Truong Son Range meandered across the strandplain and significantly modified the embayment. Recently, the river has become much reduced due to anthropogenic modification of the river and landscape. Prior to the Holocene marine highstand, the area was similarly characterized by a surface of prograding beach ridges that were eroded by

  4. Stratigraphic and hydrogeologic framework of the Alabama Coastal Plain

    USGS Publications Warehouse

    Davis, M.E.

    1988-01-01

    Tertiary and Cretaceous sand aquifers of the Southeastern United States Coastal Plain comprise a major multlstate aquifer system informally defined as the Southeastern Coastal Plain aquifer system, which is being studied as part of the U.S. Geological Survey's Regional Aquifer System Analysis (RASA) program. The major objectives of each RASA study are to identify, delineate, and map the distribution of permeable clastlc rock, to examine the pattern of ground-water flow within the regional aquifers, and to develop digital computer simulations to understand the flow system. The Coastal Plain aquifers in Alabama are being studied as a part of this system. This report describes the stratlgraphlc framework of the Cretaceous, Tertiary, and Quaternary Systems in Alabama to aid in delineating aquifers and confining units within the thick sequence of sediments that comprises the Southeastern Coastal Plain aquifer system in the State. Stratigraphlc units of Cretaceous and Tertiary age that make up most of the aquifer system in the Coastal Plain of Alabama consist of clastlc deposits of Early Cretaceous age; the Coker and Gordo Formations of the Tuscaloosa Group, Eutaw Formation, and Selma Group of Late Cretaceous age; and the Midway, Wilcox, and Clalborne Groups of Tertiary age. However, stratigraphlc units of late Eocene to Holocene age partially overlie and are hydraulically connected to clastic deposits in southern Alabama. These upper carbonate and clastlc stratlgraphic units also are part of the adjoining Florldan and Gulf Coastal Lowlands aquifer systems. The Coastal Plain aquifer system is underlain by pre-Cretaceous rocks consisting of low-permeabillty sedimentary rocks of Paleozolc, Triassic, and Jurassic age, and a complex of metamorphic and igneous rocks of Precambrian and Paleozolc age similar to those found near the surface in the Piedmont physiographic province. Twelve hydrogeologlc units in the Alabama Coastal Plain are defined--slx aquifers and six confining

  5. Holocene sediment distribution on the inner continental shelf of northeastern South Carolina: implications for the regional sediment budget and long-term shoreline response

    USGS Publications Warehouse

    Denny, Jane F.; Schwab, William C.; Baldwin, Wayne E.; Barnhardt, Walter A.; Gayes, Paul T.; Morton, R.A.; Warner, John C.; Driscoll, Neal W.; Voulgaris, George

    2013-01-01

    High-resolution geophysical and sediment sampling surveys were conducted offshore of the Grand Strand, South Carolina to define the shallow geologic framework of the inner shelf. Results are used to identify and map Holocene sediment deposits, infer sediment transport pathways, and discuss implications for the regional coastal sediment budget. The thickest deposits of Holocene sediment observed on the inner shelf form shoal complexes composed of moderately sorted fine sand, which are primarily located offshore of modern tidal inlets. These shoal deposits contain ~67 M m3 of sediment, approximately 96% of Holocene sediment stored on the inner shelf. Due to the lack of any significant modern fluvial input of sand to the region, the Holocene deposits are likely derived from reworking of relict Pleistocene and older inner-shelf deposits during the Holocene marine transgression. The Holocene sediments are concentrated in the southern part of the study area, due to a combination of ancestral drainage patterns, a regional shift in sediment supply from the northeast to the southwest in the late Pleistocene, and proximity to modern inlet systems. Where sediment is limited, only small, low relief ridges have formed and Pleistocene and older deposits are exposed on the seafloor. The low-relief ridges are likely the result of a thin, mobile veneer of sediment being transported across an irregular, erosional surface formed during the last transgression. Sediment textural trends and seafloor morphology indicate a long-term net transport of sediment to the southwest. This is supported by oceanographic studies that suggest the long-term sediment transport direction is controlled by the frequency and intensity of storms that pass through the region, where low pressure systems yield net along-shore flow to the southwest and a weak onshore component. Current sediment budget estimates for the Grand Strand yield a deficit for the region. Volume calculations of Holocene deposits on the

  6. Coastal Hazards: Hurricanes, Tsunamis, Coastal Erosion.

    ERIC Educational Resources Information Center

    Vandas, Steve

    1998-01-01

    Details an ocean-based lesson and provides background information on the designation of 1998 as the "Year of the Ocean" by the United Nations. Contains activities on the poster insert that can help raise student awareness of coastal-zone hazards. (DDR)

  7. Coastal Hazards: Hurricanes, Tsunamis, Coastal Erosion.

    ERIC Educational Resources Information Center

    Vandas, Steve

    1998-01-01

    Details an ocean-based lesson and provides background information on the designation of 1998 as the "Year of the Ocean" by the United Nations. Contains activities on the poster insert that can help raise student awareness of coastal-zone hazards. (DDR)

  8. Late Holocene Andesitic Eruptions at Mount Rainier

    NASA Astrophysics Data System (ADS)

    Sisson, T. W.; Vallance, J. W.

    2005-12-01

    Holocene Mt. Rainier erupted much more frequently than is recorded by its 11 pumiceous tephras. In the 2.6-2.2 ka Summerland eruptive period, 6 groups of thin (1-5 mm) Sparsely Vesicular Glassy (SVG) ashes were deposited (S1-S6), followed by the 0.3 km3 C-tephra. Two groups of andesitic lava flows and one andesitic block-and-ash flow (2.45 ka) also erupted in the Summerland period (ice conceals any other products). Based on glass composition the pyroclastic flow correlates with S4 ashes that also contain pumiceous grains and rare pumice lapilli. The first of the lava groups, exposed in windows through the Emmons and Winthrop glaciers, is Sr-rich for Mt. Rainier eruptives and correlates with S5 & S6 ashes based on similar high-Sr plagioclase. The ensuing C-tephra formed by plinian eruption of mixed and mingled magma comprising 4 juvenile components: mixed porphyritic andesite pumice, crystal-poor andesite scoria, vesicular high-Sr dacite blebs in pumice and scoria, and poorly inflated crystal-rich high-Sr dacite. High-Sr components were probably entrained conduit linings and segregations from the preceding high-Sr eruptions. The youngest lava group, exposed at the summit, is normal-Sr andesite lacking mixing textures of the C-tephra, and represents eruption of another small batch of andesitic magma perhaps just after the C event. SVG ash grains have blocky-to-fluidal shapes, are rich in plagioclase microlites, and their glasses are high-SiO2 (66-78%) and low-Al2O3 (15-11%). Melting experiments yield apparent equilibration pressures <50MPa for SVG liquids. SVG ashes likely result from shallow hydromagmatic explosions as largely degassed magmas transited the upper-edifice hydrothermal system during effusive eruptions. Rare pumice lapilli codeposited with S1, S2, and S4 ashes have microlite-free dacitic glasses, one with nonreacted hbl phenocrysts. These pumice formed from magmas that ascended rapidly from reservoir depths, synchronous with or closely between effusive

  9. The Holocene Paleolimnology of Lake Superior

    NASA Astrophysics Data System (ADS)

    Hyodo, A.; Longstaffe, F. J.

    2010-12-01

    This study describes contributions of glacial meltwater to Lake Superior over the last 11,000 cal BP. Rhythmites (interpreted as varves), lithological and mineralogical variations, and radiocarbon dating were used to establish chronostratigraphic correlation among four sediment cores from Lake Superior (Duluth, Caribou and Ile Parisienne basins, Thunder Bay Trough). Glacial sediments were deposited between 10,850 and 8,800 cal BP. The oxygen-isotope compositions of ostracodes record the presence of glacial meltwater in ancient Lake Superior as the Laurentide Ice Sheet waxed and waned. Glacial meltwater was increasingly dominant between ~10,850 and ~9,250 cal BP, particularly as thick varves formed in northern portions of the Lake Superior Basin (10,400-10,200, 9,900 and 9,300-9,200 cal BP). Glacial meltwater supply was reduced in the Thunder Bay Trough between 9,250 and 8,950 cal BP, but returned from 8,950 to 8,800 cal BP. Glacial meltwater flow from the Lake Superior Basin probably bypassed the Huron Basin several times during this period. Final termination of glacial meltwater supply occurred at 8,800 cal BP - coincident with cessation of varve formation and inception of ancient Lakes Agassiz-Ojibway and Houghton. Primary productivity was very low and algal growth occurred under conditions of extreme nitrogen deficiency - as determined using TOC, TN and C/N ratios - until glacial meltwater supply to the Basin was ended. The postglacial sediments are non-calcareous. The diatom silica proxy record shows that oxygen-isotope compositions of water rapidly increased after glacial meltwater termination, reaching -10 per mil during the Holocene Thermal Maximum. The oxygen-isotope compositions of water decreased at 3,000 cal BP in response to the Holocene Neoglacial Interval before gradually rising to Lake Superior’s modern value of -8.7 per mil. Aquatic primary productivity, inferred using TOC, TN, and the carbon- and nitrogen isotope compositions, has increased

  10. Postglacial sea-level rise and its impact on the circum-arctic Holocene climate evolution

    NASA Astrophysics Data System (ADS)

    Bauch, Henning; Abramova, Ekaterina; Alenius, Teija; Saarnisto, Matti

    2016-04-01

    The global sea-level rise after the last glaciation not only affected the surface properties (circulation, T-S, sea ice seasonality) of the Arctic Ocean and nearby seas it also had a strong impact on the Holocene development of the shallow North Siberian shelf systems and the environmental evolution of the adjacent hinterland areas. In this region sea level reconstructions indicate the postglacial highstand occurred some time in the middle Holocene, between 6 to 5 ka (Klemann et al., 2015). After that time the sedimentary regime of the shelf seas stabilized as noted in a drastic decrease in sedimentation rates observed in all sediment cores taken from middle to outer shelf water depths of the Laptev Sea (Bauch et al. 2001). But, at water depths lower than 30 meters - i.e., in the inner shelf and nearer to the coasts - sedimentation continued at relatively higher rates, presumably due to input of terrigenous material from river runoff as well as coastal erosion. In relation to the latter process, the huge Lena Delta should comprise a region of sediment catchment where aggradation wins over erosion. However, little is known about the detailed history of this delta during the second half of the Holocene. We therefore have investigated three islands within the Lena Delta. All of these are comprised of massive peat of several meters in thickness. Picking discrete specimens of water mosses (Sphagnum) only, we have carefully dated these peat sections. The depth/age relation of the sampled profiles reflect the growth rate of peat, and thus, the islands. It shows that the islands' history above the present-day delta sea level is about 4000 yrs. old. Moreover, a significant change in peat growth is noted after 2500 yrs BP in both, accumulation and composition, and allows the conclusion of a major shift in Arctic environmental conditions since then. Thus, our results add further information also for other coastal studies, as the ongoing degradation of the rather vulnerable

  11. Bacterial diversity and distribution in the holocene sediments of a northern temperate lake.

    PubMed

    Nelson, David M; Ohene-Adjei, Samuel; Hu, Feng Sheng; Cann, Isaac K O; Mackie, Roderick I

    2007-08-01

    Sediments contain an abundance of microorganisms. However, the diversity and distribution of microorganisms associated with sediments are poorly understood, particularly in lacustrine environments. We used banding patterns from denaturing gradient gel electrophoresis (DGGE) and 16S rDNA sequences to assess the structure of bacterial communities in the Holocene sediments of a meromictic lake in Minnesota. Cluster analysis of the DGGE banding patterns indicates that the early- and middle-Holocene samples group separately from the late-Holocene samples. About 79% of the recovered bacterial sequences cluster with the alpha-, beta-, delta-, epsilon-, and gamma- Proteobacteriaceae and Firmicutes. The remaining approximately 21% lack cultured representatives. The taxonomic lineages of bacteria differ statistically among the early-, middle-, and late-Holocene samples, although the difference is smallest between early- and middle-Holocene samples. Early- and middle-Holocene samples are dominated by epsilon-Proteobacteriaceae, and late-Holocene samples are dominated by sequences from uncultured subphyla. We only recovered delta-Proteobacteriaceae in late-Holocene sediments and alpha- and gamma- Proteobacteriaceae in late- and middle-Holocene sediments. Diversity estimates derived from early-, middle-, and late-Holocene clone libraries indicate that the youngest (late-Holocene) samples had significantly greater bacterial diversity than the oldest (early-Holocene) samples, and the middle-Holocene samples contained intermediate levels of diversity. The observed patterns of diversity may be caused by increased bacterial niche-partitioning in younger sediments that contain a greater abundance of labile organic matter than older sediments.

  12. Coastal mapping handbook

    USGS Publications Warehouse

    ,; ,; Ellis, Melvin Y.

    1978-01-01

    Passage of the Coastal Zone Management Act of 1972 focused attention on the Nation's coastal land and water areas. As plans for more effective management of the coastal zone evolved, it soon became apparent that improved maps and charts of these areas were needed. This handbook was prepared with the requirements of the entire coastal community in mind, giving greatest attention to the needs of coastal zone managers and planners at the State and local levels. Its principal objective is to provide general information and guidance; it is neither a textbook nor a technical manual, but rather a primer on coastal mapping. This handbook should help planners and managers of coastal programs to determine their mapping requirements, select the best maps and charts for their particular needs, and to deal effectively with personnel who gather data and prepare maps. The sections on "Sources of Assistance and Advice" and "Product and Data Sources" should be especially useful to all involved in mapping the coastal zone. Brief summaries of the mapping efforts of several State coastal zone management programs are included. "Future outlook" discusses anticipated progress and changes in mapping procedures and techniques. Illustrations are inserted, where appropriate, to illustrate the products and equipment discussed. Because of printing restrictions, the colors in map illustrations may vary from those in the original publication. The appendixes include substantial material which also should be of interest. In addition a glossary and an index are included to provide easy and quick access to the terms and concepts used in the text. For those interested in more technical detail than is provided in this handbook, the "Selected references" will be useful. Also, the publications of the professional societies listed in appendix 4 will provide technical information in detail.

  13. Holocene relative sea levels of Bonaire (Leeward Antilles) - Evidence from circumlittoral sediment traps

    NASA Astrophysics Data System (ADS)

    Engel, Max; May, Simon Matthias; Brückner, Helmut

    2014-05-01

    Relative sea-level (RSL) rise in the near future represents one of the most serious coastal hazards worldwide, in particular in the Caribbean region where it may enhance negative effects from hurricane-induced flooding. RSL is a function of global (glacioeustasy, steric effect), regional (e.g. glacio-isostatic adjustment [GIA], gravitational effects inducing deformation of the earth, upper/lower mantle viscosity, etc.) and local (sediment compaction, tectonic uplift/subsidence) factors. Information on past RSL supports inferences on upper limits of ice shield ablation, estimates of anthropogenic contribution to historical and future RSL rise and calibration of rheological Earth models. We present the first Holocene RSL curve for the island of Bonaire in the southern Caribbean based on 42 14C datings from 20 sediment cores taken from nine different sedimentary archives along the coast. The sedimentary environment of each index point was linked to a palaeo-water depth based on literature and field observations. The index points trace a local RSL history of decelerating rise since 7000-6000 years ago and subsequent asymptotical approximation, similar to RSL curves from adjacent coasts of Curaςao and Venezuela. The results were compared to an existing reference model which considers global effects and regional GIA (including implications for geopotential). Even though the central and northwestern parts of Bonaire experienced slow tectonic uplift of up to 50 cm since the mid-Holocene and correction for compaction was applied, the new RSL curve for Bonaire runs slightly below the reference model which is probably due to sediment compaction in the investigated archives, collapse of cavities in the underlying limestone, or, at Boka Bartol, local-scale normal faulting (c. 1.5 mm/yr).

  14. Stone tools and foraging in northern Madagascar challenge Holocene extinction models

    PubMed Central

    Dewar, Robert E.; Radimilahy, Chantal; Wright, Henry T.; Jacobs, Zenobia; Kelly, Gwendolyn O.; Berna, Francesco

    2013-01-01

    Past research on Madagascar indicates that village communities were established about AD 500 by people of both Indonesian and East African heritage. Evidence of earlier visits is scattered and contentious. Recent archaeological excavations in northern Madagascar provide evidence of occupational sites with microlithic stone technologies related to foraging for forest and coastal resources. A forager occupation of one site dates to earlier than 2000 B.C., doubling the length of Madagascar’s known occupational history, and thus the time during which people exploited Madagascar’s environments. We detail stratigraphy, chronology, and artifacts from two rock shelters. Ambohiposa near Iharana (Vohémar) on the northeast coast, yielded a stratified assemblage with small flakes, microblades, and retouched crescentic and trapezoidal tools, probably projectile elements, made on cherts and obsidian, some brought more that 200 km. 14C dates are contemporary with the earliest villages. No food remains are preserved. Lakaton’i Anja near Antsiranana in the north yielded several stratified assemblages. The latest assemblage is well dated to A.D. 1050–1350, by 14C and optically stimulated luminescence dating and pottery imported from the Near East and China. Below is a series of stratified assemblages similar to Ambohiposa. 14C and optically stimulated luminescence dates indicate occupation from at least 2000 B.C. Faunal remains indicate a foraging pattern. Our evidence shows that foragers with a microlithic technology were active in Madagascar long before the arrival of farmers and herders and before many Late Holocene faunal extinctions. The differing effects of historically distinct economies must be identified and understood to reconstruct Holocene histories of human environmental impact. PMID:23858456

  15. Stone tools and foraging in northern Madagascar challenge Holocene extinction models.

    PubMed

    Dewar, Robert E; Radimilahy, Chantal; Wright, Henry T; Jacobs, Zenobia; Kelly, Gwendolyn O; Berna, Francesco

    2013-07-30

    Past research on Madagascar indicates that village communities were established about AD 500 by people of both Indonesian and East African heritage. Evidence of earlier visits is scattered and contentious. Recent archaeological excavations in northern Madagascar provide evidence of occupational sites with microlithic stone technologies related to foraging for forest and coastal resources. A forager occupation of one site dates to earlier than 2000 B.C., doubling the length of Madagascar's known occupational history, and thus the time during which people exploited Madagascar's environments. We detail stratigraphy, chronology, and artifacts from two rock shelters. Ambohiposa near Iharana (Vohémar) on the northeast coast, yielded a stratified assemblage with small flakes, microblades, and retouched crescentic and trapezoidal tools, probably projectile elements, made on cherts and obsidian, some brought more that 200 km. (14)C dates are contemporary with the earliest villages. No food remains are preserved. Lakaton'i Anja near Antsiranana in the north yielded several stratified assemblages. The latest assemblage is well dated to A.D. 1050-1350, by (14)C and optically stimulated luminescence dating and pottery imported from the Near East and China. Below is a series of stratified assemblages similar to Ambohiposa. (14)C and optically stimulated luminescence dates indicate occupation from at least 2000 B.C. Faunal remains indicate a foraging pattern. Our evidence shows that foragers with a microlithic technology were active in Madagascar long before the arrival of farmers and herders and before many Late Holocene faunal extinctions. The differing effects of historically distinct economies must be identified and understood to reconstruct Holocene histories of human environmental impact.

  16. Exceptional preservation of children's footprints from a Holocene footprint site in Namibia

    NASA Astrophysics Data System (ADS)

    Bennett, Matthew R.; Morse, Sarita A.; Liutkus-Pierce, Cynthia; McClymont, Juliet; Evans, Mary; Crompton, Robin H.; Francis Thackeray, J.

    2014-09-01

    Here we report on a Holocene inter-dune site close to Walvis Bay (Namibia) which contains exceptionally well-preserved children's footprints. The footprint surface is dated using Optically Stimulated Luminescence (OSL) methods to approximately 1.5 ka. These dates are compared to those obtained at nearby footprint sites and used to verify a model of diachronous footprint surfaces and also add to the archaeological data available for the communities that occupied these near-coastal areas during the Holocene. This model of diachronous footprint surfaces has implications for other soft-sediment footprint sites such as the 1.5 Ma old footprints at Ileret (Kenya). The distribution of both human and animal tracks, is consistent with the passage of small flock of small ungulates (probably sheep/goats) followed by a group of approximately 9 ± 2 individuals (children or young adults). Age estimates from the tracks suggest that some of the individuals may have been as young as five years old. Variation in track topology across this sedimentologically uniform surface is explained in terms of variations in gait and weight/stature of the individual print makers and is used to corroborate a model of footprint morphology developed at a nearby site. The significance of the site within the literature on human footprints lies in the quality of the track preservation, their topological variability despite a potentially uniform substrate, and the small size of the tracks, and therefore the inferred young age of the track-makers. The site provides an emotive insight into the life of the track-makers.

  17. Pleistocene to Holocene contrasts in organic matter production and preservation on the California continental margin

    USGS Publications Warehouse

    Dean, W.E.; Gardner, J.V.

    1998-01-01

    Organic matter in sediments from cores collected from the upper continental slope (200-2700 m) off California and southern Oregon shows marked differences in concentration and marine character between the last glacial interval (ca. 24-10 ka) and either Holocene time or last interstadial (oxygen isotope stage 3, ca. 60-24 ka). In general, sediments deposited during Holocene time and stage 3 contain higher amounts of marine organic matter than those deposited during the last glacial interval, and this contrast is greatest in cores collected off southern California. The most profound differences in stage 3 sediments are between predominantly bioturbated sediments and occasional interbeds of laminated sediments. The sediments are from cores collected within the present oxygen minimum zone on the upper continental slope from as far north as the Oregon-California border to as far south as Point Conception. These upper Pleistocene laminated sediments contain more abundant hydrogen-rich (type II) marine algal organic matter than even surface sediments that have large amounts of nonrefractory organic matter. The stable carbon-isotopic composition of the organic matter does not change with time between bioturbated and laminated sediments, indicating that the greater abundance of type II organic matter in the laminated sediments is not due to a change in source but rather represents a greater degree of production and preservation of marine organic matter. The presence of abundant, well-preserved organic matter supports the theory that the oxygen minimum zone in the northeastern Pacific Ocean was more intense, and possibly anoxic, during late Pleistocene time as a result of increased coastal upwelling that enhanced algal productivity.

  18. Alaskan transect links Holocene carbon shifts to peatland paleoecology and paleoclimate

    NASA Astrophysics Data System (ADS)

    Peteet, D. M.; Nichols, J. E.; Andreev, A.; McGeachy, A.; Perez, M.

    2011-12-01

    Arctic and subarctic peatlands are highly sensitive to climate shifts, and greenhouse warming is greatest at high latitudes. As high latitudes warm and peatlands provide positive and negative feedbacks in carbon sequestration, the paleo-perspective becomes critical in assessing future peatland stocks. We target a north-south (temperature) and east-west (moisture) transect of Alaskan peatlands using pollen and spores, plant macrofossils, charcoal, stable isotopes, and C/N coupled with carbon to explore the relationship of climate and vegetation shifts to carbon storage through time. Since deglaciation, peatlands have developed in a variety of maritime and continental subarctic and arctic environments with vegetation ranging from fens to bogs. Factors affecting the net carbon storage (productivity and decomposition) include the vegetation type, precipitation, temperature, bryophyte component, seasonality, snow history, fire history, and permafrost. New paleoecological records from three Holocene peatlands, each spanning at least 9000 years, include a continental boreal forest site, Goldmine Bog, Fairbanks, (65°N, 147°W), and maritime sites including Phalarope Bog, Kodiak (57°N, 154°W), and Bear Bog, Cordova (60°N, 145°W). Major shifts in moisture and temperature are evident throughout the Holocene from our multiproxy investigations of each site. Our data address several questions about subarctic/arctic carbon storage and climate, such as whether bogs or fens sequester more carbon, as this topic is intensely debated in the current literature. We also compare shifts in inferred moisture and temperature with carbon storage at each site, and with other coastal and interior sites for a fuller understanding of changes in the climate of this important region.

  19. Holocene Indian Ocean Cosmic Impacts: The Megatsunami Chevron Evidence From Madagascar

    NASA Astrophysics Data System (ADS)

    Masse, W.; Bryant, E.; Gusiakov, V.; Abbott, D.; Rambolamana, G.; Raza, H.; Courty, M.; Breger, D.; Gerard-Little, P.; Burckle, L.

    2006-12-01

    The 2.6 million year Quaternary period terrestrial physical record lacks definitive crater evidence for major regional catastrophic impacts by asteroids and comets other than the 10.5-km diameter Botsumtwi structure in Ghana and the 14.0-km diameter Zhamanshin structure in Kazakhstan [1] dating between about 900 and 1100 kya. Current cosmic impact rate models suggest that an average of between 3-6 globally catastrophic impacts should have occurred on the Earth during the Quaternary, along with several additional significant regional impacts in addition to Zhamanshin and Botsumtwi. These models and data indicate that the great majority of the "missing" major impact locations would likely have occurred in poorly studied oceanic settings. Only recently have Late Quaternary and Holocene period coastal paleo-megatsunami chevron deposits been defined in the Caribbean and along the western coasts of Australia, along with the suggestion that some may have been created by oceanic cosmic impacts in distinction to those caused by landslips, eruptions, and seismic events. We investigate the possibility that many or most megatsunami chevrons occurring along the southern coast of Madagascar were caused by two or more major Holocene Indian Ocean cosmic impacts. This hypothesis is based on an initial study of the worldwide archaeological and anthropological record, and the preliminary study of satellite images of the chevrons, selected Indian Ocean deep-sea cores, sea-floor bathymetry, and physical examination of the Madagascar deposits themselves. Candidate Indian Ocean impact structures are identified and correlated with the southern Madagascar megatsunami chevron deposits. [1] Masse, W.B. 2007 The Archaeology and Anthropology of Quaternary Period Cosmic Impact. In Bobrowsky, P.T. & Rickman, H. (eds.)Comets/Asteroid Impacts and Human Society. Springer, Berlin (in press).

  20. Holocene sedimentation in Richardson Bay, California

    USGS Publications Warehouse

    Connor, Cathy L.

    1983-01-01

    Examination of foraminifers, diatoms, ostracodes, clay mineralogy, and sediment-size variation from 9 borehole sites along the salt-marsh margins of Richardson Bay reveals a record of gradual infilling of fine-grained estuarine sediments. Over the past 10,000 years this area was transformed from a V-shaped Pleistocene stream valley to a flat-floored arm of the San Francisco Bay estuary. A radiocarbon date obtained from a basal peat overlying nonmarine alluvial sand near the town of Mill Valley indicates that stable salt-marsh vegetation was present in the northwestern arm of Richardson Bay 4600?165 years ago and agrees within error limits with a Holocene sea-level curve developed by Atwater, Hedel, and Helley in 1977 for southern San Francisco Bay. The average sedimentation rate over the last 4600 years is estimated to be 0.2 cm/yr for the inner part of the bay. Comparison of early maps with updated versions as well as studies of marsh plant zonations in disturbed and nondisturbed areas shows that almost half of the marsh in Richardson Bay has been leveed or filled since 1899.

  1. Late Holocene rainforest disturbance in French Guiana.

    PubMed

    Ledru, M -P.

    2001-06-01

    Palm swamp forest sediments collected in French Guiana provide new data about late Holocene rainforest. Two cores were collected in 'Les Nouragues' ecological station (4 degrees 05'N, 52 degrees 40'W). The lithology shows two different types of sediment, organic peat in the upper part and oxidized clay with low organic content and lacking pollen in the lower part, both separated by a gravel horizon. Radiocarbon dates show that this gravel horizon could have been deposited between 4500 and 3000yrBP. Pollen analysis carried out on the organic sediments record rainforest disturbances between ca 1520-1380 and 1060-860cal yrBP suggested by the presence of the pioneer tree species Cecropia together with other shade intolerant genera. Cecropia is recorded for a period that lasts between 660 and 320 years. This abnormal duration for presence of a pioneer species in rainforest is explained by brief and repeated changes in the composition of the canopy asssociated to perturbations of the palm swamp.

  2. Sedimentation Response to Holocene Landscape Disturbance on the Poverty Bay Continental Margin, East Coast New Zealand

    NASA Astrophysics Data System (ADS)

    Orpin, A. R.; Carter, L.; Alexander, C. R.; Kuehl, S. A.

    2004-12-01

    Since human settlement, dramatic landscape changes have occurred on the Raukumara Peninsula, East Coast North Island of New Zealand. In particular, European destruction of native forests for pasture caused accelerated erosion of the mudstone and sandstone dominated hinterland. Sediment eroded from the Raukumara Ranges is primarily carried by three small-catchment river systems, which collectively deliver approximately 70 Mt/y of suspended sediment, representing about 0.3% of total global input to the ocean. Today, the Waipaoa River delivers 15 Mt/y of mud to coastal Poverty Bay, accumulating in an actively subsiding mid-shelf basin and outer shelf lobe. The shelf is bordered along its seaward edge by two emergent ridges, but a significant component of hemipelagic sediment leaks through the 13 km-wide Poverty Gap between the ridges, and is deposited on the slope in a large structural indentation that is heavily incised by the Poverty submarine canyon system. Using Holocene tephrochronology, and accepting near-full capture of Holocene riverine sediment on the shelf and slope, accumulation rates indicate that the modern (post-colonisation) sediment input from the Waipaoa River is probably an order of magnitude higher than the average for the Holocene. Previous studies suggest that a five-times increase in accumulation rates by the early 1900's on the shelf is contemporaneous with deforestation. Modern sediment mass accumulation rates determined from excess 210Pb profiles suggest that shelf sedimentation increases seaward, reaching a maximum of 0.9 cm/y on the outer shelf, with no net accumulation apparent on the inner-middle shelf. In general, accumulation rates are an order of magnitude lower on the slope, around 0.1 cm/y, decreasing slightly down-slope. Palynological data show a succession of destruction of native forests by burning, extensive land clearance for pasture, and the establishment of exotic forests. These markers date the arrival of Polynesian settlers

  3. Reconstructing Mid- to Late Holocene sea-level change from coral microatolls, French Polynesia

    NASA Astrophysics Data System (ADS)

    Hallmann, N.; Camoin, G.; Eisenhauer, A.; Vella, C.; Samankassou, E.; Botella, A.; Milne, G. A.; Pothin, V.; Dussouillez, P.; Fleury, J.

    2016-12-01

    Coral microatolls are sensitive low-tide recorders, as their vertical accretion is limited by the mean low water springs level, and can be considered therefore as high-precision recorders of sea-level change. They are of pivotal importance to resolving the rates and amplitudes of millennial-to-century scale changes during periods of relative climate stability such as the Mid- to Late Holocene, which serves as an important baseline of natural variability prior to the industrial revolution. It provides therefore a unique opportunity to study coastal response to sea-level rise, even if the rates of sea-level rise during the Mid- to Late Holocene were lower than the current rates and those expected in the near future. Mid- to Late Holocene relative sea-level change in French Polynesia was reconstructed based on the coupling between absolute U/Th dating of in situ coral microatolls and their precise positioning via GPS RTK (Real Time Kinematic) measurements. The twelve studied islands represent ideal settings for accurate sea-level studies because: 1) they can be regarded as tectonically stable during the relevant period (slow subsidence), 2) they are located far from former ice sheets (far-field), 3) they are characterized by a low tidal amplitude, and 4) they cover a wide range of latitudes which produces significantly improved constraints on GIA (Glacial Isostatic Adjustment) model parameters. A sea-level rise of less than 1 m is recorded between 6 and 3-3.5 ka, and is followed by a gradual fall in sea level that started around 2.5 ka and persisted until the past few centuries. In addition, growth pattern analysis of coral microatolls allows the reconstruction of low-amplitude, high-frequency sea-level change on centennial to sub-decadal time scales. The reconstructed sea-level curve extends the Tahiti last deglacial sea-level curve [Deschamps et al., 2012, Nature, 483, 559-564], and is in good agreement with a geophysical model tuned to fit far-field deglacial

  4. Reconstructing Mid- to Late Holocene sea-level change from coral microatolls, French Polynesia

    NASA Astrophysics Data System (ADS)

    Hallmann, Nadine; Camoin, Gilbert; Eisenhauer, Anton; Botella, Alberic; Milne, Glenn; Vella, Claude; Samankassou, Elias; Pothin, Virginie; Dussouillez, Philippe; Fleury, Jules; Fietzke, Jan

    2017-04-01

    Coral microatolls are sensitive low-tide recorders, as their vertical accretion is limited by the mean low water springs level, and can be considered therefore as high-precision recorders of sea-level change. They are of pivotal importance to resolving the rates and amplitudes of millennial-to-century scale changes during periods of relative climate stability such as the Mid- to Late Holocene, which serves as an important baseline of natural variability prior to the industrial revolution. It provides therefore a unique opportunity to study coastal response to sea-level rise, even if the rates of sea-level rise during the Mid- to Late Holocene were lower than the current rates and those expected in the near future. Mid- to Late Holocene relative sea-level change in French Polynesia was reconstructed based on the coupling between absolute U/Th dating of in situ coral microatolls and their precise positioning via GPS RTK (Real Time Kinematic) measurements. The twelve studied islands represent ideal settings for accurate sea-level studies because: 1) they can be regarded as tectonically stable during the relevant period (slow subsidence), 2) they are located far from former ice sheets (far-field), 3) they are characterized by a low tidal amplitude, and 4) they cover a wide range of latitudes which produces significantly improved constraints on GIA (Glacial Isostatic Adjustment) model parameters. A step-like sea-level rise is evidenced between 6 and 3.9 ka leading to a short sea-level highstand of about a meter in amplitude between 3.9 and 3.6 ka. A sea-level fall, at an average rate of 0.3 mm.yr-1, is recorded between 3.6 and 1.2 ka when sea level approached its present position. In addition, growth pattern analysis of coral microatolls allows the reconstruction of low-amplitude, high-frequency sea-level change on centennial to sub-decadal time scales. The reconstructed sea-level curve extends the Tahiti last deglacial sea-level curve [Deschamps et al., 2012, Nature

  5. Holocene Deglaciation of the Scandinavian Ice Sheet: Preliminary 10Be Ages

    NASA Astrophysics Data System (ADS)

    Cuzzone, J. K.; Clark, P. U.; Marcott, S. A.; Lunkka, J.; Wohlfarth, B.; Caffee, M. W.; Carlson, A. E.

    2013-12-01

    The response of ice sheets to a warming climate is not well understood. Because we are limited in our understanding of present dynamics, reconstructing the deglaciation of former ice sheets allows for a better understanding of how past ice sheets responded to a warming climate along with their contribution to sea-level rise. These reconstructions also serve as critical constraints for ice sheet modeling efforts. Here, we present a suite of new 10Be ages from erratic boulders along three transects spanning southern to northern Sweden and Finland, that improve our understanding of the deglaciation of the Scandinavian Ice Sheet (SIS) beginning ~ 11.7ka through its final demise during the early Holocene. Dates from southern Finland, beginning at the Salpausselka Younger Dryas moraine (11.5 × 0.7 ka, n=4), inland southern Finland near Jyvaskyla (11.5 × 0.5ka, n=2), and coastal Finland (~60km from Gulf of Bothnia) near Vimpeli (11.5 × 0.4ka, n=4) indicate a rapid retreat following the Younger Dryas for Southern Finland (~500km within uncertainty of ages). Preliminary dates also exist for Northern Finland, near Inari (10.8 × 0.5ka, n=4) and near Oulu (10.5 × 0.6 ka, n = 4) suggesting a later retreat in the north. Dates from southern Sweden, near Skovde (12.73 × 0.8ka, n=4) to Mora (10.41 × 0.6ka, n=5) suggest a slower retreat (over ~400km). Lastly, dates in Northwestern Sweden suggest a final termination of the SIS around 9.4 × 0.7ka (n = 3). Additional ages are now being processed at PRIME Lab, Purdue University, which will further strengthen our understanding of SIS retreat from all sampled sites. These new data will help to constrain the Holocene deglaciation of the SIS and its associated retreat rates, and establish the SIS contribution to Holocene sea level rise, which will improve our understanding of ice-sheet response to a warming climate.

  6. Persistence of ENSO-Like Climate Variability Throughout the Holocene

    NASA Astrophysics Data System (ADS)

    Asmerom, Y.; Polyak, V. J.; Rasmussen, J. B.; Burns, S. J.; Lachniet, M. S.

    2005-12-01

    The El Niño Southern Oscillation (ENSO) is a Pacific climate phenomenon with global climate teleconnections. Many aspects of the modern ENSO regime are unknown, and its persistence and modalities in the past are even less known. In continents, the main difficulty has been finding ENSO-sensitive proxies with near-annual resolution that are datable by isotopic techniques. Speleothems from ENSO-influenced regions, such as the Southwestern USA (SW), offer new opportunities. In the SW, El Niño years are typically wetter and La Niña years drier than normal. ENSO teleconnections with precipitation are especially strong when the SOI and NINO3 are out-of-phase during negative phases of the Pacific Decadal Oscillation (PDO) (1). Data from uranium-series dated late Holocene speleothems from southern New Mexico and an early Holocene-Pleistocene speleothem from the Grand Canyon (Arizona) are used to investigate ENSO variability during the Pleistocene-early Holocene as compared to the Late Holocene. It has been previously suggested that frequency and magnitude of ENSO has changed since the early Holocene (e.g. 2). Our data consist of growth thickness variations of annual bands for the late Holocene and gray scale and stable isotopic data for the early Holocene and the Pleistocene-Holocene transition. Previously we had demonstrated that growth thickness in our annually-banded speleothems is related to precipitation (3). Gray scale in our Grand Canyon speleothem is well-correlated with δ18O isotopic values (R = -0.63). Dark bands, which we interpret to represent arid years, correlate with high δ18O values. Multiple-taper spectral (MTM) and wavelet analyses of the late Holocene data show statistically significant (above 90% confidence) peaks at interannual (2-6 yr) timescales in addition to decadal and centennial frequencies throughout the record, which we suggest represent PDO and solar modulators. The prominent interannual frequencies in our datalikely reflect the

  7. Maximum-limiting ages of Lake Michigan coastal dunes: Their correlation with Holocene lake level history

    USGS Publications Warehouse

    Arbogast, Alan F.; Loope, Walter L.

    1999-01-01

    At each site, thick deposits of eolian sand overlie late-Pleistocene lacustrine sands. Moderately developed Spodosols (Entic Haplorthods) formed in the uppermost part of the lake sediments are buried by thick dune sand at three sites. At the fourth locality, a similar soil occurs in a very thin (1.3 m) unit of eolian sand buried deep within a dune. These soils indicate long-term (∼ 4,000 years) stability of the lake deposits following subaerial exposure. Radiocarbon dating of charcoal in the buried sola indicates massive dune construction began between 4,900 and 4,500 cal. yr B.P. at the Nordhouse Dunes site, between 4,300 and 3,900 cal. yr B.P. at the Jackson and Nugent Quarries, and between 3,300 to 2,900 cal. yr B.P. at Rosy Mound. Given these ages, it can be concluded that dune building at one site occurred during the Nipissing high stand but that the other dunes developed later. Although lake levels generally fell after the Nipissing, it appears that dune construction may have resulted from small increases in lake level and destabilization of lake-terrace bluffs.

  8. The Holocene environmental history of a small coastal lake on the north-eastern Kamchatka Peninsula

    NASA Astrophysics Data System (ADS)

    Solovieva, N.; Klimaschewski, A.; Self, A. E.; Jones, V. J.; Andrén, E.; Andreev, A. A.; Hammarlund., D.; Lepskaya, E. V.; Nazarova, L.

    2015-11-01

    A radiocarbon and tephra-dated sediment core from Lifebuoy Lake, located on the north-east coast of Kamchatka Peninsula, was analysed for pollen, spores, diatoms, chironomids and tephra in order to uncover regional environmental history. The 6500-year environmental history of Lifebuoy Lake correlates with the broad regional patterns of vegetation development and climate dynamics with both diatoms and chironomids showing near-synchronous changes. Between ca. 6300 and 3900 cal yr BP, the lake ecosystem was naturally enriched, with several Stephanodiscus species dominating the diatom plankton. This natural eutrophication state is likely to be due to a combination of the base-rich catchment geology, the fertilisation effect of several fires in the catchment, silica input from tephra layers and, possibly, nitrogen input from seabirds. The substantial tephra deposit at about 3850 cal yr BP might have stopped sedimentary phosphorus from entering the lake water thus decreasing the trophic state of the lake and facilitating the shift in diatom composition to a benthic Fragiliariaceae complex. Both diatoms and chironomids showed simultaneous compositional changes, which are also reflected by statistically significant changes in their rates of change 300-400 years after the arrival of Pinus pumila in the lake catchment. The rapid increase in both total diatom concentration and the percentage abundance of the large heavy species, Aulacoseira subarctica might be a response to the change in timing and intensity of lake spring turn-over due to the changes in the patterns of North Pacific atmospheric circulation, most notably westward shift of the Aleutian Low. The two highest peaks in A. subarctica abundance at Lifebouy Lake occurred during opposite summer temperature inferences: the earlier peak (3500-2900 cal yr BP) coincided with warm summers and the latter peak (300 cal yr BP-present) occurred during the cold summer period. These imply that A. subarctica shows no direct response to the changes of summer air temperature. Instead, it appears to thrive during the periods of increased winter precipitation, thicker ice and late spring turn-over periods, i.e., shows indirect response to climate. The clearest effect of tephra deposition on the lake ecosystem is above 908 cm (ca. 3800 cal yr BP) where the tephra deposit might have caused the shift from Stephanodiscus-dominated planktonic assemblages to the Fragilariaceae complex of benthic species. Tephra deposits might have also contributed towards the development of eutrophic plankton from about 6300 cal yr BP. It is not certain if several tephra deposits influenced diatom and chironomid changes during the last 300 years.

  9. Evidence for latest Pleistocene to Holocene uplift at the southern margin of the Central Anatolian Plateau (CAP), southern Turkey

    NASA Astrophysics Data System (ADS)

    Cosentino, Domenico; Öǧretmen, Nazik; Cipollari, Paola; Gliozzi, Elsa; Radeff, Giuditta; Yıldırım, Cengiz; Baykara, Oruc M.; Shen, Chuan-Chou

    2016-04-01

    Along the Mediterranean coastal area of southern Anatolia, markers of ancient sea-level have been reported west of Alanya and east of the Göksu delta. In both areas, bioconstructed fossil rims, consisting mainly of calcareous algae, are situated 0.5 m above the live counterpart. The fossil rim to the west of Alanya has been dated between 2690 to 1545 yrs BP, evidencing late Holocene rock uplift at the CAP southern margin. More recently, based on beachrocks along the coastal area from Incekum to the south of Adana, authors showed that the shoreline was raised around 0.5 m after 19 BC-200 AD. Based on new field observations along the coast between Aydı ncı k and Ayaş (Mersin, southern Turkey), together with AMS 14C dating and high-resolution U-Th chronology, a more complex uplift history can be suggested. Along the coast of Yeşilovacı k, we observed up to seven uplifted marine notches, from 0.5 m to 6.10 m above sea level. Some of them show relationships with a travertine crust that yielded U-Th ages of 2727 ± 1559 years and 5236 ± 2255 years. In the same area, a calcareous algae fossil trottoir related to a marine notch 5.40 m above sea level yielded an AMS 14C 2σ age of 32700 to 31645 years cal BP. Considering that the global ocean was 60 m below the present sea level at 32 ka, the Yeşilovacı k coastal area has been uplifted at 2 mm/yr. Moving to the east, in a small embayment at Eǧribük, two distinct well cemented beach deposits containing Murex brandaris, Cerithium vulgatum, and Columbella rustica have been uplifted at 0.3 m and 0.7 m above the present sea level. Although it is difficult to reconstruct the paleodepth of those beach deposits, AMS 14C 2σ ages of 5575 to 5445 years cal BP and 2130 to 1965 years cal BP show late Holocene uplift. In the Narlı kuyu area, up to seven different uplifted markers of sea level were observed between 0.8 and 7.2 m above the present sea level. In addition, near Ayaş new insights for late Holocene uplift are

  10. Coastal Chile Perspective View

    NASA Image and Video Library

    2010-03-04

    This perspective view from NASA Shuttle Radar Topography Mission of coastal Chile indicates the epicenter red marker of the 8.8 earthquake on Feb. 27, 2010, just offshore of the Maule region in the Bahia de Chanco.

  11. National Coastal Condition Assessment

    EPA Pesticide Factsheets

    The NCCA is a collaborative, statistical survey of the nation's coastal waters and the Great Lakes. It is one of four national surveys that EPA and its partners conduct to assess the condition and health of the nation's water resources.

  12. Clinal variation of some mammals during the Holocene in Missouri

    NASA Astrophysics Data System (ADS)

    Purdue, James R.

    1980-03-01

    Eastern cottontail ( Sylvilagus floridanus), fox squirrel ( Sciurus niger), and gray squirrel ( Sciurus carolinensis) were examined for clinal variation during the Holocene. Modern samples of all three species displayed strong east-west patterns along the western edge of the eastern deciduous forest: S. floridanus and S. niger decrease and S. carolinensis increases in size. Archeological samples of S. carolinensis from Rodgers Shelter (23BE125), Benton County, Missouri, and Graham Cave (23MT2), Montgomery County, Missouri, indicated an increase in size from early to middle Holocene. Sylvilagus floridanus from Rodgers Shelter decreased in size from early to middle Holocene and then increased during the late Holocene to modern proportions. A literature survey reveals that clinal variation is a common phenomenon among modern homeotherms. In introduced species, clinal variation has developed after relatively few generations, indicating rapid adaptations to environmental conditions; often winter climatic variables are implicated. Morphological variation in the study species during the Holocene is interpreted as a response to changing climates. Studies of morphological clines may lead to another valuable data source for reconstructing past ecologies.

  13. Evaluation of Holocene pollen records from the Romanian Plain.

    PubMed

    Tomescu

    2000-05-01

    This study is a critical review of pollen analyses carried out on Holocene sequences from 15 sites in and near the Romanian Plain. Three sites come from natural sediments, 10 sites are from anthropogenic deposits and two are from both anthropogenic and natural settings. The general reconstruction is of a steppe-forest-steppe vegetation through the Holocene. The nature of the deposits, however, casts doubts on this reconstruction. Deposits of archaeological sites generally yield pollen spectra that are influenced by human activities and thus unsuitable for vegetation reconstructions. Loess deposits are also unfavorable for pollen preservation because of high pH and porosity. Consequently, pollen spectra from loess deposits are strongly biased by selective pollen destruction. Research and experiments carried out by several authors suggest that spectra dominated by Asteraceae, Poaceae, Chenopodiaceae or Pinus pollen in soils and loess are a result of selective pollen destruction, especially if low pollen concentrations, progressive pollen deterioration or high frequencies of deteriorated or unidentifiable pollen are evidenced. The fact that pollen records from the Romanian Plain come from loess, alkaline peat or archaeological sites reduces their reliability for reconstructions of vegetation. The vegetation history of similar regions in Hungary, Bulgaria and Turkey suggests that early Holocene steppe vegetation was gradually replaced by forest or forest-steppe vegetation in the late Holocene. Records from lake sediments are required to find out whether the Holocene vegetation history of the Romanian Plain was similar.

  14. Seawater isotope constraints on tropical hydrology during the Holocene

    NASA Astrophysics Data System (ADS)

    Oppo, Delia W.; Schmidt, Gavin A.; LeGrande, Allegra N.

    2007-07-01

    Paleoceanographic data from the low latitude Pacific Ocean provides evidence of changes in the freshwater budget and redistribution of freshwater within the basin during the Holocene. Reconstructed Holocene seawater δ 18O changes compare favorably to differences predicted between climate simulations for the middle Holocene (MH) and for the pre-Industrial late Holocene (LH). The model simulations demonstrate that changes in the tropical hydrologic cycle affect the relationship between δ 18Osw and surface salinity, and allow, for the first time, quantitative estimates of western Pacific salinity change during the Holocene. The simulations suggest that during the MH, the mean salinity of the Pacific was higher because less water vapor was transported from the Atlantic Ocean and more was transported to the Indian Ocean. The salinity of the western Pacific was enhanced further due both to the greater advection of salt to the region by ocean currents and to an increase in continental precipitation at the expense of maritime precipitation, the latter a consequence of the stronger Asian summer monsoon.

  15. Parasitic diversity found in coprolites of camelids during the Holocene.

    PubMed

    Taglioretti, Verónica; Fugassa, Martín Horacio; Sardella, Norma Haydée

    2015-07-01

    Knowledge of parasitic infections to which fauna was exposed in the past provides information on the geographical origin of some parasites, on the possible dispersal routes and for archaeological fauna on the potential zoonotic risk that human and animal populations could be exposed. The aim of the present study was to examine the gastrointestinal parasite present in camelid coprolites collected from the archaeological site Cerro Casa de Piedra, cave 7 (CCP7), Patagonia, Argentina. Coprolites were collected from different stratified sequences dating from the Pleistocene-Holocene transition to the late Holocene. Paleoparasitological examination revealed the presence of eggs of Trichostrongylidae attributed to Lamanema chavezi or Nematodirus lamae, eggs of three unidentified capillariids, Strongylus-type eggs and oocysts of Eimeria macusaniensis. These parasites affected camelids living in the studied area since the Pleistocene-Holocene transition, about 10,000 years ago. Gastrointestinal parasite fauna of patagonian camelids did not vary significatively from Pleistocene-Holocene transition to late Holocene, although environmental conditions fluctuated greatly throughout this period, as indicative of the strength and the stability of these associations over time. In this study, the zoonotic and biogeography importance of parasites of camelids are also discussed.

  16. ‘Cape capture’: Geologic data and modeling results suggest the Holocene loss of a Carolina Cape

    USGS Publications Warehouse

    Thieler, E. Robert; Ashton, Andrew D.

    2011-01-01

    For more than a century, the origin and evolution of the set of cuspate forelands known as the Carolina Capes—Hatteras, Lookout, Fear, and Romain—off the eastern coast of the United States have been discussed and debated. The consensus conceptual model is not only that these capes existed through much or all of the Holocene transgression, but also that their number has not changed. Here we describe bathymetric, lithologic, seismic, and chronologic data that suggest another cape may have existed between Capes Hatteras and Lookout during the early to middle Holocene. This cape likely formed at the distal end of the Neuse-Tar-Pamlico fluvial system during the early Holocene transgression, when this portion of the shelf was flooded ca. 9 cal (calibrated) kyr B.P., and was probably abandoned by ca. 4 cal kyr B.P., when the shoreline attained its present general configuration. Previously proposed mechanisms for cape formation suggest that the large-scale, rhythmic pattern of the Carolina Capes arose from a hydrodynamic template or the preexisting geologic framework. Numerical modeling, however, suggests that the number and spacing of capes can be dynamic, and that a coast can self-organize in response to a high-angle-wave instability in shoreline shape. In shoreline evolution model simulations, smaller cuspate forelands are subsumed by larger neighbors over millennial time scales through a process of ‘cape capture.’ The suggested former cape in Raleigh Bay represents the first interpreted geological evidence of dynamic abandonment suggested by the self-organization hypothesis. Cape capture may be a widespread process in coastal environments with large-scale rhythmic shoreline features; its preservation in the sedimentary record will vary according to geologic setting, physical processes, and sea-level history.

  17. The Holocene deglaciation of the Byers Peninsula (Livingston Island, Antarctica) based on the dating of lake sedimentary records

    NASA Astrophysics Data System (ADS)

    Oliva, M.; Antoniades, D.; Giralt, S.; Granados, I.; Pla-Rabes, S.; Toro, M.; Liu, E. J.; Sanjurjo, J.; Vieira, G.

    2016-05-01

    The process of deglaciation in the Antarctic Peninsula region has large implications for the geomorphological and ecological dynamics of the ice-free environments. However, uncertainties still remain regarding the age of deglaciation in many coastal environments, as is the case in the South Shetland Islands. This study focuses on the Byers Peninsula, the largest ice-free area in this archipelago and the one with greatest biodiversity in Antarctica. A complete lacustrine sedimentary sequence was collected from five lakes distributed along a transect from the western coast to the Rotch Dome glacier front: Limnopolar, Chester, Escondido, Cerro Negro and Domo lakes. A multiple dating approach based on 14C, thermoluminescence and tephrochronology was applied to the cores in order to infer the Holocene environmental history and identify the deglaciation chronology in the Byers Peninsula. The onset of the deglaciation started during the Early Holocene in the western fringe of the Byers Peninsula according to the basal dating of Limnopolar Lake (ca. 8.3 cal. ky BP). Glacial retreat gradually exposed the highest parts of the Cerro Negro nunatak in the SE corner of Byers, where Cerro Negro Lake is located; this lake was glacier-free since at least 7.5 ky. During the Mid-Holocene the retreat of the Rotch Dome glacier cleared the central part of the Byers plateau of ice, and Escondido and Chester lakes formed at 6 cal. ky BP and 5.9 ky, respectively. The dating of the basal sediments of Domo Lake suggests that the deglaciation of the current ice-free easternmost part of the Byers Peninsula occurred before 1.8 cal. ky BP.

  18. Holocene Climate and Catchment-Specific Responses to Climate Change, Recorded in a Transect of Icelandic Lakes

    NASA Astrophysics Data System (ADS)

    Geirsdottir, A.; Axford, Y.; Florian, C. R.; Miller, G. H.; Crump, S. E.; Larsen, D. J.; Olafsdóttir, S.; Thordarson, T.; Blair, C.

    2015-12-01

    Holocene paleoclimate reconstructions from the northern North Atlantic landmasses exhibit greater responses to climate forcings than other Arctic regions presumably tied to changes in North Atlantic ocean-atmosphere circulation. Here we present an overview of high-resolution, precisely dated and PSV synchronized Holocene lake sediment records on Iceland, where we employ diverse proxies at sites spanning a broad modern climate gradient, from the presently glaciated highlands to the coastal lowlands. Despite substantial differences in catchment specific processes that influence each lake record, the multi-proxy reconstructions over the last 10 ka show remarkably consistent trends, especially throughout the mid to late Holocene cooling related to the slow decrease in summer insolation. Of particular note are highly non-linear abrupt departures of centennial scale summer cold periods such as at 5.5 ka, ~4.2 ka; ~3.0 ka, ~1.5 ka, 0.7 ka, and 0.2 ka. Some of the abrupt shifts may be related to Icelandic volcanism influencing catchment stability, but the lack of a full recovery to pre-existing values after the perturbation suggests increased periglacial activity, decreased vegetation cover, and glacier growth in Iceland. That these shifts reflect regional climate changes is also supported by contemporaneous shifts documented elsewhere in the northern North Atlantic region. Although timing and abruptness of these shifts is similar between our Icelandic lake records, their magnitude can differ substantially. Regional-scale factors such as volcanism likely modulate climatic responses to radiative forcing; and at the same time, local watershed characteristics like vegetation cover and soil properties produce site-specific environmental responses to climate change. Our Icelandic lake records provide opportunities to observe the precise timing of local climate shifts and corresponding environmental responses, and thus to disentangle these effects.

  19. Indian monsoon variations during three contrasting climatic periods: The Holocene, Heinrich Stadial 2 and the last interglacial-glacial transition

    NASA Astrophysics Data System (ADS)

    Zorzi, Coralie; Sanchez Goñi, Maria Fernanda; Anupama, Krishnamurthy; Prasad, Srinivasan; Hanquiez, Vincent; Johnson, Joel; Giosan, Liviu

    2015-10-01

    In contrast to the East Asian and African monsoons the Indian monsoon is still poorly documented throughout the last climatic cycle (last 135,000 years). Pollen analysis from two marine sediment cores (NGHP-01-16A and NGHP-01-19B) collected from the offshore Godavari and Mahanadi basins, both located in the Core Monsoon Zone (CMZ) reveals changes in Indian summer monsoon variability and intensity during three contrasting climatic periods: the Holocene, the Heinrich Stadial (HS) 2 and the Marine Isotopic Stage (MIS) 5/4 during the ice sheet growth transition. During the first part of the Holocene between 11,300 and 4200 cal years BP, characterized by high insolation (minimum precession, maximum obliquity), the maximum extension of the coastal forest and mangrove reflects high monsoon rainfall. This climatic regime contrasts with that of the second phase of the Holocene, from 4200 cal years BP to the present, marked by the development of drier vegetation in a context of low insolation (maximum precession, minimum obliquity). The historical period in India is characterized by an alternation of strong and weak monsoon centennial phases that may reflect the Medieval Climate Anomaly and the Little Ice Age, respectively. During the HS 2, a period of low insolation and extensive iceberg discharge in the North Atlantic Ocean, vegetation was dominated by grassland and dry flora indicating pronounced aridity as the result of a weak Indian summer monsoon. The MIS 5/4 glaciation, also associated with low insolation but moderate freshwater fluxes, was characterized by a weaker reduction of the Indian summer monsoon and a decrease of seasonal contrast as recorded by the expansion of dry vegetation and the development of Artemisia, respectively. Our results support model predictions suggesting that insolation changes control the long term trend of the Indian monsoon precipitation, but its millennial scale variability and intensity are instead modulated by atmospheric

  20. Indian monsoon variations during three contrasting climatic periods: the Holocene, Heinrich Stadial 2 and the last interglacial-glacial transition

    NASA Astrophysics Data System (ADS)

    Zorzi, Coralie; Fernanda Sanchez Goñi, Maria; Anupama, Krishnamurthy; Prasad, Srinivasan; Hanquiez, Vincent; Johnson, Joel; Giosan, Liviu

    2016-04-01

    In contrast to the East Asian and African monsoons the Indian monsoon is still poorly documented throughout the last climatic cycle (last 135,000 years). Pollen analysis from two marine sediment cores (NGHP-01-16A and NGHP-01-19B) collected from the offshore Godavari and Mahanadi basins, both located in the Core Monsoon Zone (CMZ) reveals changes in Indian summer monsoon variability and intensity during three contrasting climatic periods: the Holocene, the Heinrich Stadial (HS) 2 and the Marine Isotopic Stage (MIS) 5/4 during the ice sheet growth transition. During the first part of the Holocene between 11,300 and 4,200 cal years BP, characterized by high insolation (minimum precession, maximum obliquity), the maximum extension of the coastal forest and mangrove reflects high monsoon rainfall. This climatic regime contrasts with that of the second phase of the Holocene, from 4,200 cal years BP to the present, marked by the development of drier vegetation in a context of low insolation (maximum precession, minimum obliquity). The historical period in India is characterized by an alternation of strong and weak monsoon centennial phases that may reflect the Medieval Climate Anomaly and the Little Ice Age, respectively. During the HS 2, a period of low insolation and extensive iceberg discharge in the North Atlantic Ocean, vegetation was dominated by grassland and dry flora indicating pronounced aridity as the result of a weak Indian summer monsoon. The MIS 5/4 glaciation, also associated with low insolation but moderate freshwater fluxes, was characterized by a weaker reduction of the Indian summer monsoon and a decrease of seasonal contrast as recorded by the expansion of dry vegetation and the development of Artemisia, respectively. Our results support model predictions suggesting that insolation changes control the long term trend of the Indian monsoon precipitation, but its millennial scale variability and intensity are instead modulated by atmospheric

  1. Migrating Seals on Shifting Sands: Testing Alternate Hypotheses for Holocene Ecological and Cultural Change on the California Coast

    NASA Astrophysics Data System (ADS)

    Koch, P. L.; Newsome, S. D.; Gifford-Gonzalez, D.

    2001-12-01

    The coast of California presented Holocene humans with a diverse set of ecosystems and geomorphic features, from large islands off a semi-desert mainland in the south, to a mix of sandy and rocky beaches abutting grassland and oak forest in central California, to a rocky coast hugged by dense coniferous forest in the north. Theories explaining trends in human resource use, settlement patterns, and demography are equally diverse, but can be categorized as 1) driven by diffusion of technological innovations from outside the region, 2) driven by population growth leading to more intensive extraction of resources, or 3) driven by climatic factors that affect the resource base. With respect to climatic shifts, attention has focused on a possible regime shift ca. 5500 BP, following peak Holocene warming, and on evidence for massive droughts and a drop in marine productivity ca. 1000 BP. While evidence for a coincidence between climatic, cultural, and ecological change is present, albeit complex, in southern California, similar data are largely lacking from central and northern California. We are using isotopic and archaeofaunal analysis to test ideas for ecological and cultural change in central California. Three features of the archaeological record are relevant. First, overall use of marine resources by coastal communities declined after 1000 BP. Second, northern fur seals, which are common in earlier sites, drop in abundance relative to remaining marine animals. We have previously established that Holocene humans in central California were hunting gregariously-breeding northern fur seals from mainland rookeries. These seals breed exclusively on offshore islands today, typically at high latitudes. Their restriction to these isolated sites today may be a response to human overexploitation of their mainland rookeries prehistorically. Finally, collection of oxygen and carbon isotope data from mussels at the archaeological sites, while still in a preliminary phase, has

  2. Groundwater quality in the Coastal Los Angeles Basin, California

    USGS Publications Warehouse

    Fram, Miranda S.; Belitz, Kenneth

    2012-01-01

    The Coastal Los Angeles Basin study unit is approximately 860 square miles and consists of the Santa Monica, Hollywood, West Coast, Central, and Orange County Coastal Plain groundwater basins (California Department of Water Resources, 2003). The basins are bounded in part by faults, including the Newport-Inglewood fault zone, and are filled with Holocene-, Pleistocene-, and Pliocene-age marine and alluvial sediments. The Central Basin and Orange County Coastal Plain are divided into a forebay zone on the northeast and a pressure zone in the center and southwest. The forebays consist of unconsolidated coarser sediment, and the pressure zones are characterized by lenses of coarser sediment divided into confined to semi-confined aquifers by lenses of finer sediments. The primary aquifer system in the study unit is defined as those parts of the aquifer system corresponding to the perforated intervals of wells listed in the California Department of Public Health (CDPH) database of public-supply wells. The majority of public-supply wells are drilled to depths of 510 to 1,145 feet, consist of solid casing from the land surface to a depth of about 300 to 510 feet, and are perforated below the solid casing. Water quality in the primary aquifer system may differ from that in the shallower and deeper parts of the aquifer systems.

  3. High Arctic Paraglacial Coastal Evolution in Northern Billefjorden, Svalbard

    NASA Astrophysics Data System (ADS)

    Strzelecki, Matt; Long, Antony; Lloyd, Jerry

    2013-04-01

    Most sediment budget studies in paraglacial, High Arctic, environments have focussed attention on quantifying sediment fluxes in glacial and fluvial catchments. In contrast, little attention has been paid to the functioning of the paraglacial coastal zone with existing models of coastal change based on relict systems developed in mid latitude settings. The pristine coasts of Spitsbergen provided a superb opportunity to quantify how High Arctic coasts are respondingto rapid climate warming and associated paraglacial landscape transformation. In this paper we reconstruct the development of the paraglacial coasts in Petuniabukta and Adolfbukta, the northernmost bays of Billefjorden, central Spitsbergen. The study area is characterized by a sheltered location, a semi-arid, sub-polar climate, limited wave fetch and tidal range, and rapid retreat of all surrounding glaciers. Using a combination of geomorphological, sedimentological, remote sensing and dating methods, we study the processes controlling the coastal zone development over annual, century and millennial timescales. Interannual changes observed between 2008-2010 show that gravel barriers in the study area are resilient to the impacts of local storms and the operation of sea-ice processes. In general, the processes controlling the short-term barrier development often operate in the opposite direction to the landforming patterns visible in the longer-term evolution. Over multi-decadal timescales, since the end of the Little Ice Age. we observe drammatic changes in sediment flux and coastal response under an interval characterised by a warming climate, retreating local ice masses, a shortened winter sea-ice season and melting permafrost. A new approach of dating juvenile mollusc found in uplifted marine barriers led to the better understating of the Late Holocene evolution of a Petuniabukta coastal zone and its reaction to deglaciation, glacioisostatic uplift and sea-level fluctuations. We propose a new

  4. Late Holocene Hurricane Activity in the Gulf of Mexico from a Bayou Sediment Archive

    NASA Astrophysics Data System (ADS)

    Rodysill, J. R.; Donnelly, J. P.; Toomey, M.; Sullivan, R.; MacDonald, D.; Evans, R. L.; Ashton, A. D.

    2012-12-01

    Hurricanes pose a considerable threat to coastal communities along the Atlantic seaboard and in the Gulf of Mexico. The complex role of ocean and atmospheric dynamics in controlling storm frequency and intensity, and how these relationships could be affected by climate change, remains uncertain. To better predict how storms will impact coastal communities, it is vital to constrain their past behavior, in particular how storm frequency and intensity and the pattern of storm tracks have been influenced by past climate conditions. In an effort to characterize past storm behavior, our work contributes to the growing network of storm records along the Atlantic and Gulf coasts by reconstructing storm-induced deposits in the northern Gulf of Mexico during the Late Holocene. Previous work on the northern Gulf coast has shown considerable centennial-scale variability in the occurrence of intense hurricanes, much like the northern Atlantic coast and in the Caribbean Sea. The timing of active and quiet intervals during the last 1000 years amongst the Gulf Coast records appears to be anti-phased with stormy intervals along the North American east coast. The sparse spatial coverage of the existing intense hurricane reconstructions provides a limited view of the natural variability of intense hurricanes. A new, high resolution reconstruction of storms along the northern Gulf Coast would be beneficial in assembling the picture of the patterns of storminess during the Late Holocene. Our study site, Basin Bayou, is situated on the north side of Choctawhatchee Bay in northwest Florida. From 1851 to 2011, 68 storms have struck the coast within 75 miles of Basin Bayou, of which 10 were Category 3 or greater, making it a prime location to reconstruct intense hurricanes. Basin Bayou openly exchanges water with Choctawhatchee Bay through a narrow channel, which acts as a conduit for propagating storm surges, and potentially coarse-grained bay sediments, into the bayou. Our record is

  5. Seasonal deposition of Holocene banded sediments in the Severn Estuary Levels (southwest Britain): palynological and sedimentological evidence

    NASA Astrophysics Data System (ADS)

    D