An integrated sequence stratigraphic, palaeoenvironmental, and chronostratigraphic analysis of the Tangahoe Formation, southern Taranaki coast, with implications for mid-Pliocene (c. 3.4–3.0 Ma) glacio-eustatic sea-level changes

Sediments of the mid-Pliocene (c. 3.4–3.0 Ma) Tangahoe Formation exposed in cliffs along the South Taranaki coastline of New Zealand comprise a 270 m thick, cyclothemic shallow-marine succession that has been gently warped into a north to south trending, low angle anticline. This study examines the sedimentologic, faunal, and petrographic characteristics of 10 Milankovitch-scale (6th order), shallow-marine depositional sequences exposed on the western limb of the anticline. The sequences are recognised on the basis of the cyclic vertical stacking of their constituent lithofacies, which are bound by sharp wave cut surfaces produced during transgressive shoreface erosion. Each sequence comprises three parts: (1) a 0.2–2 m thick, deepening upwards, basal suite of reworked bioclastic lag deposits (onlap shellbed) and/or an overlying matrix supported, molluscan shellbed of offshore shelf affinity (backlap shellbed); (2) a 5–20 m thick, gradually shoaling, aggradational siltstone succession; and (3) a 5–10 m thick, strongly progradational, well sorted “forced regressive” shoreline sandstone. The three-fold subdivision corresponds to transgressive, highstand, and regressive systems tracts (TSTs, HSTs, and RSTs) respectively, and represents deposition during a glacio-eustatic sea-level cycle. Lowstand systems tract sediments are not recorded because the outcrop is situated c. 100 km east of the contemporary shelf edge and was subaerially exposed at that time. Well developed, sharp- and gradational-based forced regressive sandstones contain a variety of storm-emplaced sedimentary structures, and represent the rapid and abrupt basinward translation of the shoreline on to a storm dominated, shallow shelf during eustatic sea-level fall. Increased supply of sediment from north-west South Island during “forced regression” is indicated from petrographic analyses of the heavy mineralogy of the sandstones. A chronology based on biostratigraphy and the correlation of a new magnetostratigraphy to the magnetic polarity timescale allows: (1) identification of the Mammoth (C2An.2r) and Kaena (C2An.1r) subchrons; (2) correlation of the coastal section to the Waipipian Stage; and (3) estimation of the age of the coastal section as 3.36–3.06 Ma. Qualitative assessment of foraminiferal census data and molluscan palaeoecology reveals cyclic changes in water depth from shelf to shoreline environments during the deposition of each sequence. Seven major cycles in water depth of between 20 and 50m have been correlated to individual 40 ka glacio-eustatic sea-level cycles on the marine oxygen isotope timescale. The coastal Tangahoe Formation provides a shallow-marine record of global glacio-eustasy prior to the development of significant ice sheets on Northern Hemisphere continents, and supports evidence from marine δ18O archives that changes in Antarctic ice volume were occurring during the Pliocene

THE LATE QUATERNARY HISTORY OF THE RIVER ERME, SOUTH DEVON

This thesis examines a typical 'drowned* river valley of south-west England. The River Erme drains southern Dartmoor and, in common, with other rivers of the region, has a buried channel graded to c. -50m OD. The channel has been infilled with a variety of sediments, of which the top 6-7m have been analysed for this study. Augered cores have been collected from the modern floodplain and salt marsh areas in the lower part of the valley and have been studied using particle size, diatom, molluscan and radiocarbon analyses. The main sediment types recovered include a fine silt unit representing the most recent phase of fluvial deposition, which overlies variable horizons of fluvial granitic sands and gravels and brackish organic sands and silts. These are, in places, replaced at depth by shelly silts, sands and gravels deposited under more estuarine and marine conditions. The organic layer has been radiocarbon dated to between 1000 and 2000 years BP and has been correlated with a former area of marshland recorded in the tithe maps of the region. It is suggested that the Erme valley was previously more estuarine than today and that alluviation and infilling of the Erme's channel in the last 1000-2000 years has been aided by forest clearance and tin mining on Dartmoor. All of the sediments recovered from the buried channel are derived from local sources of bedrock and have probably been deposited in the last 4000-6000 years. Evidence from the tithe maps suggests that the channel has been stable in the past 200 years. This work seeks to contribute to the Quaternary knowledge of the south-west of England, and because of the paucity of data concerning these burled rock channels, makes this study of the River Erme a preliminary model against which other rivers in the South West may be compared.University College, Swanse

Late Glacial Sedimentation and History of the Lake Nipigon Basin, Ontario

The Lake Nipigon basin lies north of the Lake Superior basin and was the hydrological link between glacial Lake Agassiz and the Great Lakes during part of the last deglaciation. A sequence of glaciolacustrine sediments, composed mainly of silt-clay rhythmites and sand, was deposited in the offshore waters of glacial Lake Nipigon by overflow from Lake Agassiz and meltwater from the retreating glacier margin. Sections from six long sediment cores and four lake bluff exposures reveal a sandy (early deglacial) lower section that is overlain by 300 to 850 silt-clay rhythmites (varves). Deposition of these varves, as well as coarser sediment along the western shore, began after 9200 BP, as the glacial margin retreated northward along the continental divide that separated the Nipigon basin from the higher Lake Agassiz basin to the west. The absence of ice rafted clasts in the rhythmites suggests that the ice had retreated from the lake by the time they were deposited. On the basis of their elevation in relation to the lowest raised beach at West Bay, which formed about 9000 BP, most rhythmites probably were deposited between 9000 and 8000 BP. Species of arboreal pollen are present in early postglacial sediments of the Nipigon-Superior lowlands, suggesting that the Lake Nipigon region became colonized by coniferous and deciduous forests soon after déglaciation. The presence of non-arboreal pollen species suggest that these forests were interspersed with open meadows and grasslands, similar to today's floral assemblages. Fossil molluscs recovered from glaciolacustrine sand exposed along the eastern side of the basin suggest that the limnological characteristics of late glacial Lake Nipigon were similar to those of today.Le bassin du lac Nipigon situé au nord du bassin du lac Supérieur a assuré le lien hydrologique entre le Lac Agassiz et les Grands Lacs pendant une partie de la dernière glaciation. Une séquence de sédiments glaciolacustres, surtout composés de rythmites silto-argileuses et de sable, a été déposée au large du rivage du Lac glaciaire Nipigon par les eaux de crue du Lac Agassiz et les eaux de fonte du glacier en recul. Les coupes dans six carottes de sédiments et quatre coupes naturelles dans la falaise révèlent la présence de sable dans la partie inférieure (début de la déglaciation) recouverte par 300 à 850 rythmites silto-argileuses (varves). La mise en place de ces varves, comme celle des sédiments plus grossiers le long de la rive ouest, a commencé après 9200 BP, alors que la marge glaciaire reculait vers le nord le long de la ligne de partage des eaux entre le bassin du Lac Nipigon de celui plus élevé du Lac Agassiz. L'absence de fragments glaciels dans les rythmites indique que le glacier s'était déjà retiré. Selon leur altitude par rapport à la plage perchée la moins élevée à West Bay, formée vers 9000 BP, la plupart des rythmites ont été déposées entre 9000 et 8000 BP. Le pollen arboréen présent dans les premiers sédiments postglaciaires des basses terres Nipigon-Supérieur montre que les forêts de conifères et de décidus se sont établies peu après la déglaciation. La présence de pollen non arboréen montre que ces forêts étaient parsemées de prés ouverts et de prairies, comme c'est le cas aujourd'hui. Les mollusques fossiles recueillis dans les sables glaciolacustres le long du côté est du bassin montrent que les propriétés limnologiques du Lac Nipigon sont semblables à celles d'aujourd'hui.Das Becken des Nipigonsees liegt nôrdlich von dem des Oberen Sees, und war das hydrologische Bindeglied zwischen dem glazialen Agassizsee und den groBen Seen wàhrend eines Teils der letzten Enteisung. Eine Sequenz glaziallimnischer Sedimente, hauptsàchlich aus Schlamm-Lehm, Rhythmiten und Sand bestehend, wurde in dem kùstennahen Wasser des glazialen Nipigansees abgelagert durch ùberlauf vom Agassizsee und Schmelzwasser von dem zurùckweichenden Gletscherrand. Abschnitte von sechs langen Sedimentbohrkernen und vier See-Steilhang-Aufschlùsse zeigen einen sandigen (Beginn der Enteisung) unteren Bereich, der von 300 bis 850 Schlamm-Lehm-Rhythmiten (Warwen) ùberlagert ist. Die Ablagerung dieser Warwen sowie grôberer Sedimente entlang der westlichen Kùste begann nach 9200 v.u.Z., als der Eisrand nordwârts zurùckwich, entlang der Wasserscheide, die das Nipiganbecken von dem hôheren Agassizbecken nach Westen hin trennte. Das Fehlen von Eisfragmenten in den Rhythmiten IaBt vermuten daB das Eis zum Zeitpunkt ihrer Ablagerung vom See schon zurùckgewichen dap das Eis zum Zeitpunkt war. Entsprechend ihrer Erhebung in Bezug auf den niedrigsten gehobenen Strand in der West Bay, der sich um 9000 v.u.Z. herausbildete, wurden die meisten Rhythmite wohl zwischen 9000 und 8000 v.u.Z. abgelagert. Baumpollenarten in den frùhen postglazialen Sedimenten der Superior-Nipigan-Ebenen legen nahe, daB im Nipigansee -Gebiet kurz nach der Enteisung Tannen- und Laubwald sich ausbreiteten. Das Vorkommen von baumfremden Pollenarten zeigt, daB die Wâlder von offenen Weiden und Grasland durchsetzt waren, àhnlich der heutigen Bewachsung. Schalentier-Fossile, die aus dem glaziallimnischen Sand gewonnen wurden, entlang der ôstlichen Seite des Beckens, zeigen, daB die limnologischen Charakteristika des spâtglazialen Nipigan-sees den heutigen àhnlich waren

Florida Bay Science Program: a synthesis of research on Florida Bay

This report documents the progress made toward the objectives established in the Strategic Plan revised in 1997 for the agencies cooperating in the program. These objectives are expressed as five questions that organized the research on the Florida Bay ecosystem: Ecosystem History What was the Florida Bay ecosystem like 50, 100, and 150 years ago? Question 1—Physical Processes How and at what rates do storms, changing freshwater flows, sea level rise, and local evaporation and precipitation influence circulation and salinity patterns within Florida Bay and exchange between the bay and adjacent waters? Question 2—Nutrient Dynamics What is the relative importance of the influx of external nutrients and of internal nutrient cycling in determining the nutrient budget for Florida Bay? What mechanisms control the sources and sinks of the bay’s nutrients? Question 3—Plankton Blooms What regulates the onset, persistence, and fate of planktonic algal blooms in Florida Bay? Question 4—Seagrass Ecology What are the causes and mechanisms for the observed changes in the seagrass community of Florida Bay? What is the effect of changing salinity, light, and nutrient regimes on these communities? Question 5—Higher Trophic Levels What is the relationship between environmental and habitat change and the recruitment, growth, and survivorship of animals in Florida Bay? Each question examines different characteristics of the Florida Bay ecosystem and the relation of these to the geomorphological setting of the bay and to processes linking the bay with adjacent systems and driving change.This report also examines the additional question of what changes have occurred in Florida Bay over the past 150 years

Stable isotope compositions of fossil mollusks from southern California: Evidence for a cool last interglacial ocean

Stable isotope compositions have been determined for modem mullusks and fossil mollusks collected from uplied marine terraces at three l d t i e s in southern California. By using a paleocliatic model that decouples the temperature and ice-volume signals in ocean water, ocean-water temperatures off southern California are estimated to have been -3.8 °C at ~85 ka, -3.0 °C at ~107 ka, and -2.2 °C at ~125 ka relative to present temperature. These results indicate rather cool conditions during the peak of the last interglacial stage at 125 ka and conflict with results from terrace faunal studies that suggest water temperatures were warm or warmer than at present

Sediment core fossils in ancient Lake Ohrid: testing for faunal change since the Last Interglacial

Ancient Lake Ohrid is probably of early Pleistocene or Pliocene origin and amongst the few lakes in the world harbouring an outstanding degree of endemic biodiversity. Although there is a long history of evolutionary research in Lake Ohrid, particularly on molluscs, a mollusc fossil record has been missing up to date. For the first time, gastropod and bivalve fossils are reported from the basal, calcareous part of a 2.6 m long sediment succession (core Co1200) from the north-eastern part of Lake Ohrid. Electron spin resonance (ESR) dating of mollusc shells from the same stratigraphic level yielded an age of 130 ± 28 ka. Lithofacies III sediments, i.e. a stratigraphic subdivision comprising the basal succession of core Co1200 between 181.5–263 cm, appeared solid, greyish-white, and consisted almost entirely of silt-sized endogenic calcite (CaCO<sub>3</sub>>70%) and intact and broken mollusc shells. Here we compare the faunal composition of the thanatocoenosis with recent mollusc associations in Lake Ohrid. A total of 13 mollusc species (9 gastropod and 4 bivalve species) could be identified within Lithofacies III sediments. The value of sediment core fossils for reconstructing palaeoenvironmental settings was evaluated and the agreement between sediment and palaeontological proxies was tested. <br><br> The study also aims at investigating major faunal changes since the Last Interglacial and searching for signs of extinction events. <br><br> The combined findings of the ecological study and the sediment characteristics suggest deposition in a shallow water environment during the Last Interglacial. The fossil fauna exclusively included species also found in the present fauna, i.e. no extinction events are evident for this site since the Last Interglacial. The thanatocoenosis showed the highest similarity with recent Intermediate Layer (5–25 m water depth) mollusc assemblages. The demonstrated existence of a mollusc fossil record in Lake Ohrid sediment cores also has great significance for future deep drilling projects. It can be hoped that a more far reaching mollusc fossil record will then be obtained, enabling insight into the early evolutionary history of Lake Ohrid

Mollusca from a species-rich deep-water Leptometra community in the Alboran Sea

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Tropical limestone forest resilience during MIS-2: implications for Pleistocene foraging & modern conservation

In this paper we present a multi-proxy study of tropical limestone forest and its utilization by human groups during the major climatic and environmental upheavals of MIS-2 (29-11.7 ka BP). Our data are drawn from new field research within the Tràng An World Heritage property, on the edge of the Red River Delta, northern Vietnam. Key findings from this study include 1) that limestone forest formations were resilient to the large-scale landscape transformation and inundation of the Sunda continent at the end of the last glaciation; 2) that prehistoric human groups were probably present in this habitat through-out MIS-2; and 3) that the forested, almost insular, karst of Tràng An provided foragers with a stable resource-base in a wider changing landscape. These results have implications for our understanding of the prehistoric utilization of karst environments and resonance for conservation efforts in the face of climate and environmental change today

Stratigraphic analyses of late-quaternary sediments from S’Albufera, North East Mallorca, Spain

1. Much of the environmental history of the western Mediterranean has been inferred from records obtained throughout a wider region. Very little work has been conducted on Mallorca. Sediments suited to palaeoenvironmental studies are of limited extent within the Balearic Islands, principally as a result of climatic factors. Stratigraphic cores were collected from two sites (Es Colombar, Amarador) on S'Albufera marsh, Mallorca, in the hope that the sedimentary records could provide source material for interpreting environmental history. In order to develop an understanding of past environmental conditions at S'Albufera, and to asses the potential for future studies of this nature, lithological, geochemical and micropalaeontological (pollen and foraminifera) analyses were conducted upon the sediments. Pollen data were explored using the constrained incremental sum of squares (CONISS) multivariate technique. Through these investigations, an understanding of the geomorphological and vegetation history of S'Albufera has been achieved. 3. All data suggest that S'Albufera was a saline lagoon system throughout the period reflected in these sediments. Progressive sea level rise facilitated an areal expansion of this lagoon. Periods of reduced mean water level have also been identified, one of which was initiated in 1856 during drainage of the lagoon, and is still apparent today. In the absence of absolute dates, it is proposed that earlier phases of lower mean water level occurred during the historical period, in response to the influence of anthropogenic disturbance, eustatic flux or climatic shifts. A relative chronology has been inferred from Corylus pollen data. Amarador is believed to have been a lagoon since ca. 8000 yr. B P., whilst Es Colombar became inundated ca. 3000 yr. B P.4. Pollen assemblages suggest the vegetation of S'Albufera has varied little throughout the lagoonal period. Local vegetation, dominated by salt-tolerant, semi-aquatic Chenopodiaceae and Gramineae, has only grown at the coring sites during periods of reduced mean water levels. At other times local pollen contributions were derived from marsh vegetation at the lagoon periphery. Regional pollen signals are dominated by arboreal inputs e.g. Pinus and Quercus. Regional trends are obscured by low pollen sums and aquatic deposition, which affords highly-mixed assemblages.5. As a relatively undisturbed sedimentary environment, S'Albufera displays great potential as a site for palaeoenvironmental reconstruction work. The nature of the deposits exerts some influence over the suitability of some lines of investigation, pollen included. It is proposed that maximum gains from future studies would be derived from the study of other assemblages, such as ostracods, diatoms and charophytes. All of these groups are believed to be well-represented within the sedimentary record