Changes in Benthic Foraminiferal Assemblages Marking the Pleistocene-to-holocene Transition on the Blake Outer Ridge, Western North Atlantic Ocean PDF Download

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Changes in Benthic Foraminiferal Assemblages Marking the Pleistocene-to-holocene Transition on the Blake Outer Ridge, Western North Atlantic Ocean

Changes in Benthic Foraminiferal Assemblages Marking the Pleistocene-to-holocene Transition on the Blake Outer Ridge, Western North Atlantic Ocean PDF Author: Katherine Taylor Whittaker
Publisher:
ISBN:
Category : Foraminifera
Languages : en
Pages : 134

Book Description


Changes in Benthic Foraminiferal Assemblages Marking the Pleistocene-to-holocene Transition on the Blake Outer Ridge, Western North Atlantic Ocean

Changes in Benthic Foraminiferal Assemblages Marking the Pleistocene-to-holocene Transition on the Blake Outer Ridge, Western North Atlantic Ocean PDF Author: Katherine Taylor Whittaker
Publisher:
ISBN:
Category : Foraminifera
Languages : en
Pages : 134

Book Description


North Carolina Coastal Oceanography Symposium

North Carolina Coastal Oceanography Symposium PDF Author: Robert Y. George
Publisher:
ISBN:
Category : Coastal ecology
Languages : en
Pages : 626

Book Description


Proceedings of the Ocean Drilling Program

Proceedings of the Ocean Drilling Program PDF Author: Ocean Drilling Program
Publisher:
ISBN:
Category : Borings
Languages : en
Pages : 492

Book Description


Benthic Foraminifera as Paleo-sea-ice Indicators in the Western Arctic Ocean

Benthic Foraminifera as Paleo-sea-ice Indicators in the Western Arctic Ocean PDF Author: Kelly Best Lazar
Publisher:
ISBN:
Category :
Languages : en
Pages :

Book Description
As global climate continues to warm, the Arctic Ocean is becoming increasingly vulnerable, largely due to a fast retreat of sea ice. Knowledge of paleo-sea-ice conditions is essential for comprehending the changing Arctic system. This study combines micropaleontological (foraminiferal) data with existing litho- and chronostratigraphic results to construct a more resolved stratigraphic record and history of sea-ice change during the Quaternary in the western Arctic Ocean. Benthic foraminiferal assemblages were investigated in four sediment cores from the Northwind, Mendeleev, and Lomonosov Ridges (western Arctic Ocean). A uniquely-preserved sediment core from the Northwind Ridge was found to contain the longest calcareous foraminiferal record in the Arctic Ocean, estimated to extend to the early Pleistocene, ca. 1.5 Ma. This record was divided into two assemblage zones, representing distinct changes in foraminiferal composition with respect to ecological groups (polar vs. phytodetrital species) and extinct taxa. The distribution of polar and phytodetrital species yields significant information related to sea ice (perennial vs. seasonal) and associated climatic conditions. A principal faunal and sedimentary turnover occurred near the early-middle Pleistocene boundary (estimated ca 0.7-0.8 Ma), indicating an advance of perennial sea ice along with an increase in glacial inputs from the Laurentide ice sheet at the end of the Mid-Pleistocene Transition (MPT).

Early-Middle Pleistocene Transitions

Early-Middle Pleistocene Transitions PDF Author: Geological Society of London
Publisher: Geological Society of London
ISBN: 9781862391819
Category : Science
Languages : en
Pages : 342

Book Description
The Early-Middle Pleistocene transition (around 1.2 to 0.5 Ma) marks a profound shift in Earth's climate state. Low-amplitude 41 ka climate cycles, dominating the earlier part of the Pleistocene, gave way progressively to a 100 ka rhythm of increased amplitude that characterizes our present glacial-interglacial world. This volume assesses the biotic and physical response to this transition both on land and in the oceans: indeed it examines the very nature of Quaternary climate change. Milankovitch theory, palaeoceanography using isotopes and microfossils, marine organic geochemistry, tephrochronology, the record of loess and soil deposition, terrestrial vegetational change, and the migration and evolution of hominins as well as other large and small mammals, are all considered. These themes combine to explore the very origins of our present biota.

Benthic Foraminiferal Assemblages on the Continental Margin Off Nova Scotia

Benthic Foraminiferal Assemblages on the Continental Margin Off Nova Scotia PDF Author: Mark A. Williamson
Publisher:
ISBN:
Category :
Languages : en
Pages : 0

Book Description
Two hundred and fifty grab samples from the continental margin off Nova Scotia were examined for total (live+dead) foraminiferal content. One hundred and twenty species were recognised, seventy five of which occur with an abundance greater than 3% in any one sample. Q-Mode factor analysis of the raw abundance data (total population) determined 8 shelf and 4 slope factor assemblages, accounting for 87.5% and 77% of the original raw data respectively. Comparison of the live data with the factor assemblages enabled the detection of anomalous assemblages which are un-representative in respect to present day environments. In the north east of the study area (around Misaine, Canso and Banquereau) an exclusively agglutinated assemblage dominated by Adercotryma glomerata occupies both banks and basins. In the LaHave and Emerald Basins of the central shelf, a predominantly calcareous assemblage occurs with maximum amounts of Globobulimina auriculata and Nonionellina labradorica. Transitional between these two shelf assemblages is an agglutinating assemblage dominated by Saccammina atlantica. Consistently present along the shelf edge is a Trifarina angulosa assemblage. Present in Chedabucto and Gaberous bays and in a few samples near Sable Island is an agglutinating Eggerella adyena assemblage. A relict and in some areas a transport affected assemblage is recognised in the south western approaches to Emerald Basin on the Scotian Gulf; this is dominated by Elphidium excayatum. Occupying the hard, rough bedrock, and sandy/gravelly areas of the inner shelf and outer bank regions is a Cibicides lobatulus assemblage. Four assemblages lie seaward of the shelf break. An upper slope assemblage is dominated by Bulimina exilis, with a local variation dominated by Trifarina occidentalis. A lower slope assemblage is dominated by Uvigerina peregrina. Also present in slope regions is another Elphidium excayatum assemblage which is thought to be the down slope equivalent of the shelf assemblage. The statistical relationship of these defined assemblages to various aspects of the marine environment (depth, temperature, salinity, percent gravel, sand and mud) were investigated through multiple regression techniques. This indicates that the present foraminiferal distribution patterns off Nova Scotia are mainly a response to the prevailing hydrography. The Adercotryma glomerata assemblage is influenced by the presence of cold, less than normal salinity waters of arctic, Labrador current origin. The central basin assemblage (G. auriculata) is related to warmer more saline waters of slope origin. The transition between these two bottom waters is marked by the Saccammina atlantica assemblage. The primary influence of the hydrography on assemblage distribution patterns on the shelf off Nova Scotia is probably related to calcium carbonate availability which is a function of temperature, salinity, and carbon dioxide content within each water type. Preferred substrate character is found to determine the occurrence of the Cibicides lobatulus assemblage. Diversity trends within the study area were examined (S,H(s),∝,E). Each index used produced similar patterns which indicate relationships to hydrography and environmental stability. Implications of the present study for further work on Pleistocene to Recent climatic changes are discussed with reference to a piston core from Canso Basin. On the basis of this study the down core changes in foraminiferal populations indicate several distinct variations in temperature and salinity since the last glaciation; these variations are probably a result of the varying degree of influence that Labrador derived waters have had in this area and is in turn a function of changing ice volumes to the north.

Late Quaternary Benthic Foraminiferal Assemblages from the Eastern South Atlantic Ocean : Reconstruction of Deep Water Circulation and Productivity Changes

Late Quaternary Benthic Foraminiferal Assemblages from the Eastern South Atlantic Ocean : Reconstruction of Deep Water Circulation and Productivity Changes PDF Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 207

Book Description


BENTHIC FORAMINIFERAL ASSEMBLAGE AND SEDIMENTOLOGICAL CHANGES WITHIN THE PLIOCENE YORKTOWN FORMATION, SOUTHEASTERN VIRGINIA.

BENTHIC FORAMINIFERAL ASSEMBLAGE AND SEDIMENTOLOGICAL CHANGES WITHIN THE PLIOCENE YORKTOWN FORMATION, SOUTHEASTERN VIRGINIA. PDF Author: Whittney E. Spivey
Publisher:
ISBN:
Category :
Languages : en
Pages : 95

Book Description
The Pliocene Yorktown Formation consists of four distinct lithologic units that record three marine transgressive sequences along the U.S. mid-Atlantic margin. The Sunken Meadow Member was deposited during the Zanclean Stage and the Rushmere, Morgarts Beach, and Moore House members are assigned to the Piacenzian Stage. These units were deposited during a time when global atmospheric CO2 concentrations were similar to present, and average sea-level and mean global temperatures were ~25 meters and ~3[degrees]C higher than the pre-industrial, respectively. During the Piacenzian, the largest cool to warm transition took place between Marine Isotope Stages (MIS) M2 (3.3 Ma) and M1 (3.25 Ma) recorded in the Rushmere and Morgarts Beach sediments. The mid-Piacenzian Warm Period (~3.264--3.025 Ma; mPWP) is an interval widely considered to have had climatic conditions similar to projections for the end of the 21st century; the base of the mPWP is defined by the transition between peak MIS M2 and peak MIS M1.Forty-five samples were collected along the James River near Rushmere, Virginia, and at Pipsico Boy Scout Camp, Spring Grove, Virginia and were analyzed for benthic foraminifer community and sedimentological changes between each member of the formation. These data are useful boundary conditions for shallow, near-shore environments for future global climate models. Discernible differences in grain-size distribution occur between the Sunken Meadow and Rushmere members; generally, the Sunken Meadow Member is composed of coarser sands, has less mud, and has a higher percentage of sand and phosphatic and glauconitic grains than the Rushmere Member. These sedimentological changes are often subtle in outcrop and occur within decimeters of the contact between the two units, giving the appearance that the two units are conformable in some areas. The most notable change in grain-size occurs at the conformable boundary between the Rushmere and Morgarts Beach members, where the average percentage of sand decreases from ~60% in the Rushmere Member to ~16% in the Morgarts Beach Member. Foraminiferal analysis distinguishes six biofacies across the entire Formation--two in the Sunken Meadow Member, three within the conformable Rushmere-Morgarts Beach members, and one in the Moore House Member. The Sunken Meadow Member represents a marine transgression, where changes in benthic foraminiferal assemblages and grain-size distribution indicate up-section deepening of water depth. Deposition of this unit has been interpreted as a mild temperate shallow-shelf setting with normal marine salinity based on the molluscan assemblage. This unit likely records the maximum phase of the transgression (maximum flooding). The Rushmere-Morgarts Beach members record the most extensive transgression in the Pliocene. Grain-size analysis and benthic foraminiferal assemblages indicate a shift in depositional environment from an open, middle shelf environment in the Rushmere Member to a restricted lagoonal environment in the Morgarts Beach Member. The molluscan assemblage indicates a subtropical to tropical climate. The least extensive Pliocene transgression is recorded in the Moore House Member. It likely represents a cooler temperate environment and the formation of offshore bars in the Salisbury Embayment.

Holocene Benthic Foraminiferal Assemblages from the SW Pacific: Implications for a High Resolution

Holocene Benthic Foraminiferal Assemblages from the SW Pacific: Implications for a High Resolution PDF Author: Sascha Überall
Publisher:
ISBN:
Category :
Languages : de
Pages : 0

Book Description


Benthic foraminifers as tools to reconstruct high-latitude Holocene climate variability and processes during cold-water coral mound growth and development

Benthic foraminifers as tools to reconstruct high-latitude Holocene climate variability and processes during cold-water coral mound growth and development PDF Author: Nina Forster
Publisher: BoD – Books on Demand
ISBN: 3732285073
Category : Science
Languages : en
Pages : 250

Book Description
Cold-water corals occur worldwide from high latitudes to tropical areas, in various settings from the deep-sea to shallow marine environments near the coast. The topic of this thesis is the establishment and extension of knowledge about environmental conditions controlling cold-water coral (CWC) mound development. From literature it is known that glacial-interglacial cycles drive development and geographic distribution of CWC mounds on a large scale. On the other hand, knowledge about the influence of small scale climatic and oceanographic changes during the Holocene is scarce. Thus, this thesis focuses on the investigation of the limited Holocene climatic and oceanographic changes and their effect on the process of mound genesis. For this purpose, a Holocene CWC mound setting in a sound in the Altafjord in northern Norway (70°N) -- the Stjernsund -- was chosen and the local benthic ecosystem was extensively analysed. Von den sub-arktischen hohen Breiten bis in warme tropische Zonen besiedeln Kaltwasserkorallen unseren Planeten. Sie haben sich verschiedenste Lebensräume erschlossen --- Von der Tiefsee bis zu marinen Flachwassergebieten an der Küste kann ihr Vorkommen beobachtet werden. Sie bilden faszinierende Ökosysteme die erst in den letzten Jahrzehnten intensiver erforscht wurden. Diese Arbeit widmet sich der tieferen Erforschung dieser Lebensräume. Im Fokus stehen dabei Umweltbedingungen, die die Entwicklung der Kaltwasserkorallenvorkommen kontrollieren. Umfangreiche frühere Untersuchungen haben bereits gezeigt, dass ihr Wachstum, als auch ihre geographische Verbreitung im Wesentlichen von Glazial-Interglazial-Zyklen gesteuert werden. Die kurzzeitlichen klimatischen und ozeanographischen Steuerungsfaktoren sind im Vergleich dazu jedoch nahezu unbekannt. Daher konzentriert sich diese Arbeit auf die Erforschung von kurzeitigen klimatischen und ozeanographischen Veränderungen, die insbesondere im Holozän zu beobachten sind, sowie deren mögliche Auswirkungen auf die Entwicklung von Kaltwasserkorallen Mounds. Hierzu wurde der holozäne Kaltwasserkorallen Mound im Stjernsund, ein Sund im Altafjord in Nordnorwegen (70°N) ausgewählt und dessen benthisches Ökosystem umfassend analysiert.