scholarly journals Late Quaternary Paleoceanography and Sedimentary Environments in Hudson Strait

2007 ◽  
Vol 43 (2) ◽  
pp. 161-178 ◽  
Author(s):  
G. Vilks ◽  
B. MacLean ◽  
B. Deonarine ◽  
C. G. Currie ◽  
K. Moran
Keyword(s):  
Late Quaternary ◽  
Tidal Mixing ◽  
Last Deglaciation ◽  
Eastern Basin ◽  
Sedimentary Environments ◽  
Minimum Age ◽  
Bottom Waters ◽  
Salinity Difference ◽  
Seismic Reflection Profiles ◽  
Glaciomarine Sediments

ABSTRACT Airgun and high resolution Huntec seismic reflection profiles are interpreted to show up to 130 m of glacial, glaciomarine and postglacial sediments overlying bedrock. In a basin at the eastern entrance to Hudson Strait most of the surficial sediment was deposited during the last déglaciation, but in western Hudson Strait multiple till sequences from previous glaciations are recognized. Five acoustic units were identified, at least three of which were penetrated with piston cores. Foraminifera of the stratigraphically deepest core in the eastern basin indicate a proximal glaciomarine environment and a likely presence of an ice shelf. A 14C date of 8060 ± 70 yBP (TO 750) on molluscan shells gives a minimum age for the top of the acoustically laminated distal glaciomarine sediments. The early postglacial foraminifera suggest a period of increased influence of offshore bottom waters restricted to the deep eastern basin. The surface sediments of all cores contain species indigenous of colder and fresher inshore waters of the present time. The ratio of 18CV16O in the benthic foraminifer Cibicides lobatulus is herein related to bottom salinity. Downcore measurements of 8'8O on C. lobatulus tests indicate bottom paleosalinities lower by about 0.5%o shortly before the dated horizon of 8000 yBP. By this time Hudson Strait was sufficiently clear of glacial ice for establishment of the present tidal regime. The lower bottom salinities indicate that tidal mixing took place between glacial meltwater leaving Hudson Bay and the offshore counterflow. This process is thought to have reduced the sharpness of the salinity difference between the offshore water and the surface plume of Laurentide meltwater as it entered the ocean.

scholarly journals Late Quaternary history of Lammefjorden, north-west Sjælland, Denmark

2020 ◽  
Author(s):  
Ole Bennike ◽  
Peter Roll Jakobsen ◽  
Jakob Walløe Hansen
Keyword(s):  
Late Quaternary ◽  
Sediment Cores ◽  
Late Glacial ◽  
Early Holocene ◽  
Last Deglaciation ◽  
North West ◽  
Najas Marina ◽  
Marine Deposits ◽  
Minimum Age ◽  
History Of

Lammefjorden is a reclaimed fjord in north-west Sjælland, Denmark. Sediment cores from the area were collected to study its development after the last deglaciation, in particular the sea-level history. Late glacial and Early Holocene lake and bog deposits occur below marine deposits. Sparse late glacial fossil assemblages indicate tree-less environments with dwarf-shrub heaths. Early Holocene deposits contain remains of Betula sec. Albae sp. and Pinus sylvestris, which indicate open forests. The wetland flora comprised the calciphilous reed plant Cladium mariscus and the water plant Najas marina. Marine gyttja from basins is characterised by sparse benthic faunas, probably due to high sedimentation rates. In some areas, shell-rich deposits were found, with large shells of Ostrea edulis, indicative of high summer temperatures, high salinity and strong tidal currents. A marine shell dated to 6.7 cal. ka provides a minimum age for the marine transgression of Lammefjorden.

Late Quaternary deep marine sediment records off southern Africa

2021 ◽  
Author(s):  
H.C. Cawthra ◽  
E.W. Bergh ◽  
E.A. Wiles ◽  
J.S. Compton
Keyword(s):  
Southern Africa ◽  
Late Quaternary ◽  
Strongly Correlated ◽  
Sea Level Fluctuations ◽  
Proxy Records ◽  
Terrestrial Environments ◽  
Bottom Waters ◽  
Resolution Mapping ◽  
And Shifts ◽  
Glacial Periods

Abstract High-resolution mapping, sampling and analysis of upper Quaternary southern African continental margin sediments recovered from beyond the Last Glacial Maximum shoreline (>130 m water depth) have expanded our understanding of how marine and terrestrial records are linked over glacial-interglacial climatic cycles. This paper synthesises data currently available from the deep seafloor around southern Africa and, specifically, core sites that demonstrate terrestrial sedimentological connectivity. Several proxies and case studies reveal the evolution of depositional systems, palaeoceanography and palaeoclimate over the last 191 kyr. Hydroacoustic mapping and investigations of submarine canyons have been carried out primarily on the eastern and southwestern margins, while palaeoceanographic productivity and microfossil assemblages have been applied most extensively on the western marine and southern Agulhas Bank. Studies on the western margin indicate that enhanced productivity, less oxygenated bottom waters and reduced marine faunal diversity in the transition to glacial periods, while glacial terminations are associated with reduced productivity and more oxygenated bottom waters. These changes, linked to palaeoceanography and late Quaternary sea-level fluctuations, influence the sedimentary record and sedimentation rates. On the eastern margin, sediment fluxes applied as proxies for rainfall offshore of the Great Kei, Umzimvubu, Limpopo and Zambezi rivers indicate that the southern African climate responds to changes in orbitally-modulated insolation and in particular, to the ~23 kyr precessional cycle, where the proxy records keep pace with this and then diverge at ~80 to 70 kyr. Since the penultimate glacial (Marine Isotope Stage/MIS 6), more humid conditions observed in southern Africa, as the Northern Hemisphere entered phases of rapid cooling, were potentially driven by a combination of warming in the Agulhas Current and shifts of the subtropical anticyclones. Broadly, the sedimentary records reviewed suggest fluctuations in climate and oceanographic circulation that are strongly correlated with the global benthic δ18O record, suggesting sensitivity to high-latitude forcing, and a strong influence of late Quaternary glacial-interglacial cycles despite these marine sites being far-removed from terrestrial environments.

Late Quaternary sedimentation on the southwestern Scotian Slope, eastern Canada: relationship to glaciationGeological Survey of Canada Contribution 20070176.

2008 ◽  
Vol 45 (3) ◽  
pp. 267-285 ◽  
Author(s):  
Thian Hundert ◽  
David J.W. Piper
Keyword(s):  
Late Quaternary ◽  
Sediment Cores ◽  
Sediment Supply ◽  
Scotian Shelf ◽  
Eastern Canada ◽  
Glacial Retreat ◽  
Air Gun ◽  
Continental Slopes ◽  
History Of ◽  
Seismic Reflection Profiles

The sedimentary record on continental slopes has the potential to preserve a record of glacial retreat on the adjacent continental shelf. The glacial history of the southwestern part of the Scotian Shelf is poorly known. Air-gun and high-resolution sparker profiles and numerous sediment cores up to 10 m long have been used to determine the character of sedimentation on the southwestern Scotian Slope since the last glacial maximum (LGM). Seismic-reflection profiles show that glacial till was deposited at shallow depths on the upper continental slope, and correlation to dated piston cores farther downslope show that this till dates from the LGM. Slope sedimentation at this time was dominated by local ice and deposited as plume fallout and turbidites. Progressively increasing importance of red-brown sediment derived from glacial supply to Laurentian Channel indicates retreat of ice from the shelf edge and diminishing supply of proglacial sediment from the calving embayment in the mid-Scotian Shelf. With the termination of distal proglacial sediment supply, the sedimentation rate diminished rapidly and hemipelagic sedimentation prevailed through the Holocene.

scholarly journals Combination of Numerical Dating Techniques Using 10Be in Rock Boulders and 14C of Resilient Soil Organic Matter for Reconstructing the Chronology of Glacial and Periglacial Processes in a High Alpine Catchment during the Late Pleistocene and Early Holocene

Radiocarbon ◽  
2009 ◽  
Vol 51 (2) ◽  
pp. 537-552 ◽  
Author(s):  
Filippo Favilli ◽  
Markus Egli ◽  
Dagmar Brandova ◽  
Susan Ivy-Ochs ◽  
Peter W Kubik ◽  
...  
Keyword(s):  
Organic Matter ◽  
Soil Organic Matter ◽  
Late Quaternary ◽  
Chemical Characterization ◽  
Soil Formation ◽  
Parent Material ◽  
Surface Dynamics ◽  
Exposure Dating ◽  
Minimum Age ◽  
Absolute Dating

Glacier fluctuations and paleoclimatic oscillations during the Late Quaternary in Val di Rabbi (Trentino, northern Italy) were reconstructed using a combination of absolute dating techniques (14C and 10Be) and soil chemical characterization. Extraction and dating of the stable fraction of soil organic matter (SOM) gave valuable information about the minimum age of soil formation and contributed to the deciphering of geomorphic surface dynamics. The comparison of 10Be surface exposure dating (SED) of rock surfaces with the 14C ages of resilient (resistant to H2O2 oxidation) soil organic matter gave a fairly good agreement, but with some questionable aspects. It is concluded that, applied with adequate carefulness, dating of SOM with 14C might be a useful tool in reconstructing landscape history in high Alpine areas with siliceous parent material. The combination of 14C dating of SOM with SED with cosmogenic 10Be (on moraines and erratic boulders) indicated that deglaciation processes in Val di Rabbi were already ongoing by around 14,000 cal BP at an altitude of 2300 m asl and that glacier oscillations might have affected the higher part of the region until about 9000 cal BP. 10Be and 14C ages correlate well with the altitude of the sampling sites and with the established Lateglacial chronology.

Using remote sensing to quantify aeolian transport and estimate the age of the terminal dune field Dunas Pampa Blanca in southern Peru

2009 ◽  
Vol 71 (3) ◽  
pp. 426-436 ◽  
Author(s):  
Ralf Hesse
Keyword(s):  
Late Quaternary ◽  
Digital Processing ◽  
Sediment Supply ◽  
Aeolian Transport ◽  
Dune Field ◽  
Southern Peru ◽  
Coastal Desert ◽  
Aeolian Dunes ◽  
Minimum Age ◽  
Transverse Dunes

AbstractAeolian dunes are widely used to reconstruct paleoenvironmental conditions. However, terminal dune fields (ergs) in the coastal desert of southern Peru – where information regarding Quaternary paleoenvironmental conditions is very limited – have until now not been used for paleoenvironmental reconstructions and the time depth of their accumulation is unknown. Here, different estimates are derived to constrain the time depth recorded in the Dunas Pampa Blanca, a terminal dune field in coastal southern Peru. Dune field age is calculated using the volume of the Dunas Pampa Blanca and (i) recent aeolian transport rate in migrating transverse dunes feeding the Dunas Pampa Blanca (derived from digital processing of sequential Landsat and Quickbird images) and (ii) limitations posed by recent fluvial sediment supply to the source of aeolian transport. The resulting maximum age estimate of 70 ± 8 ka (from aeolian transport) compares with a minimum age estimate of 4–75 ka (from sediment supply). However, a minimum age estimate of 110–450 ka is deduced from the tectonic and topographic evolution of the region. This discrepancy contradicts the hypothesis of late Quaternary stability in the Peruvian coastal desert and indicates that recent conditions of aeolian sediment supply and transport are not representative for the late Quaternary.

The late Quaternary history of Greely Fiord and its tributaries, west-central Ellesmere Island

1990 ◽  
Vol 27 (2) ◽  
pp. 255-270 ◽  
Author(s):  
John England
Keyword(s):  
Sea Level ◽  
Late Quaternary ◽  
Sensu Stricto ◽  
Ellesmere Island ◽  
Relative Sea Level ◽  
Ice Caps ◽  
Last Glaciation ◽  
West Central ◽  
Grounding Line ◽  
Minimum Age

Moraines and meltwater channels mark the limit of the last glaciation that interfingered with the sea around the perimeter of Greely Fiord and its tributaries. The extent of this ice advance was dictated predominantly by its proximity to the sea. Consequently, the large tidewater glaciers at the fiord heads today were so constrained by calving that they advanced only 5–10 km. Similarly, grounding-line deposits from widespread plateau ice caps also terminate just below marine limit. The most extensive outlet glaciers, which advanced 20–35 km beyond present margins, are simply those that had access to the most extensive terrain above marine limit, i.e., the northwest margin of the Agassiz Ice Cap.Forty-one new 14C dates are presented. The onset of the last ice advance must predate marine shells collected from sediments overlying a former grounding line when sea level was 122 m higher than present. At this site, the lowermost shells collected from glaciomarine silts dated 38 070 ± 410 BP, whereas a surface sample 13 m above them dated 22 900 ± 190 BP. Although both dates may be minimum estimates, they are nonetheless associated with an ice margin that retreated only a few kilometres by 7850 BP, suggesting the maintenance of the glacioisostatic loading (and relative sea level) during the interim. Nearby, shells in growth position overlying bedrock confirm that relative sea level was > 83 m asl by 38 010 ± 410 BP (minimum age). These marine deposits lie outside the last ice limit and are not overlain by glacigenic sediments.Distal to the last ice limit, Greely Fiord was occupied by the full glacial sea, whose limit is marked by discontinuous beaches and wave-cut benches. The full glacial sea rises from 116 m north of Greely Fiord to a maximum elevation of 148 m bordering its south shore from which it descends to 112 m asl near the head of Cañon Fiord. Numerous 14C dates on shells collected within 8 m of marine limit show that the full glacial sea remained stable from at least 8400 to 7400 BP. Several other shell samples collected ~20 m below marine limit are much older (> 22 000 BP). The position of relative sea level between ca. 8000 and > 22 000 BP is uncertain; however, stratigraphic evidence for an intervening regression has not been found.The modest extent of the last ice limit encircling Greely Fiord, together with its occupancy by the full glacial sea, is fully compatible with the paleogeography previously reported from northeast Ellesmere Island and northwest Greenland. Furthermore, this data base provides a reinterpretation of a 500 km transect previously reported along west-central Ellesmere Island to the south and affirms that the Innuitian Ice Sheet, defined sensu stricto for the last glaciation, is supplanted by the full glacial Innuitian Sea, which penetrated the Queen Elizabeth Islands, constraining the last ice limit.

Late Quaternary glacio- and Hydro-Isostasy, on a Layered Earth

1974 ◽  
Vol 4 (4) ◽  
pp. 405-428 ◽  
Author(s):  
J. Chappell
Keyword(s):  
North America ◽  
Late Quaternary ◽  
Oceanic Islands ◽  
Mantle Flow ◽  
Upward Movement ◽  
Last Deglaciation ◽  
Regional Effects ◽  
Relaxation Effects ◽  
The Earth ◽  
Hinge Zone

Isostatic response of the Earth to changes in Quaternary Times of ice and water loads is partly elastic, and partly involves viscous mantle flow. The relaxation spectrum of the Earth, critical for estimation of the mantle flow component, is estimated from published determinations of Fennoscandian and Laurentide rebound, and of the nontidal acceleration of the Earth's rotation. The spectrum is consistent with an asthenosphere viscosity around 1021P, and a viscosity around 1023P below 400 km depth. Calculation of relaxation effects is done by convoluting the load history with the response function in spherical harmonics for global effects, and in rectangular or cylindrical transforms for smaller regional effects. Broad-scale deformation of the globe, resulting from the last deglaciation and sea level rise, is calculated to have involved an average depression of ocean basins of about 8 m, and mean upward movement of continents of about 16 m, relative to the center of the Earth, in the last 7000 yr. Deflection in the ocean margin “hinge zone” varies with continental shelf geometry and rigidity of the underlying lithosphere: predictions are made for different model cases. The computational methods is checked by predicting Fennoscandian and Laurentide postglacial warping, from published estimates of icecap histories, with good results. The depth variations of shorelines formed around 17,000 BP (e.g., North America, 90–130 m; Australia, 130–170 m), are largely explainable in terms of combined elastic and relaxation isostasy. Differences between Holocene eustatic records from oceanic islands (Micronesia, Bermuda), and continental coasts (eastern North America, Australia), are largely but not entirely explained in the same terms.

Faunal dynamics of foraminiferal assemblages in the Bathonian (Middle Jurassic) ore-bearing clays at Gnaszyn, Kraków-Silesia Homocline, Poland

2012 ◽  
Vol 62 (3) ◽  
pp. 403-419 ◽  
Author(s):  
Jolanta Smoleń
Keyword(s):  
Sedimentation Rate ◽  
Middle Jurassic ◽  
Taxonomic Diversity ◽  
Feeding Strategies ◽  
Type I ◽  
Type Ii ◽  
Low Oxygen ◽  
Sedimentary Environments ◽  
South Central ◽  
Bottom Waters

ABSTRACT Smoleń, J. 2012. Faunal dynamics of foraminiferal assemblages in the Bathonian (Middle Jurassic) ore-bearing clays at Gnaszyn, Kraków-Silesia Homocline, Poland. Acta Geologica Polonica, 62(3), 403-419. Warszawa. The faunal dynamics of benthic foraminifera in the Middle Jurassic ore-bearing clays of Gnaszyn (Kraków- Częstochowa Upland, south-central Poland) are used to reconstruct sedimentary environments. Two types of foraminiferal assemblages, distinct in their quantitative and qualitative composition, were distinguished; type I assemblages, characterizing intervals between horizons with sideritic concretions; and type II assemblages, characterising horizons with sideritic concretions. Benthic foraminifers were further subdivided into eight ecological morphogroups, based on their morphological features and micro-habitats. Type I assemblages consist mostly of plano/concavo-convex, small-sized epifaunal morphotypes, with a restricted occurrence of shallow infaunal forms and a scarcity of deep infaunal taxa, which suggests low-oxygen conditions in both sediment and bottom waters, and a high sedimentation rate in an outer shelf environment. Type II assemblages are characterized by high taxonomic diversity, high specimen abundance and variability of epifaunal and infaunal morphotypes representing a mixed group of specialized feeding strategies. This suggests optimum living conditions controlled by a lower sedimentation rate, relatively well-oxygenated bottom waters and sufficient or high food supply.

scholarly journals Interplay of Holocene surface faulting and climate in the Central Po Plain, Italy

2021 ◽  
pp. 1-16
Author(s):  
Andrea Zanchi ◽  
Cesare Ravazzi ◽  
Angelo Cavallin ◽  
Massimiliano Deaddis ◽  
Mattia De Amicis ◽  
...  
Keyword(s):  
Late Quaternary ◽  
Historical Earthquakes ◽  
Thrust Fault ◽  
Lateral Spreading ◽  
Maximum Displacement ◽  
Fault Movement ◽  
Po Plain ◽  
Minimum Age ◽  
History Of ◽  
Quaternary History

Abstract Understanding the recent events marking the late Quaternary history of the Po Plain (N-Italy) is of overriding importance to decipher the record of depositional versus erosional phases, and their interplay with climatic, tectonic, and human forcing. We reconstructed the structural setting and chronostratigraphy of a Holocene succession crosscut by a thrust fault located south of Montodine (Cremona, Italy) within the Po Plain. The fault shows a maximum displacement up to one meter. Radiocarbon dating fixes a minimum age of 11.9 cal ka BP for the postglacial river entrenchment and constrains the fault movement age between 5.9 and 3.4 cal ka BP. Undeformed Late Medieval coarse gravels cover the faulted succession. Due to the outcrop position, lying above the buried frontal thrusts of the Southern Alps and North Apennines, we propose that faulting results from secondary surface effects induced by seismic shaking. We discuss two main mechanisms, both related to lateral spreading, that can result in the formation of reverse faults close to the surface. The Soncino area, recording one of the strongest historical earthquakes of the central Po Plain (1802), is considered as a possible source for seismic shaking. The results of this study are a contribution for the assessment of the potential seismic hazard in one of the most populated regions of Europe.

Turning waves and crustal reflection profiling

Geophysics ◽  
1997 ◽  
Vol 62 (1) ◽  
pp. 335-341 ◽  
Author(s):  
Ralf Stadtlander ◽  
Larry Brown
Keyword(s):  
Sedimentary Cover ◽  
Indirect Evidence ◽  
Sedimentary Environments ◽  
The Past ◽  
Velocity Gradients ◽  
Basement Structures ◽  
Wave Migration ◽  
Seismic Reflection Profiles ◽  
Imaging Algorithms ◽  
Crustal Reflection

In the past, steeply dipping features were often recognized on seismic reflection profiles only from indirect evidence such as vertical offsets of cross‐cutting structures. New imaging algorithms, as for example, turning wave migration have had dramatic success in delineating steep, even‐overturned reflectors in sedimentary environments. Evaluation of the applicability of this technology to deep seismic recordings indicates that steep‐dip and turning wave migration will have limited practicality, generally, in the imaging of basement features because of the weak velocity gradients involved and the corollary requirement for large recording offsets. A potential exception arises when the basement structures to be imaged lie beneath a significant thickness of relatively young (i.e., steep velocity gradient) sedimentary cover.

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