scholarly journals Recent and Late Quaternary dinoflagellate cysts from the area of the Greenland –Iceland –Faeroe –Scotland Ridge

1984 ◽  
Vol 3 (2) ◽  
pp. 95-108 ◽  
Author(s):  
Rex Harland
Keyword(s):  
Continental Shelf ◽  
Late Quaternary ◽  
Dinoflagellate Cysts ◽  
Quaternary Sediments ◽  
The South ◽  
Northern Flank ◽  
Dinoflagellate Cyst ◽  
Southern Area

Abstract. Dinoflagellate cyst assemblages are described from Recent and Late Quaternary sediments recovered from Vema cores taken in the area of the Greenland – Iceland – Faeroe – Scotland Ridge. The dinoflagellate assemblage interpreted as indicating the Flandrian, “climatic” amelioration occurred in the sediments on the northern flank of the ridge whereas no evidence was found for this amelioration in the cores to the south. In the southern area, cyst assemblages proved an older climatic amelioration possibly of Eemian age. The potential for using dinoflagellate cysts to correlate oceanic and continental shelf areas is stressed.

scholarly journals Constraints on the precision of SAR in equivalent dose estimations close to saturation in quartz

2011 ◽  
Vol 38 (4) ◽  
pp. 413-423 ◽  
Author(s):  
Constantin Athanassas
Keyword(s):  
Growth Curve ◽  
Late Quaternary ◽  
Equivalent Dose ◽  
Curve Shape ◽  
Large Scatter ◽  
Dose Estimation ◽  
Quaternary Sediments ◽  
The South ◽  
Of Greece

Abstract Difficulties in evaluating accurate equivalent doses for Late Quaternary sediments from the south coasts of Greece arose in the course of SAR measurements. Large scatter among apparent equivalent doses perplexed the evaluation of accurate mean estimates in circumstances where very large doses were involved. Besides, dose recovery experiments revealed that when intersection of the natural signal occurs onto the saturating segment of the growth curve, a distinct relationship between De and growth curve shape occurs. At very low slope angles, SAR tends to overestimate the recovered dose. The mechanism which controls the spread in equivalent dose estimation is investigated.

scholarly journals Depositional Environments and History of Late Quaternary Sediments in Hudson Strait and Ungava Bay: Further Evidence from Seismic and Biostratigraphic Data

2007 ◽  
Vol 46 (3) ◽  
pp. 311-329 ◽  
Author(s):  
Brian MacLean ◽  
Gustav Vilks ◽  
Bhan Deonarine
Keyword(s):  
Late Quaternary ◽  
Depositional Environments ◽  
Quaternary Sediments ◽  
The South ◽  
Bay Area ◽  
South Central ◽  
History Of ◽  
Ams Dating ◽  
Seafloor Sediments ◽  
Glaciomarine Sediments

ABSTRACT Regional ship-borne investigations of seafloor sediments provide further information on late Quaternary depositional environments and history in the Hudson Strait-Ungava Bay region. Greatest sediment thicknesses, up to 130 m, occur in the large basin in eastern Hudson Strait and in the western Hudson Strait basin north of Charles Island. Significant deposits are also present in basins southwest of Charles Island, along the south central part of the Strait, and in the southern part of Ungava Bay. Glacial drift deposits are widespread, but glaciomarine and postglacial sediments mainly occur in the basinal areas, with glaciomarine sediments generally predominating. Glaciomarine sediments are laterally transitional to glacial drift in the south central part of the Strait, and at many other basin margins. AMS dating of the deepest shells found within three cores from the glaciomarine sequences in the Wakeham Bay-Baie Héricart region of south central Hudson Strait yielded ages of 8390 ± 70,8420 ± 80, and 8520 ± 80 BP. Sequences underlying the dated intervals may contain time equivalents of glaciomarine sediments 1000-2000 years older found onshore in the Deception Bay area by Gray, Bruneau, and others.

scholarly journals Late Quaternary freshwater dinoflagellate cysts from the British Isles

1985 ◽  
Vol 4 (2) ◽  
pp. 101-109 ◽  
Author(s):  
Chris O. Hunt ◽  
Martha V. Andrews ◽  
David D. Gilbertson
Keyword(s):  
Fresh Water ◽  
Late Quaternary ◽  
British Isles ◽  
Dinoflagellate Cysts ◽  
Dinoflagellate Cyst ◽  
Fluvial Deposits

Abstract. Two species of peridinioid dinoflagellate cyst are described from Late Quaternary lacustrine and fluvial deposits in England and Scotland. Saeptodinium skipseaense sp. nov. has a bipesoid tabulation and a hemiepicystal archaeopyle. Colonsaydinium psilatum gen. et sp. nov. has a compound archaeopyle interpreted as 213P (1–2i 3–5″). The morphology of the archaeopyle suggests that this may be the cyst of a species with cinctoid tabulation. Both taxa are found only in sediment laid down in base-rich, non-turbulent, relatively deep fresh water.

scholarly journals Late Quaternary Geology of the Canterbury Continental Terrace

2021 ◽  
Author(s):  
◽  
Richard Howard Herzer
Keyword(s):  
Grain Size ◽  
Continental Shelf ◽  
Sea Level ◽  
Late Quaternary ◽  
High Energy ◽  
The South ◽  
Submarine Canyons ◽  
Radiocarbon Dates ◽  
Sea Bed ◽  
Quaternary Stratigraphy

<p>The Late Quaternary stratigraphy and sedimentary processes are interpreted for an area of continental shelf and slope on the eastern side of the South Island, New Zealand, between latitudes 43°00's and 44°50's. Two formations are recognised in the Late Quaternary stratigraphy of the shelf: the Canterbury Bight Formation of mainly Last Glacia1 age and, locally overlying it, the Pegasus Formation of mainly Holocene age. The formations are distinguished by shelf-wide unconformities (visib1e in seismic profiles), by geomorphology, by grain-size modes, and by macrofauna. Ridge-and-swa1e topography occurs on two scales on the shelf. Very large ridges and troughs are interpreted from microbathymetry, stratigraphy, sediments and macrofauna to be the remains of Pleistocene barrier/lagoon complexes. With the aid of radiocarbon dates, four well developed shorelines between 28,000 yr and 15,000 yr old are recognised. The smaller ridges are submarine features, formed by strong currents. Those ridges that are in a zone of constricted and accelerated currents near Banks Peninsula are active, while those well removed from the peninsula constriction are fossil and date from times of lower sea level. Sedimentation on the continental shelf has reached a state of equilibrium with the modern hydraulic regime. Relict sediments of the deglacial transgressive sand/gravel sheet are being reworked in zones of high energy, principally in the region of constricted flow around Banks Peninsula. Modern-input sand (distinguished by its grain-size mode) is restricted by currents mainly to an active belt near shore, but locally it has replaced palimpsest sand on the middle shelf. The modern mud facies, being confined by zones of higher energy, has reached its maximum areal extent; its greatest thickness is in Pegasus Bay. Sea-bed drifter studies, and studies of sediment texture and provenance show that net sediment movement on the shelf and along shore during both Pleistocene and modern times has been northwards. The continental slope is dissected by submarine slide scars in the south and by submarine canyons in the north. Streams of fine sand, transported from the continental shelf to the upper slope by north-flowing currents during Pleistocene lowered sea levels, initiated the erosion of submarine canyons. Interception of littoral-drifted gravel by established canyons reaching Pleistocene strand lines probably accelerated. canyon erosion. The canyons are thought to be now effectively dormant. Deposition of fine sediment from suspension has dominated the development of the southern slope. This slope is consequently free of deeply corrasional features like submarine canyons but is prone to failure by gravity sliding. The youngest slides are less than 18,000 yr old. The history of growth of Pegasus Submarine Canyon is investigated in detail. The course of the canyon across the shelf is not fault controlled. As well as growing landwards, the canyon and its tributaries have, during Pleistocene sea level stillstands, grown southwards along shore towards the supply of littoral drifted gravel and sand. A buried tributary, of Penultimate Glacial age or older, on the canyon's west side, once brought the canyon 7 km closer to the present shore. The relative ages of the south-trending arms of the canyon are inferred from their relationship to known Last Glacial shorelines that are preserved on the shelf, and by their position with respect to a regional subsurface unconformity of Penultimate Glacial age. Canyon erosion was concentrated in the largest arm during the last deglacial rise of sea level, and shallow channels, interpreted as feeders are common around its rim.</p>

Active Tectonics and Paleoseismicity of the Eastern Issyk-Kul Basin (Kyrgyzstan, Tien Shan)

2021 ◽  
Vol 62 (03) ◽  
pp. 263-277
Author(s):  
A.M. Korzhenkov ◽  
E.V. Deev ◽  
I.V. Turova ◽  
S.V. Abdieva ◽  
S.S. Ivanov ◽  
...  
Keyword(s):  
Surface Deformation ◽  
Late Quaternary ◽  
Active Tectonics ◽  
Historical Earthquakes ◽  
Strike Slip ◽  
Tien Shan ◽  
Quaternary Sediments ◽  
The South ◽  
Large Earthquakes ◽  
Tectonic Movements

Abstract —The Malyi Orgochor, Orgochor, Birbash, Sukhoi Ridge, Ichketosma, and Tosma uplifts in the eastern Issyk-Kul basin are fault-related anticlinal folds composed of Neogene and Quaternary sediments involved in tectonic movements. The folds have asymmetric transversal profiles, with low-angle southern limbs and steep northern limbs cut by segments of the South Issyk-Kul and Karkara reverse faults reactivated in the late Quaternary. The location and geometry of the two faults, which both show reverse and left-lateral strike slip components, correspond to neotectonic propagation of deformation from the Terskey-Ala-Too Range over almost the whole eastern Issyk-Kul basin. Judging by primary and secondary coseismic surface deformation in the area, the South Issyk-Kul and Karkara faults repeatedly generated large earthquakes (M ≥ 7, I ≥ 9) in the Late Pleistocene and Holocene. According to trenching results, the historical earthquakes that occurred in the first and 10–11th centuries accommodated motions on the South Issyk-Kul fault. The new seismotectonic and paleoseismicity data from the eastern Issyk-Kul basin provide updates to its seismic potential.

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