摘要:

AbstractLower Pleistocene sediments recovered in boreholes from the Aberdeen Ground Formation in the central North Sea indicate that the unit was deposited in a delta front to prodelta/shallow, open shelf marine setting. Possible estuarine and clastic nearshore marine deposits have been identified on the western margin of the basin. The delta front sediments consist of interbedded, structureless to laminated sands and muds with organic debris, ferruginous nodules and common soft sediment deformation structures. Sporadic rippled and graded beds, basal scours to beds and starved ripples suggest periodic wave–current reworking. Prodelta/shelf marine sediments are predominantly argillaceous with only occasional thin sand beds and rare phosphatic bands. One exceptionally thick sand body or submarine channel‐fill although this remains uncertain. The estuarine/clastic nearshore marine sediments include coarse channel‐lag deposits and rippled and laminated subtidal sands. A rich microfossil assemblage recovered from the prodelta/shelf marine sequence indicates that deposition occurred under fluctuating climatic condi

ISSN:0267-8179    

DOI:10.1002/jqs.3390020202

出版商:John Wiley&Sons, Ltd    

年代:1987

数据来源: WILEY

摘要:

AbstractCores recovered from the Witch Ground Basin (central North Sea) and the northern Rockall Trough, near the Wyville‐Thomson Ridge have been found to contain volcanic glass shards. These have been correlated with the Vedde Ash Bed of western Norway, which has an age of 10600± 60yr BP, and with North Atlantic ash zone 1. This is the first time that this important chronostratigraphic marker has been identified on the UK continental shelf and it is suggested that it might also be present in northern Scotland. If so, it would be a useful tool in the correlation of terrestrial, lacustrine and marine sequences of the Loch Lomond Stadi

ISSN:0267-8179    

DOI:10.1002/jqs.3390020203

出版商:John Wiley&Sons, Ltd    

年代:1987

数据来源: WILEY

摘要:

AbstractA radial pattern of ice flow of the last ice sheet in the largest source area of ice (c. 5000 km2) in the British Isles in western Scotland is demonstrated by the dispersal of indicator erratics and by patterns of striae, friction cracks and ice‐moulded landforms. Three major ice domes and the principal ice divide are identified in the western Grampians. The ice domes coincided with the highest mountain blocks while it is inferred that the alignment of many of the pre‐existing valleys controlled much of the outflow of ice, forming ice streams within the ice sheet. The importance of the Rannoch Moor basin as a radial provider of ice to surrounding areas was apparently less significant than has hitherto been considered. Ice flowed into and across the southern part of the basin from the principal ice divide located to the west and south. No evidence has yet been found that would support a model of an eastward‐migrating ice divide either during the build‐up or during the deglaciation of the Late Devensian ic

ISSN:0267-8179    

DOI:10.1002/jqs.3390020204

出版商:John Wiley&Sons, Ltd    

年代:1987

数据来源: WILEY

摘要:

AbstractThe postglacial sea‐level history along a cross‐section of western Norway has been studied in detail. Ten local sea‐level curves were used to construct an equidistant shoreline diagram, covering the last 13000 years. This includes 76 radiocarbon dates, of which the majority represent lacustrine sediments at the marine/lacustrine boundary in cores from emerged lakes. The distance between the westernmost and easternmost sites is 170 km and the difference in total emergence along this profile is more than 200 m. The shorelines all dip westward with a decreasing gradient through time. The Late Weichselian lines are all slightly curved whereas the Holocene lines are apparently straight. After the formation of the uppermost shoreline by around 12 800 BP there was a rapid emergence that decelerated with time to a near standstill during the Younger Dryas. From about 10 300 there was again a rapid emergence followed by the Tapes transgression along the coast and a standstill in the most easterly areas. At the western end of this profile, the Tapes transgression started around 9000 and culminated approximately 6000 BP, when a gradual regression occurred. To the east the early Holocene regression minimum occurs at a younger date and the transgression maximum is up to 1500 years

ISSN:0267-8179    

DOI:10.1002/jqs.3390020205

出版商:John Wiley&Sons, Ltd    

年代:1987

数据来源: WILEY

摘要:

AbstractA14C‐dated magnetostratigraphy of absolute declination and inclination between 12500 and 1000014C yr BP was recently developed for southern Sweden. Recently also the Swedish geochronological time‐scale, based on c. 11 500 annually deposited clay‐varves, was connected with the present. It should therefore be possible to compare the two chronologies with a reliable magnetostratigraphic record in an appropriate clay‐varve section. We have found such a site within the Middle Swedish end‐moraine zone. Statistical correlations between the two independently dated time‐scales suggest that at 10500–1020014Cy r BP the varve chronology exceeds the14C chronology by the order of 500‐600 varve yr. Other correlations indicate that the difference between the two chronologies was less at 1100014C yr BP, and further correlations between the time‐scales at 1200014C yr BP suggest that the difference between the chronologies increased steadily from 12000 to 1000014C yr BP. If these correlations are correct they imply that the14C production rate increased steadily during the

ISSN:0267-8179    

DOI:10.1002/jqs.3390020206

出版商:John Wiley&Sons, Ltd    

年代:1987

数据来源: WILEY

摘要:

AbstractA 5.3m profile originally described as loess with a buried interglacial soil is reinterpreted from petrographic evidence and thermoluminescence dating as a Holocene colluvial accretionary soil. Mineralogical analyses of coarse silt (16–63 μm) fractions suggest that most of the silty colluvium was derived from weathered Thanet Beds upslope, though some loess was incorporated during the final depositional phase. Thin sections show that clay illuviation occurred penecontem‐poraneously with deposition of colluvium. Thermoluminescence properties suggest partial optical bleaching of the grains during rapid deposition, which is consistent with a Holocene colluvial or

ISSN:0267-8179    

DOI:10.1002/jqs.3390020207

出版商:John Wiley&Sons, Ltd    

年代:1987

数据来源: WILEY

摘要:

AbstractResults of palaeoecological studies involving pollen analytical, chemical and palaeomagnetic investigations on a 3 m core from Lough Doo, NE County Mayo, are presented. The record, which commences shortly after 7000 BP, shows a sharpAlnusexpansion coinciding with a decline inPiusat 6400 BP, an elm decline taking place in the context of severe soil erosion and the final decline ofPinusoccurring as the chemical record indicates onset of severe reducing conditions in the catchment. Pine becomes extinct at or shortly before 3200 BP in the context of increased farming activity and the expansion of blanket bog in the adjacent upland areas. A later feature (c. 1880 BP) is the expansion ofTaxusto 7.1% of total pollen.On the basis of the palynological evidence, it is concluded that there were no major Neolithic Landnam phases, which contrasts sharply with the evidence for widespread woodland clearance and the laying out of extensive and regular field systems in the northern coastal part of County Mayo. In the upper part of the core a severe inversion of14C dates is recorded. On the basis of the palaeomagnetic and pollen evidence this began at c. 1500 BP and is considered to have been initiated in the context of woodland clearance and a renewal in farming activity.

ISSN:0267-8179    

DOI:10.1002/jqs.3390020208

出版商:John Wiley&Sons, Ltd    

年代:1987

数据来源: WILEY

ISSN:0267-8179    

DOI:10.1002/jqs.3390020209

出版商:John Wiley&Sons, Ltd    

年代:1987

数据来源: WILEY

ISSN:0267-8179    

DOI:10.1002/jqs.3390020210

出版商:John Wiley&Sons, Ltd    

年代:1987

数据来源: WILEY

ISSN:0267-8179    

DOI:10.1002/jqs.3390020211

出版商:John Wiley&Sons, Ltd    

年代:1987

数据来源: WILEY