Academia.eduAcademia.edu

Figure 6 – uploaded by Caroline Hillier

See full PDFdownloadDownload figure
Figure 5 Machair Loin microfossil data, lithology and radiocarbon ages. Depths refer to centimetres below ground surface and the sill of the basin lie at 10.5m OD. Radiocarbon ages shown +10 and 95% probability range, yr BP. Pollen data for species >2% total land pollen These are two peat bogs that grade into tidal marshes on the north shore of West Loch Tarbert (Fig. 2). At their seaward end peat overlies thick, impenetrable silt and sand of similar Cores across this sediment-filled depression reveal at least 3m of unconsolidated sediment in the centre of the basin behind a sill at 10.4 + 0.2m OD (Fig. 2). Herbaceous peat at the surface grades down into organic limnic sediment that lies above a basal sand-silt clastic unit. All cores in the centre of the basin bottomed in this impenetrable unit. No diatoms or foraminifera are preserved in this clastic unit but pollen and marine

Figure 5 Machair Loin microfossil data, lithology and radiocarbon ages. Depths refer to centimetres below ground surface and the sill of the basin lie at 10.5m OD. Radiocarbon ages shown +10 and 95% probability range, yr BP. Pollen data for species >2% total land pollen These are two peat bogs that grade into tidal marshes on the north shore of West Loch Tarbert (Fig. 2). At their seaward end peat overlies thick, impenetrable silt and sand of similar Cores across this sediment-filled depression reveal at least 3m of unconsolidated sediment in the centre of the basin behind a sill at 10.4 + 0.2m OD (Fig. 2). Herbaceous peat at the surface grades down into organic limnic sediment that lies above a basal sand-silt clastic unit. All cores in the centre of the basin bottomed in this impenetrable unit. No diatoms or foraminifera are preserved in this clastic unit but pollen and marine

Related Figures (11)

oa: Journal of Quaternary Science KEYWORDS: | sea-level change; isostasy; model testing; palaeoenvironmental reconstructions; microfossil analyses
oa: Journal of Quaternary Science KEYWORDS: | sea-level change; isostasy; model testing; palaeoenvironmental reconstructions; microfossil analyses
Figure 1 (A) Location of sites with observations of relative sea-level change. (B) Location of sites with new data presented in ‘Summary anc discussion’. (C) Observations and model predictions of relative sea-level change 18 000 BP to present at Arisaig (after Shennan et al, 2005). Age erro pars for sea-level index points indicate the 95% probability range, years before present, and the vertical bar depicts the median calibrated age. The vertical error calculation includes the sum of all the quantified or estimated height errors. Relative sea level must lie at or below limiting dates, shown a solid symbols |. Model predictions come from: (A) the modified version of Lambeck (1995) described in Shennan et al. (2000); and (B) the modifiec version of Peltier et a/. (2002) described as model 3 in Shennan et al. (2002)
Figure 1 (A) Location of sites with observations of relative sea-level change. (B) Location of sites with new data presented in ‘Summary anc discussion’. (C) Observations and model predictions of relative sea-level change 18 000 BP to present at Arisaig (after Shennan et al, 2005). Age erro pars for sea-level index points indicate the 95% probability range, years before present, and the vertical bar depicts the median calibrated age. The vertical error calculation includes the sum of all the quantified or estimated height errors. Relative sea level must lie at or below limiting dates, shown a solid symbols |. Model predictions come from: (A) the modified version of Lambeck (1995) described in Shennan et al. (2000); and (B) the modifiec version of Peltier et a/. (2002) described as model 3 in Shennan et al. (2002)
Figure 2 (A) Location of the five sampling sites used to reconstruct relative sea-level change for Knapdale. (B) Schematic section showing the relationship between the sampling sites, including the elevation of the rock sills of the basins at Machair Loin, Loch Cill an Aonghais and Barnellan. (C) Cross-section of the marsh at Barr na Criche, constructed from transects of cores. Numbered cores are those sampled for biostratigrapy and radiocarbon dating—ages of samples taken from the base of the peat given as 95% probability range, yr BP
Figure 2 (A) Location of the five sampling sites used to reconstruct relative sea-level change for Knapdale. (B) Schematic section showing the relationship between the sampling sites, including the elevation of the rock sills of the basins at Machair Loin, Loch Cill an Aonghais and Barnellan. (C) Cross-section of the marsh at Barr na Criche, constructed from transects of cores. Numbered cores are those sampled for biostratigrapy and radiocarbon dating—ages of samples taken from the base of the peat given as 95% probability range, yr BP
Table 1 Previously unpublished sea-level index points for sites presented. All samples are plant macrofossils picked from the sediment unless stated otherwise
Table 1 Previously unpublished sea-level index points for sites presented. All samples are plant macrofossils picked from the sediment unless stated otherwise
Figure 3 Barnellan microfossil data, lithology and radiocarbon age. Depths refer to centimetres below ground surface and the sill of the basin lies al 30.4m OD. Radiocarbon age shown +10 and 95% probability range, yr BP. Diatom data show only species >2% total diatom count (M=mesohalobian, O-H = oligohalobous-halophile diatom salinity class). Pollen data for selected species, expressed as percentage total land poller This freshwater loch, ca. 100x150 m, is the remnant of a much larger water body in a rock basin behind a sill at 17.8 £0.5m OD. Cores taken at the edge of the loch reveal more than 8 m of sediment. The base of organic sediment coincides with the transition from foraminifera, in the underlying clastic units, to freshwater testate amoebae or thecamoebians (Fig. 4). This represents an isolation contact, dated 15410-14130 BP from herbaceous macrofossils in the basal 1. cm of the organic unit. Foraminifera below the contact give an age 15 490-14 170 BP, but this includes no marine reservoir correction. In a similar context from an isolation basin in Kintail (location 10, Fig. 1), Shennan et al. (2000) reported identical early Holocene ages from paired dates on foraminifera and bulk sediment. Both pairs of dates suggest that in shallow marine marginal environments such as isolation basins either the mixing of sea water is such that the marine reservoir effect is negligible or it is offset by old The index point from Barnellan is a reliable limiting date, demonstrating that by 17910-16770 BP the site was ice-free and relative sea level was no higher than the elevation of the sill. On balance, there is insufficient evidence to conclude unequivocally that the index point represents a fall of relative sea-level across the sill. So in testing different model predictions
Figure 3 Barnellan microfossil data, lithology and radiocarbon age. Depths refer to centimetres below ground surface and the sill of the basin lies al 30.4m OD. Radiocarbon age shown +10 and 95% probability range, yr BP. Diatom data show only species >2% total diatom count (M=mesohalobian, O-H = oligohalobous-halophile diatom salinity class). Pollen data for selected species, expressed as percentage total land poller This freshwater loch, ca. 100x150 m, is the remnant of a much larger water body in a rock basin behind a sill at 17.8 £0.5m OD. Cores taken at the edge of the loch reveal more than 8 m of sediment. The base of organic sediment coincides with the transition from foraminifera, in the underlying clastic units, to freshwater testate amoebae or thecamoebians (Fig. 4). This represents an isolation contact, dated 15410-14130 BP from herbaceous macrofossils in the basal 1. cm of the organic unit. Foraminifera below the contact give an age 15 490-14 170 BP, but this includes no marine reservoir correction. In a similar context from an isolation basin in Kintail (location 10, Fig. 1), Shennan et al. (2000) reported identical early Holocene ages from paired dates on foraminifera and bulk sediment. Both pairs of dates suggest that in shallow marine marginal environments such as isolation basins either the mixing of sea water is such that the marine reservoir effect is negligible or it is offset by old The index point from Barnellan is a reliable limiting date, demonstrating that by 17910-16770 BP the site was ice-free and relative sea level was no higher than the elevation of the sill. On balance, there is insufficient evidence to conclude unequivocally that the index point represents a fall of relative sea-level across the sill. So in testing different model predictions
Figure 6 Barr na Criche microfossil data, lithology and radiocarbon ages for cores 6, 18 and 24. See Fig. 2(C) for their elevation and position along the transect. Depths refer to cm below ground surface. Radiocarbon ages shown +10 and 95% probability range, yr BP. Pollen data for selected species as percentage total land pollen. Species shown represent marsh tree and herbaceous species. Pollen types present at core 6 but not shown at either 18 or 24 indicate absence in these cores
Figure 6 Barr na Criche microfossil data, lithology and radiocarbon ages for cores 6, 18 and 24. See Fig. 2(C) for their elevation and position along the transect. Depths refer to cm below ground surface. Radiocarbon ages shown +10 and 95% probability range, yr BP. Pollen data for selected species as percentage total land pollen. Species shown represent marsh tree and herbaceous species. Pollen types present at core 6 but not shown at either 18 or 24 indicate absence in these cores
Figure 7 Coire Camas Drollaman III diatom data, lithology and radiocarbon age. Depths refer to centimetres below ground surface and the sil of the basin lies at 38.4m OD. Radiocarbon age shown +1o and 95% probability range, yr BP. Diatom data show only species >2% tota count Additional cores from the site described by Shennan and Woodroffe (2003) provide samples suitable for radiocarbon and diatom analysis. Diatoms results, based upon counts of more than 200 valves per level compared to <50 in the earlier samples, show (Fig. 9) a transition from clastic to organic accumulation within a shallow body of standing water, a lagoon, rather than intertidal flat (cf. Shennan and Woodroffe, 2003). Both cores show consistent ages for cessation of tidal influx into the lagoon, ca. 2700 to ca. 2100 cal. yr BP (Table 1). Core 03/11 (Fig. 9) provides the more precise elevation reconstructions, being at the intertidal margin of the lagoon with a mixture of open water and intertidal diatom species, the latter typified by the aerophile species Diploneis interrupta. In Coire Camas Drollaman Ill (grid reference NM64058375) is one of a series of basins on the Ru Peninsula near to Arisaig (Shennan et al., 2005). It has a sill at 38.4m OD. Diatom data across the basal contact (Fig. 7) show freshwater sedimentation throughout, so the radiocarbon-dated sample, 16 700-15 270 BP, gives a minimum age for the basin becoming ice-free. It also constrains the marine limit to an elevation between this sill and the highest recorded basin with marine sedimentation, Upper Loch Dubh, sill at 36.5m OD, enhancing the precision of the
Figure 7 Coire Camas Drollaman III diatom data, lithology and radiocarbon age. Depths refer to centimetres below ground surface and the sil of the basin lies at 38.4m OD. Radiocarbon age shown +1o and 95% probability range, yr BP. Diatom data show only species >2% tota count Additional cores from the site described by Shennan and Woodroffe (2003) provide samples suitable for radiocarbon and diatom analysis. Diatoms results, based upon counts of more than 200 valves per level compared to <50 in the earlier samples, show (Fig. 9) a transition from clastic to organic accumulation within a shallow body of standing water, a lagoon, rather than intertidal flat (cf. Shennan and Woodroffe, 2003). Both cores show consistent ages for cessation of tidal influx into the lagoon, ca. 2700 to ca. 2100 cal. yr BP (Table 1). Core 03/11 (Fig. 9) provides the more precise elevation reconstructions, being at the intertidal margin of the lagoon with a mixture of open water and intertidal diatom species, the latter typified by the aerophile species Diploneis interrupta. In Coire Camas Drollaman Ill (grid reference NM64058375) is one of a series of basins on the Ru Peninsula near to Arisaig (Shennan et al., 2005). It has a sill at 38.4m OD. Diatom data across the basal contact (Fig. 7) show freshwater sedimentation throughout, so the radiocarbon-dated sample, 16 700-15 270 BP, gives a minimum age for the basin becoming ice-free. It also constrains the marine limit to an elevation between this sill and the highest recorded basin with marine sedimentation, Upper Loch Dubh, sill at 36.5m OD, enhancing the precision of the
Figure 9 Nostie core 11 diatom data, lithology and radiocarbon age. This core taken in 2003, after the original site description and analysis was published (Shennan and Woodroffe, 2003). Depths refer to centimetres below ground surface, elevation 7.42 m OD. Radiocarbon age shown +10 and 95% probability range, yr BP. Diatom data show only species >2% total count (P = polyhalobian, M=mesohalobian diatom salinity class)
Figure 9 Nostie core 11 diatom data, lithology and radiocarbon age. This core taken in 2003, after the original site description and analysis was published (Shennan and Woodroffe, 2003). Depths refer to centimetres below ground surface, elevation 7.42 m OD. Radiocarbon age shown +10 and 95% probability range, yr BP. Diatom data show only species >2% total count (P = polyhalobian, M=mesohalobian diatom salinity class)
Figure 10 Relative sea-level data for Skye, Kintail, Arisaig and Knapdale, sea-level index points as crosses and limiting index points shown as solid symbols |. Age error bars for sea-level index points indicate the 95% probability range, calibrated years before present and the vertical bar depicts the median calibrated age. The vertical error calculation includes the sum of all the quantified or estimated height errors. Relative sea level must lie at or below limiting index points, with error bars only visible when larger than the symbol size. Line graph shows relative sea-level model predictions based onan Earth model with the following model parameters: 71 km depth to the base of the lithosphere; upper mantle viscosity parameter of 5x 107° Pa s; lower mantle viscosity parameter of 4x 10? Pas and dominant contribution to the meltwater pulse IA event from the Antarctic ice sheet (Shennan et al., 2006)
Figure 10 Relative sea-level data for Skye, Kintail, Arisaig and Knapdale, sea-level index points as crosses and limiting index points shown as solid symbols |. Age error bars for sea-level index points indicate the 95% probability range, calibrated years before present and the vertical bar depicts the median calibrated age. The vertical error calculation includes the sum of all the quantified or estimated height errors. Relative sea level must lie at or below limiting index points, with error bars only visible when larger than the symbol size. Line graph shows relative sea-level model predictions based onan Earth model with the following model parameters: 71 km depth to the base of the lithosphere; upper mantle viscosity parameter of 5x 107° Pa s; lower mantle viscosity parameter of 4x 10? Pas and dominant contribution to the meltwater pulse IA event from the Antarctic ice sheet (Shennan et al., 2006)
Related topics:
ArchaeologyGeologyPost Glacial ReboundIce SheetsSea Level ChangeRelative Sea Level
580 California St., Suite 400
San Francisco, CA, 94104
© 2025 Academia. All rights reserved