ALBERT

Description: The Laurentide Ice Sheet (LIS) was a large, dynamic ice sheet in the early Holocene. The glacial events through Hudson Strait leading to its eventual demise are recorded in the well-dated Labrador shelf core, MD99-2236 from the Cartwright Saddle. We develop a detailed history of the timing of ice-sheet discharge events from the Hudson Strait outlet of the LIS during the Holocene using high-resolution detrital carbonate, ice rafted detritus (IRD), d18O, and sediment color data. Eight detrital carbonate peaks (DCPs) associated with IRD peaks and light oxygen isotope events punctuate the MD99-2236 record between 11.5 and 8.0 ka. We use the stratigraphy of the DCPs developed from MD99-2236 to select the appropriate DeltaR to calibrate the ages of recorded glacial events in Hudson Bay and Hudson Strait such that they match the DCPs in MD99-2236. We associate the eight DCPs with H0, Gold Cove advance, Noble Inlet advance, initial retreat of the Hudson Strait ice stream (HSIS) from Hudson Strait, opening of the Tyrrell Sea, and drainage of glacial lakes Agassiz and Ojibway. The opening of Foxe Channel and retreat of glacial ice from Foxe Basin are represented by a shoulder in the carbonate data. DeltaR of 350 years applied to the radiocarbon ages constraining glacial events H0 through the opening of the Tyrell Sea provided the best match with the MD99-2236 DCPs; DeltaR values and ages from the literature are used for the younger events. A very close age match was achieved between the 8.2 ka cold event in the Greenland ice cores, DCP7 (8.15 ka BP), and the drainage of glacial lakes Agassiz and Ojibway. Our stratigraphic comparison between the DCPs in MD99-2236 and the calibrated ages of Hudson Strait/Bay deglacial events shows that the retreat of the HSIS, the opening of the Tyrell Sea, and the catastrophic drainage of glacial lakes Agassiz and Ojibway at 8.2 ka are separate events that have been combined in previous estimates of the timing of the 8.2 ka event from marine records. SW Iceland shelf core MD99-2256 documents freshwater entrainment into the subpolar gyre from the Hudson Strait outlet via the Labrador, North Atlantic, and Irminger currents. The timing of freshwater release from the LIS Hudson Strait outlet in MD99-2236 matches evidence for freshwater forcing and LIS icebergs carrying foreign minerals to the SW Iceland shelf between 11.5 and 8.2 ka. The congruency of these records supports the conclusion of the entrainment of freshwater from the retreat of the LIS through Hudson Strait into the subpolar gyre and provides specific time periods when pulses of LIS freshwater were present to influence climate.

Description: Geophysical data from the Kangerlussuaq Trough, E Greenland (Dowdeswell et al., 2010; Stein, 1996), and from the West Iceland shelf (Syvitski et al., 1999) indicate that there are sites where pre Last Glacial Maximum (LGM) sediments exist, but no such sites have been successfully cored. However, a significant number of cores have been recovered that penetrate a basal diamicton, sometimes containing shells and foraminifera, and which are overlain by glacial marine sediments rich in ice rafted debris (IRD) (Jennings et al., 2000; Olafsdottir, 2004). At the LGM, reconstructions and marine field data (Andrews, 2008; Andrews et al., 1998, 2000; Dunhill, 2005; Funder et al., 2004; Hubbard et al., 2006; Vasskog et al., 2015) indicate that the Iceland and Greenland ice sheets were terminating at their shelf breaks with deposition on the slopes above the Denmark Strait. Active sediment deposition ceased on the Kangerlussuaq Trough Mouth Fan (KTMF) ca. 15.3 ka 14C BP (Andrews et al., 1998; Dunhill, 2005) and retreat to the present coastline occurred prior to deposition of the Vedde tephra (Jennings et al., 2006). There is strong evidence that a major change in deep-water circulation at ~15 cal ka BP resulted in abrupt warming at the onset of the Bølling/Allerød (B/A) interstadial (Thiagarajan et al., 2014; Thornalley et al., 2011). Syvitski et al (1999) and Norddahl and Ingolfsson (2015) argued that the Iceland Ice Sheet retreated rapidly during this time, driven by a rapid rise in relative sea level. Jennings et al. (2006) also presented radiocarbon evidence from marine cores for a rapid retreat of the Greenland Ice Sheet along Kangerlussuaq Trough (KT, Fig. 1).

Description: Seven pollen datasets are included. Each dataset is in a separate folder. Each folder contains two files: a text (docx) file with a short summary and an Excel with several sheets, including pollen counts (also percentage and concentration values), 14C dating, age-model details, macrofossils, etc.

Description: The short monolith (19 cm of peat and 10 cm of the mineral soil beneath), CF Ib, was taken at 40 m NW of the Visitor Centre (VC), immediately to the north of a transverse stone-wall. Mineral soil from nearby that was sealed by the stone wall also sampled (CF III: 10 cm long monolith). Pollen profile CF I (this has elsewhere been referred to as CF Ib) includes six spectra from the mineral soil and twelve spectra from the overlying peat. Profile CF III consists of six spectra. Four samples from the soil within a plough mark and two samples from the containing soil were pollen analytically investigated. The age/depth model for profile CF I consists of a linear regression line fitted to the three available 14C dates. As regards, profile CF III it is older than the basal peat in CF Ib, i.e. ca. 1000 BC. The pollen data support ascribing it to the Bronze Age. A bulk sample from the plough mark returned the 14C date 2390±40 BP. This suggests a fifth century BC date, i.e. early/mid Iron Age. LOI and tephra investigations were not carried out. These investigations relating to Céide Fields were carried out in PRU, NUIG, part-funded by The Heritage Council (of Ireland). The aim was to provide an environmental context for the establishment and use of the prehistoric stone-wall field system, and an overall chronological framework and an environmental history of the area.

Description: The sampling site was in an extensive blanket bog, 16 km south of Céide Fields Visitor Centre, where peat cutting had revealed many pine timbers and also oak timbers. This provided the opportunity to carry out a palaeoecological study that included pollen analysis and dendrochronological investigations. In the study area, the bedrock is Carboniferous sandstone which, to the east of the sampling area, gives way to Carboniferous limestone of the Moy valley. Here there are thick glacial deposits including well-developed drumlin fields, and the land is fertile and bogs are few. Core GRN I was taken where what appeared to be an isolated small pine stump (P2/W1) was present at ca. 58 cm in a turf bank (depth from the cutover surface; the uppermost peat (≥1 m) had been removed by peat cutters). At a lower level and in a drainage channel below the peat face, there were several pine timbers. A pine stump P1/W2) at this level from beside the core was 14C dated; pine stump P2 was also 14C dated. The age/depth model (Clam v. 2.2) for the pollen profile derives from a smooth spline curve (smooth factor = 0.4) fitted to ten 14C dates which includes two pine timber dates. The uppermost peat-derived 14C date, 1170±30 BP (10–8 cm; at least 1 m of peat had been removed by peat cutters), was regarded as unrealistically young and was not used. The pollen profile GRN I spans the interval ca. 5700–1800 BC. The pollen profile indicates that pine grew in the mire from the beginning of the record (5700 BC) to at least 2600 BC ('pine flush' recorded at 2700–2600 BC). This is supported by a Pinus stomatal record and also dendrochronological investigations of pine in the extensive bog at Garrynagran. The dendrochronological investigations enabled two floating chronologies to be constructed spanning the intervals 4530-4350 BC and 3135–2700 BC (fixed by 14C dates from dendro-matched pines). These data, together with the pollen data, serve to emphasise the importance of bog-pine in the region at ca. 3000 BC. Profile GRN I shows a distinct Elm Decline (but little P. lanceolata) that is followed by a Neolithic Landnam (3700–3300 BC). After a long lull in activity, farming impact begins to register again in a substantial way in the early Bronze Age (2300 BC). The macrofossil data provide evidence for mire development including a substantial role for Sphagnum austinii from ca. 2750 BC onwards. LOI and tephra investigations were also carried out. A distinct tephra layer was present (9–4 cm; highest tephra concentration at 6–5 cm; ca. 1450 BC based on age/depth model). The results of the tephra investigations have yet to be published. The research, most of which was carried out as a PhD project by Eneda Jennings (1997), was supported by Forbairt/Eolas (Irish Research Council) and NUIG Postgraduate Fellowship scheme.