Impact of melting of the Laurentide Ice Sheet on sediments from the upper continental slope off southeastern Canada: evidence from Sm–Nd isotopesThis article is one of a series of papers published in this Special Issue on the themePolar Climate Stability Network.

Abstract

We present new Sm–Nd isotope data for sediments from a core located on the continental slope of the St. Pierre Bank of Canada’s east coast. The Nd analyses indicate that the sediments were derived from two principal sources: the North American Shield that yields an average early Proterozoic isotopic signature and a younger Proterozoic signature attributed to Appalachian crustal sources. The Appalachian-sourced sediments predominated during the last glacial maximum (LGM) and were associated with low sedimentation rates (<30 cm/ka), with the exception of a strong North American Shield signature present in a detrital carbonate layer that corresponds to Heinrich Layer 1 (H1). The dominance of the Appalachian signature decreased subsequent to H1. The Appalachian signatures closely follow the distribution of sediments interpreted as locally derived glacial tills, while the North American Shield signatures follow the distribution of hemipelagic mud that was likely deposited by the Labrador Current. The Nd data are consistent with the persistence of the Wisconsinan Ice Sheet coverage of Newfoundland and the Grand Banks after the LGM, although the coverage began to wane prior to 12.5 ka as evidenced by the increasing influence of the Labrador Current. However, an increase in the Appalachian isotope signature at the close of the Younger Dryas event likely indicates the final melting of the ice sheet covering the Grand Banks and the Avalon Peninsula, and the initiation of the Labrador Current’s modern circulation pathway.

A multi-proxy reconstruction of oceanographic conditions around the Younger Dryas–Holocene transition in Placentia Bay, Newfoundland

“…This may be due to presumably persisting cooling effects of enhanced polar water and ice advection by the Labrador Current under the preceding climate regime in combination with strong meltwater discharge from the nearby Newfoundland local glacial ice cover (Shaw et al, 2006;Stevenson et al, 2008). Alternatively, uncertainties in the age model may not entirely be excluded, although the chronology of AI07-14G seems to be robust when looking at the Younger Dryas-Holocene transition.…”

“…The very youngest section of core AI07-14G, representative of the beginning of the Holocene, shows an increase in productivity and a warming of the surface waters which might be linked to the further retreat of the Laurentide ice sheet during this time period (Dyke, 2004;Shaw et al, 2006;Stevenson et al, 2008). This early Holocene warming trend may be linked to the precession-driven summer insolation anomaly reaching a maximum at northern high latitudes between 12 and 10 cal kyrs BP leading to a time-transgressive warming pattern in the (sub)Arctic regions (Kaufman et al, 2004).…”

Evidence for meltwater drainage via the St. Lawrence River Valley in marine cores from the Laurentian Channel at the time of the Younger Dryas

“…Hillaire-Marcel et al (2008) came to a similar conclusion that meltwater events from the Laurentide Ice Sheet probably do not leave easily interpreted salinity signals in δ 18 O records. This is why alternatives were proposed, such as the Mg/Ca ratio (Carlson et al, 2007) or various geochemical signals that can be used to determine the actual source of the meltwater (Carlson et al, 2007;Stevenson et al, 2008;Not and Hillaire-Marcel, 2012;Maccali et al, 2013).…”

Fine scale sediment structure and geochemical signature between eastern and western North Atlantic during Heinrich events 1 and 2

“…Rashid et al / Quaternary Science Reviews xxx (2012) 1e15 11 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 isotopic 3 Nd and 87 Sr/ 86 Sr ratios (Barber, 2001;Farmer et al, 2003;Peck et al, 2007;Stevenson et al, 2008).…”