Quaternary Sedimentary Processes and Budgets in Orphan Basin, Southwestern Labrador Sea

• Published in: Quaternary Research
• Main Authors: Hiscott, Richard N., Aksu, Ali E.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Cambridge University Press (CUP) 1996
• Subjects: Barents Sea; Labrador Sea; Newfoundland
• Online Access: http://dx.doi.org/10.1006/qres.1996.0017; http://api.elsevier.com/content/article/PII:S0033589496900174?httpAccept=text/xml; http://api.elsevier.com/content/article/PII:S0033589496900174?httpAccept=text/plain; https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0033589400024674

Abstract The continental slope in Orphan Basin, northeast of Newfoundland, is underlain by several seaward-thinning debris-flow wedges alternating with acoustically stratified, regionally extensive, mainly hemipelagic sediments. δ 18 O stratigraphy and volcanic ash layers in a 11.67-m core indicate that the uppermost debris-flow wedge formed during the last of several sea-level lowstands in isotopic stages 2–4. Similarly, seismic reflection correlation of dated levels at DSDP Site 111 with the Orphan Basin succession suggests that two deeper debris-flow wedges were deposited during oxygen isotopic stages 6 and 8. The oldest of the debris-flow deposits in at least three of the wedges formed well into the corresponding glacial cycle, after ice sheets had reached the edge of the continental shelf. Slower deposition by hemipelagic processes and ice rafting formed the acoustically stratified units, including Heinrich layers. The youngest three debris-flow wedges each have volumes of 1300–1650 km 3 . Approximately two-thirds of this material is attributed to glacial erosion of Mesozoic and Tertiary strata beneath the Northeast Newfoundland Shelf. The remainder is believed to have been derived by glacial erosion of older bedrock that now forms the island of Newfoundland. The observed sediment volumes and the inferred basal and upper ages of the debris-flow wedges imply an average glacial denudation rate of about 0.13 mm/yr for this older bedrock, and an average of about 60 m of glacial bedrock erosion since oxygen isotope stage 22. This denudation rate is similar to estimates from the Barents Sea region off Norway.