Sediment Provenance Changes in the Western Arctic Ocean in Response to Ice Rafting, Sea Level, and Oceanic Circulation Variations Since the Last Deglaciation

Abstract

Two sediment piston cores were recovered from the Chukchi‐Alaskan (05JPC) and Canadian Beaufort (02PC) margins to investigate grain‐size, geochemical, and mineralogical compositions. This allowed the reconstruction of changes in detrital sediment provenance and transport related to climate variability since the last deglaciation. The end‐member modeling analyses of grain size indicate that sea ice and nepheloid transport and the Mackenzie River sediment plume are major factors influencing sedimentation in the Chukchi‐Alaskan and Canadian Beaufort margins, respectively. Unmixing of the sediment composition indicates that detrital sediments in core 02PC are derived mainly from the Mackenzie River, whereas sediments from core 05JPC are derived mainly from the Mackenzie River during the deglaciation and include a mixture of Holocene sediments from the Bering Strait, Mackenzie River, and Eurasian margin. The dolomite‐rich ice‐rafted debris recorded in both cores could be related to the different phases of iceberg discharges from the Amundsen Gulf Ice Stream. Quartz and feldspar‐rich ice‐rafted debris dated at 13 and 10.6 ka cal BP (before present) are related to the Lake Agassiz outburst in core 02PC and meltwater discharge from the Brooks Range glaciers in core 05JPC. Detrital proxies in core 02PC support the hypothesis that large meltwater and iceberg discharges from the Lake Agassiz outburst to the Arctic Ocean and Amundsen Gulf ice stream may have triggered the Younger Dryas. Finally, similar trends observed between sea level curves and our detrital proxy suggest that the sea level changes in the western Arctic Ocean have an important influence on the sediment dynamic during the early to middle Holocene.

Quantifying Provenance and Transport Pathways of Holocene Sediments From the Northwestern Greenland Margin

“…The geochemical composition (ED‐XRF) for the three cores (Figure a) confirms the relatively similar composition of cores 204 and 210 compared to core Kane2B (especially with Mg, Al, and Ca). In addition, because aluminosilicates and clay minerals are largely associated with Al, quartz with Si and carbonates are associated with Ca, the ternary plot Al‐Si‐Ca (expressed as oxides; Figure b) was used to obtain a general geochemical classification of the sediments (e.g., Deschamps et al, ; Gamboa et al, ). This complementary diagram shows that the elemental sediment composition also reflects the major distinction between sedimentary sources for core Kane2B (rich in detrital carbonates) and for cores 204 and 210 (similar to average shale; Pourmand et al, ).…”

“…Elemental compositions of sediments were analyzed by energy‐dispersive X‐ray fluorescence (ED‐XRF) spectrometry, using a PANalytical Epsilon 3‐XL. We considered a total of 14 elements (Al, Si, K, Mg, Ca, Ti, Mn, Fe, P, Sr, V, Cr, Zn, and Zr) with analytical procedures similar to Gamboa et al () and Deschamps et al (). Prior to ED‐XRF analysis, loss on ignition was determined gravimetrically by heating the dried samples up to 950 °C for 3 hr.…”

Holocene Changes in Deep Water Circulation Inferred From Authigenic Nd and Hf Isotopes in Sediment Records From the Chukchi‐Alaskan and Canadian Beaufort Margins

“…Next, Sr, Nd, and Hf contained in the sediment oxyhydroxide fraction were leached for approximately 1 hr in a single step using a dilute reducing and complexing solution consisting of 0.005‐M hydroxylamine hydrochloride (HH), 1.5% acetic acid, and 0.03‐M Na‐EDTA, buffered to pH = 4 with suprapur® NaOH. A buffered acetic acid leach step was omitted since biogenic carbonates are negligible in all sediment samples (Deschamps, Montero‐serrano, & St‐Onge, ). The hydroxylamine hydrochloride and acetic acid mixture was tenfold diluted compared with the method of Gutjahr et al () to avoid any potential contamination caused by the leaching of clay minerals.…”

“…On the Canadian Beaufort Shelf and the Chukchi Sea, most of the surficial seabed sediments are predominantly composed of Holocene bioturbated gray to olive‐gray marine silts and clays (Gamboa et al, ; Kobayashi et al, ). The modern sedimentation in the Chukchi Sea is believed to be mainly derived from northeastern Siberia, the northeastern Bering Sea (mainly from the Yukon River and to lesser extents from the Aleutian arc and Anadyr River), and the Mackenzie River, whereas the Canadian Beaufort margin sediment originates primarily from the Mackenzie River basin (Asahara et al, ; Darby et al, ; Deschamps, Montero‐serrano, & St‐Onge, ; Gamboa et al, ; Horikawa et al, ; Kobayashi et al, ; Nelson & Creager, ). Smaller Alaskan rivers have a more local impact but may have been a more important sediment source during the early stages of the last transgression (Hill & Driscoll, ).…”

“…Smaller Alaskan rivers have a more local impact but may have been a more important sediment source during the early stages of the last transgression (Hill & Driscoll, ). During deglaciation and the early Holocene, sediment inputs to the Chukchi‐Alaskan and Beaufort margins were presumably higher due to the rising sea level associated with meltwater and iceberg discharge from the retreat of large ice sheets (Deschamps, Montero‐serrano, & St‐Onge, ).…”