Elsevier

Marine Geology

Volume 445, March 2022, 106752
Marine Geology

Research article
Glaciomarine sediment deposition on the continental slope and rise of the central Ross Sea since the Last Glacial Maximum

https://doi.org/10.1016/j.margeo.2022.106752Get rights and content

Highlights

  • Glaciomarine sedimentation in the continental slope and rise of the Ross Sea

  • Higher geochemical and isotopic properties of the glacial and degalcial sediments

  • More supply of reworked shelf sediments by the glacial advance of Ross Ice Sheet

  • Role of Ross Ice Sheet on the sediment deposition in the central Ross Sea

Abstract

The continental margin of the Ross Sea has been consistently sensitive to the advance and retreat of the Ross Ice Sheet (RIS) between the interglacial and glacial periods. This study examines changes of the glaciomarine sedimentation on the continental slope and rise to the eastern side of Hillary Canyon in the central Ross Sea, using three gravity cores collected at increasing water depths. Besides older AMS 14C ages of bulk sediments, based on the analytical results, sediment lithology was divided into units A, B1, and B2, representing Holocene, deglacial, and glacial periods, respectively. The sedimentation rate decreased as the water depth increased, with a higher sedimentation rate in the deglacial period (unit B1) than the Holocene (unit A). Biological productivity proxies were significantly higher in glacial unit B2 than in interglacial unit A, with transitional values observed in deglacial unit B1. Biological productivity generally decreased in the Antarctic continental margin during the glacial period because of extensive sea ice coverage. The higher biogenic contents in unit B2 are primarily attributed to the increased transport of eroded and reworked shelf sediments that contained abundant biogenic components to the continental slope and rise beneath the advancing RIS. Thus, glacial sedimentation on the continental slope and rise of the central Ross Sea was generally governed by the activity of the RIS, which generated melt-water plumes and debris flows at the front of the grounding line, although the continental rise might have experienced seasonally open conditions and lateral effects due to the bottom current.

Introduction

Approximately 98% of Antarctica is covered with ice; thus, the continental ice plays an important role in the global water cycle and climate change (Pattyn et al., 2018). If the entire Antarctic Ice Sheet (AIS) were to melt, the global sea level would rise as high as ~60 m above the present-day level, which is equivalent to almost half of the range that it fell during the last glacial period (Nakada et al., 2000; DeConto and Pollard, 2016). The AIS is geographically divided into the West Antarctic Ice Sheet (WAIS) and East Antarctic Ice Sheet (EAIS) by the Transantarctic Mountains. The marine-based WAIS is largely below sea level and flows rapidly, compared to the EAIS (Fretwell et al., 2013). Hence, the WAIS is more sensitive to changes in seawater temperature and sea level (DeConto and Pollard, 2016). The AIS plays an important role in controlling global climate change, with variations in the extent of the AIS affecting the surface albedo, global sea level, ocean circulation, and the production of bottom water (e.g., Ogura and Abe-Ouchi, 2001; Mackensen, 2004; Ritz et al., 2015).

The WAIS discharges ice into the central and eastern sectors of the Ross Sea, while the EAIS supplies ice to the western sector (Rignot et al., 2008). The extensive Ross Ice Sheet (RIS) primarily developed from portions of both with a comparatively higher contribution from the WAIS. The RIS advanced to the shelf edge in the eastern Ross Sea during the Last Glacial Maximum (LGM) (Fig. 1; Anderson et al., 2019, Lowry et al., 2020). Contrastingly, the RIS did not reach the shelf edge in the central and western Ross Sea, where it ceased its advance at Mawson Bank, Pennell Bank, JOIDES Basin, and the Pennell Trough during the LGM (Fig. 1; Howat and Domack, 2003; Anderson et al., 2019; Prothro et al., 2020; Torricella et al., 2021). The advance and retreat of the RIS significantly influences the depositional processes and environments in the Ross Sea (Domack et al., 1999; Anderson et al., 2014; Prothro et al., 2018; Smith et al., 2019; King et al., 2022).

The Antarctic sedimentary and climate history during the last glacial period, the glacial termination, and the Holocene has been subject to extensive modeling and empirical reconstruction over the past few decades (e.g., Barker et al., 1999; Yokoyama et al., 2000; Licht et al., 2005; Weber et al., 2011; Golledge et al., 2013; Anderson et al., 2014, Anderson et al., 2019; Mezgec et al., 2017; Bart et al., 2018; Prothro et al., 2018, Prothro et al., 2020; Khim et al., 2021; Melis et al., 2021; Torricella et al., 2021; King et al., 2022). The unique sedimentary successions that are associated with RIS activity on the continental shelf of the Ross Sea have thus been well established. Anderson et al. (2014) reported that diamicton was deposited extensively in the subglacial or glacial-marine setting of the continental shelf during the LGM. Diamicton or subglacial till was also found to have been deposited widely under the grounded ice sheet during the LGM (Prothro et al., 2018; Smith et al., 2019). At this time, frequent debris flows and turbidity currents from the front of the grounding line supplied large quantities of sediments to the deep basin (Barker et al., 1999; Weber et al., 2011). During the glacier retreat (i.e., transition time or deglaciation), the ice shelf and the distance from the grounding line controlled the sedimentary processes in the continental shelf (Bart et al., 2017; Prothro et al., 2018). The supply of ice-rafted debris (IRD) increased and laminated sandy silt was deposited as a result of the seasonal melt-water outflow from the front of the grounding line (e.g., Smith et al., 2019). The warm climate and seasonally open marine conditions in the Holocene thus allowed a high primary productivity of diatoms in the surface water, leading to the deposition of abundant biogenic sediments (i.e., siliceous mud and ooze) on the western side of the continental shelf, while the Holocene muds on the eastern side are characterized by scarce and reworked diatoms (Langone et al., 1998; Domack et al., 1999; Melis and Salvi, 2009; Anderson et al., 2014; McGlannan et al., 2017).

The glaciomarine sedimentation on the continental slope and rise around Antarctica was also influenced by the dynamics of the AIS (Pudsey, 2000; Caburlotto et al., 2010; Kim et al., 2020; Hillenbrand et al., 2021). During the glacial period, the AIS advanced beyond the continental shelf toward the shelf edge on most of the Antarctic continental margins (e.g., the Ross Sea, the Weddell Sea, and around the Antarctic Peninsula), resulting in the transportation of eroded and unsorted sediments from the continental shelf toward the upper continental slope by melt-water (Escutia et al., 1997; Weber et al., 2011; Khim et al., 2021). The turbidity current also transported the eroded and reworked hemipelagic sediments of the continental shelf farther onto the lower continental slope and rise (Kuvaas and Leitchenkov, 1992; Weber et al., 1994; Escutia et al., 1997; Stow and Smillie, 2020). Bottom currents formed contourite deposits on the Antarctic continental margin under the high sedimentation rates and lack of bioturbation that occurred during the glacial period (Pudsey, 1992; Gilbert et al., 1998; Lucchi and Rebesco, 2007; Rebesco et al., 2014). Such depositional processes led to an increase in the sedimentation rate in the continental slope and rise (Pudsey, 2000; Weber et al., 2011; Rebesco et al., 2014; Stow and Smillie, 2020); however, evidence for the erosion and reworking of shelf sediments has not yet been reported.

Most previous studies on the continental slope and rise of the Ross Sea have examined the western part of the region (Tolotti et al., 2013; Kim et al., 2020; Khim et al., 2021; Melis et al., 2021; Torricella et al., 2021). In the Central Basin to the western of the Iselin Bank, the terrigenous sediment supply increased during the glacial period due to strong glacial influence (Torricella et al., 2021). The following deglaciation is characterized by an abrupt increase in biogenic materials consisting mainly of diatoms and silicoflagellates, which led to the maximum of primary production. Then, the Holocene period is characterized by high, albeit lower, biogenic flux (Hartman et al., 2021). The similar results were reported by Kim et al. (2020) using the two gravity cores from the western side of the Iselin Bank.

The previous studies have been carried out less on the eastern side of Iselin Bank than on its western side. The physical properties (i.e., magnetic susceptibility, bulk density, and P-wave velocity) of the sediments comprising the continental slope on the eastern side of the bank indicate that sedimentation patterns were different between the glacial and interglacial periods (Bonaccorsi et al., 2000). For example, structureless or stratified diamicton were deposited during the glacial period, while laminated sediments that were affected by biogenic productivity were commonly deposited during the interglacial period. However, the sedimentary records are incomplete and discontinuous because the studied cores were collected from channel systems. Furthermore, the geochemical and isotope signatures of the continental slope and rise sediments on the eastern part of the Iselin Bank have not yet been studied.

In this study, we investigated three sediment cores that were collected across the continental slope and rise on the east of Hillary Canyon in the central Ross Sea (Fig. 1). For the first time, multi-proxy data, mainly focused on geochemical and isotope signatures, were used to understand the glaciomarine depositional processes related to the RIS, emphasizing the enhanced re-sedimentation of shelf sediments in the continental slope and rise to the east of the Hillary Canyon in response to the advance of the RIS during the glacial periods.

Section snippets

Study area

The Ross Sea is characterized by steep shelf edges, many north-northeast trending basins, troughs and banks (the Drygalski, JOIDES, and Glomar-Challenger basins, Pennell Trough, and the Crary, Iselin, Mawson, and Pennell banks), and a landward deepening of the continental shelf (Fig. 1). The banks are generally shallower than 500 m. The continental shelf in the Ross Sea is geographically divided into eastern and western sectors at 180°. The eastern continental shelf consists of broad basins and

Materials and methods

Three gravity cores (GC1, GC2, and GC3) and three box cores (BC1, BC2, and BC3) were obtained at three stations (RS14-C1, C2, and C3) across the continental slope and rise on the east of Hillary Canyon (central Ross Sea) during the XXIX Italian PNRA (National Antarctic Research Program) Expedition (PNRA–ENEA/UTA, 2014) under the Italian project ROSSLOPE II (Fig. 1, Table 1). The box cores were used to check the extent of loss from the gravity cores and the core-top age, whereas the gravity

Core-top comparison

A fair amount of material from the top of gravity cores was lost during the coring process. The geochemical properties of the box core and the upper part of the gravity core were compared to estimate the core-top loss. Fig. 2 shows a comparison of TOC, TN, and CaCO3 contents between the two cores, for which the variation patterns were found to coincide. Differences of <0.06% for TOC, <0.01% for TN, and <0.2% for CaCO3 were obtained for the core-tops at sites C1 and C2, while those of 0.3% for

Sediment deposition on the continental slope and rise of the central Ross Sea

The core-top ages for GC3, GC2, and GC1 were found to be 1.5 ka, 5.7 ka, and 2.5 ka, respectively (Table 2). Such old ages are generally observed in core-tops from the Antarctic Ocean (Licht et al., 1996; Andrews et al., 1999). The older AMS 14C ages at the core-top sediments of box cores and gravity cores are due to a combination of the old carbon effect in the seawater and surface sediment loss during coring operation. The old carbon effect depends on the inclusion of old “particulate”

Conclusions

To comprehend the changes in glaciomarine sedimentation on the continental slope and continental rise of the central Ross Sea since the LGM, box and gravity cores were obtained at three sites (C1, C2, and C3), on the eastern side of Hillary Canyon. The sedimentological, geochemical, and isotopic properties of the core sediments were analyzed along with AMS 14C dating of the bulk sediments. A comparison of the box cores with the tops of the gravity cores demonstrated the minimal core-top loss of

Access to the data

All the relevant data in this study were summarized in Research Data File of Supplement File and uploaded in PANGAEA.

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgements

The captain, crew, and all onboard of the R/V ITALICA together with the technicians and researchers associated with the XXIX PNRA Expedition in 2014 are thanked for the core sampling in the framework of the PNRA-ROSSLOPE II Project. We appreciate Dr. M. Weber and an anonymous reviewer for their critical and constructive comments to improve the data interpretation on the depositional processes in the continental slope and rise of the Ross Sea. This study was carried out by the National Research

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