Sedimentary environmental change induced from late Quaternary sea-level change in the Bonaparte Gulf, northwestern Australia
Low-latitude continental shelves, mixed siliciclastic–carbonate sedimentary systems, provide an understanding of sedimentary environments driven by paleoclimatological processes. The Bonaparte Gulf, northwestern Australian continental shelf, is among the widest in the world, ranging to 500 km, with shallow carbonate terraces and platforms that were exposed during periods of lower sea level. The dominant sediments type switches between carbonate and siliciclastic over a sea-level cycle. However, the mechanism of sedimentary environmental change in the Bonaparte Gulf is not clearly understood. Here, we present a record of sedimentary environmental change from ca. 24 to 35 ka that is related to sea-level variability and exposure of carbonate terraces and platforms. Multi-proxy data from a marine sediment core show a sea-level change induced switch in sedimentary environment from siliciclastic to carbonate-dominated sedimentation during the last glaciation. Radiocarbon ages constrain the timing of this switch to ca. 26 ka, associated with a local sea-level fall of −90 m.
KeywordsSedimentary environment Radiocarbon dating Bonaparte Gulf Northwestern Australia Last Glacial Maximum Sea-level change
Intertropical Convergence Zone
last glacial maximum
total organic carbon
mass accumulation rate
dry bulk density
liner sedimentation rate
Continental shelves are the main transport pathway of sediments from land to sea, playing an important role in the earth’s surface system. The sedimentary environment of low-latitude mixed siliciclastic–carbonate continental shelves is strongly influenced by sea-level change and fluvial processes (Dunbar and Dickens 2003; Schlager et al. 1994; Webster et al. 2012). Detailed research on sedimentary environments of continental shelves improves our understanding of monsoonal intensity and sea-level variability (Bourget et al. 2012; Yokoyama et al. 2000).
Today, northwestern Australia experiences a semi-arid climate. Southeast winds prevail in the Austral summer and northwesterly winds in the Austral winter. There is a strong rainfall seasonality during the Austral summer (De Deckker et al. 2014; Gallagher et al. 2014a). This is the Australian monsoon, the intensity of which has varied with the movement of the Intertropical Convergence Zone (ITCZ) over the past 30,000 years (cf., Ding et al. 2013; Kuhnt et al. 2015; Mohtadi et al. 2011).
This mixed siliciclastic–carbonate and shallow continental shelf is influenced by monsoonal intensity and sea-level change (Gallagher et al. 2014b). Petroleum exploration and paleoclimatic reconstructions have driven interest in the long-term understanding of the sedimentary environment in this region (Anderson et al. 2011; Nicholas et al. 2014). Moreover, mixed siliciclastic–carbonate sedimentary environments in low-latitude and semi-enclosed marginal marine environments provide information on the mechanism of paleoclimatic and hydrologic change (cf., Bahr et al. 2005; Isaack et al. 2016; Soulet et al. 2011). However, our understanding of late Quaternary evolution of the Bonaparte sedimentary environment is much less well constrained.
Here, we document the evidence of environmental changes due to the exposure of these carbonate terraces and platforms before the LGM. The Bonaparte Gulf is a “far-field” (cf., Yokoyama and Esat 2011), tectonically stable site extremely suitable for reconstruction of sea level due to past continental ice-volume change (De Deckker and Yokoyama 2009; Ishiwa et al. 2016; Yokoyama et al. 2000, 2001b). We also describe the sedimentary consequences of past environmental change from a marine piston core (KH11-1-PC01) using Ca/Ti ratios, total organic carbon (TOC) and total nitrogen (TN), constrained by radiocarbon dating.
Core KH11-1-PC01 was recovered from a water depth of 140 m during the KH11-1 cruise of R/V Hakuho-Maru during January and February 2011 (Fig. 1). The top 600 cm interval of core KH11-1-PC01 (core recovery length: 951 cm) was analyzed as it is within the range of radiocarbon dating. Well-preserved macrofossils (primarily bivalves) were collected for radiocarbon dating.
Physical properties and geochemical analysis
Color reflectance was measured at 2-cm intervals after splitting the cores on ship using a Minolta CM-2002 photospectrometer. At the same time, magnetic susceptibility was measured at 2-cm intervals using a Bartington Instruments MS2C system.
Age results of macrofossils in core KH11-1-PC01
14C age (BP)
Calendar age (cal BP) 1σ
Calendar age (cal BP) 2σ
2320 ± 30
1940 ± 40
1940 ± 90
10,510 ± 40
11,730 ± 140
11,670 ± 260
9750 ± 40
10,650 ± 50
10,660 ± 110
18,370 ± 50
21,770 ± 100
21,750 ± 200
590 ± 130
200 ± 140
20,290 ± 70
23,930 ± 120
23,920 ± 250
20,290 ± 70
23,940 ± 120
23,930 ± 250
20,940 ± 70
24,710 ± 180
24,730 ± 320
20,950 ± 140
24,740 ± 240
24,760 ± 430
20,910 ± 70
24,660 ± 170
24,690 ± 310
23,320 ± 210
27,270 ± 200
27,160 ± 450
23,280 ± 70
27,250 ± 100
27,240 ± 200
24,280 ± 90
27,890 ± 100
27,920 ± 220
25,330 ± 280
28,990 ± 300
29,020 ± 610
30,060 ± 230
33,820 ± 190
33,820 ± 410
35,020 ± 550
39,160 ± 580
39,270 ± 1280
Calendar ages were calculated using Oxcal (Ramsey and Lee 2013) with Marine 13 and Intcal 13 (Reimer et al. 2013) as calibration curves for macrofossils and organic matter ages. The local reservoir correction, ΔR, is undefined in the Bonaparte Gulf but expected to be minor (cf., O’Connor et al. 2010). Thus, we made no local correction, consistent with previous works (Ishiwa et al. 2016; Yokoyama et al. 2000, 2001b).
The age–depth model of KH11-1-PC01 was constrained using the BACON model (Blaauw and Christen 2011) based on macrofossil ages, since organic matter ages are affected by the transportation time of terrigenous components (cf., Ishiwa et al. 2016; Nakamura et al. 2016). This model uses the Bayesian analysis and Monte Carlo methods to constrain the smoothing age–depth model using the R statistical software package (cf., De Vleeschouwer et al. 2012; Shanahan et al. 2012).
Calculation for exposure percentage in the Bonaparte Gulf
The area of carbonate terraces and platforms in the Bonaparte Gulf exposed during lower sea level was calculated using the bathymetric dataset from Whiteway (2009). The data were interpolated to a uniform resolution of 0.5 min latitudinally and longitudinally. We calculated the area of exposure along the sea-level curve and set the exposure percentage to 0% at relative sea level = 0 m and to 100% at relative sea level = −120 m. This percentage was calculated at a 5-m interval.
Lithology and physical properties
XRF core scanning and geochemical analysis
Ca counts are constant at 600,000 from 600 to 200 cm, increasing to ~800,000 counts at 180 cm (Fig. 2). There is a sharp drop at 70 cm. From 30 cm to the core top, Ca decreases to 400,000 counts. Ti counts gradually decrease from 600 to 200 cm, sharply decreasing to 20,000 counts at ~200 cm (Fig. 2). There is a peak of ~25,000 counts from 30 cm to the core top.
TOC is ~0.7% from 600 to 200 cm, sharply increasing to 1.5% at ~180 cm with a peak of ~0.8% at ~510 cm (Fig. 2). TOC is variable in the upper 40 cm of core. C/N ratios reach a maximum of ~15 at 510 cm, then maintain a value of ~9 through the depth interval of 500–180 cm, above which values are relatively constant at ~13 (Fig. 2). In the upper 60 cm, ratios decrease upwards to the core top.
Age results of organic matter in core KH11-1-PC01
14C age (BP)
Calendar age (cal BP) 1σ
Calendar age (cal BP) 2σ
1790 ± 30
1700 ± 80
1720 ± 100
7650 ± 30
8430 ± 20
8450 ± 60
7040 ± 70
7870 ± 70
7840 ± 140
21,040 ± 80
25,400 ± 120
25,390 ± 230
21,450 ± 60
25,780 ± 80
25,770 ± 150
21,180 ± 70
25,540 ± 110
25,510 ± 220
22,200 ± 110
26,390 ± 170
26,440 ± 350
21,780 ± 100
26,000 ± 90
26,010 ± 200
25,060 ± 110
29,090 ± 170
29,110 ± 320
24,370 ± 90
28,440 ± 150
28,420 ± 280
25,090 ± 90
29,120 ± 160
29,140 ± 300
26,360 ± 130
30,700 ± 150
30,660 ± 300
30,600 ± 150
34,560 ± 170
34,530 ± 330
32,810 ± 200
36,720 ± 330
36,930 ± 680
Exposure of carbonate terraces and platforms in Bonaparte Gulf
Interpretation and discussion
Sedimentary environmental change during late Quaternary
The variation in terrigenous input is interpreted to be related to changes in TOC flux and C/N ratios (cf., Ishiwa et al. 2016; Yu et al. 2010; Mackie et al. 2005). The terrigenous sediment supply increased after ca. 26 ka, as indicated by the increased TOC, C/N ratios, and sedimentation rate (Figs. 5, 6). Increased terrigenous material during this time would make mixed marine-terrigenous organic matter older, increasing the offset from macrofossil ages (Fig. 3). Additionally, mass accumulation rate calculated by the BACON model supports the exposure of carbonate terraces and platforms during this period (Fig. 5).
Mechanism for sedimentary environmental change
Sedimentation patterns would have fluctuated with the relative strength of monsoon (Gallagher et al. 2014b; Kuhnt et al. 2015). The Australian Monsoonal precipitation pattern is sensitive to latitudinal ITCZ migration (Lewis et al. 2011), while speleothem records from this region indicate low monsoon variability at this time (Lewis et al. 2011; Partin et al. 2007), consistent with marine and terrestrial records (Fitzsimmons et al. 2013; Reeves et al. 2013) that show a northward ITCZ position. We suggest that the changes in monsoonal variability are not strong enough to control the sedimentary facies in the Bonaparte Gulf. A relative change in carbonate sediment flux increased at ca. 26 ka as shown by physical properties and geochemical analysis (Fig. 5). Rivers passing through the continent would have supplied siliciclastic sediments to the depression (Gingele et al. 2001; Gingele and De Deckker 2003). During this period, the supply of siliciclastic sediments did not change much due to the weak variability of monsoonal intensity. By contrast, the carbonate supply increased due to the exposure of carbonate terraces and platforms.
Sea level below −90 m resulted in sufficient exposure of carbonate terraces and platform to increase the flux of carbonate sediments (Fig. 7). During sea-level highstands, much of the shelf was submerged. During sea-level lowstands, the carbonate terraces and platforms were exposed and the Bonaparte Depression was semi-enclosed from the Timor Sea. The relative area of exposure was an important control on the sedimentary facies of the gulf.
While the hydro-isostatic effects in the Bonaparte Gulf do not significantly affect to the current interpretation (Yokoyama et al. 2000, 2001b), this factor cannot be entirely discounted due to paleotopography and paleo-water depth effects. Yokoyama et al. (2000, 2001b) estimated the amplitude of this effect (offset between the global sea level and relative sea level) is less than 20 m. Therefore, the bathymetry in Fig. 7 has an error of 10% due to hydro-isostasy effects.
These observations indicate that the sedimentary environment in the Bonaparte Gulf is primarily driven by sea-level variability due to the distinctive topography with its central depression surrounded by higher-level carbonate terraces and platforms. Exposure of carbonate terraces and platforms with a sea-level fall enhances sedimentary environmental change, characterized by carbonate sediment production and transportation. Paleobathymetry would also likely have affected local ocean circulation patterns and tidal ranges.
Sea-level change prior to the LGM has been estimated using the uplifted coral on the Huon Peninsula, indicating that sea level fell from −70 to −110 m from 30 to 24 ka (Cutler et al. 2003; Yokoyama et al. 2001c). This is consistent with sea level from the Red Sea (Siddall et al. 2003), which falls ~20 m from 28 to 26 ka (−80 to −100 m).
Comparison to other regions
Mixed carbonate-siliciclastic sedimentary systems are observed in low-latitude tropical regions. Isaack et al. (2016) present a sea-level driven model of sediment dynamics based on a multi-proxy record in the barrier-reef lagoon of Bora Bora in the South Pacific. They suggest that carbonate sediment produced in marginal reef areas is transported to the lagoons. This mechanism indicates that carbonate terraces and platforms in the Bonaparte Gulf can be the source of carbonate sediments, generating the variation of geochemical signal in the core.
The Black Sea became a semi-enclosed marginal sea, similar to the Bonaparte Gulf, during lowering sea levels (Bahr et al. 2005), and reconnected to the Mediterranean Sea at ~9000 years ago in association with rising sea level (Soulet et al. 2011). Geochemical data suggest that the hydrologic system has changed from lacustrine to marine, controlled by a water depth of sills connected to Mediterranean Sea. By contrast, during sea-level lowstands, the Bonaparte Gulf connected to the Timor Sea mainly by paleochannels at a water depth of ~200 m (Fig. 1; Yokoyama et al. 2000, 2001a). The sedimentary environment in the Bonaparte Gulf is influenced by the exposure of carbonate terraces and platforms, which played a role in pathways of carbonate sediments.
Geochemical and chronological records from a piston core in the Bonaparte Gulf, northwestern Australia, show a sedimentary environmental change at ca. 26 ka. Carbonate terraces and platforms and their deeply incised paleochannels play an important role in this paleoenvironmental change.
Ca/Ti ratios as an indicator of changes in mixed siliciclastic–carbonate sediments increased at ca. 26 ka, indicating the enhanced supply of carbonate sediments. TOC and C/N ratios as an indicator of terrigenous input also increased. The changes in these geochemical signals can be explained by the exposure of carbonate terraces and platforms.
Precipitation patterns shift can drive the change in sediment supply. However, during the period we investigate, the variability of Australian monsoon was not strong enough to change the sedimentary environment. By contrast, global sea-level fall to −90 m occurred at ca. 26 ka, driving the exposure of carbonate terraces and platforms and the switch from siliciclastic to carbonate-dominated sedimentation. Our research provides an understanding of a sea-level driven sedimentary environmental change in low-latitude mixed siliciclastic–carbonate environment.
TI carried out this work and YY managed the cruise KH11-1 and also supervised this work. YM supported measurement of this work. MI managed measurement in CMCR and gave useful comments. SO interpreted results and helped to write the final manuscript. YY, YM, MI and SO joined the cruise of KH11-1. All authors read and approved the final manuscript.
We greatly appreciate the members of the cruise of KH11-1 for collecting and subsampling the sediment cores. The reviewers, Dr. S. Nichol and Dr. S. Gallagher, gave us the useful and valuable comments to revise this paper. This study was supported by the Center for Advanced Marine Core Research (CMCR), Kochi University, cooperative research program (11A031, 11B039) and grants from the Japan Society for the Promotion of Science (JSPS) KAKENHI (JP26247085, JP15KK0151) and JSPS Fellows DC2 (16J04542).
The authors declare that they have no competing interests.
- Anderson TJ, Nichol S, Radke L, Heap AD, Battershill C, Hughes M, Siwabessy PJ, Barrie V, Alvarez de Glasby B, Tran M, Daniell J (2011) Seabed environments of the Eastern Joseph Bonaparte Gulf, Northern Australia: GA0325/Sol5117-Post-survey Report. Geosci Aust RecordGoogle Scholar
- Bourget J, Ainsworth RB, Nanson R (2013) Origin of mixed carbonate and siliciclastic sequences at the margin of a “giant” platform during the Quaternary (Bonaparte Basin, NW Australia). In: Verwer K, Playton TE, Harris PM (eds) Deposits, architecture, and controls of carbonate margin, slope, and basinal settings, special publication 105. SEPM (Society for Sedimentary Geology), TulsaGoogle Scholar
- Bourget J, Ainsworth RB, Thompson S (2014) Seismic stratigraphy and geomorphology of a tide or wave dominated shelf-edge delta (NW Australia): process-based classification from 3D seismic attributes and implications for the prediction of deep-water sands. Mar Pet Geol 57:359–384CrossRefGoogle Scholar
- Gallagher SJ, Fulthorpe CS, Bogus KA (2014a) Reefs, oceans, and climate: a 5 million year history of the Indonesian Throughflow, Australian monsoon, and subsidence on the northwest shelf of Australia. International Ocean Discovery Program Scientific Prospectus 356Google Scholar
- Gingele FX, De Deckker P (2003) Fingerprinting Australia’s rivers using clays and the application for the marine record of rapid climate change. Advances in Regolith. ANU Research Publications, pp 140–143Google Scholar
- Isaack A, Gischler E, Hudson JH, Anselmetti FS, Lohner A, Vogel H, Garbode E, Camoin GF (2016) A new model evaluating Holocene sediment dynamics: insights from a mixed carbonate—siliciclastic lagoon (Bora Bora, Society Islands, French Polynesia, South Pacific). Sed Geol 343:99–118CrossRefGoogle Scholar
- Ishiwa T, Yokoyama Y, Miyairi Y, Obrochta S, Sasaki T, Kitamura A, Suzuki A, Ikehara M, Ikehara K, Kimoto K, Bourget J, Matsuzaki H (2016) Reappraisal of sea-level lowstand during the Last Glacial Maximum observed in the Bonaparte Gulf sediments, northwestern Australia. Quat Int 397:373–379CrossRefGoogle Scholar
- Lewis SC, Gagan MK, Ayliffe LK, Zhao J, Hantoro WS, Treble PC, Hellstrom JC, LeGrande AN, Kelley M, Schmidt GA, Suwargadi BW (2011) High-resolution stalagmite reconstructions of Australian–Indonesian monsoon rainfall variability during Heinrich stadial 3 and Greenland interstadial 4. Earth Planet Sci Lett 303:133–142CrossRefGoogle Scholar
- Ramsey CB, Lee S (2013) Recent and planned developments of the program oxcal. Radiocarbon 55:720–730Google Scholar
- Reeves JM, Bostock HC, Ayliffe LK, Barrows TT, De Deckker P, Devriendt LS, Dunbar GB, Drysdale RN, Fitzsimmons KE, Gagan MK, Griffiths ML, Haberle SG, Jansen JD, Krause C, Lewis S, McGregor HV, Mooney SD, Moss P, Nanson GC, Purcell A, van der Kaars S (2013) Palaeoenvironmental change in tropical Australasia over the last 30,000 years—a synthesis by the OZ-INTIMATE group. Quat Sci Rev 74:97–114CrossRefGoogle Scholar
- Reimer PJ, Bard E, Bayliss A, Beck JW, Blackwell PG, Ramsey CB, Buck CE, Cheng H, Edwards RL, Friedrich M, Grootes PM, Guilderson TP, Haflidason H, Hajdas I, Hatte C, Heaton TJ, Hoffmann DL, Hogg AG, Hughen KA, Kaiser KF, Kromer B, Manning SW, Niu M, Reimer RW, Richards DA, Scott EM, Southon JR, Staff RA, Turney CSM, van der Plicht J (2013) Intcal13 and marine13 radiocarbon age calibration curves 0–50,000 years cal bp. Radiocarbon 55:1869–1887CrossRefGoogle Scholar
- Riethdorf JR, Thibodeau B, Ikehara M, Nurnberg D, Max L, Tiedemann R, Yokoyama Y (2015) Surface nitrate utilization in the Bering sea since 180kA BP: insight from sedimentary nitrogen isotopes. Deep Sea Res Part II Top Stud Oceanogr:1–14Google Scholar
- Schlager W, Reijmer JJG, Droxler A (1994) Highstand shedding of carbonate platforms. J Sediment Res B64:270–281Google Scholar
- Shanahan TM, Beck JW, Overpeck JT, McKay NP, Pigati JS, Peck JA, Scholz CA, Heil CW, King J (2012) Late Quaternary sedimentological and climate changes at Lake Bosumtwi Ghana: new constraints from laminae analysis and radiocarbon age modeling. Palaeogeogr Palaeoclimatol Palaeoecol 361–362:49–60CrossRefGoogle Scholar
- Webster JM, Beaman RJ, Puga-Bernabeu A, Ludman D, Renema W, Wust RAJ, George NPJ, Reimer PJ, Jacobsen GE, Moss P (2012) Late Pleistocene history of turbidite sedimentation in a submarine canyon off the northern Great Barrier Reef, Australia. Palaeogeogr Palaeoclimatol Palaeoecol 331–332:75–89CrossRefGoogle Scholar
- Whiteway T (2009) Australian Bathymetry and Topography Grid, June 2009. Scale 1:5000000. Geoscience Australia, CanberraGoogle Scholar
Open AccessThis article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.