Exploring the Deep Sea and Beyond themed issue Linking a late Miocene–Pliocene hiatus in the deep-sea Bounty Fan off South Island, New Zealand, to onshore tectonism and lacustrine sediment storage Kathleen M. Marsaglia1, Candace E. Martin2, Christopher Q. Kautz2, Shawn A. Shapiro1, and Lionel Carter3 1Department of Geological Sciences, 18111 Nordhoff Street, California State University, Northridge, California 91330-8266, USA 2Department of Geology, University of Otago, P.O. Box 56, Dunedin, 9054, New Zealand 3Antarctic Research Centre, Victoria University Wellington, P.O. Box 600, Wellington 6140, New Zealand ABSTRACT and tectonic events that affect fl uvial-deltaic some extent in the source region, above the slope systems within their source areas and can be (e.g., Normark et al., 2009). So it is very fi tting The cored record at Ocean Drilling Pro- used to reconstruct rates of continental erosion that our Bounty Fan example be included in a gram Site 1122, located on the levee of the (e.g., Burbank et al., 1993; Clift, 2006; Clift volume dedicated to his memory and research. Bounty Fan off southeastern New Zealand, and Blusztajn, 2005; Hoorn et al., 1995). This shows a major late Miocene to Pliocene potential is often not realized. For example, con- BOUNTY TROUGH AND FAN SYSTEM (11.0–3.5 Ma) hiatus in sedimentation. This cerns about autogenic switching of submarine hiatus straddles a period of major uplift in fan lobes and stratigraphic completeness on the The Cenozoic Bounty Channel (Fig. 1) devel- the Southern Alps where the rivers that feed Indus Fan west of India forced Clift et al. (2002) oped in a Late Cretaceous continental rift, the sediment to the Bounty Fan are ultimately to focus instead on the shelf-margin stratigraphic Bounty Trough (Carter et al., 1994). This aban- sourced. There are no signifi cant changes record to address sediment budgets. In contrast, doned rift is currently proximal to or within a in sediment provenance across this inter- on the Bengal Fan east of India, no pronounced zone of transpressional deformation originat- val. We link this hiatus to a combination of breaks in sedimentation were observed (Cochran ing at the Alpine fault plate margin near the rift decreased sediment supply owing to tectonic et al., 1989). Intraplate submarine fan systems apex in southern South Island. Source river(s) disruption of fl uvial drainage and a roughly on Atlantic-style passive margins, where eustatic draining this transpressional tectonic highland simultaneous increase in bottom-current and climatic processes are thought to dominate, feed sediment across a wave-dominated shore- strength. Evidence for this scenario includes are not immune to tectonic signals in that they line onto a wave-dominated continental margin the distribution of current-generated struc- can be created or infl uenced by distant plate- where Neogene deposition has been strongly tures in the core, the relative timing of an marginal tectonic events that reorganize drainage controlled by eustatic fl uctuations of sea level onshore transition from fl uvial to lacustrine patterns (e.g., Hoorn et al., 1995) or affect sedi- (e.g., Carter et al., 1985). Seismic profi les across sedimentation, and a potential post-hiatus ment provenance (e.g., Potter, 1986). the shelf show it to be covered by thin sediment pulse of more weathered sediment into the The Bounty Fan system off South Island, wedges that pinch out landward (Carter et al., Bounty Fan. This sediment pulse was pos- New Zealand, combines aspects of both oro- 1986). Shelf sediments include modern, relict- sibly associated with the reestablishment of genic and passive systems. Like the Bengal sys- palimpsest terrigenous sand and gravel, as well throughgoing drainage and the erosion and tem mentioned above, the Bounty system exhib- as bioclastic sediments (Carter et al., 1985, 1986). fl ushing of stored alluvial to lacustrine sedi- its a major temporal disconnect from source to During highstands, bedload and coarse suspended ments through the system. Thus the Bounty sink, with a period of tectonism in the source load contribute to the inner shelf prism with fi ne Fan provides an excellent example of how the orogen (Southern Alps) correlating to a major suspended load moving along and across shelf complex interplay between tectonic and pale- submarine hiatus on the passive-margin Bounty to contribute to local shelf depocenters in the lee oceanographic forces can affect the sedimen- Fan instead of a major sediment pulse as might of major promontories and a proximal slope-fan tary record in deep-marine systems. be expected. To fully understand the implication complex (Otago fan, Fig. 2A) (Carter and Carter, of a major hiatus in Bounty Fan sedimentation 1993). During lowstands, sediment was dispersed INTRODUCTION documented at Ocean Drilling Program Site mainly across the shelf to contribute directly to 1122, we evaluated the entire source-to-sink the proximal Otago slope-fan complex, a series In determining budgets for sediment fl ux to the system, combining previously published petro- of coalescing fans fed by nine major submarine deep sea, all parts of the system must be exam- logical, sedimentological, and stratigraphic data canyons along the Otago continental slope (Carter ined (Clift, 2006) rather than just proximal (e.g., sets from onshore and offshore segments with and Carter, 1988), or to long distant transport via Burbank et al., 1993) or distal (e.g., Rea, 1992) some new geochemical data. a series of three submarine feeder channels that segments. This is the source-to-sink approach William Normark also embraced such a merge into the 900-km-long Bounty Channel promoted by Driscoll and Nittrouer (2000) that holistic approach to deep-sea fan formation (Figs. 1and 2; Carter and Carter, 1988). Note that has been successfully applied on margins across and evolution. As his work on deep-sea fans the Otago fan complex has not been drilled, but the globe including North Island, New Zealand evolved (e.g., Normark, 1970, 1974; Normark Carter and Carter (1993) infer it to potentially be (Carter et al., 2010). Large submarine fan sys- et al., 1984; Piper and Normark, 2001), so did of late Pliocene or younger age. tems associated with major orogens such as the his reali zation that the answers to submarine The Bounty Channel follows the Bounty Himalayas potentially record climatic, eustatic, fan evolution, the ultimate sediment sink, lay to Trough axis for 670 km and empties out onto Geosphere; April 2011; v. 7; no. 2; p. 305–312; doi:10.1130/GES00621.1; 4 fi gures. For permission to copy, contact [email protected] 305 © 2011 Geological Society of America Downloaded from http://pubs.geoscienceworld.org/gsa/geosphere/article-pdf/7/2/305/3714555/305.pdf by guest on 26 September 2021 Marsaglia et al. increased uplift (Walcott, 1998). Tectonic uplift 35°S (topography), glacial development, eustatic change, and enhanced sediment supply were Australian likely linked (Carter and Carter, 1996; Carter, Taupo Plate North R.M., et al., 2004). Maximum sedimentation rates Volcanic Island on the margin and in the trough were attained Zone in late Pliocene to Pleistocene glacial periods with intervening interglacials characterized 40° by pelagic deposition in the trough as it was Transform Alpine Fault Pacific bypassed by establishment of high-stand, along- South Plate Island shelf sediment transport regimes (Carter et al., 1990). Furthermore, as outlined in Carter, L., et al. 500 km (2004), fan sedimentation was variably affected by the Pacifi c Deep Western Boundary Current Site 1119 Chatham Rise Chatham Is (DWBC), part of the global thermohaline cir- 45° 4000 m culation, and the mainly wind-driven Antarctic Site 594 Circumpolar Current (ACC), which initiated in Southern Alps Bounty Trough the region during the early Oligocene (Fig. 1). Here we focus on results of drilling of the Bounty Channel Site 1122 1000 m Bounty Channel at Ocean Drilling Program Bounty Fan Site 1122 (Carter et al., 1999) where a 617.8 m succession of lower Miocene to upper Pleisto- Solander Trough cene turbidites, pelagic to hemipelagic sedi- Site 1120 1000 m ments and contour current-modifi ed deposits 50° Site 1121 were recovered from the channel levee (Figs. 2 Solander Channel and 3). Sandy laminae and beds represent over- Campbell Plateau S.W. Pacific bank deposits from turbidity currents that tra- Campbell “Skin” Drift Basin versed and overspilled the Bounty Channel in the process, building up the channel levees (see discussion of processes in Carter et al., 1999). 1000 m 1000 The Miocene section extends from 617.8 to DSDP Site 490 meters below sea fl oor (mbsf), ranges in ODP Site age from ~16 to 11 Ma, and accumulated at 55° Terrigenous supply via turbidity current an average rate of ~20 m/m.y. It is unconform- ably overlain at ~490 mbsf by lower Pliocene N DWBC + NZ sediments ~3.5 Ma in age (Fig. 3). Sediment Sediment accumulation was apparently continuous from the late Pliocene into the Pleistocene with accu- 165°E 170° 175° DWBC + ACC mulation rates reaching ~400 m/m.y. Carter et al. (1999) attributed this sedimentation pat- Figure 1. Location map with details of New Zealand plate boundaries (insert), surround- tern to uplift of the Southern Alps, but they ing bathymetry, Bounty system elements and currents mentioned in the text, and drill sites did not address the cause of the major hiatus (modifi ed from Carter et al., 1999). Abbreviations: ACC—Antarctic Circumpolar Current; and/or unconformity at 490 mbsf. Rather than DSDP—Deep Sea Drilling Project; DWBC—Deep Western Boundary Current; NZ—New an angular unconformity, the hiatus at Site 1122 Zealand; ODP—Ocean Drilling Program; S.W.—Southwest. is more accurately described as a para con- formity unrelated to plate boundary deforma- tion (Carter et al., 1999).