Reconnaissance of Bulk Sediment Composition and Clay Mineral Assemblages: Inputs to the Hikurangi Subduction System

Wallace, L.M., Saffer, D.M., Barnes, P.M., Pecher, I.A., Petronotis, K.E., LeVay, L.J., and the Expedition 372/375 Scientists Proceedings of the International Ocean Discovery Program Volume 372B/375 publications.iodp.org

Contents https://doi.org/10.14379/iodp.proc.372B375.203.2020 1 Abstract 1 Introduction Data report: reconnaissance of bulk sediment 2 Methods composition and clay mineral assemblages: 5 Results 15 Conclusions 1 inputs to the Hikurangi subduction system 16 Acknowledgments 16 References Michael B. Underwood2

Keywords: International Ocean Discovery Program, IODP, JOIDES Resolution, Expedition 372, Expedition 375, Hikurangi Subduction Margin Coring, Logging, and Observatories, Hikurangi margin, clay mineral assemblage, bulk sediment

Abstract derstand the behavior and spatial distribution of slow slip events (SSE) along the plate interface (Saffer et al., 2017). Drilling focused This report provides a reconnaissance-scale assessment of bulk on recovery of sediments, rocks, and pore fluids, acquisition of log- mineralogy and clay mineral assemblages in sediments and sedi- ging-while-drilling data, and installation of long-term borehole ob- mentary rocks that are entering the Hikurangi subduction zone, off- servatories. Interpretations of new compositional results from the shore North Island, New Zealand. Samples were obtained from transect area are challenging, however, because comparable infor- three sites drilled during Leg 181 of the Ocean Drilling Program mation is almost nonexistent from other sectors along the strike- (Sites 1123, 1124, and 1125) and 38 piston/gravity cores that are dis- length of the margin. The closest Ocean Drilling Program (ODP) tributed across the strike-length of the margin. Results from bulk- sites (1123, 1124, and 1125) are located far seaward of the Hikurangi powder X-ray diffraction show large variations in normalized abun- Trough (Figure F1). Shipboard X-ray diffraction (XRD) measure- dances of total clay minerals and calcite. The typical lithologies ments were not completed during that expedition, and only one range from clay-rich hemipelagic mud (i.e., mixtures of terrigenous published report contains postcruise compositional data (Winkler silt and clay with lesser amounts of biogenic carbonate) to calcare- and Dullo, 2002). Far to the southwest, XRD data from the Canter- ous mud, muddy calcareous ooze, and nearly pure nannofossil ooze. bury Basin and Canterbury slope (Land et al., 2010; Villaseñor et al., Basement highs (Chatham Rise and Hikurangi Plateau) are domi- 2015) are of limited value to Hikurangi studies because those sites nated by biocalcareous sediment, whereas most deposits in the capture a different system of detrital sources and dispersal routes off trench (Hikurangi Trough and Hikurangi Channel) and on the insu- the South Island of New Zealand (Figure F1). lar trench slope are hemipelagic. Clay mineral assemblages (<2 μm) The motivation for regional-scale reconnaissance of sediment change markedly as a function of geographic position. Sediment en- composition is to provide better context for forthcoming interpreta- tering the southwest side of the Hikurangi subduction system is en- tions of detrital provenance, sediment dispersal, and temporal evo- riched in detrital illite (>60 wt%) relative to chlorite, kaolinite, and lution of sedimentary systems. Quantitative compositional data are smectite. Normalized proportions of detrital smectite increase sig- also important for several ancillary reasons. The geologic hosts for nificantly toward the northeast to reach values of 40–55 wt% off- slow slip events near the Hikurangi IODP transect likely include shore Hawkes Bay and across the transect area for Expeditions 372 lithified and variably altered volcaniclastic sediments of Late Creta- and 375 of the International Ocean Discovery Program. ceous age, but incorporation of other rock types in the fault zone (e.g., siliciclastic mudstone, altered basalt, marl, and nannofossil Introduction chalk) is also possible (Davy et al., 2008; Barnes et al., 2010; see the Expedition 372B/375 summary chapter [Saffer et al., 2019]). If Expeditions 372 and 375 of the International Ocean Discovery chalk and marl are volumetrically significant at the depths where Program (IODP) drilled five sites on the overriding and subducting slow slip occurs, then the subducting carbonates might modulate plates of the Hikurangi convergent margin, offshore North Island, fault-slip behavior by crystal plasticity (Kennedy and White, 2001) New Zealand (Figure F1). The project’s overarching goal is to un- or diffusive mass transfer (Rutter, 1976). The purity of the

1 Underwood, M.B., 2020. Data report: reconnaissance of bulk sediment composition and clay mineral assemblages: inputs to the Hikurangi subduction system. In Wallace, L.M., Saffer, D.M., Barnes, P.M., Pecher, I.A., Petronotis, K.E., LeVay, L.J., and the Expedition 372/375 Scientists, Hikurangi Subduction Margin Coring, Logging, and Observatories. Proceedings of the International Ocean Discovery Program, 372B/375: College Station, TX (International Ocean Discovery Program). https://doi.org/10.14379/iodp.proc.372B375.203.2020 2 Department of Earth & Environmental Science, New Mexico Institute of Mining & Technology, Socorro NM 87801, USA. [email protected] MS 372B375-203: Received 26 August 2019 · Accepted 26 November 2019 · Published XX Month 2020 This work is distributed under the Creative Commons Attribution 4.0 International (CC BY 4.0) license. M.B. Underwood Data report: reconnaissance of bulk sediment composition and clay mineral assemblages

Figure F1. Index map of the offshore eastern New Zealand region with major bodies of sediment accumulation and likely pathways of sediment dispersal. Ocean Drilling Program (ODP) sites were drilled during Leg 181. International Ocean Discovery Program (IODP) sites were drilled during Expeditions 372 and 375. CB = Canterbury Basin, CS = Cook Strait, RDA = Ruatoria debris avalanche.

35° o o o o o o S North Island Hikurangi 500 km Terrigenous supply fan-drift via turbidity currents N Deep Western RDA Hikurangi IODP Plateau Boundary Current l ODP Site 1124 40° Taupo volcanic zone

CS Channel Hikurangi 1000100 0mm ODP Site Chatham Rise ODP Site 1123 South CB 1125 45° Island 40004000m m

Bounty Channel ODP Site Sediment drift 1122 Bounty Fan Submarine fan Fan-drift

170° 175°E 180° 175°W 170° marl/chalk is a critical variable, however, as is the extent of replace- yses of standard mineral mixtures (Fisher and Underwood, 1995; ment of primary volcaniclastic constituents by expandable clay Underwood et al., 2003). Data from the standards were used to cal- minerals (smectite group). How much clay is present in these litho- culate a matrix of normalization factors with singular value decom- logies, and which clay minerals are dominant? How variable are the position (SVD), as well as a suite of regression equations that relate lithologies along the strike-length of the margin? This report pro- values of integrated peak area to mineral abundance (weight per- vides some preliminary compositional information to help answer cent). Because of differences in XRD hardware, tube fatigue, and those important questions. software, each individual instrument requires calibration and com- To build an archive of relevant compositional data, samples were putation of its own set of normalization factors and/or regression acquired for XRD analyses from ODP Sites 1123, 1124, and 1125 equations. It is also important to blend the “correct” mineral mix- (Figure F1) plus a representative distribution of piston/gravity cores tures using individual standards that match as close as possible to along the strike-length of the Hikurangi margin. Prominent bathy- the natural mineral assemblages of a particular study area. The metric features targeted by the sampling include (1) the Bounty “wrong” blend of clay minerals, for example, or the “wrong” crystal- Channel, which heads off the southeast coast of South Island and linity of calcite will exacerbate errors in their calculated values of directs gravity flows toward the southeast (Lawver and Davey, weight percent. Underwood et al. (in press) provided details re- 2005); (2) submarine canyons emanating from the Cook Strait sec- garding the standard mineral mixtures (both bulk powder and clay tor between South Island and North Island (Mountjoy et al., 2009); size), along with intralaboratory and interlaboratory tests of preci- (3) the Hikurangi Channel, which funnels gravity flows down the sion and comparisons of accuracy. The results reported herein were axis of Hikurangi Trough (toward the north-northeast) before used to inform choices for the Hikurangi-specific standards. bending sharply to the east (Lewis and Pantin, 2002); (4) the Ruato- ria debris avalanche, which remobilized accreted trench sediments Methods and slope deposits along the northernmost Hikurangi margin (Col- lot et al., 2001); and (5) two prominent basement highs on the sub- Samples ducting plate, Chatham Rise and the Hikurangi Plateau (Wood and A total of 61 specimens from Sites 1123, 1124, and 1125 were Davy, 1994; Davy et al., 2008). In addition, the array of sampling acquired from the Gulf Coast Repository in College Station, TX sites encompasses the region’s most influential ocean current, the (USA). The lithologies range from hemipelagic mud (defined here Pacific Deep Western Boundary Current (DWBC) (Shipboard Sci- as silty clay to clayey silt, or lithified equivalent, with subordinate entific Party, 1999a; McCave et al., 2004). biogenic carbonate) to marl (defined here as muddy calcareous ooze Another reason for reconnaissance-scale sampling was to cali- to calcareous mud or lithified equivalents) and chalk (>75% carbon- brate shipboard and shore-based XRD computations. The method ate). Sample spacing for those specimens was designed to cover a used during IODP Expeditions 372 and 375 (see the Expedition representative spread of burial depths and ages for each site. A total 372B/375 methods chapter [Wallace et al., 2019]) depends on anal- of 91 specimens from 38 piston and gravity cores were acquired

IODP Proceedings 2 Volume 372B/375 M.B. Underwood Data report: reconnaissance of bulk sediment composition and clay mineral assemblages from repositories at Lamont-Doherty Earth Observatory (multiple for 2.5–3.0 min. Those specimens were analyzed at the New Mexico cruises on the R/V Vema and the R/V Conrad), Oregon State Uni- Bureau of Geology and Mineral Resources as back-loaded random versity (Cruise RR0503 on the R/V Roger Revelle), and the New Zea- powders using a Panalytical X’Pert Pro diffractometer with Cu an- land National Institute of Water and Atmospheric Research ode. Continuous scans were run at generator settings of 45 kV and (NIWA). The NIWA collection comprises material from multiple 40 mA over an angular range of 5°–70°2θ. The scan step time was research vessels and cruises, including giant piston cores collected 5.08 s, the step size was 0.008°2θ, and the sample holder was spin- by the R/V Marion Dufresne. Table T1 provides the geographic in- ning. Slits were fixed at 0.25 mm (divergence) and 0.1 mm (receiv- formation for each coring station. The lithologic name assigned to ing), and the specimen length was 10 mm. Raw data files were each sample (e.g., lutite, clay-bearing nannofossil ooze, and silty clay) processed using MacDiff software (version 4.2.5) to establish a base- was taken from the original shipboard core descriptions (e.g., Ship- line of intensity, smooth counts, and correct peak positions (relative board Scientific Party, 1999c) without regard to potential inconsisten- to quartz) and to calculate peak intensities and peak areas. Figure cies in terminology or classification scheme. Shipboard descriptions F2 shows representative diffractograms with identification of the of the piston/gravity cores were downloaded from the National Oce- diagnostic peaks for total clay minerals, quartz, feldspar, and calcite. anic and Atmospheric Administration (NOAA) Index to Marine and Values of integrated peak area were used to compute relative Lacustrine Geological Samples (https://www.ngdc.noaa.gov/geo- weight percent for total clay minerals, quartz, feldspar, and calcite samples). Specific sample intervals in those cores cover a represen- following two approaches: (1) a set of polynomial regression equa- tative spread of lithologies, which is indicated by the shipboard tions that relate weight percent to peak area in standard mineral descriptions of color, carbonate content, texture, and clay content. mixtures and (2) a matrix of SVD normalization factors also cali- The NIWA cores and specific sample intervals in those cores were brated from analyses of standard mineral mixtures (Table T2). If a chosen by NIWA personnel (Lisa Northcote and Philip Barnes). natural sample comes close to matching the compositional charac- ter of the standards, then the sum of the values of relative weight Bulk-powder XRD percent will be close to 100%. Sums greater than 100% usually mean The specimens of bulk sediment were freeze-dried, and splits mismatches of mineral crystallinity. Sums significantly less than were crushed to a fine powder using a mechanical mortar and pestle 100% are usually caused by an abundance of solids (amorphous

Table T1. Location of sample sites and lithology of samples used in the com- Table T2. Singular value decomposition (SVD) normalization factors and positional reconnaissance. Lithology terms were taken from original ship- regression equations used for computations of wt% in bulk-powder and board core descriptions. Download table in CSV format. clay-size mineral mixtures. Download table in CSV format.

Figure F2. Representative X-ray diffractograms for random bulk-powder specimens. Diagnostic peaks for computation of weight percent are indicated for total clay minerals (Cl), quartz (Q), feldspar (F), and calcite (Cc).

1124C-20X-4, 10-12 cm Cc 1124C-46X-1, 58-60 cm 1200 Q 3500 Cc

3000 1000 2500 800 2000 600 1500 F

Intensity (counts) Cl 400 1000

200 500 Cl Q

10 15 20 25 30 10 15 20 25 30

1800 RC09-105, 51-53 cm Q RR0503-31JC-2, 110-111 cm Q 2600 1600

2200 1400 1200 1800 1000 1400 800

1000 600 F

Intensity (counts) F Cc 600 400 Cl Cc Cl 200 200

10 15 20 25 30 10 15 20 25 30 Angle (°2θ) Angle (°2θ)

IODP Proceedings 3 Volume 372B/375 M.B. Underwood Data report: reconnaissance of bulk sediment composition and clay mineral assemblages and/or crystalline) not included in the standard mix (e.g., volcanic Figure F3. Representative X-ray diffractograms for oriented clay-size speci- glass, zeolites). All of the relative abundance values were normalized mens. Diagnostic peaks for computation of weight percent are indicated for to total clay minerals + quartz + feldspar + calcite = 100%. The same smectite (001), illite (001), undifferentiated chlorite (002) + kaolinite (001), analytical and computational approach was used for shipboard data and quartz (100). Subsidiary peaks for individual clay minerals, quartz, and illite/smectite mixed-layer clays are also shown. The saddle:peak intensity acquisition during Expeditions 372 and 375 (see the Expedition ratio for smectite (001) was used to determine percent expandability. 372B/375 methods chapter [Wallace et al., 2019]). Underwood et al. (in press) provide a thorough assessment of interlaboratory preci- Peak sion between the R/V JOIDES Resolution and New Mexico Tech. Er- MD06-3003, 446–447 cm 6000 rors of accuracy for the standard mineral mixtures are smaller using Smectite (001) the regression equations, as opposed to SVD normalization factors. 5000 The average errors (computed weight percent − true weight percent) are total clay minerals = 1.7%, quartz = 1.2%, feldspar = 1.6%, and 4000 calcite = 1.2% (Underwood et al., in press).

3000 Clay-size XRD Saddle Quartz (101)

Intensity (counts) Illite (001) The clay-sized fraction (<2 μm) was isolated from representative 2000 Chlorite (002) + bulk samples of hemipelagic mud and mudstone. Carbonate-rich kaolinite (001) Chlorite (004) + kaolinite (002) specimens (chalk, marl, etc.) were excluded from the clay-mineral 1000 I/S reconnaissance because they would have required time-consuming I/S acid digestion steps. Splits of the freeze-dried bulk sediment were transferred to 600 mL beakers, treated with 2% hydrogen peroxide 510152025 to remove organic matter, and suspended in ~250 mL of sodium hexametaphosphate solution (4 g/1000 mL of distilled H2O). Bea- RR0503-01-1, 50–51 cm kers with suspended clay were inserted into an ultrasonic bath for 3000 Chlorite (002) + kaolinite (001) several minutes to promote dispersion and retard flocculation. Sus- Illite (001) pensions were washed of solutes by two passes through a centrifuge Quartz (101) (8200 rpm for 25 min; ~6000× g) with resuspension in distilled-de- ionized water after each pass. The suspended particles were then 2000 Chlorite (004) + kaolinite (002) transferred to 125 mL plastic bottles and resuspended by vigorous Chlorite shaking plus insertion of an ultrasonic cell probe for ~2 min. Clay- (001) size splits of each suspension (<2 μm equivalent spherical diameter) Smectite Intensity (counts) 1000 (001) Illite Chlorite were separated by centrifugation (1000 rpm for 2.4 min; ~320× g). (002) (003) Preparation of oriented clay aggregates for the XRD scans followed Quartz the filter-peel method (Moore and Reynolds, 1989b) using 0.45 μm (100) filter membranes and glass discs. Discs were placed in a closed va- por chamber at room temperature for at least 24 h to saturate the 5 10 15 20 25 clay aggregates with ethylene glycol. This last step expands the in- Angle (°2θ) terlayer of smectite to minimize overlap between the smectite (001) and chlorite (001) reflections (Figure F3). where smectite + illite + undifferentiated (chlorite + kaolinite) + The oriented glycol-saturated clay-size specimens were ana- quartz = 100% (Table T2). To permit comparisons among the three lyzed at the New Mexico Bureau of Geology and Mineral Resources computational approaches, the weight percent values were also nor- using the same Panalytical X’Pert Pro diffractometer. Those scans malized to a clay-only assemblage of smectite + illite + undifferenti- were run at generator settings of 45 kV and 40 mA over an angular ated (chlorite + kaolinite) = 100%. As described more fully by range of 2°–28.0°2θ and using a scan step time of 1.6 s, a step size of Underwood et al. (in press), errors of accuracy for the standard 0.01°2θ, and a stationary sample holder. Slits were fixed at 0.5 mm mineral mixtures are largest using the Biscaye (1965) weighting fac- (divergence) and 0.1 mm (receiving), and the specimen length was tors (as high as 18.6%), but those values are tabulated here to permit 10 mm. Raw data files were processed using MacDiff software (ver- direct comparisons with data from previous studies (e.g., Winkler sion 4.2.5) to establish a baseline of intensity, smooth counts, cor- and Dullo, 2002). The average errors using the regression equations rect peak positions (relative to quartz), and calculate peak are illite = 3.0%, undifferentiated (chlorite + kaolinite) = 5.1%, and intensities and peak areas. Representative diffractograms are shown smectite = 3.9% (Underwood et al., in press). in Figure F3 with identification of the diagnostic peaks for smectite, Methods for routine assessment of clay diagenesis include the illite, undifferentiated chlorite + kaolinite, and quartz. saddle:peak method to compute “expandability” of smectite and/or Values of integrated peak area were used to compute relative illite/smectite (I/S) mixed-layer clay (Rettke, 1981). The angular po- and normalized abundance values for each of the common clay- sition of the composite I/S 002/003 peak (°2θ) was used to compute sized minerals following three approaches: (1) Biscaye (1965) peak- the percentage of illite layers in the mixed-layer clay (Moore and area weighting factors, which are equal to 1× smectite, 4× illite, and Reynolds, 1989a). This computation is possible only when the I/S 2× undifferentiated chlorite + kaolinite; (2) a set of regression equa- peak intensity is high enough to resolve a clear apex. The peak tions where smectite + illite + undifferentiated (chlorite + kaolinite) width at half maximum for the illite 001 peak (Δ°2θ) is used as a + quartz = 100%; and (3) a matrix of SVD normalization factors, measure of illite crystallinity (Warr and Mählmann, 2015).

IODP Proceedings 4 Volume 372B/375 M.B. Underwood Data report: reconnaissance of bulk sediment composition and clay mineral assemblages

Results Table T3. Results of bulk-powder X-ray diffraction and computations of mineral abundance. See Table T1 for sample locations and lithologies. Down- Bulk-powder XRD load table in CSV format. To illustrate spatial changes in the bulk-powder XRD results (Table T3), the data are grouped by geographic sector; all of the val- dances are 34.8–85.5 wt% (average = 69.3 wt%). Contents of total ues on such plots are normalized abundances computed using the clay minerals range 6.5–42.0 wt% (average = 17.5 wt%), and the pro- regression equations (Table T2). Figure F4 shows the sector off- portions of both quartz and feldspar remain consistently <12 wt%. shore South Island, New Zealand. This sector includes the transect Site 1125 is located on the north flank of Chatham Rise at a wa- area for IODP Expedition 317 (Canterbury Basin), ODP Site 1119, ter depth of 1360 m (Figure F5). This site lies beneath a zone of high Deep Sea Drilling Project (DSDP) Site 594, and distal reaches of the primary productivity (the Subtropical Convergence), but sedimen- Bounty Channel. Samples from Cores VM16-122 and RR0503-06 tation is also modulated by two surface currents, the East Cape Cur- display the greatest amount of compositional variability with calcite rent, which carries suspended terrigenous sediment from eastern contents of 0.9 to 86.7 wt% and total clay contents of 2.2–38.8 wt%. North Island, and the Southland Current, which flows up the east Judging from those compositional ranges, the cores appear to con- coast of South Island before turning east to parallel the crest of Cha- tain both biocalcareous ooze and hemipelagic mud from Bounty tham Rise (Shipboard Scientific Party, 1999d). The cores recovered Channel spillover. The remaining samples are typical hemipelagic from Site 1125 comprise a Miocene to Quaternary succession of muds (i.e., mixtures of terrigenous silt and clay plus subordinate clay-rich nannofossil ooze and chalk alternating with layers more biogenic carbonate). Their values of total clay content are 28.0– enriched in terrigenous silt and clay (Shipboard Scientific Party,

39.1 wt%; quartz content is 17.0–38.1 wt%, feldspar content is 20.6– 1999d). Coulometric measurements of CaCO3 were not completed 36.3 wt%, and calcite content is 0.8–32.1 wt%. Those compositions at this site, but XRD analyses of 18 samples (Table T3) show consis- are in general agreement with bulk-powder XRD data from the tently high concentrations of calcite (58.0–86.6 wt%; average = Canterbury Basin (Villaseñor et al., 2015), although quantitative 73.9 wt%). Normalized proportions of total clay minerals range 4.6– comparisons should be made with caution because of differences in 19.9 wt% (average = 11.0 wt%), whereas the contents of both quartz methodology. and feldspar are consistently <11 wt%. The contributions of terri- Samples analyzed from the Chatham Rise sector (Figure F5) in- genous silt and clay are slightly higher in the lower 170 m of the sec- clude those from nine piston/gravity cores and two ODP sites. The tion (Figure F7). one specimen from Core RC09-111, located in the distal northeast The Hikurangi Channel (Figure F8) is the primary conduit for corner of the sector, is nearly devoid of calcite and contains turbidity currents and related gravity flows entering Hikurangi 58.1 wt% total clay. Water depth at that coring station is 4777 m be- Trough from the southwest (Lewis et al., 1998; Lewis and Pantin, low sea level, so the provisional interpretation is depletion of car- 2002). The channel extends >2000 km from feeder canyons that bonate due to deposition (and dissolution) below the calcite head in the Cook Strait and along the southeast coast of South Is- compensation depth (CCD). Core samples from shallower water land (Lewis, 1994; Mountjoy et al., 2009). Six hemipelagic mud sam- depths along the crest and northern flank of Chatham Rise are con- ples were analyzed from four cores in the channel-levee complex sistently enriched in calcite, with normalized percentages of 34.3– (Figure F8). The mud specimens contain 33.4–43.7 wt% total clay 88.7 wt%. The total clay content is 5.5–34.7 wt%. Normalized per- minerals, 20.4–31.0 wt% quartz, 20.6–28.7 wt% feldspar, and 6.6– centages of quartz range 3.1–16.5 wt%, and values for feldspar are 14.8 wt% calcite (Table T3). These bulk compositions are similar to 2.6–14.5 wt%. These compositions are consistent with a continuum the values documented in Cores VM16-123 and RC08-76 offshore of mixing between biogenic carbonate ooze and subordinate silici- southeast South Island (Figure F4). clastic silt + clay (i.e., calcareous mud to nearly pure nannofossil The Hawkes Bay sector offshore North Island lies farther to the ooze). Cores from the southern flank of Chatham Rise (RR0503-10, northeast along the subduction margin (Figure F9). A total of 10 RR0503-11, and RC09-108) are more variable in composition, with samples were analyzed from giant piston Core MD2121, on the calcite contents of 4.1–83.7 wt% and total clay contents of 4.8–39.9 landward trench slope, to test for compositional variability within wt%. The occurrences of mud with low percent calcite values are the Holocene and latest Pleistocene. Normalized concentrations of consistent with spillover from the distal reaches of Bounty Channel, total clay minerals in that core range from 35.2 to 41.1 wt%. The which meanders across the southern edge of the sector (Figure F5). content of quartz is 23.6–28.2 wt%, and feldspar varies between 20.1 Site 1123 was drilled on the northeastern flank of Chatham Rise and 23.3 wt%. Values for calcite range from 12.3 to 19.1 wt%. Nearby at a water depth of 3290 m (Figure F5). The main purpose for drill- Cores RR0503-52 and RR0503-56 yielded similar bulk compositions ing there was to document the long-term effects of the DWBC on (Table T3). One sample from Core MD06-2997, on the outer conti- sedimentation (Shipboard Scientific Party, 1999b). Coring extended nental shelf, contains slightly more quartz (30.1 wt%) balanced by a to a total depth of 632.8 meters below seafloor (mbsf), and the strata reduction of calcite (8.0 wt%). Two samples from Core VM18-231, range in age from late Eocene to Quaternary (Shipboard Scientific recovered from the seaward levee of Hikurangi Channel, contain Party, 1999b). The lithologies include clay-rich nannofossil ooze, 42.1–42.4 wt% total clay, 23.5–27.5 wt% quartz, 19.5–23.7 wt% feld- nannofossil chalk, nannofossil-rich mudstone, and micrite (Figure spar, and 6.7–14.6 wt% calcite (Figure F9), which is similar to sam- F6). Beds are typically 1–1.5 m thick and distinguished by color ples from the upstream reaches of the Hikurangi Trough (Figure variations (greenish gray to white) caused by differing proportions F8). of biogenic carbonate and terrigenous clay. Values of CaCO3 (from The IODP transect region (Figure F10) includes the five sites shipboard coulometric measurements) are highly scattered drilled during Expeditions 372 and 375 (see the Expedition throughout the section and range 10%–84% (Shipboard Scientific 372B/375 summary chapter [Saffer et al., 2019]), the Ruatoria de- Party, 1999b). XRD analyses of 20 samples (Table T3) confirm the bris avalanche, and a transverse submarine canyon in the Poverty compositional variability (Figure F6); normalized calcite abun- reentrant. Three giant piston cores from this sector (MD06-3003,

IODP Proceedings 5 Volume 372B/375 M.B. Underwood Data report: reconnaissance of bulk sediment composition and clay mineral assemblages

Figure F4. South Island sector of the reconnaissance study area with positions of sample sites and normalized proportions of dominant minerals in random bulk-powder specimens (computed using regression equations). Deep Sea Drilling Project (DSDP) Site 594 was cored during Leg 90. Ocean Drilling Program (ODP) Site 1119 was cored during Leg 181 (Shipboard Scientific Party, 1999b). The transect across Canterbury Basin was cored during Integrated Ocean Drilling Program Expedition 317. Geographic information for the piston and gravity cores is listed in Table T1. X-ray diffraction results are tabulated in Table T3.

41° S 100 km

N 42° Hikurangi Channel VM16-123

43° RC08-76

Chatham Rise 44° ODP Site 1119 IODP 317 45° South Island Bounty Channel RR0503-06 Bounty Channel DSDP 46° Site 594 RR0503-01 VM16-122

47° South Island sector

168° 170° 172° 174° 176° 178°E 180° 178°W

Calcite Quartz South Island sector Bulk powder mineralogy Feldspar Total clay minerals 100

40 Normalized abundance (wt%) 20

RC08-76 (29 cm) VM16-122 (36 cm) RC08-76 (154 cm) VM16-122 (104VM16-122 cm) (363VM16-122 cm) (809VM16-123 cm) (103 cm)

RR0503-06JC-1RR0503-06JC-1 (20 cm) (60 cm) RR0503-01JC-1 (50-51) RR0503-06JC-6 (750 cm)RR0503-01JC-4RR0503-01JC-4 (450-451) (530-531)

MD06-3008, and MD06-3009) were described and interpreted in 39.1 wt% quartz, 19.1–33.9 wt% feldspar, and 4.1–14.7 wt% calcite detail by Pouderoux et al. (2012). With one exception (Site U1751; (Table T3). Samples from the Ruatoria debris avalanche and vicinity 52.3 wt% calcite), the bulk compositions from these cores mirror reveal no significant differences in bulk composition compared to those of sediments in the Hawkes Bay sector to the southwest (Fig- undeformed slope sediments to the southwest (Figure F10). Core ure F9). Normalized abundance is 20.6–43.1 wt% total clay, 23.1– MD06-3004, on the continental shelf, contains less total clay (20.6–

IODP Proceedings 6 Volume 372B/375 M.B. Underwood Data report: reconnaissance of bulk sediment composition and clay mineral assemblages

Figure F5. Chatham Rise sector of the reconnaissance study area with positions of sample sites and normalized proportions of dominant minerals in random bulk-powder specimens (computed using regression equations). Geographic information for Ocean Drilling Program (ODP) Sites 1123 and 1125 and the piston-gravity cores is listed in Table T1. X-ray diffraction results are tabulated in Table T3.

40° S Chatham Rise sector RC09-111

41°

RR0503-29 ODP Site 1123 Hikurangi Channel 42° RR0503-28 RR0503-19

43° ODP Site 1125 RC09-110

Chatham Rise 44°

RR0503-11 RC08-78 RR0503-10 45° N Bounty Channel 46° RC09-108 100 km

178°E 180° 178°W 176° 174° 172° 170° 168°

Calcite Quartz Chatham Rise sector Bulk-powder mineralogy Feldspar Total clay minerals 100

40 Normalized abundance (wt%) 20

0 ) cm) 36 cm) (70 cm) 2 (131 JC-1 (51 cm) 29JC-2 RC08-78 (54 cm) RC09-108RC09-108 (53 cm) (77 cm) RC08-78RC08-78 (355 cm) (903 cm) 3-28JC-1 (40 cm) RC09-110RC09-110 (208 cm) (6 RC09-111 (615 cm) RC09-108 (1164 cm) 0503-19JC-6R050 (7200503-28JC- cm) RR0503-10JC-1 RR0503-11JC-1(40 cm) (40 cm) RR0503-19 R RR0503- RR0503-10JC-3RR0503-11JC-3 (340 cm) (365 cm) RR0503-19JC-2RR (181 cm RR RR0503-28JC-7 RR0503-29JC-8(900 cm) (980 cm)

24.2 wt%) and higher proportions of quartz (37.8–39.1 wt%) and Hikurangi Plateau is the dominant bathymetric feature seaward feldspar (31.9–33.9 wt%) (Table T3). It’s reasonable to surmise that of the IODP transect sector (Figure F11). The Hikurangi Channel relatively small contrasts in composition compared to nearby slope meanders toward the east across the plateau before bending north and trench-floor deposits are probably related to the grain size dis- in the vicinity of Site 1124 (Lewis, 1994; Davy et al., 2008). Six cores tribution because quartz and feldspar are expected to increase in were sampled from along the southern flank of the plateau. With the silt and fine sand fractions. two clay-rich exceptions (Cores RR0503-31 and RR0503-48), these

IODP Proceedings 7 Volume 372B/375 M.B. Underwood Data report: reconnaissance of bulk sediment composition and clay mineral assemblages

Figure F6. Generalized stratigraphic column for Ocean Drilling Program Site 1123 (modified from Shipboard Scientific Party, 1999c) with normalized values of major minerals in random bulk-powder specimens computed using regression equations and singular value decomposition (SVD) normalization factors (Table T2). X-ray diffraction results are tabulated in Table T3.

Site 1123 Normalized abundance in bulk sediment (wt%) Graphic Total clay minerals Quartz Feldspar Calcite Age lithology 0204002040 20 40 20 40 60 80 Tephra

Quaternary Clayey nannofossil ooze, nannofossil ooze, 100 tephra Regression SVD

Clayey nannofossil 200 chalk, nannofossil chalk, tephra

300 late Miocene Pliocene

Nannofossil chalk Depth (mbsf)

400

middle Miocene Nannofossil mudstone, chalk 500

Mass transport deposit

Clay-bearing chalk early Miocene

600 Oligo. Micrite (limestone) Eocene sediments cover the spectrum from calcareous mud to muddy cal- rocks as old as Late Cretaceous (Figure F12). The common litholo- careous ooze. Contents of total clay minerals range from 15.0 to gies include clay-bearing nannofossil ooze, nannofossil-bearing 40.2 wt%, and the proportion of calcite ranges from 25.4 to 67.1 mud, chalk, mudstone, zeolitic mudstone, and chert. Coulometric wt%. Contents of quartz and feldspar are <20 wt%. One core from measurements revealed large variations in the abundance of CaCO3; the southernmost Kermadec Trench was also sampled (Figure F11). values range 1.5–88.3 wt% with considerable scatter throughout the Mud from that core contains 37.9–40.8 wt% clay minerals, 24.4– section (Shipboard Scientific Party, 1999c). Bulk XRD data from 23 29.4 wt% quartz, 21.7–26.1 wt% feldspar, and 6.7–13.0 wt% calcite. samples are generally consistent with the heterogeneous nature of Site 1124 is located on a north-south–trending ridge of drift core descriptions (Figure F12). The normalized abundance of total sediment at a water depth of 3978 m (Shipboard Scientific Party, clay minerals ranges 5.8–60.7 wt%, and the abundance of calcite 1999c). The main goal of drilling at Site 1124 was to obtain a record varies between 3.0 and 91.3 wt% (Table T3). Quartz values range of Miocene sedimentation under the influence of the DWBC. In ad- 1.5–17.9 wt%, and feldspar content ranges 1.4–19.6 wt%. In general, dition, a sequence of Pleistocene turbidites laps onto the drift sedi- the content of total clay increases downsection from the seafloor to ments from the west, having spilled over the right bank of ~300 mbsf, with a corresponding decrease in calcite (Figure F12). Hikurangi Channel (Shipboard Scientific Party, 1999c). Coring Conversely, the lower 125 m of the section is generally more en- reached a total depth of 473 mbsf with recovery of sedimentary riched in calcite.

IODP Proceedings 8 Volume 372B/375 M.B. Underwood Data report: reconnaissance of bulk sediment composition and clay mineral assemblages

Figure F7. Generalized stratigraphic column for Ocean Drilling Program Site 1125 (modified from Shipboard Scientific Party, 1999e) with normalized values of major minerals in random bulk-powder specimens computed using regression equations and singular value decomposition (SVD) normalization factors (Table T2). X-ray diffraction results are tabulated in Table T3.

Site 1125 Normalized abundance in bulk powder (wt%) Graphic Total clay Quartz Feldspar Calcite Age lithology Lithology 0204002040020400204060 80

Clayey nannofossil ooze, nannofossil- bearing silty clay

100

Regression SVD factors Nannofossil-bearing silty clay, clay-bearing nannofossil ooze 200

Nannofossil chalk 300 Depth (mbsf)

400 Miocene Pliocene Quat. Clayey nannofossil chalk

500

Clay mineral assemblages Island sector) tends to contain more crystalline illite (i.e., narrower peak) as compared to smectite-rich specimens (broader peak). The A smaller subset of the total suite of bulk sediment specimens range of crystallinity values spans the domain from advanced dia- was used to generate initial results for the clay-sized fraction. This genesis to anchimetamorphism (i.e., incipient greenschist facies). effort concentrated on lithologies with relatively high proportions Given the near-seafloor position of the cored intervals, these results of total clay minerals (Table T4) to reveal possible first-order should be regarded as indicators of geologic conditions in the detri- changes in clay along the strike length of the Hikurangi margin. Fig- tal source areas rather than in situ burial diagenesis. ure F13 shows the geographic distribution of clay-size results plot- Smectite expandability ranges 46%–86% (Table T4). In a generic ted as normalized proportions of clay minerals (i.e., where smectite sense, the lower values (less expandability) are consistent with + illite + undifferentiated [chlorite + kaolinite] = 100%). Proportions higher proportions of detrital I/S mixed-layer clay in the assem- of smectite overall range 5.0–54.2 wt%. Weight percent values for blage, whereas higher values are indicative of more discrete smec- illite range 35.7–67.4 wt%, and the proportion of undifferentiated tite in the assemblage from altered volcanic sources. Percentages of chlorite + kaolinite ranges 9.4–27.8 wt%. The spatial changes, how- illite within the I/S mixed-layer phase range 1.1%–21.8% (Table T4). ever, are noteworthy. The region offshore South Island and continu- Those measurements were possible only for smectite-rich speci- ing into the proximal reaches of Hikurangi Channel is dominated by mens with intensities high enough to resolve the I/S 002/003 peak. detrital illite, with normalized proportions of 61–71 wt% (or 53%– Again, these results should be regarded as indicators of geologic 64% using Biscaye weighting factors; Table T4). Proportions of conditions in the detrital source areas rather than in situ burial dia- smectite begin to increase significantly near 41°S (Core VM18-230), genesis. and smectite remains the dominant clay throughout the Hawkes Comparisons between these reconnaissance results for clay Bay sector and the IODP transect area (Figure F13), with most val- minerals and data from published XRD studies in the region are un- ues >40 wt%. reliable because of differences in methodology. For example, Land The crystallinity index for illite is consistently between 0.42Δ°2θ et al. (2010) analyzed the clay mineral assemblages from ODP Site and 0.59Δ°2θ (Table T4). The illite-rich clay assemblage (e.g., South

IODP Proceedings 9 Volume 372B/375 M.B. Underwood Data report: reconnaissance of bulk sediment composition and clay mineral assemblages

Figure F8. Proximal Hikurangi Channel sector of the reconnaissance study area with positions of sample sites and normalized proportions of dominant minerals in random bulk-powder specimens (computed using regression equations; Table T2). Geographic information for the piston-gravity cores is listed in Table T1. X-ray diffraction results are tabulated in Table T3.

40° Hikurangi Channel sector S North Island prism

etionary VM18-230 41° accr

Cook Hikurangi Strait South Island RC09-105 U657 42° Hikurangi Channel

U660 N

43° Chatham Rise 100 km

173° 174° 175° 176° 177° 178° 179°E 180°E

Hikurangi Channel sector Calcite Quartz Bulk powder mineralogy Feldspar Total clay minerals 100

40 Normalized proportion (wt%) 20

RC09-105 RC09-105 U660 U657 VM18-230 VM18-230 (51-53 cm) (802-803 cm) (0-2 cm) (15-16 cm) (53-54 cm) (244-245 cm)

1119 in the Canterbury Basin (Figure F4), but their computations of tors result in underestimated values for illite, and the values for relative abundance were based on proportions of raw peak-area val- chlorite are overestimated. Bulk-powder data from Villaseñor et al. ues without application of weighting factors. Qualitatively, those re- (2014) also reveal low concentrations of detrital smectite in the sults show that the mineral assemblage in Canterbury Basin is Canterbury Basin sediments relative to illite, muscovite, and chlo- dominated by illite and chlorite with minor to trace amounts of rite. smectite. In terms of qualitative temporal trends, the data from Site Carbonate-rich samples from ODP Site 1123 (Figure F5) were 1119 reveal higher smectite values in the lower Pliocene with con- analyzed by Winkler and Dullo (2002) after treating the specimens sistent decreases upsection into the upper Pliocene and Pleistocene with acetic acid to remove CaCO3. Their computations of relative (Land et al., 2010). Accuracy errors in the reported percentages, abundance utilized Biscaye (1965) weighting factors (Table T2), so however, are probably >25%. Computations without weighting fac- semiquantitative comparisons are possible with the results reported

IODP Proceedings 10 Volume 372B/375 M.B. Underwood Data report: reconnaissance of bulk sediment composition and clay mineral assemblages

Figure F9. Hawkes Bay sector of the reconnaissance study area with positions of sample sites and normalized proportions of dominant minerals in random bulk-powder specimens (computed using regression equations; Table T2). Geographic information for the piston-gravity cores is listed in Table T1. X-ray diffraction results are tabulated in Table T3.

Hawkes Bay sector 39° S Hikurangi Plateau

Poverty Canyon Hawkes Bay

North prism Island Hikurangi Channel MD06-2997

VM18-231 40° RR0503-56 accretionary N

RR0503-52

MD2121 100 km Hikurangi

177° 178° 179°E 180°

Hawkes Bay sector Calcite Quartz Bulk powder mineralogy Feldspar Total clay minerals 100

40 Normalized abundance (wt%)

MD2121 (25 cm) MD2121 (612 cm) VM18-231 (39 cm) MD2121MD2121 (1550MD2121 cm) (1700MD2121 cm)(1790MD2121 cm) (2100MD2121 cm) (2190MD2121 cm) (2500MD2121 cm) (2940 cm) (3480 cm) VM18-231 (134 cm) MD06-2997 (2100 cm) RR0503-52-JC-1 (15 cm) RR0503-56-JC-2 (30 cm) RR0503-52-JC-2RR0503-52-JC-4RR0503-52-JC-6 (185 cm) (480 cm) (720RR0503-56-JC-5 cm) RR0503-56-JC-6 (450 cm) (680 cm) here (Table T4). The data from Site 1123, when plotted versus dep- (1986) documented a similar temporal trend at DSDP Site 594 (Fig- ositional age, show clear trends over time (Winkler and Dullo, ure F5; Shipboard Scientific Party, 1986). In sediments younger 2002). Smectite content decreases from maximum values of ~80% than 6 Ma, the content of illite ranges 41%–57% (Winkler and Dullo, at 33 Ma to ~20%–30% by 1–2 Ma. Conversely, proportions of illite 2002), overlapping the range of values reported here for offshore and chlorite both increase over the same timespan. Robert et al. South Island and proximal Hikurangi Channel (Table T4).

IODP Proceedings 11 Volume 372B/375 M.B. Underwood Data report: reconnaissance of bulk sediment composition and clay mineral assemblages

Figure F10. International Ocean Discovery Program (IODP) transect sector of the reconnaissance study area with positions of sample sites and normalized proportions of dominant minerals in random bulk-powder specimens (computed using regression equations; Table T2). Geographic information for the piston-gravity cores is listed in Table T1. X-ray diffraction results are tabulated in Table T3.

IODP transect sector

TAN0810-3

38° S Ruatoria MD06-3009 debris avalanche

North Island

MD06-3008 Site U1519 x MD06-3004 Site U1518 x Poverty Site U1517 N 39° Site U1526 Canyon x x MD06-3003 Site U1520 Hawkes Bay U1746 100 km U1752 U1751 177° 178° 179°E 180°

Calcite Quartz Hikurangi IODP transect sector Feldspar Total clay minerals Bulk powder mineralogy 100

40 Normalized abundance (wt%)

U1751 (4U1752 cm) (1 cm) U1746 (92 cm) TAN0810-3 (2 cm) TAN0810-3MD06-3009 (62 cm) (1 cm) MD06-3008 (1 cm) MD06-3008 (900 cm)MD06-3004MD06-3004 (147 cm) (313 cm)MD06-3003MD06-3003 (146 cm) (446 cm) MD06-3009MD06-3009 (1035 cm) (1920MD06-3008 cm) (2137 cm) MD06-3003 (1199 cm)

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Figure F11. Hikurangi Plateau sector of the reconnaissance study area with positions of sample sites and normalized proportions of dominant minerals in random bulk-powder specimens (computed using regression equations; Table T2). Geographic information for Ocean Drilling Program (ODP) Site 1124 and the piston-gravity cores is listed in Table T1. X-ray diffraction results are tabulated in Table T3.

Hikurangi Plateau sector VM18-232 37° S Kermadec Trench IODP transect region N Fig. F10

38° 100 km North Island Ruatoria Hikurangi Plateau debris avalanche 39° Hikurangi Channel prism ODP Site 1124 Hawkes Bay RR0503-48 RR0503-41 RR0503-36 RR0503-44 40° accretionary RR0503-47 RR0503-31 177° 178° 179°E 180° 179°W 178° 177° 176°

Hikurangi Plateau sector Calcite Quartz Bulk powder mineralogy Feldspar Total clay minerals 100

40 Normalized proportion (wt%)

VM18-232 (41 cm) VM18-232 (223 cm)

RR0503-47JC-2 (51 cm)RR0503-48JC-2 (50 cm) RR0503-44TC-1 (40 cm) RR0503-47JC-8 (940 cm)RR0503-48JC-4RR0503-41JC-1 (450RR0503-41JC-2 cm) (101 RR0503-41JC-5cm) (131 cm) (635 RR0503-44TC-2cm) RR0503-31JC-2 (110RR0503-31JC-4 cm) (110RR0503-36JC-1 cm) (450 RR0503-36JC-5cm) (101 cm) (660 cm)

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Figure F12. Generalized stratigraphic column for Ocean Drilling Program Site 1124 (modified from Shipboard Scientific Party, 1999d) with normalized values of major minerals in random bulk-powder specimens computed using regression equations and singular value decomposition (SVD) normalization factors (Table T2). X-ray diffraction results are tabulated in Table T3.

Site 1124 Normalized abundance in bulk sediment (wt%)

Graphic Total clay minerals Quartz Feldspar Calcite Age lithology 02040 60 0 20 40 20 40 20 40 60 80

Quat.

Clay-bearing Plio. nannofossil ooze, 100 nannofossil mud, tephra

Regression late SVD Mio.

200

Nannofossil chalk, mid. mudstone Mio. Depth (mbsf)

300 early Mio. Nannofossil chalk, clay-bearing chalk

Chalk 400 Oligo. Mudstone Eocene Chalk, zeolitic Paleoc. mudstone Zeolitic Cret. mudstone, chert

Table T4. Results of clay-size X-ray diffraction and computations of mineral abundance. See Table T1 for sample locations and lithologies. Download table in CSV format.

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Figure F13. Core locations and normalized clay mineral proportions. Normalized proportions (where smectite + illite + undifferentiated chlorite + kaolinite = 100%) are based on computations using regression equations (Table T2). X-ray diffraction results are tabulated in Table T4.

Relative proportion (wt%) IODP transect sector 0 20 40 60 80 100 N 38° MD06-3009, 1035 S MD06-3009 MD06-3009, 0 MD06-3008, 900 North Island MD06-3008 MD06-3008, 0

MD06-3004 MD06-3004, 313 MD06-3003, 446 39° MD06-3003 U1752, 0 U1752 100 km 177° 178° 179°E 180° RR0503-44, 110

Hawkes Bay sector RR0503-44, 40 39° S RR0503-48, 450 N Hawkes RR0503-47, 940 Bay RR0503-47, 51 North Hikurangi Channel VM18-231, 134 Island MD06-2997 VM18-231, 39 VM18-231 40° RR0503-56, 680 RR0503-56 RR0503-52 RR0503-56, 450 RR0503-56, 30 MD2121 100 km RR0503-52, 720 177° 178° 179°E 180° RR0503-52, 480 40° Hikurangi Channel sector S RR0503-52, 185 North N RR0503-52, 15 Island 41° VM18-230 MD2121, 25

Cook VM18-230, 244 Strait South RC09-105 U657 VM18-230, 53 42° Island Hikurangi Channel U657, 15 U660 U660, 0

43° Chatham Rise 100 km RC09-105, 802 RC09-105, 51 173° 174° 175° 176° 177° 178° 179°E 180°

41° South Island sector VM16-123, 103 S RC08-76, 29 N VM16-123 RC08-76, 154 43° 100 km RC08-76 RR0503-01, 530 Chatham Rise sland RR0503-01, 450

45° South I RR0503-01, 50 RR0503-01 VM16-122, 104 Bounty Channel V16-122 Smectite Illite Chlorite + kaolinite 47° 168° 170° 172° 174° 176° 178°E 180° 178°W

Conclusions whereas clay-rich hemipelagic mud typifies the Hikurangi Trough and landward trench slope. Locally, the carbonate-rich and clay- Reconnaissance-scale XRD analysis of bulk sediment reveals rich sediments are interbedded. The clay mineral assemblage large variations in proportions of biogenic calcite and terrigenous changes significantly along the strike length of the margin. Detrital clay minerals across the Hikurangi subduction system. Most speci- illite is the dominant clay mineral from offshore South Island into mens from subducting bathymetric highs (Chatham Rise, Hikurangi the southwest portion of the Hikurangi Trough. Smectite becomes Plateau) are composed of fine-grained biocalcareous sediment (cal- the dominant clay mineral in the trench–forearc domain between careous mud, muddy calcareous ooze, and nannofossil ooze), 41°S latitude and the Kermadec Trench.

IODP Proceedings 15 Volume 372B/375 M.B. Underwood Data report: reconnaissance of bulk sediment composition and clay mineral assemblages

Acknowledgments McCave, I.N., Carter, L., Carter, R.M., and Hayward, B.W., 2004. Cenozoic oceanographic evolution of the SW Pacific gateway: introduction. In This study used samples provided by core repositories at the In- McCave, I.N., Carter, L., Carter, R.M., and Hayward, B.W. (Eds.), Cenozoic ternational Ocean Discovery Program (Ocean Drilling Program Leg Oceanographic Evolution of the Southwest Pacific Gateway, ODP Leg 181. 181), Lamont-Doherty Earth Observatory, Oregon State University Marine Geology, 205(1–4):1–7. https://doi.org/10.1016/S0025-3227(04)00015-5 (supported by NSF grant Number OCE-1558679), and the New Moore, D.M., and Reynolds, R.C., Jr., 1989a. Identification of mixed-layered Zealand National Institute of Water and Atmospheric Research. clay minerals. In Moore, D.M., and Reynolds, R.C., Jr. (Eds.), X-Ray Dif- Funding for XRD analyses was obtained through a grant to Laura fraction and the Identification and Analysis of Clay Minerals: New York Wallace at GNS Science from the New Zealand Ministry for Busi- (Oxford University. Press USA), 241–271. ness, Innovation, and Employment’s Endeavour Research (Contract Moore, D.M., and Reynolds, R.C., Jr., 1989b. Sample preparation techniques C05X1605). Karissa Rosenberger assisted with sample preparation for clay minerals. In Moore, D.M., and Reynolds, R.C., Jr. (Eds.), X-Ray at New Mexico Tech, and Kelsey McNamara assisted with XRD at Diffraction and the Identification and Analysis of Clay Minerals: New the New Mexico Bureau of Geology and Mineral Resources. Kather- York (Oxford University Press USA), 179–201. ine Maier provided a helpful review of the manuscript. Mountjoy, J.J., Barnes, P.M., and Pettinga, J.R., 2009. Morphostructure and evolution of submarine canyons across an active margin: Cook Strait sector of the Hikurangi margin, New Zealand. Marine Geology, 260:45–68. References https://doi.org/10.1016/j.margeo.2009.01.006 Pouderoux, H., Proust, J.-N., Lamarche, G., Orpin, A., and Neil, H., 2012. Barnes, P.M., Lamarche, G., Bialas, J., Henrys, S., Pecher, I., Netzeband, G.L., Postglacial (after 18 ka) deep-sea sedimentation along the Hikurangi sub- Greinert, J., Mountjoy, J.J., Pedley, K., and Crutchley, G., 2010. Tectonic duction margin (New Zealand): characterisation, timing and origin of tur- and geological framework for gas hydrates and cold seeps on the Hiku- bidites. Marine Geology, 295–298:51–76. rangi subduction margin, New Zealand. Marine Geology, 272(1–4):26–48. https://doi.org/10.1016/j.margeo.2011.11.002 https://doi.org/10.1016/j.margeo.2009.03.012 Rettke, R.C., 1981. Probable burial diagenetic and provenance effects on Biscaye, P.E., 1965. Mineralogy and sedimentation of recent deep-sea clay in Dakota Group clay mineralogy, Denver Basin. Journal of Sedimentary the Atlantic Ocean and adjacent seas and oceans. Geological Society of Petrology, 51(2):541–551. https://doi.org/10.1306/212F7CCF-2B24- https://doi.org/10.1130/0016- America Bulletin, 76(7):803–831. 11D7-8648000102C1865D 7606(1965)76[803:MASORD]2.0.CO;2 Robert, C., Stein, R., and Acquaviva, M., 1986. Cenozoic evolution and signifi- Collot, J.-Y., Lewis, K., Lamarache, G., and Lallemand, S., 2001. The giant Rua- cance of clay associations in the New Zealand region of the South Pacific, toria debris avalanche on the northern Hikurangi margin, New Zealand; Deep Sea Drilling Project, Leg 90. In Kennett, J.P., von der Borch, C.C., et result of oblique seamount subduction. Journal of Geophysical Research: al., Initial Reports of the Deep Sea Drilling Project, 90: Washington, DC Solid Earth, 106(B9):19271–19297. (U.S. Govt. Printing Office), 1225–1238. https://doi.org/10.1029/2001JB900004 https://doi.org/10.2973/dsdp.proc.90.130.1986 Davy, B., Hoernle, K., and Werner, R., 2008. Hikurangi Plateau: crustal struc- Rutter, E.H., 1976. The kinetics of rock deformation by pressure solution. ture, rifted formation, and Gondwana subduction history. Geochemistry, Philosophical Transactions of the Royal Society, A: Mathematical, Physical Geophysics, Geosystems, 9(7):Q07004. & Engineering Sciences, 283:203–219. https://www.jstor.org/sta- https://doi.org/10.1029/2007GC001855 ble/74639 Fisher, A.T., and Underwood, M.B., 1995. Calibration of an X-ray diffraction Saffer, D.M., Wallace, L.M., and Petronotis, K., 2017. Expedition 375 Scientific method to determine relative mineral abundances in bulk powders using Prospectus: Hikurangi Subduction Margin Coring and Observatories. matrix singular value decomposition: a test from the Barbados accretion- International Ocean Discovery Program. ary complex. In Shipley, T.H., Ogawa, Y., Blum, P., et al., Proceedings of the https://doi.org/10.14379/iodp.sp.375.2017 Ocean Drilling Program, Initial Reports, 156: College Station, TX (Ocean Saffer, D.M., Wallace, L.M., Barnes, P.M., Pecher, I.A., Petronotis, K.E., LeVay, Drilling Program), 29–37. L.J., Bell, R.E., Crundwell, M.P., Engelmann de Oliveira, C.H., Fagereng, https://doi.org/10.2973/odp.proc.ir.156.103.1995 A., Fulton, P.M., Greve, A., Harris, R.N., Hashimoto, Y., Hüpers, A., Ikari, Kennedy, L.A., and White, J.C., 2001. Low-temperature recrystallization in M.J., Ito, Y., Kitajima, H., Kutterolf, S., Lee, H., Li, X., Luo, M., Malie, P.R., calcite: mechanisms and consequences. Geology, 29(11):1027–1030. Meneghini, F., Morgan, J.K., Noda, A., Rabinowitz, H.S., Savage, H.M., https://doi.org/10.1130/0091- Shepherd, C.L., Shreedharan, S., Solomon, E.A., Underwood, M.B., 7613(2001)029%3C1027:LTRICM%3E2.0.CO;2 Wang, M., Woodhouse, A.D., Bourlange, S.M., Brunet, M.M.Y., Cardona, Land, M., Wust, R.A.J., Robert, C., and Carter, R.M., 2010. Plio-Pleistocene S., Clennell, M.B., Cook, A.E., Dugan, B., Elger, J., Gamboa, D., Geor- paleoclimate in the Southwest Pacific as reflected in clay mineralogy and giopoulou, A., Han, S., Heeschen, K.U., Hu, G., Kim, G.Y., Koge, H., particle size at ODP Site 1119, SE New Zealand. Marine Geology, 274(1– Machado, K.S., McNamara, D.D., Moore, G.F., Mountjoy, J.J., Nole, M.A., 4):165–176. https://doi.org/10.1016/j.margeo.2010.04.001 Owari, S., Paganoni, M., Rose, P.S., Screaton, E.J., Shankar, U., Torres, Lawver, L.A., and Davey, F.J., 2005. River-like erosion within the Bounty sub- M.E., Wang, X., and Wu, H.-Y., 2019. Expedition 372B/375 summary. In marine channel, southwest Pacific Ocean. Marine Geology, 216(3):101– Wallace, L.M., Saffer, D.M., Barnes, P.M., Pecher, I.A., Petronotis, K.E., 106. https://doi.org/10.1016/j.margeo.2005.02.005 LeVay, L.J., and the Expedition 372/375 Scientists, Hikurangi Subduction Lewis, K.B., 1994. The 1500-km-long Hikurangi Channel: trench-axis channel Margin Coring, Logging, and Observatories. Proceedings of the Interna- that escapes its trench, crosses a plateau, and feeds a fan drift. Geo- tional Ocean Discovery Program, 372B/375: College Station, TX (Interna- Marine Letters, 14(1):19–28. https://doi.org/10.1007/BF01204467 tional Ocean Discovery Program). Lewis, K.B., Collot, J.-Y., and Lallemand, S.E., 1998. The dammed Hikurangi https://doi.org/10.14379/iodp.proc.372B375.101.2019 Trough: a channel-fed trench blocked by subducting seamounts and their Shipboard Scientific Party, 1986. Site 594: Chatham Rise. In Kennett, J.P., von wake avalanches (New Zealand–France GeodyNZ Project). Basin der Borch, C.C., et al., Initial Reports of the Deep Sea Drilling Project, 90: Research, 10(4):441–468. Washington, DC (U.S. Government Printing Office), 653–744. https://doi.org/10.1046/j.1365-2117.1998.00080.x https://doi.org/10.2973/dsdp.proc.90.110.1986 Lewis, K.B., and Pantin, H.M., 2001. Channel-axis, overbank and drift sedi- Shipboard Scientific Party, 1999a. Leg 181 summary: southwest Pacific pale- ment waves in the southern Hikurangi Trough, New Zealand. Marine oceanography. In Carter, R.M., McCave, I.N., Richter, C., Carter, L., et al., Geology, 192(1–3):123–151. Proceedings of the Ocean Drilling Program, Initial Reports, 181: College https://doi.org/10.1016/S0025-3227(02)00552-2 Station, TX (Ocean Drilling Program), 1–80. https://doi.org/10.2973/odp.proc.ir.181.101.2000

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Shipboard Scientific Party, 1999b. Site 1119: drift accretion on Canterbury lege Station, TX (International Ocean Discovery Program). Slope. In Carter, R.M., McCave, I.N., Richter, C., Carter, L., et al., Proceed- https://doi.org/10.14379/iodp.proc.372B375.201.2020 ings of the Ocean Drilling Program, Initial Reports, 181: College Station, Villaseñor, T., Jaeger, J.M., Marsaglia, K.M., and Browne, G.H., 2015. Evalua- TX (Ocean Drilling Program), 1–112. tion of the relative roles of global versus local sedimentary controls on https://doi.org/10.2973/odp.proc.ir.181.103.2000 middle to late Pleistocene formation of continental margin strata, Canter- Shipboard Scientific Party, 1999c. Site 1123: north Chatham Drift—a 20-Ma bury Basin, New Zealand. Sedimentology, 62(4):1118–1148. record of the Pacific Deep Western Boundary Current. In Carter, R.M., https://doi.org/10.1111/sed.12181 McCave, I.N., Richter, C., Carter, L., et al., Proceedings of the Ocean Drill- Wallace, L.M., Saffer, D.M., Barnes, P.M., Pecher, I.A., Petronotis, K.E., LeVay, ing Program, Initial Reports, 181: College Station, TX (Ocean Drilling L.J., Bell, R.E., Crundwell, M.P., Engelmann de Oliveira, C.H., Fagereng, Program), 1–184. https://doi.org/10.2973/odp.proc.ir.181.107.2000 A., Fulton, P.M., Greve, A., Harris, R.N., Hashimoto, Y., Hüpers, A., Ikari, Shipboard Scientific Party, 1999d. Site 1124: Rekohu Drift—from the K/T M.J., Ito, Y., Kitajima, H., Kutterolf, S., Lee, H., Li, X., Luo, M., Malie, P.R., boundary to the Deep Western Boundary Current. In Carter, R.M., Meneghini, F., Morgan, J.K., Noda, A., Rabinowitz, H.S., Savage, H.M., McCave, I.N., Richter, C., Carter, L., et al., Proceedings of the Ocean Drill- Shepherd, C.L., Shreedharan, S., Solomon, E.A., Underwood, M.B., ing Program, Initial Reports, 181: College Station, TX (Ocean Drilling Wang, M., Woodhouse, A.D., Bourlange, S.M., Brunet, M.M.Y., Cardona, Program), 1–137. https://doi.org/10.2973/odp.proc.ir.181.108.2000 S., Clennell, M.B., Cook, A.E., Dugan, B., Elger, J., Gamboa, D., Geor- Shipboard Scientific Party, 1999e. Site 1125: productivity under the subtropi- giopoulou, A., Han, S., Heeschen, K.U., Hu, G., Kim, G.Y., Koge, H., cal convergence on north Chatham Slope. In Carter, R.M., McCave, I.N., Machado, K.S., McNamara, D.D., Moore, G.F., Mountjoy, J.J., Nole, M.A., Richter, C., Carter, L., et al., Proceedings of the Ocean Drilling Program, Owari, S., Paganoni, M., Rose, P.S., Screaton, E.J., Shankar, U., Torres, Initial Reports, 181: College Station, TX (Ocean Drilling Program), 1–92. M.E., Wang, X., and Wu, H.-Y., 2019. Expedition 372B/375 methods. In https://doi.org/10.2973/odp.proc.ir.181.109.2000 Wallace, L.M., Saffer, D.M., Barnes, P.M., Pecher, I.A., Petronotis, K.E., Underwood, M.B., Basu, N., Steurer, J., and Udas, S., 2003. Data report: nor- LeVay, L.J., and the Expedition 372/375 Scientists, Hikurangi Subduction malization factors for semiquantitative X-ray diffraction analysis, with Margin Coring, Logging, and Observatories. Proceedings of the Interna- application to DSDP Site 297, Shikoku Basin. In Mikada, H., Moore, G.F., tional Ocean Discovery Program, 372B/375: College Station, TX (Interna- Taira, A., Becker, K., Moore, J.C., and Klaus, A. (Eds.), Proceedings of the tional Ocean Discovery Program). Ocean Drilling Program, Scientific Results, 190/196: College Station, TX https://doi.org/10.14379/iodp.proc.372B375.102.2019 (Ocean Drilling Program), 1–28. Warr, L.N., and Mählmann, R.F., 2015. Recommendations for Kubler Index https://doi.org/10.2973/odp.proc.sr.190196.203.2003 standardization. Clay Minerals, 50(3):283–286. Underwood, M.B., Lawler, N., and McNamara, K., in press. Data report: stan- https://doi.org/10.1180/claymin.2015.050.3.02 dard mineral mixtures, normalization factors, and determination of error Winkler, A., and Dullo, W.-C., 2002. Data report: Miocene to Pleistocene sed- for quantitative X-ray diffraction analyses of bulk powders and clay-sized imentation pattern on the Chatham Rise, New Zealand. In Richter, C. mineral assemblages. In Wallace, L.M., Saffer, D.M., Barnes, P.M., Pecher, (Ed.), Proceedings of the Ocean Drilling Program, Scientific Results, 181: I.A., Petronotis, K.E., LeVay, L.J., and the Expedition 372/375 Scientists, College Station, TX (Ocean Drilling Program), 1–21. Hikurangi Subduction Margin Coring, Logging, and Observatories. Pro- https://doi.org/10.2973/odp.proc.sr.181.206.2002 ceedings of the International Ocean Discovery Program, 372B/375: Col- Wood, R., and Davy, B., 1994. The Hikurangi Plateau. Marine Geology, 118(1– 2):153–173. https://doi.org/10.1016/0025-3227(94)90118-X

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