Late Miocene Submarine Volcanism in ANDRILL AND-1B Drill Core, Ross Embayment, Antarctica

Home , Cape Roberts Project, Hut Point Peninsula, McMurdo Ice Shelf, McMurdo Volcanic Group, Minna Bluff, Mount Bird

Late Miocene submarine volcanism in ANDRILL AND-1B drill core, Ross Embayment, Antarctica

Alessio Di Roberto1, Massimo Pompilio1, and Thomas I. Wilch2 1Istituto Nazionale di Geoﬁ sica e Vulcanologia, sezione di Pisa, Via della Faggiola, 32-56126 Pisa, Italy 2Department of Geological Sciences, Albion College, 611 E. Porter Street, Albion, Michigan 49224, USA

ABSTRACT INTRODUCTION eral hundreds of thousands of years, as at least fi ve inversions of the magnetic polarity occur The ANDRILL McMurdo Ice Shelf initia- The ANDRILL (Antarctic Geological Drill- in this interval. A 2.81-m-thick intermediate tive recovered a 1285-m-long core (AND-1B) ing Program) AND-1B core provides a well-pre- lava fl ow at 646.5–649.2 mbsf was dated to composed of cyclic glacimarine sediments served (>98% core recovery), high-resolution, 6.48 ± 0.13 Ma and provides the only isotopic with interbedded volcanic deposits. The late Neogene record from the nearshore gla- age of the interval (Wilson et al., 2007c). Ini- thickest continuous volcanic sequence by cimarine environment in Antarctica (Naish et tial interpretations of the core were based solely far is ~175 m long and is found at mid-core al., 2007, 2009). The marine core was obtained on core logging done during drilling. Here we depths from 584.19 to 759.32 m below sea- from beneath the McMurdo Ice Shelf, in the provide a more detailed and refi ned interpreta- fl oor. The sequence was logged, and initial Ross Embayment of Antarctica (Fig. 1). The tion of LSU 5, based on reanalysis of the origi- interpretations of lithostratigraphic subdi- McMurdo Ice Shelf drill site is located ~10 km nal nongenetic core log descriptions and the visions were made on ice during drilling in east of Hut Point Peninsula, Ross Island (Fig. 1), actual core, as well as new analysis of accurate late 2006. Subsequent observations, based on in the subsidence moat created by the volcanic high-resolution digital core images and petro- image, petrographic, and scanning electron Ross Island (Naish et al., 2007). The core top is graphic thin sections. We describe and discuss microscopy–energy dispersive spectroscopy situated 943 m below sea level. The core (Fig. 2) primary subaqueous volcanic deposits as well analyses, provide a more detailed, revised consists of intercalated glacigenic, biogenic, and as volcanic-rich epiclastic debris in LSU 5 interpretation of a thick submarine to emer- volcanic deposits, which have been interpreted and examine facies relations within a vertical gent volcanic succession. in terms of changing environmental conditions sequence. Interpretations of eruptive and depo- The sequence is subdivided into two main since ca. 12 Ma (McKay et al., 2009; Naish et sitional processes for both pyroclastic and epi- subsequences on the basis of sediment com- al., 2009). Volcanic rocks form a signifi cant clastic debris defi ne the evolution of this thick position, texture, and alteration style. The component of the core: more than 65,000 of volcaniclastic sequence. The 175-m-thick inter- ~70-m-thick lower subsequence consists the >2 mm clasts (70% of total clast count) are val records intense subaqueous volcanic activity mostly of monothematic stacked volcanic- volcanic (Pompilio et al., 2007), and abundant during a period of limited to no glaciation. rich mudstone and sandstone deposits, which volcanic layers occur throughout the core with are attributed to epiclastic gravity fl ow tur- thicknesses ranging from millimeters to 175 m. EREBUS VOLCANIC PROVINCE bidite processes. This subsequence is con- This study focuses on the 175-m-long volcanic sistent with abundant active volcanism that interval from 584.19 to 759.32 mbsf (meters The AND-1B drill site is located in the Ere- occurred at a distal site with respect to the below seafl oor), which was classifi ed in the ini- bus Volcanic Province (Fig. 1), which comprises drill site. The ~105-m-thick upper subse- tial report core log record as lithostratigraphic alkaline Neogene volcanic centers on the west quence consists mainly of interbedded tuff, unit 5 (LSU 5) by Krissek et al. (2007). fl ank of the intracontinental West Antarctic rift lapilli tuff, and volcanic diamictite. A Late The AND-1B core stratigraphic sequence system in the McMurdo Sound region (Kyle, Miocene (6.48 Ma) 2.81-m-thick subaque- was initially subdivided into eight lithostrati- 1990). Ross Island, a large volcanic complex ously emplaced lava fl ow occurs within the graphic units (LSU 1– LSU 8) composed of just north of the drill site, is dominated by the second subsequence. This second subse- several depositional sediment facies. Among active 3794 m Mount Erebus, surrounded radi- quence is attributed to recurring cycles of the eight, LSU 5 (Fig. 2) is distinctive on the ally by the Mount Terror, Mount Bird, and submarine to emergent volcanic activity that basis of its high volcanic content, lack of diato- Hut Point Peninsula eruptive centers (Fig. 1). occurred proximal to the drill site. This new mite, and varied range of siliciclastic sediments Mount Erebus is composed mostly of basanite data set provides (1) the fi rst rock evidence (Krissek et al., 2007). LSU 5 includes differ- and its fractionated product phonolite (Kyle, of signifi cant Late Miocene submarine volca- ent depositional facies, the products of which 1977, 1981; Kyle et al., 1992); the oldest Ere- nic activity in the Ross Embayment during a can be attributed to both reworked and primary bus outcrops are low-elevation 1.3 Ma Cape period of no to limited glaciation, and (2) a volcanic depositional processes. Preliminary Barne rock (Esser et al., 2004). Mount Bird rich stratigraphic record that elucidates sub- paleomagnetic studies of the AND-1B core car- and Mount Terror are basanitic shield volca- marine volcano-sedimentary processes in an ried out on ice (Wilson et al., 2007b) revealed noes that erupted 4.6–3.8 Ma and 1.7–1.3 Ma, offshore setting. that LSU 5 covers a time span of at least sev- respectively (Wright and Kyle, 1990a, 1990b;

Geosphere; October 2010; v. 6; no. 5; p. 524–536; doi: 10.1130/GES00537.1; 6 ﬁ gures; 1 table; 4 supplemental ﬁ gures.

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Kyle and Muncy, 1989). Hut Point Peninsula, Morning, and Mount Discovery are all major the fl ow of the Ross Ice Shelf into McMurdo located just 10 km west of the drill site, is the volcanic centers. The earliest known volcanic Sound (Wilch et al., 2008; Talarico and San- most proximal subaerial volcanic outcrop to the outcrops date to 18.7 Ma and include extensive droni, 2009). Glacial reconstructions show that drill site. Surface mapping and drill core records evolved alkaline explosive vent complexes on fl owlines of a grounded ice sheet in the Ross from the 1970s at Hut Point Peninsula reveal a the northwestern and northeastern slopes of Embayment directed to the drill site would Pleistocene (since 1.3 Ma) record of evolving Mount Morning (Martin et al., 2009) and far- sweep around Minna Bluff (12–6 Ma) and past alkaline volcanism, dominated by basanitic- ther south, at Mason Spur and Helms Bluff White Island (7.7–0.2 Ma) (Naish et al., 2009). hawaiitic cinder cones and a phonolite dome at (Armstrong, 1978; Kyle and Muncy, 1989; Two major glacial unconformities dated as 9.6 the surface (Kyle, 1981). Kyle, 1990). A thick pumice lapilli tuff, dated and ca. 10.4 Ma on Minna Bluff are attributed Major volcanic centers are also located to 22 Ma, was also found in the Cape Roberts to erosion by an early Ross Ice Sheet (Fargo et south of the AND-1B drill site. White Island, Project CRP-2 drill hole (Armienti, et al., 2001; al., 2008). Talarico and Sandroni (2009) sug- the magmatism of which dates to 7.7 Ma, is a McIntosh, 2001). Late Miocene volcanism gested that clasts from both Minna Bluff and basanite to tephriphonolite shield volcano and with ages similar to the ca. 6.5 Ma lava fl ow in White Island are important components of gla- is the next most proximal volcano, located LSU 5 is known to have occurred at both White cial deposits in the AND-1B core. 15 km south-southeast of the drill site (Cooper Island and Minna Bluff. Minna Bluff, south Recent aeromagnetic studies have also sug- et al., 2007). Farther south (40–60 km from the of the drill site, formed between 12 and 6 Ma gested the possible existence of submarine vol- drill site), Black Island, Minna Bluff, Mount and has since acted as an important barrier to canoes beneath the McMurdo Ice Shelf, as well

166°E 168°E 170°E 164°E Ross Sea 79°S Ross

Antarctica Island Mt. Bird Mt.Terror 4-3 Ma <0.82-1.75 Ma Ross Ice Shelf Mt.Erebus <1.31 Ma

78°S CRP1-3 McMurdo Hut Point Peninsula 170°E 162°E Sound <2 Ma AND-1B

79°S White Island 7.65-0.17 Ma

Brown Black Island Peninsula 11.19-1.69 Ma

Minna Bluff 160°E 10.4-7.26 Ma 168°E Mt.Discovery 3-2 Ma Eruptive complex Coring site Mt.Morning 40 Km °S 8 <18.7 Ma 7 160°E 162°E 164°E 166°E

Figure 1. Location of the core site and main geographical features of the Erebus Volcanic Province. Map also shows volcanic centers (encircled with different colors) belonging to the Erebus Volcanic Province with relative time span of activity. Satellite image from SSEC/UW-Madison AWS Network (Space Science and Engineering Center, University of Wisconsin Automatic Weather Station, http:// amrc.ssec.wisc.edu/). CRP1–3—Location of Cape Roberts Project 1–3 drill holes. The box indicates the area described in Figure 5.

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Silt

Age

Unit

Clay

San

avel

Depth

Gravel

Silt

Age

Unit

Clay b

Depth

Gr vf f m c vc g p c b vf f m c vc g p c

Silt

Age

Unit

Clay

Sand

Depth

Gravel

vel

lt vf f m cvc g p c b

A Cla

San

1.1

Dep 50 505 B Gra

4.2 1.104 Ma vf f m c vc g p c b Pleistocene 2.1 C 2.2 605 100 1.65 Ma 510

2.3 D 1.67 Ma 705

2.4 610 150 515

3.1 3.2 710 615 200 520 715 620 250 525

3.3 720 625 530 300 725

U5A 3.4 630

535 LS 3.5 350 730

Pliocene

Miocene

3.6 635 540 400

4.3 735

4.1 640

545 cene

450 Mio 740

4.8 Ma Pliocene 645 550

4.2

Early

SU5B 6.48 Ma 745

500 L 650 B 555 750 4.3 550 655 560 4.4 600 755

1 660 5. C 565 6.48 Ma 5.2 760 650 665 570

5.3 765 700 670 D 575 5.4 770 750 675 580

4.4 775 680 800 585

6.1 780 6.1 685 850 590

Miocene 785 690 900 590

LSU5B

6.2 790 695

950 LSU5A 795

6.3 1000 Diatomite

v Volcanic 40Ar/ 39 Ar ages 1050 Siltstone Hiatus 1100 Diamictite 6.4 1150 Lava flow 1200 Mudstone/sandstone

7.1 1250 13.57 Ma Sandstone/conglomerate 8.1

Figure 2. Stratigraphic summary of the AND-1B core from 500 to 800 m below seaﬂ oor (mbsf). Lithologies are plotted against depth.

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TABLE 1. LITHOFACIES DESCRIPTION AND INTERPRETATION OF DEPOSITIONAL PROCESS Facies Bed description Components Volcanic/Glacial process 2 to 6 Volcanic- Cm- to mm-thick beds of siltstone, clayey Reworked glass shards, pumice and scoria, Turbidity currents from a far rich mudstone to siltstone, and fine- to medium-grained sandstone, lava fragments, and magmatic crystals; located grounding sandstone interlaminated and interbedded at millimeter to granitoids, metasediments and mudstone centimeter scales (supplemental material 1) intraclasts 11a - Lapilli Tuff and Cm- to dm-thick, massive to crudely stratifi ed, coarse Pristine pumice, scoria and glass shards; High- to low-concentrated, Tuff lapilli tuff to fi ne tuff, normally graded to well- few igneous crystals, and dense, angular eruption-fed, aqueous bedded (supplemental material 2) lava fragments density current 11b - Lava Flow Fine-grained tephrite (supplemental material 3) N.A. Submarine lava fl ow 11c - Volcanic Cm- to m-thick, coarse sand to breccia, massive Dense, angular lavas, scoria and oxidized High-density mass fl ows Diamictite to very poorly to faintly bedded (supplemental altered volcanics (debris fl ows) material 4) Note: N.A.—not available.

as submarine lava fl ow extensions of exposed FACIES cross-lamination is mostly limited to coarse silt- volcanic islands including White Island (Wilson stone. Incomplete Bouma sequences sometimes et al., 2007a). These inferred submarine volca- Krissek et al. (2007) grouped primary and occur. Basal contacts with underlying sediments noes have not been sampled or dated. near-primary volcanic rocks and sediments in are either sharp or diffuse, whereas in the top- a single facies (designated #11 in core logs), most part convolute bedding and fl uid escape TECHNIQUES which includes lapilli tuff, volcanic diamictite, structures are common. and a tephritic lava fl ow. Some of these deposits Sandstone is less common and is mostly rep- The AND-1B core was logged fi rst on ice were interpreted as slightly reworked by sedi- resented by volcanic fi ne- to medium-grained during drilling in late 2006 (Krissek et al., ment gravity fl ow processes but less reworked sandstone, which is normally graded to volca- 2007; Pompilio et al., 2007). Core description than volcanic-rich equivalents of other facies. nic siltstone; some nongraded massive beds was conducted by the ANDRILL McMurdo Volcaniclastic rocks were also included in pri- also occur. Incipient planar laminations, cross- Ice Shelf sedimentology-stratigraphy team, fol- marily nonvolcanic siliciclastic facies, includ- stratifi cation, and climbing ripple laminations lowing procedures and operations outlined in ing facies #2 (mudstone), #3 (interstratifi ed are common. Basal contacts of sandstone units the Scientifi c Logistics Implementation Plan mudstone and sandstone), #4 (mudstone with are usually sharp and interpreted as erosional. for the ANDRILL McMurdo Ice Shelf Project interdispersed common clasts), #5 (rhythmi- The majority of beds are constituted by a hetero- (SLIP; Naish et al., 2006). Preliminary strati- cally interlaminated mudstone with siltstone or lithic mix of volcanic-derived clasts (i.e., glass graphic and petrologic data on volcanic rocks sandstone) and #6 (sandstone) (Krissek et al., shards, variously vesicular pumices and scoria, in the AND-1B core were reported in Krissek 2007). Here we redefi ne and redescribe these dense lava fragments, and magmatic crystals) et al. (2007) and in Pompilio et al. (2007), and facies in the context of the LSU 5 volcanic inter- with variable and sometimes signifi cant amounts provide the starting point for the analysis and val. On the basis of detailed stratigraphic, tex- of mainly basement-derived clasts (granitoids, interpretations in this study. tural, and component analyses we subdivided metasediments) and mudstone intraclasts. Both Additional macroscopic and stratigraphic facies 11 into 3 subfacies (11a–11c), keep- volcanic-derived and crystalline rock fragments descriptions of LSU 5 have been further imple- ing the same number for coherence (Table 1; are subangular to well rounded and show traces mented by analysis of high-resolution digital supplemental fi gures); this further subdivision of intense reworking by granule abrasion and images (150 dpi) of split drill core visualized in was considered necessary to detail the complex comminution. Sandstone and siltstone are usu- a desktop workstation using Corelyzer software architecture of LSU 5. ally matrix supported; the matrix is composed of (Rao et al., 2006). These images were studied silt-sized (tens of microns) volcanic fragments in order to infer mechanisms of eruption, trans- Facies 2–6: Volcanic-Rich Mudstone port, and deposition. Macroscopic observations to Sandstone 1 of digital images and core were integrated with Supplemental Figure 1. PDF fi le image of the uppermost half of the core is composed of hetero- detailed sample characterization performed on We group the fi ve facies (facies 2–6) iden- lithic, volcanic-rich, clast-rich muddy diamictite. more than 50 thin sections distributed within tifi ed by Krissek et al. (2007) as products of Beds are composed of granule- to pebble-sized (up LSU 5; additional sampling was undertaken reworking of primary volcanic deposits into a to few cm in diameter) clasts of granitoids, metasedi- where particular structures are evident or in single facies association (Fig. 3A; Supplemen- ments, volcanics, and mudstone intraclasts immersed correspondence to specifi c sedimentary units. tal Figure 11). In the original facies description, in a heterolithic, volcanic-rich, sand-sized matrix. This part of the core is well stratifi ed horizontally Selected sample microtextures and macrotex- these volcanic units were included as varia- with stratifi cations defi ned by color variation, hori- tures were further analyzed using scanning tions of facies that were mostly siliciclastic. zontal alignment of clast long axes, and variations electron microscopy–energy dispersive spec- The lower part of LSU 5 is dominated by these in grain size. The lowermost half of the interval is troscopy Philips XL30 scanning electron micro- facies (Fig. 4), including dark gray to black, composed of stacked layers of very dark greenish to black volcanic coarse sandstone with dispersed scope (accelerating voltage 20 kV, beam current centimeter- to millimeter-thick beds of siltstone, granules, volcanic fi ne- to medium-grained sand- 1 nA, working distance 10 mm), equipped with clayey siltstone, and fi ne- to medium-grained stone, volcanic fi ne sandstone, volcanic claystone, energy dispersive X-ray analysis (DX 4; Earth sandstone, interlaminated and interbedded at volcanic siltstone, weakly stratifi ed silty claystone/ Science Department of Pisa University) and millimeter to centimeter scales. Beds commonly clayey siltstone, and volcanic mudstone. If you are backscattered electron images collected with a exhibit normal grading, although nongraded viewing the PDF of this paper or reading it offl ine, please visit http://dx.doi.org/10.1130/GES00537.S1 JEOL JXA 8200 Superprobe (Istituto Nazionale massive beds also occur. Planar lamination and or the full-text article on www.gsapubs.org to view di Geofi sica e Vulcanologia, Rome). cross-stratifi cation are common while ripple Supplemental Figure 1.

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A A1 clayclay

heterolithicheterolithic ssandand

5 mm 1 mm

B B 1 quenchedquenched rimrim zeolitezeolite

pumicespumices zeolitezeolite 5 mm 500 µm

C C1 analcimeanalcime pyritepyrite

pyritepyrite

5 mm 250 µm

DDDD1

lavalava lavalava

5 mm 500 µm pumicepumice pumicepumice

Figure 3. Thin section optical (left column) and scanning electron microscope backscattered images (right column) of selected representative samples of relevant facies in LSU 5: A and A1—heterolithic epiclastic sandstones (facies 2–6); B and B1—volcanic tuff (facies 11a); C and C1—lava ﬂ ow (facies 11b); D and D1—volcanic diamictites (facies 11c).

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large vesicles (hundreds of microns in diameter) Facies

Silt

Clay Figure 4. Composite stratigraphic log of

Unit

Sand

Depth to honeycomb-textured clasts with fi ne vesicles Gravel LSU 5A and LSU 5B, showing facies distri- vf fmc vc gpcb 2-6 11a 11b 11c (few tens of microns in diameter). Vesicles are bution with depth (in mbsf). Lithologies are frequently convoluted and deformed with some 585 the same as Figure 2. clasts showing a probable vesiculation after fragmentation. In these clasts, early synerup- 590 tive vesiculation is preserved in vesicles aligned 595 and minerals, clay aggregates, and crystalline to below quenched and fractured clast rims, while microcrystalline zeolites. post-fragmentation processes give rise to unde- 600 formed, mostly spherical vesicles developed 605 Facies 11a: Lapilli Tuff and Tuff in the inner part of the clast. A large portion of fragments exhibit marginal quenching and 610 Lapilli tuff and tuff (Fig. 3B; Supplemen- widespread fracturing. The nature of the vesicu- 2 615 tal Figure 2 ) are one of the most widespread larity and quenching, in addition to the presence deposits within LSU 5 (Fig. 4). The units are of fl uidal deformation of the thin glass tips, sug- 620 composed of centimeter- to decimeter-thick, gests possible heat retention during deposition. 625 massive to crudely stratifi ed, coarse lapilli tuff Stratigraphic relationships between mainly to fi ne lapilli tuff (sizes after White and Hough- massive lapilli tuff and laminated fi ne tuff 630 ton, 2006) normally graded to or overlain by intervals are variable. Three main cases occur: well-bedded, extremely fi ne to fi ne tuff with (1) deposits with similar proportion of lapilli 635 diffuse parallel to low-angle cross-laminations. tuff and tuff (the most common); (2) much

LSU5B 640 The coarser lapilli tuff beds are moderately to reduced portions of lapilli tuff overlain by poorly sorted and are composed of juvenile extensively developed fi ne tuff; and (3) multiple 645 greenish-yellowish clasts set in a dark green stacked sequences of lapilli tuff overlain by, and 650 matrix; they are matrix to clast supported and separated by erosion surfaces from, very limited sorting and/or bedding may be obscured by occurrences of fi ne tuff. Laminated fi ne-grained 655 alteration, although normal grading is obvious tuff is frequently overlain by yellow-gray volca- 660 in some units. The fi ner tuff beds are moderately nic siltstone or claystone, which is moderately to well sorted, commonly clast supported and to intensely bioturbated with frequent convolu- 665 open-framework textured, and rarely graded. tion, fl uid escape structures, and load structures. 670 Juvenile fragments of both lapilli tuff and fi ne Coarse tuff is usually cemented by a micritic to tuff beds are composed of texturally homoge- crystalline matrix made up by clay and zeolites 675 neous pumice, scoria and glass shards mixed (mainly analcime and phillipsite). Fine-grained with reduced amounts of igneous crystals, and tuff is always cemented by highly crystalline 680 dense, angular lava fragments. Abundant red- zeolite (phillipsite and analcime). 685 dish oxidized fragments occur especially in the A few layers of parallel to low-angle lami- uppermost part of the sequence. Juvenile frag- nated, extremely fi ne, well-sorted tuff also 690 ments are mostly aphyric, with few crystals of occur just above the top of LSU 5 at 584.19– 695 plagioclase, pyroxene, amphibole, and altered 584.84 mbsf. Although Krissek et al. (2007) olivine in a glassy matrix. Some juvenile frag- ascribed these layers to LSU 4.4, these tuffs 700 ments are tachylitic with abundant microlaths of can be considered genetically linked to similar 705 plagioclase frequently altered and replaced by deposits of LSU 5. These tuff beds are centime- clay minerals and chlorite. ter to decimeter thick and clast supported, and 710 Within lapilli tuff, volcanic fragments are are composed of y-shaped to blocky, poorly 715 variably vesicular, likely representing a contin- vesicular and aphyric glass shards. Calcite to uum between end members represented by clasts zeolite crystalline cement constitutes the matrix. 720 with low vesicularity made up of few relatively Many shards exhibit concentric rims of devit- rifi ed glass a few tens of microns thick and in

725 LSU5A some cases tiny perlitic fractures. 730 2Supplemental Figure 2. PDF fi le image of pumiceous lapilli tuff to tuff. Deposits are moderately Facies 11b: Lava Flow 735 well sorted and are composed of clasts ranging from coarse ash to lapilli (~1 cm). Lapilli tuff are clast- A 2.81-m-thick lava fl ow occurs within the 740 supported. Although sorting and bedding are par- tially obscured by alteration, faint normal grading LSU 5 sequence from 646.49 to 649.30 mbsf 745 occurs. Few coarse sand-sized grains of red scoria (Figs. 3C and 4; Supplemental Figure 33). The occur in the interval. Clasts are often cemented by 750 lava fl ow is a fi ne-grained tephrite, with few calcite. Patches and lenses of pyrite occur. If you are large (>1 mm) feldspar phenocrysts set in a 755 viewing the PDF of this paper or reading it offl ine, please visit http://dx.doi.org/10.1130/GES00537.S2 pilotaxitic groundmass. The upper lava fl ow 760 or the full-text article on www.gsapubs.org to view contact exhibits a 1–2-cm-thick alteration rim, Supplemental Figure 2. composed of a series of concentric rinds of

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calcite and zeolite. Similarly, the basal 2 cm of to sand-sized matrix. Some lava clasts have a and was put at 688.92 mbsf since above this the fl ow in contact with underlying sediments jig-saw texture, suggesting short transport after depth tuff beds became predominant. are also altered to calcite, zeolite (Krissek et breakage; accidental very rounded, yellow al., 2007), and pyrite. Soft-sediment deforma- claystone intraclasts also occur. Sequence LSU 5B (584.19–688.92 mbsf: tion occurs at the contact between the lava fl ow The volcanic diamictite matrix is dark green LSU 5.3–5.1) and underlying muddy sediments. Abundant and dominantly composed of clay- and zeolite- millimeter-wide fractures and sparse vesicles altered volcanic ash. Volcanic diamictite beds Sequence LSU 5B comprises three of the are evident within the lava and are now occupied are usually <2 m thick (Krissek et al., 2007), but lithostratigraphic subunits (LSU 5.1–5.3) traced by secondary calcite and silica veins and amyg- sequences of stacked diamictite beds as thick as by Krissek et al. (2007), as well as the lowest dales. Fractures near the top and base of the lava 10 m also occur. 2 m of LSU 4.4. The sequence extends from are generally parallel to the bounding surfaces; 688.92 to 584.19 mbsf and is largely composed fractures in the core of the lava are inclined to STRATIGRAPHY OF AND-1B: LSU 5 of stacked tuff and lapilli tuff beds (facies 11a) anastamosing (Krissek et al., 2007). There is no and volcanic diamictite (facies 11c). Intervals of clear evidence of pillow-like structures in this We report here observational data collected interleaved volcanic-rich sandy claystone and lava. The occurrence of glassy rinds, fl ow and off ice, including results from the examina- dark sandstone as thick as several meters (facies shear textures, and the presence of a subaqueous tion of high-resolution images of the core and 3, 4, 5; e.g., between 608.22 and 618.58 mbsf) gravity fl ow just above the lava fl ow indicate a analysis of thin sections by optical and scan- also occur. Deposits consist of dark olive to gray submarine setting (Pompilio et al., 2007). ning electron microscope. This information sandy claystone beds, to 1 m thick, interfi ngered integrates and expands upon previous on-ice with millimeter- to centimeter-thick sandstone, Facies 11c: Volcanic Diamictite core descriptions summarized in Krissek et al. laminated to massive and frequently biotur- (2007). The LSU 5 was originally subdivided on bated, though the dark color may obscure the Diamictite (Fig. 3D; Supplemental Fig- ice by the AND-1B sedimentology team into 4 degree of bioturbation present. ure 44), in which volcanic detritus is domi- subunits, LSU 5.1–5.4, that were differentiated The sequence also includes the 2.81-m-thick nant, is an important component of the LSU on the basis of lithostratigraphic characteristics. lava fl ow (facies 11b) found from 646.49 to 5 volcanic sequence and represents a variation Here we simplify the model and, on the basis 649.30 mbsf. The lava fl ow is associated with of the heterolithic facies 9 (stratifi ed diamic- of volcanic and sedimentologic facies analysis incipiently bedded, very poorly sorted, and tite) and 10 (massive diamictite) described (Fig. 4), subdivide the entire LSU 5 into two crudely normally graded volcanic diamictites by Krissek et al. (2007). Most of the volcanic sequences, LSU 5A and LSU 5B. (facies 11c). Volcanic diamictites, to ~8 m thick, diamictite is massive, very poorly sorted, and are widespread in the sequence even when not very poorly to faintly bedded, although normal Sequence LSU 5A (688.92–759.32 mbsf: associated with a lava fl ow (e.g., 674.83–683.13, grading appears in some examples. The volca- LSU 5.4) 655.45–658.41, and 618.93–620.50 mbsf). nic diamictites are composed of coarse sand- to Several stacked extremely fi ne tuff lay- pebble-sized clasts of dense, angular lavas with Sequence LSU 5A includes the whole of LSU ers occur very close to the topmost part of the textures analogous to the lava fl ow, scoria, and 5.4 of Krissek et al. (2007) and extends from sequence (584.19–584.84 mbsf) (facies 11b); oxidized altered volcanics enclosed in a clay- 688.92 to 759.32 mbsf. It comprises an almost they are almost completely composed of well- monothematic sequence of siltstone, clayey silt- sorted, y-shaped to blocky glass shards with stone, and sandstone belonging to facies 2–6 traces of glass hydration, slight glass rim leach- 3Supplemental Figure 3. PDF fi le image of lava fl ow. The lava is a fi ne-grained tephrite, with few of Krissek et al. (2007). Beds are volcanic rich ing, and pervasive cracks. The deposit is clast large (>1 mm) feldspar phenocrysts set in a pilotax- throughout LSU 5A, with variable quantities of supported and cemented with crystalline calcite. itic groundmass. The fracture pattern is variable from nonvolcanic, mainly crystalline rock fragments. the top of the interval toward the base. Pyrite coat- Crystalline rock fragments are more abun- FACIES INTERPRETATIONS ing and secondary minerals are abundant in fractures and vesicles and at the sediment contact. If you are dant in some layers in the lowermost meters viewing the PDF of this paper or reading it offl ine, of the subsequence (e.g., in the volcanic-rich, Rationale please visit http://dx.doi.org/10.1130/GES00537.S3 clast-rich muddy diamictite located at 750.54– or the full-text article on www.gsapubs.org to view 751.01 mbsf). Siltstone, clayey siltstone, and Submarine, nonwelded pyroclastic debris Supplemental Figure 3. sandstone are periodically interrupted by yel- deposits that are directly related to volcanic lowish, millimeter- to centimeter-thick laminae explosions are very diffi cult to discriminate enriched in biogenic silica sediments. Bioturba- from cold, remobilized, volcanogenic mass fl ow 4 Supplemental Figure 4. PDF fi le image of volca- tion is variable and sometimes masked by sedi- deposits because of the lack of unequivocal dis- nic diamictite predominantly composed of granule- to small pebble-sized (up to 4 cm in diameter) clasts ment cementation. tinctive criteria. The distinction is more diffi cult of pumice, scoria, and lava immersed in sand-sized In the uppermost part of LSU 5A (688.92– where deposits are altered, metamorphosed, matrix. The volcanic clasts are subangular to angu- 714.80 mbsf), centimeter- to decimeter-thick and/or deformed as in ancient sequences or lar; red vesicular scoria are abundant. Beds are faint- beds of lapilli tuff and tuff (facies 11b) are where sediment exposure is laterally limited ly stratifi ed horizontally by changes in clast content and dominant clast types at decimetric scale. The interfi ngered with laminated sandstone and and depositional structures are poorly traceable. matrix of this breccia is mainly composed of pum- siltstone. The progressive increase in the num- Notwithstanding, a number of recent works ice sand that typically forms >50% of the matrix but ber and thickness of tuff beds toward the top have demonstrated that discrimination of sub- locally exceeds 90%. The matrix also includes zeo- of sequence LSU 5A marks the transition into marine primary pyroclastic deposits from those lites and calcite. If you are viewing the PDF of this sequence LSU 5B. The passage from sequence subjected to reworking and redeposition (epi- paper or reading it offl ine, please visit http://dx.doi .org/10.1130/GES00537.S4 or the full-text article on LSU 5A to sequence LSU 5B is not marked by clastic) is possible where detailed facies analy- www.gsapubs.org to view Supplemental Figure 4. a sharp unconformity, hiatus, or erosive surface, sis is performed (White, 1996; Skilling, 1994;

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Smellie and Hole, 1997; Mueller et al., 2000). stone, and sandstone, as well as intense rework- absence of grain abrasion, and the complete Moreover the nature, texture, and morphologi- ing of clasts all point to a prevalent epiclastic ori- preservation of clasts with complex shapes cal properties of clasts can be used to help in gin of sediments. Turbidites may be deposited by (Doucet et al., 1994; White, 2000). The evi- discriminating the sediment origin. turbidity currents resulting from grounding-line dence for heat retention associated with larger Basaltic eruptions at shallow to moderate fan processes or volcanic and/or tectonic activ- clasts during their deposition, i.e., marginal depths, such as those observed at Surtsey Vol- ity. The fi ne nature of the sediment and the near quenching, fl attened and convoluted vesicles, cano, Iceland (Kokelaar, 1983), Falcon Island, total absence of dropstones indicate that turbid- and deformation of thin glass tips, supports the Tonga (Hoffmeister et al., 1929), Capelinhos, ity currents may develop from a grounding line hypothesis of a primary deposition of synerup- Faial Island, Azores (Machado et al., 1962; located far from the drill site and may funnel tive hot gravity fl ows. The presence of sparse Cole et al., 1996, 2001; Solgevik et al., 2007; fi ne-grained products produced by fl uvial and tuff in the uppermost part of LSU 5A indicates Zanon et al., 2008), Kick’em-Jenny (Lesser glacial erosion of volcanic and basement rock. the initiation of sporadic explosive subaque- Antilles), and the recent eruption off the coast Similar deposits may be produced from the mix- ous activity close to the drill site. The limited of Nuku’alofa, Tonga (Associated Press, 2009), ing of primary submarine volcanic deposits with thickness and small grain size of these deposits produce great amounts of fragmental volcanic nonvolcanic detritus; the mixing may occur both as well as their intermittent occurrence within products. Volcanic rock and detritus can be prior to or during the transport toward the deeper the LSU 5A sequence suggest that they resulted transferred to the basins either by eruptive or portion of the sedimentary system, with the non- from either low-energy eruptive activity or a dis- syneruptive processes like subaqueous pyro- volcanic fractions supplied by glacier tongues tal volcanic source (Song and Lo, 2002; Allen clastic fl ows and eruption-fed aqueous density descending from the Transantarctic Mountain et al., 2007). currents. Alternatively, volcanic material tempo- front and by grounding-line processes. rarily stored on the cone fl anks can be redistrib- A signifi cant change in depositional environ- Sequence LSU 5B: 584.19–688.92 mbsf uted into adjacent basins via gravity fl ows. ment and processes occurs in the upper part of Primary basaltic volcaniclastic deposits pro- the LSU 5A sequence. The presence of lapilli Sequence LSU 5B, the upper sequence, rep- duced by recent and ancient mafi c underwater tuff and tuff in the upper meters of sequence resents a fundamental change in the sedimentary eruptions, such as at Greenland (Mueller et LSU 5A marks a transition from the predomi- system both in terms of the nature and source al., 2000), are typifi ed by a very homogeneous nantly epiclastic sedimentation to a system of sediments, as well as the main depositional (monomictic) composition and dominated by dominated by materials directly derived from processes. The base of sequence LSU 5B is a poorly sorted mixture of mafi c scoria frag- explosive volcanic activity. Though core expo- not marked by a sharp unconformity, hiatus, or ments, glass shards, and crystals. The angular sure is limited, the tuff and lapilli tuff depos- erosive surface and was placed at 688.92 mbsf clasts preserve primary fragile structures (e.g., its are similar to eruption-fed density current because at this depth coarse tuff beds begin to thin glassy rims) and are unabraded. Epiclastic deposits in recent or ancient submarine and dominate. Lapilli tuff and tuff that compose or reworked volcanic-rich deposits, not directly subglacial explosive volcanic successions in most of the second sequence resemble tuff cou- related to a single eruption, may originate from several locations described by several authors plets described in the upper part of sequence A, either subaerial pyroclastic sediments or from (e.g., Fiske, 1963; Mueller and White, 1992; although the latter are characterized by thicker submarine volcanic fl ows. Such reworking White, 1996; Smellie and Hole, 1997; Fiske et beds and coarser clast size. We attribute the bulk occurs in particular during periods of quies- al., 1998; Smellie, 1999; White and Houghton, of the LSU 5B succession to submarine explo- cence of the eruptive activity. Primary pyroclas- 1999; White, 2000). sive activity. Coarser grain size, bed thicknesses, tic deposits may be eroded and transported by Poorly sorted and massive to crudely stratifi ed and increase in frequency of lapilli tuff suggest fl uvial, marine, and glacial systems. Volcanic lapilli tuff may represent the main body of highly an increase of explosive energy or a shift to an fragments occurring in epiclastic deposits usu- concentrated, eruption-fed, aqueous density cur- eruptive vent closer to the drill site. ally show traces of intense reworking such as rents with high sedimentation rates, whereas the A key volcanic feature in the core is the rounding, abrasion, and comminution, and are thin-bedded and parallel to low-angle, cross- 2.81-m-thick lava fl ow (646.49–649.30 mbsf). variably mixed with nonvolcanic material from laminated uppermost part of the tuff may repre- The quenched rims on the fl ow, the presence within the depositional basin, or derived from sent deposition by cogenetic low-density fl ows of soft-sediment deformation at its base, and source rocks outside the basin area, including (White, 2000; Mueller, 2003). These low-density the analysis of bounding facies suggest that the siliciclastic and crystalline basement rocks and/ fl ows may develop in the tail of the eruption-fed lava fl ow was emplaced in a subaqueous envi- or bioclastic fragments. Lithological and sedi- aqueous density currents (Kokelaar and Busby, ronment. According to Walker’s (1973) model, mentological observations indicate that both 1992; Martin and White, 2001; Mueller, 2003) a subaerial tephritic (basaltic) lava fl ow with epiclastic and primary volcaniclastic deposits or by the collapse of fi ne sediments injected into thickness similar to that cored should be fed by occur throughout LSU 5 and provide a record of the water column by subaqueous pyroclastic a vent located within 4 km from the drill site. an evolving submarine volcanic complex. jets (the same that generate eruption-fed density Considering that the emplacement in water currents) (Cashman and Fiske, 1991). The fi nal implies a higher cooling rate and several other Sequence LSU 5A: 688.92–759.30 mbsf drape may produce a very fi ne ash deposit elutri- processes that promote higher viscosity and ated from the main part of the fl ow during the shorter lengths, the distance of 4 km for the vent A combination of sedimentary structures, transport (Mueller, 2003) and deposited as fall- position should be considered as maximum including bedding, planar and low-angle cross- out through the water column. Despite its own relevance and signifi cance stratifi cation, normal grading, partial Bouma The interpretation of a primary volcanic den- as a time stratigraphic horizon, the occurrence sequences, convolute bedding, and rip-up clasts, sity fl ow origin for these deposits is based on of lava offers a context for interpretation of the indicates a turbidity current origin for the major- several key features, including the occurrence volcanic diamictites that are in contact with ity of sequence LSU 5A. Among turbidites, the of very homogeneous components (scoria and this coherent fl ow and found at various strati- dominance of heterolithic siltstone, silty clay- dense lava fragments), the almost complete graphic levels in LSU 5B. As described here,

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the volcanic diamictite is composed of juvenile phases of the same eruption depending upon shallow to emerging volcanic vent or eruption lava clasts that are texturally identical to the the rate of extrusion and volatile content of the column. Further evidence of the emergence of lava fl ow and by pumiceous fragments similar magma. Eruptive activity was intermittent and the volcanic vent is the occurrence of stacked to those composing the tuff. We interpret these likely initiated by high eruption rates and high beds of extremely fi ne tuff, likely produced by diamictites as a mixture of clasts derived from volatile contents that favor submarine fi re foun- contact of a vesiculating, ash-producing melt autoclastic processes acting on the lava fl ow taining or subaqueous pyroclastic jets, which with external water, in the uppermost part of the and clasts derived by the subaqueous explosive were transformed into eruption-fed density cur- LSU 5B (584.19–584.84 mbsf). activity associated with the emplacement of a rents. During the late stages of these explosive The presence of volcanic edifi ces close to submarine lava fl ow. High-density mass fl ows eruptions lower eruption rates and diminished the drill site was hypothesized by Wilson et al. (debris fl ows) related to cycles of growth and volatile content may produce lava fl ows and their (2007a) on the basis of the presence of large collapse of a local volcanic pile may develop in associated diamictites (Stix and Gorton, 1989). accumulation of magnetically susceptible detri- front of the lava fl ow so that volcanic diamictites The abundant reddish oxidized fragments in tus surrounding small (1–2 km wavelength), may be found both at the base as well as above lava-related diamictites and in tuffs suggest ther- discrete, circular anomalies south of Hut Point it. The presence of diamictites without related mal oxidation conditions of high-temperature Peninsula (Fig. 5). lava fl ows is attributed to the higher mobility volcanic materials (Cas and Wright, 1987; The presence within the volcanic sequence of of mass fl ows compared to lava fl ows. Thus Song and Lo, 2002). Oxidizing conditions can intervals composed of bioturbated, olive-green diamictites are proxies for lava fl ows that did be reached either during the emergence of the to yellowish volcanic-rich epiclastic claystone not reach the drill site. volcanic vent above sea level or if the erup- interstratifi ed with volcanic-rich epiclastic sand- A continuum exists between processes that led tive plume (or fountain) reaches and breaks stone (facies 11a; e.g., 608–618 mbsf) indicates to the formation of eruption-fed density current the sea surface; in this sense reddish oxidized that volcanic activity was periodically inter- deposits and lava fl ows; thus, these processes volcanic fragments may indicate the passage rupted by periods of quiescence. During these and resultant processes may represent different from a submarine eruptive environment to a periods the supply of volcaniclastic detritus was

167°E 168°E 169°E

Hut Point 78°S Peninsula 166°E

AND-1B 169°E

White Island

165°E

Subaerial volcanic complex Volcanic centers after Wilson Black 168°E et al., 2007a. Glaci-volcaniclastic sediments Island after Wilson et al., 2007a. 20 Km

165°E 166°E 167°E

Figure 5. Close-up from Figure 1, illustrating the position of volcanic centers and glacial-volcaniclastic sediments relative to AND-1B core site.

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reduced, whereas benthic biologic activity (bioturbation) and the deposition of epiclastic and hemipelagic sediments was favored. A represen- LSU 5B tation of the depositional system is schematized in Figure 6. (586.45-688.92 mbsf) Dry Valleys DISCUSSION Brown Peninsula

Temporal Evolution of the Volcanic Black McMurdo Island Sound Complex in LSU 5 ETC ETC ETC ETC A well-constrained chronology has been VTC VTC developed for the AND-1B core from a com- White 40 39 Island EFD,VD,LF bination of Ar/ Ar ages, microfossil biostra- AND-1B tigraphy, and correlation of magnetic polarity stratigraphy with the geomagnetic polarity time scale on primary volcanic deposits for the upper Ross Sea ~600 m of the AND-1B core (Wilson et al., 2007c; Naish et al., 2008). The age model con- siders the presence of several hiatuses, changes S in accumulation rate between hiatuses, and the presence of several erosion surfaces. Despite LSU 5A the paucity of volcanic material suitable for (688.92-714.80 mbsf) radiometric dating, the recognition of four well- Dry Valleys deﬁ ned time stratigraphic windows into the his- Brown tory and dynamics of the Ross Ice Shelf (Naish Peninsula et al., 2008, 2009) has resulted. Ages of ca. 4.6– Black McMurdo 4.9 Ma and ca. 3.2–3.6 Ma were indicated for Island Sound ETC 460–600 mbsf and 280–440 mbsf, respectively, ETC ETC VTC ETC whereas ages of ca. 2.35–2.75 Ma and ca. 0.1– VTC 0.78 Ma were attributed to 150–253 mbsf and White VTC 20–80- mbsf (Naish et al., 2008, 2009). The chro- Island EFD nology of LSU 5 is less robust below 586 mbsf AND-1B due to the absence of biostratigraphic data and the fact that correlation with the geomagnetic Ross Sea polarity time scale is poorly constrained. The Miocene-Pliocene boundary should

occur within a series of hiatuses in LSU 5 S between 615.50 and 635.00 mbsf (~620 mbsf) that account for ~1 m.y. of time (Wilson et al., LSU 5A 2007c). A 40Ar/39Ar age (6.48 ± 0.13 Ma) on the basaltic lava fl ow sampled at 648 mbsf indicates (714.80-759.32 mbsf) a Late Miocene age for this interval of the core. Dry Valleys The only chronostratigraphic data available Brown below 700 mbsf are some 40Ar/39Ar ages of vol- Peninsula canic clasts affording maximum depositional Black McMurdo Island Sound ages of 9.41 Ma at 796.53 mbsf, 8.53 Ma at ETC ETC ETC VTC ETC VTC VTC White Figure 6. Schematic models illustrating the Island AND-1B progressive migration or growth of a volcanic edifi ce close to the coring site. Main eruptive, transport, and depositional processes are Ross Sea also sketched (see text for details); fl ow pat- terns are purely illustrative. VTC— volcanic- rich turbidity current; EFD—eruption-fed S density currents; VD—volcanic diamictites; 20 Km LF—lava fl ows; ETC—epiclastic turbidity currents; mbsf—meters below seafl oor.

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822.78 mbsf, and 13.57 Ma for the base of the Solgevik et al., 2007; Zanon et al., 2008). Simi- mentation rates with submarine outwash and AND-1B drill core (Ross et al., 2007; J. Ross, lar volcanic complexes have also been inferred mass-fl ow deposition. The contact between 2009, personal commun.). Thus lacking any from ancient volcanic sequences like Lookout LSU 6 and LSU 5 represents the onset of a long other biostratigraphic constraints, LSU 5 vol- Bluff, New Zealand (Maicher, 2003), Pahvant period of ice retreat from the AND-1B core site. canism initiated after 8.53 Ma and ceased by Butte, Utah (White, 1996, 2001), and Kangerlu- The retreat is coincident with a rapid reduction 4.9 Ma. Additional, more detailed, clast dating luk sequence, southeast Greenland (Mueller et to zero in outsized clast (dropstone) abundance may refi ne the chronology of the lower half of al., 2000, 2002). of both volcanic and Transantarctic Mountain the core, constraining the very beginning of the Our interpretations of facies associations in basement origin that is observed in LSU 5A volcanic activity recorded in LSU 5. LSU 5 suggest that a single eruption (or erup- (Talarico and Sandroni, 2009). The volcanic Considering the drill-site position, the LSU 5 tive period) started with a high-energy phase record of LSU 5 is unusual in the context of the sequence may be an expression of the currently with the deposition of lapilli tuff and tuff, fol- AND-1B succession in that evidence for inter- eroded and submarine northwesternmost exten- lowed by effusive emission of lava fl ows and ruptions by glaciations is absent. sion of the 7.65 ± 0.69 Ma White Island volca- related volcanic diamictites when the energy or We infer open-water conditions at the time nic complex (Cooper et al., 2007; Wilson et al., gas content decreased. Single eruptive events of the volcanic eruptions documented in LSU 2007a). The general lack of siliciclastic glacial were likely short-lived, with activity commonly 5B. The emergence of a submarine volcano or deposits and biogenic sediments interleaved lasting from days to a few years. Observations at generation of subaqueous pyroclastic jets that with volcanic detritus is consistent with LSU Surtsey and Capelinhos indicate that eruptions break the water surface preclude signifi cant ice 5 representing a short-lived interval. However, lasting several days to a few weeks constructed cover. During terrestrial subglacial eruptions the occurrence of more than one paleomagnetic edifi ces as big as 180 m above the sea level the heat is more or less effi ciently transferred reversal within this LSU places some mini- (>300 m above seafl oor) (Thorarinsson et al., from the erupted magma to the surrounding gla- mum constraints (i.e., hundreds of thousands of 1964; Machado et al., 1962). Analogous to these cier (55% to >80%; Höskuldsson and Sparks, years) on the duration of volcanism (Wilson et observed eruptions, the LSU 5 activity could 1997; Gudmundsson, 2003; Gudmundsson and al., 2007c). have been cyclical, intermittent, and alternat- Cook, 2004; Gudmundsson et al., 2004) while ing with quiescent periods during which erosion warm water derived from ice melting remains Structural Evolution of the Volcanic of primary volcanic deposits and deposition of confi ned in a water-fi lled cavity in the glacier Complex in LSU 5 epiclastic turbidites occurred. The growth of the until it can escape through fractures or perme- volcanic complex may have continued until the able ice layers. If an eruption persists, the sub- The onset of the LSU 5 volcanic sequence emergence of the volcanic complex or until the glacial volcano can break the ice surface and represents a signifi cant shift from a glacier- establishment of a very shallow water setting, as emerge, melting as much as several hundreds of dominated to a volcano-dominated geological testifi ed by high-temperature oxidization prod- meters of ice (Höskuldsson and Sparks, 1997). system. Lithostratigraphic unit 6 (LSU 6), which ucts that are abundant in the sequence. By contrast, in submarine eruptions the heat underlies LSU 5 and extends to ~1225 mbsf, In the topmost part of sequence LSU 5B, a transfer to the overlying ice is likely much less contains no pure volcanic horizons (Krissek et series of hiatuses occur mainly within volcanic- effi cient since a signifi cant part of magma heat al., 2007). The activation of a new source of rich epiclastic deposits (wavy dashed red line is lost during the interaction with seawater and volcaniclastic material is indicated by the con- in Fig. 2), indicating that volcanic activity was the water eventually produced by ice melting stant supply of very fi ne primary pyroclasts that repeatedly interrupted by variably long peri- quickly cools and moves away. The presence were remobilized, reworked, and form the vol- ods of quiescence. During quiescence, erosion of a thick ice shelf would likely prevent the canic fraction of the distal epiclastic turbidites of volcanic deposits and epiclastic deposition emergence of the volcano and favor exclusively recovered from the lowermost part of sequence occurred. The duration of these periods of subaqueous activity. Thus a deglaciated condi- LSU 5A. The fi rst evidence of a nearby growing reduced volcanic activity cannot be exactly con- tion above the drill site seems more realistic volcanic complex in the McMurdo Sound basin strained since biostratigraphic data are absent for the primary volcanic sequences of LSU 5B. and in LSU 5 is the eruption-fed aqueous den- in this part of the core and correlation with The lack of dropstones and glacial diamictite in sity current deposits that are interlayered with the geomagnetic polarity time scale is poorly LSU 5 supports this interpretation. laminated volcanic claystone and siltstone in the constrained. However, an overall duration of These considerations seem to be in agree- uppermost part of sequence LSU 5A. ~1 m.y. of time was reconstructed on the basis ment with data on marine oxygen isotope (δ18O) Sequence LSU 5B may have resulted from of stratigraphic considerations and geochrono- records from diatomite deposits overlying LSU an increase of eruptive energy due to higher logic data (Wilson et al., 2007c). 5 that indicate higher global sea surface tem- magma supply or gas content, and/or a shift peratures relative to today, with open-water of the eruptive activity closer to the drill site. Paleoclimatic and Paleoenvironmental conditions or thin ice cover in the Ross Embay- Eruptions may have been produced by very Implications ment following the deposition of the volcanic complex edifi ces made up of several monoge- sequence (Naish et al., 2009). The volcanic netic and closely spaced and often overlapping Facies analysis and interpretation of LSU activity may have continued until the emergence cones; similar structures were produced dur- 5 provide important data for paleoclimate and of the volcanic complex, as testifi ed by abun- ing recent basaltic eruption at many locations, paleoenvironment reconstructions. Sequence dant oxidized volcanic fragments both in tuff including Surtsey and its associated satellites LSU 5A is bounded at its base by deposits that and in volcanic diamictite deposits. (Thorarinsson, 1964; Lorenz, 1974; Jakobsson indicate subglacial conditions with oscillation The hypothesis of an emerging volcano and Moore, 1982; Kokelaar and Durant, 1983), of the grounding line and variable infl uence of seems at fi rst appearance to be unrealistic in Falcon Island, Tonga (Hoffmeister et al., 1929), icebergs in sediment delivery (LSU 6 and LSU light of the current basin bathymetry and con- and Capelinhos or São Roque volcano, Azores 7). According to Krissek et al. (2007), these sidering an eruptive style as that inferred by (Machado et al., 1962; Cole et al., 1996, 2001; oscillations were accompanied by high sedi- the sequence interpretation (Surtseyan style).

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Esser, R.P., Kyle, P.R., and McIntosh, W.C., 2004, 40Ar/39Ar Today, a volcano erupting on the seafl oor close of the LSU 5 volcaniclastic sequence preclude dating of the eruptive history of Mt. Erebus, Antarc- to the AND-1B would need to grow vertically any interaction with grounded or ungrounded tica: Volcano evolution: Bulletin of Volcanology, v. 66, ~1000 m to be in shallow water or an emergent ice, indicating prevalent open water conditions p. 671–686, doi: 10.1007/s00445-004-0354-x. Fargo, A.J., McIntosh, W.C., Dunbar, N.W., and Wilch, environment. However, the present basin con- (or at maximum seasonal sea ice). T.I., 2008, 40Ar/39Ar geochronology of Minna Bluff, fi guration is the result of the loading of the crust Antarctica: Timing of Mid-Miocene glacial erosional ACKNOWLEDGMENTS events within the Ross Embayment: Eos (Transactions, by the Ross Island volcanic pile that produced American Geophysical Union), v. 89, Fall meeting ~1 km of subsidence beneath Ross Island and supplement, abs. V13C-2127. The ANDRILL project is a multinational collabo- the development of an enclosing moat (Stern et Fiske, R.S., 1963, Subaqueous pyroclastic fl ows in the ration between the Antarctic programs of Germany, Ohanapecosh Formation, Washington: Geological al., 1991) superimposed on the regional pattern Italy, New Zealand, and the United States. Antarctica Society of America Bulletin, v. 74, p. 391–406, doi: of accommodation space created by late Ceno- New Zealand is the project operator and developed 10.1130/0016-7606(1963)74[391:SPFITO]2.0.CO;2. zoic rifting (Naish et al. 2007). At the time that the drilling system in collaboration with A. Pyne. Fiske, R.S., Cashman, K.V., Shibata, A., and Watanabe, K., 1998, Tephra dispersal from Myojinsho, Japan, during LSU 5 deposition began, the Ross Island vol- Antarctica New Zealand supported the drilling team at Scott Base; Raytheon Polar Services Corporation its shallow submarine eruption of 1952–1953: Bulle- canic complex was most likely not present, as tin of Volcanology, v. 59, p. 262–275, doi: 10.1007/ supported the science team at McMurdo Station s004450050190. the oldest outcrops at Mount Bird are 4.6 Ma and the Crary Science and Engineering Laboratory. Gudmundsson, M.T., 2003, Melting of ice by magma-ice- (Wright and Kyle, 1990a), and Mount Erebus, The ANDRILL Science Management Offi ce at the water interactions during subglacial eruptions as an composing the bulk of the island, is younger University of Nebraska-Lincoln provided science indicator of heat transfer in subaqueous eruptions, in planning and operational support. The scientifi c White, J.D.L, et al., eds., Explosive subaqueous vol- than 1.3 Ma. If Ross Island were absent during studies are jointly supported by the U.S. National canism: American Geophysical Union Geophysical the LSU 5 deposition, then only regional sub- Science Foundation, the New Zealand Foundation for Monograph 140, p. 61–72. sidence related to the late Cenozoic rifting was Research Science and Technology, the Italian Ant- Gudmundsson, M.T., and Cook, K., 2004, The 1918 eruption of Katla, Iceland: Magma fl ow rates, ice melting responsible for the basin confi guration. Remov- arctic Research Programme, the German Research rates and generation of the greatest jökulhlaup of the ing the ~1 km of subsidence due to Ross Island Foundation, and the Alfred Wegener Institute for 20th century: General Assembly 2004, International Polar and Marine Research. We are grateful for the Association of Volcanology and Chemistry of the loading results in a shallow water or emerged detailed core logging by the McMurdo Ice Shelf Earth’s Interior, Pucoń, Chile, 14–19 November, setting for the volcanic complex that produced Sedimentology Team and for helpful discussions Abstract s11b_pth_135. LSU 5B, which is consistent with the presence with Phil Kyle during the drilling. We thank co-chiefs Gudmundsson, M.T., Sigmundsson, F., Björnsson, H., and Högnadóttir, T., 2004, The 1996 eruption at Gjálp, Vat- of oxidized volcanic fragments in the core. (Tim Naish, Ross Powell) and staff scientist Richard Levy for coordinating efforts, and A. Cavallo (Istituto najökull ice cap, Iceland: Effi ciency of heat transfer, ice deformation and subglacial water pressure: Bul- Nazionale di Geofi sica e Vulcanologia, Rome) for letin of Volcanology, v. 66, p. 46–65, doi: 10.1007/ CONCLUSIONS assistance in scanning electron microscope observa- s00445-003-0295-9. tions. Di Roberto benefi ted from a Programme for Hoffmeister, J.E., Ladd, H.S., and Ailing, H.L., 1929, Falcon Our new detailed volcano-stratigraphic data Antarctic Research post-doctoral fellowship. Island: American Journal of Science, v. 18, p. 461–471. Höskuldsson, A., and Sparks, R.S.J., 1997, Thermodynam- and interpretations of the thick and very complex REFERENCES CITED ics and fl uid dynamics of effusive sub-glacial erup- volcaniclastic sequence in the AND-1B core tions: Bulletin of Volcanology, v. 59, p. 219–230, doi: provide new insights into the volcanic history 10.1007/s004450050187. Allen, S.R., Hayward, B.W., and Mathews, E., 2007, A Jakobsson, S.P., and Moore, J.G., 1982, The Surtsey and evolution of the Erebus Volcanic Province facies model for a submarine volcaniclastic apron: The Research Drilling Project of 1979: Surtsey Research during the Late Miocene. This study presents Miocene Manukau Subgroup, New Zealand: Geologi- Progress Report, v. 9, p. 76–93. cal Society of America Bulletin, v. 119, p. 725–742, Kokelaar, B.P., 1983, The mechanism of Surtseyan volca- a record and a model of submarine volcanism doi: 10.1130/B26066.1. nism: Geological Society of London Journal, v. 140, in the intracontinental rift setting of the Ross Armienti, P., Tamponi, M., and Pompilio, M., 2001, Sand p. 939–944, doi: 10.1144/gsjgs.140.6.0939. Embayment. The study of the LSU 5 volcanic provenance from major and trace element analyses Kokelaar, B.P., and Busby, C., 1992, Subaqueous explosive of bulk rock and sand grains from CRP-2/2A, Vic- eruption and welding of pyroclastic deposits: Science, sequence enabled us to identify mechanisms of toria Land Basin, Antarctica: Terra Antarctica, v. 8, v. 257, p. 196–201, doi: 10.1126/science.257.5067.196. transport and deposition of volcaniclastic detri- p. 569–582. Kokelaar, B.P., and Durant, G.P., 1983, The submarine erup- tus during a time of minimal ice cover followed Armstrong, R.L., 1978, K-Ar dating: Late Cenozoic tion and erosion of Surtla (Surtsey), Iceland: Journal of McMurdo Volcanic Group and Dry Valley glacial his- Volcanology and Geothermal Research, v. 19, p. 239– by the development of a new volcanic complex tory, Victoria Land, Antarctica: New Zealand Journal 246, doi: 10.1016/0377-0273(83)90112-9. prior to 6.48 Ma. This volcanic complex began of Geology and Geophysics, v. 21, p. 685–698. Krissek, L., Browne, G., Carter, L., Cowan, E., Dunbar, Associated Press, 2009, Tongan inspectors head to undersea G., McKay, R., Naish, T., Powell, R., Reed, J., Wilch, erupting in submarine conditions and continued volcano: http://www.physorg.com/news156663985.html. T., and The ANDRILL-MIS Science Team, 2007, until the volcanic complex summit grew into Cas, R.A.F., and Wright, J.V., 1987, Volcanic successions: Sedimentology and stratigraphy of the AND-1B Core, a very shallow water environment. According London, Allen and Unwin, 528 p. ANDRILL McMurdo Ice Shelf Project, Antarctica: Cashman, K.V., and Fiske, R.S., 1991, Fallout of pyroclas- Terra Antartica, v. 14, no. 3, p. 185–222. to our interpretation, eruptive dynamics were tic debris from submarine volcanic eruptions: Science, Kyle, P.R., 1977, Mineralogy and glass chemistry of recent similar to those characterizing recent shallow- v. 253, p. 275–280, doi: 10.1126/science.253.5017.275. volcanic ejecta from Mt. Erebus, Ross Island, Antarc- water basaltic eruptions that have been observed Cole, P.D., Guest, J.E., and Duncan, A.M., 1996, Capelin- tica: New Zealand Journal of Geology and Geophysics, hos: The disappearing volcano: Geology Today, v. 12, v. 20, p. 1123–1146. in several geologic settings. The sequence was p. 68–72, doi: 10.1046/j.1365-2451.1996.00010.x. Kyle, P.R., 1981, Glacial history of the McMurdo Sound probably deposited during repeated short-lived Cole, P.D., Guest, J.E., Duncan, A., and Pacheco, J.M., area, as indicated by the distribution and nature of 2001, Capelinhos 1957–1958, Faial, Azores: Depos- McMurdo volcanic rocks in the Dry Valley Drilling eruptive events; each event likely started with a its formed by an emergent Surtseyan eruption: Bul- Project, in McGinnis, L.D., ed., Dry Valley Drill- high-energy phase during which the deposition letin of Volcanology, v. 63, p. 204–220, doi: 10.1007/ ing Project: American Geophysical Union Antarctic of lapilli tuff and tuff occurred, followed by effu- s004450100136. Research Series, v. 33, p. 403–412. Cooper, A.F., Adam, L.J., Coulter, R.F., Eby, G.N., and Kyle, P.R., 1990, McMurdo volcanic group—Western Ross sive emission of lava fl ows and related volca- McIntosh, W.C., 2007, Geology, geochronology and Embayment, in LeMasurier, W.E., and Thomson, nic diamictites and other gravity fl ow deposits. geochemistry of a basanitic volcano, White Island, J.W., eds., Volcanoes of the Antarctic plate and south- More generally, the analysis of the LSU 5 vol- Ross Sea, Antarctica: Journal of Volcanology and Geo- ern oceans: American Geophysical Union Antarctic thermal Research, v. 165, p. 189–216, doi: 10.1016/ Research Series, v. 48, p. 19–25. canic sequence in the AND-1B core furnishes j.jvolgeores.2007.06.003. Kyle, P.R., and Muncy, H.L., 1989, Geology and geochro- a new and consistent data set for the study of Doucet, P., Mueller, W., and Chartrand, F., 1994, Archean, nology of McMurdo Volcanic Group rocks in the deepwater, volcanic eruptive products associated with vicinity of Lake Morning, McMurdo Sound, Antarc- basaltic submarine volcanic activity and its the Coniagas massive deposit, Quebec, Canada: Cana- tica: Antarctic Science, v. 1, p. 345–350, doi: 10.1017/ products. The facies analysis and interpretation dian Journal of Earth Sciences, v. 31, p. 1569–1584. S0954102089000520.

Geosphere, October 2010 535

Downloaded from http://pubs.geoscienceworld.org/gsa/geosphere/article-pdf/6/5/524/3341064/524.pdf by guest on 25 September 2021 Di Roberto et al.

Kyle, P.R., Moore, J.A., and Thirwall, M.F., 1992, Petro- Naish, T.R., Powell, R.D., Barrett, P.J., Levy, R.H., Henry, Thorarinsson, S., 1964, Surtsey. The new island in the North logic evolution of anorthoclase phonolite lavas at Mt. S., Wilson, G.S., Krissek, L.A., Niessen, F., Pompilio, Atlantic: New York, Viking Press, 63 p. Erebus, Ross Island, Antarctica: Journal of Petrology, M., Ross, J., Scherer, R., Talarico, F., Pyne, A., and Walker, P.L., 1973, Lengths of lava fl ows: Royal Society of v. 33, p. 849–875. the ANDRILL-MIS Science Team, 2008, Late Neo- London Philosophical Transactions, v. 274, p. 107–118. Lorenz, V., 1974, Studies of the Surtsey tephra deposits: gene climate history of the Ross Embayment from the White, J.D.L., 1996, Pre-emergent construction of a Surtsey Research Progress Report, v. 7, p. 72–79. AND-1B drill core: Culmination of three decades of lacustrine basaltic volcano, Pahvant Butte: Bulle- Machado, F., Parsons, W.H., Richards, A.F., and Mulford, Antarctic margin drilling, in Cooper, A.K., ed., Antarc- tin of Volcanology, v. 58, p. 249–262, doi: 10.1007/ J.W., 1962, Capelinhos eruption of Fayal volcano, tica: A keystone in a changing world, Proceedings of s004450050138. Azores, 1957–1958: Journal of Geophysical Research, the 10th International Symposium on Antarctic Earth White, J.D.L., 2000, Subaqueous eruption-fed density cur- v. 67, p. 3519–3529, doi: 10.1029/JZ067i009p03519. Sciences: Washington, D.C., National Academies rents and their deposits: Precambrian Research, v. 101, Maicher, D., 2003, A cluster of Surtseyan volcanoes at Press, p. 71–82. p. 87–109, doi: 10.1016/S0301-9268(99)00096-0. Lookout Bluff, North Otago, New Zealand: Aspects of Naish, T., and 55 others, 2009, Obliquity-paced Pliocene White, J.D.L., 2001, Eruption and reshaping of Pahvant edifi ce spacing and time, in White, J.D.L, et al., eds., West Antarctic Ice Sheet oscillations: Nature, v. 458, Butte volcano in Pleistocene Lake Bonneville, in Explosive subaqueous volcanism: American Geophysi- p. 322–328, doi: 10.1038/nature07867. White, J.D.L., and Riggs, N.R., eds., Volcaniclastic cal Union Geophysical Monograph 140, p. 167–178. Pompilio, M., Dunbar, N., Gebhardt, A.C., Helling, D., sedimentation in lacustrine settings: International Martin, U., and White, J.D.L., 2001, Depositional and erup- Kuhn, G., Kyle, P., McKay, R., Talarico, F., Tulaczyk, Association of Sedimentologists Special Publication tive mechanisms of density current deposits from a S., Vogel, S., Wilch T., and The ANDRILL-MIS Sci- 30, p. 61–80. submarine vent at the Otago Peninsula, New Zealand, ence Team, 2007, Petrology and geochemistry of the White, J.D.L., and Houghton, B.F., 1999, Surtseyan and in McCaffrey, W.D., et al., eds., Particulate gravity cur- AND-1B Core, ANDRILL McMurdo Ice Shelf Proj- related eruptions, in Sigurdsson, H., et al., eds., Ency- rents: International Association of Sedimentologists ect, Antarctica: Terra Antartica, v. 14, p. 255–288. clopedia of volcanoes: San Diego, Academic Press, Special Publication 31, p. 245–261. Rao, A., Chen, Y., Lee, S., Leigh, J., Johnson, A., and p. 495–512. Martin, U., Cooper, A.F., and Dunlap, W.J., 2009, Geochro- Renambot, L., 2006, Corelyzer: Scalable geologic core White, J.D.L., and Houghton, B.F., 2006, Primary volcani- nology of Mount Morning, Antarctica: Two-phase evo- visualization using OSX, Java and OpenGL: Apple’s clastic rocks: Geology, v. 34, p. 677–680, doi: 10.1130/ lution of a long-lived trachyte-basanite-phonolite erup- Worldwide Developers Conference 2006: Electronic G22346.1. tive center: Bulletin of Volcanology, v. 72, p. 357–371, Visualization Laboratory, http://www.evl.uic.edu/ Wilch, T.I., McIntosh, W.C., Panter, K.S., Dunbar, N.W., doi: 10.1007/s00445-009-0319-1. core.php?mod=4&type=3&indi=310. Smellie, J.L., Fargo, A., Scanlan, M., Zimmerer, McIntosh, W.C., 2001, 40Ar/39Ar geochronology of tephra Ross, J., McIntosh, W.C., Dunbar, N.W., and ANDRILL-MIS M.J., Ross, J., and Bosket, M.E., 2008, Volcanic and and volcanic clasts in CRP-2A, Victoria Land Basin, Science Team Preliminary, 2007, 40Ar/39Ar results glacial geology of the Miocene Minna Bluff Volcanic Antarctica, in Barrett, P.J., and Ricci, C.A., eds., Stud- from the AND-1B core, in Cooper, A.K., et al., eds., Complex, Antarctica: Eos (Transactions, American ies from the Cape Roberts Project, Ross Sea, Antarc- Antarctica: A keystone in a changing world: Online Pro- Geophysical Union), v. 89, Fall Meeting supplement, tica, Scientifi c report of CRP-2/2A: Terra Antartica, ceedings of the 10th ISAES X: U.S. Geological Survey abs.V11F–06. v. 7, p. 621–630. Open-File Report 1047, extended abs. 093. Wilson, G., Damaske, D., Moeller, H.D., Tinto, K., and McKay, R., Browne, G., Carter, L., Cowan, E., Dunbar, G., Skilling, I.P., 1994, Evolution of an englacial volcano— Jordan, T., 2007a, The geological evolution of south- Krissek, L., Naish, T., Powell, R., Reed, J., Talarico, F., Brown Bluff, Antarctica: Bulletin of Volcanology, ern McMurdo Sound—New evidence from a high- and Wilch, T., 2009, The stratigraphic signature of late v. 56, p. 573–591, doi: 10.1007/BF00302837. resolution aeromagnetic survey: Geophysical Jour- Cenozoic oscillations of the Antarctic Ice Sheet in the Ross Smellie, J.L., 1999, Subglacial eruptions, in Sigurdsson, nal International, v. 170, p. 93–100, doi: 10.1111/ Embayment, Antarctica: Geological Society of America H., et al., eds., Encyclopedia of volcanoes: San Diego, j.1365-246X.2007.03395.x. Bulletin, v. 121, p. 1537–1561, doi: 10.1130/B26540.1. Academic Press, p. 403–418. Wilson, G., Florindo, F., Sagnotti, L., Ohneiser, C., and the Mueller, W.U., 2003, A subaqueous eruption model for Smellie, J.L., and Hole, M.J., 1997, Products and processes ANDRILL-MIS Science Team, 2007b, Paleomag- shallow-water, small volume eruptions: Evidence from in Pliocene-recent, subaqueous to emergent volcanism netism of the AND-1B Core, ANDRILL McMurdo two Precambrian examples, in White, J.D.L, et al., eds., in the Antarctic Peninsula: Examples of englacial Surt- Ice Shelf Project, Antarctica: Terra Antartica, v. 14, Explosive subaqueous volcanism: American Geophysi- seyan volcano construction: Bulletin of Volcanology, p. 289–296. cal Union Geophysical Monograph 140, p. 189–203. v. 58, p. 628–646, doi: 10.1007/s004450050167. Wilson, G., 20 others, and the ANDRILL-MIS Science Mueller, W.U., and White, J.D.L., 1992, Felsic fi re-fountain- Solgevik, H., Mattsson, H.B., and Hermelin, O., 2007, Team, 2007c, Preliminary integrated chronostratigra- ing beneath Archean seas: Pyroclastic deposits of the Growth of an emergent tuff cone: Fragmentation and phy of the AND-1B Core, Andrill McMurdo ice shelf 2730 MA Hunter Mine Group, Quebec, Canada: Jour- depositional processes recorded in the Capelas tuff project, Antarctica: Terra Antartica, v. 14, p. 297–316. nal of Volcanology and Geothermal Research, v. 54, cone, São Miguel, Azores: Journal of Volcanology Wright, A.C., and Kyle, P.R.A., 1990a, Mount Bird, in p. 117–134, doi: 10.1016/0377-0273(92)90118-W. and Geothermal Research, v. 159, p. 246–266, doi: LeMasurier, W.E., and Thomson, J.W., eds., Volcanoes Mueller, W.U., Garde, A.A., and Stendal, H., 2000, Shallow- 10.1016/j.jvolgeores.2006.06.020. of the Antarctic plate and southern oceans: American water, eruption-fed, mafi c pyroclastic deposits along Song, S.R., and Lo, H.J., 2002, Lithofacies of volcanic Geophysical Union Antarctic Research Series, v. 48, a Paleoproterozoic coastline: Kangerluluk volcano- rocks in the central Coastal Range, eastern Taiwan: p. 97–98. sedimentary sequence, southeast Greenland: Precam- Implications for island arc evolution: Journal of Wright, A.C., and Kyle, P.R.A., 1990b, Mount Terror, in brian Research, v. 101, p. 163–192, doi: 10.1016/ Asian Earth Sciences, v. 21, p. 23–38, doi: 10.1016/ LeMasurier, W.E., and Thomson, J.W., eds., Volcanoes S0301-9268(99)00087-X. S1367-9120(02)00003-2. of the Antarctic plate and southern oceans: American Mueller, W.U., Dostal, J., and Stendal, H., 2002, Inferred Stern, T.A., Davey, F.J., and Delisle, G., 1991, Lithospheric Geophysical Union Antarctic Research Series, v. 48, Palaeoproterozoic arc rifting along a consuming plate fl exure induced by the load of the Ross Archipelago, p. 99–102. margin: Insights from the stratigraphy, volcanology southern Victoria Land, Antarctica, in Thomson, Zanon, V., Pacheco, J., and Pimentel, A., 2008, Growth and geochemistry of the Kangerluluk sequence, south- M.R.A., et al., eds., Geological evolution of Antarctica: and evolution of an emergent tuff cone: Consider- east Greenland: International Journal of Earth Sci- Cambridge, Cambridge University Press, p. 323–328. ations from structural geology, geomorphology and ences, v. 91, p. 209–230, doi: 10.1007/s005310100211. Stix, J., and Gorton, M.P., 1989, Subaqueous volcaniclas- facies analysis of São Roque volcano, São Miguel Naish, T.R., and 16 others, 2006, ANDRILL McMurdo tic rocks of the Confederation lake area, northwestern (Azores): Journal of Volcanology and Geother- Ice Shelf Project Scientifi c Prospectus: Science Man- Ontario: Discrimination between pyroclastic and epi- mal Research, v. 180, p. 277–291, doi: 10.1016/ agement Offi ce, University of Nebraska-Lincoln, clastic emplacement: Ontario Geological Survey Mis- j.jvolgeores.2008.09.018. ANDRILL Contribution 4, p. 1–18. cellaneous Paper, v. 143, p. 83–93. Naish, T.R., Powell, R.D., Levy, R., Henrys, S., Krissek, L., Talarico, F., and Sandroni, S., 2009, Provenance signa- Niessen, F., Pompilio, M., Scherer, R., Wilson, G., and tures of the Antarctic Ice Sheets in the Ross Embay- The ANDRILL-MIS Science Team, 2007, Synthesis of ment during the Late Miocene to Early Pliocene: The the Initial Scientifi c Results of the MIS Project (AND- ANDRILL AND-1B core record: Global and Planetary MANUSCRIPT RECEIVED 31 JULY 2009 1B Core), Victoria Land Basin, Antarctica: Terra Change, v. 69, p. 103–123, doi: 10.1016/j.gloplacha REVISED MANUSCRIPT RECEIVED 12 JANUARY 2010 Antartica, v. 14, p. 317–327. .2009.04.007. MANUSCRIPT ACCEPTED 14 JANUARY 2010

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