Brief descriptions of the cores recovered from 90 holes drilled at 55 sites along Transect EG65 are provided below. A summary of the geographical locations of the drilled sites is given in Table T1. As for Transect EG68, basement recovery was limited by a cover of glaciomarine sediment of variable thickness containing a high proportion of gravel- to boulder-sized clasts. Despite the difficulties in penetrating this cover, basement was unequivocally sampled in 40 holes.
Four holes were drilled at Site SEG21. Drilling in Hole SEG21A penetrated 0.35 m before coring began, and coring terminated at a depth of 0.51 meters below seafloor (mbsf). Unit S-1 is composed of pebble-sized, angular to subrounded diamicton clasts of weathered basalt. Living barnacles were found attached to one of the clasts. Unit I-1 is 10 cm of sparsely clinopyroxene-plagioclase phyric basalt. Hole SEG21B was drilled immediately after Hole SEG21A without emptying the core barrel. Drilling penetrated 0.38 m before coring began, and coring terminated at 0.44 mbsf. Unit S-1 is diamicton clasts composed of pebble-sized, angular to subrounded clasts of basalt and felsic gneiss. Unit C-1 is 8 cm of moderately clinopyroxene phyric basalt resembling Unit I-1 in Hole SEG21A. Drilling in Hole SEG21C penetrated 0.39 m before coring began, and coring terminated at 0.54 mbsf. Only aphyric basaltic gravel (Unit S-1) was recovered from this hole. Drilling in Hole SEG21D penetrated 0.28 m before coring began, and coring terminated at 0.58 mbsf. Unit I-1 is 31 cm of highly fractured sparsely plagioclase-clinopyroxene-olivine phyric and glomerophyric basalt, based on thin section description. The petrographic similarities between cored basalt recovered from Holes SEG21A, SEG21B, and SEG21D indicate that the volcanic basement was sampled from most holes drilled at Site SEG21.
Drilling in Hole SEG22A penetrated 0.29 m before coring began, and coring terminated at 1.15 mbsf. Unit I-1 is 98 cm of intersertal and moderately plagioclase-clinopyroxene phyric and glomerophyric basalt with 5% plagioclase and traces of clinopyroxene phenocrysts. The volcanic basement was sampled at Site SEG22.
Drilling in Hole SEG23A penetrated 0.50 m before coring began, and coring terminated at 0.72 mbsf. Unit C-1 is composed of cored fragments of fine- to medium-grained, sparsely plagioclase-olivine phyric and glomerophyric basalt. The surfaces of many of the fragments are weathered and suggest that the volcanic basement was not directly sampled at Site SEG23.
Drilling in Hole SEG24A penetrated 0.40 m before coring began, and coring terminated at 0.90 mbsf. Unit S-1 is a 4-cm subangular clast of sparsely plagioclase-olivine phyric basaltic gravel. Unit I-1 is 53 cm of amygdaloidal, fractured, and moderately plagioclase-clinopyroxene phyric basalt with 5% plagioclase and 2% clinopyroxene phenocrysts. The volcanic basement was sampled at Site SEG24.
Drilling in Hole SEG25A penetrated 0.50 m before coring began, and coring terminated at 1.09 mbsf. Unit S-1 is 15 cm of subangular, pebble-sized, amygdaloidal basaltic clasts with remaining interstitial reddish brown mud. The volcanic basement was not sampled at Site SEG25.
Drilling in Hole SEG26A penetrated 0.30 m before coring began, and coring terminated at 1.39 mbsf. Unit I-1 is 110 cm of moderately plagioclase-clinopyroxene phyric and glomerophyric basalt with 7% plagioclase and 1% clinopyroxene phenocrysts. The unit is extensively fractured. The volcanic basement was sampled at Site SEG26.
Drilling in Hole SEG27A penetrated 0.18 m before coring began, and coring terminated at 1.22 mbsf when the ship lost position. Unit I-1 is 131 cm of highly plagioclase-clinopyroxene-olivine phyric basalt with 10% plagioclase and equal amounts (4%) of clinopyroxene and olivine phenocrysts. The basalt is highly vesicular and amygdaloidal. Live corals were attached to the top surface (Fig. F5), indicating a sediment-free sea bottom. The volcanic basement was sampled at Site SEG27.
Drilling in Hole SEG28A penetrated 0.29 m before coring began, and coring terminated at 0.85 mbsf. Unit I-1 is 48 cm of vesicular, highly plagioclase-olivine-clinopyroxene phyric basalt with 15% plagioclase phenocrysts and minor amounts of clinopyroxene and olivine. The volcanic basement was sampled at Site SEG28.
Drilling in Hole SEG29A penetrated 1.40 m before coring began, and coring terminated at 2.12 mbsf. Unit S-1 is a 5-cm rounded granite pebble. Unit I-1 is 54 cm of vesicular, moderately plagioclase-olivine-clinopyroxene phyric and glomerophyric basalt with 3% plagioclase and very small amounts of olivine and clinopyroxene phenocrysts. The volcanic basement was sampled at Site SEG29.
Drilling in Hole SEG30A penetrated 0.57 m before coring began, and coring terminated at 1.52 mbsf. Unit S-1 is 23 cm of well-rounded basalt, gneiss, and quartz pebbles. The volcanic basement was not sampled at Site SEG30.
Drilling in Hole SEG31A penetrated 0.66 m before coring began, and coring terminated at 1.36 mbsf. Unit I-1 is 70 cm of vesicular, highly plagioclase-clinopyroxene-olivine phyric and glomerocrystic basalt with 10% plagioclase, 3% clinopyroxene, and 1% olivine phenocrysts. A large 32-cm-long vesicular segregation pipe with sharp but irregular boundaries occurs at the top of the unit (Fig. F6). The volcanic basement was sampled at Site SEG31.
Two holes were drilled at Site SEG32. Drilling in Hole SEG32A penetrated 0.80 m before coring began, and coring terminated at 1.32 mbsf. Unit I-1 is 23 cm of melanocratic hornblende-biotite pegmatite with interstitial oxides believed to represent the Archean basement. The gneiss is composed of hornblende, biotite, quartz, and opaque minerals. Drilling in Hole SEG32B penetrated 0.82 m before coring began, and coring terminated at 1.82 mbsf. Unit S-1 is 23 cm of diamicton clasts including basalt and quartzite. The continental basement was sampled at Site SEG32.
Drilling in Holes SEG33A and SEG34A penetrated to depths of 2.09 and 0.68 mbsf, respectively. No core was recovered from these holes.
Drilling in Hole SEG35A penetrated 1.88 m before coring began, and coring terminated at 3.00 mbsf. Unit S-1 is three subangular to rounded pebbles of basaltic to arkosic rock fragments. The volcanic basement was not sampled at Site SEG35.
Drilling in Hole SEG36A penetrated 0.60 m before coring began, and coring terminated at 0.86 mbsf. Unit I-1 is 25 cm of highly amygdaloidal, moderately olivine-clinopyroxene-plagioclase phyric olivine basalt, with 5% olivine, 3% clinopyroxene, and small amounts of plagioclase phenocrysts. Spherical vesicles are filled with chlorite, albite, and calcite. The groundmass is highly silicified and olivine phenocrysts are completely altered to rusty red iddingsite. This unit is distinctive in terms of both its general appearance and its original phenocryst assemblage of olivine and clinopyroxene. We conclude that the volcanic basement was sampled at Site SEG36.
Drilling in Hole SEG37A penetrated 1.40 m before coring began, and coring terminated at 3.00 mbsf. Unit C-1 is a 7-cm-long cored clast of aphyric basalt, relatively similar to Unit I-1 in Hole SEG36A. Because of the petrographic similarity to Unit I-1 in Hole SEG36A, it is suggested that Unit C-1 represents a locally derived block of the volcanic basement.
Three holes were drilled at Site SEG38. The attempt to drill Hole SEG38A was terminated by an approaching ice flow and no recovery was made. Drilling in Hole SEG38B penetrated 0.91 m before coring began, and coring terminated at 1.88 mbsf. Unit S-1 is 32 cm of diamicton clasts of very variable compositions and sizes, including coarse-grained amphibolites and a 19-cm-long fragment of gray sandstone. The latter consists of subangular and cemented fragments of quartz, mica, feldspar, epidote, and carbon flasers cemented by calcite. Drilling in Hole SEG38C penetrated 1.28 m before coring began, and coring terminated at 1.85 mbsf. Unit S-1 is 7 cm of olivine phyric and aphyric basaltic pebbles. The volcanic basement was not sampled at Site SEG38.
Drilling in Hole SEG39A penetrated 0.60 m before coring began, and coring terminated at 1.19 mbsf. Unit S-1 is 12 cm of subangular to rounded clasts of basalt and sandstone. Some clasts show glacial striations. The volcanic basement was not sampled at Site SEG39.
Drilling in Hole SEG40A penetrated 0.65 m before coring began, and coring terminated at 1.89 mbsf. Unit I-1 is 118 cm of highly olivine phyric olivine basalt. Glacial striations occur on the top surface of Unit I-1. Olivine phenocrysts are completely altered to iddingsite and lizardite. Plagioclase glomerocrysts are recognized in thin section. Amygdules are filled with calcite, chlorite, and quartz. This unit has the distinctive appearance first noted in Unit I-1 at Site SEG36. We conclude that the volcanic basement was sampled at Site SEG40.
Drilling in Hole SEG41A started coring when the drill touched the seafloor, and coring terminated at a depth of 0.42 mbsf. Unit I-1 is 23 cm of amygdaloidal, highly plagioclase-olivine-clinopyroxene phyric olivine basalt with most phenocrysts in glomerocrysts and 8% plagioclase, 2% olivine, and small amounts of clinopyroxene phenocrysts. Live corals and other life forms were found on top pieces and demonstrate the lack of sediment cover at this site. This unit resembles Unit I-1 at Site SEG36. The volcanic basement was sampled at Site SEG41.
Three holes were drilled at Site SEG42. Drilling in Hole SEG42A penetrated 0.58 m before coring began, and coring terminated at 1.14 mbsf. Unit C-1 is 15 cm of fresh, amygdaloidal, highly olivine-clinopyroxene phyric basalt clasts. Drilling in Hole SEG42B penetrated 0.95 m before coring began, and coring terminated at 1.40 mbsf. Unit I-1 is 40 cm of seriate and amygdaloidal, highly olivine -plagioclase phyric basalt with 12% olivine and 10% plagioclase phenocrysts. Vesicles are lined successively with chlorite, quartz, and calcite. The groundmass is highly silicified, and olivine phenocrysts are completely altered to iddingsite. Drilling in Hole SEG42C penetrated 1.39 m before coring began, and coring terminated at 1.91 mbsf. Unit S-1 is 8 cm of mainly basaltic pebbles. Unit I-1 is 40 cm of vesicular and amygdaloidal, highly plagioclase-olivine-clinopyroxene phyric basalt with 7% plagioclase, 6% olivine, and 3% clinopyroxene phenocrysts. The highly olivine-plagioclase phyric units recovered from all holes at Site SEG42 are petrographically similar to the volcanic units first observed at Site SEG36. The volcanic basement was sampled at Site SEG42.
Drilling in Hole SEG43A penetrated 0.62 m before coring began, and coring terminated at 1.12 mbsf. Unit I-1 is 47 cm of vesicular and highly olivine-plagioclase-clinopyroxene phyric basalt with 10% olivine, 9% plagioclase, and 2% clinopyroxene phenocrysts, similar to the volcanic units first observed at Site SEG36. The volcanic basement was sampled at Site SEG43.
Drilling in Hole SEG44A penetrated 0.26 m before coring began, and coring terminated at 0.72 mbsf. Unit I-1 is 46 cm of vesicular, banded, and sparsely olivine phyric olivine basalt. This unit is petrographically similar to the volcanic units first observed at Site SEG36. The volcanic basement was sampled at Site SEG44.
Drilling in Hole SEG45A penetrated 0.48 m before coring began, and coring terminated at 1.12 mbsf. Unit S-1 is 16 cm of diamicton clasts composed of subangular to rounded pebbles of basalt, gneiss, and granite. Unit I-1 is 33 cm of moderately olivine-clinopyroxene-plagioclase phyric and highly amygdaloidal basalt with 4% olivine, 4% clinopyroxene, and 2% plagioclase phenocrysts. It is very highly altered and fractured with a crumbling appearance. This unit is petrographically similar to the volcanic units first observed at Site SEG36. The volcanic basement was sampled at Site SEG45.
Drilling in Hole SEG46A penetrated 0.82 m before coring began, and coring terminated at 0.92 mbsf. Unit S-1 is 22 cm of mostly basaltic pebbles, although some gneiss and granite pebbles are present as well. The volcanic basement was not sampled at Site SEG46.
Drilling in Hole SEG47A penetrated 0.52 m before coring began, and coring terminated at 0.96 mbsf. Unit S-1 is 16 cm of angular to subrounded basaltic and gneissic pebbles. Unit I-1 is 58 cm of fresh, amygdaloidal, sparsely olivine-clinopyroxene phyric basalt. This unit is petrographically similar to the volcanic units first observed at Site SEG36. The volcanic basement was sampled at Site SEG47.
Drilling in Hole SEG48A penetrated 1.90 m before coring began, and coring terminated at 2.11 mbsf. Unit S-1 is 71 cm of diamicton composed of matrix supported muddy sandstone with foraminifers. The sandstone is matrix-supported and poorly sorted with rounded diverse clasts, including ~8% basaltic and other rock fragments. The volcanic basement was not sampled at Site SEG48.
Drilling in Hole SEG49A penetrated 0.79 m before coring began, and coring terminated at 1.46 mbsf. Unit S-1 is 50 cm of diamicton composed of matrix-supported, poorly sorted muddy sandstone with foraminifers and a gravel layer with pebble-sized, subrounded basaltic and gneissic clasts. Unit S-1 is very similar to Unit S-1 in Hole SEG48A. The volcanic basement was not sampled at Site SEG49.
Drilling in Hole SEG50A penetrated 1.66 m before coring began, and coring terminated at 1.77 mbsf. Unit S-1 is 33 cm of diamicton composed of an accumulation of mostly basaltic, pebble-sized, angular to subrounded clasts. The volcanic basement was not sampled at Site SEG50.
Drilling in Hole SEG51A penetrated 0.42 m before coring began, and coring terminated at 0.59 mbsf. Unit I-1 is 52 cm of amygdaloidal, highly fractured, moderately plagioclase-clinopyroxene phyric basalt. This unit may represent flow top rubble. Drilling in Hole SEG51B penetrated 0.41 m before coring began, and coring terminated at 0.56 mbsf. Unit I-1 is 23 cm of moderately olivine-clinopyroxene phyric olivine-basalt with 3% olivine and 2% clinopyroxene phenocrysts. A 1-cm-sized xenolith of olivine and pyroxene was discovered after splitting the core. Drilling in Hole SEG51C penetrated 0.44 m before coring began, and coring terminated at 0.92 mbsf. Unit S-1 is a 22-cm accumulation of mostly basaltic pebble-sized clasts that also include a small foliated gneissic clast. Unit I-1 is 23 cm of vesicular, moderately clinopyroxene-plagioclase phyric basalt with 5% clinopyroxene and 3% plagioclase phenocrysts. It is brecciated, cemented with quartz and calcite, and resembles a flow top. The volcanic basement was sampled at Site SEG51.
Drilling in Hole SEG52A penetrated 0.28 m before coring began, and coring terminated at 0.46 mbsf. Unit S-1 is a 10-cm accumulation of pebble-sized rock fragments including basaltic and gneissic varieties. Unit I-1 is 21 cm of sparsely plagioclase-clinopyroxene phyric and glomerophyric basalt with oxidized fractures. The volcanic basement was sampled at Site SEG52.
Drilling in Hole SEG53A penetrated 0.37 m before coring began, and coring terminated at 0.60 mbsf because of an approaching iceberg. Unit I-1 is 22 cm of amygdaloidal and aphyric basalt. Drilling in Hole SEG53B penetrated 0.36 m before coring began, and coring terminated at 0.72 mbsf. Unit I-1 is 31 cm of amygdaloidal, aphyric basalt that is similar to Unit I-1 of Hole SEG53A. The basalts in both holes are highly altered and fractured and appear angular and subrounded in the core. Because all pieces are petrographically very similar, both units were classified as igneous. The volcanic basement was sampled at Site SEG53.
Drilling in Hole SEG54A penetrated 0.44 m before coring began, and coring terminated at 0.71 mbsf. Unit S-1 is 3 cm of subrounded basaltic pebbles. Unit I-1 is 19 cm of sparsely clinopyroxene-plagioclase-olivine phyric basaltic clasts with 5% clinopyroxene, 2% plagioclase, and 1% olivine phenocrysts. The petrography of Unit I-1 is similar to igneous units in Holes SEG52A, SEG53A, and SEG53B and suggests that the volcanic basement was sampled at Site SEG54. Unit I-1 was classified as an igneous unit despite the lowermost clast in the section being subrounded with weathered, fractured surfaces.
Drilling in Hole SEG55A made no recovery. Drilling in Hole SEG55B penetrated 0.60 m before coring began, and coring terminated at 0.98 mbsf. Unit S-1 is 12 cm of subangular to subrounded pebbles of basaltic, dioritic, and granitic compositions, some with small amounts of adhering mud. Unit I-1 is 20 cm of vesicular and sparsely plagioclase phyric basalt. Drilling in Hole SEG55C penetrated 0.15 m before coring began, and coring terminated at 0.32 mbsf. Unit S-1 is 4 cm of subangular, pebble-sized clasts of basalt and diorite. Unit C-1 is 9 cm of cored basalt clasts consisting of amygdaloidal, moderately plagioclase-clinopyroxene-olivine phyric and glomerophyric basalts. Small inclusions are millimeter sized and fresh and contain olivine and pyroxene. Unit C-1 is very similar to Unit I-1 in Hole SEG55B and is interpreted to be a locally derived basaltic clast. It is concluded that the volcanic basement was sampled at both Holes SEG55B and SEG55C.
Two holes were drilled at Site SEG56. Drilling in Hole SEG56A penetrated 0.30 m before coring began, and coring terminated at 0.71 mbsf. Unit S-1 is 7 cm of diamicton clasts composed of subangular pebbles of basaltic, dioritic, and biotite granitic rocks. Unit I-1 is 28 cm of amygdaloidal, highly plagioclase-olivine-clinopyroxene phyric and glomerophyric olivine basalt with 6% plagioclase, 4% clinopyroxene, and 2% olivine phenocrysts and a trachytic groundmass texture. Drilling in Hole SEG56B penetrated 0.37 m before coring began, and coring terminated at 0.60 mbsf. Unit S-1 is a single subangular pebble of biotite felsic gneiss. Unit C-1 is 14 cm of cored and rounded clasts of amygdaloidal, moderately plagioclase-olivine-clinopyroxene phyric to glomerophyric basalt with trachytic alignment of plagioclase laths in the groundmass. The two basalt units defined at this site are petrographically very similar. The units are also similar to Unit I-1 in Hole SEG57A and probably represent the local volcanic basement.
Drilling in Hole SEG57A penetrated 0.48 m before coring began, and coring terminated at 0.87 mbsf. Unit I-1 is 45 cm of amygdaloidal, moderately plagioclase-olivine-clinopyroxene phyric basalt with 2% plagioclase, 2% olivine, and 1% clinopyroxene phenocrysts. The basalt has a trachytic groundmass. The unit is petrographically very similar to Unit C-1 in Hole SEG56B. The volcanic basement was sampled at Site SEG57.
Drilling in Hole SEG58A penetrated 0.57 m before coring began, and coring terminated at 1.13 mbsf. Unit I-1 is 27 cm of seriate, highly plagioclase-olivine-clinopyroxene phyric and glomerophyric basalt with 8% plagioclase, 4% olivine, and 2% clinopyroxene phenocrysts. The volcanic basement was sampled at Site SEG58.
Both holes drilled at Site SEG59 sampled a thin sediment cover without reaching the volcanic basement. Drilling in Hole SEG59A penetrated 0.40 m before coring began, and coring terminated at 0.80 mbsf. Unit C-1 is 16 cm of subangular, sparsely clinopyroxene-plagioclase phyric basaltic clasts and gneissic clasts. Drilling in Hole SEG59B penetrated 0.32 m before coring began, and coring terminated at 0.32 mbsf. Unit S-1 is 16 cm of sparsely clinopyroxene-plagioclase phyric basaltic and granitic clasts. The volcanic basement was not sampled at Site SEG59.
Drilling in Hole SEG60A penetrated 0.42 m before coring began, and coring terminated at 0.51 mbsf. Unit C-1 is a 3 cm highly plagioclase-olivine phyric basaltic clast. Drilling in Hole SEG60B penetrated 0.35 m before coring began, and coring terminated at 1.35 mbsf. Unit I-1 is 103 cm of amygdaloidal, moderately plagioclase-olivine-clinopyroxene phyric and intersertal basalt with 5% plagioclase, 4% olivine, and 1% clinopyroxene phenocrysts. The uppermost part of Unit I-1 is very vesicular and fractured and may represent a flow top. The volcanic basement was sampled at Site SEG60.
Drilling in Hole SEG61A penetrated 0.36 m before coring began, and coring terminated at 0.82 mbsf. Unit S-1 is a 13-cm-long foliated gneissic clast with various forms of benthic organisms growing on the top weathered surface. Unit I-1 is 62 cm of vesicular, moderately clinopyroxene-olivine phyric basalt. Drilling in Hole SEG61B penetrated 0.30 m before coring began, and coring terminated at 1.67. Unit I-1 is 156 cm of moderately plagioclase-clinopyroxene-olivine phyric basalt with 5% plagioclase, 1% clinopyroxene, and 1% olivine phenocrysts. The volcanic basement was sampled at Site SEG61.
Drilling in Hole SEG62A penetrated 0.42 m before coring began, and coring terminated at 0.94 mbsf. Unit S-1 is 9 cm of subangular basaltic pebbles. Unit I-1 is 30 cm of vesicular, moderately plagioclase-clinopyroxene phyric basalt with 5% plagioclase and 2% clinopyroxene phenocrysts. The volcanic basement was sampled at Site SEG62.
Drilling in Hole SEG63A penetrated 0.80 m before coring began, and coring terminated at 1.01 mbsf. Unit I-1 is 30 cm of vesicular to glomerophyric, moderately plagioclase-olivine-clinopyroxene phyric basalt with rusty-brown weathering and contains 2% plagioclase, 1% olivine, and 1% clinopyroxene phenocrysts. Drilling in Hole SEG63B penetrated 0.48 m before coring began, and coring terminated at 0.91 mbsf. Unit I-1 is 55 cm of basalt very similar to basalt recovered from Unit I-1 in Hole SEG63A. These petrographic similarities suggest that Unit I-1 in Hole SEG63A may represent the local volcanic basement similar to basement sampled by Unit I-1 in Hole SEG63B. The volcanic basement was sampled at Site SEG63.
Drilling in Hole SEG64A penetrated 0.48 m before coring began, and coring terminated at 0.65 mbsf. Unit S-1 is 17 cm of subangular to rounded clasts consisting of basalt, granite, and sandstone. Drilling in Hole SEG64B penetrated 0.30 m before coring began, and coring terminated at 0.87 mbsf. Unit C-1 is an 8-cm-long core of a moderately plagioclase-clinopyroxene phyric basaltic boulder with a weathered and rounded lower surface. The volcanic basement was not sampled at Site SEG64.
Drilling in Hole SEG65A penetrated 0.40 m before coring began, and coring terminated at 0.68 mbsf. Unit S-1 is 4 cm long and composed of two pebble-sized clasts of granite and basalt. Unit I-1 is 27 cm of amygdaloidal, moderately olivine-clinopyroxene-plagioclase phyric basalt with 5% olivine, 3% clinopyroxene, and 2% olivine phenocrysts. Drilling in Hole SEG65B penetrated 0.25 m before coring began, and coring terminated at 0.57 mbsf. Unit S-1 is 4 cm of small, pebble-sized basaltic and gneissic clasts and a ~2.5-cm-long unspecified snail shell. Unit I-1 is 26 cm of moderately olivine-clinopyroxene-plagioclase phyric and glomerophyric basalt. The volcanic basement was sampled at Site SEG65.
Drilling in Hole SEG66A penetrated 0.30 m before coring began, and coring terminated at 0.60 mbsf. Unit S-1 is 16 cm of subangular, moderately, plagioclase-clinopyroxene phyric basaltic pebbles of nearly identical petrographic characteristics. The volcanic basement was not sampled at Site SEG66.
The attempt to drill Hole SEG73A terminated at 1.13 mbsf when the ship lost positioning. Drilling in Hole SEG73B stepped rapidly to a full penetration depth of 3.00 mbsf. Unit S-1 is 14 cm of rounded to subangular diamicton clasts with basaltic and gneissic compositions. The volcanic basement was not sampled at SEG73.
Drilling in Hole SEG74A penetrated 1.60 m before coring began, and coring terminated at 1.93 mbsf. Unit S-1 is 4 cm of sparsely plagioclase-clinopyroxene phyric basaltic gravel. Unit I-1 is 27 cm of massive, nonvesicular, highly olivine phyric basalt with strong orange coloration from weathering. Almost all phenocrysts are altered to red clay. Fractures occur frequently and are filled by red alteration clay and occasionally lined by a black mineral. This unit is petrographically similar to the distinctive volcanic units first observed at Site SEG36. Drilling in Hole SEG74B penetrated 1.10 m before coring began, and coring terminated at 1.20 mbsf. Unit S-1 contains subangular to subrounded pebbles with a range of compositions including basalt, gneiss, and metamorphic quartzite. Two clasts have a composition similar to Unit I-1 in Hole SEG74A. Hole SEG74C was drilled 15 m northwest offset from the original target. Drilling penetrated 0.43 m before coring began, and coring terminated at 0.51 mbsf without core recovery. Hole SEG74D was drilled at the same location as Hole SEG74C. Drilling penetrated 0.71 m before coring began, and coring terminated at 1.01 mbsf. Unit S-1 is 17 cm long and composed of 2- to 4-cm-sized pebbles of basalt and sandstone. The sandstone consists mainly of quartz and mica. The basaltic pebbles are highly weathered, red-stained, and moderately olivine phyric (~10% olivine). Olivine phenocrysts are ~2 mm in diameter, and all are altered to a green mineral and iddingsite. Amygdules are ~1 mm in diameter, ellipsoidal, and filled with green minerals that have red stains around the rims. The basaltic pebbles are similar to Unit I-1 in Hole SEG74A. Hole SEG74E was drilled at the same location as Holes SEG74C and SEG74D and penetrated 0.87 m before coring began. Coring terminated at 2.4 mbsf. Unit S-1 is composed of <1-cm-sized basaltic gravel with a composition similar to that of Unit I-1 in Hole SEG74A. Unit C-1 is a 7-cm-long cored clast of moderately plagioclase-olivine-clinopyroxene phyric basalt with 5% plagioclase, 2% olivine, and 1% clinopyroxene phenocrysts. Plagioclase and clinopyroxene form glomerocrysts, with olivine occasionally composing part of the glomerocrystic assemblage. Vesicles are ~0.5–2 mm in diameter and most commonly unfilled, although some have white zeolite fillings. Small vesicles occur in irregular swarms. Unit C-1 is different from Unit I-1 in Hole SEG74A. The volcanic basement was sampled at Site SEG74.
Drilling in Hole SEG75A penetrated 1.68 m before coring began, and coring terminated at 1.94 mbsf. Unit S-1 is 22 cm of basaltic gravel consisting of highly olivine-clinopyroxene phyric basalt similar to the underlying Unit C-1. Unit C-1 is a 4-cm-long cored clast of highly olivine-clinopyroxene phyric (10% olivine and 1% clinopyroxene), amygdaloidal, very highly altered basalt. All olivine phenocrysts have been replaced by green clays and iddingsite. Amygdules are most often lined with a dark green mineral, possibly epidote, and filled with clays, carbonate, and zeolites. The high content of amygdules indicate that Unit C-1 represents a pahoehoe flow top. Drilling in Hole SEG75B penetrated 1.68 m before coring began, and coring terminated at 1.93 mbsf. Unit S-1 is a 3-cm-long clast of moderately olivine phyric basalt, different in composition from the underlying Unit I-1. Unit I-1 is 27 cm of amygdaloidal, highly olivine-clinopyroxene phyric (10% olivine and 1% clinopyroxene), very highly altered basalt. All olivine phenocrysts are altered to green clays and iddingsite. Amygdules are most often lined with a dark green mineral, possibly epidote, and filled with pale green to white clays, carbonate, and zeolites. Drilling in Hole SEG75C penetrated 1.40 m before coring began, and coring terminated at 1.92 mbsf. Unit S-1 is 3 cm of basaltic gravel with a composition similar to Unit S-1 in Hole SEG75B. Unit S-2 is 24 cm of highly olivine-clinopyroxene phyric basaltic gravel similar to the underlying Unit I-1. Unit I-1 is 18 cm of fine-grained, amygdaloidal, highly olivine-clinopyroxene phyric basalt (10% olivine and 1% clinopyroxene). The basalt is very highly altered and with vesicles filled by green clay minerals. This unit is petrographically similar to the distinctive volcanic units first observed at Site SEG36. Unit I-1 is petrographically similar to clasts in Units S-1 and C-1 of Hole SEG75A. The volcanic basement was sampled at SEG75.
Drilling in Hole SEG76A penetrated 0.30 m before coring began, and coring terminated at 0.41 mbsf. Unit S-1 is a 3-cm subangular diamicton clast of gneissic composition. Unit C-1 is an 8-cm-long clast of aphyric basalt. The basalt is very highly altered with a yellowish brown appearance and is amygdaloidal with 0.5- to 2-mm spherically to irregularly shaped amygdules filled with orange and red clay minerals. Drilling in Hole SEG76B penetrated 1.12 m before coring began, and coring terminated at 1.40 mbsf. Unit S-1 is 10 cm of diamicton clasts consisting of subangular to subrounded clasts of gneiss and sandstone. Unit C-1 is 11 cm of cored clasts of fine-grained, highly olivine phyric basaltic composition with 50% olivine phenocrysts. The basalt is nonvesicular and apparently very fresh but different from the clast in Hole SEG76A. Unit C-1 is petrographically similar to the distinctive olivine phyric igneous units first recovered from Site SEG36. The volcanic basement may have been sampled at SEG76.
Drilling in Hole SEG77A penetrated 0.66 m before coring began, and coring terminated at 1.07 mbsf. Unit S-1 is 8 cm of moderately olivine phyric basaltic clasts compositionally similar to the underlying unit. Unit I-1 is 43 cm of fine-grained, amygdaloidal and vesicular, moderately olivine phyric basalt that is highly altered with 4% olivine phenocrysts. Large (0.5–4 mm) round to very elongate vesicles are filled with dark brown to yellow clays. Some vesicles are elongated in the same direction, which may be a flow feature. This unit is petrographically similar to the distinctive olivine phyric igneous and clast units first recovered from Site SEG36. Drilling in Hole SEG77B penetrated 0.40 cm before coring began, and coring terminated at 0.60 mbsf. Subunit S-1a is a 2-cm-long gneissic clast. Subunit S-1b is 36 cm of moderately olivine-phyric basaltic gravel similar to Unit I-1 in Hole SEG77A. Hole SEG77C was relocated ~10 m southeast of the original site target and drilling penetrated 0.56 m before coring began. Coring terminated at 1.47 mbsf. Unit S-1 is 49 cm of moderately olivine phyric basaltic gravel compositionally similar to Unit I-1 in Hole SEG77A. The volcanic basement was sampled at SEG77.
It was not possible to find stable ground for the drill rig on the seabed. No material was recovered from Hole SEG78A.
Drilling in Hole SEG79A penetrated 0.56 m before coring began, and coring terminated at 0.82 mbsf without recovery. Drilling in Hole SEG79B penetrated 0.32 m before coring began but terminated without recovery because of approaching ice flows. Hole SEG79C was drilled at a location offset ~10 m southeast from the original site target. Drilling penetrated 0.52 m before coring began, and coring terminated at 0.68 mbsf. Subunit S-1a is 2 cm of aphyric, fine-grained, reddish brown basaltic gravel. Subunit S-1b is 17 cm of highly olivine phyric basalt gravel similar to the underlying Unit C-1. Unit C-1 is a 16-cm-long cored clast of massive, highly olivine phyric basalt with a possibly glacially polished upper surface. The basalt contains 12% olivine and ~1% clinopyroxene and is moderately altered. Unit C-1 is petrographically similar to the distinctive olivine phyric igneous and clast units first recovered at Site SEG36. The volcanic basement may have been sampled at SEG79.
Drilling in Hole SEG80A was erratic, and coring terminated at 1.88 mbsf. Unit S-1 is 2 cm of diamicton clasts of basaltic and hornblende-biotite-garnet gneissic compositions. Unit C-1 is composed of medium-grained, porphyritic, highly clinopyroxene-plagioclase-olivine phyric basaltic clast that is moderately altered. Drilling in Hole SEG80B penetrated 2.54 m before coring began, and coring terminated at 3.00 mbsf. Unit S-1 is 3 cm of diamicton clasts of subrounded basalt and gneissic pebbles. Unit S-2 is 61 cm of gray, highly bioturbated, calcite-cemented but fragile micaceous sandstone with coal flasers (Fig. F7). Unit S-2 is interpreted to represent in situ sampling of the prebasaltic basin fill. The volcanic basement was not sampled at SEG80.
Drilling in Hole SEG81A terminated at 1.88 mbsf. Unit S-1 is 11 cm of diamicton clasts composed of 2- to 3-cm, large subangular fragments of sandstone and gneiss. Drilling in Hole SEG81B penetrated to 1.36 m and then stepped to 1.89 mbsf, where drilling was terminated without recovery. The volcanic basement was not sampled at Site SEG81.