Magnetostratigraphic and Biostratigraphic Synthesis, Deep Sea Drilling Project Leg 94

he Gulf of Alaska began about 0945 hr (local time) on 9 September 1992-the first daylight survey of the cruise. The survey was routine, and a beacon was dropped for Site 887 at about 1130 hr. Hole 887A was spudded with a good mud-line core at 2200 hr that same evening. Hole 887 A penetrated 285 m with 84% recovery and bottomed, after penetrating about 15 m of basaltic pea gravel, at basement. The attempt to spud Hole 887B, beginning at about 0600 hr on 11 September, met with failure twice, apparently because the APC apparatus was inoperable, which necessitated a pipe trip for a new bit assembly. Hole 887B finally was spudded at 0200 hr on the morning of 12 September and consisted of five APC cores (41.4 m cored and 103.5% recovery) raised for high-resolution studies of sediment and pore-water chemistry. With the recovery of Core 145-887B-2H, Leg 145 passed the 4000-m total core recovery level and became part of the now five-member elite group of ODP/DSDP cruises that has exceeded 4 km in total recovery. Hole 887C was spudded at 0600 hr on 12 September and was continued using the APC-coring system down to 274 mbsf with 98.4% recovery, a testament to the efficacy of the new aggressive piston-coring techniques. At 1100 hr on 13 September, we began the round trip to change the bit and set a bottom-hole assembly (BHA) for rotary-coring in the basement of the seamount platform. Hole 887D penetrated to 373.1 mbsf, about 84 m into basalt, with a low recovery of 20% in the rock. The last core of Leg 145, 145-887D-13R, arrived on deck at 0210 hr on 15 September, when preparation for logging began. The first two logging runs with the Quad combo and the formation microscanner (FMS) tools went well, but at about 0000 hr on 16 September, the FMS tool became stuck in the drill pipe during retrieval. Normal procedures could not dislodge it, so the crimper and then the cable cutter were sent down the wire, the cable was cut, and we started out of the hole. The suspect section of pipe arrived on deck about 1230 hr, the FMS tool was extracted, and the JOIDES Resolution got under way for Victoria, Canada, at 1500 hr on the 16th of September, about half a day sooner than expected. We were carrying 4321.40 m of sediment and basalt recovered from the sites of the North Pacific Transect, about 1 km more recovery than anticipatedthanks to the hard work and efficiency of the SEDCO drilling crews and the ODP operations group.The 289 m of sediment recovered at Site 887 can be divided into three lithologic units. Lithologic Unit I (0-90 mbsf) is an upper Pliocene to Quaternary siliceous silty clay (Subunit IA, 0-45 mbsf) and clay (Subunit IB,. Dropstones are numerous, and ash layers are common in Unit I. Lithologic Unit II (90-270 mbsf) is a lower Miocene to upper Pliocene siliceous ooze with scattered carbonate. Lithologic Unit II can be divided into three subunits. Lithologic Subunit IIA (90-174 mbsf) is an essentially pure diatom ooze of late Pliocene-late Miocene age. Subunit HB (174-235/mbsf) is an upper Miocene to middle Miocene calc...

Section: Diatomssupporting

confidence: 75%

Site 887

1993

“…The LO of the silicoflagellate Mesocena quadrangula has an approximate age of 0.70 Ma in the middle latitudes of the At lantic (Baldauf et al, 1987) and an age of 0.79 Ma in the east ern equatorial Pacific (Barren, 1980). The LO of Nitzschia fos silis has an approximate age of 0.58 to 0.64 Ma in the middle latitudes of the Atlantic (Baldauf et al, 1987) and approximates the LO of Mesocena quadrangula (0.79 Ma) in the eastern equa torial Pacific (Barren, 1980).…”

Section: Diatomsmentioning

confidence: 99%

“…The LO of Nitzschia fos silis has an approximate age of 0.58 to 0.64 Ma in the middle latitudes of the Atlantic (Baldauf et al, 1987) and approximates the LO of Mesocena quadrangula (0.79 Ma) in the eastern equa torial Pacific (Barren, 1980). The last occurrences of both M. quadrangula and N. fossilis occur between Samples 108-662A-5-1, 30 cm, and -662A-4H, CC.…”

Section: Diatomsmentioning

confidence: 99%

Site 662

1988

“…While such an assessment cannot yield actual corrections for numerical ages assigned to the biohorizons, it can provide powerful evidence that these biohorizons require further scrutiny, at least in regional biostratigraphic and chronostratigraphic contexts. Figure 2 is a chronology of calcareous nannofossil biohorizons compiled from Berggren et al (1985), with additions mainly from Baldauf et al (1987). (For sources of other data, see also Gartner, 1992.)…”

Section: Introductionmentioning

confidence: 99%

Intercalibration of Leg 133 Biostratigraphies

Gartner¹,

Wei²,

Kroon³

et al. 1993

The biohorizons of calcareous nannofossil and planktonic foraminifers have been intercalibrated for Ocean Drilling Program (ODP) sites drilled during Leg 133 on the northeastern Australian margin. The absence of an independent chronology (e.g., magnetostratigraphy) limits the evaluation of biohorizons for assessing their relative positions within the framework of the best established chronologies. The nannofossil chronology was arbitrarily taken as the reference framework. The order of several late Neogene biohorizons is frequently reversed. Three possible explanations can be invoked: redeposition, inadequate sample spacing, and diachrony. In the absence of proper control on the first two of these explanations, the third possibility cannot be evaluated properly.