Jack Baldauf

Equatorial Pacific productivity changes near the Eocene‐Oligocene boundary

There is general agreement that productivity in high latitudes increased in the late Eocene and remained high in the early Oligocene. Evidence for both increased and decreased productivity across the Eocene-Oligocene transition (EOT) in the tropics has been presented, usually based on only one paleoproductivity proxy and often in sites with incomplete recovery of the EOT itself. A complete record of the Eocene-Oligocene transition was obtained at three drill sites in the eastern equatorial Pacific Ocean (ODP Site 1218 and IODP Sites U1333 and U1334). Four paleoproductivity proxies that have been examined at these sites, together with carbon and oxygen isotope measurements on early Oligocene planktonic foraminifera, give evidence of ecologic and oceanographic change across this climatically important boundary. Export productivity dropped sharply in the basal Oligocene (~33.7 Ma) and only recovered several hundred thousand years later; however, overall paleoproductivity in the early Oligocene never reached the average levels found in the late Eocene and in more modern times. Changes in the isotopic gradients between deep- and shallow-living planktonic foraminifera suggest a gradual shoaling of the thermocline through the early Oligocene that, on average, affected accumulation rates of barite, benthic foraminifera, and opal, as well as diatom abundance near 33.5 Ma. An interval with abundant large diatoms beginning at 33.3 Ma suggests an intermediate thermocline depth, which was followed by further shoaling, a dominance of smaller diatoms, and an increase in average primary productivity as estimated from accumulation rates of benthic foraminifera.

Species-specific responses of late Miocene Discoaster spp. to enhanced biosilica productivity conditions in the equatorial Pacific and the Mediterranean

Census data of a major Cenozoic calcareous nannofossil genus (Discoaster) have been acquired from Site U1338, located near the Equator in the eastern Pacific Ocean and drilled in 2009 during Integrated Ocean Drilling Program (IODP) Expedition 321. The investigated 147.53 m thick upper Miocene sediment sequence is primarily composed of biogenic carbonate and biogenic silica. Diatom biostratigraphic data were used to develop a revised biomagnetostratigraphic age model, resulting in more variable late Miocene sedimentation rates. Carbonate content variations mainly reflect dilution by biogenic silica production, although intense carbonate dissolution affects a few shorter intervals. Abundance variations of discoasters show no distinct correlation with either carbonate or biosilica contents. The two dominant Discoaster taxa are D. brouweri and D. variabilis, except for a 12 m thick interval where D. bellus outnumbers the sum of all other discoasters by a factor of 4.6. Data presented indicate that first D. hamatus and then D. berggrenii both evolved from D. bellus. Three unusual morphotypes, here referred to as Discoaster A, B and C, increase in relative abundance during episodes of enhanced biosilica production in the upper half of the investigated sequence (Messinian). Strikingly similar morphotypes have been observed previously in Messinian age sediments from the Mediterranean, characterized by alternating deposition of biogenic carbonate and biosilica. This suggests a species-specific response among some of the late Miocene discoasters to broader oceanographic and climatic forcing that promoted episodes of enhanced deposition of biogenic silica.

The Ocean Drilling Program III: The shipboard laboratories on "JOIDES Resolution"

JOIDES Resolution (a.k.a. SEDCO/BP 471), the scientific drillship of the National Science Foundations Ocean Drilling Program, contains over 12,000 square feet of laboratory space. Years of experience gained in the previous JOIDES program of scientific ocean drilling (the Deep Sea Drilling Project) have provided many ideas for improving upon the capabilities of a scientific drillship. Each laboratory on JOIDES Resolution is designed to include state-of-the-art equipment and techniques. A laboratory module seven stories high was added to the ship. This allows for ship investigations of sedimentology, physical properties, paleomagnetics, chemistry, petrography, and paleontology. In addition, thin section, X-ray diffraction/X-ray fluorescence, underway geophysics, logging and downhole measurement, computer, photographic, core storage, and library facilities are all available. This paper emphasizes the new instrumentation that was acquired or developed for the laboratories. Some techniques and equipment are in use for the first time at sea. Our experiences with these through the programs early cruises are related. The program plans to continually update its shipboard laboratory capability.

THE OCEAN DRILLING PROGRAM. RESULTS FROM THE THIRD YEAR OF FIELD OPERATIONS

The Ocean Drilling Program (ODP) recently completed its first 18 cruises (3 years) by addressing important scientific problems in the regions of the Bahamas,Iberian margin, Norwegian Sea, Baffin Bay, Labrador Sea, Kane Fracture Zone,, Tyrrhenian Sea, Northwest African margin, Barbados forearc, Galapagos, Peru margin, Weddell Sea, Sub-Antarctic South Atlantic Ocean, Mascarene Plateau, Bengal Fan, Indus Fan, Oman margin, Owen Ridge and Southwest Indian Ridge. During this period, the ships drilling systems as well as the shipboard scientific laboratory complex have undergone a thorough testing, with modification made as required. Beginning in the fall of 1988, following a series of drilling cruises in the Indian Ocean, Joides Resolution will embark on a 2 year campaign of drilling in the western and central Pacific Ocean. Many of ODPs scientific and technical objectives have been addressed during the initial 18 cruises. For example, high-latitude drilling, initiated in the northern polar latitudes in 1985 (Leg 104 Norwegian Sea; Leg 105 Labrador Sea/Baffin Bay) continued in 1987 in the southern polar latitudes of the Weddel Sea and the sub-Antarctic South Atlantic Ocean (Legs 113 and 114). Another important thrust requiring a major commitment in engineering development has been in drilling holes in zero-age crust in regions with little or no sediment cover (Legs 106, 109 and 118). This paper focuses on ODPs third year of scientific operations and discusses areas of future studies.