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50 Years of Ocean Discovery: National Science Foundation 1950—2000 Scientific Ocean Drilling, from AMSOC to COMPOST Edward L. Winterer Scripps Institution of Oceanography, University of California, San Diego ABSTRACT For more than 30 years, following the abandonment of the bungled Mohole project, designed to drill a hole through the crust-mantle boundary, the National Science Foundation (NSF) has energetically supported and shepherded along a spectacularly successful scientific ocean drilling program that has cored oceanic sediments and crust at more than a thousand places over most of the global ocean. The program has tested major hypotheses such as seafloor spreading, provided the material basis for a increasingly fine-grained geologic time scale, delivered otherwise unattainable data on compositions and processes from levels deep beneath the seafloor, including the oceanic crust, and made possible the elaboration of a detailed global paleoceanographic history, extending back about 180 million years. Early mistakes and fumbles about responsibilities for oversight, funding, management, science operations, and scientific advice were corrected. Short-lived ventures into complicated, very high-tech schemes were abandoned with no harm to the main, continuing scientific thrust of the program. NSF found important funding and participation from other nations and has been responsive to requests from U.S. scientists for funds to carry out site surveys, postcruise studies of cores, and down-hole experiments. The crossroad ahead, when present funding expires in 2003, is hazardous. It is a major question whether the very costly and specialized riser-drilling program being planned for a new Japanese vessel, with still-fuzzy definition of the science objectives, can be funded alongside the more flexible style of nonriser drilling that has attracted scientists from such a large range of disciplines. Proposals and programs for coring into the ocean floor from floating platforms began in the United States in 1957 with a modest planning grant of $15,000 from the National Science Foundation (NSF) to the National Academy of Sciences. Since then, a half dozen ocean drilling programs— some huge, some tiny; some successes, some failures—have been funded, for a total NSF and international expenditure of a billion dollars. My own fervent conviction is that we have received extraordinary value for money. It is my purpose here, in my own idiosyncratic way, to take stock of the successes and failures of these programs, in terms of both their scientific and technical accomplishments and their management structures. THE MOHOLE PROJECT Some 41 years ago, Walter Munk, Harry Hess, and a few others, reacting to a long and wearying panel session reviewing good, but normal, science proposals in Earth science for the National Science Foundation, asked themselves if there weren't some truly major question running across subdisciplines that could be posed and answered, even if it took stretching technology and even if it might cost quite a lot of money. Their candidate question was: What is the physical nature of the Mohorovicic seismic discontinuity—the Moho—that marks a change in physical properties that defines the boundary between the Earth's crust and underlying mantle? To learn the answer, they thought it technically possible to drill a hole through the crust and to sample rocks across and at the boundary. Because the Moho beneath the oceans is only about 5 km beneath the deep seafloor, a drill ship that could drill through 5 km of rock in water depths of 5 km would be required. Not easy, not something that industry was actually doing, but something that was technically probably within reach. The self-constituted, small, and very informal American
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50 Years of Ocean Discovery: National Science Foundation 1950—2000 Miscellaneous Society (AMSOC), to which Munk, Hess, and Roger Revelle belonged, took the idea under its aegis at a meeting at Munk's home—always characterized as a wine breakfast—and submitted a proposal to NSF in mid-1957 to explore the feasibility of drilling (and coring) a hole to the Moho. To give AMSOC a cover of respectability and fiscal responsibility, the National Academy of Sciences (NAS), at the suggestion of NSF, gave it an administrative home. NSF granted $15,000 (half the amount requested) and the work began, with Willard Bascom, an experienced marine engineer, as executive director. It was he who coined the name Mohole for the project. AMSOC was to provide both scientific advice and management. One geophysicist, Maurice Ewing, Director of Lamont Geological Observatory, who became an AMSOC member by happening to be in the hallway of the Cosmos Club when AMSOC gathered nearby for a meeting, urged from the start that the single-site Mohole attempt should be preceded by coring at many places through the oceanic sediment cover, thought from seismic data, largely collected by ships of his institution, to be not more than about 1 km thick. He argued that not only would such an intermediate step provide experience in drilling in great water depths, but it would answer fundamental questions about the age of the ocean basins (permanent or young?) and the nature of the rocks below the sediments (harder sediments? volcanic rocks?). AMSOC, reflecting diverse views in the community, was divided on this, but decided temporarily to put aside Ewing's option and to keep the focus on the ultimate Moho target. The debate over this choice intensified over the life of Mohole, and the progressive ascendancy of the gradualists weakened the support in the scientific community for the one-hole approach. Industry and Congress quickly rallied in support of the concept of very deep drilling, spurred by the public boast of the USSR to start drilling its own hole through the Earth's crust and thus to demonstrate its technological superiority over the United States once again, as had just been done with Sputnik (van Keuren, 1995). Riding on this wave, a preliminary notice of a proposal to NSF went forward from AMSOC to NSF in 1958 for $2.75 million, to be available in 1960. The AMSOC proposal gave three possible types of drill sites: on a continent, on an oceanic atoll, and on the deep seafloor. The seafloor option prevailed, and for this a dynamically positioned, floating rig was deemed most feasible. The hardware part of the Mohole project got underway with some testing to see if a drill vessel could hold position in deep water during drilling, using a dynamic positioning system. AMSOC chartered an industry vessel, CUSS-I, which, after some preliminary tests in soft sediments of a Neogene turbidite basin in waters about 1,000 m deep west of San Diego, then drilled a hole 183 m deep in 3,570 m of water off the Mexican island of Guadalupe. The dynamic positioning scheme and the coring of both pelagic sediments and basaltic basement there were successful, opening the way to the more ambitious stage, a hole all the way to the Moho. The cost for this Guadalupe phase of Mohole was about $1.5 million. Enthusiasm was high and work to identify the best drill site proceeded. After extensive studies of existing geophysical records and some new survey work, a panel of geophysicists chose a site on the deep seafloor about 300 km north of the island of Oahu. All that was needed now was the actual heavy-duty drill ship. NSF next opened the bidding for construction and operation of the Mohole drill vessel. Several consortia of experienced oil companies and shipbuilders submitted bids, but the nod went not to the lowest bidder, but rather to a company with no experience in drilling, the Texas-based major engineering and construction firm of Brown and Root. Partly because of the low evaluation score assigned to its presentation in the first round of bidding and its ascent to the top in several re-reviews, cries of unfair political influence by Brown and Root resounded. A Houston Congressman, Albert Thomas, chaired the committee that controlled NSF's budget and another Texan, L.B. Johnson, was Vice-President. A particular feature of the contract was that Bascom's AMSOC group (now organized as a private company) was to be incorporated into the Brown and Root operation, to keep the contractor oriented toward the scientific goals. Bascom soon jumped ship, declaring that the contractor was not paying much attention to his group's advice. Although AMSOC-NAS was still supposed to be providing scientific advice, AMSOC members were scientists fully engaged in their own projects and, absent Bascom's group, could not or would not assume Moho management responsibilities. The result was that NSF itself, rather than some academic entity, was managing the project. The whole dreary tale of the bidding and rebidding process and of the subsequent delays, cost overruns (from original estimates of $14 million to later estimates of about $160 million) and final failure of the project has been recounted in detail, for example in Solow's 1963 article in Fortune magazine. After the expenditure of about $57 million, Congress (Representative Thomas, chairman of the committee controlling the NSF money having just died) denied further funding and NSF had to abandon Project Mohole, with no ship built or any ocean crustal hole drilled. One hole, about 300 m deep, was drilled on land into serpentinite (altered mantle?) near the coast of Puerto Rico, as a test of drilling tools. NSF learned the hazards of attempting management by NSF rather than by contractors with roots in the academic community concerned directly with the scientific goals of the project. In hindsight, given what we know now from three decades of drilling experience in crustal rocks, it is highly unlikely that drilling at the candidate Moho site near Oahu would have penetrated more than a small fraction of the thickness of the oceanic crust. By 1965, the Moho, as a near-term scientific objective, gradually faded from the agenda of working scientists.
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50 Years of Ocean Discovery: National Science Foundation 1950—2000 LOCO AND THE BIRTH OF JOIDES Instead, well before the death of Mohole, a new initiative, focused on oceanic sediments, moved forward. AMSOC itself, under its chairman Hollis Hedberg, had been increasingly inclined toward sediment drilling, partly as a prelude for Mohole and partly as an end in itself. There was much talk of a second ship for this purpose. Then Cesare Emiliani, of the University of Miami, seized the moment by proposing to NSF in 1962 a modest plan to use a small chartered drilling vessel to core sediments in the Caribbean Sea, a project labelled LOCO (LOng COres). The aim, wholly in keeping with his own special research interests, was to decipher and extend the paleoceanographic history of the Neogene when continental glaciers waxed and waned repeatedly in the northern hemisphere, causing major swings in global sea level. The swings could be monitored through the changing microfossil contents and stable isotopic compositions of cored calcareous pelagic sediments. To help guide this work, Emiliani formed a LOCO advisory group comprising scientists from the major U.S. oceanographic institutions, which evolved into the Joint Oceanographic Institutions for Deep Earth Sampling (JOIDES) organization in 1964, with much encouragement from NSF, and membership of four U.S. oceanographic institutions—Miami, Lamont, Woods Hole, and Scripps. JOIDES was to plan and provide scientific advice; the actual management of projects was to be contracted by NSF to individual JOIDES institutions. In the interim after the LOCO committee disbanded but before JOIDES formed, Emiliani drove ahead with his project and in 1963, after several attempts, successfully cored through about 55 m of pelagic sediments in 610 m of water off the coast of Jamaica from the small drill vessel Submarex (Emiliani and Jones, 1981). The LOCO program, driven by the ideas and persuasiveness of a single scientist and operated as a normal NSF grant, was a technical and scientific success and cost only about $100,000! D/V CALDRILL ON THE BLAKE PLATEAU JOIDES was now hard at work planning future drilling. Its first project, accomplished during 1965, was the drilling of a transect of holes across the Blake Plateau, a marginal submarine plateau at depths of 25-1,000 m off the Atlantic coast of Florida. The objective was to determine the history of relative sea level changes as an entree to the history of tectonic subsidence of a sector of the continental margin, which was known to have been a shallow-water reef area during the Late Cretaceous, some 70 million years ago. For this venture, NSF, on the advice of JOIDES, awarded the managerial contract to Lamont, which seized the offer of an oil company to allow use of its chartered vessel D/V CaMrill while it was in transit from Panama to Canada. In the spirit of JOIDES, the shipboard scientists came from several JOIDES institutions and the U.S. Geological Survey. CaMrill maintained position by monitoring deviations from the vertical of a taut wire from the vessel to an anchor on the seafloor. The data went to a computer that controlled four large outboard motors on the four "corners" of the ship and kept the ship on station. The cores (recovery about 25-70 percent) from the six drill sites nicely documented the Cenozoic drowning history of the old Cretaceous carbonate platform, but everyone understood that the taut-wire station-keeping system would not be applicable to operations in the deep sea, the place everyone wanted to go. For this, a larger vessel with dynamic positioning was required. DSDP AND D/V GLOMAR CHALLENGER After the three coring ventures, Guadalupe Mohole, LOCO, and the Blake Plateau, sediment cores were now seen as fairly easy to recover. Microfossils in the cores were generally sufficiently abundant to determine the geologic age of samples. Coring could be extended at least into the upper part of basaltic oceanic basement and its age estimated from the paleontological age of the immediately overlying sediments. In principle, these two simple facts opened the possibility of working out not only the paleoceanographic history of the ocean basins over the past 100 million years (the age of the then-oldest known samples from the ocean floor), but also the age of oceanic crust in all the oceans. A heady vision! At NSF, awareness was growing that coring of sediments was probably better done from a ship other than the Mohole ship. A sediment-coring ship would need be on station only for days or weeks, while the Mohole ship would be on station for years. The two programs were now being viewed as independent, and so NSF, in 1963, proposed to Congress an Ocean Sediment Coring Program, distinct from the Mohole Project. Funds were provided for the new program in fiscal year 1965. The trigger for realizing an oceanic drilling project was the acquisition of a practical dynamic positioning system. This system, considerably refined from that deployed from CUSS I, comprised an acoustic transponder dropped from the ship onto the seafloor and an array of four hydrophones lowered a little below the ship's hull. The arrival-time differences of signals from the transponder were processed in a computer, which controlled the ship's main propulsion system and lateral tunnel thrusters, keeping the ship for weeks at a time generally well within a circle with a diameter less than 10 percent of water depth. JOIDES panels had recommended to NSF the acquisition of a drilling vessel capable of coring in water as much as 6,000 m deep for periods of months in moderate sea conditions and of coring continuously into both sediments and basement rocks to subseafloor depths of several kilometers. NSF, in 1966, awarded to Scripps a prime contract for 18 months of drilling, with a first year's infusion of $7.4 mil
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50 Years of Ocean Discovery: National Science Foundation 1950—2000 lion. Scripps immediately set about acquiring a suitable vessel and recruiting the managerial and technical staff required to operate the scientific parts of the program, now called the Deep Sea Drilling Project (DSDP). Scripps, in 1967, sub-contracted with Global Marine, Inc., to supply the drill vessel, which Global Marine christened Glomar Challenger, in honor of the great exploring vessel of the nineteenth century. Scripps equipped it with laboratories for the preliminary study and curation of core samples. By the middle of 1968 the ship was ready to sail, staffed by Global Marine ship and drilling crews and by Scripps technicians. Scientific parties were recruited for each eight-week leg from the entire scientific community, foreign and domestic. The contractual terms required that Scripps take from JOIDES its scientific advice on the definition of objectives for each leg, the general track of the vessel, the shipboard measurements to be made, the curation of the cores, and down-hole measurements. JOIDES also recommended shipboard scientists to DSDP. JOIDES advised, Scripps managed as prime contractor, and NSF monitored—and paid. The First 18 Months: Validating the Promise The Deep Sea Drilling Project would not have been possible had it not been that the main features of the bathymetry of the oceans were known from echo sounding during and after World War II. In addition, a near-global web of seismic reflection profiles had already been collected, mainly by Lamont ships; and magnetometer surveys showing anomaly patterns had been made. The new plate tectonic hypothesis was the hottest topic in Earth science. There were big ideas to put to the test and there was a way to pick good sites for the testing. What was hoped for and what was accomplished during the first 18 months? A quick overview of the major scientific achievements shows why nobody wanted to stop drilling at the end of that time. JOIDES planners had by now devised a nine-leg plan of drilling: a beginning leg in the Gulf of Mexico, partly to explore one of the Sigsbee Knolls (a group of buried salt domes); then one leg each across the North and South Atlantic, mainly to date oceanic crust; a leg in the Caribbean; then five legs in the Pacific, including a north-south transect of the thick pile of pelagic sediments close to the Equator; and a long loop westward to explore the possibly very old crust farthest from the active East Pacific Rise spreading ridge. Then to the home port of Long Beach to end the project. The ship went first to the Atlantic, mainly to test the sea-floor-spreading hypothesis. The first leg, led by Ewing, drilled into the caprock of a salt dome in 3,572 m of water, where geophysical evidence suggested the crust might be oceanic rather than continental. The drilling did not settle the question of the depth of water during salt accumulation. The drilling did make JOIDES aware of the risk of encountering uncontrollable hydrocarbons, and so planners created a Safety and Pollution Panel to screen proposed sites for their risk potential. The following leg, across the North Atlantic, ran into serious problems with hard chert layers in the lower Cenozoic sediments, and reached basaltic basement at only three sites. Calcareous sediments at depths below the present compensation depth for calcite (about 4,500 m) suggested subsidence of the seafloor. The age distribution of basement was shown to be consistent with spreading from the Mid-Atlantic Ridge, but could not be considered a good test of the hypothesis. Leg 3, across the South Atlantic from Dakar to Rio, was a blockbuster. The main objective was no less than a rigorous test of the then-new hypothesis of seafloor spreading. J. Heirtzler had identified magnetic anomalies on both sides of the Mid-Atlantic Ridge along a transect across the South Atlantic and had estimated the ages of the anomalies by extrapolating back into the Late Cretaceous the radiometric ages of magnetic reversals in Neogene lava flows on land, assuming uniform spreading rates. Two geophysicists, Art Maxwell and Dick von Herzen, were designated as co-chief scientists. Drilling showed a near-perfect match between magnetically predicted basement ages and paleontologically determined ages of basal sediments, and for this reason alone the leg was a triumph. Seafloor spreading leaped from hypothesis to ruling theory at a single bound. But also among the scientific party were two geologists, Ken Hsü and Jim Andrews, who persuaded their co-chiefs to take lots of sediment cores on their way to the crucial contact between sediments and basement—the single core that some geophysicists wanted from a hole. In the long sequences of near-continuous cores, Hsü and Andrews recognized changes in the degree to which calcareous fossils were preserved from destruction by dissolution at the seafloor. Their data provided the basis for others to reconstruct the history for the South Atlantic of fluctuations in the depth of complete calcite dissolution, the calcite compensation depth (CCD). Quantitative paleoceanography was now a discipline, and drilling was the way toward writing a paleoceanographic history, back to about 180 million years ago and for all the world ocean. The final Atlantic leg, in the western South Atlantic and in the Caribbean, reconnoitered a diverse array of problems, solving none of them, but whetting appetites for more focused work, especially in the Caribbean. Reconnaissance legs—and there were a number of them in the early part of DSDP—open up problems but don't generally solve them. In the Pacific, two big questions lay open to the drill: What was the history of pelagic sedimentation in the equatorial high-productivity zone, and what was the age of oceanic lithosphere in the western Pacific, far from the active East Pacific Rise spreading ridge? In the eastern Pacific, planners laid out a three-leg, north-south transect, from about 41°N to 30°S, but the results of the first of these, from 41°N to 14°N, showed that dissolution on the seafloor had destroyed most
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50 Years of Ocean Discovery: National Science Foundation 1950—2000 microfossils at these latitudes. JOIDES therefore asked DSDP to change plans, substituting an east-west transect along the equator for the southern part of the original track. This was an early demonstration of the need to keep feeding new results into future planning and established an enduring modus operandi. The results from these three early Pacific legs documented the strong dependence on latitude not only of pelagic sediment accumulation rates, but also of the depth profiles of carbonate dissolution for the past 35 million years. The drilling further opened up the problem of sedimentation on an oceanic plate that is moving not only east-west, as in the Atlantic, but also north-south, across the equatorial high-fertility zone. From the sediment-thickness data, epoch by epoch, a quantitative estimate of the rate of northward plate motion could be made and compared with independent estimates coming from the recently introduced fixed-hotspot model for the evolution of the linear Hawaiian volcanic chain. Recognition of the abundance of well-preserved microfossils and of the near-continuous record of sedimentation in the Pacific equatorial zone led to several later coring legs that provided us with the material basis for an extraordinarily detailed biostratigraphic time scale, combining all three major groups of planktonic microfossils: foraminifera, coccolithophorids (nanofossils), and radiolarians. The results from the two-leg swing into the central and western Pacific, the region farthest from the actively spreading East Pacific Rise, could only hint at the history of the Mesozoic Pacific. On one of the legs, the ship was used more like a dredge than a drill and few cores were recovered during repeated attempts (36 holes!) to core the sediment-basement contact. Two western Pacific oceanic plateaus, Shatsky and Ontong Java, were drilled, and Lower Cretaceous strata were confirmed on Shatsky. Ontong Java (still the cynosure of many eyes) is covered by about 1 km of pelagic sediments, but chert layers, here as elsewhere, blocked penetration of the flat-faced diamond bits used in the early days of the project and interfered with recovery of more than a few chips of rock. Better technology was urgently needed. Lessons Learned Early A lesson learned from drilling during the first 18 months from both engineering and scientific perspectives was that coring should be continuous, and that vastly improved methods were required to get these continuous records in piles of sediment with widely varying physical properties (e.g., alternating chert and chalk layers). The JOIDES Planning Committee later ordained continuous coring as the norm and engineers developed better drill bits, a system of heave compensation to keep the drill bit from moving up and down with the motion of the vessel (ready for sea trials on Leg 33 in 1973), and a hydraulic piston corer that recovers long, undisturbed cores free of vessel motion (ready for Leg 64 in 1978). Pressure core barrels have been deployed to retrieve gas hydrate samples under in situ pressures. Gradually and intermittently, then more regularly, down-hole logging was instituted for most holes, and a fruitful collaboration was established with logging companies, to improve and widen the scope and effectiveness of the logging tools available. These tools have not only helped to fill in gaps in the cores, but enabled correlation of drill results with those of seismic reflection profiling, and establishment of heat flow values and other geophysical parameters. From the very beginning, scientific panels advocated using the holes as ''natural laboratories," but budgets and time constraints kept this activity at a slow pace. Nonetheless, over the years, the drilled holes have been increasingly used for measurement of such variables as heat flow and for experiments on fluid flow, seismic velocity, and earthquake monitoring, to name but a few. What was needed, from the very first, was money to design, test, and put into action these technologic innovations. The reality was that there was never enough money. The contract with Global Marine was fixed and the remaining funds were for all the rest. If the planners asked for better bits or more logging, then the money had to come out of science operations. For example, until the very end of DSDP in 1983, NSF allowed expenditure for only one computer for word processing for a project that was publishing a 1000-page hard-back report on scientific results every two months. The Long Haul As easily predicted, before the ship had progressed more than part way along its planned nine-leg track, plans were already changing and new proposals were submitted to extend the project. So excited was the scientific community by the early results that NSF, after suitable review and by simple amendment to the initial contract, extended the project for another two years. Time and again extensions were granted, going on now for 30 years. Contractors have changed, the JOIDES organization has expanded, international partners have been recruited, funding sources have been added (and deleted), names have changed, the drill ship has been replaced and project management shifted, while the drilling goes on and new scientific results pour in. Almost immediately after the formation of JOIDES, the University of Washington was added to the group and U.S. JOIDES institutions now number eleven. A U.S. corporate entity, Joint Oceanographic Institutions, Inc., was created to provide fiscal responsibility for JOIDES, so that NSF could sign contracts to support JOIDES activities. From the beginning of DSDP, many non-U.S. scientists had been members of the scientific parties aboard the ship, but in 1975, by requests from several countries and with the active encouragement of NSF, the project was formally internationalized as the International Program for Ocean Drilling (IPOD). Several partner nations (Germany, the USSR, France, United
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50 Years of Ocean Discovery: National Science Foundation 1950—2000 Kingdom, Japan) joined JOIDES, each paying a share of project costs as annual "dues." The list of member countries and consortia of countries has fluctuated over the years, but their combined contribution to the drilling program now constitutes roughly 40 percent of the costs. They also contribute significantly to site surveys in preparation for drilling, pay the salaries and travel costs of their nationals, and fund their shipboard scientists for postcruise analysis of samples and data. After IPOD had been in existence for a few years, NSF came to realize that U.S. shipboard scientists were at a competitive disadvantage on funding and set up a system of support through a U.S. Scientific Advisory Committee (USSAC) that also gives grants (through NSF) to support other drilling-related science. Each partner nation is responsible for its own site survey expenditures, and NSF has responded quite generously to U.S. proposals for geophysical surveys in support of drilling. A breakdown of the $1 billion expended by NSF and its international partners on the various ocean drilling projects, from Mohole to the present day, is shown in Table 1. DETOUR: THE OCEAN MARGIN DRILLING PROGRAM In the late 1970s and early 1980s, paced by improvements in seismic reflection systems available in academia, scientific interest in the JOIDES community began to focus very seriously on thickly sedimented continental margins such as the Atlantic margin of North America and the margins of Africa. To reach prime objectives at these places without risk of encountering oil or gas accumulations that could escape to the seafloor, a ship equipped with a riser system was needed (i.e., a system in which the drill pipe is within a surrounding pipe and drilling fluids pumped down the inner, rotating pipe are circulated back to the ship within the annular space between the two pipes). This system allows pressure controls (i.e., drilling muds and shut-off devices). NSF, with support from the Carter Administration, approached representatives of the U.S. oil industry with a suggestion that JOIDES and industry might form a kind of consortium to accomplish scientific drilling on margins, with industry supplying technical expertise, some geophysical survey data, and some financial support. Industry went along for a time with this new Ocean Margin Drilling (OMD) program to the extent of sending delegates to the OMD scientific planning committee meetings and paying for a set of data synthesis albums. Some participants from industry were from the beginning hesitant not only about the potential costs of the program, but also about the possible presence of an "open-book" program operating in waters of economic interest to the companies. One requirement troublesome to most U.S. academic scientists was that non-U.S. participation was excluded. In 1984, on hearing the final cost estimates and with the Reagan Administration now at the helm, many industrial participants withdrew from the project, which then collapsed. About $16 million had been spent, nearly all on administrative expenses and engineering studies. No steel was cut, no holes were drilled. During the OMD effort, a search had been made for a suitable drill ship for the riser program. The daily costs for commercial vessels of this class were prohibitively high, and planners then turned to the famous Glomar Explorer, the ship that the Central Intelligence Agency had commissioned to recover the coding device from a Soviet submarine that sank in deep water northwest of the Hawaiian Islands. This recovery effort, thinly disguised as a manganese nodule hunt, in an area where nodules were not very abundant and compositionally of little commercial interest, was successful and the special ship, with its derrick, drawworks with immense lifting power, dynamic positioning, and very large spaces available for laboratories, was in mothballs near San Francisco. NSF, as part of the OMD program, contracted with engineers to draw plans for conversion of this government-owned ship for riser drilling. The cost estimates were huge, in fact unacceptable. The ship remained in mothballs until 1996, when it was at last converted to a deepwater drillship for Chevron and Texaco, at a cost of about $ 160 million. JOIDES RESOLUTION AND ODP: A NEW SHIP AND A NEW MANAGEMENT Owing to strong pressures from the scientific community, the DSDP drilling program was kept on course through all the OMD detour. At about this time, a crisis in industry sent daily rates for drill ships plummeting, and an alert NSF moved quickly to hire a particularly suitable ship, the D/V Sedco 471, owned and operated by British Petroleum and Schlumberger, at bargain rates. By November 1983, D/V Glomar Challenger had completed 96 consecutive legs of drilling. The acquisition of the larger and more capable ship coincided with a move of management of the project from the Deep Sea Drilling Project at Scripps Institution of Oceanography to the Ocean Drilling Program (ODP) at Texas A&M University. After a hiatus of only 14 months, drilling began again using D/V Sedco 471, known henceforth to the scientific community as JOIDES Resolution, a name not only honoring Cook's eighteenth-century exploring ship, but also resonating with notions of community accord, group determination, and scientific problem solving. Drilling began (ODP Leg 100) in January 1985. We are now (Leg 182) drilling along the Great Australian Bight and the system is performing well, given that budgets are now so tight that some scheduled scientific plans cannot be carried out for lack of proper tools being available on the ship. SCIENTIFIC MILESTONES: RESULTS THAT CHANGED OUR WAY OF THINKING In looking back over the past 30 years of scientific ocean drilling, certain milestones mark signal achievements, some
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50 Years of Ocean Discovery: National Science Foundation 1950—2000 TABLE 1 NSF Expenditures for Scientific Ocean Drilling Programs, 1958-1998 (thousand dollars) DSDP OMD ODP Year Mohole LOCO Caldrill U.S. Ship U.S. Sciencea International U.S. Ship U.S. Sciencea International Annual Totals 1958 20 20 1959 20 20 1960 220 220 1961 1,520 1,520 1962 1,970 1,970 1963 3,820 20 3,840 1964 8,000 88 8,088 1965 24,700 250 24,950 1966 16,970 5,400 22,370 1967 0 1968 4,160 42 4,202 1969 2,430 20 2,450 1970 6,300 175 6,475 1971 7,010 7,010 1972 8,930 282 9,212 1973 9,250 269 9,519 1974 10,700 295 250 11,245 1975 10,220 185 1,250 11,655 1976 11,800 3,500 15,300 1977 12,800 100 3,880 16,780 1978 12,700 204 4,400 70 17,374 1979 9,260 1,800 8,000 1,000 20,060 1980 13,940 1,020 4,880 3,400 23,240 1981 14,790 2,158 5,600 4,888 27,436 1982 13,070 1,468 8,560 5,578 28,676 1983 15,500 1,145 6,460 1,313 3,640 28,058 1984 1,340 1,482 1,000 22,530 2,026 4,170 32,548 1985 1,070 22,760 3,695 7,600 35,125 1986 2,120 19,430 7,342 12,510 41,402 1987 210 20,220 8,600 15,000 44,030 1988 20,650 8,900 15,000 44,550 1989 21,250 9,800 15,000 46,050 1990 21,550 9,700 16,600 47,850 1991 23,460 10,100 16,500 50,060 1992 24,980 11,600 16,580 53,160 1993 25,400 10,000 17,800 53,200 1994 28,430 10,100 15,770 54,300 1995 27,550 11,500 16,720 55,770 1996 27,680 11,400 16,720 55,800 1997 27,440 12,450 16,960 56,850 1998 29,946 10,950 17,454 58,350 TOTALS 57,240 108 250 173,000 10,645 47,780 16,249 366,916 138,163 220,384 1,030,735 a The category U.S. Science, under DSDP and ODP, includes grants to U.S. scientists for drilling-related research and for U.S. site surveys in support of drilling. SOURCE: Bruce Malfait, NSF, August 1998.
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50 Years of Ocean Discovery: National Science Foundation 1950—2000 of which are set out in recent overviews (Malfait et al., 1993; Larson et al., 1997). Other achievements, just as significant, are the cumulative result of many legs of drilling. I review here a sampling—probably reflecting my own interests—of some of the most important results, findings that truly changed our way of thinking. I also mention a few problems that remain as very important but unresolved by drilling. Time Scales It has been said that the special philosophical contribution of the geological sciences is the establishment of the immensity of geologic time. The elaboration and refinement of time scales have developed apace with new methods to measure the passage of relative and absolute time: superposition of strata, cross-cutting relations among rock bodies, biostratigraphy, radiometric decay, magnetic reversals, variations in isotopic compositions of strata, and rhythmically deposited sediments. Because cores of pelagic sediments from ocean drilling are commonly exceptionally rich in the remains of the most important planktonic microfossils—radiolarians, foraminifers, and coccolithophorids—the cores provide the basis for very detailed biostratigraphic zonations, based on first and last appearances and joint occurrences of taxa. The web of drill sites in the different oceans enables the establishment of a virtually global biostratigraphic scheme for the past 150 million years. The continuous cores also provide material for determination of magnetic-reversal sequences, which can in turn be linked to the sequence of seafloor magnetic anomalies. The direct radiometric dating of volcanic ash beds in the sediments and of drilled oceanic crust, using laser technology that can yield 0.1 million-years resolution, plus radiometric dating of biostratigraphically constrained ash beds and igneous rocks on the land, has improved resolution by an order magnitude since the Ocean Drilling Program began. In the last decade, these scales, with resolution of about 0.5-2 million years, have been further refined by an order of magnitude by the realization that rhythmic sedimentation in step with the rhythmic changes in the Earth's orbital parameters is a common feature of pelagic sediments. We are now close to the definition of a time scale for the last 30 million years with 20,000- to 100,000-year resolving power. The road is open to extend this precision back into the Jurassic via our drill cores. Having a time scale with such fine resolution makes it possible to address a host of rate problems: rates of sediment accumulation, rates of evolution, rates of change of environment. It makes possible the detailed ordering of related events on a global scale and the unraveling of cause-and-effect, chicken-and-egg problems. Paleoceanography The planktonic microfossils in pelagic sediments fall to the seafloor from overlying near-surface waters and thus reflect prevailing environmental conditions in these waters, while benthic fossils reflect conditions at the seafloor. This simple picture is distorted by the effects of dissolution: calcareous fossils tend selectively to dissolve in cold deep waters, owing to the greater dissolved carbon dioxide content there. Thus, to make paleoceanography quantitative, we need an independent method of estimating paleodepth. Almost concurrent with the start of drilling, an empirical relation was established, using an early version of the magnetic anomaly time scale, for the age of oceanic crust and its depth below the sea surface. The empirical curve, with correction for isostatic loading by sediments, fits closely to a simple curve D = D0 + K(Age1/2), where D is the depth of oceanic crust, D0 is the depth at the spreading center and K is a constant, generally about 350. The curve is applicable out to crust about 80 million years old, where it begins to flatten. The immediate payoff was the charting of the regional and temporal fluctuations in the depth where carbonate supply and dissolution rates balance, the calcite compensation depth (CCD). A first-order finding was that there was an abrupt deepening of the CCD by about 1,000 m near the beginning of the Oligocene, about 35 million years ago, at about the time of the earliest continental-scale Antarctic glaciation. Global paleodepth maps of the CCD now exist for many levels in the post-Jurassic. A paleoceanographical surprise emerged with the coring of organic carbon-rich layers at several levels in the mid-Cretaceous in both the Atlantic and the Pacific oceans. Paleodepth estimates for these sediments yielded a broad range of depths, excluding the abyssal waters of the Pacific, suggesting that the anoxic conditions were associated with a broadening and intensification of the oxygen minimum, possibly owing to relatively strong density stratification of the oceans during these extreme "greenhouse" times of raised global sea level and warm ocean temperatures. Determination of 16O/18O in precisely dated mid-Cretaceous-Recent planktonic and benthic foranminifers has allowed construction of a detailed history of oceanic surface-and bottom-water temperatures and an estimate of the changing volumes of continental ice. What the isotope record shows, besides the contrast between the generally warm "greenhouse" ocean climates of the Cretaceous and the colder (in high latitudes) "icehouse" climates of the Neogene, is a stepwise history of long periods of relatively stable conditions and abrupt transitions to new, but different, stable conditions. The record also shows that tropical sea-surface temperatures have been relatively stable; it has been the high-latitude oceans (and the deep waters derived from these latitudes), that have changed the most. What we do not understand are the "why's" of the stepwise history. One promising avenue was explored in the South Atlantic by coring the summit and flanks of Walvis Ridge in a highly successful attempt to document the history of bottom-water temperatures along an oceanic depth profile (Shackleton et al., 1984). The depth-profile approach has not since been much exploited,
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50 Years of Ocean Discovery: National Science Foundation 1950—2000 but holds great promise in mapping the paleotemperature structure of the oceans. Beginning with DSDP Leg 27, attempts were made to drill in very high latitude waters, mainly for paleoceanographic objectives. In spite of daunting conditions, drilling around Antarctica and in the seas off northeast Greenland and in the Labrador Sea has elucidated the Paleogene beginnings of continental glaciation and clarified the plate tectonic events that opened a circum-Antarctic Ocean and led to the formation of Antarctic Bottom Water. In the north, drilling has enabled reconstruction of the history of formation of North Atlantic Deep Water. Drilling on the two sides of the Isthmus of Panama has established the timing of the late Neogene closure of the isthmus, isolating Atlantic from Pacific marine biotas and forming a land bridge for terrestrial animals. Catastrophes: The K/T Event and the Desiccate Mediterranean Two spectacular events have captured public imaginations, the impact of the cosmic bolide that struck Earth at the end of the Cretaceous and the drying-up of the Mediterranean near the end of the Miocene. The K/T bolide story has depended as much on data obtained from land outcrops as from the ocean drill cores, which have served mainly to provide an especially detailed record of the sequence of events in regions relatively close to the impact site, on the Yucatan Peninsula. The discovery of the Mediterranean events, on the other hand, was almost purely the result of drilling on DSDP Legs 13 and 42A, which showed that the salt deposits that accumulated in shallow salt marshes and brine basins at the bottom of several Mediterranean depressions are both underlain and overlain directly by deep-sea biogenic sediments. Only small tectonic movements were required to isolate the Mediterranean from the Atlantic, and near-total evaporation, which may have been repeated many times, was likely very quick. These two catastrophes are now so well documented that, taken together with the evidence about very rapid shifts in ocean temperatures and the long-standing evidence of catastrophic floods on land (e.g., the rapid emptying of Lake Missoula to create the scablands of Washington), they are softening the rock-hard beliefs of the Earth science community in traditional gradualism. We must now admit the possibility of rare and powerful events, the amplifying effects of critically located small events, and the wide range of possible rates of change. James Hutton, the father of classical uniformitarianism and his disciple Charles Lyell may be uneasy in their graves. Gas Hydrates and Living Bacteria at Depth Solid hydrates of methane are stable in the pore spaces of sediments where the temperatures are cold or the confining pressures sufficient. Vast regions of the arctic tundra are underlain by sediments containing gas hydrates, and drilling has confirmed that continental margin sediments containing concentrations of biogenic methane also contain crystalline gas hydrates where temperatures and confining pressures are right. These concentrations are commonly visible on reflection seismic records as "bottom-simulating reflectors." Drilling has permitted preliminary estimates of the locations of these buried hydrates and an appreciation of the quantities of methane that might be released into the atmosphere if bottom-water temperatures were to rise significantly. Although evidence of bacteria has been recovered in cores from oil exploration and from pores in volcanic glass under 400 m of mid-Atlantic sediments, ODP drilling in plant-rich layers in turbidites of the Amazon deep-sea fan in the Atlantic Ocean has recovered bacteria that are actively reproducing at subbottom depths of hundreds of meters. Taken together with the evidence of living bacteria from the high-temperature vents along spreading ridges, we can agree with Reiche (1945) that "The infernos envisioned by medieval theologians can [hold] only limited terrors for such creatures." We are still exploring for the outer limits of the biosphere. Oceanic Lithosphere and Hydrothermal Activity Early attempts to drill into very young oceanic lithosphere, close to the active spreading centers where post-emplacement alteration of rocks should be minimal, were defeated. The brittle and fractured basaltic rocks broke up in front of the drill and stopped progress. Except in areas of strong hydrothermal alteration, we have still not been able to sample more than a few meters into "zero-age" oceanic crust. The most successful drilling has been at a site off Costa Rica on crust about 6 million years old, covered by about 275 m of sediment. Here coring was successful to a depth of 1,836 m into pillow basalts and sheeted dikes. Surprisingly, seismic velocities commonly associated with Layer 3, generally believed to be gabbro, are measured at this hole in part of the zone of sheeted dikes and basalt flows. The deeper parts of the oceanic lithosphere can be reached only where spreading was very slow and magma supply so skimpy that basalts are thin or absent and spreading has allowed gabbro and mantle rocks to emerge at the seafloor. Gabbros were cored almost continuously at a site on the slow-spreading Southwest Indian Ridge, southeast of Africa, yielding virtually the full suite of oceanic plutonic rocks and partly validating models erected on the basis of scattered dredge samples and from studies of supposed oceanic lithosphere tectonically emplaced onto continents—the ophiolites. The excellent drilling conditions at this site suggest that, in principle, one might reach the dreamed-of Moho here. The mantle itself has been cored at a few places, (e.g., in the Atlantic off Iberia in tectonically disturbed locales, where ultrabasic rocks have been serpentinized and uplifted in dia
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50 Years of Ocean Discovery: National Science Foundation 1950—2000 pirs that reached the seafloor, and in magma-starved segments of the Mid-Atlantic Ridge). In the Pacific, serpentinized mantle rocks were recovered by drilling in a tectonic rift zone. Because seismic data indicate that the Moho is present at depth even where altered mantle rocks are close to the seafloor, we are left with the original AMSOC question: What is the nature of this seismic discontinuity? Is it an original petrologic boundary, a tectonic boundary, or a level in the lithosphere marking the downward limit of alteration by circulating seawater? Or any one of these, depending on where you are? Repeated measurements over a period of several years at the Costa Rica drill site show that cool ocean water is being drawn down into the upper parts of the oceanic crust. Heat flow measurements and direct observation from submersibles show that hot waters, charged with ions from crustal alteration, emerge elsewhere at oceanic spreading centers and from outcrops of crustal rocks on abyssal hills. The drill has successfully recovered hydrothermal spring deposits close to an active spreading center, deposits that include tall chimneys of sparkling metal sulfides. Gradually, we are building up quantitative estimates of the rates and depths of circulation of seawater through the oceanic lithosphere and of the extent to which this flow moderates the composition of seawater. Drilling on crust ranging in age back to the Middle Jurassic shows that most hydrothermal alteration takes place while the lithosphere is very young. Beginning with the clean test of seafloor spreading on Leg 3, the determination of the age of oceanic lithosphere has been made at many of the 1100 sites drilled, giving us a set of ties between the biostratigraphic scale and magnetic anomalies, back to the mid-Jurassic, and enabling the interpretation of magnetic anomaly patterns in terms of plate tectonic evolution. Mantle Plumes, Hotspots, and Early Cretaceous Volcanism The ruling theory for the formation of linear seamount chains is that they result from motion of a plate over a fixed melting anomaly, or hotspot, in the underlying mantle. Drilling along the Emperor Seamount Chain in the North Pacific and the Ninety East Ridge in the Indian Ocean showed that these fitted the model. Other drilled chains (e.g., the Line and Marshall chains in the Pacific) have messy records of progressive volcanism, and some undrilled chains, sampled by dredge and by hammer, (e.g., the Australs and the Puka Puka chains), show a scrambling of ages, inconsistent with fixed hotspots. Linear seamount chains remain a problem. Several oceanic plateaus—great deep-rooted (tens of kilometers to the Moho), smooth-backed leviathans that rise to levels 1-3 km above the surrounding deep ocean floor—have been drilled, primarily for the continuous stratigraphy of the mainly calcareous pelagic sediments that blanket the basaltic basement. The origin of many of the plateaus is ascribed to mantle plumes, arising mainly during a short interval during the mid-Cretaceous from unknown depths. Beyond limiting the times of formation, drilling has got us almost nowhere on the plateau problem so far. Dating of the age of emplacement of several of the major oceanic plateaus (Ontong Java, Manihiki, Kerguelen), of scores of seamounts spread over a large part of the western Pacific and the great volumes of basalt on the deep Pacific seafloor, far from any contemporary spreading ridge, points to a highly unusual time of massive volcanism during a relatively short time of only about 20 million years in the Early Cretaceous. The volumes are comparable to those produced along the entire global spreading system and suggest some very deep rooted cause, a veritable revolution in the Earth's mantle. The near coincidence of these events with the beginning of the long period of normal polarity of the Earth's magnetic field and of the widespread deposition of organic-rich black sediments and evidence for warm climates, has stimulated a search for causal connections among these effects. Passive Continental Margins The Atlantic Ocean is bordered by passive continental margins, segments of which have been subsiding and receiving continent-derived and carbonate sediments since the Middle Jurassic. The North American margin is covered by a prism of sediments too thick for full penetration with JOIDES Resolution, but the European-African margin has a much thinner cover, and the early history of the margin is thus within reach of the drill. Cores documenting the early history of the Morocco margin show a beginning with a Late Triassic proto-Atlantic saline basin below sea level and progressive Mesozoic evolution from fluviatile to deeper and deeper waters. Farther north, in the Norwegian Sea, which opened much later than the Central Atlantic, drilling penetrated and sampled huge wedges of mainly subaerial early Tertiary basalts that were extruded from both sides of the widening rift between Norway and Greenland. Such marginal basalts are imaged on seismic records from many other segments of passive margin around the world and may be related to voluminous mantle plumes that may localize and even initiate seafloor spreading. Active Continental Margins, Island Arcs, and Backarc Basins Concentrated drilling has been done on several active continental margins, where oceanic lithosphere is being sub-ducted beneath a volcanic arc. These places are the loci of major seismicity, and understanding processes in them should contribute to public safety. The clearest results have been obtained from a transect off Barbados, where drilling was carded through the surface separating the two opposing
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50 Years of Ocean Discovery: National Science Foundation 1950—2000 plates. Here, measurements of in situ fluid pressures showed that the oceanic sediments in the lower plate are overpressured. Cores from sedimentary strata of the upper plate showed strong evidence of tectonic kneading of sediments in the accretionary prism and also the presence of fluid escape channels carrying waters squeezed from the deforming sediments upward to the seafloor. Several transects across the entire active margin complex (trench, forearc, volcanic arc, backarc basin, and remnant arc) have documented not only the materials in this system, but the timing and rates of development in them as well as the contrasting deformational styles in zones with thickly sedimented compared to near-barren trenches. THE FUTURE Now the drilling program is approaching another crossroads. In 2003, unless something new happens, drilling may well cease or be replaced by a quite different program strongly resembling OMD in its scientific objectives. Planning continues for the five-year ODP time between now and then. One drilling prospect has been opened by the Japanese announcement that they intend to construct, at their own expense, a large ship ("Godzilla Maru") fitted out for riser drilling. Some tens of millions of dollars are said to be in the pipeline for design studies for a ship that will cost upwards of $500 million to build and have daily operating costs of something like $130,000 (about three times the JOIDES Resolution). Drilling from this ship during the first few years is planned to be in waters not more than about 2.5 km deep (shallower than most of the spreading ridge system, let alone the main ocean floor), and the ship would work for much of this time close to Japanese home waters, where a number of problems in the structure, hydrology, and seismicity of thickly sedimented active margins are available. Proposals for specific riser drilling objectives are now being formulated. As for nonriser, ODP-style drilling, NSF is said to be looking at the possibilities of funding a Resolution-type vessel for operations post-2003, in addition to paying its share of the Japanese riser ship daily costs. The U.S. COMPOST-II Committee on Post-2003 Scientific Ocean Drilling issued a report in 1996 endorsing a two-ship program. The active scientific community is busy writing proposals to be discussed at a planned international conference in 1999. Urgent messages are in the air that we should all be demonstrating support for and submitting proposals for work in an Integrated Ocean Drilling Program (IODP) to follow ODP, and using two ships, riser and nonriser. We appear still to lack concordance on major new scientific initiatives, initiatives of the scope and imagination of the original Mohole project, initiatives that can capture the attention of large segments of not only the scientific community but the public and Congress as well. To arms! Enlist now! ACKNOWLEDGMENTS I thank Bruce Malfait for the data on year-by-year expenditures for drilling projects. Both he and Walter Munk made constructive suggestions on an early draft of the paper. D.K. Van Keuren kindly allowed use of his unpublished paper on the history of the Mohole Project. W.W. Hay made constructive suggestions for improvement of an earlier draft of the manuscript. REFERENCES Emiliani, C., and J.I. Jones. 1981. A new global geology: Appendix III: report on Cruise LOCO 6301 with Drilling Vessel Submarex (a reprinting of the report made to NSF). Pp. 1721-1723 in C. Emiliani (ed.), The Sea, volume 7: The Oceanic Lithosphere. John Wiley, New York. Greenberg, D.S. 1964. Mohole: The project that went awry. Science 143:115-119. Larson, R.L., and 29 others. 1997. ODP's Greatest Hits. Brochure issued by Joint Oceanographic Institutions, Washington, D.C. 28 pp. Malfait, B., and 51 others. 1993. 25 years of ocean drilling. Oceanus 36(4):5-133. Reiche, P. 1945. A Survey of Weathering Process and Products. Univ. New Mexico Pubs. Geol. No. 1. 87 pp. Shackleton, N.J., M.A. Hall, and A. Boersma. 1984. Pp. 599-612 in T.C. Moore, Jr., and Rabinowitz, P.D. et al., (eds). Initial Reports of the Deep Sea Drilling Project, 74. U.S. Government Printing Office, Washington, D.C. Solow, H. 1963. Fortune (May):138-141,198-199, 203-204, 208-209. Van Keuren, D.K. 1995. Drilling to the mantle: Project Mohole and federal support for the Earth sciences after Sputnik. Unpublished text of paper delivered at Annual Meeting, History of Science Society, Minneapolis, Minn. 13 pp.
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