Drilling to Decipher Long-Term Sea-Level Changes and Effects — A Joint Consortium for Ocean Leadership , ICDP , IODP , DOSECC , and Chevron Workshop

One of the most societally relevant objectives of the Earth sciences is to understand the history and impact of global sea-level (eustatic) fluctuations at different timescales. Over a third of the world’s population lives within 100 km of a coastline. One-tenth of the global population and thirteen  percent of the world’s urban population live in coastal areas that lie within just 10 m above sea level (the Low Elevation Coastal Zone or LECZ), which covers only two percent of the  world’s land area (McGranahan et al., 2007). Reconstruction of global mean sea level since 1870 indicates a twentieth cen tury rate of sea-level rise of 1.7 ± 0.3 mm yr−1 and a significant acceleration of sea-level rise of 0.013 ± 0.006 mm yr−2 (Church and White, 2006), in part due to anthropogenic influences. Satellite observations in the last decade show that the rates have increased since 1993 to 3.3 ± 0.4 mm yr  -1


Introduction
One of the most societally relevant objectives of the Earth Earth arth sciences is to understand the history and impact of global sea-level (eustatic) fluctuations at different timescales.Over a third of the world's population lives within 100 km of a coastline.One-tenth of the global population and thirteen -tenth of the global population and thirteen tenth of the global population and thirteen thirteen percent of the world's urban population live in coastal areas that lie within just 10 m above sea level (the Low Elevation Coastal Zone or LECZ), which covers only two percent of the two percent of the percent of the world's land area (McGranahan et al., 2007).Reconstruction of global mean sea level since 1870 indicates a twentieth cen-twentieth cen-th century rate of sea-level rise of 1.7 ± 0.3 mm yr −1 and a significant acceleration of sea-level rise of 0.013 ± 0.006 mm yr −2 (Church and White, 2006), in part due to anthropogenic influences.Satellite observations in the last decade show that the rates have increased since 1993 to 3.3 ± 0.4 mm yr ± 0.4 mm yr ± 0.4 mm yr 0.4 mm yr 0.4 mm yr yr yr -1 (Cazenave and Nerem, 2004).Remote-sensing data suggest that ice sheets currently contribute little to sea-level rise.Best estimates are that sea level could rise by as much as 50 cm in the next 100 years (IPCC, 2007).However, dynamical instabilities in response to climate warming may cause faster ice-mass loss (Cazenave, 2006).Rahmstorf et al (2007) show that sea-level observations are tracking at the high end of the IPCC estimates and conclude that 80 cm, and perhaps >1 m, is the most likely global rise by 2100.In some of the most heavily populated areas (e.g., the U.S. Atlantic seaboard) relative sea-level rise exceeds 4 mm yr yr yr -1 (Psuty and Collins, 1996) due to combined effects of global sea-level rise and subsidence.While such rates are gradual on a human timescale, the geological record shows that they can increase rapidly and dramatically (e.g., >2 m in a century�� Fairbanks, 1989�� Bard et al., 1990)�� in addition, the retreat of shorelines can be erratic and rapid even under conditions of moderate global rises of sea level.
The geologic record provides an opportunity to quantify the timing, amplitudes, rates, mechanisms/controls, and effects (stratigraphic response) of eustatic change (Figs. 1 and 2).This information, in turn, provides a baseline for predicting future global sea-level changes and assessing anthropogenic influences.In order to understand the effects of potential future eustatic trends, it is vital to document how the Earth system has operated during past abrupt climate Earth system has operated during past abrupt climate arth system has operated during past abrupt climate changes (e.g., the last and penultimate deglaciations) and under past conditions of extreme climate forcing, and to con-, and to con-and to con-strain the eustatic response to elevated CO 2 levels.For example, determining how sea level varied in response to level varied in response to level varied in response to past intervals of global warming-e.g., marine isotope chrons -e.g., marine isotope chrons e.g., marine isotope chrons 5e (Thompson and Goldstein, 2005), 11 (Droxler et al., 2003), 31 (Scherer et al., 2008)�� "mid " Pliocene warmth (Draut "mid " Pliocene warmth (Draut "mid " Pliocene warmth (Draut et al., 2003), the middle Miocene climate optimum, the early Eocene (Zachos et al., 2001), and the Late Cretaceous (Abreu et al., 1998�� Miller et al., 2005a, b�� Bornemann et al., 2008)will provide a means to evaluate the eustatic impact of future climate trends.Understanding how processes/mechanisms yield specific eustatic responses will therefore improve our understanding of the societal impact of the resulting sea-level of the societal impact of the resulting sea-level the societal impact of the resulting sea-level changes.Furthermore, understanding how process interactions produce the preserved stratigraphy of beds and sequences is fundamental to deciphering the long-term geologic and climatic history recorded by sediments in a variety of marine sedimentary basins.These environments are also economically and strategically important-testing predictive sequence models has a proven potential for identifying a proven potential for identifying proven potential for identifying oil and gas resources and for ground water/pollution remediation issues.Such research also helps to achieve the long-sought goal of predicting margin lithologies in the absence of drilling, a concept pioneered by the Exxon group (Vail and Mitchum, 1977).Finally, constraining the history of sea-level change provides data of direct use to researchers in other disciplines because of the relationships between Workshop Reports timeframes and depositional settings, including siliciclastic, carbonate, and mixed systems (Fig. 3).Fundamental to the , and mixed systems (Fig. 3).Fundamental to the and mixed systems (Fig. 3).Fundamental to the approaches recommended by our workshop are as follows: 1) as follows: 1) : 1) to enhance our understanding of eustatic timing, amplitudes, enhance our understanding of eustatic timing, amplitudes, rates, and stratigraphic response during the icehouse period, , and stratigraphic response during the icehouse period, and stratigraphic response during the icehouse period, when glacioeustasy is known to be the principal eustatic mechanism, and�� 2) to begin an aggressive program to under-to begin an aggressive program to under-begin an aggressive program to understand the mechanisms responsible for greenhouse eustasy and how they relate to climatic trends and stratigraphic response.

Salt Lake City �orkshop
Various groups related to the Ocean Drilling Program (ODP) have developed strategies for studying eustasy on orbital (>19 kyr) and longer timescales (Imbrie et al., 1987�� Watkins and Mountain, 1990�� JOIDES, 1992).These strategies have begun to be implemented with drilling transects across the New Jersey margin (ODP Legs 150, 150X, 174A, and 174AX), the Bahamas (Leg 166 and mission-specific platform sites) and a targeted sea-level amplitude experiment on the Marion Plateau, Northeast Australia (Leg 194).However, an effective, coordinated strategy requires that additional margin transects be drilled.In addition, it has been fifteen years since the last of these groups�� the Sea-Level Working Group (JOIDES, 1992), discussed goals and strategies of sea-level research.Recent drilling advances, including the use of mission-specific platforms (MSP) offshore and joint onshore-offshore drilling (e.g., IODP Expedition 313), together with new views on the roles of tectonics and sediment dynamics, required that the scientific community reevaluate the fundamental assumptions of sea-level studies.
As a follow-up to the SEALAIX Symposium ("Sea-Level ("Sea-Level "Sea-Level Changes: Records, Processes and Modeling", September , September September 2006, Presqu'île de Giens, France), an international work- ), an international work-, an international workshop of more than fifty participants was held in Salt Lake fifty participants was held in Salt Lake participants was held in Salt Lake City, Utah The purposes s of the workshop were 1) to review results of ODP and early ere 1) to review results of ODP and early 1) to review results of ODP and early to review results of ODP and early review results of ODP and early IODP drilling for sea-level objectives�� 2) to reevaluate princi-to reevaluate princi-reevaluate principles and strategies for constraining genetic links between eustatic change and Earth system processes and for defining the relative roles of eustasy versus local processes in building the stratigraphic record�� and 3) to identify possible geo-to identify possible geo-identify possible geographical areas and time-intervals for future IODP drilling transects.Presentations about IODP, ICDP, and DOSECC , and DOSECC and DOSECC were followed by keynote scientific talks and a series of short, three-minute presentations by participants.Breakout groups subsequently focused on the relationship between recorded sea-level cyclicity and eustatic mechanisms through time, and on deciphering the stratigraphic response to , and on deciphering the stratigraphic response to and on deciphering the stratigraphic response to on deciphering the stratigraphic response to deciphering the stratigraphic response to eustasy through a sedimentary process approach in both eustasy and ice-sheet growth and decay, nutrients and ocean productivity, carbon storage, and ocean chemistry.
, and ocean chemistry.and ocean chemistry.
The Miller et al. (20 05a) back-stripped sea-level curve was smoothed with a 21-point Gaussian convolution filter to generate the smooth black curve.The pink box at 11 Ma is a sea-level estimate derived from the Marion Plateau (John et al., 2004).Light green boxes indicate times of spreading rate increases on various ocean ridges (Cande and Kent, 1992).Dark green box indicates the opening of the Norwegian-Greenland Sea and concomitant extrusion of basalts (Modified from Browning et al., 2008).(Harrison, 1990).Sea level is important for the .Sea level is important for the Sea level is important for the Sea level is important for the ea level is important for the study of tectonic processes, because it is the datum against which vertical tectonic movements are measured.

1) Refining timing, amplitudes, and mechanisms of icehouse
, and mechanisms of icehouse and mechanisms of icehouse (Oligocene-Recent) eustatic change.ODP results to date have demonstrated that global sea-level changes over the past 42 myr can be explained, in part, by growth and decay of continental ice sheets (glacioeustasy�� Miller et al., 1996�� Eberli et al., 1997�� Eberli, 2000).Such drilling has principally addressed the timing of sea-level change and has also determined that sequence boundaries indeed represent timelines as predicted in the sequence stratigraphic model (Eberli et al., 1997�� Betzler et al., 2000).
However, our understanding of how climate change influences sea level, even during this "icehouse" period of large level, even during this "icehouse" period of large level, even during this "icehouse" period of large ice sheets, is incomplete.In particular, there are still uncertainties surrounding the hierarchy of eustatic and sequence periodicities, and particularly the origins of sequences with durations of >1 myr, which do not appear to conform to long-period (1.2 myr and 2.4 myr) astronomi-myr and 2.4 myr) astronomi-and 2.4 myr) astronomical variations (Miller et al., 2005a).It is surprising that modulation by the 1.2-myr-long tilt cycle is not a dominant periodicity in icehouse sea-level records, because it has been shown that the short 41-kyr tilt cycle domi--kyr tilt cycle domi-kyr tilt cycle dominates the ice-volume record of the past 34+ my (Zachos et al., 2001).The 2.4-myr very long eccentric--myr very long eccentric-myr very long eccentricity cycle dominates carbon isotopic records throughout the Cretaceous to Cenozoic through its effects on the carbon system, , which might be expected to be influenced by sea-level changes.Spectral analysis of the Miller et al. (2005a) sea-level records shows that variations occur with an as-yet-unexplained, persistent 3-myr beat that may be either an -myr beat that may be either an myr beat that may be either an interference between the 1.2 myr myr and 2.4 myr cycles or be an artifact of an undersampled sea-level signal.This intriguing relationship bears investigation because the million-year-scale sea-level signal can be shown to be a composite of 41-kyr tilt cycles, at least for the icehouse world (Miller et al., 2005a).
Moreover, sea-level amplitudes during this period have not yet icehouse and greenhouse worlds.Breakout Group Two was further subdivided into siliciclastic and carbonate groups.In addition to identifying scientific questions and objectives, the groups were also asked to consider drilling program design, potential target areas, and technology requirements , and technology requirements and technology requirements (onshore and offshore).

Objective 1: Determining Eustatic Mechanisms
Understanding the mechanisms that drive eustatic change requires knowledge of the timing, amplitudes, and rates of , and rates of and rates of global sea-level change (Fig. 1).It also requires information on climate and paleoceanography, mainly derived from proxy records (Fig. 4), and tectonic mechanisms that control the volume of the oceans.In turn, such quantification of eustatic change will contribute to other areas of the Earth sciences Earth sciences arth sciences by helping to constrain such processes as ice-sheet growth and decay, ocean temperatures, carbon burial, and inorganic carbon precipitation in carbonates (Fig. 4) as well as global Schematic figure illustrating how deep-sea geochemical records can be used to understand mechanisms of past eustatic changes by analogy to the modern ocean.During atmospheric transport from low to high latitudes water vapor becomes progressively more depleted in δ 18 O, and ice sheets have a very negative δ 18 O signature.The isotopic composition of high latitude ice sheets is a function of the magnitude of isotopic fractionation within the hydrological cycle, which in turn is dependent on pCO 2 and temperature, and could vary over geological timescales.Consequently, the δ 18 O composition of seawater (δ 18 O sw ) is largely a function (ƒ) of ice volume and regional evaporation and precipitation processes.Reconstructing δ 18 O s w in different ocean basins will highlight times of eustatic changes due to ice-volume fluctuations, as well as provide a record of the timing and amplitude of these changes.δ 18 O sw can be derived by combining the isotopic composition of foraminiferal calcite ("δ 18 O Foraminifer ") with independent temperature proxies (e.g., Mg/Ca for deep-water temperature, and TEX86 and alkenones for surface water temperatures).Subsequently, correlation of excursions in δ 18 O sw to more positive values with independent evidence of sea-level change can be taken as support for the operation of a glacio-eustatic mechanism.Open ocean sites can also provide more indirect evidences of the relative role of glacio-eustasy through geological time.The presence of ice rafted debris (IRD) in open ocean sediments indicates iceberg transport, and thus a significant volume of ice at sea level along continental margins.The waxing and waning of ice sheets is a function of high-latitude temperatures and atmospheric pCO2, which also impact the position of the carbonate compensation depth (CCD).Fluctuations in the CCD are recorded as variable carbonate contents (%CaCO 3 ) within deep-sea sediments and could be used as indirect evidence of glacial/interglacial alternations, as CCD is sensitive to changes in carbonate burial on the shelf.Finally, eustatic variations control the area of shelf submerged, thus indirectly impacting the type of rocks subjected to continental weathering, the amount of nutrients and carbonate ions delivered to the coastal ocean, and the area available for carbon burial on continental margins.Some isotope systems (Os, Nd, and Sr) are available as proxies of continental weathering.The weathering processes ultimately have feedbacks on the carbon cycle, climate, and glacioeustasy.been adequately constrained.
One approach for determining eustatic amplitudes that has been applied with success to applied with success to the New Jersey margin involves combining sequence stratigraphic and back-stripping analyses (Fig. 5�� Kominz and Pekar, 2001�� 2002�� Pekar and Kominz, 2001).The resulting sea-level curve (Fig. 2�� Browning et al., 2008) repre-2008) repre-) represents the best current estimate, but it is still incomplete because lowstand sediments were not recovered, introducing uncertainty to estimated amplitudes.Possibly as a result, the Miocene part of the New Jersey sea-level curve does not appear to correspond as well to the globally recognized stratigraphic signature of the Neogene as other eustatic curves (Fig. 6�� Bartek et al., 1991).Furthermore, the New Jersey curve also differs from  18 O records that have been corrected for paleotemperature and are therefore an improved record of ice-volume fluctuations (Billups andSchrag, 2002�� Lear et al., 2004), and which do correspond well to the stratigraphic signature of the Neogene (Fig. 6).
Finally, estimates of the amplitudes of eustatic change from one-dimensional back-stripping at one location (e.g., New Jersey�� Miller et al., 2005a�� Kominz et al., 2008�� 2008���� Browning et al., 2008) requires supplemental application of 2008) requires supplemental application of ) requires supplemental application of this procedure to strata on distant continents (e.g., Carter et al., 1991).Future scientific drilling must therefore include additional drilling for icehouse eustatic objectives.Ideally, two-and three-dimensional back-stripping procedures would -and three-dimensional back-stripping procedures would and three-dimensional back-stripping procedures would improve amplitude estimates (Kominz and Pekar, 2001).These approaches require good regional seismic coverage and a well-constrained, regional, sequence stratigraphic framework, including data that can only be obtained from cores.
2) Challenging the paradigm of a stable, ice-free "greenhouse" climate.Though we are beginning to unlock the mysteries of icehouse sea-level changes, our understanding of eustatic change during the preceding "greenhouse" world of the Triassic to early Eocene is controversial.For example, the Late Cretaceous has been reconstructed as a greenhouse world with warm polar climates (Bice et al., 2006), and most studies have assumed the absence of polar ice sheets (e.g., Huber et al., 1995).However, the work of Exxon Production Research Company (Vail andMitchum, 1977�� Haq et al., 1987) and more recent publications (Van Sickel et al., 2004�� Miller et al., 2003, 2005a, b�� b�� b�� Bornemann et al., 2008) have indicated large (tens of meters), short-period (<1 myr) Late Cretaceous global sea-level (eustatic) fluctuations (Fig. 2).In addi-   tion, second-(~10 my), third-(1-5 my) and fourth-(~0.5 my) order sequences can apparently be correlated widely between tectonically active and passive regions (e.g., Western Interior Seaway, Europe and India�� Gale et al., 2002) suggesting eustatic control.Glacioeustasy is the only known mechanism for producing such large, rapid eustatic changes (Donovan and Jones, 1979�� Fig. 1).
There are two solutions to this enigma: eustatic mechanisms are not fully understood, or there were ice sheets throughout much of the Triassic to early Eocene (Stoll and Schrag, 1996, 2000�� Abreu et al., 1998�� Miller et al., 2003, 2005a,b�� Bornemann et al., 2008).ODP and ICDP drilling onshore New Jersey (Leg 174AX) have provided a detailed record of Cretaceous to early Eocene sequences.This record quantifies high amplitudes and rates of eustatic change (>25 m in <1 myr) in the Late Cretaceous to Eocene greenhouse world.Based on this sea-level history, Miller et al. (2003Miller et al. ( , 2005a, b) , b) have proposed that ice sheets existed for geologically short intervals (i.e., lasting ~100 ky) during the Late Cretaceous-Eocene.This view can be reconciled with previous assumptions of an ice-free Greenhouse World.World.orld.Eustatic changes on the 10 6 yr scale were typically ~15-30 m in the Late Cretaceous-Eocene (ca.100-33.8Ma), suggesting growth and decay of small-to medium-sized (10-15 x 10 6 km 3 ) ephemeral Antarctic ice sheets (Miller et al., 2005a, b).b).b).
However, although such indirect evidence for ephemeral ice sheets is growing, there is, as yet, no physical evidence for Late Cretaceous to early Eocene ice sheets.A particular difficulty is that other data indicate warm global temperatures for much of this interval-for example, very warm , very warm very warm Albian-Santonian sea surface temperatures in the tropical Atlantic (Forster et al., 2007).There is therefore a need for additional high-resolution stratigraphic records from the greenhouse period.

Objective : Defining Stratigraphic Responses
The stratal geometries that define sedimentary sequences worldwide (Mitchum et al., 1977�� Haq et al., 1987) result from a complex interplay of processes acting in three dimensions.Eustasy competes with climatic and paleoceanographic variations, tectonism, rates and modes of sediment supply, and , and and submarine current activity to influence base level and shoreline position and, hence, stratal formation and preservation.
, hence, stratal formation and preservation.hence, stratal formation and preservation., stratal formation and preservation.stratal formation and preservation.Understanding margin sedimentation, therefore, requires evaluation of multiple processes (including eustasy) at various temporal and spatial scales (Nittrouer and Kravitz, 1995).However, predictive models of the distribution of sediments within unconformity-bounded sequences are based on assumptions about the importance of relative sea-level change (Posamentier et al., 1988�� Vail et al., 1991) that have yet to be adequately tested.
Nevertheless, various industry and academic studies have established that unconformity-bounded sequences are indeed the building blocks of the stratigraphic record (see summary in Christie-Blick and Driscoll, 1995), as first proposed by Vail and Mitchum (1977), and that they can occur in predictable patterns (Fig. 3).For example, the geometric signature of stratigraphic sequences along continental margins for the last 30 Ma involves (Fig. 3C-E (Bartek et al., 1991, Tcherepanov et al., 2008a andb).Although this pattern is widespread and is observed globally in both siliciclastics and carbonates (Fig. 3�� Bartek et al., 1991�� Tcherepanov et al., 2008a andb), the heart of this section, the early and mid-), the heart of this section, the early and mid-, the heart of this section, the early and middle Miocene, has not yet been ground-truthed by drilling.The fundamental assumptions and predictive capabilities of sequence models can only be tested by drilling on shallow continental shelves where (3-D) sedimentary geometries are -D) sedimentary geometries are D) sedimentary geometries are constrained by seismic data (e.g., Kominz and Pekar, 2002).Siliciclastic Margins. .Because of the complex interplay of forcing mechanisms responsible for the stratigraphic record, stratigraphic response must be defined in a diversity of time periods and settings, both tectonic and sedimentary.Siliciclastic sediments are excellent sea-level markers because both highly sensitive indicators of shoreline position, and they are globally widespread.However, it is essen-, and they are globally widespread.However, it is essen-and they are globally widespread.However, it is essen-they are globally widespread.However, it is essen-are globally widespread.However, it is essential to define the specific sedimentary processes (depositional, transportational, and erosional) responsible for the strati-, and erosional) responsible for the strati-and erosional) responsible for the stratigraphic record and to distinguish the responses of these processes to eustasy from their responses to local forcing.This process-based approach must be a component of future drilling-based sea-level research.
The stratigraphic record comprises both surfaces and intervening sedimentary units.In offshore work, surfaces are often defined initially using seismic reflection profiles and later calibrated by coring (Fig. 3).However, only coring can provide the lithofacies and biofacies of the intervening units.Sequence stratigraphic models of such units (Posamentier et al., 1988�� Van Wagoner et al., 1988�� Vail et al., , 1988�� Vail et al., 1988�� Vail et al., ., , 1991) are based on simple assumptions about how facies respond to relative sea-level changes.However, the real world is rendered more complex by the additional influence of local forcing and the three-dimensionality of sequence architectures.Future drilling to investigate the stratigraphic response to eustasy must therefore evaluate the contributions of tectonism and sediment supply.In addition, geometrical variations must be constrained by pre-drilling seismic surveys.
Carbonate Platforms and Margins.Carbonates are excellent sea-level markers because carbonate facies are depthdependent owing to the importance of sunlight to many carbonate-secreting organisms (Eberli et al., 1997�� Camoin et al., 2007a).The relationship of these systems to the carbon cycle allows direct correlation of climatic and eustatic signals (Lear et al., 2004).In addition, multiple dating techniques are available for carbonates (including 14 C, U/Th, Sr, U/Pb, biostratigraphy, and magnetostratigraphy).These enable , and magnetostratigraphy).These enable and magnetostratigraphy).These enable ese enable enable examination of a wide range of frequencies of sea-level change, from millennial scale to tens of millions of years.
Continental margin transects (Fig. 3) have the advantage that their stratigraphic architectures are well constrained by seismic data.However, they are complemented by tropical reefs and atolls, which provide the most reliable geological estimates of relative sea level by dating "fossil sunshine" level by dating "fossil sunshine" level by dating "fossil sunshine" (e.g., shallow dwelling corals).The study of coral reefs is of crucial importance in attempts to resolve the rates of millennial-scale changes in sea level, to clarify the mechanisms that drive glacial-interglacial cycles, and to con-, and to con-and to constrain geophysical models.Coral reefs provide unparalleled records of sea-level amplitudes, particularly for the middle to late Pleistocene.For example, drilling reefs in Barbados has provided a precise estimate for the last eustatic lowstand (120 ± 5 m below present at 18 ka�� Fairbanks, 1989�� Bard ± 5 m below present at 18 ka�� Fairbanks, 1989�� Bard ± 5 m below present at 18 ka�� Fairbanks, 1989�� Bard 5 m below present at 18 ka�� Fairbanks, 1989�� Bard 5 m below present at 18 ka�� Fairbanks, 1989�� Bard et al., 1990�� Peltier and Fairbanks, 2006).Shallow-water drilling of coral reefs remains challenging due to recovery problems, but is necessary to allow study of recent high-resolution climate changes, and it contributes to estimates of the future , and it contributes to estimates of the future and it contributes to estimates of the future it contributes to estimates of the future contributes to estimates of the future s to estimates of the future to estimates of the future behavior of the Earth system on societal timescales.This approach was employed during IODP Expedition 310 off Tahiti (Camoin et al., 2007a, b).
Strategies 1) A focus on both icehouse and greenhouse objectives.
2) Drilling transect approach.This approach, which was was tried and tested on the New Jersey Margin and Great Bahama Bank, with additional IODP drilling planned off New Zealand (Fig. 3), must be enhanced and extended by: • Integration of onshore (e.g., ICDP, DOSECC) and offshore (IODP, DOSECC) drilling.The record of icehouse eustasy is best preserved offshore (e.g., on (e.g., on e.g., on continental margins), but the older, greenhouse, record ), but the older, greenhouse, record , but the older, greenhouse, record tends to be preserved and drillable beneath coastal plains or in onshore basins (e.g., the Western Interior Seaway).Onshore drilling is therefore expected to play an increasingly important role in sea-level studies.
• Drilling of sufficient boreholes, including multiple transects where necessary, and incorporation of sufficient seismic control to constrain three-dimensional stratigraphic architecture.
• Maximizing core recovery by using appropriate drilling technology (e.g., casing, mud) and platforms (e.g., Mission Specific Platforms [MSPs]), and by adapting coring strategies as needed, e.g., by using diamond coring or short advances of the XCB.
3) Recognizing the value of addressing tectonically active settings.For example, the stratigraphic expression of sea-level change in active foreland basins in the U.S. and Canadian western interior basins is superlative, though the stratigraphic records incorporate the effects of both eustasy and tectonism.
Examination of margins with high stratigraphic resolution will allow evaluation of the interaction of eustasy and other processes (e.g., Papua New Guinea�� Jorry et al., 2008), and integration with process-oriented 2008), and integration with process-oriented ), and integration with process-oriented -oriented oriented modeling (e.g., physical and mathematical modeling done as part of the Margins and Intermargins Initiatives).

5) Coordination with drilling operations designed to address
other objectives.Sea-level studies can benefit greatly from the results of research into, for example, paleoclimate, carbon cycling, and ice-sheet dynamics (Fig. 4).Conversely, these research programs will also gain necessary insights from a well constrained eustatic history.

Future �ork
Future IODP drilling for sea-level objectives includes IODP Expedition 313, New Jersey inner shelf drilling scheduled for summer 2009 and IODP Expedition 317, Canterbury Basin, New Zealand, scheduled for November 2008-January 2009.Great Barrier Reef drilling is tentatively planned for 2009.These planned expeditions, and existing IODP proposals (e.g., Maldives, North West Australian Shelf, Gulf of Mexico -Southern Bank, Belize margin, Gulf of Papua), all , all all address icehouse objectives.Such drilling is indeed vital, in particular to constrain icehouse eustatic amplitudes and to calibrate the stratigraphic signature of the Neogene (Bartek et al., 1991).However, the next phase of sea-level studies must include greenhouse objectives.We therefore encourage proponents to prepare and submit sea-level proposals for both offshore and onshore drilling focusing on the greenhouse world.
Consortium for Ocean Leadership provided excellent support before and during the workshop.Dave Zur of DOSECC also provided logistical support.Bryan Bracken of Chevron led an outstanding field trip to Book Cliffs before the workshop, ably assisted by Sunday Shephard and Peter Sixsmith.We express our sincere appreciation for the financial support of the Consortium for Ocean Leadership, ICDP, IODP, DOSECC, and Chevron.This joint support enabled us to , and Chevron.This joint support enabled us to and Chevron.This joint support enabled us to make the workshop a truly international meeting.

Figure 1 .
Figure 1.The mechanisms that generate eustatic change operate on different timescales and generate different magnitudes of sea-level change.These variations in conjunction with proxy data may be used to determine the causal mechanisms of eustatic change.(ModifiedfromMiller et al., 2005a.) (8-10 October 2007) sponsored by Consortium for Ocean Leadership (formerly Joint Oceanographic Institutions), the International Continental Scientific Drilling Program (ICDP), the Integrated Ocean Drilling Program the Integrated Ocean Drilling Program Integrated Ocean Drilling Program (IODP), Drilling, Observation and Sampling of the Earth's Continental Crust (DOSECC), and Chevron.The purposes , and Chevron.The purposes and Chevron.

Figure 2 .
Figure2.Global sea level (light blue) for the interval 7-100 Ma derived by back-stripping five New Jersey coastal plain core holes(Miller et al., 2005a).Revised back-stripped sea-level cur ve (brown) based on a total of eleven New Jersey core holes(Kominz et al., 2008).Global sea level (purple) for the interval 0 -7 Ma derived from δ 18 O, shown in red for a benthic

Figure 3
Figure 3. [A] Middle Atlantic Transect (MAT) off New Jersey, showing drillsites targeting a Paleogene-Pleistocene prograding clinoform succession.MAT has been drilled on the slope (ODP Leg 150; sites not shown) and shelf (Leg 174A; sites 1071-1073 along strike from this profile), as well as on the Coastal Plain (Legs 150X and 174AX).Inner shelf drilling (MAT 1-3) is planned as a Mission-Specific Platform IODP Expedition 213.[B] Line drawing of interpreted Great Bahama Bank sequences drilled during ODP Leg 166 (Sites 1003-1005) and the Bahamas Drilling Project (sites Clino and Unda).[C]The stratigraphic signature of the Neogene represented by: 1) late Oligocene-early Miocene aggradation, backstepping and partial drowning; 2) late early Miocene-early middle Miocene vertical growth or aggradation; 3) earliest middle Miocene downward shift of deposition; 4) late middle Miocene systematic lateral growth (progradation); and 5) late Miocene-early Pliocene re-flooding and aggradation(Bartek et al., 1991; Tcherepanov et al., 2008).[D] The Neogene stratigraphic signature along the West Maldives Inner Sea carbonate margin.[E] Neogene stratigraphic signature in the Gulf of Papua.[F] A future sea-level transect: line drawing of interpreted sequences, offshore Canterbury Basin, New Zealand, showing proposed IODP sites, scheduled for drilling as IODP Expedition 317.

Figure 4 .
Figure 4. Details are given below.

Figure 5 .Figure 6 .
Figure5.In order to determine sea-level change from a marginal marine setting, we recommend at least two-dimensional sequence stratigraphic back-stripping.An example of some of the data required for two-dimensional sequence stratigraphic back-stripping fromKominz and Pekar (2001, 2002)  is shown for illustration.[A] Chronostratigraphic chart for New Jersey coastal plain Oligocene sequences.Solid colors represent highstand systems tracts, while lowstand systems tracts are depicted by patterned colors.Vertical lines show well [B] Sequence model for New Jersey coastal plain Oligocene sequences.Patterns and lines as described above.[C]Geometry of horizons identified in A and B after performing geohistory analysis.Sequences may be identified by colors, which reflect those in A and B, and the labeled offlap break points (inverted triangles) of the final horizon of each sequence.(Modified fromKominz and Pekar, 2002.)