Expedition 317 investigated the record of global sea-level change (eustasy) within continental margin sedimentary sequences and how eustasy interacts with local forcing to produce preserved sedimentary architectures.

No abstract

Sedimentary organic matter is a potential indicator of paleoenvironments. In this study we examine the relationship among composition of kerogen (insoluble organic matter), sedimentary environments, and sea-level changes in Miocene to Pleistocene sediments of the Niigata and Akita backarc basins, central Japan. Our primary analytical tool is a ternary diagram with apexes consisting of woodycoaly organic matter, herbaceous with pollen and spores, and amorphous organic matter (AOM) with alginite (organic-walled marine microfossils). The composition of kerogen plots into distinct regions on the ternary diagram: fluvial to estuarine, prodeltaic, shelf, slope and basin-floor submarine fans, and distal basin-floor sediments. The fluvial and estuarine sediments have high proportions of woody-coaly and herbaceous organic matter with pollen and spores, and a lesser proportion of AOM ؉ alginite, because pollen and spores were mainly deposited in estuaries. Because abundant coarse-grained, terrigenous organic matter was supplied by delta distributaries, the prodeltaic sediments have high proportions of woody-coaly organic matter. The composition of kerogen in the shelf sediments is similar to the kerogen in slope and basin-floor submarine-fan sediments, as plotted on the ternary diagram. Both kinds of kerogen accumulations have high proportions of woody-coaly organic matter and AOM with alginite and lesser proportions of herbaceous organic matter with pollen and spores. This relationship suggests that turbidity currents supplied the terrigenous sediments. The sediments on the distal basin-floor contain high proportions of AOM.Each pattern in the ternary diagram reflects a difference in hydrodynamic behavior, distance from land, and the supply of terrigenous organic matter. The sub-ternary diagram, which has apexes of WFA (weakly fluorescent amorphous organic matter), NFA (nonfluorescent amorphous organic matter) ؉ FA (fluorescent amorphous organic matter), and alginite, further suggests the origin of AOM. The NFA in shelf sediments and WFA in distal basin-floor sediments are inferred to consist of terrestrial higher plant and marine organic matter, respectively. A ␦ 13 C value of kerogen rich in NFA (Ϫ24.6 and Ϫ27.3‰) suggests land plants, whereas kerogen rich in WFA (Ϫ20.0 to Ϫ23.6‰) suggests marine plankton. These inferences agree with those derived from the sub-ternary diagram. Furthermore, compositional changes of the kerogen in turbidites reflect relative sea-level changes, as seen by shifts in compositions on the ternary diagram. The use of ternary diagrams like those used here is recommended for future studies of kerogen, depositional environment, and sea-level relationship.

Integrated Ocean Drilling Program Expedition 317 drilled progradational sequences on the continental shelf and upper slope in the offshore Canterbury Basin on the eastern margin of the South Island of New Zealand. We measured δ 18 O and δ 13 C values in benthic foraminifers (Nonionella flemingi) from the upper 550 meters below seafloor at slope Site U1352. The results of the oxygen isotope ratios in conjunction with nannofossil datum levels allow identification of most of the marine isotope stages (MIS) shown in the LR04 stack since MIS 63 (1.76 Ma). Materials and methods A total of 343 samples were taken from the upper 550 m in Hole U1352B. The cores consist mainly of unconsolidated mud intercalated with fine sand layers. Sediment was sampled using 20 cm 3 plastic tubes. Freeze-dried samples were washed over 125, 250, and 500 µm stacked sieves. From several to ~40 tests of benthic foraminifer N. flemingi were picked from subsamples of the medium to fine sand-size fraction (125-500 µm). Three to six well

We evaluate lithofacies, chronology, and seismic sequences from the Canterbury Basin, New Zealand passive continental slope (Integrated Ocean Drilling Program [IODP] Expedition 317 Site U1352 and environs) and compare this with slope sequences from the New Jersey passive margin. Our goal is to understand continental slope sedimentation in response to glacio-eustasy and test the concepts of sequence stratigraphy. High-resolution geochemical elemental and lithostratigraphic analyses were calibrated to a chronology constructed from benthic foramininferal oxygen isotopes for the past ~1.8 m.y. We identify lithofacies successions by their unique geochemical and lithologic signature and correlate them with marine isotope stages (MIS) at Milankovitch 100 k.y. (MIS 1-12) and 41 k.y. (MIS 13-63) periods. Eight seismic sequence boundaries (U13-U19) were identified from high-resolution multichannel seismic data, providing a seismic stratigraphic framework. Except for MIS 1-5 and MIS 54-55, there are 2-16 MIS stages and a comparable number of lithofacies contained within each seismic sequence, indicating that it took one to several glacio-eustatic cycles to build each seismic stratigraphic sequence. These findings support prior results obtained by the Ocean Drilling Program (ODP) Leg 174A on the New Jersey continental slope. On both margins, there is a strong correlation between seismic sequences, lithofacies, and MIS, thus linking them to glacio-eustasy. However, the correlation between MIS and seismic sequences is not one-to-one, and Pleistocene seismic sequences on the two margins are not synchronous. Local conditions, including differences in sedimentation rates and creation of accommodation space, strongly influenced sediment preservation at each location, revealing that high-frequency Pleistocene seismic sequences need not correlate globally.