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doi:10.2204/iodp.proc.342.111.2014
Site U14101
R.D. Norris, P.A. Wilson, P. Blum, A. Fehr, C. Agnini, A. Bornemann, S. Boulila, P.R. Bown, C. Cournede, O. Friedrich, A.K. Ghosh, C.J. Hollis, P.M. Hull, K. Jo, C.K. Junium, M. Kaneko, D. Liebrand, P.C. Lippert, Z. Liu, H. Matsui, K. Moriya, H. Nishi, B.N. Opdyke, D. Penman, B. Romans, H.D. Scher, P. Sexton,
H. Takagi, S.K. Turner, J.H. Whiteside, T. Yamaguchi, and Y. Yamamoto2
Background and objectives
Integrated Ocean Drilling Program (IODP) Site U1410 (proposed Site SENR-23A; 41°19.6993′N, 49°10.1847′W; ~3400 m water depth) is a mid-depth site (~2950 meters below sea level [mbsl] paleodepth at 50 Ma) (Tucholke and Vogt, 1979) in the upper mid-depth end of the Expedition 342 Paleogene Newfoundland sediment drifts depth transect (Fig. F1). The site was positioned to capture a record of sedimentation ~1.5 km shallower than the largely sub–carbonate compensation depth (CCD) record drilled at Site U1403 (Figs. F2, F3). The location, well above the average late Paleogene CCD, should be sensitive to both increases and decreases in carbonate burial, whether these reflect variations in dissolution related to changes in the CCD, changes in carbonate production, or variations in background noncarbonate sedimentation. Our primary scientific objectives for drilling Site U1410 were
To obtain an expanded record of lower to middle Eocene drift sedimentation that can be compared directly to the relatively condensed record at Site U1409 drilled on the edge of the drift; To capture fine-scale variations in carbonate preservation and lysocline shifts in carbonate-rich sediment that is ~400 m deeper than at Site U1408; and To evaluate the history of deep water and the CCD on sediment chemistry, grain size, and provenance.
Secondary objectives included the possible recovery of specific Paleogene hyperthermals such as the Middle Eocene Climatic Optimum (MECO) for comparison with the record of these events elsewhere, particularly Sites U1404, U1406, and U1408 along the Expedition 342 depth transect.
Site U1410 is a companion site to Site U1409, where we employed an offset drilling strategy to obtain advanced piston corer (APC) records through a thicker section of the same sediment drift. Drilling a similar pair of sites (U1407 and U1408) showed that the more expanded Site U1408 record is essentially a record similar to that at Site U1407 but with much more clay and a somewhat younger uppermost sediment record. We found largely the same geometry in the J-Anomaly Ridge sites, where the center of the drift has a massively expanded record of the same geological intervals that is present in relatively condensed sections at the ends of the drift. Hence, we expected that coring at Site U1410 would recover a sequence with more clay but otherwise similar gross stratigraphy to the more condensed companion Site U1409.
The primarily calcareous sequence expected at Site U1410 should record changes in ocean alkalinity and carbonate production. Sites U1403 and U1404 were mainly positioned to capture large-amplitude CCD deepening events such as the carbonate budget “overshoots” that are thought to be associated with the most extreme climate perturbations of the Cenozoic, such as those involved with the Paleocene/Eocene Thermal Maximum (PETM), the late middle Eocene, and the Eocene–Oligocene transition (EOT) (see the “Site U1403” and “Site U1404” chapters [Norris et al., 2014b, 2014c]). Transient shoaling of the CCD in generally carbonate rich sequences should be recorded at Site U1410 by decreases in carbonate preservation and decreasing carbonate content relative to clay or biosiliceous sediment, as we have already observed at Sites U1404–U1408. As an upper mid-depth site on the Newfoundland depth transect at ~3400 mbsl, Site U1410 was positioned to allow us to reconstruct small changes in carbonate content between the records of Sites U1406 (3850 mbsl) and U1408 (3022 mbsl) and should have a few intervals in which the sediment is 80%–90% carbonate but also intervals in which carbonate abundance falls in the record. Carbonate content was expected to be generally higher at sites in shallower water depth, such as the majority of the sites located on Southeast Newfoundland Ridge, but less than our shallowest depth Sites U1407 and U1408.
The relatively high carbonate contents anticipated in sediment at Site U1410 should permit the construction of detailed stable isotope records and calcareous microfossil biostratigraphy that can be tied by physical property records and magnetochronology to Sites U1403–U1406 further downslope and Sites U1407 and U1408 upslope. Ties between sites on Southeast Newfoundland Ridge and those on J-Anomaly Ridge will allow the isotope stratigraphy and biochronology developed for Sites U1406–U1408 to be exported to the lower ends of the depth transect.
Ultimately, the goal is to use the combination of the lower and middle Eocene record at Sites U1407–U1410 and the younger Paleogene record at Site U1406 to produce composite stable isotope and carbonate content records that can be tied to the more intermittent geochemical records at Sites U1403–U1405. Our aim is to match carbonate-rich intervals across all of the J-Anomaly sites with the sites on Southeast Newfoundland Ridge to create an orbital-resolution record of fluctuations in ocean chemistry and deep water origins.
Site U1410 was proposed during Expedition 342 to test the hypothesis that there are several acoustically transparent drift packages on the Southeast Newfoundland Ridge that correlate to similar but more persistently developed reflector units on the toe of J-Anomaly Ridge (cored at Site U1403). Drilling on J-Anomaly Ridge showed that the uppermost acoustically transparent unit is of middle Eocene to early Miocene age and is separated from a thin, lower, acoustically transparent interval by a set of very well developed reflectors of early Eocene to Cretaceous age. In turn, drilling at Sites U1407–U1409 showed that drift sedimentation begins in the middle early Eocene. We hope to use Site U1410 to determine the onset of drift sedimentation in a record that is likely to have a higher fidelity than the relatively condensed records on the fringes of the sediment drifts.
We hypothesized that Site U1410 would provide an expanded record of primarily calcareous ooze and chalk of rough age-equivalence to sites in deeper water on J-Anomaly Ridge. In particular, Site U1410 should provide a high–deposition rate record of the middle and early Eocene as a counterpart to the largely sub-CCD record at Site U1403 and the shallower records at Sites U1407 and U1408. The combination of these records will improve age and water depth control on the behavior of the CCD in the North Atlantic during this key interval.
Publication: 3 March 2014
MS 342-111
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