Site 762

Abstract

1 Haq, B. U., von Rad, U., et al., 1990. Proc. ODP, Init. Repts., 122: College Station, TX (Ocean Drilling Program).2 Shipboard Scientific Party is as given in the list of Participants preceding the contents. 112°15.24'E, water depth 1360 m) is located on the western part of the central Exmouth Plateau. In this area a thick Triassic paralic section is unconformably overlain by a thin upper Jurassic marine succession and lower Cretaceous prodelta sediments, which is in turn covered by mid-Cretaceous to Cenozoic pelagic carbonates. This site was chosen to provide documentation of the Cretaceous and Tertiary depositional sequences and cycles of sea-level change in an area with excellent seismic-stratigraphic control. Together with Site 763 (which is closer to the source of terrigenous influx), this site was expected to furnish data that will help separate the tectonic, sedimentary, and eustatic signals for testing sequence stratigraphic models. Site 762 was drilled to a total depth (TD) of 940 m and recovered a section ranging in age from Berriasian to Quaternary, with an overall recovery rate of 75%. The upper 182 m of foraminifer-nannofossil and nannofossil oozes of late Oligocene through Quaternary age are underlain by nannofossil oozes and chalks of early Paleocene to late Oligocene age with numerous intervals of cyclic color bands. The Cretaceous/Tertiary boundary occurs at 554.6 mbsf, within the nannofossil chalk, and is marked by a slight color change. HOLE 762CDateThe chalky lithofacies is present to 838.5 mbsf. Clay content is generally greater in the lower part of the section; age ranges from early Albian to latest Maestrichtian. The Cenomanian chalks include abundant pressure-solution contacts (stylolites). The Cenomanian/Turonian boundary is well represented by an interval rich in organic material. Below 838.5 mbsf, a 10-m-thick unit of black shales (equivalent to Muderong Shales on land) of early Aptian age probably represents a period of anoxia on the plateau in an open-marine setting. The mid-Cretaceous to Paleogene section is essentially complete and in large part well preserved. The black shales are unconformably underlain by silty claystones and prodelta claystones of Berriasian to early Valanginian age (equivalent to the Barrow Group on land), which extend to the TD of 940 mbsf. A belemnite-rich horizon below the black shales might represent the beginning of a major global late Neocomian transgression. The site yielded an expanded Maestrichtian-Paleocene succession with well-preserved calcareous microflora and fauna, suitable for detailed magneto-biostratigraphic and stable-isotopic work. Nannofossils, and to some extent, foraminifers, were useful in assigning ages to the pre-Tertiary section. Rich dinoflagellate assemblages were found in the Aptian black shales.Three logging runs with the seismic-stratigraphic, geochemical, and neutron-density tools generated logs for detailed correlations and for safety considerations regarding the subsequent drilling of Site 763. Careful monitoring of hydroca...

Multi-elemental Statistical Features of Early Paleogene Sediments from the Mid-latitude Eastern Indian Ocean

“…Since then, the Cenozoic sedimentary environment has corresponded to an open-ocean setting (Bilal & McClay, 2022;Haq et al, 1992). The present-day water depth of this site is 1360 m (Haq et al, 1990; Figure 1b), and the paleodepth of the early Paleogene is comparable to that reported today (1000-1200 m; Haq et al, 1992;Jones & Wonders, 1992).…”

“…The lithology of the early Paleogene section of Site 762C mainly consists of nannofossil chalk that was deposited above the CCD and has been divided into three lithologic subunits (Unit II, Subunit IIIA, and Subunit IIIB; Haq et al, 1990;…”

Reconstructing Eocene Eastern Indian Ocean Dynamics Using Ocean‐Drilling Stratigraphic Records

“…Hole 762C (19°53.23ˊS, 112°15.24ˊE) is located on the western part of the central Exmouth Plateau (northern Carnarvon Basin) at a present-day water depth of 1,360 m ( Figure 1) (Haq et al, 1990). The Cenozoic XU ET AL.…”

“…Hence, the sedimentary noise model is assumed to be largely unaffected by unstable sedimentation and volcanism. Postdepositional clay mineral diagenesis could also be a source for noise-level variability, however, the clay mineralogy of Site 762 chiefly reflects humid-climate weathering products, only marginally affected by clay mineralogy diagenesis (Haq et al, 1990). By exclusion, the sedimentary noise modeling result is thus considered to be mainly influenced by sea-level.…”

“…Hole 762C (19°53.23ˊS, 112°15.24ˊE) is located on the western part of the central Exmouth Plateau (northern Carnarvon Basin) at a present-day water depth of 1,360 m (Figure 1) (Haq et al, 1990 sedimentary environment corresponds to an open-ocean setting that has been tectonically quiescent since the mid-Cretaceous (Haq et al, 1992). A detailed cyclostratigraphic age-depth model has been recently constructed for the Plio-Pleistocene (Auer et al, 2020;Stuut et al, 2019).…”