Composition and stable isotope record of bulk sediment and belemnite rostra from ODP Hole 122-761C


Autoria(s): Bralower, Timothy J
Cobertura

LATITUDE: -16.737000 * LONGITUDE: 115.535000 * DATE/TIME START: 1988-07-21T09:00:00 * DATE/TIME END: 1988-07-25T02:00:00

Data(s)

13/11/1992

Resumo

A sedimentary sequence documenting the early history of the proto-Indian Ocean was drilled at Site 761 on the Wombat Plateau, northwest Australia. Directly above the post-rift unconformity, two lithologic units were recovered which reflect deposition in incipient oceanic environments. The lower unit, composed of sandstone, contains abundant belemnites and a few lenses composed of low-diversity coccolith assemblages. The second unit, composed of chalk, contains abundant calcispheres, thoracospheres, low-diversity coccolith assemblages, and a few radiolarians. Belemnites and organisms that produced calcispheres and thoracospheres are thought to be opportunistic. Their abundance, and the absence of a normal marine fauna and flora, reflects an unstable early ocean environment. Stable oxygen and carbon isotopic data for the two units fall into almost separate fields. Heavy delta18O values for the belemnites indicate that they have not been affected by recrystallization. Instead, these isotopic values are thought to indicate either the deep, cool habitat of the belemnites or strong vital effects. A bulk chalk delta18O value from the belemnite sand is 3 to 4 parts per mil lighter than the belemnite delta18O values, possibly because it is largely composed of coccoliths which inhabited warmer surface waters. Light delta13C values for bulk calcisphere-bearing nannofossil chalk samples are thought to be a direct result of upwelling or of vital effects. Heavy delta18O values for the chalk unit are interpreted as resulting from upwelling of cool waters. Assemblage and isotopic data are consistent with this incipient ocean basin being highly productive, either as a result of upwelling or runoff of nutrient-rich waters from nearby land areas. However, it is not possible to rule out the control of vital effects on the isotopic signature of any of the fossil groups.

Formato

application/zip, 3 datasets

Identificador

https://doi.pangaea.de/10.1594/PANGAEA.729195

doi:10.1594/PANGAEA.729195

Idioma(s)

en

Publicador

PANGAEA

Direitos

CC-BY: Creative Commons Attribution 3.0 Unported

Access constraints: unrestricted

Fonte

Supplement to: Bralower, Timothy J (1992): Stable isotopic, assemblage, and paleoenvironmental investigations of juvenil-ocean sediments recovered on Leg 122, Wombat Plateau, Northwest Australia. In: von Rad, U; Haq, BU; et al. (eds.), Proceedings of the Ocean Drilling Program, Scientific Results, College Station, TX (Ocean Drilling Program), 122, 569-585, doi:10.2973/odp.proc.sr.122.155.1992

Palavras-Chave #122-761C; Calcispheres; Coccoliths; d13C carb; d13C skel carb; d18O carb; d18O skel carb; delta 13C, carbonate; delta 13C, skeletal carbonate; delta 18O, carbonate; delta 18O, skeletal carbonate; DRILL; Drilling/drill rig; Inorganic particles; Joides Resolution; Label; Label 2; Leg122; Mass spectrometer Finnigan MAT 251; Ocean Drilling Program; ODP; ODP sample designation; Sample code/label; Sample code/label 2; Smear slide analysis; South Indian Ridge, South Indian Ocean; Thoracosphere
Tipo

Dataset