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| Format: | Dataset Open Access |
| Language: | en |
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PANGAEA
1990
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| Online Access: | https://doi.org/10.1594/PANGAEA.755955 |
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| _version_ | 1867170911693570048 |
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| author | Baker, Paul A Malone, Mitchell J Burns, Stephen J Swart, Peter K |
| author_facet | Baker, Paul A Malone, Mitchell J Burns, Stephen J Swart, Peter K |
| collection | Datos científicos de ciencias marinas y ambientales |
| contents | Stable isotopic and minor element compositions were measured on the fine fraction of pelagic carbonate sediments from Ocean Drilling Program Site 709 in the central Indian Ocean. This section ranges in age from 47 Ma to the present. The observed compositional variations are the result of either paleoceanographic changes (past oceanic chemical or temperature variations) or diagenetic changes. The CaCO3 record is little affected by diagenesis. From previous work, carbonate content is known to be determined by the interplay of biological productivity, water column dissolution, and dilution. The carbon isotopic record is generally similar to previously published curves. A good correlation was observed between sea-level high stands and high 13C/12C ratios. This supports Shackleton's hypothesis that as the proportion of organic carbon buried in marine sediments becomes larger, oceanic-dissolved inorganic carbon becomes isotopically heavier. This proportion appears to be higher when sea level is higher and organic carbon is buried in more extensive shallow-shelf sediments. The strontium content and oxygen isotopic composition of carbonate sediments are much more affected by burial diagenesis. Low strontium concentrations are invariably associated with high values of d18O, probably indicating zones of greater carbonate recrystallization. Nevertheless, there is an inverse correlation between strontium concentration and sea level that is thought to be a result of high-strontium aragonitic sedimentation on shallow banks and shelves during high stands. Iron and manganese concentrations and, to a lesser extent, magnesium and strontium concentrations and carbon isotopic ratios are affected by early diagenetic reactions. These reactions are best observed in a slumped interval of sediments that occurs between 13.0 and 17.5 Ma. As a result of microbial reduction of manganese and iron oxides and dissolved sulfate, it is hypothesized that small amounts of mixed-metal carbonate cements are precipitated. These have low carbon isotopic ratios and high concentrations of metals. |
| format | Dataset Open Access |
| id | pangaea_https___doi_org_10_1594_PANGAEA_755955 |
| institution | PANGAEA |
| language | en |
| publishDate | 1990 |
| publisher | PANGAEA |
| record_format | pangaea |
| spellingShingle | Elemental and stable isotopic composition of fine fraction samples of ODP Site 115-709 (Table 1) Baker, Paul A Malone, Mitchell J Burns, Stephen J Swart, Peter K 115-709A; 115-709B; 115-709C; AGE; Atomic absorption spectrometry (AAS), Perkin-Elmer; Calcium carbonate; Calcium carbonate, dry weight; DEPTH, sediment/rock; DRILL; Drilling/drill rig; DSDP/ODP/IODP sample designation; Event label; Iron; Joides Resolution; Leg115; Magnesium; Manganese; Mass; Mass spectrometer Finnigan MAT 251; Ocean Drilling Program; ODP; Sample code/label; South Indian Ridge, South Indian Ocean; Strontium; Weighed (scale); δ13C, carbonate; δ18O, carbonate Stable isotopic and minor element compositions were measured on the fine fraction of pelagic carbonate sediments from Ocean Drilling Program Site 709 in the central Indian Ocean. This section ranges in age from 47 Ma to the present. The observed compositional variations are the result of either paleoceanographic changes (past oceanic chemical or temperature variations) or diagenetic changes. The CaCO3 record is little affected by diagenesis. From previous work, carbonate content is known to be determined by the interplay of biological productivity, water column dissolution, and dilution. The carbon isotopic record is generally similar to previously published curves. A good correlation was observed between sea-level high stands and high 13C/12C ratios. This supports Shackleton's hypothesis that as the proportion of organic carbon buried in marine sediments becomes larger, oceanic-dissolved inorganic carbon becomes isotopically heavier. This proportion appears to be higher when sea level is higher and organic carbon is buried in more extensive shallow-shelf sediments. The strontium content and oxygen isotopic composition of carbonate sediments are much more affected by burial diagenesis. Low strontium concentrations are invariably associated with high values of d18O, probably indicating zones of greater carbonate recrystallization. Nevertheless, there is an inverse correlation between strontium concentration and sea level that is thought to be a result of high-strontium aragonitic sedimentation on shallow banks and shelves during high stands. Iron and manganese concentrations and, to a lesser extent, magnesium and strontium concentrations and carbon isotopic ratios are affected by early diagenetic reactions. These reactions are best observed in a slumped interval of sediments that occurs between 13.0 and 17.5 Ma. As a result of microbial reduction of manganese and iron oxides and dissolved sulfate, it is hypothesized that small amounts of mixed-metal carbonate cements are precipitated. These have low carbon isotopic ratios and high concentrations of metals. |
| title | Elemental and stable isotopic composition of fine fraction samples of ODP Site 115-709 (Table 1) |
| topic | 115-709A; 115-709B; 115-709C; AGE; Atomic absorption spectrometry (AAS), Perkin-Elmer; Calcium carbonate; Calcium carbonate, dry weight; DEPTH, sediment/rock; DRILL; Drilling/drill rig; DSDP/ODP/IODP sample designation; Event label; Iron; Joides Resolution; Leg115; Magnesium; Manganese; Mass; Mass spectrometer Finnigan MAT 251; Ocean Drilling Program; ODP; Sample code/label; South Indian Ridge, South Indian Ocean; Strontium; Weighed (scale); δ13C, carbonate; δ18O, carbonate |
| url | https://doi.org/10.1594/PANGAEA.755955 |