Chemistry of biogenic sediments from the equatorial Pacific

• Main Authors: Kryc, Kelly A, Murray, Richard W, Murray, David W
• Format: Other/Unknown Material
• Language: English
• Published: PANGAEA 2003
• Subjects: 11031300 Multicorer1; 11080952 Multicorer4; 11091335 Multicorer5; 11101338 Pistoncore5; 11120107 Multicorer8; 11161400 Multicorer11; 11172115 Multicorer12; 11181007 Multicorer13; 11191756 Piston core 8; TT013-PC72; 11230530 Multicorer18; 11240508 Multicorer19; 11270742 Multicorer22; 11290827 Multicorer25; 11291231 Pistoncore13; 12062238 Multicorer37; 178-1098B; Drake Passage; DRILL; Drilling/drill rig; Equatorial Pacific; GC; Gravity corer; JGOFS; Joides Resolution; Joint Global Ocean Flux Study; Leg178; MUC; MultiCorer; Ocean Drilling Program; ODP; PC; Piston corer; Thomas G. Thompson; TT013; TT013_104; TT013_113; TT013_114; TT013_148; TT013_23; TT013_27; TT013_32; TT013_4; TT013_41; TT013_58; TT013_63; TT013_66; TT013_72; TT013_88; TT013_93; Antarc*; Antarctic; Antarctic Peninsula
• Online Access: https://doi.pangaea.de/10.1594/PANGAEA.725451; https://doi.org/10.1594/PANGAEA.725451

To increase our understanding of the mechanisms that control the distribution of Al and Ti within marine sediment, we performed sequential extractions targeting the chemical signatures of the loosely bound, exchangeable, carbonate, oxide, organic, opal, and residual fraction of sediment from a carbonate-dominated regime (equatorial Pacific) and from a mixed opal-terrigenous regime (West Antarctic Peninsula). We observe a systematic partitioning of Al and Ti between sediment phases that is related to bulk Al/Ti. We show that, where we can quantify an Al(excess) component, the dissolved Al is preferentially affiliated with the oxide fraction, resulting in Al/Ti molar ratios of 500-3000. This is interpreted as the result of surface complexation in the water column of dissolved Al onto oxyhydroxides. We also observe a previously undetected Ti(excess) with as much as 80% of the total Ti in the organic fraction, which is most likely a function of metal-organic colloidal removal from the water column. In samples where the excess metals are obscured by the detrital load, the Al and Ti are almost exclusively found in the residual phase. This argues for the paired removal of Al (preferentially by the oxide component) and Ti (preferentially by the organic component) from the water column by settling particulate matter. This research builds upon earlier work that shows changes in the bulk ratio of Al to Ti in carbonate sediment from the central-equatorial Pacific that coincide with changes in the sedimentary bulk accumulation rate (BAR). The ratios that are observed are as much as three times higher than typical shale values, and were interpreted as the result of scavenging of dissolved Al onto particles settling in the water column. Because this non-terrigenous Al(excess) accounts for up to 50% of the total sedimentary Al inventory and correlates best with BAR, the bulk Al/Ti may be a sensitive tracer of particle flux and, therefore, export production. Because we show that the excess metals are the result of scavenging ...