Mg/Ca and Sr/Ca in calcites and estimated distribution coefficients in marine sediments (Table 2)

• Main Author: Delaney, Margaret Lois
• Format: Dataset
• Language: English
• Published: PANGAEA 1989
• Subjects: 30-288_Site; 30-289; 41-366_Site; 41-369_Site; 74-526_Site; Calculated; COMPCORE; Composite Core; Deep Sea Drilling Project; DEPTH; sediment/rock; DRILL; Drilling/drill rig; DSDP; Event label; Glomar Challenger; Leg30; Leg41; Leg74; Magnesium/Calcium ratio; Magnesium distribution coefficient; North Atlantic/CONT RISE; North Atlantic/CONT SLOPE; Sample comment; South Atlantic/CREST; South Pacific; South Pacific/PLATEAU; Strontium/Calcium ratio; Strontium distribution coefficient; Temperature; Pacific; North Atlantic
• Online Access: https://doi.pangaea.de/10.1594/PANGAEA.723370; https://doi.org/10.1594/PANGAEA.723370

Recrystallization processes in marine sediments can alter the extent to which biogenic calcite composition serves as a proxy of oceanic chemical and isotopic history. Models of calcite recrystallization developed to date have resulted in significant insights into these processes, but are not completely adequate to describe the conditions of recrystallization. Marine sediments frequently have concentration gradients in interstitial dissolved calcium, magnesium, and strontium which have probably evolved during sediment accumulation. Realistic, albeit simplified, models of the temporal evolution of interstitial water profiles of Ca, Mg, and Sr were used with several patterns of recrystallization rate variation to predict the composition of recrystallized inorganic calcite. Comparison of predictions with measured Mg/Ca and Sr/Ca ratios in severely altered calcite samples from several Deep Sea Drilling Project sites demonstrates that models incorporating temporal variation in interstitial water composition more successfully predict observed calcite compositions than do models which rely solely on present-day interstitial water chemistry. Temporal changes in interstitial composition are particularly important in interpreting Mg/Ca ratios in conjunction with Sr/Ca ratios. Estimates of Mg distribution coefficients from previous observations in marine sediments, much lower than those in laboratory studies of inorganic calcite, are confirmed by these results. Evaluation of the effects of diagenetic alteration of biogenic calcium carbonate sediment must be a site-specific process, taking into account accumulation history, present interstitial chemistry and its variation in the past, and sample depths and ages.