(Table 2) Calcium carbonate content in deep-sea surface sediments, supplement to: Broecker, Wallace S; Clark, Elizabeth (2009): Ratio of coccolith CaCO3 to foraminifera CaCO3 in late Holocene deep sea sediments. Paleoceanography, 24(3), PA3205


The reconstruction of paleocarbonate ion concentrations provides an important constraint on the contribution of the CaCO3 cycle to the decrease in atmospheric CO2 content during glacial time. Such reconstructions have been challenging because each of the existing paleo-[CO3]2- indices has serious limitations. In this study, we reexamine the Broecker-Clark CaCO3 size index by analyzing the <20 µm, 20 to 38 µm, and 38 to 63 µm fractions in sediments from the Ontong-Java Plateau and the Ceara Rise. Scanning electron microscope analyses demonstrate that the less than 20 µm CaCO3 is dominated by coccoliths and the greater than 20 µm CaCO3 is dominated by foraminifera. Our results clearly indicate that the coccoliths are far more resistant to dissolution than the foraminifera. Referenced to a core top sample from 2.31 km depth in a core top sample from 4.04 km depth on the Ontong-Java Plateau, ~70% of the foraminifera CaCO3 was dissolved as opposed to only ~7% of the coccolith CaCO3. We found that the dissolution of foraminifera shells did not produce a significant amount of fragments smaller than 63 µm in size, and thus the Broecker-Clark size index is not a measure of the extent of fragmentation. Rather, it is a measure of the extent of differential dissolution of foraminifera relative to coccoliths. On the basis of these results, we propose a new dissolution index which involves the ratio of dissolution-susceptible foraminifera CaCO3 to total CaCO3.

MW9109-15GGC by WHOI's Dan McCorkle and published previously by Chiu and Broecker (2008).

DOI https://doi.org/10.1594/PANGAEA.831705
Related Identifier https://doi.org/10.1029/2009PA001731
Related Identifier https://doi.org/10.1029/2008PA001599
Metadata Access https://ws.pangaea.de/oai/provider?verb=GetRecord&metadataPrefix=datacite4&identifier=oai:pangaea.de:doi:10.1594/PANGAEA.831705
Creator Broecker, Wallace S; Clark, Elizabeth
Publisher PANGAEA - Data Publisher for Earth & Environmental Science
Publication Year 2009
Rights Creative Commons Attribution 3.0 Unported
OpenAccess true
Language English
Resource Type Supplementary Dataset
Format text/tab-separated-values
Size 578 data points
Discipline Earth System Research
Spatial Coverage (-10.610W, -38.270S, 1.967E, 39.950N); Central Pacific
Temporal Coverage Begin 1954-03-07T00:00:00Z
Temporal Coverage End 1984-12-20T00:00:00Z