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doi:10.2204/iodp.proc.302.203.2009

Results

On all 1570 samples, peaks for 38 minerals were identified and quantified on XRD traces. The sum of all peak areas was calculated as a “total peak area” (TPA) (Fig. F2). Data are presented in the same manner as in the “Sites M0001–M0004” chapter. Presenting the ratio of a given mineral peak versus TPA also excludes the dilution of the noncrystalline materials, which produces a diffuse bulb in the background of the diffractogram (compare Fig. F4 and Fig. F5). In the Paleogene sequence, particularly in lithologic Units 2 and 3 of the ACEX cores (see the “Sites M0001–M0004” chapter), this is represented by noncrystalline opal-A and partially crystalline opal-CT. The reduction in TPA is here directly related to opal contents up to 60%–70% (Ogawa et al., 2008, submitted). In the Neogene section of the ACEX cores, small amounts of amorphous Fe- and Mn-oxides can be assumed, as outlined by the inorganic geochemistry data (see the“Methods” chapter).

The Expedition 302 scientists (see the “Sites M0001–M0004” chapter) already chose some very indicative intensity peak ratios, such as the ratios of plagioclase and K-feldspar and of kaolinites and chlorites for tracing wet or dry, warm or cold chemical (wet and warm = more kaolinite and less feldspars, less K-feldspar), and strong or weak physical weathering (Griffin et al., 1968; Tucker, 1988). Both ratios have a clear maximum during the warmer phases of the Paleogene sequence (Fig. F2).

Primary or nondiagenetic carbonate minerals (especially calcite) occur predominantly in the upper 200 m of the combined ACEX core sequence and are always a minor component in the Lomonosov Ridge sediment sequence. Nevertheless, in the uppermost 60 m (~4 Ma according to O’Regan et al., 2008b) carbonate minerals continuously increase, with high-frequency changes occurring in the dolomite content (Fig. F6). It is possible that the intensification of the Northern Hemisphere glaciation is reflected by these data. St. John (2008) proposes such intensification based on an increase in ice-rafted debris and coarse fraction content. However, this is only a hypothesis because a full quantification of the mineral content and its integration with grain size, ice-rafted debris, and physical property data is pending (see O’Regan et al., 2008a, for a first glance at such an effort).

This data report can only give a brief insight into the plentifulness of significant changes of the bulk mineral assemblage. Data are stored in the Pangaea WDC Mare Database (doi.pangaea.de/​10.1594/​PANGAEA.705057) in the same manner data were tabulated in the site chapter (Table T42 in the “Sites M0001–M0004” chapter). Normalizing the single peak data to the TPA allows for a good interlaboratory comparability and reliable semiquantification of XRD data as long as the configuration of the instruments is similar (i.e., same radiation, same divergence slits, and similar detector). We will complete full quantification of mineral contents for geochemical and paleoceanographic purposes using the QUAX full-pattern analysis software (cf. Vogt et al., 2002).

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