The carbonate contents at Site 982 vary strongly between 15 and 95 wt% (Fig. 3). The deepest section studied is characterized by continuously high contents of carbonate with maximum values exceeding 90 wt%; only three minor excursions to lower values <55 wt% appear at 52.3, 59.5, and 62.9 mcd. Relatively high numbers of coccoliths display the general trend of the carbonate contents. In contrast to these high carbonate concentrations, rather low numbers of planktonic foraminifers, which are dominated by subpolar species, are observed in the depth interval of >60-52.3 mcd (Fig. 3). The first input of IRD appears at ~59.5 mcd, as also indicated by a first noticeable peak of the >500-µm fraction (Fig. 4), which consists exclusively of large rock fragments. Maxima with relatively high amounts of IRD are present until 38.6 mcd.
A significant change appears at ~55.0 mcd. Relatively high-amplitude and high-frequency fluctuations of the carbonate record are observed. The carbonate contents range from 15 to 90 wt% accompanied by varying numbers of planktonic foraminifers. A general trend to higher numbers of planktonic foraminifers is observed from 55 to 42 mcd. This tendency is also reflected by increasing percentages of the 125- to 500-µm fraction (Fig. 4). The total number of coccoliths is relatively low but is dominated by high percentages of the cold water-adapted species Coccolithus pelagicus in the depth interval 52.8-39.3 mcd. A short interval with intensified frequencies and amplitudes of carbonate contents varying between 15 and 90 wt% at 40.5 to 38.5 mcd marks the next sedimentary transition. This interval is accompanied by high amounts of IRD and an abrupt change in planktonic foraminifer composition. Strongly decreasing percentages of subpolar planktonic foraminifers indicate the appearance of the polar species Neogloboquadrina pachyderma sin. (Fig. 3). This obvious change persists in the following 8 mcd.
Carbonate contents fluctuate strongly from 38.5 to 16 mcd. The two-step decrease of minimum carbonate contents at ~24 mcd is remarkable. In addition, in the section from 40.5 to 32 mcd, the total numbers of coccoliths reach values of up to 40,000 × 106 per gram of sediment with low but significant percentages of C. pelagicus. At 32 mcd, a short peak of again-high percentages of subpolar planktonic foraminifer species leads to a short phase in which subpolar species again dominate the assemblage at >90%. On the other hand, the total number of planktonic foraminifers and also coccoliths decreases (Fig. 3). This phase ends abruptly at 29 mcd, where high percentages of polar planktonic foraminifers reappear and the total number of planktonic foraminifers increases to maximum values of more than 60,000 individuals per gram (ind/gram). At 26 mcd, the amount of benthic foraminifers decreases suddenly. The subpolar planktonic foraminifer percentage curve generally follows the pattern of the strongly fluctuating carbonate record. The total number of coccoliths increases significantly at 29 mcd.
A remarkable change in the structure of the carbonate record is obvious at the last 16 mcd of the record (Fig. 3). Depressed frequency and increased amplitude are characteristic for the carbonate record and also for the record of the subpolar planktonic foraminifer percentage. The curve of the total number of planktonic foraminifers does not seem to follow a regular pattern. There is apparently no correlation between the total number of foraminifers and the carbonate record. This effect is not present for the total abundance of coccoliths. Coccolith peaks match the major carbonate peaks. The highest total numbers of coccoliths can be observed at 2.5 mcd with more than 90,000 × 106 coccoliths per gram of sediment. The highest amounts of IRD, with as much as 18,000 grains/gram, were also counted in this last section.
From high carbonate contents ranging from 10 to 50 wt% and correspondingly high contents of coccoliths from 90 to 85 mcd, the total carbonate sedimentation decreases sharply to almost zero. Little to no carbonate was deposited in the interval from 85 to 65 mcd (Fig. 5). Carbonate contents vary between 0 and 2.6 wt%, and only one isolated peak at 70.5 mcd reaches 23.6 wt%. Long carbonate-barren sections are predominant, with sporadic low values of total planktonic foraminifers below five individuals per gram observed. The first input of IRD occurs in this section at 83.5 mcd. Following the high percentages of the 63- to 125- and the 125- to 500-µm fractions at 83-81 mcd, the grain-size distribution is characterized by high percentages of the <63-µm fraction until 49 mcd (Fig. 6).
Carbonate contents increase slightly in the section from 65 to 31 mcd (Fig. 5). Two maxima at 54.5 and 41 mcd reach 14 and 18 wt%, respectively. Except for these maxima, carbonate values never exceed 5 wt%. Correspondingly, two small peaks in the total amount of coccoliths are obvious. Coccolith assemblages are dominated by Coccolithus pelagicus. The numbers of total planktonic foraminifers do not exceed 26 individuals per gram. IRD input generally increases in this section. Maximum values at 35 mcd reach 16,000 grains/gram. Despite the low numbers of planktonic foraminifers, dominant percentages of subpolar planktonic foraminifers are present from 66 to 64 mcd and from 56 to 53.5 mcd. High percentages also occur from 39 to 34 mcd.
The first significant amount of planktonic foraminifers is from 31 to 24 mcd, fluctuating between zero and maximum numbers of more than 29,000 ind/gram (Fig. 5). The assemblage is clearly dominated by polar species. Analogously, carbonate values increase to generally higher values, varying between 0 and 22 wt%. An almost carbonate-barren interval from 22 to 17 mcd was identified as highly disturbed or slumping in the core descriptions (Jansen, Raymo, Blum, et al., 1996), so we regard this interval as extremely extended.
The last section is characterized by strongly fluctuating carbonate contents as well as greatly varying amounts of planktonic foraminifers and coccoliths. Highest values of carbonate occur to >60 wt%. The highest numbers of planktonic foraminifers range to 50,000 ind/gram; those of coccoliths, as much as 13,000 × 106/g of sediment. Benthic foraminifers also reach higher numbers, with more than 1000 ind/gram. Percentages of subpolar species coincide with the varying carbonate and total planktonic foraminifer records, whereas the generally high IRD input fluctuates anticyclically with the carbonate measurements.