IRD abundance (in weight percent) and MAR are presented in the "Appendix", and Figure F2. IRD abundance is cyclic throughout, with small peaks alternating with periods of low or no IRD. IRD abundance fluctuates within a range of 0-2.0 wt%, except within three intervals: two peaks between 195.7 and 204.3 mbsf, 128.8 mbsf, and 60.7-62.2 mbsf (Fig. F2A). These peaks range from 2.5 to 3.7 wt% IRD, and the first and third intervals coincide with 20- to 50-cm-thick diamicton beds. These diamicton beds show characteristics attributed to deposition from ice rafting that include gradational contacts, weak stratification, and random pebble orientation (Cowan et al., 1997). The MAR profile has an appearance similar to the IRD abundance with three unusually large peaks (three to five times the size of the other peaks) at ~2.8 (Fig. F2B, interval a), 1.9 (Fig. F2B, interval b) and 0.88 Ma (Fig. F2B, interval c). Between these large peaks, there are many smaller frequency cycles produced by peaks in MAR that alternate with low or no IRD. One prolonged period of low MAR occurs from 2.12 to 1.98 Ma. Many cycles have a sawtooth pattern that increases gradually upsection to the peak MAR then abruptly decreases to zero. An example of one such prominent cycle occurs from 0.65 to 0.55 Ma. Visually, the IRD MAR record at Site 1101 is divided into three intervals of ~1-Ma duration (Fig. F2B). In intervals a-b and b-c (Fig. F2B), the general trend is for the magnitude of the highest MAR peaks within a cycle to decrease through the interval then abruptly increase at the prominent peak. In the upper interval (above c) (Fig. F2B) this MAR trend is reversed, with the peaks gradually increasing until an abrupt decrease at 0.1 Ma. The frequency of peaks in the upper interval is also greater than in a-b and b-c (Fig. F2B).
Within the interval from 95 to 38 mbsf (Sections 178-1101A-11H-7 to 6H-1), sediments were categorized by lithofacies using core descriptions and X-radiographs (Fig. F3). This interval, from 1.37 to 0.54 Ma, was chosen for detailed study because it contains the Jaramillo Subchron and the Brunhes/Matuyama boundary. It has well-defined alternations between foraminifer-bearing homogeneous mud representative of interglacials and terrigenous laminated or homogeneous mud without foraminifers deposited during glacial periods (Barker, Camerlenghi, Acton, et al., 1999). The contrast in magnetic susceptibility (MS) between the carbonate-bearing interglacials and the low-carbonate terrigenous glacial intervals has produced a well-defined cyclicity throughout (Fig. F3). Most sections were X-rayed, and this allowed for further characterization of sedimentary structures and a count of IRD >2 mm in 1-cm increments (Fig. F3). The prominent peak c (Fig. F2B) occurs at 0.88 Ma (62.2-60.7 mbsf), and therefore, the timing of this and other peaks in IRD with regard to glacial-interglacial cyclicity can be investigated.