The paleomagnetic data presented in this paper are of two different types: those obtained using the shipboard pass-through magnetometer and those derived from a conventional analysis of discrete sediment samples. Shipboard measurements were routinely taken on archive-core sections before and after stepwise alternating-field (AF) demagnetization up to at least 20 mT.
To avoid edge effects, measurements within 5 cm from the edges were removed from the data.
Discrete samples from soft material were taken by pressing 6-cm3 plastic sample boxes into the working half of the cores. The harder sediments were precut with a sharp stainless steel spatula before they were sampled with a plastic cube. Typically, we obtained two samples per 1.5-m core section when the sediment was not disturbed. Scribe marks on the cubes were oriented parallel to the vertical axis of the core. Discrete samples were subjected to progressive AF demagnetization upon return to Munich. Paleomagnetic measurements were carried out in the Paleomagnetism Laboratory of the Universität München with a cryogenic magnetometer. All samples were stepwise AF demagnetized in three directions. Approximately 600 samples from Holes 1138A and 1140A were AF demagnetized in at least five steps up to at least 60 mT to isolate their characteristic remanence components.
A total of 21 sediment samples were selected from different lithotypes from Sites 1138 and 1140 for rock magnetic studies. Isothermal remanent magnetization (IRM), backfield, hysteresis curves, and thermomagnetic curves were measured in air using a variable frequency translation balance in the Paleomagnetism Laboratory of the Universität München.