(Appendix) Characteristic directions at DSDP Hole 76-534A

Kimmeridgian-Tithonian red marly limestones and Berriasian white limestones were recovered at Site 534 of DSDP Leg 76 in the western North Atlantic. These yielded a well-defined magnetostratigraphy with the characteristic magnetization carried by hematite in red sediments and magnetite in white sediments. The polarity sequence is correlated to the magnetostratigraphy of Kimmeridgian-Tithonian-Berriasian pelagic carbonates of northern Italy and southern Spain, allowing precise biostratigraphic age correlations. The Berriasian/Tithonian boundary occurs within the upper half of Core 90, the late Tithonian/early Tithonian boundary at the base of Core 96, and the Tithonian/Kimmeridgian boundary at the top of Core 102. Correlations are also made to M-16 through M-22 of the marine magnetic anomaly M-sequence. Poor recovery and irregular magnetic properties of the underlying Kimmeridgian-Oxfordian-Callovian marls and claystones prevented determination of a polarity sequence, but the entire interval has mixed polarity. Valanginian gray marly limestones have very weak magnetizations, and preliminary results are inadequate to determine the polarity pattern.

Natural oxides, elements and remanent magnetization intensities and directions at DSDP Hole 93-603B

Dark green spherules occur in the lower part of a turbidite in Section 603B-22-3, at the 70 cm level. In all probability these spherules originally consisted of massive glass, but now appear to have become completely altered into smectite. The presence of numerous microscopic fissures in the spherules probably mediated in the alteration process. Judging by the presence of similar spherules at the Cretaceous/Tertiary (K/T) boundary in DSDP Hole 390B, the green spherules are thought to represent diagenetically altered impact ejecta from one large or several smaller extraterrestrial objects at the end of the Cretaceous. The presence of anomalously high concentrations of Ni, Co, and As higher up in the turbidite are in agreement with an expected enrichment of these elements in the K/T boundary clay. However, precise Ir analyses are necessary in order to confirm this.

Component NRM Directions for two sediment cores from the Arctic Ocean

Inclination patterns of natural remanent magnetization (NRM) in Quaternary sediment cores from the Arctic Ocean have been widely used for stratigraphic correlation and the construction of age models, however, shallow and negative NRM inclinations in sediments deposited during the Brunhes Chron in the Arctic Ocean appear to have a partly diagenetic origin. Rock magnetic and mineralogical studies demonstrate the presence of titanomagnetite and titanomaghemite. Thermal demagnetization of the NRM indicates that shallow and negative inclination components are largely "unblocked" below ~300 °C, consistent with a titanomaghemite remanence carrier. Following earlier studies on the Mendeleev-Alpha Ridge, shallow and negative NRM inclination intervals in cores from the Lomonosov Ridge and Yermak Plateau are attributed to partial self-reversed chemical remanent magnetization (CRM) carried by titanomaghemite formed during seafloor oxidation of host (detrital) titanomagnetite grains. Distortion of paleomagnetic records due to seafloor maghemitization appears to be especially important in the perennially ice covered western (Mendeleev-Alpha Ridge) and central Arctic Ocean (Lomonosov Ridge) and, to a lesser extent, near the ice edge (Yermak Plateau). On the Yermak Plateau, magnetic grain size parameters mimic the global benthic oxygen isotope record back to at least marine isotope stage 6, implying that magnetic grain size is sensitive to glacial-interglacial changes in bottom-current velocity and/or detrital provenance.