Paleomagnetic study of the Albian Contessa section (Umbria, Italy) has defined several intervals of reversed characteristic remanent magnetizations (ChRM) carried by high unblocking- temperature hematite within the Cretaceous Normal Polarity Superchron. The reversed intervals correspond with 2 reddish zones (pigmentary hematite) found throughout Umbria which may reflect the oxidation state of the seafloor during deposition. The reversed ChRM may represent a remagnetization acquired 18 m.y. after deposition in reversed polarity chron 33R (or later). If a remagnetization, the process is of great interest since it can produce remagnetization patterns which resemble polarity intervals. Alternatively, the reversed ChRM may record intervals of reversed geomagnetic field polarity acquired during intense seafloor oxidation episodes during the mid-Albian (107-104 Ma). If correct, several of the intervals are of sufficient duration (>100 kyr) to be of use in magnetostratigraphic studies and might provide markers on oceanic crust of the Cretaceous Quiet Zone. If primary, the intervals also suggest a modification of models of geomagnetic reversal frequency. Recently, 2 zones of reddish, hematite-bearing sediments were also identified in the Albian Breggia section (Switzerland). The reddish zones may have more than a regional significance; they may mark rapid changes in paleoceanographic conditions analogous to (but opposite in oxidation) to the Cretaceous global anoxic events. Paleomagnetic data suggest the presence of reversed ChRMs from the Breggia sediments from which we can exclude a remagnetization scenario calling upon circulating fluids affecting only a portion of the measured sections. Reactivation of a preexisting mineral phase, however, is another remagnetization mechanism which is presently being considered. Nevertheless, the funding of reversed ChRMs in a stratigraphically narrow interval at well-separated sites gives further support to a primary magnetization model. We propose an extension of our studies to a reference section in Italy and the deep sea (ODP) aimed at characterizing the paleoclimate signature of the mid-Albian sediments through rock- magnetic and cyclostratigraphic (bedding and geochemical) measurements. First, we hope to determine the nature, duration and extent of the oxidized intervals. Second, we hope to use these data as a means to examine critically the lock-in mechanism of the remanent components of magnetization observed in the Albian (and other) pelagic sediments.
