Magnetic Reversals: Their Application to Stratigraphic Problems

Abstract

Abstract Paleomagnetic results from Europe and North America show that the Lower Triassic is characterized by mixed polarity (“Buntsandstein-Chugwater mixed polarity zone”), in contrast to the long-lasting predominantly reversed polarity of the “Kiaman interval” of the Permian. These pronounced differences emphasize the possibilities of applying paleomagnetism to stratigraphic boundary problems, in this case the definition of the Paleozoic-Mesozoic boundary. Furthermore, a paleomagnetic study of the uppermost part of the middle and upper Buntsandstein (Scythian) has shown that several magnetic reversals provide the same correlation as do fossil soils across a distance of more than 200 km. This example is used to demonstrate the importance of magnetic reversals as an auxiliary stratigraphic tool for regional problems. A preliminary Permo-Tricssic reversal time scale was assembled, which indicates evidence for a long-lasting (dominantly normal) “Newark normal interval” of Late Triassic to Early Jurassic age. This interval probably is reflected in the quiet zones of oceanic magnetic anomaly (sea-floor spreading) pattern odiacent to the continental slopes on both sides of the North Atlantic.