Recalibration of the geomagnetic polarity timescale

Abstract

The quest for improved time control, to estimate rates of geologic and paleoenvironmental processes, is central to the Earth sciences. Until the middle of this century, geochronology was based solely on macrofossil evolution, providing the largely unmodified definition of geologic stages. In the last few decades, with impetus from the Deep Sea Drilling Project (DSDP) and the Ocean Drilling Program (ODP), microfossil biostratigraphy has become increasingly important. Although new radiometric techniques have resulted in improved absolute age precision, the direct correlation of absolute ages to biozonations (and hence to geologic stage boundaries) remains poor. This is due to the difficulty of finding materials suitable for radiometric dating which can be directly correlated to biozonations. The bridge between biozonations and absolute ages and the interpolation between absolute ages are best accomplished, particularly for Cenozoic and late Mesozoic time, through the geomagnetic polarity timescale (GPTS). The template for Late Jurassic to Quaternary geomagnetic polarity is derived from oceanic magnetic anomalies. As demonstrated by Heirtzler et al. [1968], the GPTS can be constructed using oceanic magnetic anomaly record(s), assuming constant seafloor spreading rate(s), and interpolating between available radiometric ages. In the last quadrennium, there have been outstanding developments in radiometric dating and astrochronology which have greatly improved the absolute age control of the GPTS.