Relative palaeointensity for dating geological sequences
Palaeomagnetic and palaeoenvironmental data from Indonesia and particularly from the Island of Sulawesi are scarce and exact dating has turned out to be a challenge in many archives from this region. Here we outline difficulties in radiocarbon dating of the palaeoenvironmental record from Lake Kalimpaa, Sulawesi, Indonesia. These difficulties demand the integration of additional parameters to obtain a reliable chronology for this record. Thus, we compare the palaeomagnetic secular variation data from this record with the CALS3k.4 spherical harmonic geomagnetic model of the 0–3 ka field (Korte & Constable 2011). The resulting age–depth model for the Lake Kalimpaa sequence provides a profound basis for further multi-proxy investigations on this record. For the first time, high-resolution palaeomagnetic secular variation data continuously spanning the past 1300 years are presented for this region, which complement existing records with lower temporal resolution or records missing the top-most sections.
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Magnetostratigraphy is best known as a technique that employs correlation among different stratigraphic sections using the magnetic directions defining geomagnetic polarity reversals as marker horizons. The ages of the polarity reversals provide common tie points among the sections, allowing accurate time correlation. Recently, studies of magnetic methods and the timing of geological processes have acquired a broader meaning, now referring to many types of magnetic measurements within a stratigraphic sequence. Many of these measurements provide correlation and age control not only for the older and younger boundaries of a polarity interval, but also within intervals. Thus, magnetostratigraphy no longer represents a dating tool based only on geomagnetic polarity reversals, but comprises a set of techniques that includes measurements of geomagnetic field parameters, environmental magnetism, rock-magnetic properties, radiometric dating and astronomically forced palaeoclimatic change recorded in sedimentary rocks, and key corrections to magnetic directions related to geodynamics, palaeocurrents, tectonics and diagenetic processes.