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- Title
Permian Magnetostratigraphy and End of the Kiaman Reverse Polarity Superchron From the Southeast Karoo Basin, South Africa.
- Authors
De Kock, M. O.; Abubakre, A. O.
- Abstract
Paleomagnetic results for a ∼2,353‐m‐thick magnetostratigraphic section for undeformed middle to late Permian rocks in the southeast of the Karoo Basin of South Africa are reported. Predominantly pseudo‐single‐domain or single‐domain titanomagnetite (with possible minor contributions by pyrrhotite and multi‐domain magnetite) were identified as remanence carriers of a dual polarity magnetization interpreted as the record of the Permian geomagnetic field during the Kiaman Reverse Polarity Superchron and subsequent Illawarra mixed polarity interval. The timing of remanence acquisition is further constrained by the effect of Jurassic‐aged dolerite intrusions, which either partially or wholly overprint the Permian remanence in their immediate vicinity. A paleopole at 62.0°S; 64.3°E and dp/dm = 4.9°/5.8° is calculated from the bedding‐corrected primary remanence (when corrected for inclination shallowing at f = 0.6 the paleopole is located at 53.2°S; 46.9°E and dp/dm = 5.9°/6.3°). This is comparable to other Permian paleopoles from the southwest section of the Karoo Basin. The end of the Kiaman Reverse Polarity Superchron can be correlated between the E‐W extremes of the basin to reveal a diachronous boundary between the Ecca and the Beaufort groups, with diachronicity calibrated to 1.1 million years for the first time. Plain Language Summary: Magnetostratigraphy is here used as a dating tool for calibrating the correlation of middle to late Permian sedimentary rock units. During the Permian, the Kiaman Reverse Polarity Superchron is a prominent ca. 318–265 Ma magnetostratigraphic interval of reverse polarity described from east Australia (among many other locations) and is followed by the Illawarra interval of mixed polarity. The end of the Kiaman Reverse Polarity Superchron is a useful chronostratigraphic marker horizon. We identify the end of the Kiaman Reverse Polarity Superchron within drill core from the southeast Karoo Basin and correlate this to its record within the southwest of that basin at localities that are 900 km apart. Another prominent marker horizon in the Karoo Basin (i.e., the boundary between the Ecca and the Beaufort groups) is characterized by a change in the depositional environment from marine to terrestrial deposition. Although this important lithostratigraphic boundary is known to be diachronous across the Karoo Basin, we here illustrate and calibrate 1.1 million years of time transgression by this boundary in the southern part of the basin. Key Points: The end of the Kiaman Reverse Polarity Superchron is identified in the southeast Karoo Basin allowing regional correlationThe effect of Karoo large igneous province dolerite intrusions is limited, and primary Permian remanence defines magnetostratigraphyThe diachronous boundary between the Ecca and Beaufort groups is calibrated
- Subjects
ILLAWARRA (N.S.W.); SOUTH Africa; PALEOMAGNETISM; DRILL cores; IGNEOUS provinces; CORE drilling; REMANENCE; GEOMAGNETISM
- Publication
Journal of Geophysical Research. Solid Earth, 2022, Vol 127, Issue 6, p1
- ISSN
2169-9313
- Publication type
Article
- DOI
10.1029/2022JB024384