Extending the paleogeographic range and our understanding of the Neoarchean Monteville impact spherule layer (Transvaal Supergroup, South Africa)

Bruce M. Simonson, Nicolas J. Beukes, Sandra Biller

Research output: Contribution to journalArticlepeer-review

3 Citations (Scopus)

Abstract

The Monteville spherule layer (MSL) was deposited in the Griqualand West Basin (GWB) on the Kaapvaal Craton approximately 2.63 Ga. The spherules were generated by a large impact and reworked by impact-generated waves and/or currents. The MSL has been intersected in three previously undescribed cores. Two of the cores, GKF-1 and GKP-1, were drilled ~30 km west of the southernmost outcrop of the MSL. The third core, BH-47, was drilled ~250 km south and east of the GWB. The MSL contains medium to coarse sand-size spherules like those described previously in all three cores but each one was emplaced in a different way. In GKF-1, the MSL is 90 cm thick and contains large rip-up clasts of basinal carbonate and early diagenetic pyrite. In GKP-1, the MSL is only 1.5 cm thick and consists largely of fine carbonate sand, yet it contains pyrite intraclasts up to ~1 cm long. In BH-47, the MSL consists of a lower coarse sandy zone ~37 cm thick rich in spherules, carbonate peloids/ooids, pyrite intraclasts, and quartzose sand and an upper, finer sandy zone ~46 cm thick; neither zone contains any large intraclasts. The new occurrences triple the known extent of the MSL from ~15,000 to ~46,000 km2, support the oceanic impact model for the formation of the MSL, demonstrate that it is a persistent regional time-stratigraphic marker, place new constraints on the Kaapvaal paleoshoreline at the time of impact, and support the existence of Vaalbara.

Original languageEnglish
Pages (from-to)2217-2240
Number of pages24
JournalMeteoritics and Planetary Science
Volume54
Issue number10
DOIs
Publication statusPublished - 1 Oct 2019

ASJC Scopus subject areas

  • Geophysics
  • Space and Planetary Science

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