Kolosjoki Sedimentary Formation: A Record In The Aftermath Of The Paleoproterozoic Global Positive Delta C-13 Excursion In Sedimentary Carbonates

The Kolosjoki Sedimentary Formation of the Pechenga Greenstone Belt, north eastern Fennoscandia, records the aftermath of the Paleoproterozoic global positive delta C-13 excursion in sedimentary carbonates (the Lomagundi-Jatuli isotope excursion). The goals of this research were to provide detailed new data on the delta C-13 trend in the Kolosjoki Sedimentary Formation and generate a secular delta C-13 curve for the time period immediately succeeding the Lomagundi-Jatuli isotope excursion. For these purposes, sedimentary carbonate samples from two new drillcores representing the Kolosjoki Sedimentary Formation were collected. In total 88 whole-rock samples and 67 micro-drilled subsamples (ca. 1-3 mg) were analyzed for the isotope composition of C and O, the whole-rock elemental abundances, and for the composition of the acid-soluble fraction. The Kolosjoki carbonate rocks are dolostone or calcitic dolostone (Mg/Ca=0.50-0.67) with minor limestone (Mg/Ca=0.04-0.06). Only weak correlation was observed between the Mn/Sr ratios and the delta C-13 and delta O-18 values, and the carbonate samples have likely retained their near-primary delta C-13 values. The sedimentary carbonate rocks show first low delta C-13 values at -2 to -1 parts per thousand and then a subtle, upward increasing delta C-13 trend fromca. 1 to 3 parts per thousand. The increasing delta C-13 trend is interpreted to record a recovery from a delta C-13 minimum following the Lomagundi-Jatuli isotope excursion. (C) 2013 Elsevier B. V. All rights reserved.