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Dolomite abundance in the North American rock record
  • Julia Wilcots,
  • Shanan E Peters,
  • Kristin D Bergmann
Julia Wilcots
Princeton University, MIT

Corresponding Author:jwilcots@princeton.edu

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Shanan E Peters
University of Wisconsin-Madison
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Kristin D Bergmann
Massachusetts Institute of Technology
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The mineral dolomite (CaMg(CO3)2) forms in only small quantities in modern oceans, cannot be precipitated abiotically from unmodified seawater in laboratory experiments, yet comprises much of the carbonate rock record. The challenge of explaining the apparent temporal discrepancy in dolomite, the “dolomite problem,” has fascinated carbonate sedimentologists for centuries. Yet, this pursuit has lacked a quantitative tabulation of dolomite in the rock record. Here, we use the North American rock record, as archived in Macrostrat, to assemble a record of dolomite abundance through geologic time. The completeness and age resolution of our dataset allow us to compare dolomite abundance with environmental variables, including stromatolite abundance, evaporite occurrences, sea level, glaciation, and temperature. We use these comparisons to test the assumption that the bulk of the geologic dolomite record was formed via secondary diagenetic processes. We find no monotonic decrease in abundance with age-the expected result if late diagenesis affects the bulk of the record. Dolomite was just as abundant during the first half of the Paleozoic as it was during most of the Neoproterozoic, a challenge to canonical thinking. We show that a number of dolomite precipitation mechanisms known from modern environments and experimentally grown dolomite can explain many of the patterns we observe in the North American dolomite record. Perhaps dolomite is not such a problem after all.