Abstract
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.