hide
Free keywords:
-
Abstract:
The Cambrian Pedroche Formation comprises a mixed siliciclastic–carbonate succession recording subtidal
deposition on a marine platform. Carbonate carbon isotope chemostratigraphy confirms previous biostratigraphic
assignment of the Pedroche Formation to the Atdabanian regional stage of Siberia, correlative to Cambrian Series
2. At the outcrop scale, thrombolitic facies comprise ~60% of carbonate-normalized stratigraphy and coated-grains
another ~10%. Petrographic point counts reveal that skeletons contribute at most 20% to thrombolitic inter-reef
and reef-flank lithologies; on average, archaeocyath clasts make up 68% of skeletal materials. In contrast,
petrographic point counts show that skeletons comprise a negligible volume of biohermal and biostromal
thrombolite, associated nodular carbonate facies, and ooid, oncoid and peloid grainstone facies. As such,
archaeocyathan reefal bioconstructions represent a specific and limited locus of skeletal carbonate production and
deposition. Consistent with data from coeval, globally dispersed lower Cambrian successions, our analysis of the
Pedroche Formation supports the view that lower Cambrian carbonates have more in common with earlier,
Neoproterozoic deposits than with younger carbonates dominated by skeletal production and accumulation
