Dolomite pipes in the Crato Formation fossil lagerstätte (Lower Cretaceous, Aptian), of northeastern Brazil

Abstract

Pipe-like structures filled with massive and brecciated Fe-rich dolomites occur within a 5–6 m sequence of otherwise horizontal, millimetre-laminated limestones of the Nova Olinda Member of the Crato Formation (Aptian, Lower Cretaceous) of north east Brazil. The pipe-fills predate compaction, contain hydro-brecciated host strata, developed penecontemporaneously with a carbonate laminite, and may represent methane seeps. Such seeps may have developed above buried topographic highs as fluids emanating from deeper strata migrated along buried discontinuities such as the basement/Cretaceous unconformity and buried faults in the basement.