Aragonitic oolite deposits in Danian (lower Palaeocene) carbonate shelves from the Pyrenees, N Spain.

Abstract

Danian shallow-water carbonates from the Pyrenees comprise substantial amounts of oolite, a striking feature given the global paucity of these non-skeletal deposits during the early Paleogene (Sandberg, 1983). The host succession form a wide rimmed shelf, with large coralgal reefs along its seaward margin (Baceta, 1996). Platform growth was punctuated by 3rd to 5th order relative sea level changes that created three depositional sequences and numerous m-scale shelf top parasequences. Oolite occur as multiple sheet-like units at the base of 4th-5th order parasequences, and mostly represent low-relief dunes and bars associated to tidal and wave-induced currents during episodes of marine re-flooding. The ooids show microfabrics and diagenetic features indicative of a dominant primary aragonite mineralogy. This enhanced precipitation of non-skeletal aragonite across the shelf top was coeval to prolific skeletal aragonite production along the reefal margin (i.e. corals, peys- sonnelids and dasyclads). Without discarding an origin due to local conditions, our data support the hypothesis of a distinct Danian aragonite-facilitating seawater stage before the onset of the Aragonite III global phase of the middle-late Cenozoic (Sandberg, 1983; Stanley, 2006).