87Sr/86Sr Chronostratigraphy and dolomitization history of the Seroe Domi Formation, Curaçao (Netherlands Antilles)

The Seroe Domi Formation is a 350 m-thick sequence of Neogene marine limestones and silicilastic sandstones cropping out on the leeward coast of Curaçao, Netherlands Antilles. Integrated analyses of lithofacies, biostratigraphy, geochemistry and Sr isotope model age analyses indicate that Seroe Domi Formation has experienced three major episodes of limestone diagenesis and dolomitization (Dolomites I, I′, and II) that have taken place after successive Mio-Plio-Pleistocene depositional and subaerial exposure events (Subunits 1, 2, and 3). Subunit 1, the lowermost 30 to 100 m of the Seroe Domi Formation, is composed of interbedded coralgal grainstone gravity flows, pelagic wackestones, and allochthonous blocks deposited in Middle Miocene deep-water (>500 m) fore-reef and carbonate slope environments. Subunit 2, the uppermost 250 m of the Seroe Domi Formation, consists of coralgal packstones with basement-derived siliciclastic sands that were deposted in shallowing fore-reef to reef-front environments during the Late Miocene to Pliocene. Subunit 3 siliciclastic sandstones were deposited during the Early Pleistocene within erosional cavities in the Subunit 2 limestones, and are overlain by Late Pleistocene Quaternary Limestone Terraces. The petrography, distribution and geochemistry of Dolomites I, I′ and II indicate that they were precipitated from seawater-freshwater mixing zone fluid environments. Dolomite rhombs and meteoric calcite cements within biomolds illustrate that the host Seroe Domi Formation limestones were subaerially exposed prior to each dolomitization event. Dolomite I (δ18O = +1.04 to +2.46% PDB; δ13C = −2.55 to −6.79 PDB;87Sr/86Sr=0.708866 to 0.708915; Zn=0 ppm; Cu=0 ppm) was precipitated from mixtures of seawater with isotopically-depleted freshwater during the late Middle Miocene. Dolomite I′ (δ18O = +2.08 to +3.55 PDB, δ13C = −1.53 to 1.69 PDB,87Sr/86Sr=0.708981−0.709030; Zn=0 ppm; Cu=0 ppm) was also precipitated from mixtures of seawater with isotopically-depleted freshwater, but during late Late Miocene. In contrast, Dolomite II (δ18O = +2.69 to +3.51 PDB; δ13C = −0.34 to +1.53 PDB;87Sr/86Sr=0.708954 to 0.709088; Zn=20 ppm; Cu=20 ppm) precipitated from late Early Pliocene mixtures of seawater with isotopically-depleted freshwater that had derived Zn, Cu, and less-radiogenic Sr from basalts comprising the Curaçao basement.