COMPARISON OF THE PETROGRAPHIC CHARACTERISTICS OF NEOGENE AND PLEISTOCENE VOLCANICLASTIC-RICH CARBONATES FROM CURACAO, NETHERLANDS ANTILLES

Mixed petrographic volcaniclastic/carbonate samples were collected from Neogene and Pleistocene outcrops from fore-reef slopes and within erosional inlets (bocas) on Curacao, Netherlands Antilles. Outcrops of the SeroeDomi Formation included conglomerate facies of the Younger Seroe, and Pleistocene outcrops included volcaniclastic deposits associated with Pleistocene reef terraces of the Lower Reef Terrace. The depositional environments of these two outcrops were significantly different: SeroeDomi is interpreted as fore-reef slope/debris flows carrying eroded material from the Curacao Lava Formation, and the Pleistocene terrace outcrops are backreef/lagoonal facies with eroded volcanic clasts from the nearby outcrops of the Curacao Lava Formation. Standard petrographic observations, coupled with cathodoluminescence microscopy and XRD, were conducted. Chemically weathered basalt clasts in the SeroeDomi Formation had a reticulated texture and consisted of limonite and chlorite, while partially weathered basalt clasts contained pyroxenes.The reticulated texture of some of the grains likely represents the simultaneous crystallization of illmanite and olivine, which has been altered to limonite. Basalt clasts in the Pleistocene samples show little to no chemical alteration, consisting of rounded diabase basalt fragments with a similar reticulated texture. Examining the weathering history of the basalt fragments is an important step in understanding its role as a possible Mg-source for dolomitization in the SeroeDomi Formation.