Architecture of the volcanic layer from the Costa Rica Rift, constraints from core-log integration

[1] An understanding of the architecture of the ocean crust's volcanic layer is critical since this records the variations in volcanic activity during formation and subsequently controls the movement of hydrothermal fluids through this layer. Unfortunately, core recovery in the majority of Ocean Drilling Program (ODP)/Deep Sea Drilling Program basement holes is generally low and biased toward more massive lithologies. Consequently, the identification and estimation of lithological diversity within the volcanic layer is only possible through the integration of core and wire line logging results. Wire line logging provides nearly continuous records of both physical and chemical properties of the borehole wall, which can be used to identify the various volcanic/sedimentary lithologies, which then can be calibrated in regions of enhanced core recovery. Using this approach, the architecture of the volcanics from ODP Hole 896A has been reconstructed. This new model illustrates a hiatus in volcanism marked by a thick breccia horizon, which probably marks the transition from axis to off-axis volcanism.