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The study of fossil seep carbonate precipitates exposed in coastal outcrops north of Santa Cruz (California) is producing unprecedented insights on the relationships between tectonics and flow of fluids and gases in organic-rich hemipelagic Neogene sediments. Most of the fieldwork performed during the last year of the project was focused on reconstructing the morphology and geometry/distribution of the seep precipitates in relation to stratigraphic and structural features present in the host formations to investigate potential relationships/controls between lithology, geological structures such as faults and folds and the plumbing system of the paleoseep. These high-resolution 3D reconstructions were carried out mainly in two outcrops where these structures are exceptionally exposed: one outcrop (approx. area of survey 300x50m) is exposed along seacliffs in the city of Santa Cruz. The other seep locality is exposed at Waddel Bluff near Año Nuevo north of Santa Cruz (approx. area of survey 250x30m). Fieldwork included structural geologic analysis combined with high-resolution geospatial analysis using new techniques developed with a Terrestrial Laser Scanning (TLS) surveying equipment. The results of these surveys offer an exceptionally high –resolution picture of the morphology of seep carbonates such as chimneys and carbonate pavements and their conduits in folded and fractured biosiliceous rocks of the late Miocene Santa Cruz Mudstone and Pliocene Purisima Formation. This pioneer approach allows quantitative, 3D modeling of the complex geomorphology of the seep precipitates and their spatial distribution, including their spatial variability as a function of geological structure.

The geospatial surveys were focused on the portions of the outcrops where the seep precipitates (low-Mg calcite) have been already sampled and partially analyzed for both petrographic and stable isotope analyses. Prior to conducting the geospatial surveys, a local geodetic framework of topographic benchmarks was first created using differential GPS technology (1 to 2 cm accuracy). The geospatial surveys were carried out with a state-of-the-art TLS, a Trimble VX Spatial Station. The laser scanner is equipped with Direct Reflex (DR) technology, a direct drive system with robotic servo-mechanisms and a built-in digital camera. Using this new technologic and methodological approach the complex geological surfaces representing the faulted and bedded rocks of the host formation and the fossil seeps were accurately measured and reproduced to create 3D models of the outcrops. Post-processing operations and interpretation of the geospatial data includes editing and merging of point clouds (surveyed points), interpolation and contouring, creation of surface meshes, and photographic rendering of three-dimensional (3D) surface models. Methods have been developed for the analysis/parameterization of the surface scans to obtain the orientation of faults and fractures and distribution, elongation and volume of the seep precipitates. These methods imply a phase of in situ structural measurements and the extrapolation of these measurements across the whole surveyed areas throughout automatic analysis of geospatial data using Trimble's Real Work Advanced 3D software. The field and post-processing techniques and methods developed for field collection of geospatial and structural data for this research project are a powerful tool that can be used for the exploration of these and other fossil and modern hydrocarbon seeps exposed elsewhere in the world.

The other focus of Dr. Aiello's research on the fossil seep precipitates has been the microanalysis of the seep carbonate samples to establish how many and what types of carbonate phases form the seeps and how the micro-fabric of the seep precipitates compares with their morphology, the location of conduits and their location relative to fractures and other potential structural conduits. This has been done with a combination of optical petrography and more recently with the use of a scanning electron microscope (SEM, Hitachi S-3400N-II). This is a modern low-vacuum Scanning Electron Microscope (SEM), equipped with an INCA Energy 250 energy dispersive X-ray spectrometer EDX. In the next year of the project this instrument will result a fundamental tool to conduct microanalyses on the different generations of seep carbonate precipitates.

The results of this research have been fully integrated in the educational activities of Dr. Aiello at Moss Landing Marine Laboratories. The methods developed to produce geospatial models of the seep outcrops are presently used in the class “Habitat Mapping” that the PI is teaching during Fall 2009. The techniques developed with SEM and EDX will part of the curriculum that will be taught during a class on electronic microscopy that Dr. Aiello will teach during Spring 2010. Undergraduate student assistants supported by this grant are learning a large range of field and analytical techniques and will be trained to the use and interpretation of the SEM and EDX data.