HYPERSPECTRAL IMAGING OF PALEOCENE CARBONATE COLD SEEPS IN THE PANOCHE HILLS, CALIFORNIA

In the Panoche Hills of California, carbonate seep deposits comprise a uniquely complete fluid migration system, preserved in the rock record. These carbonate hardgrounds, which occur as mounds, concretions and pavements, formed due to the upward seepage of bicarbonate-saturated fluid derived from various processes of methane oxidation. The carbonate seep deposits have been field mapped in the central portion of the Panoche Hills. Using remote sensing techniques to extend this mapping provides a valuable tool for understanding fluid and hydrocarbon migration.

The HyMap hyperspectral data set was centered on the field-mapped area. HyMap has 126 bands across a wavelength interval from the visible to the short wave infrared (0.45 to 2.5 mm). Carbonates have a diagnostic absorption feature centered at 2.3 mm, within the range of HyMap's accuracy. The seep-derived carbonates of the Panoche Hills mostly formed below the sediment-water interface and incorporate a significant amount of siliciclastic minerals, which complicates the spectral identification of carbonate. Spectra collected in the field provided in situ data for spectral comparison and helped to map carbonates associated with siliciclastic material using Spectral Angle Mapper classification.

By combining remote sensing data with digital elevation models, the Panoche Hills can be mapped in 3D space. The results of hyperspectral classifications can be draped over topography demonstrating the relationships between mapped geologic features and regional relief. In particular, the carbonate seep deposits provide a hard substrate that holds up the ridges of the Panoche Hills, as previously recognized in the field mapped area and as modeled in newly classified areas. Mapping via remotely sensed data has extended the boundaries of the seep system in the north and south, beyond the previously field mapped areas.