QUANTIFYING FACIES PATTERNS, SHAPES AND SIZES BY INTEGRATING REMOTE SENSING, GIS, AND CARBONATE SEDIMENTOLOGY: THREE CREEKS AREA, ANDROS ISLAND, BAHAMAS

Analysis of modern analogs is one of the few means by which high-resolution spatial complexity of sedimentary systems can be described. This study integrated Landsat TM data, geographic information systems (GIS), and carbonate sedimentology to characterize, analyze, and understand the morphology of the Three Creeks area of the modern tidal flat of northwest Andros Island in the Bahamas. The Landsat TM image was classified to create a thematic map of eight spectrally distinct classes. By comparison with published maps and aerial photographs, each class was interpreted to represent a distinct tidal flat subenvironment. The spatial statistics of the digital thematic map of subenvironments then were analyzed to characterize the shapes, sizes, and patterns of sediment accumulations.

The quantitative analysis reveals several interesting results concerning character and distribution of subenvironment classes, including: 1) different classes have different mean size; 2) different classes have different shape complexities, with low algal marsh being the least complex and exposed levee/beach ridge being the most complex; 3) classes with more ordered lateral transitions (lower entropy) are generally characterized by more complex shapes; and 4) mean area for each facies can be predicted (R²=0.78; RMSE=0.99) from parameters that may be discernable from ancient successions. Markov analysis of lateral transitions among classes suggests that the tidal flat is a highly ordered system, in contrast with the vertical patterns of similar facies in ancient analogs that may be statistically disordered or only marginally non-random. These results are inconsistent with models that suggest that tidal flat subenvironments are a ‘facies mosaic’ or are randomly distributed. The disorder in facies patterns in ancient successions may reflect the influence of mechanisms external to the sedimentary system or the processes inherent to means by which sediments are preserved.