Spatial Patterns of Sediment Accumulation on a Holocene Carbonate Tidal Flat, Northwest Andros Island, Bahamas

To characterize spatial patterns of sedimentation and analyze the morphology of
part of the modern tidal flats of northwest Andros Island in the Bahamas, this
study integrated remote sensing, geographic information systems (GIS), and
carbonate sedimentology. The fundamental data are a Landsat TM image that has
been classified to create a thematic map of eight subfacies, interpreted to
represent a distinct tidal-flat subenvironment such as adjacent marine, exposed
levee-beach ridge, pond, and algal marsh. Spatial statistics of the thematic
map characterize the patterns of sediment accumulation. Quantitative analysis
highlights several interesting results concerning subfacies character and
distribution: (1) of the eight mapped subfacies, low algal marsh is most
widespread, representing 27.5% of the total area, whereas exposed levee-beach
ridge is the least widespread, accounting for 10% of the area; (2) the patches
of different subfacies have different shape complexities, with low algal marsh,
high algal marsh, and mangrove ponds being the least complex and exposed
levee-beach ridge being the most complex; (3) Markov chain analysis suggests
that lateral transitions between different subfacies are highly ordered; (4)
frequency distribution of subfacies patch area and lacunarity (gap size
distribution) data exhibit power law relationships over several orders of
magnitude, consistent with fractal characteristics; and (5) mean subfacies
patch size is highly correlated with mean distance to a tidal channel.

The fractal nature of patch size and gaps between facies illustrate that on
this tidal flat neither the size nor the spatial distribution of subfacies has
a characteristic scale. This statistical behavior is consistent with the
presence of self-organization, or emergence of pattern in the absence of a
template or external forcing. The statistical self-organization on the tidal
flat is the cumulative expression of local processes, but it becomes apparent
only through analysis of the whole system. These results are inconsistent with
models suggesting that tidal flats include a migrating complex of randomly
distributed, randomly sized subenvironments. Ancient successions that include
random patterns may reflect the more pronounced influence of forces external to
the sedimentary system, instead of an absence of those forces. The purpose of
this study is to characterize spatial patterns of sedimentation and analyze the
morphology of part of the modern tidal flats of northwest Andros Island in the
Bahamas, through the integration of remote sensing, geographic information
systems (GIS), and carbonate sedimentology.

Spatial Data Organization Information -

Indirect Spatial Reference: All locations were determined using a UTM/
latitude-longitude system.
Direct Spatial Reference: Point Spatial Reference Information
- Horizontal Coordinate System Definition - Geodetic Model: