Description of the Morphology and Dynamics of a Carbonate
Sandy Tidal Flat, Shroud Cay, Exumas
Gregor Eberli and Maaike Petrie
Project Purpose
For the tidal channel sand and tidal flat complex located behind Shroud Key in the
Exuma Island Chain, this project will:
1. Quantitatively measure the channel and delta size and spatial distribution and describe
the morphology;
2. Evaluate and describe the size and distribution of sediments within the delta and
channel; and
3. Measure physical controlling processes;
4. Use seismic data to describe subsurface morphology.
Scope of Work
This project focuses on the tidal channel sand a tidal flat complex at Shroud Cay
(Figure 1). During the first year of this study we will focus on collecting information on
the sediments, flow, and wave characteristics of these areas. The second year we will
focus on analyzing data collected in Summer 2007 to describe the complex
characteristics.
Key Deliverables
Quantitative measures of the sizes, shapes, and spatial trend metrics of the
complexes, and description of the attributes (type, size, sorting) of sediments within those
bodies. Collectively, this information can be used to develop a description of the spatial
distribution of sedimentological settings at Shroud Cay.
Project Description
Construction of meaningful geologic models requires information on the size, shape,
and orientation of geologic bodies and the size, distribution, porosity and permeability of
the grain populations of these bodies. To acquire this data, this project includes four
general steps: 1) generating and analyzing facies maps; 2) exploring grains within the
morphologies; 3) assessing controlling parameters; and 4) interpretation.
1. Remote sensing data provide aerial maps that can be used to map facies and
sedimentary bodies (Figure 1). Data from these maps will be enhanced with data
collected during site visits and will assist in generating validated maps.
2. Sediment samples will provide information on the dynamics of sediment
production and transport in these systems. For this project, we will collect samples
from several environments, then analyze the samples in terms of constituents,
grain size, and sorting.
3. We will analyze data provided and collected on the bathymetry and flow
velocity. For this project, we will analyze high-resolution data available to explore
the bathymetry and we will collect data on current flow velocities in and around
the flat and channel.
4. Steps 1-3 provide an information on the distribution of different sediment types
and the geologic bodies in which they occur and the nature of currents in and
around carbonate tidal flats and channels. The final aspect of the project will
involve interpretation of the accumulated data. Using remote sensing imagery we
will place observations in the context of their environment and provide a
description on the character and controls on currents, how the sediment attributes
reflect current activity, and how all of these data can be used to better understand
and predict ancient grainstone analogs.
Expected Results
Descriptions of the attributes (size, shape, geometry, relief) of geomorphic bodies and
correlation to the processes of sedimentation.
INSERT FIGURE
Figure 1. Location of study area, Shroud Cay with inlet sand complex, tidal The inlet channel sand
complex and tidal flat indicated.