Carbonate depositional environments are inherently heterogeneous because of the superposition of sedimentary and diagenetic processes during successions of relative sea level changes. Projects in the modern environment use a combination of various types of remote sensing data and surface samples to capture the spatial trend metrics of sedimentary bodies. Surface samples from northwestern Great Bahama Bank are intended to refine the facies maps of this classic modern platform system.
Understanding flow, compartmentalization and mineralization in reservoirs depends on knowledge of the 3-D architecture of sedimentary structure and fracture network in the rock volume around the borehole. Several of our projects aim to increase our understanding of the lateral and vertical heterogeneity of facies and fractures. To achieve this goal, we have developed a new generation of 3-D Ground Penetrating Radar to retrieve the sub-meter scale variability of facies and flow units from Pleistocene grainstone shoals in the Miami Oolite and for fractures in several locations around the world. Seismic data from various regions are used to examine the evolution of carbonate systems in different tectonic settings and assess the influence of tectonic activity, sea level changes and sediment supply on the carbonate depositional system. Currently, we study seismic data from the Bahamas-Cuba foreland basin to decipher carbonate platform drowning as a result of increased subsidence during the formation of this foreland basin, and to delineate the evolution of the Gulf Stream from sediment drifts in the Bahamas region.
Reservoir heterogeneities and the large-scale distribution of reservoir quality dolomite have been the focus of projects in the Mississippian Madison Formation. Currently we are assessing the dolomitization processes in the Madison Formation and the correlation of the dynamics of the evolving foreland basin on the evolution of these ramp carbonates. In addition, we continue our research in relating mechanical stratigraphy to sequence stratigraphy. These projects will provide us with a methodology to predict to a certain degree the fractures from facies and stratigraphic information.

Windward carbonate platform margins are often assumed to stack vertically during sea level highstands but recent studies document a more complicated architecture of onlapping and overstepping wedges that stack laterally and prograde seaward. In addition, there is growing evidence that Pleistocene sea-level highstands contain higher frequency, suborbital sea-level fluctuations Both factors potentially contribute to significant facies and stratigraphic heterogeneity along windward margins. The objectives of this project are:
1. To address the fundamental question of how high frequency sea-level changes influence the stratigraphic facies heterogeneity.
2. To assess windward margin stratigraphy and heterogeneity through mapping the modern facies and coring the Pleistocene parasequence-scale stratigraphy alongthe ~200 km windward margin in the Exumas, Bahamas.
3. To deliver a baseline for improved carbonate heterogeneity estimation and reservoir characterization in windward margin settings.

The principal objective is to determine the facies geometry, diagenesis, and petrophysics of carbonate rocks subjected to repeated cycles of freshwater and marine diagenesis from regional uplift and high-amplitude changes in sea level. The Pleistocene reefs that developed over the past 2.5 million years provide one of the best opportunities to study the complex three-dimensional architecture and controlling factors of fringing reef development during high frequency sea level cycles. A series of laterally stacked reef-skeletal clinothems document successive deposition during uplift and changes in available accommodation space with relative sea-level changes.

Quantitative sedimentological and diagenetic data sets are essential building blocks of forward models and reservoir quality studies. This study focuses on Glover’s Reef, a Caribbean atoll that records multiple sea-level highstands within the last 500,000 years, preserving a variety of depositional facies and an early diagenetic overprint.Data sets collected in this study include petrographic data from rotary cores to identify depositional facies and diagenetic features, fluid inclusion Tm ice data to identify the origin of diagenetic features, and petrophysical measurements to evaluate phi/K relationships. These data sets are complemented with point counting of grain, cement,and pore types. In addition, Amino Acid Racemization (AAR) dating is employed to improve age control on the stacked reef sequences.

In this ongoing study, a new model for the mixed carbonate-siliciclastic system of the Neuquén Basin has been proposed. This model is based on outcrop and seismic data (year 1) and a detailed assessment of the heterogeneous reservoir properties in subsurface data (year 2). Reservoir heterogeneities are the result of the complex variations of facies and diagenetic history. These variations can only be observed adequately in outcrops but must be considered when making larger scale seismic interpretations. Seismic images can be calibrated to the observed smaller scale variability of depositional geometries in outcrop by using a key tool: Synthetic seismic models. The goal of the proposed research effort is to develop a predictive model that incorporates the outcrop variability of the Upper Jurassic-Lower Cretaceous mixed system in the Neuquén Basin.

Observations from submersible dives (Grammer et al., 1993) have documented scars in the upper slope of Great Bahama Bank. More recent, high-resolution bathymetry maps revealed a slump scar on the magnitude of 100 meters in relief on the toe-of-slope of Great Bahama Bank (Grasmueck et al., 2007). This slump scar at very toe-of-slope is imaged in its entirety with multibeam data collected during the CARAMBAR cruise. Other kilometer long scars are visible along the slope of both Little and Great Bahama Bank. Slope failures of this magnitude and at this low of a position on the slope have not been reported and are hard to explain. This study aims to describe the geometries of these slope failures and to give an explanation for why they occur.

Recent studies document that the lower slopes of Great Bahama Bank are sites of extensive cold-water coral growth (Grasmueck et al., 2006, 2007). In some areas, the average density of coral mounds is 18 mounds/km2. These mounds can be as high as 120 meters and form kilometer long linear ridges. These findings are based on surveys with an autonomous underwater vehicle in five areas in the Straits of Florida, covering approximately 80 km2. The multibeam data collected during the CARAMBAR cruise reveals an even greater abundance and diversity of mound architecture. Furthermore, the data set allows questions about the punctuated stratigraphic occurrence and the internal growth pattern of such mounds to be addressed.

The primary objective of this international project is the characterization of the morphology and geometry of the carbonate slope system and its relationship to sedimentary processes. Several aspects within this objective can be investigated using the comprehensive data set provided by the CARAMBAR cruise. In addition, the seismic data can be calibrated to the lithology and stratigraphy of the ODP Legs 101 and 166 and Küllenberg cores. Based on the available data, the following sub-projects will be conducted by the participating institutions.

The multichannel seismic survey collected during the CARAMBAR cruise is of higher frequency and resolution than the site surveys conducted in preparation for drilling ODP Legs 101 and 166. The 25 cubic inch air gun images the slope with unprecedented clarity. Because the seismic lines were traced across the ODP dill sites where completely cored wells penetrated strata as far back as the Lower Cretaceous (Site 627), a unique opportunity arises for a refined correlation between the cores and seismic data. This refinement will be best in the sites along theBahamas Transect at the western prograding margin of Great Bahama Bank because, in these sites, a vertical seismic profile was shot after drilling and complete logging suites were run in all of the wells (Eberli et al. 1997). With this refined correlation, we will address some fundamental questions in regards to the control of the reflectivity in these strata and the development of the physical properties.

We will initiate a study that combines satellite imagery and field mapping of the Miocene (?) Los Haitises platform in northeastern Dominican Republic. The Los Haitises platform is a ~1000 square kilometer platform composed of shallow water carbonates. The uplifted platform has been exposed to intense meteoric dissolution since exposure in the mid-Pliocene (?). A series of karst pinnacles and ridges with intervening sinkholes and dissolution depressions cap the platform. Our initial reconnaissance of road cut exposures along a new highway indicates that these platform limestones are likely age equivalent with the late Miocene to early Pliocene deposits further east in the Cibao Basin.