Diagenesis continuously alters carbonate rocks and consequently their petrophysical properties. Our research projects have thus a double focus; one to understand the diagenetic processes, and two, to relate the diagenetic alterations to the resulting rock properties. 
Modern sediments on Great Bahama Bank and elsewhere provide baseline information about the geochemical signature of “unaltered” carbonate platform sediments. Cores from the shallow subsurface along the western margin of Great Bahama Bank and in Florida document the effects of early diagenesis on porosity, velocity, and permeability in platform carbonates and grainstone shoal complexes in particular. The geochemical studies of the dolomites and limestones from deeper cores on Great Bahama Bank and the Marion Plateau are ideal to examine the influence of burial diagenesis on the petrophysical properties and to assess the fluid flow in isolated carbonate platforms. Deeply buried rocks that were later uplifted such as the Mississippian Madison Formation underwent several episodes of diagenesis from shallow to deep burial. Our current geochemical projects in this formation try to unravel these different episodes and to document the importance of each event on the reservoir quality of the formation. In addition, we test the applicability of geochemical tracers, in particular δ13C for the stratigraphic correlation of the widely spaced section in Wyoming and Idaho and to other sections around the world.

This project investigates the role of sediment-associated microbial biofilms on calcium carbonate precipitation with the goal of better understanding the physical, chemical and microbiological conditions involved in the formation of large-scale ooid shoals. Towards this end we seek to:

• Quantify the amount of biofilm coating carbonate grain surfaces and assess the stability/adherence of sediment biofilms through column flow-through and agitation experiments.

• Characterize metabolic processes associated with carbonate precipitation through metabolic gene profiling of active, non active, and mat stabilized sediments.

• In vitro precipitation experiments to assess the roles of microbial metabolism and biofilm/EPS in carbonate precipitation.

Objectives:

• Applying multiple geochemical proxies to stalagmites from the Bahamas offers the opportunity to better understand the paleoclimate of the region.

• Initial results support the idea that cold periods in the North Atlantic during then last glacial period (Heinrich events) are intervals of aridity followed by a shift to a much wetter climate in the sub-tropics. Additionally, these periods were extremely dusty, a phenomenon which could have actually induced climate change.

• The methods proposed here are additionally applicable for a range of studies including diagenetic histories in all types of carbonates.

A fundamental argument used to support the idea that large changes in the C isotopic record during specific periods of time are related to changes in the global carbon cycle is that similar changes in the C isotopic signals are seen on a global basis during ancient time periods. However, we have shown in a recently published paper that this is not the case (Swart and Kennedy, 2012). In fact similar changes in the C isotopic composition were evident in Pleistocene carbonates collected from both the Pacific and the Atlantic which are related to freshwater diagenesis connected to sea-level changes and not global changes in the carbon cycle. They appear to be similar in nature to C isotope patterns
observed in the Neoproterozoic which have been interpreted as being original in nature. Within the Neoproterozoic sections other isotope systems (B, Mg, and Ca) have also been investigated and suggested to be original in nature. The purpose of the project outlined here will be to investigate how changes in other isotopic systems (Ca, Mg, and Bisotopes) in the well-known diagenetic zones are documented in comparatively recent rocks (Pleistocene-Miocene) and ascertain whether these systems can be usefully applied to the other geological time periods. The results of this study will be of use in applying these new isotope systems towards the understanding of diagenesis in carbonates.

Objectives:

• Manually precipitate calcium carbonate under varying environmental conditions with a control on all factors that have a role in the final composition.

• To quantify the variation in Δ47 CO2 with changes in precipitation rate in order to evaluate the effect on clumped isotope measurements.