Jonathan B. Sumrall

Student-Designed Mapping Project as Part of a Geology Field Camp.

ABSTRACT During the summer of 2012, the Louisiana State University (LSU) field camp program was affected by close proximity to the large Waldo Canyon Fire in Colorado Springs, CO, as well as by a fire incident on the field camp property. A mapping exercise was created that incorporated spatial data acquired on the LSU property to investigate research questions that were developed by the students. The ownership of the design, implementation, and reporting of the project from start to finish generated strong personal interest from the students and led to enhanced academic performance. Four of the six student groups that conducted this exercise chose to investigate questions related to wildfire on the property. The influence of the events of the summer was strong in shaping their interest and project design. Furthermore, the connection to the wildfire events and the camp property itself strengthened the interest level of the students and the sense of ownership of the projects. While the specific events of that summer field camp program are not possible to re-create, we show here that the strategy of allowing students to control as much of the project design as possible is a good strategy for enhancing student interest and thus strengthening the achievement of learning objectives. This can be achieved while still providing students with the academic content as appropriate for the curriculum of a given course.

Microbial mixing zone dolomitization and karst development within Isla de Mona Dolomite, Isla de Mona, Puerto Rico

Modification of the mixing zone model to include microbial processes that promote dolomitization explains many of the petrographic, isotopic, and outcrop observations found on Isla de Mona. Large flank margin caves at the contact between the Isla de Mona Dolomite and the capping Lirio Limestone formed during prolonged, likely episodic, periods with a stable lens position. These periods would produce a stable halocline. The halocline is hypothesized to be the zone of dolomitization in the microbial mixing zone model. Collection of organics at the density interface of the halocline coupled with sulfate reduction by sulfate-reducing bacteria would establish a geochemical environment that promotes dolomitization of the precursor limestone. This microbial community and geochemical environment would overcome the kinetic and thermodynamic barriers associated with the previous mixing zone model.

Unusual polygenetic void and cave development in dolomitized Miocene chalks on Barbados, West Indies

prism, about 125 km east of the Lesser Antilles volcanic island arc. The island is approximately 23 x 32 km, with 432 km2 of area (Fig. 1). Glacioeustasy and episodic tectonic uplift have created a series of limestone terraces fronted by cliffs (e.g. Humphrey, 1997). The island conforms to the Carbonate Island Karst Model (CIKM) classification of a composite island (Mylroie & Mylroie, 2007). The strata of the island from oldest are: 1) Eocene, tectonically deformed deep-sea clastics of the Scotland Formation; 2) flat-lying Miocene chalks and marls of the Oceanics Group; and 3) a series of Pleistocene carbonate terraces that are pervasively karstified (e.g., Speed, 1990; Taylor & Mann, 1991; Machel, 1999; Jones & Banner 2003). The clastics are exposed in the Scotland District (Fig. 1), and stream caves have developed in the Upper Coral Reef Terrace. The most conspicuous surface and near-surface post-depositional attributes of the Pleistocene carbonates are karst features, which include several dozen deeply incised gullies (dry valleys), abundant sinkholes, and caves of various sizes and origin (Day, 1983; Machel, 1999, 2011; Machel et al., 2012).

Cave development within a paleosol breccia in the dolomitized Seroe Domi Formation, Aruba, Lesser Antilles

Abstract Payoff Cave, found within dolomitized sections of the Seroe Domi Formation on Aruba, provides a set of diagenetic observations unique to island karst. Paleosol breccia found as wall and ceiling rock and as bedrock pillars within Payoff Cave was determined to be low-Mg calcite in mineralogy with clasts of dolomitized host limestone. Payoff Cave is interpreted to be a flank margin (FM) cave based on morphologic features. The relevant diagenetic history of this section of the Seroe Domi is: (1) dolomitization and initial cave formation, (2) collapse and paleosol breccia formation within the initial cave, (3) reoccupation of the mixing zone to form a new FM cave within the more soluble calcitic paleosol breccia, and (4) cliff retreat and exposure of Payoff Cave as found today. Dolomitization, karstification, and the presence of a paleosol breccia combine in a complex diagenetic history on Aruba.