Jonathan B. Sumrall
Assistant Professor
Sedimentology, Carbonate Petrology, & Isotope Geochemistry

My interest in sedimentology originates from a childhood spent on the Gulf Coast of Mississippi.  My interest in carbonate environments (mainly coral reefs) began on an undergraduate field trip to the Bahamas. My master’s research at the University of South Florida focused on a thermal karst region in Southwestern Romania. I also worked on a small side project inventorying cave minerals on San Salvador Island, The Bahamas. I started working in the sinkhole/environmental consulting industry in Florida after my master’s degree.
I started my PhD at Mississippi State University after a year of working in the private industry. I decided to tackle the century old dolomite question, against my advisor’s advice. I made a keen observation while on a cave mapping expedition on Mona Island off the coast of Puerto Rico the summer before starting my PhD. I noticed that there were extensive caves developed along the contact between differing carbonate units on Mona Island. The older, lower unit was known as the Mona Dolomite and was overlain by the younger Lirio Limestone. A return trip to Mona Island coupled with visiting 5 other Caribbean islands eventually shaped my understanding of these paradoxical carbonates.
My current research investigates early carbonate deposition and diagenesis associated with microbial reactions. The inspiration behind this research originates from somewhat of an accident. The rocks that I examined during my dissertation contain significant amounts of organic material. This organic material was essentially ignored by previous researchers.

The contribution of microbial communities and organic material to the maturation of these rocks is poorly understood. My future research will focus on examining rocks that are known to be microbial in origin. Comparing the geochemical signals in these known microbialites to older rocks should shed light on the changes associated with diagenesis in carbonate rocks.
My second area of research includes cave and karst geochemistry, especially hydrogeology, mineralization, and surface denudation. Caves are natural laboratories where conditions are kept relatively constant. Mineral precipitates can originate from a relatively simple mixture of biological activity and chemical oversaturation). These mineral deposits can then be used as proxies for the paleoclimatic signal during deposition.

In addition, caves provide a “3-D” view of a rock unit. Traditionally, geologists use outcrops and road cuts to visualize the 3-D nature of geology. Caves penetrate into a rock unit, allowing access to more spatially diverse samples. Cave surveying is conducted in order to determine the exact position of sampling locations. Two of my hobbies are cave cartography and cave surveying. I am currently a member of several cave mapping expeditions, including locations such as: the Yucatan Peninsula; Barbados; Mona Island, Puerto Rico; Florida; Haiti; and Jamaica.
My hobby of caving and mapping contributes to my research agenda. I am taking a group of students to Barbados to assist with cave mapping and help begin a new phase in my research agenda. Most of these new projects will examine early carbonate diagenesis; however, several others will focus on hydrocarbon migration on Barbados, microbial reactions associated with natural oil seeps, and clastic diagenesis of sandstones and shale on Barbados.

Overall, my research is a practical field-based approach that couples geochemical and petrographic observations in order to gain a greater understanding of the young carbonate system. It is not unusual to see me rappelling down a cliff on a tropical island in order to get the “perfect” sample. The allure of tropical islands, practical research, and overall excitement about my research has been one of my greatest motivators for students that work with me

Jonathan B. Sumrall
Department of Geography and Geology
P.O. Box 2148
Huntsville, TX 77341

Phone: (936)-294-1593
Personal Webpage:

GEOL 1304
Historical Geology
GEOL 3330
GEOL 4440

Carbonate Petrology and Diagenesis
Isotope Geochemistry
Cave and Karst Geology

Contact Us: Department of Geography & Geology, Sam Houston State University, Lee Drain Building Suite 332, Hunstville, TX 77341