Luis A. González

 

Luigi Doing Java

Professor

PhD University of Michigan, 1989.
MS University of Michigan, 1983.
BS University of Puerto Rico, 1978.

Curriculum Vita

 

Research Interests

My general research interests are in:

  1. Stable isotope chemistry and its application to continental paleoclimatology.
  2. Carbonate geochemistry with emphasis on isotopic and trace elemental chemistry.
  3. Carbonate geology with emphasis on karst development and carbonate deposition in marine and karst systems.
  4. Carbonate diagenetic processes.

Current Research

  1. Quaternary Paleoclimates
  2. Cretaceous Paleoclimate and Paleohydrology
  3. Experimental Carbonate Growth
  4. Hydrocarbon Bearing Concretions in South Central Puerto Rico
  5. Sedimentology and Diagenesis of Isla de Mona, Puerto Rico

Cold Water Cave Stalagmite Fluorescent bandingQuaternary Paleoclimates

A significant portion of my current research emphasizes the utilization of the isotopic composition, mineralogy, growth history and growth patterns of speleothems (cave formations such as stalagmites, stalactites, and flowstone) to extract paleoclimatic and paleoenvironmental signals. Research has been conducted in the North American Midwest (Iowa, Illinois, Missouri, Minnesota, and Wisconsin), Asia (Vietnam and Nepal), and the Caribbean (Jamaica, Puerto Rico). Current research efforts focus on northern South America.

Particular efforts include:

The image at right is a Laser Scanning Confocal Microscopy fluorescent image of a stalagmite (image taken at The University of Iowa Central Electron Microscopy Facility). The light (bright) bands are fluorescent and the gray (dark) bands are non-fluorescent. These bands are believed to represent spring-to-summer (bright) and fall-to-spring (dark) calcite growth.  Fluorescent growth banding allow us to identify yearly growth and thus generate absolute chronologies. Image height is approximate 0.6 mm.

Selected Publications


Cretaceous Paleoclimate and Paleohydrology

This research is a collaborative effort with G. Ludvigson (Kansas Geological Survey), B. Witzke (Iowa Department of Natural Resources Geological Survey Bureau), R. Brenner (University of Iowa), David Ufnar (University of Southern Mississippi) focusing on the use of isotopic geochemistry of early diagenetic siderite and calcite to extract paleoenvironmental information. This research effort aims to improve our understanding of paleohydrology of coastal lowlands of the Cretaceous Western Interior Basin. The initiation of this research was spearheaded by Dr. Ludvigson who recognized that sphaerosiderites encountered in association with paleosol horizons in paleo-coastal (humid) lowland sequences had great potential to preserve important paleoenvironmental information.

The first major achievement of our research was documenting the systematic behavior of sphaerosiderite isotopic chemistry (Ludvigson et al., 1998) that can be used as a proxy for the isotopic composition of paleogroundwaters in coastal lowlands. We have generated large data sets for the eastern margin of the Cretaceous Western Interior Basin and for the northernmost portions of the western margin (e.g., White et al, 2000; Ufnar et al., in review) and produced a paleolatitudinal sphaerosiderite d18O trend (35 to 70° N). One of the surprises of our data set is that it implies a precipitation paleolatitudinal d18O trend that is much steeper than the modern trend. This is counterintuitive, if we assume that present day temperature-d18O relationships apply to the past. Under my direction, we have taken next logical progression and are using the sphaerosiderite d18O to quantify changes in the hydrologic cycle. Our initial approach utilized well-known amount-effect relationship with efforts led by Post-Doctoral Research Associate T. White (White et al, 2000 – Geology). Osotopic mass balance modeling efforts were led by former Ph.D. student D. Ufnar (Ufnar et al., 2002 and 2004), both approaches yield estimates that imply precipitation rates that are at least double and up to four times higher than present day rates.

As part of this research we have identified unique setting where co-occurrence of what appear to be coeval calcite and sphaerosiderite phreatic cements formed in regional aquifers, allow us to estimate regional vs. local groundwater compositions (sphaerosiderite vs. siderite and/or calcite). The regional aquifer phreatic cements are significantly lighter than nearby locally recharged humid paleosol sphaerosiderites. The regional phreatic cement data also exhibit a poleward paleolatitudinal d18O trend towards more depleted isotopic compositions. The combination of coastal lowland sphaerosiderite data with regional aquifer cement will allow to develop models to quantify contributions from local vs. regional (e.g., high altitude melts on western margin catchments, and continental effects on eastern margin broad low altitude catchments).

Our current data gathering efforts and modeling results provide us with unique means to quantify changes in the hydrologic cycle. Our empirical data from terrestrial settings and mass balance model results serve to test and validate GCM simulations and their applicability to Greenhouse world conditions. We are extending the latitudinal cover of our studies to include the sub-tropical to tropical belts and in the coming years we will be sampling Albian sequences in Texas and New Mexico, and sequences in Mexico and Colombia.

Selected Publications


Hydrocarbon Bearing Concretions South Central Puerto Rico

Petroleum exploration efforts in Puerto Rico have focused on Tertiary basins that are believe to hold the greatest potential of yielding exploitable hydrocarbons, yet, in these basins neither hydrocarbons nor potential source rocks have been discovered. The only documented occurrence of hydrocarbons in the island of Puerto Rico are carbonate concretions of the Cretaceous Cariblanco Formation. Hydrocarbons in these concretions are preserved as inclusions within calcite cements and a light mature oil is present in voids in the concretions. Recent petrographic, isotopic and organic chemistry studies by the PI and colleagues indicate that 1) significant hydrocarbons were generated during the formation of these concretions; 2) hydrocarbon generation was linked to elevated geothermal gradients and faulting associated with the emplacement of the Late Cretaceous intrusives; and 3) the fate of the hydrocarbons might have been linked to either the Cretaceous deformation of regional Paleocene to Eocene motions along the Great Southern Puerto Rico Fault Zone. Research focus on 1) the diagenetic history of concretionary carbonates in the Cariblanco and associated units, limestone units within the Cariblanco and overlying units and calcite veins associated with Cretaceous to Eocene faulting; 2) 40Ar/39Ar dating of intrusive bodies; 3) geometric and kinematic studies of faults, folds, and veins; to determine the links between a) hydrocarbon generation and migration, b) carbonate deposition (concretions, limestones, and veins), c) igneous intrusions, d) faulting and folding, e) vein formation/deformation, and f) regional tectonics.

Selected Publications

Isla de Mona

Isla de Mona is an uplifted carbonate plateau that lies halfway between Puerto Rico and Hispaniola (Dominican Republic). The island is made of Miocene to Pliocene shallow water carbonates and is fringed on its western and southern sides by Pleistocene reef terraces.

Research on Isla de Mona focuses on the diagenesis of the Miocene to Pliocene carbonates. Extensive cavern development and massive dolomitization of these carbonates (Isla de Mona Dolomite and Lirio Limestone) are early diagenetic features and are associated with repeated sea-level oscillation. During the Miocene and earliest Pliocene the island was at or near sea level. No definitive middle or late Pliocene  deposits are known and it is likely that the island remain exposed throughout much of this time.  A number of Pleistocene fringing-reef deposits (terraces) can be found at elevations ranging from over 60 meter to 6 meters indicating that the island was uplifted in episodic fashion during the Pleistocene.

The Miocene carbonates of Isla de Mona exposes the only known late Miocene reef complex in the Caribbean.Isla de Mona Este

Selected Publications



Current Graduate Students

Ph.D.

M.S.

Undergraduate

Former Graduate Students

University of Kansas

Ph.D.

M.S.

University of Iowa

Chris, Luis, Ruben 2002 Commencement
  • Roger Gomez - MS 2004
  • Heather Steffe - MS 2004
  • Vionette DeChoudens-Sanchez - MS 2003
  • Heidi Dowd - MS 2003
  • Leah Young - MS 2002
  • Jennifer Obrad - MS 2002
  • Mary Ellis - MS 2001
  • Aaron Suzuki - MS 1998
  • Mary Clare Jones (Maxwell) - MS 1997
  • Suellen Leimkuehler - MS 1996
  • Randy Locke - MS 1994
  • Hector M. Ruiz - MS 1993
  • Jeffrey A. Dorale - MS 1992
  • Paul K . Knoerr - MS 1991

It's time for Café