Greg A. Ludvigson: Research Interests

My research is in stratigraphic and paleoenvironmental synthesis, using the stable carbon & oxygen isotopic geochemistry of carbonates and fossil material in the stratigraphic rock record. Recently, this work has been at the state-of-the-art Paul H. Nelson Stable Isotope Laboratory at the University of Iowa, using digitally-controlled microsampling equipment, a Finnigan Kiel III automated carbonate reaction device, and a Finnigan MAT 252 stable isotope ratio mass spectrometer. Work has been focused on Cretaceous and Ordovician global change studies that both have received NSF grant support.

Philosophical Approach to Paleoclimatology:

Paleoclimatology offers the geosciences a special claim to social relevance in helping to improve the forecasting of impending climate changes forced by the anthropogenic buildup of greenhouse gases in the atmosphere over the next two centuries. The development of terrestrial paleoclimatology remains a research frontier, having lagged earlier studies of marine records that were spurred by the DSDP and ODP programs. Nevertheless, paleoclimatic studies of terrestrial environments are more directly relevant to the human prospect attending future climate changes. Studies of high-resolution Quaternary paleoclimatic records from continental archives in ice cores, lacustrine sediments, tree rings, and spleleothems, to name a few, represent a burgeoning area of paleoclimatic research. While I have followed development of this work, and have some research experience in Quaternary paleoclimatology, my funded paleoclimatologic research has been in other periods of Earth History. Given that a 4 x CO₂ atmosphere is probably removed by less than two centuries from now, the terrestrial paleoclimatology of Mesozoic warm periods in Earth History, with special emphasis on major uncertainties regarding the behavior of the hydrologic cycle, has been a special niche in paleoclimatic research that I have elected to fill. I, and my colleagues in these endeavors are recognized for international leadership in this research frontier, and have been successful in attracting major grant support to carry out this work. We have only just begun to explore the many facets of this topic that are amenable for study.

Terrestrial paleoclimatology and paleohydrology of the Cretaceous greenhouse world:

This team research was recently awarded its second major grant from NSF. Our work has investigated d¹⁸O compositions

of paleosol carbonates from 34°N to 75°N paleolatitude, and determined that differences between the Cretaceous gradient and that predicted from modern soil waters result from a much more active hydrologic cycle in the Cretaceous. Isotope mass balance modeling suggests up to a four-fold increase in Cretaceous precipitation rates at the mid-latitude high (45°N). The new grant extends the paleolatudinal range of data collection into the subtropics and to the paleoequator.

One of my newest research ventures concerns the d¹³C chemostratigraphy of stacked Early Cretaceous calcrete paleosols in dinosaur-bearing strata of the Cedar Mountain Formation in Utah. A pilot study has shown that these deposits capture the record of marine carbon isotope excursions associated with Oceanic Anoxic Events 1a, 1b, and 1d in the Aptian-Albian stages. Diagenetic studies of individual beds are tracking changes in the d¹⁸O values of paleoprecipitation, and ¹⁸O enrichments in vadose components are being used to develop quantitative estimates of evaporative fluxes from these semiarid paleolandscapes. I am inaugurating a multi-proxy paleoenvironmental study of a bone bed from the Price River 2 dinosaur quarry, integrating diagenetic work on authigenic carbonates with phosphate d¹⁸O data from fossil tooth enamel from therapods, sauropods, and turtle scutes in the bone bed. Future plans include integration of magnetostratigraphy with isotopic chemostratigraphy for refined marine-nonmarine correlations. I am also very interested in collaborative research using radiogenic isotopes to date pedogenic carbonate components.

Selected Publications:

Ufnar, D.F., González, L.A., Ludvigson, G.A., Brenner, R.L., and Witzke, B.J., 2004, Diagenetic overprinting of the sphaerosiderite paleoclimate proxy: are records of pedogenic groundwater d¹⁸O values preserved?: Sedimentology, v. 51, no. 1, p. 127-144. [PDF]

Ufnar, D.F., Ludvigson, G.A., González, L.A., Brenner, R.L., and Witzke, B.J., 2004, High latitude meteoric d¹⁸O compositions: Paleosol siderite in the mid-Cretaceous Nanushuk Formation, North Slope Alaska: Geological Society of America Bulletin, v. 116, no. 3, p.463-159. [PDF]

Brenner, R.L., Ludvigson, G.A., Witzke, B.J., Phillips, P.L., White, T.S., Ufnar, D.F., González, L.A., Joeckel, R.M., Gottemoeller, A., and Shirk, B.R., 2003, Aggradation of gravels in tidally influenced fluvial systems: upper Albian (Lower Cretaceous) on the cratonic margin of the North American Western Interior foreland basin: Cretaceous Research, v.24, no. 4, p. 439-448. [PDF]

Ufnar, D.F., González, L.A., Ludvigson, G.A., Brenner, R.L., and Witzke, B.J., 2002, The mid-Cretaceous water bearer: Isotope mass balance quantification of the Albian hydrologic cycle: Palaeogeography, Palaeoclimatology, Palaeoecology v. 188, p. 51-71. [PDF]

Ufnar, D.F., Gonzalez, L.A., Ludvigson, G.A., Brenner, R.L., and Witzke, B.J., 2001, Stratigraphic implications of meteoric sphaerosiderite d¹⁸O compositions in paleosols of the Cretaceous (Albian) Boulder Creek Formation, NE British Columbia foothills, Canada: Journal of Sedimentary Research, v. 71, no. 6, p. 1017-1028. [PDF]

White, T.S., González, L.A., Ludvigson, G.A., and Poulsen, C.J., 2001, Middle Cretaceous greenhouse hydrologic cycle of North America: Geology, v. 29, no. 4, p. 363-366. [PDF]

White, T.S., Witzke, B.J., and Ludvigson, G.A., 2000, Evidence for an Albian Hudson arm connection between the Cretaceous western interior seaway of North America and the Labrador Sea: Geological Society of America Bulletin, v. 112, no. 9, p. 1342-1355. [PDF]

Ludvigson, G.A., González, L.A., Metzger, R.A., Witzke, B.J., Brenner, R.L., Murillo, A.P., and White, T.S.,1998, Meteoric sphaerosiderite lines and their use for paleohydrology and paleoclimatology: Geology, v. 26, p. 1039-1042. [PDF]

Ludvigson, G.A., Witzke, B.J., Gonzalez, L.A., Hammond, R.H., and Plocher, O.W., 1994, Sedimentology and carbonate geochemistry of concretions from the Greenhorn marine cycle (Cenomanian‑Turonian), eastern margin of the Western Interior Seaway: in Shurr, G.W., Ludvigson, G.A., and Hammond, R.H., Cretaceous Sedimentary Record of the Eastern Margin of the Western Interior Seaway, Geological Society of America, Special Paper 287, p. 145-173.

Marine Chemostratigraphic Record of the Late Ordovician greenhouse-icehouse transition:

This project was funded by NSF, and is an exploratory effort to examine the sequence stratigraphic architecture of a succession of marine carbon isotope excursions that are temporally associated with onset of a glacial episode in the southern hemisphere. Work has shown that positive carbon isotope excursions that occur in more nearshore carbonate strata completely starve out in more offshore sections. Dramatic d¹⁸O shifts associated with some excursions might suggest relationships to oscillations in thermohaline circulation in the Iapetus Ocean. Work to date has been on the d¹³C_carb of carbonate muds, but we are beginning work on the chemostratigraphy of bulk organic matter analyzed by EA-CF-IRMS. I also am interested in collaborative research coupling the light stable isotope chemostratigraphy with studies of other isotope systems to further general understanding of the record. Future collaborative research on paleoceanographic modeling of Ordovician epeiric seas is also a long-term goal.

Selected Publications:

Ludvigson, G.A., Witzke, B.J., Gonzalez, L.A., Carpenter, S.J., Schneider, C.L., and Hasiuk, F.H., in press, Late Ordovician (Turinian-Chatfieldian) carbon isotope excursions and their stratigraphic and paleoceanographic signficance: invited paper for special issue “Late Ordovician oceanography, tectonics, climate, and facies” edited by Mark Harris and Mike Pope, for Palaeogeography, Palaeoclimatology, Palaeoecology.

Simo, J.A. Emerson, N.R., Byers, C.W., and Ludvigson, G.A., 2003, Anatomy of an embayment in an Ordovician sea, Upper Mississippi Valley, USA: Geology, v. 31, no. 6, p. 545-548. [PDF]

Ludvigson, G.A., Witzke, B.J., Schneider, C.L., Smith, E.A., Emerson, N.R., Carpenter, S.J., and González, L.A., 2000, A profile of the mid-Caradoc (Ordovician) carbon isotope excursion at the McGregor Quarry, Clayton County, Iowa: in Anderson, R.R., Ed., The Natural History of Pikes Peak State Park, Clayton County, Iowa, Geological Society of Iowa, Guidebook 70, p. 25-31. [PDF]

Ludvigson, G.A., Jacobson, S.R., Witzke, B.J., and González, L.A., 1996, Carbonate component chemostratigraphy and depositional history of the Ordovician Decorah Formation, Upper Mississippi Valley, in Witzke, B.J., Ludvigson, G.A., and Day, J.E., eds., Paleozoic Sequence Stratigraphy: Views from the North American Craton, Geological Society of America, Special Paper 306, p. 67-86. [PDF]

Raatz, W.D., and Ludvigson, G.A., 1996, Depositional environments and sequence stratigraphy of Upper Ordovician epicontinental deep water deposits, eastern Iowa and southern Minnesota: in Witzke, B.J., Ludvigson, G.A., and Day, J.E., eds., Paleozoic Sequence Stratigraphy: Views from the North American Craton, Geological Society of America, Special Paper 306, p. 143-159. [PDF]