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Data report: penetrometer measurements of in situ temperature and pressure, IODP Expedition 3081

H. Long,2 P.B. Flemings,3 B. Dugan,4 J.T. Germaine,5 and D. Ferrell6


We conducted temperature and pore pressure measurements using the Davis-Villinger Temperature-Pressure Probe and the temperature/​dual pressure probe penetrometers during Integrated Ocean Drilling Program Expedition 308. In Ursa Basin, 18 measurements were used to determine that the geothermal gradient at Site U1324 is bilinear. The temperature gradient is 18.6°C/km in lithostratigraphic Unit I and 16.7°C/km in Unit II. Based on nine measurements at Site U1322, the geothermal gradient is 21.9°C/km. In Brazos-Trinity Basin IV, the geothermal gradient at Site U1320 is 23.1°C/km. In Ursa Basin, significant overpressures (overpressure ratio = ~0.7) are observed in the sediments above ~200 meters below seafloor (mbsf) at Sites U1322 and U1324. At Site U1324, pore pressure decreases with increasing depth between 200 and 300 mbsf. Below 300 mbsf and within lithostratigraphic Unit II, overpressure is approximately constant (~1 MPa). Unit II is composed of silty claystone interbedded with beds of silt and very fine sand. In Brazos-Trinity Basin IV, only two penetrometer deployments were made and the data are inconclusive.

1 Long, H., Flemings, P.B., Dugan, B., Germaine, J.T., and Ferrell, D., 2008. Data report: penetrometer measurements of in situ temperature and pressure, IODP Expedition 308. In Flemings, P.B., Behrmann, J.H., John, C.M., and the Expedition 308 Scientists, Proc. IODP, 308: College Station, TX (Integrated Ocean Drilling Program Management International, Inc.). doi:10.2204/​iodp.proc.308.203.2008

2 ExxonMobil Upstream Research Company, 3120 Buffalo Speedway, Houston TX 77098, USA.

3 John A. and Katherine G. Jackson School of Geosciences, The University of Texas at Austin, 1 University Station C1100, Austin TX 78712-0254, USA.

4 Department of Earth Science, Rice University, Houston TX 77005, USA.

5 Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, Cambridge MA 02139, USA.

6 Integrated Ocean Drilling Program, Texas A&M University, College Station TX 77845, USA.

Initial receipt: 15 June 2007
Acceptance: 16 April 2008
Web publication: 29 October 2008
MS 308-203