Stephen S. Harlan

Research Interests:

• Structural geology, strain analysis, and the evolution of thin- and thick-skinned thrust belts; particular emphasis on the interaction between both structural styles in southwestern Montana and northwestern Wyoming.
• Structural and tectonic evolution of western North America—Proterozoic to Recent
• Origin and distribution of large Tertiary to Recent calderas and associated volcanic systems in the in the western U.S.
• Paleomagnetism/Rock Magnetism:

o Precambrian paleomagnetism of North America with emphasis on the Middle and Late Proterozoic and reconstruction of Proterozoic continental configurations; application of ⁴⁰Ar/³⁹Ar geochronology to dating the age of remanence acquisition in igneous and metamorphic rocks. More information here.

o Timing of thin-skinned thrust belt and basement-involved deformation in the central and southern Rocky Mountains using paleomagnetism and high-precision ⁴⁰Ar/³⁹Ar geochronology.

o Application of paleomagnetism to identification and quantification of vertical- and horizontal-axis (tilt) rotations in contractional, extensional and strike-slip regimes.

o Use of anisotropy of magnetic susceptibility (AMS) and related techniques in the analysis of structural fabrics in igneous and metamorphic rocks, and as primary flow indicators in ash-flow tuffs and dikes.

o Use of paleomagnetism to identify and/or constrain the temperature of emplacement of pyroclastic flows, breccias, and related deposits.

o Rock magnetic investigations of soil/loess sequences as a proxy for records of Quaternary climate change.

• Geochronology:

o Use of ⁴⁰Ar/³⁹Ar and U-Pb geochronology to study the thermal evolution of igneous and metamorphic terranes.

o Use of ⁴⁰Ar/³⁹Ar geochronology of Late Cretaceous/Tertiary volcanism in the western U.S.

o Use of ⁴⁰Ar/³⁹Ar, U-Pb, and Sm-Nd isotopic systems to date the age of emplacement of Precambrian mafic dikes and sills.

o Application of the close relationship between laboratory unblocking temperatures of magnetic phases and the closure temperatures of common potassium-bearing minerals used in ⁴⁰Ar/³⁹Ar dating in order to date the age of remanence acquisition in paleomagnetic studies.

o Dating of precious metal deposits and thermochronologic studies of basement rocks in central Alaska by the ⁴⁰Ar/³⁹Ar, U-Pb, and fission track methods.

· Applications of Geographic Information Systems (GIS), Database Systems, and remotely sensed data to the solution of geologic, structural, and tectonic problems, including the production of digital geologic maps.

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