Paleolatitudes and Paleoclimates of Laurentia and Its Accreted Terranes since 1.8 Ga

Paleoclimate is of fundamental importance to two issues of major societal concern: natural resource depletion and climate change. 

There is no end in sight for projected increases in global demand for hydrocarbons, uranium, aluminum, nickel, iron, lead, zinc, copper, and hundreds of other commodities.  The formation of each on the above list is now known to be controlled, in part, by paleoclimate.  Carbonate-hosted lead zinc deposits, for example, require evaporative climatic conditions, whereas Neoproterozoic sedimentary iron formations are only found in association with low-latitude glacial deposits.  To help ensure that future supplies keep up with growing demands, it is important to find out where undiscovered deposits are likely to be found.  For this, we need to understand both the paleoclimatic controls of deposit formation and the paleoclimate history itself, i.e. the process and the specifics. 

Concerns about global warming have raised general awareness of atmospheric general-circulation models (GCMs) and especially the validity of model predictions.  Paleoclimate here plays a critical role, in providing data on actual conditions in the deep past.  A GCM that can't reproduce what is known to have happened is in need of refinement. Conversely, the more such tests that a GCM passes, the more plausible and weighty its predictions become. 

Paleoclimate and a second variable, paleolatitude, are closely linked in Earth history.  The correlation between present-day latitude and present-day climate is clear: the equatorial belt is hot and wet, the poles are cold and dry, and so on.  These correlations pertain back in time, although subject to three complications. The first of these, of course, is that "real" climate change does happen, most evident through the glacial-interglacial cycles of the Pleistocene.  Without North America moving appreciably, the Laurentide ice sheet advanced as far as 40°N, then shrank bank to almost nothing.  The second complication, which comes to dominate at longer time scales, is the ever-changing configuration of continents: a landmass might simply drift from one climatic belt into another, Gondwana over the South Pole in the Paleozoic.  The third complication is raised by the hypothesis of inertial-interchange true polar wander. This holds that at times (e.g., late Neoproterozoic), the entire lithospheric shell, consisting of 20+ plates, rotated en masse such that a point that started at the pole ended at the equator.  Together, these three complications demand that paleoclimate and paleolatitude be tracked individually, and that anomalous data not be dismissed out of hand.

This Research Opportunity is aimed at candidates with expertise in both paleomagnetism and paleoclimatology, and a penchant for scientific synthesis.  The goal will be to synthesize the paleoclimates (temperature, precipitation) and paleolatitudes of Laurentia and its accreted terranes, from formation of the cratonic core at about 1.8 Ga to present.  The results will need to be packaged so that future users can quickly assess and compare the paleoclimate and paleolatitude of a given region for a given time, with caveats as appropriate.  The successful applicant will have considerable latitude in fleshing out the research and publication plan.  The Lower 48 and Alaska will be emphasized but relevant data from Canada, Mexico, and elsewhere will, of course, need to be considered.  The research will be linked with an ongoing synthesis of tectonic history by the Research  Advisor.  Whereas the main goal and highest priority is a synthesis, focused research on a key gap in the paleomagnetic or paleoclimate record will be encouraged.  Applicants should discuss the merits, feasibility, and logistics of some possible targets.

Proposed Duty Station: Anchorage, AK

Areas of Ph.D.: Geology, geophysics

Qualifications: Applicants must meet one of the following qualifications: Research Geologist, Research Geophysicist

(This type of research is performed by those who have backgrounds for the occupations stated above. However, other titles may be applicable depending on the applicant's background, education, and research proposal. The final classification of the position will be made by the Human Resources specialist.)

Research Advisor(s): Dwight Bradley, (907) 786-7434, dbradley@usgs.gov

Human Resources Office contact: Candace Azevedo, (916) 278-9393, caazevedo@usgs.gov

Summary of Opportunities