121 Precambrian Geology

Tuesday, 30 October 2007
8:00 AM - 12:00 PM

RECONSTRUCTING ARCHEAN CLIMATE WITH HARD AND MODIFIED KINFLOW

Paper number: 121-3
Program: Technical Sessions
Time: 8:30 AM – 8:45 AM

Authors

Abstract

We seek to reconstruct Archean climate history. Two tools play a central role in our present efforts to do so: the Holistic Archean Research Database (HARD) and an extended version of KINFLOW. HARD is a repository of data on Archean rock samples. We are actively populating this database and hope to incorporate all extant Archean data. The extended version of KINFLOW is a one-dimensional reactive transport model configured to model the mineralogical evolution of weathering profiles.

In the present project, we simulate the weathering of parent materials, e.g. basalt, to form soils. Boundary conditions are chosen to coincide with plausible conditions during the Archean. Atmospheric composition is an important variable that affected soil profile evolution in that eon. Thus, we vary simulated oxygen and carbon dioxide levels from negligible levels up to the maximum values permitted by published empirical constraints. However, we are primarily interested in the effect of changes in temperature on the evolution of soil profiles.

Data regarding all known paleosols from the Archean (and Paleoproterozoic) as well as their presumed parent materials are present in HARD. We will present results of weathering simulations initiated on several of these parent materials at 5, 25, and 70 degrees Celsius. We will compare simulation results to known paleosol profiles and seek to infer the likely temperature range of weathering during Archean (and Paleoproterozoic) soil formation. Results from these comparisons, and similar ones involving sedimentary rocks and inferred parent material for the sediments, will be used to begin to develop a more nuanced picture of Archean temperature history than has previously been revealed.