Growth of Active Fault-Propagation Folds in Late Quaternary Sedimentary Basins, Central and Southwest Japan

E. C. Cannon
University of Colorado, Department of Geological Sciences, Boulder, CO

Japan offers an ideal location to study the growth and linkage of fault-propagation folds and blind thrust faults in transpressive stress regimes. Blind thrusts near Tokyo and Osaka produce faultpropagation folds at shallow depths. These folds deform Late Quaternary fluvial and shallow marine sediments, and volcanic ash layers. By formulating a detailed growth history and stratigraphic development for these active fault-propagation folds, I can provide a modern analog for fault-propagation folding potentially useful in evaluating fold growth in ancient sedimentary basins.

I plan to integrate ultrahigh resolution P-wave seismic reflection profiles, stratigraphy from borehole data, and geomorphic surveys to evaluate the growth and stratigraphic development of faultpropagation folds. P-wave seismic data image reflectors spaced at submeter scales. In Osaka, a 230 square mile section contains over 9000 boreholes with typical depths to 130–230 feet (occasionally 1950–2600 feet). Stratigraphic ages in the boreholes are constrained by age-dated ash layers and shallow-marine sedimentary layers correlated to eustatic changes. During summer 2001 fieldwork, I will document the geomorphology of the folds. I will use fault-propagation fold and geomorphic modeling programs to develop a comprehensive model for fold growth and stratigraphic development.

Fault-propagation folding can play a key role in producing hydrocarbon reservoirs. Rapid fault propagation, bed-parallel shear, and changes in sedimentation and erosion rates on the fold limbs are important factors in reservoir development that can be evaluated first in Japan, and then in other modern and ancient sedimentary basins.

AAPG Search and Discovery Article #90902©2001 AAPG Foundation Grants-in-Aid