1. Anatomy of a Half Graben, Northwestern China
Wan Yang, Geology Dept., Wichita State University
Fluvial-lacustrine sediment fill in rift basins are important petroleum source and reservoir rocks. Our investigation revealed the complex events and controlling processes of sedimentation in a half-graben ~260 million years ago.
Fluvial & eolian deposits
The sequence of events, from bottom/old to top/young, in the field photo include:
Shallow lake carbonate deposition;
Lake withdrawal & erosion, forming Unconformity 1;
River peneplanation and deposits;
Landscape stabilization and soil formation under arid climate over a long period of Unconformity 2;
Renewed river and loess deposition under a dry and windy climate.
Unconformity 2
Ancient calcareous soil
Fluvial sandstone
Unconformity 1
Lacustrine limestone