Basin Analysis:

Basin Analysis is the three dimensional reconstruction of regional depositional dynamics in a sedimentary basin. It produces a 3-D geometric depositional history of the basin, including information on:

Utility:

Sediment source

The first task in characterizing an ancient basin is the identification of source regions. This requires that their weathering products be identified in the sediment, as in the Cretaceous Laramide basin at right.



Garnets as framework clasts in point bar from Mineral Resources and Geofluids

Direct identification of lithic fragments:

These directly indicate source rocks and provenance. Specifics:

ZTR index: zircon, tourmaline, and rutile are especially stable heavy minerals that maintain integrity through multiple sedimentary cycles. As a result, they increase in abundance as sediments mature. Relative abundance is referred to as the ZTR index. Sediments that have endured longer transport such as beach (right) and subtidal clastic deposits.

Transport direction

These are indicated by the distribution of sediment textures:


Paleocurrent analysis

Even in a modern environment, characterizing general current direction is problematic if all we have access to are single small points of observation. For example, in the flood plain of a meandering stream, current, at any given point, may be flowing in any direction. It is only by sampling many localities that we develop a general sense of the current direction. Reliable reconstruction of ancient current directions, likewise, requires hundreds of measurements of cross beds, current ripples, etc. Unlike modern observations:

Rose diagram: Commonly, paleocurrent data are graphically represented on circular graphs that summarize current vector data. The diagram takes the form of a radial histogram divided into convenient angular increments (5º, 20º, etc.) Number or percent of measurements that fall in each section are graphed (like a histogram). Dominant current direction will be the largest "pie slice." Secondary signal that might not be readily apparent can often be seen.

Stratigraphic cross sections

Unlike a geologic cross section in which surface topography and structure are shown, a stratigraphic cross section (right) omits surface topography and suppresses structural information or displays it only schematically. All data are aligned along a shared datum or elevation. Intended to emphasize:

Fence diagram

Stratigraphic cross sections are two dimensional by definition. To illuminate three dimensional patterns, a common convention is the fence diagram where a series of cross sections is arranged like fences on a map. To be intelligible, these usually must be simplified from standard 2D sections and scaled appropriately.

Stratigraphic maps

Show the aerial distribution, configuration, and aspect of a stratigraphic unit or surface compressed into two dimensions. There are many aspects of stratigraphy that can be mapped: