Abstract

The character and quantity of bioturbation preserved on bedding-plane exposures reflect a number of interrelated factors, including sediment accumulation rate, oxygen availability, and benthic community composition. In order to effectively document and compare bioturbation data from bedding planes, precise quantitative methods are needed. Here we present the intersection grid method, a quantitative presence/absence-based technique for accurately and efficiently estimating the percentage bioturbation on bedding-plane surfaces. The intersection grid method, which is based on an established method for estimating vegetative cover, is entirely digital and allows grids to be precisely scaled to match the bioturbation being analyzed. In addition, a record of each grid analysis can be saved as an image file for archiving and use in paleocommunity reconstruction. Testing the intersection grid method on hypothetical bedding-plane images demonstrates that accurate results—within 0.5% of the actual bioturbation percentage—can be obtained efficiently by scaling the grid within a recommended range. Intersection grid method data can be analyzed statistically and combined with descriptive ichnological and sedimentological data to reveal spatial, temporal, and paleoenvironmental patterns in bioturbation and make meaningful comparisons at outcrop, locality, and regional scales.

You do not currently have access to this article.