Comparison of surficial geology maps based on soil survey and in depth geological survey

Miller, B.A. and C.L. Burras. 2015. Comparison of surficial geology maps based on soil survey and in depth geological survey. Soil Horizons 56(1). doi:10.2136/sh14-05-0005.


Previous studies have suggested researchers should use Soil Survey maps to create surficial geology maps where more spatial detail about surficial geology is needed than is available from maps already produced by geologists. Despite the widespread availability of relatively detailed soil maps in the USA, few areas have a surficial geology map published at similar map scales. This apparent gap between disciplines calls to question the accuracy of soil maps to represent the spatial distribution of surficial geologic materials. Therefore, the purpose of this research is to test the agreement between maps from these two sources. To accomplish this, published surficial geology maps are compared to those derived from Soil Survey maps in an area where geologists have a close relationship with soil scientists, but the coverage of detailed surficial geology maps is limited. This study compares seventeen 1:100,000 and ten 1:24,000 surficial geology maps recently produced by the Iowa Geologic Survey with Soil Survey maps that have been categorized to represent the surficial geology of the same areas. Depending on the state of understanding the geologic history for an area when the map was produced and the acceptance of differences due to cartographic scale, most of the maps were in agreement at 67-99% of the examined sites. Lower agreement percentages were in areas with more complicated geologic histories, such as areas described as loamy sediments or where a thin loess cover could be obscured by bioturbation.

*A map from this article provided the cover image for this edition of Soil Horizons.

Leave a Reply