Complete chain-node topology is present. The data set was checked for polygon closure, erroneous or duplicate arcs, incorrect intersections, overshoots and undershoots, label errors, node errors, and appropriate fuzzy tolerances.
The data set represents the regional bedrock geology of the Pennsylvania portion of the Jamestown 30- by 60-minute quadrangle. The bedrock geology maps from which the contacts in this data set were derived show the rock units that crop out at the surface or that are present beneath the soil or beneath relatively thin surficial deposits. The contacts of the soils themselves, or of surficial deposits such as alluvium, colluvium, and glacial till and outwash, are not included in the source materials, nor are they included in this data set. Because the data set represents regional geology, some of the bedrock geologic units are
(1) generalized, (2) combined with other units, or (3) slightly exaggerated in areal extent so
that they may be represented at 1:250,000 scale (the scale of the 1980 map).
The data set does not include all of the information shown on the 1980 geologic map. For
example, the data set does not contain glacial boundaries, inset maps, marginal type, cross
sections, and the base information, such as roads, streams, and political boundaries, shown
on the 1980 map.
The lithologies in the polygon attribute table (items LITH1, LITH2, and LITH3) were
modified from the geologic descriptions of the units in the map explanation of the 1980
map, based on a review in 1998 by PaGS staff geologists. The scope of the 1980 map did
not include the mapping of lithologies, but rather the mapping of geologic formations
which, in most cases, consist of more than one lithology. The lithologic designations in the
explanation of the 1980 map are generalized and are not based on detailed field mapping or
statistical analyses. Moreover, the lithologies of many geologic units vary considerably
both laterally and vertically. Therefore, the dominant lithology (volumetrically) assigned to
a given unit in the data set may constitute only a minor part of that unit in local areas.
Additionally, the lithologies designated for each unit are generalized based on the areal
extent of the unit within the entire state. In cases where a geologic unit contains members
and other subunits that are present in only one region of the state, the lithologies for those
subunits and members are included in the data sets for all 30- by 60-minute quadrangles in
which the geologic unit occurs. Thus, some lithologies that are included in the data set for a
given 30- by 60-minute quadrangle may not occur within the areal extent of that