http://pubs.usgs.gov/of/2007/1010/lm100k_readme.txt

Description of digital data files posted on this website:

lm100k_readme.txt - this file

lm100k_metadata.txt - FGDC compliant metadata. Each Geodatabase Feature Class also has its own metadata embedded in the geodatabase.

lm100k_geodatabase.zip - Geodatabase package.  Includes:
-- lm100kgdb_readme.txt
-- LakeMead100k_OFR2007-1010.mdb - ArcGis Personal Geodatabase
-- LakeMead100k_OFR2007-1010.style - ArcMap style
-- LakeMead100k_OFR2007-1010.lyr - ArcMap layer file of symbolized feature classes
-- f36114a1.tif - 1:100,000-scale DRG base

lm100k_shapefiles.zip - Shapefile package.  Includes:
-- lm100kshape_readme.txt
-- lm100k_shapefiles - shapefiles of feature classes in the geodatabase (does not include annotation layers)
-- lmlmu100k.dbf - list of 1:100,000-scale geologic map units
-- LakeMead100k_OFR2007-1010.style - ArcMap style
-- f36114a1.tif - 1:100,000-scale DRG base