Geologic units in San Juan county, New Mexico

Nacimiento Formation (Paleocene) at surface, covers 23 % of this area

San Juan Basin

Kirtland and Fruitland Formations (Campanian) at surface, covers 16 % of this area

Coal-bearing, primarily in the Fruitland.

Menefee Formation (Campanian to Santonian) at surface, covers 12 % of this area

Mudstone, shale, and sandstone; coal-bearing.

San Jose Formation (Eocene) at surface, covers 8 % of this area

San Juan Basin

Mancos Shale, upper part (Campanian to Coniacian) at surface, covers 7 % of this area

Mancos Shale, upper part

Mancos Shale (Cenomanian to Campanian) at surface, covers 4 % of this area

Divided into Upper and Lower parts by Gallup Sandstone.

Alluvium (Holocene to upper Pleistocene) at surface, covers 4 % of this area

Alluvium

Cliff House Sandstone (Campanian) at surface, covers 4 % of this area

Transgressive marine sandstone.

Mancos Shale, lower part (Turonian and Cenomanian) at surface, covers 3 % of this area

Mancos Shale, lower part

Chuska Sandstone (Middle to upper Oligocene) at surface, covers 3 % of this area

Restricted to Chuska Mountains.

Lewis Shale (Campanian) at surface, covers 3 % of this area

Marine shale and mudstone.

Morrison Formation (Upper Jurassic) at surface, covers 2 % of this area

Upper Jurassic nonmarine rocks.

Pictured Cliffs Sandstone (Campanian) at surface, covers 2 % of this area

Prominent cliff-forming marine sandstone.

Ojo Alamo Formation (Paleocene) at surface, covers 2 % of this area

San Juan Basin

Gallup Sandstone (Turonian) at surface, covers 2 % of this area

Generally regressive marine sandstone.

Landslide deposits and colluvium (Holocene to Pleistocene) at surface, covers 2 % of this area

Landslide deposits on western flanks of Socorro Mountains not shown for clarity.

Point Lookout Sandstone (Campanian to Santonian) at surface, covers 1 % of this area

Regressive marine sandstone in McKinley and Sandoval Counties; the lower, Hosta Tongue, of Point Lookout is transgressive and is separated from main body by the Satan Tongue of Mancos Shale.

Dakota Sandstone (Cenomanian) at surface, covers 0.9 % of this area

Includes Oak Canyon, Cubero, and Paguate Tongues; includes Clay Mesa Tongue of Mancos Shale.

San Rafael Group (Middle Jurassic) at surface, covers 0.5 % of this area

Consists of Entrada Sandstone, Todilto and Summerville Formations, Bluff Sandstone, and locally Zuni Sandstone (or only Acoma Tongue of Zuni).

Mesaverde Group (Campanian to Turonian) at surface, covers 0.4 % of this area

Includes Cliff House Sandstone, Menefee Formation, and Point Lookout Sandstone.

Rock Point Formation of Chinle Group (Upper Triassic) at surface, covers 0.4 % of this area

May locally include Wingate Sandstone.

Animas Formation (Paleocene and upper Cretaceous) at surface, covers 0.3 % of this area

Volcaniclastic sedimentary rocks of intermediate composition in northern San Juan Basin.

Upper middle Tertiary basaltic andesites and andesites of the Mogollon Group (Lower Miocene and uppermost Oligocene (22-26 Ma)) at surface, covers 0.2 % of this area

Includes Bearwallow Mountain Andesite and basaltic andesite of Mangas Mountain; also near vent basaltic lavas and shallow intrusions in the Chuska Mountains.

Triassic rocks, undivided (Triassic) at surface, covers 0.1 % of this area

Continental red beds.

Upper Cretaceous rocks of southwestern New Mexico, undivided (Maastrichtian to Cenomanian) at surface, covers < 0.1 % of this area

Beartooth and Sarten Formations are in part Albian. Includes Virden Formation in northern Hidalgo County, Ringbone Formation in Hidalgo, Luna and Grant Counties, Mancos Shale in Silver City area.

Tertiary mafic intrusive rocks (Pliocene to upper Eocene) at surface, covers < 0.1 % of this area

Includes many long basaltic andesite dikes of Oligocene age near Pie Town, Acoma, Riley, Chupadera, Truth or Consequences, Roswell, Raton, and Dulce; and several elongate or shoestring-like sills of basalt or basaltic andesite. Also includes basaltic necks of Pliocene age that dot the landscape northeast of Mount Taylor. Where dikes extend into Quaternary alluvium the contact is an unconformity.

Chinle Group (Upper to middle Triassic) at surface, covers < 0.1 % of this area

Map unit includes Moenkopi Formation (Middle Triassic) at base in many areas; in eastern part of state the following five formations are mapped: TRr, TRb, TRt, TRg, and TRs.

Upper and Middle Jurassic rocks, undivided (Upper and Middle Jurassic) at surface, covers < 0.1 % of this area

In southwest includes the basalt-bearing Broken Jug Formation.

Tertiary intrusive rocks of intermediate to silicic composition (Pliocene to Eocene) at surface, covers < 0.1 % of this area

Includes monzonitic to granitic plutons, stocks, laccoliths, and porphyritic dikes in deeply eroded magmatic centers; and andesitic, dacitic, or rhyolitic plugs and dikes near cauldrons or stratovolcanoes. In the Latir field, fine-grained rhyolitic dikes commonly cut coarse-grained granitic plutons. Includes alkaline laccoliths, plugs, and dikes in Colfax County. North-trending dikes near Capitan include some mafic diabase dikes.