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Mineral Resources > Online Spatial Data > Geology > by state > Texas Geology

Geologic units in Llano county, Texas

alluvium (Phanerozoic | Cenozoic | Quaternary | Holocene) at surface, covers 0.7 % of this area

alluvium

Lithology: sand; silt; clay or mud; gravel

Wilberns Formation showing San Saba Member (Phanerozoic | Paleozoic | Cambrian-Furongian) at surface, covers 3 % of this area

Wilberns Formation showing San Saba Member

Lithology: dolostone (dolomite); limestone; sandstone

Packsaddle Schist (preCambrian-Proterozoic [Llano]) at surface, covers 21 % of this area

Packsaddle Schist

Lithology: amphibole schist; quartz-feldspar schist; mica schist; schist; amphibolite; quartzite; marble; granulite; gneiss

Town Mountain Granite (preCambrian-Proterozoic) at surface, covers 23 % of this area

Town Mountain Granite

Lithology: granite; porphyry

Big Branch Gneiss (preCambrian-Proterozoic) at surface, covers < 0.1 % of this area

Big Branch Gneiss

Lithology: gneiss; schist

Honeycut Formation (Phanerozoic | Paleozoic | Ordovician-Early) at surface, covers 0.5 % of this area

Honeycut Formation

Lithology: dolostone (dolomite); limestone

Valley Spring Gneiss (preCambrian-Proterozoic) at surface, covers 25 % of this area

Valley Spring Gneiss

Lithology: paragneiss; mica schist; amphibole schist

Red Mountain Gneiss (preCambrian-Proterozoic) at surface, covers 0.3 % of this area

Red Mountain Gneiss

Lithology: gneiss; granite; granite

Younger granitic intrusion (preCambrian-Proterozoic) at surface, covers 8 % of this area

Younger granitic intrusion

Lithology: granite; aplite; pegmatite

Riley Formation showing Lion Mountain Sandstone and Cap Mountain Limestone Members, undivided (Phanerozoic | Paleozoic | Cambrian-Middle) at surface, covers 2 % of this area

Riley Formation showing Lion Mountain Sandstone and Cap Mountain Limestone Members, undivided

Lithology: limestone; sandstone; shale; siltstone

Marble Falls Limestone (Phanerozoic | Paleozoic | Carboniferous Pennsylvanian [Morrow]) at surface, covers 0.2 % of this area

Marble Falls Limestone

Lithology: limestone; shale

Terrace deposits (Phanerozoic | Cenozoic | Quaternary | Pleistocene Holocene) at surface, covers < 0.1 % of this area

Terrace deposits

Lithology: terrace; sand; gravel; silt; clay or mud

Wilberns Formation showing Point Peak, Morgan Creek Limestone, and Welge Sandstone Members, undivided (Phanerozoic | Paleozoic | Cambrian-Furongian) at surface, covers 3 % of this area

Wilberns Formation showing Point Peak, Morgan Creek Limestone, and Welge Sandstone Members, undivided

Lithology: limestone; medium-grained mixed clastic; conglomerate; siltstone

Lost Creek Gneiss (preCambrian-Proterozoic) at surface, covers < 0.1 % of this area

Lost Creek Gneiss

Lithology: paragneiss; schist; metasedimentary rock

Mafic igneous rocks (preCambrian-Proterozoic) at surface, covers 0.1 % of this area

Mafic igneous rocks

Lithology: diorite; hornblendite; metagabbro

Gorman Formation (Phanerozoic | Paleozoic| Ordovician-Early) at surface, covers 0.8 % of this area

Gorman Formation

Lithology: limestone; dolostone (dolomite)

Tanyard Formation (Phanerozoic | Paleozoic | Ordovician-Early) at surface, covers 2 % of this area

Tanyard Formation

Lithology: limestone; dolostone (dolomite)

Hickory Sandstone Member (Phanerozoic | Paleozoic | Cambrian-Middle) at surface, covers 7 % of this area

Hickory Sandstone Member

Lithology: sandstone; sandstone; conglomerate

Quaternary deposit, undivided (Phanerozoic | Cenozoic | Quaternary) at surface, covers 0.2 % of this area

sand, silt, clay, and gravel. locally indurated with calcium carbonate (caliche); includes point bar, natural levee, stream channel, sand dune, terrace, alluvial fan, landslide bolson and playa deposits

Lithology: sand ; silt ; clay or mud; gravel; carbonate

Smithwick Formation (Phanerozoic | Paleozoic | Carboniferous Pennsylvanian-Middle [Atoka]) at surface, covers < 0.1 % of this area

Smithwick Formation

Lithology: fine-grained mixed clastic; limestone; shale; sandstone; conglomerate