Qal
Alluvium
Quaternary
Medium to dark grayish brown, locally reddish brown, poorly sorted, unconsolidated cobbles, pebbles, sand, silt.  Locally thicker layers of moderately sorted, rounded cobbles or pebbles reflecting previous locations of stream channel.  Thickness is typic
1-1
Header1
None
255,255,179
no pattern
DS01
Alluvial sediment
High
DMUID01
Qt
Terrace Deposits
Reddish brown, clayey to sandy matrix containing rounded pebbles to cobbles of sandstone, vein quartz, and quartzite.  These deposits are locally present along current stream levels of Toms Creek and the Monacacy River, but at a higher level than the pre
1-2
255,242,102
Sedimentary material
DMUID02
Qc
Colluvium
Unsorted diamicton containing light gray to reddish gray, angular to subrounded boulders and cobbles of quartzite with a silty matrix.  Present as a thin veneer covering outcrops of the Weverton Formation on the sides of College Mountain and as wedge-sha
1-3
250,217,128
Colluvium and other widespread mass-movement sediment
DMUID03
Jd
Jurassic Dike(s)
Jurassic
Medium to dark gray, medium- to fine-grained, massive diabase.  Weathers to rusty, reddish or orangish brown, spheroidal boulders and cobbles.  Distributed as linear dikes that cut across stratification and massive sills that are subparallel to it.  Dike
2
255,77,0
Intrusive igneous rock
DMUID04
Trtm
Thermally Metamorphosed Rocks
Triassic
Medium to olive gray, hard, brittle and fractured hornfels and meta-arkose, adjacent to diabase intrusions. Includes dark-gray to olive-black hornfels in contact metamorphic zones that are a few feet wide adjacent to narrow dikes but may be hundreds of f
3
^tm
140,167,189
Contact-metamorphic rock
DMUID05
Trg
Gettysburg Formation
Cyclically interbedded reddish gray, laminated, very fine-grained sandstone, sandy siltstone and red to reddish brown shale to rooted mudstone.  Sandstone and siltstone intervals are commonly laminated to cross-laminated and siltstone intervals are mudcr
4
^g
175,217,217
Sandstone and mudstone
DMUID06
Trgh
Heidlersburg Member
Gettysburg Formation, Heidlersburg Member
Interbedded gray, calcareous siltstone and shale, laminated mudcracked and brecciated limestone, and dark grayish brown to reddish brown siltstone and shale.  Bedding is defined by cycles of gray siltstone and shale grading upward into gray laminated lim
4-1
Header2
^gh
27,183,222
Mostly mudstone
DMUID07
Trn
New Oxford Formation
The New Oxford Formation consists of interbedded, gray, pinkish gray, and reddish brown, fine- to coarse-grained sandstone, brownish red to reddish gray siltstone, red mudstone, shale, and calcareous claystone.  Sandstone or sandstone-dominated intervals
5
^n
171,247,243
DMUID08
Cfu
Frederick Formation
Cambrian
Medium to dark gray, thin- to medium-bedded, pyritic, argillaceous limestone and shaly limestone.  Contains intervals of tan-weathering dolomitic shale and sandy brecciated limestone.  In the Emmitsburg Quadrangle the Frederick Formation is highly sheare
6
_f
255,145,114
Limestone
DMUID10
Ch
Harpers Formation
Brownish gray to dark greenish gray, silty, phyllitic shale to highly sheared, phyllitic siltstone with intervals of brownish gray, medium-grained, silty sandstone.  Thickness is estimated at greater than 900 feet (275 m) in the Emmitsburg Quadrangle.
7
_h
247,196,222
DMUID11
Cwo
Owens Creek Member
Weverton Formation, Owens Creek Member
Medium to medium dark gray, medium- to thick-bedded, pebbly, ferruginous metagraywacke with thin layers of dark gray metasiltstone and shale. Some layers are poorly bedded and conglomeratic while others exhibit coarse-grained cross-beds.  This member is
8-1
_wo
212,120,120
Metasedimentary rock
DMUID12
Cwm
Maryland Heights Member
Weverton Formation, Maryland Heights Member
Interbedded, dark gray to dark greenish gray, intensely sheared, tuffaceous metasiltstone, metagraywacke, and quartzite. Near the top of the member a thick-bedded to massive, light gray quartzite approximately 30 feet (10 m) thick, represents the main ri
8-2
_wm
247,153,153
DMUID13
Cwb
Buzzard Knob Member
Weverton Formation, Buzzard Knob Member
Light- to medium-gray, thin- to medium-bedded, metaquartzite with thin partings and interbeds of thin, dark gray, fine-grained chloritic layers up to 1.5 inch thick.  Tabular and trough cross-bedding is prominent in the upper part of this member.  The Bu
8-3
_wb
255,222,209
Quartzite
DMUID14
CZl
Loudoun Formation
Cambrian-Late Proterozoic
Medium to dark gray, medium-bedded, phyllitic and quartoze conglomerate, and black, tuffaceous phyllite.   The Loudon Formation ranges in thickness from 30 to 200 feet.
9
_Zl
240,179,179
Lower-grade metamorphic rock of unspecified origin
DMUID15
Zcm
Catoctin Formation
Late Proterozoic
Massive to sheared and foliated, medium to dark greenish-gray, chloritic, epidote-rich metabasalt.  Some intervals consist of highly sheared chlorite tuffaceous phyllite, or amygdaloidal basalt.  Epidote is distributed as light green veins and amygdule f
10
222,204,179
Meta-mafic rock
DMUID16
Weverton Formation
Light gray to gray quartzite and light to medium gray metagraywacke with intervening intervals of dark greenish gray tuffaceous phyllite.  Three members are mapped within the Weverton Formation on Catoctin Mountain in Maryland. In ascending order these a
8
Header3
Regional metamorphic rock of unspecified origin
DMUID17
Trns
Sandstone beds
New Oxford Formation, sandstone beds
5-1
^ns
120,201,168
Sandstone
DMUID18