Central and Southern Appalachian Geomorphology - Tennessee, Virginia, and West Virginia: Maryville, Tennessee to Washington, D.C. July 2-9, 1989

124 Pages·9.89 MB·English

by  G. Michael Clark, Edward J. Ciolkosz, J. Steven Kite, David A. Lietzke(auth.)

Central and Southern Appalachian
Geomorphology-Tennessee,
Virginia, a~d West Virginia
Maryville, Tennessee to Washington, D.C.
July 2-9, 1989
Field Trip Guidebook T150
Leaders:
G. Michael Clark, Edward}. Ciolkosz,
}. Steven Kite, and David A. Lietzke
American Geophysical Union, Washington, D.C.
Copyright 1989 American Geophysical Union
2000 Florida Ave., N.W., Washington, D.C. 20009
ISBN: 0-87590-659-1
Printed in the United States of America
View from North ForkMountain horizontal control triangulation station (3553' =1083m), GrantCounty,
WestVirginia(Hopeville7.5'quadrangle) southwestintoPendletonCounty. Cameralocationisatcrestof
dipslopeonsoutheastlimbofWillsMountainAnticlinorium. Nearlytreelessareainlowestcenteristhescar
head area ofa debris slide that originated during a 17-18 June 1949 cloudburst that centered over this
mountain (Stringfield and Sn1ith, 1956; Clark, 1987a, c). In intennediate distance are the fold core, and
northwest limb (double, faulted, "saw-toothed" symmetrical ridges, underlain by Tuscarora Sandstone,
Silurianage)oftheWillsMountainAnticlinorium. Fromrightcenteredgetovanishingpoint (rightcenter
skyline)isAlleghenyFront,underlainatbasebythicksequenceofclasticsedimentaryrocksofDevonianage.
AboveDevonianstrataarerocksofMississippianage:thePoconoSandstoneunderliesaprominentbenchand
isoverlainbytheGreenbrierLimestone(snow-coveredhighpastures),and"intumissucceededbytheMauch
ChunkGroup;allthreerockunitsarejustbelow right skyline. CrestofAlleghenyFront(skylineatright)is
capped by orthoquartzite sandstones and conglomerates of the Pottsville Group ofPennsylvanian age,
supportingaforestcoverdominatedbyredspruce(Picea rubens). AlleghenyFrontisoneofseveralmajor
Central and Southern Appalachian structural fronts crossed by the T150 excursion that have powerful
geomorphicexpression. BothWillsMountainAnticlinoriumandAlleghenyFrontwereproducedduringthe
Alleghanian Orogeny (FIGURE 3) by at-depth tectonic upramping of the Waynesboro Sheet onto the
Martinsburg Sheet along decollements that, in the Central Appalachians, are predominantly blind thrust
systemscharacterizedbycoevalrockcoverdefonnation(DunneandFerrell,1988;McKoy, 1988).
Leaders:
G. Michael Clark
Department of Geological Sciences
The University of Tennessee
Knoxville, TN 37996-1410
Edward J. Ciolkosz
Department of Agronomy
The Pennsylvania State University
University Park, PA 16802
J. Steven Kite
Department of Geology and Geography
West Virginia University
Morgantown, WV 26506
David J. Lietzke.
Soil Scientist Consultant
Route 3 Box 607
Rutledge, TN 37861
IGC FIELD TRIP T150:
CENTRAL AND SOUTHERN APPALACHIAN GEOMORPHOLOGY -
TENNESSEE, VIRGINIA, AND WEST VIRGINIA
1 2 3 4
G. Michael Clark , Edward J. Ciolkosz , J. Steven Kite , and David A. Lietzke
INTRODUCTION and relief of the land during various stages
of the region's complex geomorphic history.
The geomorphology of the Central and South It is the authors' belief that major advances
ern Appalachians has been the subject of in understanding origin and evolution of
several prior excursions. Johnson et ale landforms and landscapes in the Appalachian
(1933) led a group from New York through New Highlands can come only with new knowledge of
Jersey, Pennsylvania, Maryland, and eastern both soil morphogenesis and the development
most West Virginia to the 16th International of form and relief on the underlying and bor
Geological Congress in Washington, DC. Butts dering bedrock surfaces through weathering
et ale (1933) discussed some aspects of Appa and erosion. This conviction dictates that
lachian geomorphology during their excursion the topics apropos to a geomorphic field ex
from Washington to Morristown, Tennessee and cursion setting be balanced between bedrock
return. More recently, Ciolkosz et al. and soil observations and discussions, as
(1971) led a geomorphology and soils trip these earth materials underlie and uphold the
from Pittsburgh, Pennsylvania to Washington. form and relief of the land, and interact
Kite and Linton (1987) £t at., organized with the ongoing surficial processes.
field excursions for the first meeting of the The foci of T150 include, but are not lim
Southeastern Friends of the Pleistocene in ited to, the following topics: the origin and
eastern West Virginia. Boguckiet ale (1973) evolution of topography and drainage in a
led a trip through Great Smoky Mountains Na Late Paleozoic fold-belt mountain range;
tional Park; part of this route will be re humid-temperate region process geomorphic re
traversed on day one of this excursion. search; recognition and study of dynamic and
Delcourt and Delcourt (1985) also conducted a relict landforms and their underlying materi
trip from Knoxville through the Great Smoky als; and applied geomorphic research studies
Mountains and in addition visited the ter that stress topics of prime concern to the
races of the Little Tennessee River. Since conservation and sensible development of the
the 16th IGC, the focus of Appalachian geo region's resources.
morphic research has shifted from speculation
on overall drainage evolution and description Route Logistics
and correlation of presumed erosion surfaces
IGC field trip T150 was designed to illus
to quantitative description, process-oriented
trate as many regionally-important facets of
studies based on equilibrium concepts, and
Central and Southern Appalachian geomorphol
applied research. Interest remains high,
ogy as can be accommodated with practical lo
however, in research that would help explain
gistical, temporal, and resource restraints
the origins of topography and drainage in
(FIGURE 1). For example, three great struc
this classic region. From the early works of
tural fronts (Blue Ridge, Allegheny, and
McGee (1888a, 1888b) and Davis (1888, 1889)
Little North Mountain) that have profound
to the present, the Appalachians have been
geomorphic expression will be transected dur
regarded as a prime area for the study of the
ing the excursion. Mileage favors the Ridge
effects of lithology and structure on form
and Valley province that inspired early semi
nal ideas on regional landscape origin and
1Department of Geological Sciences, The evolution in old fold-belt mountain ranges
University of Tennessee, Knoxville and still does so today. This routing also
commemorates the most extensive Appalachian
2Department of Agronomy, The Pennsylvania
excursion of the XVI International Geological
State University, University Park
Congress that dealt in part with geomorphic
3Department of Geology and Geography, West form and drainage (Butts et at., 1933), and
Virginia University, Morgantown
depicts the progress of geomorphic thought
4Lietzke Soil Services, Route 3, Box 607, for more than half a century. Overall geo
Rutledge, Tennessee graphic balance is maintained by selected
T150: 1
o------r-1-00------..---2-0,0mi
1...i.M.i
A Airport (McGhee - Tyson)
(I'
\!..) AppaIachian Plateau K Knoxville
® RIdge and Valley 8 Blacksburg
@ Blue Ridge M Monterey
@ Piedmont 6\VF Blackwater Falls
~
\Visconsinan Drift S Si<yland
[.:0S0:.:00]:: Pre - Wisconslnun Drift W Wash!nq;on D.C.
FIGURE 1 Major geomorphic units crossed by T150; see TABLE 1 for hierarchy.
Overnight stops are indicated on map and identified in legend.
routing and stops in the Blue Ridge, Appa (FIGURE 1), the first day's road log extends
lachian Plateaus, and Piedmont provinces from the Valley of East Tennessee into the
where trip themes are exemplified. southern section of the Blue Ridge province
From McGhee-Tyson International Airport and the Great Smoky Mountains National Park.
T150: 2
TABLE 1Geomorphic Units CrossedbyT150
Hierarchy (afterThornbury, 1965) Notations
AppalachianHighlands majordivision
Piedmontprovince
Foothill Zone section seeHack(1982)
NortheasternHighlands section seeHack(1982)
PiedmontLowlands section seeHack (1982)
BlueRidgeprovince
Northern BlueRidge section northofRoanokeRiver
SouthernBlueRidge section southofRoanokeRiver
Ridge andValleyprovince
Middle section= "RidgeandValley" DelawareRivertoca. NewRiver
"Ridge andValley"informaldistrict
"ShenandoahValley"informaldistrict
"MassanuttenMountain"informaldistrict
Southern section="Valley andRidge" southofca. NewRiver
"Valley andRidge ofVirginia"informaldistrict
"GreatValleyofVirginia"informaldistrict
"ValleyofEastTennessee"informaldistrict
"BaysMountain"informal subdistrict
AppalachianPlateausprovince
unglaciatedAlleghenyPlateausection "maturelydissected"middleportion
ofprovince
As an International Biosphere and Geosphere research sites will illustrate major geo
reserve, the park is a showcase of plant and morphic problems in this portion of the Ridge
animal communities, soils, hillslope, flu and Valley province.
vial, periglacial, and structural geomorph On the fourth day, effects of record
ology. As might be expected, the park flooding, and hillslope, fluvial, and struc
receives more visitors annually than any tural geomorphology will be emphasized as the
other national park in the United States. route enters West Virginia. In late after
Self-guided geological roadside tours and noon the excursion will ascend Allegheny
trail hikes in Great Smoky Mountains National Front and enter the Appalachian Plateaus
Park can be taken with the compendium pre province on the way to Blackwater Falls.
pared by Moore (1988) and the appropriate The fifth day's trip displays examples of
topographic and geologic maps. Departing the periglacial, soil, structural and karst geo
park in late afternoon, the route re-enters morphology. The route extends from Black
the Valley of East Tennessee at Pigeon Forge water Falls eastward across eastern West
and crosses half of the width of this dis Virginia and then southeastward into Virgin
trict en route to Knoxville. ia. Entering the Shenandoah Valley near
The second tour day entails a longitudi Harrisonburg, the trek crosses the valley and
nal transect of the southern section of the enters Shenandoah National Park in the north
Ridge and Valley province from Knoxville to ern section of the Blue Ridge province and
Mountain Lake, Virginia. Drainage, karst, concludes at Skyland. Shenandoah National
soils, and structural geomorphologic forms Park is also heavily frequented by tourists.
and materials will be examined quickly on The text, road log, and maps provided by
this trip leg. This is a travel day, with Gathright (1976) provide the opportunity for
few long discussion stops. self-directed geological tours of the park.
During the third day, soil, periglacial, The final tour day includes geomorphic
hillslope, fluvial, and karst geomorphology features along part of Skyline Drive, with
will be seen between the Mountain Lake area overlook stops, and fluvial geomorphology and
and Monterey, Virginia. Visits to specific speleology in a part of the Shenandoah Valley
T150: 3
just west of the park. After recrossing the The final afternoon's route illustrates
Blue Ridge, the last leg of the excursion landforms and landscapes typical of the Pied
crosses the Piedmont province to Washington, mont province in northern Virginia. Hack
DC. (1982) has produced a subdivision of the
Piedmont Province based on objective topo
Regional Geomorphology graphic, fluvial, and bedrock characteristics
-- an exercise that needs to be extended to
Early overall treatises on the Central and other areas of the Appalachians.
Southern Appalachians dealt largely with
physiographic description and the fluvial and Blue Ridge province. Stretching from
erosional surface history (cf. Hayes and Georgia northeastward to Pennsylvania, the
Campbell, 1894; Fenneman, 1928, 1938). Topo Blue Ridge province is a geomorphic region
graphic depictions that include the excursion that exhibits striking bedrock and topograph
region include the land-surface form map by ic differences between its Southern and
Hammond (1963) and the report by Redington Northern sections. Structural relations in
(1978). Other than to name several new sec the Southern Blue Ridge are highly complex.
tional subdivisions little work has been done Fensters in several areas demonstrate long
with regional geomorphology since Thornbury distance tectonic transport of thrust sheets
(1965). For the portion of the Appalachian which themselves contain highly-deformed
Highlands traversed by this excursion, the rocks of low to high metamorphic grades. The
nomenclature is shown in TABLE 1. Availabil Southern section widens southwestward from
ity of high-resolution remote-sensing image Roanoke, Virginia, attaining a maximum width
ry, and modern studies of structure, tecton of 113 km across the North Carolina-Tennessee
ic history, stratigraphy, soil science and border. Much of this section is bordered on
geomorphology, now make it possible to define the southeast by the high Blue Ridge escarp
and map regional geomorphology in the Appala ment, and on the northwest by a foothills
chian region. For example, Pike and Thelin belt that is itself backed in some areas by a
(1988) prepared a 1:2,500,000-scale shaded much higher range, the "Unaka Mountains" of
relief map of the United States that shows some writers. Between these eminences are a
major Appalachian landscapes clearly, and series of irregular ladderlike transverse
calculated statistics of central tendency and ranges separated in 30me areas by irregularly
dispersion for elevation, slope angle, tex shaped basins (Hammond, 1963). Many of these
ture, and slope azimuth for each major physi intermediate ranges are quite high in eleva
ographic land unit. Quantification of land tion; the various Balsams, and, of course,
form and landscape parameters is a necessary the Blacks with Mt. Mitchell are examples.
prelude to objective reassessment of the The highest elevations in the United States
classical geomorphic subdivisions (Fenneman, east of the Mississippi River are attained in
1928, 1938; Thornbury, 1965) that are still the Southern Blue Ridge (2038m).
used in the United States. Numerically Structure and lithology in the Northern
based physiographic maps of geomorphic re section are less complex; much of this area
gions would find usages in many areas of both is underlain by a pervasively-faulted anti
pure and applied geomorphology. As of excur clinorium strongly asymmetrical to overturned
sion time, however, large-scale such work has to the northwest. The Northern Blue Ridge
not been done in the Appalachian Region as a core area is underlain by igneous and meta
whole, and so the classical and some other morphic rocks of Precambrian age. To the
subjective "provisional" subdivisions are northwest, these rocks are unconformably
used herein. overlain by metasedimentary siliciclastic
rocks of Cambrian age (Gathright, 1976). The
Piedmont province. Extending from Alabama first day's tour illustrates bedrock and geo
to New Jersey, the Piedmont province is most morphic relations in Great Smoky Mountains
ly underlain by multideformed igneous and National Park in the Southern Blue Ridge sec
metamorphic rocks. Rift basins filled by tion in Tennessee and western North Carolina.
Mesozoic sedimentary rocks and intruded by Near the end of the excursion, road traverses
Mesozoic plutons occupy limited areas. Bed in Shenandoah National Park, Virginia, show
rock is mantled by saprolite (see Cleaves, rock and landscape features typical of the
1988) ranging from 0 to 100 m in thickness Northern section.
except in areas where fluvial erosion or
deposition predominate. Upland surface ele Ridge and Valley province. The Ridge and
vations rise from ca. 100 to 600 m from the Valley province extends northeast from north
Coastal Plain to the Blue Ridge, with isola central Alabama 1930 kID to the St. Lawrence
ted hills (or "monadnocks") common on the lowland. As wide as 100 krn in parts of
Piedmont near the Blue Ridge province. Pennsylvania, and as narrow as 23 km near the
T150: 4
Main Drainage Divides
Secondary Drainage Divides
(Where Shown)
"""-"
------- State Lines
50 100KM
FIGURE 2 Major rivers and drainage basins crossed in the T150 excursion re
gion; many tributary streams not shown, especially away from trip route. K =
Knoxville, B = Blacksburg, M= Monterey, BWF = Blackwater Falls, S = Skyland.
Major drainage basins (in circles) are: NA =North Atlantic, OH =Ohio, SA =
South Atlantic, TN =Tennessee. Secondary drainage basins (Potomac, Shenan
doah, James) identified only in NA basin.
New York-New Jersey line, the province is ea. maker. As this rock unit increases in thick
50-100 km wide in the T150 region. This re ness and relative resistance northeastwards,
gion is typified by northeast-southwest ridges underlain by it rise in elevation and
trending ridges and valleys in its northwest occupy progressively greater portions of the
ern portion, and a 3-80 km wide valley (the Southern section's area. Southern section
"Appalachian Great Valley") to the southeast. valleys mainly are underlain by shales, silt
Thornbury (1965, p. 113) placed the boundary stones, and carbonate rocks low in silici
between the Middle section and the Southern clastic mineral content. Overall master
section "near" New River. Fenneman (1938), drainage in the Southern section is longitu
however, placed it at the New River-Tennessee dinal (FIGURE 2). The Coosa River and
River divide. associated "Coosa Strath" in Alabama and the
In the Southern section of the province, Tennessee River in Tennessee and its head
valleys are wider than the low ridges. Ero water longitudinal tributaries in south
sional levels reach sedimentary rocks of western Virginia are classic examples of such
Cambrian age, and expose numerous thrust drainage. Lower-order tributaries often ex
faults and their associated tectonic struc hibit trellis drainage. Transverse drainage
tures. Sharp, angular-crested "sawtooth" is strikingly developed in tributaries of the
ridges are underlain by sandstones, silt Tennessee River that exit from the Blue
stones, and shales of the Rome Formation that Ridge province. The Little Tennessee, the
were tectonically ramped upward above thrusts, Little River, the Little Pigeon River, the
Rounded ridge crests, ofted double-crested, Pigeon River, the French Broad River, and the
are underlain by chert-rich formations (pre Nolichucky River typify such drainage that is
dominantly carbonate rocks) of the Knox transverse to structural and lithologic
Group. Variety is added to Valley and Ridge trends.
topography of northeastern Tennessee by the The Middle section is characterized by
Bays Mountain informal subdistrict where a longitudinal fold-belt mountain ridges that
complexly-downfolded synclinorium preserves progressively occupy greater areal portions
shales, siltstones and sandstones along a of the western part of the province north
linear belt of ridges with sharp relief. In eastwards. Erosional levels are stratigraph
northeast Tennessee, extending to New River ically higher in the western "Ridge and
drainage, the Clinch Formation of Lower Valley" informal district, and rocks of
Silurian age becomes the predominant ridge Ordovician age are commonly the oldest rocks
T150: 5
exposed. Major surface thrust faults are gheny Plateau section reaches 1482 m on
less common to the northeast, and subsurface Spruce Knob. In this part of West Virginia,
or blind thrust systems with coeval cover the Allegheny Front is both the topographic
deformation become the dominant tectonic and structural boundary between the Plateau
style (Dunne and Ferrell, 1988). North of to the west and the Ridge and Valley to the
New River, the Tuscarora Sandstone (Clinch east. The Front is underlain primarily by
Formation equivalent) becomes the prime ridge clastic sedimentary rocks of Devonian and
maker. From east-central West Virginia Mississippian age that are capped by Pennsyl
northeastward, the underlying clastic Oswego vanian-age sandstones and conglomerates of
and Juniata Formations of Upper Ordovician the Pottsville Group at the crest. These
age become important secondary ridge-forming rocks have been raised and laterally trans
rock units. Additional ridge-forming rock ported northwestward above the subsurface
units include the resistant Silurian sand tectonic discontinuity produced by the
stones (including "Cacapon") within the Rose Waynesboro Sheet upramping to the Martinsburg
Hill Formation, Clifton Forge, Eagle Rock Sheet (McKoy, 1988).
Williamsport, "Keefer", and Devonian Ridge West of Allegheny Front, the Allegheny
ley (Oriskany) Sandstone. In eastern West Plateau is underlain by Mississippian- and
Virginia, and extending into Pennsylvania, Pennsylvanian-age sedimentary rocks that have
large synclinoria bring down extensive been folded into broad anticlines and syn
sequences of Middle Devonian shales into clines. In this part of West Virginia, these
broad valleys; the Bedford Synclinorium is an folds have been breached by erosion so that
example that will be crossed during day five. large anticlinal valleys and synclinal up
The narrower valleys more typical of the lands dominate the topography.
western part of the Middle section are under Major drainage lines follow fold and
lain by shales, siltstones, and carbonate lithologic trends, and perhaps fracture zones
rock units. in transverse gorges. Deep gorges with
Master drainage in the western Ridge and rapids and waterfalls are common in this part
Valley is classic trellis, with longitudinal of the Plateau. Headwater reaches often ex
tributary streams in strike valleys, and hibit dendritic patterns and in their well
transverse drainage often in spectacular spring areas are often poorly drained. In
water gaps - as linkages. North Fork Gap and the part of the Plateau visited by T150,
Brocks Gap are excellent examples that will drainage is tributary to the Cheat River sys
be traversed during day five. "Wind" gaps tem that flows via the Monongahela River
are another characteristic feature of this north to the Ohio River at Pittsburgh,
area. Dolls Gap, a spectacular example Pennsylvania.
quoted by Davis (1889, p. 245), is just north
of the excursion transect (see Antioch U.S. Climate and Vegetation
Geological Survey 7.5-minute quadrangle).
The Shenandoah Valley in northern Virginia Present climates in the excursion region
and easternmost West Virginia is underlain by vary greatly because of differences in eleva
a thick sequence of carbonate rock units of tion, exposure, latitude, distance from water
Cambro-Ordovician age that is tightly folded bodies, and other factors. Mean annual air
and pervasively faulted and otherwise frac temperatures range from ca. 6.6 to 14.5° C.
tured in many areas. The Massanutten Syn The time period between the last spring frost
clinorium contains downfolded clastic rocks and the first fall frost, or "growing season"
of Ordovician, Silurian, and Devonian age. ranges from ca. 200 days in the valleys of
Here, the ridge crests are capped by the East Tennessee to much less than 150 days at
Massanutten Sandstone, partially equivalent the highest elevations and in cold air drain
to the Tuscarora Sandstone farther west age sites. Mean annual precipitation varies
(Rader, 1982). widely. Rain shadow areas in the Ridge and
Overall Shenandoah Valley drainage is Valley of eastern West Virginia and the
trellis with transverse linkage streams (see Shenandoah Valley of Virginia may receive
Hack, 1957, 1973). In detail, there are many less than 90 cm annually. Windward high ele
complexities related to underlying structure, vation sites in the Great Smoky Mountains
rock types, and climatic history. along the Tennessee-North Carolina border may
average 200 cm. There are also large varia
Appalachian Plateaus province. The Appa tions in other factors of interest to geo
lachian Plateaus province extends from the morphologists and soil scientists. These
Coastal Plain in northwestern Alabama to include: rainfall intensity, extent and mag
northwestern New York. On T150, it will be nitude of severe storms that cause landslides
visited only in eastern West Virginia, where and floods, humidity, cloud cover, length and
the highest portion of the unglaciated Alle- severity of droughts and wet periods, and
T150: 6