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1948 Piedmont Interstream Surfaces of the Colorado Springs Region. Benjamin Almon Tator Louisiana State University and Agricultural & Mechanical College

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Recommended Citation Tator, Benjamin Almon, "Piedmont Interstream Surfaces of the Colorado Springs Region." (1948). LSU Historical Dissertations and Theses. 7915. https://digitalcommons.lsu.edu/gradschool_disstheses/7915

This Dissertation is brought to you for free and open access by the Graduate School at LSU Digital Commons. It has been accepted for inclusion in LSU Historical Dissertations and Theses by an authorized administrator of LSU Digital Commons. For more information, please contact [email protected]. PIEDMONT 1NTBR3IR5IAM SURFACES Of THE COLORADO SPRINGS REGION

A Dissertation

Submitted to the Graduate Faculty of the Louisiana State University and Agricultural and Mechanical College in partial fulfillment of the requirements for the degree of Doctor ©f Philosophy in The School of Geology

by Benjamin Almon Tator M.S. Louisiana State University, 1941 May, 1948 UMI Number: DP69293

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INTRODUCTION ...... i Region Studied ...... 4 Geologic Setting ...... 4 Structural Setting ...... 4 F ield Work 5 Acknowledgments ...... 5 Previous Work 6 CONCEPTS OF ORIGIN OF BEDROCK EROSION SURFACES ...... 7 TOPOGRAPHIC UNITS OF THE COLORADO SPRINGS REGION .... 10 Southwest Area .••»•••••• 10 Manitou Embayment Area .* 10 Lower Piedmont Area 11 High Divide Area ...... 11 PIEDMONT IN TER STREAM FLATS .. 12 High Level Group...... * 12 Intermediate Group ...... 13 Low Level Group ...... 13 The Stream Terraces ...... 14 DEADMAN CANTON SURFACE OF THE HIGH LEVEL GROUP ...... 15 Location and Extent ...... 15 Surface Features ...... 15 E levation and Slope ...... 18 The Alluv 1 urn 19

T'ho TfinV Surface ...... 21 Other High Level Group Surfaces ...... 21 v ? %n (c Lci3 d c U 1 1

^•*5- D ; ; a z 3 Page L lfflB TURKEY CREEK SURFACES OF THE INTERMEDIATE GROUP 26 Location and Extant 26 Surface Features ...... *...... 26 Elevation and Slope ...... 26 The Alluvium ...... 29 The Bedrock Surface ...... 30

Other Intermediate Group Surfaces ...... 30 ROOK CREEK SURFACES OF THE LOW LEVEL GROUP...... 34 Location and Extent ...... «...... 34 Surface Features...... 36 Elevation and Slope ..»*, ...... 36 The Alluvium ...... * *. 37 The Bedrock Surface ...... 3? THE MESA SURFACE OF THE LOW LEVEL GROUP...... 39 Location and Extent ...... 39 Surface Features • • . * .. 39 Elevation and Slope ...... 41 The Alluvium ...... 41 The Bedrock Surface ...... 43 Other Low Level Surfaces...... *...... 44 THE STREAM TERRACES ...... 43 CLIMATIC CONSIDERATIONS ...... $0 VALLEY CHARACTERISTICS ...... 53 In the Mountain Canyons ...... 53 In the Piedmont ...... *. • • * 56

i l l Page MECHANICS 01 VALLEY WIDENING ...... 59 Climatic Pastors ...... 99 Retreat of Slopes ...... 59 Channel Shifting ...... 61 Bedroek Erosion ...... 64 RELATIONSHIP BETWEEN VALLEY DEEPENING AND VALLEY WIDENING ...... 68 DEVELOPMENT OP PIEDMONT PLATS AND TERRACES ...... 71 RELATIONSHIP BETWEEN THE DAKOTA RIDGE AND THE SURFACES ...... 75 E levation ...... 75 Trend ...... 76 Extent of Preservation ...... 77 EROSIONAL HISTORY OP THE DSADMAN CANYON AREA ...... 78 AGE CONSIDERATIONS ...... 87 CONCLUSIONS ...... 91 REFERENCES CITED ...... 95

iv LIST OF FIGURES Fag© Figure 1# Index of Region Studied ...... x l Figure 2. View last along Broad Valley Flat Hor tli of Rook Creek ...... 3 Figure 3 . Stratigraphy of the Colorado Springe Region in Tabular Form ...... 4a Figure 4* Contour Map of the northern Fortion of the Deadmn Canyon Surface ...... 16 Figure 5 . View Northeast on the Southern Portion of the Deadman Canyon Surface ...... 17 Figure 6 , Alluvial Section in the Northeast edge of the Deadiaan Canyon Surface showing old Channel in the Surface ...... 19 Figure 7 * Alluvial Section in the High Level Croup Surface on the South Slop© of the Rampart Range ...... 24 Figure 8. Contour Map of the L ittle Turkey Creek Surfaces of the Intermediate Croup .... 27 Figure 9- View South on the lowest of the Inter* mediate Croup le v e ls Just N ortheast of Turkey Creek 31 Figure 10. View Mountainward on the stripped pied­ mont f l a t on the Red Greek-Turkey Creek d ivid e ...... 33 Figure 11. Contour Map of the Rock Creek Surfaces of the Low Level Croup ...... 35 Figure 12. Scour Channels In the Highway 115 road- cut through the Red Creek Surfaces •.•• 36 Figure 13. Contour Map of The Mesa Surface of the Low Level Croup ...... • 40 Figure 14. Alluvial Section in the Colorado Springs C ity Gravel Pit • • • ...... 42 Figure 15. View South across a steeply-sloping piedmont f l a t flank in g the Rampart Range in Northern portion of the Colorado Springs Region ...... 46

v. Page Figure 16* View Northeast toward little fountain Creek Canyon upsiope along the h igh est stream terraoe of that Valley • • * * * 49 Figure 17* View of Modern Channel Impingement against the Basin Wall in the Canyon Basin of Upper Bed Creek ...... 55 Figure 18, View Northward in the basin of Upper led Creek ...... 55 Figure 19. Map showing the canyon basin of Upper Bed Creek ...... 58a Figure 20. Map showing Valley Characteristics in the upper piedmont portion of the Valley of Rook Creek ...... 58b Figure 21. Map Of Deadman Canyon Area showing the Various Piedmont Surfaces ...... 86a

v i. LIST OF PLATES (Appendix)

P la te I .... Map of the Colorado Springs Begioa showing the location and extent or the various piedmont Interstream surfaces« P la te II Orosa~aeetioos along Highway 115 readouts through the middle and lowest levels of the Hook Creek Surfaces of the how Level Croup, and the middle level of the Intermediate Croup west o f Bed Creek. P la te I I I Surface profile® of the Dea&man Canyon Surface levels, the Little Turkey Greek Surfaces, and the Bock Creek Surfaces; and adjacent streams including Little Turkey, Turkey, Little Bear, Little fountain, and Bock Creeks. ABSTRACT

Three major groups of broad piedmont levels: the High Levels, the Low Levels, and the Stream Terraces, flank the Front Range in the Colorado Springs region* The High and Low Level groups are late Pleistocene in age and the Stream Terraces are Recent. A fourth Croup, the Intermediate, is the age equivalent of the Low Level Croup, but occurs in upper piedmont areas held at higher elevations because of the confining effect of the re­ sistant Dakota unit* These piedmont interstream flats stand above the modern v a lle y bottoms and slope outward from the range. They consist of relatively thin alluvium blanketing roughly planate bedrock surfaces. The alluvium is a coarse fangiomarate made up of poorly stratified and poorly sorted torrential deposits. The bedrock surfaces truncate the homoclinal structure of the piedmont. The development of the piedmont levels is related to processes active at present in the modern valley bottoms. The Front Range is being uplifted continuously and not intermitt­ ently. The piedmont surfaces occur in multiple arrangement with minor vertical intervals separating the several member levels of each group, and major vertical intervals separating the High Level Group from the Intermediate and Low Level groups. The levels of each group merge in the upslope direction toward the range. The groups tend toward convergence in the same sens®, but to a le s s marked degree. Lach le v e l i s a v a lle y bottom rem­ nant representing an episode of widening in th® stream valleys

v l i i of the region, intervals between them being hue to incision of the valley flat during episodes of valley deepening, Talley widening is oaused by sidewall retreat under the influence of a semiarld climatic regime similar to the present. The constancy of d im tic conditions over long periods yields a uniform rat© of weathering and erosion* TJnder the present semiarid climate the runoff is cap­ able of removing the material being supplied by weathering and erosion* This uniformity of climatic conditions is also expressed in an average depth of scour in the valley bottoms during torren­ tial runoff* The planate character of the bedrock surface under these levels is the result of the shift in locus of flood scour by alluvial damming of the flood channels, the average flood being capable of corroding the bedrock surface* Valley deepening occurs during episodes of increased annual rainfall over long periods. This increase yields a more uniform distribution of runoff throughout the year and continuous flow along one channel of the valley bottom* Dowacutti&g confined to one channel results* The small intervals between levels of the same group are caused by minor climatic fluctuations. The larger vertical intervals between the groups result from major climatic changes such as were brought about by change from the more arid interglaoial epochs to the more humid glacial epochs* Th© presence of three major surface groups is quite in line with evidence of two glaciations in the Rocky mountain region in Pleistocene time* The eastern face of the Front Range is an expression of differential erosion on contrasting rock types, with the resistant granitic rocks of the mountain mass standing high above the weaker

ix* sedim ents o f the piedmont# The mountains are pro sent because they are being slowly and continuously uparched. -Tim mountain front is not a result of faulting, though locally faults control the site of differential erosion#

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That portion of the Colorado Piedmont adjacent to the Front Ranges in Colorado is characterized by broad interstream flats which stand above the modern valley bottoms and slope out-* ward from the range toward the major drainage lines of the Pied* mont (Figure 2). These are one of the striking physiographic features of Rocky Mountain front topography, occurring in sharp contrast to the precipitous mountain escarpment and the aligned hogbacks of the foothills belt. These surfaces are fan-like al­ luvial terraces floored with coarse fanglomerate deposits of varying thickness. On many, relict stream channels are preserv­ ed which converge upslope toward some major canyon in the moun­ tain front. In some localities the interstream flats abut against the mountain front. In other localities they lie de­ tached from the mountains as a result of erosion. Many of the principal fan-like surfaces display a multiple of levels which occur in steplike fashion and merge upslope. Lower levels in many places engulf butte-like remnants of higher levels. The fanglomerate overlies bedrock surfaces which are eros­ ion planes truncating the homoolinal strata of the foothills belt, in some localities extending westward into the granitic rocks of the mountain mass. In most areas the bedrock surface shows little regard for variations in the rock type. The chief irre­ gularities in these rock surfaces are broad, shallow depressions

1 a or snailf channel-ilka incisions below the average bedrock le v e l. Two types of stream valleys occur in the region, those which originate within the mountain mass and flow through the piedmont to join the master drainage to the east, and those which ere confined to the piedmont* the latter are actively

i dissecting the marginal edges of the piedmont flats. Some of these lead directly to the master drainage to the east. Many, however, are tributary to the larger mountain-born valleys* hone of these valleys contain continuously flowing streams throughout the year, being for the most part dry during the summer months* The majority of the valleys of the piedmont are broad, thinly-alluviated flats underlain by a relatively flat bedrock floor* Local narrowing and widening occur along the same val­ ley* These conditions can often be attributed to variations in resistance of the bedrock forming the Valley sides* Valley segments in the mountain area are deep and narrow, except lo­ cally where small, thinly-alluviated, flat-floored basins occur* Many of these piedmont valleys contain flights of thin- ly-alluvlated, rock-floored terraces along their walls* Where these occur they border the interstream piedmont flats, form­ ing "steps* in the scarped edges of the latter features* The origin of these various levels is a major key in solving the diastrophlc history of the Rocky Mountain front region. The present study attempts to determine the history of this development* It includes detailed descriptions of the 3 surfaces in a selected area of the piedmont, concepts of ori­ gin of similar landforms in other areas as suggested by pre­ vious writers, descriptions of the processes taking place on the modern valley flats to which the interstream surfaces ap­ pear to be related, and finally, an interpretation by the au­ thor of the history of a portion of the area of study with con­ clusions as to the origin of these surfaces.

Figure 2 s Broad valley flat sloping eastward from the moun­ tain base in the lower piedmont area north of Rock Greek. The higher piedmont flat in the left and mid­ dle distance is the intermediate level of the Low Level Group in the Rock Greek Surfaoes. RIAN CAMB­ PRE- s a N! O M o CO O O tS3 o M o u t CENOZOIC UKDOVIQIAN M ISSISS- ' ' ISSISS- M PENNSYL­ PERMIAN JURASSIC 3 CAMBRIAN O gg EH O “4 VANIAN IPPIAN TERTIARY - i - EOCENE — " T ^ j. J I 1 \ i i i i . r f cu S os 1-3 s 1 8 5 2 a; k E-* < o o r-3 CU H O E ■a; h

IE PEAK PIKES DAKOTA FOUNTAIN AAI aps n ri n t t n porton of he r on io g re e th f o n tio r o p rn e rth o n e th in s e g id r and s carp S LARAMIE lDSN )O n t aphi gni cance c n a ic if n ig s ic h p ra g o p to no Of IlADISON(?) 'UANITOU LYONS LYE INS SAVJATCH HARDING MORRISON PQ ; 2 GRAIHTE H E o J25 DAWSON h PSAABdok ne Lw ve ad g Le Gop s e c a f r u s Group l e ev L igh H and el ev L Low under Bedrock APISHATA c 77 i pas tim PIERRE ODELL X IL aps n ri n t hern porton of he r on io g re e th f o n tio r o p n r e th r o n e th in s e g id r and s carp S OX HILLS L FUSON DAKOTA GRANEROS GREENHORN CARLILE h KOTA s k c a b g o h osi anes e n la p n io s ro e " e th f o on i t r o j n r e th r o n e th in u»lart*ia g n i l l o r ish H G e n e ra lly tru n c a te d by e ro s io n p la n e s 'b u t l o c a l l y form s s form y l l a c o l t u 'b s e n la p n io s ro e by d te a c n tru lly ra e n e G osi anes e n la p n io s ro e s form y l l a c o l t u b s e n la p n io s ro e by d te a c n tru lly hogbacks ra e n e G ru suraces e c rfa u s Group Bedrock in broad v a lle y s and g e n e r a lly tr u n c a te d by by d te a c n u tr lly a r e n e g and s y lle a v broad by in d te a c n Bedrock u tr lly a r e n e g and s y s lle e a n v la p n broad io s ro in e Bedrock Broad v a lle y f l a t s and dom inant b edrock under Low L e v e l l e v e L Low under edrock b inant dom and s t a l f y lle a v Broad Bedrock in broad v a lle y s and g e n e r a lly tr u n c a te d by by d te a c n u tr lly a r e n e g and s y lle a v broad in Bedrock les monan ope rmnns erosi anes e n la p n io s o r e f o nants rem e p lo s ountain m s rlie e d n U gak, as, n s equent l s y lle a v t n e u q se b su and , s ta s e u c ogbacks, H e on, hr it underi id n surf ‘ . s e c fa r u s ont yiedm s rlie e d n u t i where , n io reg M ountain s lo p e s b o rd e rin g piedm ont on th e w est est w e th on ont piedm g rin e rd o b s e p lo s ountain M les pori Int medi e Gop s e c s a e f n r u la s p n Group io s o r te e ia d e ck ro rm ed te b n I f above o s ^ e n g id rtio r o p and s rlie e knobs d n l U a u sid e R io lithologic ee n i he ao: group Dakot:. e th in ent elem c i g o l o h t i l Minor o i t t n rta o p im Not obcs n cuesqs stq e u c and Hogbacks ot r um f he kt group akots D e th of m tu tra s t n a t s i s e r Most cr "flatiron1 f on o grani purs u sp e it n a r g on n io h s 1* fa n o r i t a l f " ccurs O les pori Int at ru surf s e c s e fa r n u la s p n Group io s ro te e ia d e ck m ro r te bed n I f above o s s e n g id rtio r o p and s rlie knob3 e d n l a U u sid e R f o opogr c i portance im ic h p ra g o p to no Of il underles valey bt e Daoa ru ad Lyons and group akota D een betw y lle a v s lie r e d n u ainly M cr o di sl i Maio flatirons s n o r i t a l f anitou M f o s n tio r o p e p lo -s ip d on ccurs O s- y lle a v t en u seq b su in s e g id r Low st stat n t kt group akota D e th in m tu tra s t n ta is s e R ___ 1 ' i 4

legion Studied The region chosen for detailed study Is located within the Colorado Springs quadrangle, along the Front Mange in east central Colorado, including portions of Ml Paso, Teller, and Pueblo counties (Figure 1), The piedmont flats here are well developed, unusually well preserved, and their pattern of dis­ tribution shows ^lear relationship to the modern valley bottoms*

Geologic Setting The geology of the region is typical of the foothills belt* Sedimentary strata outcrop in the piedmont, and older granitic rocks form the mountain slopes to the west* The stra- tigraphic section is shown in tabular form in Figure 3, to­ gether with the topographic significance of each llthologlc unit. The most important of these units is the Dakota group, which for purposes of this paper, includes both the Lakota and Dakota sandstones and the intervening fuson shale. Where pre­ sent these strata form a prominent ridge which divM.es the re­ gion of study into significant topographic units. These rela­ tionships may be seen in Plate 1*

Structural Setting The structure of the eastern part of this region is homoolinal with a thick sedimentary section dipping to the east. Folding in the southwest portion has produced the Med Greek Anticline, a broad southward-plunging structure. The Cheyenne Mountain Thrust Fault has steepened the attitude of strata adjacent to the mountain base in some places, causing 5 overturning and cutting-out portions of the normal stratigra- phie se c tio n , A stru ctu ra l embayment o f sedimentary rook oc­ cupies a westward indentation of the mountain front in the area west of Colorado Springs,

F ield Work The data in t h is paper were c o lle c te d by d e ta ile d mapping of the region on an aerial photograph base during the summers of 1940, 1941, 1946, and 1947* and the winter of 1945*1946. n o­ vations and sections were measured by the use of the Paul in Al­ timeter and certain key areas were mapped by plane table* Cross se ctio n s shown (P late 2) were measured by the la t te r method. The contour maps of Figures 4* 8, 11, and 13 are taken from ad­ vance pencil sheets of maps being drafted by the United States Geological Survey, Denver, Colorado,

Acknowl edgeznen ts The writer is indebted to Dr. C. J", Boy, director, of Louisiana State University's Field Camp, and to numerous mem­ bers of the camp staff, particularly Dr. K. M. Hussey, Dr. K*P. McLaughlin, G. A. Stokes, C. H. L au tier, C, L* B u tto rff, and H, E. Kane, each of whom served as assistants during various phases of the field work. The author is further indebted to Dr, H. N. Fisk, Professor of Geology of Louisiana State Univer­ s it y , fo r valuable f ie ld c r itic is m and comments on the manu­ script; and to Dr. B. Russell, Assistant Director of the School of Geology, Louisiana State University, for helpful cri­ ticism and suggestions. Grateful thanks is also extended to Mrs. R. W# Mage®, Librarian at the Colorado Springs Public 6

Library, and bo Mr# I* W* Magee, also of that city, for encour­ agement and material assistance# The conclusions in this paper, however, are the writer's own and do not represent the opinions of any of the above mentioned persons#

Previous Work The physiography of the Colorado Springs quadrangle has not heretofore been studied in detail, though limited references to laadforme may be found in the literature# The earliest pub­ lished observations were made by Hayden (1873) who noted the broad alluvial deposits along the eastern flank of the mountains in the vicinity of Colorado Springs, the materials in which were derived from the rocks of the mountain region# Finlay (1916), pointing out the existence of long tables of gravel along the mountain base, concluded that they once formed a continuous slop­ ing plane. Van Tuyl and Loveriag (1935), indicate in aerial views erosion su rfaces on benches and spurs in the v ic in ity o f Cheyenne Mountain (Plate 1), These features are described in the present paper. Van Tuyl and Levering conclude that pedimentation was re­ sponsible for the origin of these levels and that their develop­ ment occurred during the Pliocene# CONCEPTS OP ORIGIN OP BEDROCK EROSION SURFACES

Th® origin of bedrock surface® with characteristics and physiographic position similar to those herein described has been a controversial matter since such features were first rec­ ognized by Gilbert (1877)* These surfaces have been given var­ ious names by different writers, including the terms? pediment, conoplain, suballuvial bench, rock fan, rook plane, peripediment, and pediplane. Two major theories of development of bedrock ero­ sion planes in arid and semlarid regions have gained popularity. In his work on the Henry Mountains, Utah, Gilbert (1877) referred to the bedrock erosion planes which flank the mountains as "hills of planation", suggesting that their development has been due to the lateral oorrasioa of graded streams which flow during times of cloudburst runoff, Subsequent students of the problem, who have agreed with Gilbert In principle and have de­ veloped and modified the lateral plan&tion theory, include lee

(1 9 0 0), Fenneman (1905), Ogllvi® (1905), Baker (1911), Paige (1912), Bryan (1922, 1925), lokis (1928), Blackwelder (1929, 1931), Johnson (1931, 1932) 4 Field (1935), Mackin (1937), Brad­ ley (1940), and Howard (1^42). One of the strongest exponents of this idea was Johnson, who maintained that the mountain front retreats by the undercutting of its base by laterally swinging streams which develop a plan© of truncation across the bedrock of the mountain base. The mountain slope retreats by this under­ cutting activity and the bedrock plane is extended Into the moun­ tains. Johnson used the terms "rook fan" and "rock plane" for these surfaces. 7 8

McGee (1897) attributed the origin of rock planes in southwestern Arisona and Mexico, which he called "pediments", to the action of sheetfloods occurring following cloudburst action* Davis {1905), Influenced by the work of Passarg® (1904) la Africa, preferred McGee*a explanation to the lateral oorra- sion theory, though he later accepted other possibilities for the origin of these features* Tolrnan (1909), however, showed that the sheetflood is a depositing rather than an eroding a~ gent, and pointed out that it occurs more as a result of the pre­ sence of the bedrock flat than as an agency for its development* Opposed to the advocates of lateral planation are work­ ers more or less in accord with Lawson (1915), who related de­ velopment of erosion planes on the bedrock of the mountain base to the retreat of mountain fronts in arid and semlarid regions. Subaerial weathering processes, r ill wash, and stream transpor­ tation remove the material from the retreating mountain slope* The piedmont bedrock surface, termed the "suballuvial bench", Is developed as a surface of transportation between retreating mountains and fillin g basins* Davis (1930, 1936, 193®) agreed essentially with Lawson* Other workers who differ only in details with this concept are Mortensen (1927), Berkey and Morris (1927), Waibel (192®), Bryan (1922, 1925, 1940), Bryan and McOann (1936), Gloek (1932), Rich (1935), and Bradley (1940)• Bryan recognized both lateral planation and retreat of slopes under weathering, and the removal of the weathered material by flood rills, as important activities in producing extensive rock planes* He de­ signated these surfaces "rock pediments"* 9

fhe tendency in reoent years has been to accept the com­ bination of these concepts in explaining the origin of bedrock planes of erosion# Bryans acceptance of a chronological relat­ ionship, with early lateral planation followed by later weather­ ing (1936, 1940}, was a step in that direction* Oilluly (1937) concluded that in the Ajo region in Arizona lateral corrasion, r ill wash, weathering, and the removal of weathered debris by the various agencies operate together, though at some particular place any one m y dominate# In the Ruby Mountains, Nevada, Sharpe (1940) concludes that a portion of the bedrock surfaces present are a result of lateral planation, but that the remainder were caused by weathering and slope transportation* Ray and Smith (1941) essentially agree on the combination hypothesis a® does also Benny (1941)* TOPOGRAPHIC TOXTS OF TO COLORADO SPRING- RIOION

Local sim ilarities in the piedmont interstream Flats per* mite division of the Colorado springe region into four main areas, each of which differs from the others as to elevation of surfaces present and location with respeot to the Dakota ridge, Two of these, the Southwest Area and the Manitou Embaymeat Area, are small sections of the piedmont region, lying between the Dakota ridge and the granite core of the mountains. The lower Fled* moat Area, largest of the divisions, trends nOrth*south through the entire central portion of the Colorado Springs region, It includes all of the piedmont east of the Dakota ridge, and also includes that portion east of Cheyenne Mountain where the Dakota formation has been out out by thrust faulting, A fourth unit, the High Divide Area, forms a long, narrow section along the east margin of the Southwest Area, lying between the little Fountain and Turkey Creek drainage systems. The location and extent of these areas may be seen in Flats 1* The Southwest Area is a broad topographic basin developed along the axial portion of the Red Creek Anticline, This area is rimmed by the Dakota ridge through which the drainage lines leave the basin by means of relatively narrow watergaps. Red Creek and its tributaries drain the central portion, whereas Turkey Creek and its northern tributary, L ittle Turkey Creek, drain the northeast portion. The Manitou Bmbarmeat Area, a broad structural sag in the mountain front west of Colorado Springs, forms a westward

10 11

extension of the piedmont bordered on the east by the Dakota ridge. The main drainage here is Fountain Creek which flows southeastward in this section of the piedmont. A number of smaller tributaries, including Sutherland Greek on the south, and Black Canyon and W illiams Canyon on the north, form the minor drainage of the area. The Lower Piedmont Area slop es eastward from the Dakota ridge, which separates it from the two smaller areas just de­ scribed in the north and south central portions of the region. A similar eastward slop© is present along Cheyenne Mountain in the central portion of the region, and in the southern portion east of the High Divide Area which separates it from the South­ west Area. Humorous east- and southeast-flowing tributary streams cross this area to join Fountain Creek, the master drainage of thi3 section of the piedmont. Included among these are Bear and Cheyenne creeks in the north central portion; Lime Kiln Creek in the central portion east of Cheyenne Mountain; Little Foun­ tain Creek and its two major tributaries, Little Bear and Bock creeks, in the south central portion; and a number of unnamed streams which occupy the southern section of the area between L ittle Fountain Creek and the II Paso-Fueblo County Line. The section of the area northwest of Colorado Springs is drained by Monument Creek and its northmost tributary, West Monument Creek. Camp Creek, another Fountain Creek tributary, drains the area west of Colorado Springs. PIEDMONT INTEHSTREAM FLATS

Marked differences in elevation distinguish the main pied­ mont lute*stream flats and permit their separation into High Level, Intermediate and low level groups. Each of these groups is made up of several minor levels which show an interrelation­ ship and merge in the upslope direction, A less marked mergence of this nature occurs between the groups. In areas where all three groups are present! each occurs as a unit at distinctly different elevations with respect to the mountain front. De­ sp ite t h is marked d ifferen ce in e le v a tio n , the low le v e l and Intermediate groups are equivalent in age. The Intermediate Group, however, is restricted in occurrence to the higher portions of the piedmont confined between the mountain front and the Dakota ridge, whereas the Low Level Group is not thus structurally con­ fined and occurs in the broader Lower Piedmont Area, A minor group of surfaces, the Stream Terraces, occurs in the interval between the piedmont inter stream flats and the mod­ ern valley bottoms. These, consisting of several minor levels, merge upstream with the present valley bottoms in the region adj­ acent to the mountain base. The highest of these terraces is closely related in elevation to the adjacent flats, tending to merge with the latter in the upslope direction.

High Level Group Surfaces of this group of piedmont flats occur along the mountain front in each of the piedmont areas defined. These are characterised by having the greatest elevation and, for the most part, the thickest alluvial sections. The most extensive of these

12 13 occur along the Manit©u Kmbayment Area and in the High Divide Area between the L ittle fountain Greek and Turkey Greek drainages, surfaces in the ether two areas being small and widely scattered (Plate 1)* Because of this scattered distribution, positive cor­ relation can be made only in restricted areas* The elevation of the surfaces generally increases northward in the piedmont* The group Includes several minor levels with maximum elevations rang­ ing from 6,950 to 7,500 feet* The most extensive remnant of the group is the Deadm&n Canyon Surface, described in some detail be­ low, located in the High Divide Area* The northern portion of this surface is shown in the contour map of Figure 4.

Interm ediate Croup Other piedmont flats occur below the surfaces of the High Level Group in the Southwest Area and in the Manitou Km- bayment Area (Plate 1)« Several minor levels are included with mountain base elevations ranging from 6,650 to 7»050 feet. The best examples of these occur in the Red Creek and Little Turkey Creek drainage basins* The L ittle Turkey Creek surfaces are de­ scribed below and are illustrated in the contour map of Figure 8*

Low Level Group The majority of the surfaces in this category have .maxi­ mum elevations ranging from 6,300 to 6,900 feet. In the northern portion of the Lower Piedmont, however, Low Level surfaces occur up to 7,300 feet in elevation. The group consists of several minor le v e ls r e s tr ic te d In occurrence to the Lower PIddmont Area* The most extensive of these surfaces occur along the north side 14

of Book Crook and form the surface of the feature known as *The Mesa11, on th e interstream divide between Camp and Monument creeks in the section northwest of Colorado Springs (Plate X). Both the Book Creek and The Mesa Surfaces are described below. The eonteur maps of Figures 6 and 7 supplement these descriptions.

The Stream Terraces This group of minor levels, varying in number between four and seven, occurs in all the major and many of the minor stream valleys in each of the topographic units of the region. These levels are lower in elevation than interstream flats In the same locality and are much more restricted in extent than the latter. The group is described in more detail below* jmmmm gaotqh sorfaob of the m an j i m gboot

Location and Extent This surface of the Ugh Level Qroup, located in the High Bivide Area between the L ittle Fountain and Turkey Greek drainage basins, extends slightly east of south from Beadman Canyon for a distance of 12 miles within the Colorado Springs quadrangle (Plate 1)» Broad continuations also occur in the Pueblo quadrangle to the south, particularly along the east side of Fountain Greek north of Pueblo {Gilbert, 1&9?}, The Beadma Canyon Surface is divided into a northern and a southern portion by a relatively deep canyon. The Dakota ridge bounds the northern portion along its western side for two miles (Figure 4 ). The southern portion, s long flat-topped ridge of irregular width, borders the east side of Turkey Creek Valley for a distance of 10 miles (Plate 1)* The surface reaches a maximum width of two miles about midway along the northern portion, narrowing both to the north and south. The long southward extension varies in width from a few feet to half a mile. Minor ©regional breaks interrupt its southward con­ tin u ity , A ctive d is s e c tio n by a fine*" texture# system of g u llie s and small canyons has given the eastern edge a frayed appearance. Landslide and slumping action, particularly along the eastern edge of the northern portion, is also reducing the ail®© of the su rface.

Surface Features The otherwise level aspect of the northern portion of the surface is diversified by a number of broad, relatively shallow

15 H

swales wlitefc radiate from its horfchwest m i (fig u res 4 m i 6)*

OLD CHANNELS^sjOi MODERN DRAINAGE

figure 4: - Deai&a* Canyo* Surface of the High Level Group 17

If extended to the northwest these swales converge on the moun­ tain front between Little Fountain and Little Bear creeks. These are old stream courses which once formed an integrated system on the surface. The lower end of each is occupied by an actively, headward-growing gully. The largest and deepest channel approxi­ mates the eastern base of the Dakota ridge. Three levels of the High Level Group are contained in this surface, the highest being present over most of the northern portion (Figure 4, (la)), where­ as the lowest is more restricted, forming the bottom of the deep­ est channel just noted (Figure 4, (lc)J. The surface of the south­ ern portion is an intermediate level between these two (Figure $),

Figure 5: View northeast on the southern portion of the Deadxoan Canyon Surface about fiv e m iles from the mountain base. The flat aspect of this surface is apparent in this view. The even-crested sky­ line in the distance is the so-called Rocky Mountain peneplain at approximately 10,000 feet in elevation. 18

Elevation and Slop© The h igh est macaber of the Deadman Canyon Surface forms a fan-shaped feature, three and on© half miles in extent, sloping southeastward from an elevation of 6,760 feet (Figure 4 , ( la ) ) , the average drop being 100 feet per mile. Bemnants of this sur­ face are also preserved on spurs along the mountsinward edge of Deadman Canyon (Figure 21). The restored profile in these upper­ most parts of the former surface is concave-upward, the average slope being 250 feet per mile (Plate 3, (1)}. The level preserved in the southern portion of th© Headman Canyon Surface (Plat© 3» (2)) slopes southeastward from 6,630 in the north, the average slope through this portion being 100 fe e t per mile. Flat-topped, detached spurs, 7 ,1 0 0 feet in elevation on the mountain front near Turkey and L ittle Turkey Greek canyons are correlated with this level (Figure 21). Th® average restored slope from these remnants to th© southern portion of the headman Canyon Surface is in the neighborhood of 250 feet per mile, giving th© level an upward-coneavity in this direction (Flat© 3, (2 ))* Preserved portions are essentially flat in cross-profile. The lowermost le v e l of th® Deadman Canyon Surface, in the bottom of the westernmost of th® old channels of th® nor­ thern portion, extends two and one half miles southward with a slope of 100 feet per rail© (Plat© 3, (3))* The north end is at 6,730 feet. The old channel is rounded in cross-profile in its upper, narrower end, whereas th© downslope portion is essentially flat. This level Is also present along th© east side of Turkey Creek Valley, occurring on terrace-like remnants 40 to 50 feet below th© level of the southern portion of the Deadman Canyon 19

Surface (Plate 21, (3®)).

The Alluvium Alluvial thicknesses differ under each of the three le v e ls of the Deadman Canyon Surface. A continuous a llu v ia l section is exposed along the northeast edge of the uppermost member level above the valley of Little Fountain Creek (Figure 6 ), This section thickens from 90 feet in the west to 110 feet in the east. Along the longitudinal axis of the level, however, the alluvium thins from 90 feet in the northwest to 50 feet in the southeast in the three and on© half miles of extent.

Figure 6 j Alluvial section overlying Pierre shale near the east end of the northern portion of the Deadman Canyon Sur­ face south of Little Fountain Creek. This section is about 100 feet thick. Note th© large boulders and the tendency toward stratification. One of th© swales In the surface is indicated by an arrow. 20

The alluvial section in the southern portion of the surface thins from 40 feet la the north to 10 feet in the south, in 10 miles of extent* No differences in thickness were noted in cross sectlen s* The lowest level is underlain by 25 feet of alluvial sec­ tio n in th© north, thickening to 40 f e e t downslop©* In ores© section at th© north end the alluvium thin® toward the sides of th© channel bottom* Farther downslope, however, it is of uniform thickness* Representatives of the High level Group near the mountain has© have alluvial sections which thin upslope. In some instances these may be residuals of sections that were originally thicker* A 20 -fo o t sectio n in a sm all remnant in Deadman Canyon (P late 1} may be such a residual deposit which was thicker when formed* Most of the mountain spur representatives of this group of levels are devoid of alluvial debris* The alluvium is a coarse fanglomerate composed of igneous rock fragments with minor amounts of sedimentary rock intermixed. The amount and type of the latter depends on the various strata outcropping toward the mountain front. Most of the sedimentary fragments consist of more resistant rook types, Dakota sandstone furnishing the bulk of these* Variations in lithologie character of the alluvium are an aid In distinguishing between the three member levels, as well as in determining the source of the alluvial debris. The highest level contains an abundance of rhyolit© fragments, as does the alluvium of th® lowermost level. Th® rhyolit® is absent, however, toward th© south, except for scattered fragment® which occur a i along the ©astern edge of th© surface; This constituent is lack­ ing in a ll Sigh Level Group remnants southwest of Little Turkey

Greek (Plate 1 ); because the only outcrops of this rock occur farther north, between Little Turkey and L ittle Fountain creeks, and in Hook Or©ok 0anyon. Th© alluvium o f th© Deadman Ganyon Surface is massive in general, with localized examples of distinct bedding and sorting. This material ranges in size from fin© silt and sand up to bould­ ers three feet in diameter. The larger fragments, cobble and boulder sizes, show th© rounding effect of water transport. The coarsest material is found upalopo, a gradual gradation to finer sizes occurring in the downsiope direction. Thin, irregular lenses of pebble and cobble, "mortar-beds* cemented with calcium carbonate occur throughout the seertion in many exposures. There is a marked concentration of this material near th® base.

The Bedrock Surface Below th© alluvium is a bedrock erosion surface developed across th© upturned edges of eastward-dipping strata. This sur­ face slopes to the east and southeast, and is comparatively plane. The chief departures from smoothness are swale-like de­ pressions. The dipping strata truncated rang® in age from Dakota through Pierre {Figure 3), the major portion being developed on the Apishapa formation. There is close agreement between th® at­ titude of surfaces and that of the bedrock truncation,

Other High Level Group Surfaces Representatives of th© High Leva! Group occur on flat- topped granite spurs along th© mountain front from Bock to Bed 22

creeks• Elevations vary from 6,950 to 7 ,2 5 0 feet, Surfaces are most conspicuous near the mouths of the several major canyons, and in positions indicating membership in the High Level Group, Because they are small in area and widely scattered, their cor­ relation along the mountain front is hazardous. Only in certain areas,such as along several well preserved spurs on th® southeast slopes of th© dome-like rhyollte body located west of th© Foun­ tain hogback in Deadman Canyon, is th© correlation more certain (figure 21, (le)). Th© lower ends of these spurs are at about 7 ,0 5 0 feet and the longest (1300 feet) rises steeply into the mountain mass to 7 ,2 5 0 f e e t . faaglomerat©-capped Fountain and Fountain-Lyons knobs on the L ittle Turkey-Turkey Creek divide preserve small fragments o f the High Level Group. Somewhat larger remnants occur on elong­ ate ridges which decrease in elevation toward the southeast along the southwest side of Turkey Creek. Additional one® are present along the east side of the Bakota ridge downstream from where it is breached by Turkey Creek (Flat© 1). A small isolated sur­ face belonging to this group is present on the south end of th© granite ridge along th© east side of Bed Creek, and a similar remnant occurs on th© alluvium-covered shoulder of Table Moun­ tain at the western edge of the Southwest Area (Flat© 1). The most extensive remnant in th® northern part of the quadrangle is located along the north edge of the Manitou Bia- bayiaent on the south slope of the Rampart Rang© (Flat© 1 ). This surface forms a high ridge one mil© and a quarter long on th© east side of Black Canyon. Locally, it is underlain by 23

45 fa«t of alluvium. The glope is southward from 7 ,3 7 5 fe a t, at about 400 feat per mile,. A highly dissected lower level flanks the western edge of the surface Just noted. At its southern end th© bedrock lies ap­ proximately 60 feet lower in elevation than on the adjacent high­ er level to the east, Fanglomerate is absent, excepting toward the north end of th© remnant, where it is 40 feet thick. This de­ posit is well stratified, locally cross bedded, and consists of angular to sub&agular granitic pebbles, ”Mortar-bedn lenses, five to six inches in thickness and cemented with calcium carbonate, occur throughout th© deposit {figure ?)* This section contrasts strongly with th© alluvium of th© higher level to th© east, th© latter being poorly stratified, poorly sorted, and having a much coarser texture, with two to three foot granite boulders scattered throughout. In this higher level alluvium the "mortar-bed” lenses are confined to the basal several feet, Th© surfaces of these two levels merge upslop© to the north. Several smaller terraces are present on the slo p es leading down toward the Garden of the Gods east of the higher level, A three-quarter-mile long, north-south trending piedmont surface is preserved on the d ivid e between W illiams Canyon and the west fork of Black Gaayon In the northwest portion of the embayment. This surface is underlain by alluvium which in turn overlies a bedrock surface developed across th© upturned edges of southward-dipping Bawatch, Manitou, and Fountain strata. Th© slope is southward at 300 feet per mile, from 7*200 feet in the north. The fauglomerat© Is 30 feet thick in the southern portion and lenses out in the upslop© direction. Several lower smaller surfaces fringe this remnant. 24

Figure 7: Fine-textured "Mortared" leases In angular, pebble-* size alluvium on tbs south slope of the Hampert Range. Note the relatively flue texture and fair stratification of this material. Gross-bedding is also visible near the base of the exposure. This is the lowest of the High Level Group of surfaces on the divide between Black and Williams canyon. This section is about 15 feet thick* Numerous fla t-to p p ed gran ite spurs occur along the mountain front in the western and southern portions of the embayment a t elev a tio n s between 7,000 and 7,300 feet* The mountain front north froia th© ©mbayment is devoid of High Level remnants, except for on© small surface preserved on steeply- dipping Manitou strata about two miles from the north edge of the quadrangle (Plate 1). Its elevation is 7,500 feet. Th© al­ luvium, only a few feet in thickness, lenses out westward across 25

the Sawatch-granit© eontset. Th© underlying rock surface, however, continues for a short distance westward to an abrupt end against steeper mountain slopes* LITTLE T0HKBY g e m : sprfaosi

of m i tMmtmnuTB mow

lo c a tio n and Extent The kittle Turkey Greek Surfaces are located in the kittle Turkey Greek drainage basin of the Southwest Area. They consist of three minor levels which form the Intermediate Oroup of pied­ mont f l a t s la t h is area (F la ts 1 ) . Of the three le v e ls the mid* die one is most extensive, being preserved in a broad continuous surface along the northeast side of little Turkey Greek (Figures 8 and 21)* This surface extends southeastward from the mountain base for a distance of one mile and then southward for an addi­ tional one quarter of a mile. The greatest width is one quarter of a mile about midway along its southeastward extent* The Dakota ridge lim its it on the east. A smaller remnant of the same level occurs as a flat spur extending eastward from the mountain base in the southwest corner of Deadman Canyon. The level also forme a surface on the south end of the Fountain hogback in the same locality (Figures 8 and 21)♦ Additional remnants are present in the area southwest of the Highway 115 bridge across Little Turkey Greek, as smaller surface fragments along the mountain base far­ ther to the southwest, and on dissected terraces along Little Turkey Greek to the south. The highest level of the Little Turkey Greek Surfaces occurs as a small remnant just southwest of the mouth of Little Turkey Greek Oanyon and, as s till smaller fragments along the mountain base a short distance to the southwest (Figures B and 21).

26 27

The lowest L ittle Turkey Oreek surface la preserved on narrow terraces along the drainage lines of thia section below the higher levels noted (Plate 1)*

6700

Modern Drainage

S c a le - Feet 2,000

Figure P? - L ittle Turkoy- Creek Surface'i of the Intern lediato Croup 28

Surface features These upper piedmont surfaces are quite flat with only scattered knobs and ridges of fountain or Lyons strata project­ ing above them# Some of these projections are capped with alluv­ ium and represent small residuals of the higher levels of the Intermediate and High Level groups#

Elevation and Slope The highest of the L ittle Turkey Creek Surface®, located just south of th© mouth of L ittle Turkey Greek Canyon, slopes northeast toward that stream fro© a mountain base elevation of 7 ,0 5 0 feet, the gradient being LOO feet per mile (figure 3, (2a)}* The profile of this surface is shown in Plate 3* The next lower level slopes at 200 feet per mile to the southeast and then south along L ittle Turkey Greek from a mount­ ain base elevation of 6,870 feet (figure 8 , (2b))# The eastern portion of this surface has a local northeast slop© toward Head­ man Canyon. The surface profile is shown la Plate 3. Th© small ridge-like remnant of the same level in the southwest corner of Deadman Canyon (Figure 3, (2b)) elopes eastward fro© 6,950 feet, at 400 feet per mile. The fountain hogback remnant In the same locality has a much ©ore gentle slope to the south. The surface® preserving the level southwest of the Highway 115 bridge across Little Turkey Creek have southeast slopes of 300 feet per mile from a maxima© elevation of 6 ,8 5 0 feet. Cross profile on th© latter reveals an upward-convexity opposite a minor canyon in the moun­ tain front above them. Dissected terraces of this level down­ stream along L ittle Turkey Creak have slopes along thi® stream 29

slightly greater them the preseat stream gradient. A strong stream- ward slope a ls o e x is t la these* They stand about 50 feet above the present stream bottoms in the upper piedmont. The lowermost level occurs on terrace® along little Tur­ key Creek, similar in every respect to the higher ones just de­ scribed, at a height of about 25 feet above the present valley bot­ toms in the upper piedmont {Figure $, ( 2e))*

The Alluvium The alluvium of the little Turkey Creek Surfaces is a fanglomerate, similar in general lithologie character to that al­ ready described, differences existing being minor and of local ex­ tent. This material Is most coarse in upslope portions, a gradation to finer texture occurring in the downslope directions. Bedding and sorting are poorly developed, except locally# Th© average grad© size, along sections exposed in Highway 115 readouts, is two to six inch cobbled in a coarse sand and pebble matrix# The alluvium in the surface along th® northeast side of L ittle Turkey Creek thickens from five feet near the mountain base to 15 feet in the eastern extremity near Highway 115# In north- south section along this highway a similar downslope thickening of from five to 15 feet occurs. Dissected terraces of this level, and th© lowermost level to th© south along L ittle Turkey Creek, are underlain by 10 to 15 feet of alluvial material. Th© highest of the L ittle Turkey Creek Surfaces has a maximum of 25 feet which thins in the upslope direction# Rhyelite fragment© occur in the alluvium of restricted portions of the surfaces. The highest level alluvium contains none. 30

fills constituent Is present in downslope alluvial sections of the middle level of the group along the northeast side of little Turkey Greek, and for about one half of the upslope extent along the north edge* It also occurs In the small remnant of the same level on the Fountain hogback to the north* It is lacking, however, in the allu­ vium of the same level to the west of the latter. fhe presence of this rock type indicates the former extent of this level of the Little Turkey Creek Surfaces in upslope direction to the rhyolite outcrop west of the Fountain hogback in Steadman Canyon (Figure 21, ( l o ) ) .

the Bedrock Surface The bedrock surfaces of these levels are similar in every respect to those already described, with the exception that the rocks truncated consist of older and more resistant types (Manitou through Dakota)* Remnants of higher levels project above the bed­ rock plane in some localities and minor channel-like irregularities exist below it*

Other Intermediate Group Surfaces Surfaces belonging to this group occur along Turkey Creek, the lowermost level being preserved as a terrace along both sides of this stream (Plate 1 and Figure 9). The slope in this instance is southeast at 150 feet per mile (Plate 3, (6 ))* The alluvium is

15 to 20 feet thick. All three levels of the Intermediate Croup occur in step- like fashion adjacent to the mountain base just north of Turkey Greek (Figure 21). The highest forms flat-topped elements on Manitou 31 spurs at 6,800 feet* The next lower level Is present on alluvium- ©overed ridges at 6 ,6 5 0 feet* The lowermost level is preserved as a bread bedrock flat about midway of the L ittle Turkey-furkey Greek divide, sloping at 200 feet per mile toward Turkey Greek* This surface also has a transverse slope toward an incised channel along its western edge* The alluvium has been stripped from this feature, exposing a relatively flat bedrock plane developed across southeastward-dipping fountain strata* Ho sharp irregular it lee exist below this level (Figure 9)*

Figure 9* View south from Highway 11$ along the stripped surface of the lowest of the Intermediate Group levels Just northeast o f Turkey Greek* This f la t is an erosion plane developed on gently eastward-dipping Fountain strata* Turkey Greek valley extends from right to left in the middle distance* The high tree-covered ridge beyond Turkey Creek la a remnant of the High Level Croup along the southwest side of this stream* 32

An extensive surface, correlated with th© middle of th© three levels of the Intermediate Group, occurs along the west side of led Creek in the Southwest Area (Flat® 1). The slop© is south** ea st a t 220 feet per mile, from an upslope elevation of 6 , 6?5 f e e t . A gentler slope element exists toward Bed Greek, which is Incised below the eastern edge of the surface. The maximum alluvial sec­ tio n i s 20 feet, thinning occurring in the upslope direction. In cross-section, as revealed in readouts through the southeastern portion, the alluvium is thinnest in the western edge (10 f e e t ) , thickening toward the east (20 feet)* The underlying bedrock sur­ face truncates southeastward-dipping Fountain strata, A typical channel irregularity in this surface is shown In Plate 2. The same level is preserved southwest of the lower end of the surface Just described, separated from the latter by a broad gully. Here, a 35-foot alluvial section thins to five feet downslope toward the south. Three Intermediate Group levels are present on a number of small surfaces northeast from Bed Creek (Flat© 1), each having individual characteristics of slope and thickness of alluvium, The mountain base elevations of these increase progressively to­ ward the high portion of the Bed Oreek-furkey Creek divide. On that divide, Just south of Turkey Creek Canyon, there i® a small fan-shaped surface which lacks the alluvial section common to most of these features. The apical portion of this level la at 6,700 feet and the slop© is southeast at 350 feet per mil©. Th© transverse profile is convex-upward (Figure 1 0 ), 33

Figure IDs Stripped piedmont fla t on the Red Oreek-Turkey Greek d ivid e in mount a inward view from Highway 115 Iimmed­ iate foreground}* The fan shape and convex-upward transverse profile are apparent in this view, The tree-covered h ill in th© right mlddleground is a remnant of the High Level Group along the southwest side of Turkey Greek, The Intermediate Group is represented by a multiple ar­ rangement of several surfaces in the Manitou Embayment Area, The most extensive of these occurs along the southeast side of Suther­ land Greek and slopes northeastward at 300 feet per mile toward Fountain Creek (Plate 1), Alluvial sections under these remnants vary from 15 to 20 feet, Texturally and lithologically this mater­ ial is similar to that already described, except that th© boulder sizes range up to 10 feet in diameter. The Dakota ridge lim its the extent of these surfaces on the east* book o m m mmWAxm o f t o low mmi* antooF

Location ant 1st ant This la a group of three minor levels belonging to the Low Laval Oroup which occur in flanking position along the moun­ tain baaa north and south o f Rook Croak in the Lower Piedmont (Plate 1). the highest of these is preserved on several, fang- loaerate-oapped ridges which extend into the upper piedmont be­ tween Rock Creek and Lime Kiln Talley (Figure 11, (3a))« ^he middle level of the three occurs in lower level continuations of these ridges toward the southeast (Figure 11, (3b)). Detached rewants of the same level are located farther east along the Lime Kiln and Rook creek drainages. Low h ills and ridges above lower iaterstream flats, along the north sides of lock and Lit­ tle Fountain creeks, are also correlated with this level. The lowermost level of these surfaces extends along the north side of Reek Creek, from the mountain base eastward for approximately eight miles to the valley of fountain Creek (Fig­ ure 11, ( 3c)). This surface gradually widens eastward in the piedmont to a maximum of one mile across the lower extremity. The same level is present in flanking position along the mountain base between L ittle Fountain and Bock creeks and, as small detached remnants farther east along these drainage lines (Plate I)#

34 35

MOUNTAIN

hW y

■ 2 - ° ° ° ' ■ Figure 11: - Pwcck Creek Surfaces of the Low Level Group0 36

Surface features The lower of these minor levels of the group are surmounted by butte-like remnants of the higher member levels. On some of the more extensive surfaces, particularly the lowest level north of Rook Greek, there is an irregular system of broad, shallow swales which have an eastward trend down the slope# These are old stream channels•

lievation and 31ope These piedmont flats have progressively decreasing slope east or southeast toward the valley of fountain Greek (Figure 11 and Flats 3). Mountain base portions of the three member levels north of Rock Creek have northeast components of slope away from the canyon mouth of this stream. The broad inter stream flat of the lowest level between little Fountain and Rook creeks has a similar d irectio n of slope away from L ittle Fountain Greek* Cross p r o file s on surfaces farther east, however, are essentially flat. The highest level is at 6,550 feet at th® mountain base just north of Rock Creek, rising to 6,650 feet in the westward in­ dentation of the mountain front at Lime Kiln Valley (Plate 1 ). This level slopes eastward at 400 feet per mile in its upper pied­ mont portion (F la ts 3, (7))* The next lower level slopes eastward at 200 feet per mile from a maximum elevation of 6 ,3 5 0 feet, decreasing in slope to 100 feet per mile In two and one half miles of eastward extent

(Plate 3, (8 ))# The lowermost level is at 6,373 feet at the mouth of Rook Creek Canyon. I t s eastward slope decreases from 200 to 50 37

feet per mil® in the eight miles of extent (Plat© 3, (9)}* The same le v e l between L it t le foun tain and Rook oroeks is at 6 ,4 0 0 feet at the mountain base. The slope here is toward the northeast, declining from 200 f e e t to 100 fe e t per mil® in two and one half miles of extent.

The Alluvium The alluvium in these remnants, except for minor dif­ ferences In texture and thickness, is similar to that already described. Maximum sections under the high, middle, and low mem­ ber levels in the Rock Greek 3 urfac©s are respectively 40, 25, and 20 feet* Thinnings occur in both th® upslope and downslope directions from sections of maximum thickness. Exposures in road- cute which pass transversely through the middle and lowest member levels of the surfaces show variable thickness. These sections are shown in P la te 2.

The Bedrock Surface These are east-and southeast-sloping planes which trun­ cate the underlying homo el Inal rook structure of the higher por­ tion in the Lower Piedmont Area. The surfaces are underlain almost entirely by east-dipping Pierre shale, except for th© Lime Kiln Valley section where a faulted sequence of Lykins, Morrison, Tim- pas, and Aplshapa is beveled locally (Figure 3). Small channels, extending from five to 15 feet below the bedrock level, are exposed in the Highway 115 roadcuts north of Rock Creek. These are shown in the sections of Plate 2 and in Figure 12. A 25-foot channel of this nature is present la the bedrock surface of the highest 38 level, along the abandoned portion of Highway 115 about one quar­ ter of a mile went of the sections shown in Plate Z*

Figure 12i View east in Highway 115 roadsat through the inter­ mediate level of the low level Croup in the Book Creek Surfaces. The channel**like irregularity In the middle of the view extends about 15 feet below the average bedrock level of the surface. The under­ lying bedrock is gently e a s t w a r d -dipping pierre shale. The coarse texture of the alluvium in this surface is apparent. fH8 MBA StJRFAOI OF IBS low iotsl anoup

Location and Sxtent This surface, located between Camp and Monument creeks (Plate 1), is fan-shaped and consists of three minor levels. It is detached from the mountain front and extends southeastward from a locality about three fourths of a mile east of Queens Canyon for four miles, gradually widening to a maximum of one and one half miles midway in this extent, The lower extremity has been dissected so as to consist of five narrow south- and southeast- trending spurs separated by deep gullies.

Surface Features the highest member level forms a narrow flat along the northeast edge of the surface (Figure 13, (3a)). the middle level borders this higher member on the west throughout the extent of the latter, and continues to the south on the longest of the south­ eastward-extending spurs noted above (Figure 13, (3b)). The low­ est lev elc forms the broad western portion of the surface, extend­ ing to the south on the two westernmost of these spurs (Figure 13, (3c)). these three levels give the Mesa Surface a step*!Ike ap­ pearance downward toward Camp Creek to the southwest. This surface is scarred by broadly rounded swales which radiate from the northwest end. These are old stream channels which once issued onto the surface from a major canyon in the mountains to the north (Figure 13)* The modern drainage i s work­ ing headward into the lower edge of the feature along these older drainage lines. 39 Mod ern Droinage Old Channels

Of

Figure 13: - The Mesa Surface of the Low Level Group 41

lle v a tio n and Slop®

the upslope end of the highest member level (Figure 1 3 , (Ja)) i s a t 6 ,6 5 0 feet and the slope is southeast, decreasing from 180 to 120 feet per mile toward the lower end, A higher, knob-like remnant, located at 6 ,7 3 0 feet a short distance to the north, indicates a rapid steepening of the former extent of the level in that direction* The cross profile is essentially flat.

The middle level of the three is at 6 ,6 0 0 feet in Its northwestern extremity, decreasing in gradient from 150 to 100 feet per mile down the slope toward the southeast (Figure 13, (3b))* This, and the highest level, tend to merge in the upslope direction* A transverse slope toward Gamp Greek to the southwest occurs on this member level of the surface* The lowermost level slopes from 6,575 feet In elevation toward the south, decreasing in gradient from 150 to 125 feet per mile in its extent (Figure 13, (3c))* Transverse slope is also to­ ward Gamp Greek to the southwest*

The Alluvium The alluvium of the Mesa Surface is similar in litho- logie and textural characteristics to that already described, the only differences being variations in thickness. The highest level is underlain by a 35-foot section in the northwestern end, thick­ ening to 50 feet some distance down the slop© and then thinning to 10 feet in the southeastern portion* A 25-foot section underlie® the upslope portion of the middle level of the surface. Two miles downslop© from this locality the alluvium is 30 feet thick under the center and thins to 15 feet 42

in the east and west margins of the level#

■ /. ,/ • ■!)■ :; - s' ; - I'■ -

Figure 14* Alluvial section (approximately 15 feet shown) in Colorado Springs City travel Pit at the southeast end of the Mesa Surface .The fairly well-bedded, well-sorted zones shown are quite typical of allu­ vial sections in the distal portions of these piedmont flats. The lowermost level has a 4C-foot section in the north end which th in s rap id ly to 10 feet a short distance downslope and then thickens to 40 feet once more in the lower portion* Gross- section through the lower end shows thinning to both the east and west of the thick section. 43

Th® Bedrock Surface The bedrock surface is similar in general to others de­ scribed herein, The fanglomerate in all portions rests on a south- and southeast-sloping bedrock plane developed across the upturned edges of eastward-dipping Pierre strata, The bedrock surface is somewhat higher in p o sitio n under the h ig h est member le v e l than under the other two members. In east-west profile the combined bedrock surfaces of the two lower levels forms a broad rock flat, corrugated by a series of north-south trending sags which extend below the average level. These sags broaden and deepen downslope, being almost imperceptible in the northwest portion. Under the lower end of the surface they are 500 to 000 fe e t in width and ex­ tend from 1$ to 25 feet below the average bedrock level* A 4 0 - foot alluvial section in the Colorado Springs City Grave! pit in the southeast end of the surface marks the position of one of these sags (Plgure 1 4 ), a gradual rise in the bedrock surface occurfCag both to the east and west of this locality. The dissected condi­ tion of this portion of the surface makes it possible to trace this sag for some distance in the upslope direction* The westernmost spur of the surface contains evidence of a similar bedrock sag, here, the alluvial section, 40 feet thick under the center, thins to both east and west under a gradually rising bedrock surface, Th© depth below the average bedrock level in the center of this sag Is only 20 feet, shallowing in the up­ slope direction to 10 feet and leas. The southwest slop© of the surface toward Camp Greek Is reflected in the underlying bedrock su rfa ce. u

Other Low Level Surfaces Space does nob allow for a complete description of all other Low Laval Group su rfaces in the Lower Piedmont Area* Only the most extensive of these w ill be mentioned, along with data that the author feels is pertinent. Multiple levels of this group occur on large and small su rfaces throughout th© Lower Piedmont Area north of the to ek Creek Surfaces, some in flanking position along the east face of Cheyenne Mountain and soma above the broad valley flats of the Camp Carson area east of the mountain front (Plate 1). Th© most widespread of these forms a broad piedmont flat along the northeast sid e o f Cheyenne Greek valley* The slope here Is northeastward fro m a maximum e lev a tio n o f 6 ,5 5 0 feet, and at a gradient decreas­ in g fro m 350 t© 100 feet per mil®. The level is continuous to th© southeast where it forms broad terraces along both sides of Foun­ tain Creek valley (Plate 1)* A similar but less extensive surface occurs along the mountain base between Gheyeane and Bear creeks (Plate 1)# The upslope portion of this level is obscured by a number of steep a l l u v i a l fans of more recent origin, Th© level slopes northeast* ward toward Fountain Greek, from 6,440 feet at th® lower edge of these fans, at about 150 feet per mil®. A narrow, elongate remnant preserving the same level extends along the north side of Bear Creek with an eastward slope of 200 feet per mile* Smaller rem­ nants of a slightly higher surface stand above these piedmont flats between Cheyenne and Bear creeks. One of these higher levels

i s a t 6 ,4 5 0 feet near the mountain base, th© slope of the surface being northeast away from the mouth of Cheyenne Canyon* A5

A number of east and southeast sloping levels flank the mountain base in step-like pattern north of the Mesa Surface in the lower Piedmont Area {Plate 1). Similar surface occurrences are to be found in the Castle Bock quadrangle farther north. The southernmost of these surfaces la located about one mile north of Queens Canyon, It consists of three minor levels confined between the mountain baae and the Dakota ridge. The Lyons formation forms a high, sharp-crested ridge which abruptly terminates the northern portion of the surface along its lower edge. The southern portion, however, truncates the Lyons and terminates against the Dakota ridge, The mountain base elevation rises from 7,200 feet in the south to 7#300 feet in the north. The slope is southeast at between 500 and 6 G0 feet per mile. The three member levels of this surface merge in the upslope direction toward the mountain base. The allu­ vium, consisting mainly of angular, pebble sine debris, is approxi­ m ately 35 feet thick in the downslope portion and thins mountain- ward {Figure 15}* The Lyons and Dakota formations north of this locality are cut-out by faulting, A large, southeast sloping, fan-shaped surface is located Just north of where these ridge-forming units are faulted out (Plate 1), This surface widens eastward from an apex situated at the south side of a prominent minor canyon in the mountain front. The transverse slope of the surface is away from the drainage line which issues from this canyon* Elevation of the apical portion ie 7»275 feet, slope of the long axis of the level being southeastward at 4 OO feet per mile toward a high ridge of Laramie and Fox H ills sandstone (Figure 3)» known as Popes Bluffs (Plate 1). The downslope projection of this surface carries 46

it to tii© western tea© of this ridge, indicating that the fan was confined to the area west of this feature. Three related levels are preserved in the surface, the alluvial sections of which consist predominantly of angular, pabbl© size fragments of granite similar to th© grass being shed from higher portions of the range at th© present time. Maximum alluvial thickness is 4© feet in the distal portion of this surface.

Figure 15t Steeply sloping piedmont flat confined between the mountain base fright of view) and the Lyons and Bakota ridges (left of view). This view is southward along the east side of the Rampart Range. The white appear­ ing rock in the middle foreground is Fountain and, except for small projections above the level, is truncated by the bedrock plane of the latter*

Surfaces farther north increase progressively In elevation at th© mountain base. They are similar in all respects to those 47 described; except for details of degree of slope, extent of pre­ servation, and thickness of alluvial section* fSE SMAM TORAD«8

Stream terraces occur along a number of valleys* They for® flights of thinly-alluviated, rock-floored flats at various intervals below th® piedmont interstream flats. Some terrace rem­ nants, however, are detached from the valley sides. Th© number of terraces is not uniform, either in different valleys or in different portions of the same valley. The maximum observed, seven, appears to be characteristic of the major valleys several miles below the mountain base. Canyon portions of these valleys are free of terraces. The number of terraces present ordinarily in crea ses downvalley from the canyon mouth®, and the V ertica l intervals between them also Increase, Vertical spacing is somewhat irregular. Terraces clear­ ly differentiated at one place may merge elsewhere. The tendency is for each surface to merge with the modern valley bottom in an upstream direction, in order from lowest to highest. The maximum interval measured between adjacent terraces in downvalley posi­ tio n s i s 50 feet, the average throughout most of th© valley being 15 to 20 feet. The longitudinal gradient of these terraces approxi­ mates that of the modern streams, though some are slightly steeper and some more gentle in slope. Most have a transverse slope streamward, though in a few major instances the slop© is toward valley margins (Figure 16). Some of these levels have a paired relationship with a similar level on th© opposite side of the valley, though this is not always tha case*

U$ 49

Th© alluvium in these terrao© surfaces is similar to the fanglomerat© in the higher piedmont flats* The thictaes© varies from five to 20 feet in different localities* In general, however, i t i s a relatively thin blanket over the bedrock surface* the lat­ ter is similar to that of th© piedmont surface but of more lim ited exten t *

fig u re 16s View northwest toward L ittle fountain Greek Canyon from the south edge of the lowest level of the Low Level Group surfaces north of this stream* The broad flat leading up toward this canyon is the highest terrace level of the Little Fountain-Little Bear Greek drainage. This surface has a fan-like rela­ tionship to little Fountain Creek Canyon, trans­ verse slope being away from the stream which is in the far left of the view* CLIMATIC CONSIDERATION

Th© piedmont region drained by Fountain Creek and its tri­ butaries is semiarid, a climatic condition which results In rather special types of geologic activity along the modern drainage lines* Heavy localized precipitation and torrential runoff are character­ istic of this climatic regime. The origin of th© piedmont flats, to be suggested later in this paper, Is related to the geologic processes which prevail in the valley bottoms. The following clII matic data furnish a background for an understanding Of these pro­ cesses* The mean annual rainfall varies from 12 inches at Pueblo, in the lower piedmont (Figure 1), to 14 inches at Colorado Springs, in the upper piedmont near the mountain base. A prominent feature of this precipitation is th© concentration of the greater amount in th© warmer part o f th© year, more than 75 per cent f a llin g be­ tween April 1 and September 1. Meteorological data from three wea­ ther stations located within or near the borders of th© area studied are tabulated below; Average Monthly Precipitation In Inches fV. S. Weather Bureau) Month Pueblo Penrose 0dorado Springs 1869-1930 1924-1930 1871-1930 January 0*3 0.24 0.22 February 0.6 0.42 0.36 March 0 .7 0.84 0.72 A pril 1.6 0.61 1.57 May 1.6 1.76 2.21 June 1 .3 0*95 1.82 July 2.0 1.66 2.94 August 1.8 2.28 2.29 September 0 .9 0.95 1.08 October 0-54 November 0.82 December 0.39 0 inches 1X746 Inches inches 50 n

An important precipitation characteristic is high rain­ fa ll intensity during summer thundershowers that affect only lo­ calized areas. Local records commonly show that the rainfall is of such concentrated nature as to result in disastrous floods. The Colorado Springs Gazette (June 27* 1384) described one such occurrence as follows: "There had been several thundershowers and th© creeka were somewhat swollen, ..... But about 4 o’clock .... a heavy cloud came up over Gheyann© Mountain .....sundown, . . . . r a i n and h a il began to f a l l in tremsrndous t o r r e n t s ...* , the whole surface of the country was flooded as though it were a vast lake, and in some of the ravines the water rushed along in torrents 20 to 30 feet deep. The storm continued in full violence until about 9 o’clock. The area of the storm was confined within.*., a radius of 3 or 4 miles." In another article from the same paper (August 1, 1885) there is a notation of a storm which flooded Monument Greek, but resulted in very little effect in Fountain Greek to which this stream is tributary. Another storm, extending over an area from Colorado Springs southward to a point beyond the Town of Fountain on May 27, 1902, flooded Fountain Greek and caused that stream to excav­ ate its channel 30 feet in places. The precipitation causing this flood totaled 3.02 inches, from a number of local thundershowers. The localized torrential runoff from these storms is a capable scouring agent in the channels effected. Humorous refer­ ences of scouring activity of varying magnitude are available in the literature. The flood of May 30, 1935 perhaps best typifies this scouring action* In a series of local thundershowers which occurred all over the Fountain Greek basin, ranging from three to six inches in magnitude, the various tributaries were swollen by floods. The channel of Fountain Greek was scoured to bedrock to 52 a depth of three to nine feet below the channel alluvium at this time. A securing of similar magnitude is recorded for the flood of

la the Mountain Canyons The drainage lin e s of the Front Rang® occupy deep, steep** walled gullies and canyons developed in th© igneous and metam- orphic rocks o f the pr ©-Cambrian complex. The v a lle y bottoms are floored with bedrock, covered in some portions with a re-* latively thin veneer of alluvial material. In several of the larger canyons flat-floored, alluvium-covered basins break the monotony of th© normal canyon. Thee© basins are invariably lo­ cated in parts of the canyons where several tributary streams join the main drainage channel. The alluvium covering the bedrock of the basin floor is coarse-text or ed, most of th© larger frag­ ments being rounded. Lithologlcally, this is made up of all the rock types which outcrop in th© drainage area above# A typical basin of this type, located in upper Red Creek Canyon in the southwest part of the quadrangle, was mapped in detail by the author. This basin is described below with reference to the map o f Figure 19* The present stream channel occupies a variable position on th© basin floor, in some places impinging against the canyon wall (Figure 19, (01) and Figure 17)), in others in some position out in the basin (Figure 19, (Ob)), The depth of this channel varies from two to six feet, here and there exposing bedrock. Additional dissection of th© basin flat is provided by older channels, now abandoned, which also vary up to six feet In depth. 3ome of thea© appear fresh with steep, unmodified banka (Figure 19, (Au)), whereas others are shallower and present a more modi-

53 54 tied appearance (Figure 19, (Am) and Figure IS ). The channel pattern of th® basin floor Is interlacing, divergences occurr­ ing both from the main channel (Figure 19, (Cd)) and from other old channels (Figure 19., (M)}* The smoothness of the valley flat is diversified by allu­ vial fans of varying siae, rock trains, and boulder plugs. Fans have been deposited both by the main stream and tributary channels* Most main-stream fans have apices that head in a constricted can­ yon at the upper end of the basin (Figure 19, (Fa))# Large parts of fans have been removed by dissection, leav­ ing remnants in Interchannel areas, Much fan dissection has been accomplished by th© main streams of th© valley flats, as is demon­ strated by sears in dissected fan escarpments and old channels along their bases, but som® fans have been dissected by the tribu­ tary streams. Th© cutting exposes the underlying bedrock of th© basin floor in places. Fan sequences occur below the mouths of larger tributary gullies (Figure 19, (Fo) and (Fy))* The highest of these sequence remnants present steep, 10- to 15-foot alluvial escarpments toward the basin center. Tributary fans are most num­ erous along the basin walls farthest removed from th© modern channel. The rook trains are irregular elongate ridges of coarse, bouldefly material, th© majority of which are aligned along th© interlacing channels of th© basin floor (Figure 19). These ridges, somewhat similar in appearanc© to natural levees, project from a few inches to several feet above th© alluvial flat* 55

Figure 17 1 Forties of the basin of upper Red Creek Canyon mapped in Figure 19* Here the modern channel Impinges against the granitic rocks of the canyon wall. Coarse debris in transit is visible in the right foreground. The broad alluvial flat of the valley floor is la the left of the view. Bedrock underlies the valley floor only a few feet below the alluvial material in this view.

Figure IBg 7iew northward In basin of upper Red Creek (mapped la Figure 19) showing the steep canyon walla (left of view) and the broad valley flat modified by unoccupied stream channels (left foreground). A rock train extends away 56

from the observer in the right of the view. The modern channel i s located to the rig h t of the area shown in t h is view* The basin walls consist of steeply-sloping exposures of mountaln-compex bedrock. These exhibit a marked constancy of angle of slope. Bedroek surfaces are relatively clean, being covered by only small quantities of angular rock fragments in transit. A sharp angle ordinarily marks the break between sidewall and basin floor. In places the contrast is emphasised by the presence of an old stream channel or stream scar. Talus and fan accumulations, however, obscure the angle between basin walls and basin floors at many places.

In the Piedmont The valley bottoms along and beyond the mountain front are flat and veneered with a blanket of coarse fanglomerate up to 25 feet thick which shows downvalley gradation to finer sizes. The present channel occupies a variable position with respect to valley sides. In general, the piedmont valleys of the Lower Piedmont Area have the downvalley-flarlng characteristic (Figure 3)• The upper piedmont portion of one of these valleys, Hock Creek valley, has been studied in detail and mapped by the author. The follow­ ing description is keyed to the map of Figure 20 which shows the features present. The modern channel is variable in position and is incised to depths of from two to eight feet below the alluvial surface (Figure 20, (01) and (C v)), Numerous unoocupied channels form an interlacing system on the valley flat (Figure 20, (Cd) and (Ad)). 57

These channels are comparable la every detail to those la the canyon basin described above. Many show evidence of recent use (Figure 20, (An)), whereas others have been Idle long enough to display considerable modification (Figure 20, (Am)). Bedrock is exposed in a number of places In these channels, its occurrences being present in all portions of the valley, and at approximately the same depth below the alluvial surface. The bedrock surface below the alluvial fill appears to be relatively flat. Bock trains, boulder plugs, and alluvial fans occur in this valley flat with relationships and characteristics similar to those already described for mountain basins. Because of the more open character o f Hock Greek v a lle y , however, the fans are of greater size (Figure 20, (T)), and the boulder trains more con­ tinuous than in the mountain canyon basins, Several tributary fans form plugs across abandoned channels of the valley bottom (Figure 20, (Fp)), The curved arrow symbol in Figure 20 indicates the ap~ proximate position of the sediment-granite contact where It cros­ ses the valley of Bock Greek, This contact locally follows a thrust fault, with the west side composed of the granite of the upthrown block and the east side consisting of downthrows Pierre shale (Figure 3). The granite valley walls upstream from this contact drop precipitously to the valley flat, meeting it In a sharp angle in most localities. Farther downvalley, in the sedimentary section east of the fault, the sidewalls are also steep, but are lower, Fanglom- erates of the Interstream piedmont flats commonly cap valley walls. 5 B tinder the alluvium are exposures of Pierre shale. The flights of terraees along valley sides in the piedmont have already been noted. Figure 20 deplete two such terrace levels* Above them is an upslope extension of the lowest Low Level Group piedmont flat on the south side of the valley of EoeJe Creek, The two lower terraees are separated by a five foot vertloal interval* They merge ,both with each other and the present valley bottom,up- stream* The higher level of the two stands about 15 feet above the valley bottom but this interval decreases upstream* These terraces are similar in all respects to the present stream flat, containing all of the described features thereof* (? ) Tributary Canyon o) Old Fan FIGURE 19 (Ci) Main Channel against Valley Wall Young Fan

(Cb) Main Channel in Basin (Au) Unmodified Abandoned Channel

(An) Modified Abandoned Channel

Divergence Main Channel (Ad) Divergence Abandoned Channel

a) Old Fan Apex @ Fan Plug in. Channel

/§ Present Channel Bottom

• •^°2?OOO®060i>oo^ Old Valley Flat

•.V.IiW pfiS* '/ Old T ributa ry Alluvial Fans r~v » \ \ \ \ \ -^| Young T ributary Alluvial Fans

Main Valley Alluvial Fan

eoooooooooooo R g ^ J | - a j n ooooooo Boulder Plug

xez Log Jam Scour Pool Present Channel ■ Recently Abandoned Channel valley wideninc =REd creek canyon — Old Channel Scar Modern Tributary Channel © © ® © ® © < s > © Channel FanPlug inChannel TributaryStream Unmodif Abandonedied an Channel DiversionMa|n Channel oiid Abandoned Modified Abandoned Channel Diversion an ChannelMainimpingement MainChannel inValley

VALLEY WIDENING-MOUTH OF CANYONROCK CREEKWIDENING-MOUTH © IUE 20 FIGURE O | OldestFlat Valley 0| ‘ ° ■ O . •;-i Old Channel Bottoms Channel Old •;-i LowLevelGroup Tributary Alluvial FansTributary LowestLevel Surface Present Channel Bottom

oo ° o oo0oa ole Plugs Boulder o - o on l Channel Sear Old ~ Rock Trains Rock ei n- ranlta ent-G Sedim Approximate Contact Contact Approximate (stiannelYoungest Abandoned Flat Valley Prosint ChannelProsint S C A L E I N F E E T 0

100

MECHANICS OF VALLEY WIDENING

Climatic Factors In a semiarid climate where precipitation yields Intense, localised runoff of torrential nature which is usually confined to a limited portion of one drainage area, large quantities of rock debris are shifted for relatively short distances# Though the runoff does not have the same intensity during each torrent­ ial flood, over long periods of time a certain mean intensity p r e v a ils . The rate of weathering on exposed su rfaces of homogen­ eous rock is rather constant, providing the means for removal of the weathered debris from the exposure exists* The amount of debris supplied by weathering is comparatively uniform. Thus weathering and ero sio n a l a c t iv it y in t h is region have somewhat uniform capabilities.

Retreat of Slopes A number of students of arid and semiarid land forms con­ cur in the belief that elopes weather back at a constant rate and at a relatively constant angle of slope where similar condi­ tions of climate, llthology, and rock structure prevail. Included among these are Lawson (1915)» Bryan (1935*36), Rich (1935)» F ield (1935), and G illu ly (1936). Bryan concluded that the angle of mountain slope Is af­ fected by the character of the rock and the climate, noting that weathering controlled by widely-spaced joints yields steep slopes in massive rocks, whereas more closely-spaced systems of joints yield lower slope angles. It is possible that localised joint sys-

59 60 terns in the granite rocks of the mountains are responsible for the development of canyon basins in the Colorado Springs region* Held noted that many factors control the retreat of slopes, including the length of the elope, the size and shape of the weathered rook fragments, and their rate of loosening. He con­ cluded that r ill wash on the rook surface and gravity are the im­ portant factors in the removal of material from the base of the slo p e. Gilluly agrees with Bryan and Lawson that there is a cor­ relation between the average size of rook fragments weathering from the slop e and the angle of slope* Rich observed that slopes in semiarid climates w ill retreat at a constant angle as long as the weathered material being sup­ plied from higher up on the slope is being removed from the base by running water* Accumulation of debris at the base, however, w ill cause at least a temporary halt In the escarpment retreat locally* The sidewalls of the stream valleys in the Colorado Springs region exhibit a marked constancy of slope angle* The rate of re­ treat of these slopes, however, varies from place to place. The more rapid retreat of the canyon basin walls, as compared to the narrower canyon segments, may be related to a more favorable ar­ rangement of secondary rock structures In the former localities* An additional factor may be the greater number of tributary streams which enter the basin area, the location of which might also be controlled by rock structure. A more important contrast is the more rapid retreat of slop es in the sedimentary rocks of the piedmont as compared with the granitic rooks of the mountain mass. The piedmont valleys are 61 much wider than their upstream canyon portions. Variations in valley width also occur in the piedmont, being related in every case to the bedrock forming the valley sides. Valley segments are, in general, much narrower in the more resistant sediments in the Southwest and Manitou Imbayment areas w est o f the Dakota rid g e, than in the lower Piedmont Area underlain by the less resistant sediments* Valley widening is accomplished in this region by a com­ bination of the following factors. Spalls weathered from valley walls, moved by water and gravity, collect at the bases of the slopes. Periodic flushing along channels keeps the lower portion of valley walls free of debris which would otherwise prevent uni-* form weathering and retreat of slopes. Torrential runoff provides the means for this removal of debris. Tributary streams, particular­ ly in(the more easily eroded sediments of the piedmont, are an ad­ ditional aid to sidewall retreat* These work headward into the sidewall slopes, wearing the latter back and moving the eroded material into the valley flat where it may be removed by main channel activity*

Channel Shifting The abandoned channels characteristic of a valley flat mark positions of the main channel at various times during the valley widening process (Figures 19 and 20, (Au) and (Am)). These shifts in positions of the main channel are the result of alluviation of the valley floor during torrential floods. Such aggradational activity includes the development of rock trains, boulder plugs and asso cia ted lo g Jams, and a llu v ia l fan s. 62

Tolman (1905-06) used the terms "arroyo tr a in ” and "rook train” to describe extensive radial deposits of boul&ery material on the bajada surfaces of the Southwest, concluding that these features are stream deposits* Matthes (1930), observing similar features in the Tosemite region, stated that they are not natural levees farmed at times of overflow but represent material thrown bodily out of the torrent channel. Matthes described fragments in the rock trains which had much greater sine than any existing in the area being considered here. This would not appear to be a diagnostic difference, however. It is the present writer’s ©pin* ion that these may be considered natural levees of coarse material formed by the accumulation o f bedload fragments which managed to escape from the main threads of flood current during torrential runoff. The term "rock train" is appropriate in describing them, and is inoffensive because it carries no implication of origin* The reek trains act as confining agents for runoff, but they also act in the opposite sense, in preventing new courses of floodwater from entering old, abandoned channel segments• Breach­ ing or overtopping of a rock train during an excessive flood al­ lows the runoff water to escape from regular courses into new paths across valley flats. Lower segments of channels may be abandoned when euoh diversions occur. The upper end of an abandoned channel is rapidly alluvlated. Slack water favors alluviatlon after the main flow proceeds down a new course* Alluvial plugs toward heads, and rock trains along sides of abandoned channels, render probabi­ litie s remote that a channel segment, once abandoned, is likely to be re-occupied. Diverted streams assume courses determined largely by rock-traln patterns. Diverted courses run between rook 63 trains, or between these low ridges and the valley walls, flood runoff is not likely to follow the same course for an appreciable number of years, Diversions shift channels so effectively that all parts of the valley floor are subject to being included as channel areas at some time or other, Boulder plugs and associated log jams are important agents for shifting channels, as has been noted in the flood deposits of Arroyo Seco Canyon, los Angeles County, California, by Krum- beia (19A2), In an earlier paper (1940, p.645) this author descr­ ibed the manner in which channel s h iftin g occurs due to the pres­ ence of such deposits as followst "The upbuilding of the beds forced the stream to cut laterally around the jam unless the jam itself was par­ tially undermined by the clear water pouring over its e d g e . In either case a channel lower than the surface of the deposit was soon developed,w Similar conditions exist in the Colorado Springs region. An abundance of such diversions have been caused by channel plugs and a sso cia ted lo g jams (Figures 19 and SO), The main valley fans favor channel shifting because sur­ face runoff can readily assume any radial downslope direction. This commonly leads to impingement of flood channels against ei­ ther valley wall below or marginal to the fan. Fan deposits cover old channels thus hiding the complexities of channel patterns. An actively growing fan tends to shunt earlier drainage aside. Such is the case at the north end of the Red Creek Basin shown in Figure 19, Here a large valley fan plugged an old channel a- long the east wall (Fp), and a new course was adopted elsewhere. Tributary fans tend to force main channels tcward the op­ posite valley walls. Their development favors slack water upstream 64 along main channels and hence the alluviation of valley floors above them. Blocked channels may be forced to cut back into allu­ vial material and talus along the valley wall at elevations well above those of channel bottoms* In this way are probably develop­ ed a number of the streamcut escarpments along the edges of high­ er tributary fane and valley sides (Figure 19, (Fo) and (Fy})» It may be concluded that alluvial damming by such obsta­ cles as fans, rock trains, and boulder plugs causes the runoff to shift its locus of activity to various parts of the valley flat* This shifting appears to play an important part in the general process of valley widening.

Bedrock Erosion Floods are effective agents of erosion* Their waters pick up loose debris and scour channel sides and floors, even after exposing solid bedrock* But floods are also effective a- gents o f a llu v ia tio n * Krumbein (1942, p .1400), in a summary of the causes of floodwater deposition in the Arroyo Seco, Califor­ nia, notes that flood deposits are caused by several factors in­ cluding: "abrupt decrease in gradient as at tributary mouths; abrupt velocity decrease associated with locking logs and boulders; v e lo c ity decrease caused by water p r o file adjustments at constrictions; and perhaps abrupt veloc­ ity decrease caused by hydraulic jumps." All of these factors may operate together or singly at any time during the flood, causing local alluviation and channel shifting. Velocity decrease, occasioned by the movement of floodwaters from constrictions into broader portions of the valley, occurs in the canyon basins. The valley fan at the north end of the 65

Red Creek Canyon Basin {Figure 19) i s a floodwater deposits mad© by the runoff as it rtspreads-outn upon leaving the narrower can­ yon portion above. A further contributing factor to such alluvia­ tion activity is the network of abandoned stream channels in these valley flats. These tend to dissipate the energy of the floodwaters by dividing them into component parts, thereby reducing transpor­ tations! ability and causing deposition. Thus, as the floodwaters move down a valley, scouring and alluviation occur simultaneously. The creation of alluvial obstacles shifts the locus of scour about on the valley floor to the most advantageous positions for contin­ ued flo w . K essili (1911) points out that even a stream loaded to capacity w ill continue to attack the stream bed by the impact of material carried in the bedload. Thus, even when the flood Is heavily charged with debris, vertical corrosion should be favored# Kessili notes further that during the last stages of flood the torrent changes to a "brook" and, despite decreased volume, cuts a trench into the flood deposits* Such cutting, if extensive enough to scour through the flood deposit, w ill reach the underlying rock surface. Shifting channels that are capable of cutting as deep as bedrock are capable of scouring any part of the valley floor, eventually tending to corrade the bedrock surface to ap­ proximate flatness.

D u e to the Incomplete nature of accounts of local flood scour in the Colorado Springs region, it is impossible at present to state an average figure for the effective depth of such action. Bailey (1931), however, in studies of flood activity in northern Utah, a region with climate similar to the one considered here, 66 o ffe r s the fo llo w in g data. Two flo o d s in Ford Canyon in 1923 and 1930 out a channel 40 feet deep in the fan of this creek at the canyon mouth. Parrish Creak in the same area during the 1930 flood cut down 70 feet in the canyon f ill and exposed stretches of bed- rook in the channel bottom. Woolley (1946), in detailed studies of flood activity in the west slope o f the Wasatch Range, Utah, found that Eanab Canyon was visited by torrential floods each summer from 1882 to 1886. In that period the channel depth of that stream was increased by 50 f e e t or more in places*

frankenfield (1923, F-4 2 1 ), made observations of flood ac­ tiv ity in Willard Canyon, tJtah and found that* "The stream channel was scoured to bedrock*...., the exposed surfaces showing much watermarking as if by previous floods Thus, in other regions affected by torrential runoff of localized nature scour has been shown to reach to considerable depth in the valley alluvium, exposing bedrock in places* The numerous abandoned stream channels, many of which expose bedrock in places in their bottoms, occurring all over the piedmont val­ ley flats of this region, suggest that the scouring ability of torrential runoff is sufficient to affect bedrock widely. Bryan (1940) described a process of channel shifting and scouring which he ealled "gully gravure," This process re­ quires porous debris which becomes impervious as it weathers, thereby increasing in ability to promote surface runoff. This material is gullied during torrential runoff which, of great enough intensity, may scour to bedrock. The new gully then fills with fresh alluvium which is pervious and inhibits runoff, 67 thus shifting the site of the subsequent gullying action to more decayed, more impervious debris adjacent to the newly filled chan­ nel. In this manner gullying shifts laterally and parallel incision to bedrock to about the same depth may occur each time, providing the alluvial debris is not too great in thickness for effective scour to reach the underlying bedrock. Inequalities in the bedrock surface may be reduced in this manner. Bryan applies this process te the retreat of slopes. According to him the requirements are that there be a supply of rock fragmenta from higher areas which w ill be carried by storm runoff over a slope developed on material which weathers into a clayey mass. These special conditions are met In the broad valleys in the lower Piedmont Area, developed in Pierre shale. This material weathers to a clayey mass and there is a con­ tinual source of rock fragments from the fsnglomerate in the inter- stream piedmont surfaces which form the upper portions of the val­ ley walls. This may be one maimer la which valley walls retreat lo­ cally. Furthermore, gully gravure, as described by Bryan, may aid in the development of the bedrock flat in portions of the piedmont ▼alleys which are underlain by Pierre shale. relationship mrmm v a l o t vmmiwa m > yalict w ianM

The streams of the Golcredo 3prings region are actively degrading their valleys, a fact which is supported by the deep, narrow canyon segments incised in the bedrock of the mountain mass; the steep stream gradients, ranging from 300 to 1300 feet per mile in the mountain portions; and the bedrock exposures a- long the valley sides and in the broad flats of the piedmont areas. In a degrading region such as this, in which the streams are ac­ tively deepening their valleys, the alluvium of the valley bottom is being continuously removed at a rate about equal to its re­ plenishment by weathering and erhsion. In order that degradation be continuous, the thickness of the valley flat alluvium must be slightly lose than the vertical distance that the average flood is capable of scouring. If the average depth of scour is somewhat less than the depth of alluvium, the valley cannot be degraded because the underlying bedrock is not within the scope of stream erosion. On the other hand, if the average depth of scour greatly exceeds the alluvial thickness, the excess of energy of flood run­ off w ill be capable of keeping the valley swept clean of alluvial debris, furthermore, the flood channels would b© deeply incised In the bedrock floor. Hone of these conditions obtain. The channel depths in the majority of these valley flat® reveal bedrock at many localities in their extent, but are not incised to great depth be­ low the bedrock surface. Allowing then that the bedrock of the valley bottom lies just within the scouring scope of the average flood, there i® a 69 means of producing a relatively f l a t bedrock floor in portions of these valleys where conditions are such th at the sidew alls w ill retreat. Continued shifting of the locus of scourover the valley bottom effectively corrades the underlying bedrock at a depth a- bout equal to the alluvial thickness. It is quite apparent th a t, though an average depth of scour w ill prevail under uniform cli­ matic conditions over a long period of time, individual floods w ill vary somewhat in intensity, some greater and some le s s than the mean. These variations in intensity of runoff should be .indi­ cated by minor protuberances above and minor channel irregularities below the bedrock surface* The numerous bedrock axpOburea in the irregularly-trending channels of the valley bottoms favor th is view. In places the bedrock is incised to a few feet below i t s upper surface, whereas in other localities it is covered by sever­ al feet of alluvial debris. Channel shifting, by which the valley walls are periodi­ cally freed of the cloaking effect of debri3 accumulations along their base, is also a local means of la te r a l corrasion. This occurs wherever the active flood channel impinges against the sidewalls. Valley deepening and valley widening are occurring sim ult­ aneously, as shown by the r e la t iv e ly smooth stream profile which extends without major irregularity through both broad and narrow valley segments. Locally, however, the retreat of valley walls is a more rapid process than valley deepening, so that canyon basins and broad piedmont valley flats are being developed. In this writer1® opinion, the valley bottoms of the region are being lowered uniformly but slowly, while at the earn© time lo c a l widening is occurring by channel shifting and sidewall retreat. 70

The downeuttlng is not accomplished by continuous scour, but rather by the lateral shifting of the locus of corrasion by sporadic flood runoff* This results in a uniform lowering of the bedrock floor in all portions of the valley bottom* Beep incision along any part­ icular thread of flow cannot occur unless som means of permanently confining the channel is developed* BEVELUPMSNT OF PUMQOT FLATS m> TERRACES

Uniform mountain uplift, accompanied by slight fluctuations in climate, are factors responsible for the development of the numerous stream terraces and the major broad piedmont interstream surfaces* The processes which developed these various surfaces are occurring today in the piedmont valleys and in restricted port­ ions of the canyon segments of the modern streams* Talley widening under the present semiarid climatic regime is at an optimum* The various levels of the piedmont also represent times when valley widening predominated* The vertical intervals between the terraces along the valley sides and between the piedmont levels, in this writerfs opinion, represent periods during which valley deepening was the major activity along the drainage lines* The alternation between predominance of valley widening and valley deepening is thought to be controlled by slight fluctuations in the average annual precipitation over long periods of time, as suggested in the following discussion* Permanent confinement of stream channels should occur in this region if the climate were humid enough to require permanent flow* Such climatic change would increase the vegetative cover, thereby increasing the activity of organic acids. This would accel­ erate the formation of deep soils, which would effectively halt the retreat of slopes* The amount of moving debris would decrease on the more stable slopes. Weathered material reaching the valley bottom would be broken into relatively fin© sizes which would be removed readily by the increased runoff* Lack of reasons for alluv­ ial damming would inhibit channel shifting* streams would expend

71 72 energy c u ttin g downward* A climatic change to more arid conditions would have an opposite effect* Dooreased runoff would be incapable of removing the coarser debris supplied by predominantly physical weathering processes* This debris, in the relative absence of organic acids, would tend to remain fresh and intact* The valleys would choke up with this coarse material* Sidewall retreat would be arrested by the cloaking effect of debris accumulations at their bases* Valley widening and valley deepening would be less likely than fillin g with alluvial debris* Thus, the cycle of climatic fluctuation from semiarid, as a t p resen t, to a s lig h t ly more humid should y ie ld more rapid vertical incision, whereas a shift back to semiarid w ill result in the predominance of valley widening* Throughout this cycle, however, the valleys are continuously deepened, at a more rapid rate when the runoff is greater and less rapidly during the semiarid periods where the runoff is sporadic* The control is climatic whereas the cause is continuous and uniform uplift of the mountain mass, The alluvium over broad stretches of these piedmont sur­ faces completely masks the underlying bedrock, preventing careful investigation of the characteristics of the latter. In all expos­ ures of the fanglomerate-bedrock contact along the dissected edges of the surfaces this contact was traced and mapped. The depth and coarseness of the alluvium in undissected portions of the surfaces militated against the us© of manual bore-hoi® technique for pene­ tration to the underlying bedrock* Mechanical boring tools were not available for this study* It la possible that major irregularities, undetectable by 73 ordinary field methods, may he present in the bedrock levels of these surfaces. Beep channels in the bedrock surface would cast serious doubt on the origin of the piedmont interstream flats pos­ tulated herein. An alternative hypothesis is therefore briefly outlined, the fundamental concepts of which may b© used to explain the piedmont flats should major irregularities be discovered in these bedrock erosion surfaces. These surfaces may result from processes similar to those suggested by Rich (1935), who concluded that multiples of alluvium- capped levels may develop in a piedmont floored with weak rock, adjacent to a mountain escarpment consisting of resistant rock, in the following manner, Streams issuing from such a mountain front deposit coarse materials, eroded from the mountain mass, on the weaker rocks of the piedmont. This deposit effectively blankets fan-shaped areas around the canyon mouths, forming a resistant cap which prevents lowering of the underlying rock by weathering and erosion. Adjacent areas, however, not affected by such deposits, are weathered and lowered by erosion* Piedmont- born streams, not burdened by the coarse mountain debris which is being carried by the mountain-born streams, extend their courses headward, dissecting the marginal portions of the higher, alluvium- capped areas around the canyon mouths..Eventually, one such stream may succeed in diverting the mountain-born drainage from its higher channel* Thus, a new site for deposition w ill be established along a new drainage line, and at a lower elevation. This locus of deposition w ill then form a lower, perhaps steeper, alluvium- capped surface resistant to the agencies of weathering and erosion in the piedmont. This cycle may be repeated many times and w ill 74 result in the development ©f a multiple of alluvium-capped levels ia the piedmont along the mountain base* Such an arrangement may occur ia step-like fashion, roughly paralleling the mountain front, or may occur in tandem fashion outward from the mountain base. An additional possibility of similar nature might result if the locus ©f deposition is shifted along the mountain-born chan* nel outward from the mountain base* In either ease, however, whether it be shifted to the flank or distal margins of the fan, the lower headward-eroding piedmont stream channels should be filled with alluvial material as the locus of deposition encroaches on them. Thus, deep channel irregularities should exist in the bedrock sur- face underlying the alluvial material in such localities* This hypothesis does not require climatic fluctuations for development of a multiple of levels in the piedmont. It fits well the postulate of continuous mountain uplift* However, it does re­ quire major irregularities in the bedrock surfaces underlying the interstream flats, irregularities which are not in evidence in dissected portions of the levels examined by this writer. Further* more, it does not adequately explain the presence of a relatively plane bedrock level underlying the alluvium of these surfaces* However, it is possible that the alluvium of more centrally located portions of the surfaces masks such irregularities* Consideration is now being given the possibility of obtaining evidence of the character of completely covered bedrock surfaces by seismic means. mu&immxp w m m t® Dakota kidgi AND m i SUBFACIS

Elevation, trend, and extent of preservation of ear tala of the surfaces are related to the presence or absence of the Dakota ridge* This relationship is best expressed in the Deadman Canyon section of the Southwest Area. Here the various levels are well enough preserved to reveal the control exerted by this rock unit*

E levation In general, the piedmont surfaces are at higher elevations west of the Dakota ridge (Intermediate Croup) than equivalent levels east of this feature (Low Level Croup). The Little Turkey Creek su rface, numbered (5c) in Figure 21, has a mountain base elevation of 6,870 feet (Plate 3, (5)). This level is not present between the mountain front and the Dakota ridge in the L ittle Bear-Little Fountain Creek drainage area to the north. It does occur, however, as a bread interstream flat between Little Fountain and Hock creeks at an elevation of 6,400 feet east of the Dakota ridge, described earlier in this paper as the lowest level of the Low Level Croup surfaces. Despite the difference in elevation of these two surfaces of the Intermediate and Low Level Groups, they were developed at the same time. The lower elevations of Low Level Group surfaces east of the Dakota ridge, as compared with the higher elevations of the Intermediate Group west of this ridge, is the result of more rapid downeutting by the streams in the less resistant rooks (Pierre shale) in the former locality. Another factor aiding more rapid downeutting in this area ia the shorter extent of the drain­ age lines from mountain base to junction with the master piedmont

75 76 drainage to the east (Fountain Creek), as compared with the greater extent required for more southerly streams flowing within the con-4 fines of the Dakota ridge to reach the master drainage to the south (Arkansas River)* The more northerly streams developed steeper grad­ ients beQ&use of their shorter reach, a profile condition resulting in more rapid downeutting* It should be noted here that considerable difference ia elevation exists between the mountain base portions of the present streams north of the Little Bear-Little Turkey creek drainage di­ vide, as compared to streams to the south* In-general those stre­ ams to the north have lower mountain base elevations than those to the south* For example, Little Turkey Creek is at 6,075 feet where­ as L ittle Bear Creek, occupying the adjacent major mountain canyon, is at 6,550 feat {Plate 3, (A) and (0))* The lower elevation of the L ittle Bear Creek drainage, even though developed in the same rooks as Little Turkey Creek in this locality, can be attributed to deep­ er incision in the weaker rocks to the east of the Dakota ridge and the headward migration of this incision into the more resis­ tant rocks to the west. Little Bear Creek is the only stream north of the L ittle Bear Creek-Little Turkey Creek divide which has any appreciable portion of its course in rock® other than Pierre shale, one exception being that portion of Fountain Creek west of the Da­ kota ridge in the Manitou Embayment Area.

Trend The control exerted by the Dakota ridg© on the trend of the piedmont surfaces is best exemplified by the Little Turkey Creek surface along the northeast side of that stream (Figure 21, ( 5c) and (5b)). This level trends southeast for approximately one 77 mile toward the Dakota ridge and then ia abruptly turned southward along the western base of that feature* Scattered remnants of the former extent of this surface to the south bear out this observa­ tion (Figure 2 1 , {$«)» (5h), and (Sl)h The stream responsible for the development of this level, little Turkey Creek, was controlled in tread and diverted southward by this ridge* Other instances of similar control on the trend of surfaces by topographic obstacles occur elsewhere in the piedmont (See Popes Bluff® and the Dakota Ridge in the northern portion of the Colorado Springs region as shown in P la te 1 ),

Extent of Preservation The heavily*inked portion of the Dakota ridge in Figure ill (&•»?), indicates an area which has not been lowered by erosion to the level of the bedrock under the piedmont surfaces* It projected above the Deadman Canyon Surface throughout the period of i t s dev­ elopment, and has remained a western* wall-like barrier ever since* This b arrier d iv e r ts streams from the Deadman Canyon Surface, and causes major drainage incisions and concentrated erosion in areas both to the northeast and west* little Bear and Little Turkey creeks have been d iverted in th is manner (P late 1)« IROSMAL HISTORY OF THB README CAOTOH AREA

(Figure 2 1 ) The Deadman Canyon Surface is the oldest piedmont flat in the Colorado Springs region* Its two highest levels are rem­ nants of broad, fan-shaped alluvial surfaces which, during maxi­ mum development, coalesced to form the ancient floor of the pied­ mont* Bach was developed as an ancestral valley which was widened laterally in bedrock by sidewall retreat and the shifting and scouring action of torrential runoff. The occurrence of equivalent levels throughout the Colorado Springs quadrangle (Figure 3), is evidence for the once widespread extent of this highest and oldest surface* The northern portion o f the Deadman Canyon Surface (Figure 2 1 , (1 )} was developed along an ancestral drainage which Issued from the mountain front in the L ittle Rear-Little Fountain creek area. This interpretation is supported by the presence of rhyolite fragments in the alluvium of this level and by the upstream con­ vergence of abandoned stream channels on this portion of the moun­ tain front. The Dakota ridge (Figure 21, (3C-T)) projected above this surface at all times* The southern portion of the Deadman Canyon Surface (Fig­ ure 2 1 , (2a) and (2b) is a remnant of a similar valley flat along the ancestral L ittle Turkey-Turkey creek drainage system* Levels (1) and (2 ) coalesced downstream east of the Dakota ridge to form one broad surface underlying the floor of the piedmont to the east. West of this ridge (X-Y), however, a drainage divide separated the two* The almost complete absence of rhyolite in the alluvium of the 78 79

southern portion attests to this, indicating that the ancestral L ittle Turkey Greek drainage did have access to the outcrop of this rock (le). A windgap in the Dakota ridge at (p), at 6,650 feet in elevation, preserves on© small segment of one of the old L ittle Turkey Creek courses through this ridge* Mountain spur re­ presentatives of this valley flat occur between the canyons of L ittle Turkey and Turkey creeks in the upper piedmont about midway on this divide (2g), Additional remnants ar© present along the south­ west side of Turkey Creek ((2f), (2e), (2d), (2c)), extending the old Turkey Greek flat across the outcrop of Dakota (2©)* The L ittle Turkey-Turkey Creek flat beveled the Dakota for a considerable dis­ tance south of (Y), Southward along the east limb of the Red Creek Anticline (Plate 1), however the Dakota stood as a bordering ridge. The widespread extent of the combined High Level Group of surfaces is indicated by their occurrence 20 or more mile© to the southeast, near the Fountain Creek-Arkansas River junction (Figure 1 ), where they stand 200 feet above the present valley flats (Gilbert, 1897), Doubtless, many streams other than those included within the lim its of this study contributed to the formation of this ancient floor of the piedmont in areas far removed from the Colorado Springs region. The alluvial thickness in the northern and southern portions of the Deadman Canyon Surface, 100 and 40 r e sp e c tiv e ly , requires a depth of scour to the underlying bedrock somewhat in excess of that occurring along the present drainage. However, data In the literature describing stream scour in other comparable areas sug­ gest that even a depth of scour of 100 foet i© not an unreasonable postulate (Bailey, 1934)* Furthermore, the roughly planate character 80 of the underlying bedrock surface, and the presence of waterworn alluvium directly overlying that surface, are indications that it was developed by running water. The distribution of these excessive alluvial sections is such as to suggest that they are restricted to places where steep-gradient streams of the mountains encounter** ed reduced gradients below the mountain front. The alluvial depos­ its are lenses, growing thinner both in upslope and downslope di­ rections, The fact that the deposits have a semblance of bedding throughout (Figure 6 ) indicates gradual accretion rather than a torrential outpouring of debris during on© short episode* No "valley choking effect” of a more arid climate appears to be indicated. The alluvial debris of these thicker sections was derived from the crystalline mountain mass and had to be transported by water to its present position in the upper piedmont, No evidence of thick alluvial sections exists upslope from these maximum thicknesses. On the contrary, thinning occurs in that direction. If greater aridity had once been present it might be expected to affeot the entire region, so that thick alluvial sections should have developed regionally* It has been suggested that a possible relationship may exist between glaciation in the higher mountains and alluviation in the piedmont. Though th is p o s s ib ilit y has not been in vestigated with care, it seems likely that changes favorable or adverse to glaciation correlate with decreasing or Increasing aridity in the piedmont* During the late stages of alluviation of the oldest pied­ mont flats, the runoff shifted about on the surface® to produce the braided channel patterns which are now preserved on some surfaces. 81

Eventually, however, perhaps as a result of particularly violent storm s5 or, as a result of climatic fluctuations to slightly more humid conditions, incision of the last occupied of these channels occurred* At the end of a short episode of downeutting, valley widening processes developed the lower, more restricted flats below the older levels of the High level Croup. An occurrence of this nature is represented by the lower level (Figure 21, (3a) and (Jb)) along the eastern side of the Dakota ridge ia the northern portion of the Deadman Canyon Surface* A similar episode occurred along the ancestral Turkey Creek drainage as Indicated by remnants at (Jo). Subsequent to the valley widening episode just not'#8 an­ other drainage incision occurred along the drainage west of the Da­ kota ridge. This was paralleled in time by the westward extension of a Fountain Creek tributary into the piedmont flat of the High Level Croup north of the present Deadman Canyon Surface. In the l a t ­ ter instance downeutting was greater than along the drainage lines west of the Dakota ridge. This may be attributed to the relative ease of erosion In the weak shale to the east, as compared to the more resistant rocks west of that ridge, Furthermore, the shorter reach and steeper gradient of this headward-working Fountain Creek tributary, as compared with the longer reach and more gentle grad­ ients of streams to the southwest, Increased the rate of downeutting along that stream. The growth of this ancient stream, along the ap­ proximate position of the present valley of Little Fountain Creek, eventually diverted the drainage from the lowest valley flats of the High Level Croup (3a), thus taking the L it t le B ea r-L ittle Foun­ tain Creek drainage to the northeast to Fountain Creek. Valley wid­ ening along this new drainage line, at approximately 300 fe e t lower ia elevation than the lowest Deadman Canyon Surface level, produced a piedmont flat in this locality that sloped northeast­ ward* This is the middle level of the low level Group of this study. The s c a r c ity of remnants of th is le v e l here makes aoourate recon­ struction impossible* However, small remnants containing rhyolite are preserved along the south edge of the piedmont flat between l i t t l e Fountain and Hock creeks (Figure SI, (4 b )), and upstream a- long l i t t l e Fountain Greek on the Timpas ridge (4 0 )* The presence of the rhyolite constituent demonstrates that the drainage on this surface had access to the area of outcrop of this rook west of the Dakota ridge (le). The accompanying downeutting along the drainage west of the Dakota ridge resulted In valley flat development of unknown lateral extent in that locality* Only small remnants of one of these levels are present just south of Little Turkey Greek Canyon (figure 21, (4a)), the highest level of the Intermediate Group, the slope in this instance being northeast* Following this episode, downeutting again became predomi­ nant and L ittle Turkey Creek extended its drainage basin northward to include a portion of the area of rhyolite outcrop (le). The al­ luvium of the next lower piedmont flat west of the Dakota ridge, the middle level of the Intermediate Group, contains rhyolite frag­ ments* The distribution of the rhyolite in remnants of this level makes a restoration of the drainage net of that time possible. The soutlbHsloping surface on the Fountain ridge in Deadman Canyon (5a), the downslope portion of the large remnant of the same level to the southeast ((5b) and (5d)), and small south-sloping surfaces of the level farther downstream along Little Turkey Greek ((5e), (5h), 83

(51), (55)) contain this rock type. On th© other hand, the higher east- and northeast*eloping portions of this level lack this mat- erial ((5o)» (5f)» (5g))« It is apparent from these data that the sain valley flat of the time sloped to the southeast along the west** ern base of the Dakota ridge (X-Y), with at least one tributary ▼alley flat extending to the northwest into the mountain front area of the rhyolite outcrop (le). Additional tributary flats extended west into the crystalline rock area, a ll of them merging downslope with the main valley flat, A similar level was present along Turkey Creek to the southwest (Figure 21, (53) and (5k)), It is quit© like­ ly that, except for small residuals of higher piedmont levels, a relatively broad coalescence of this surface existed between the mountain front and the Dakota ridge in this locality, A narrowing occurred through and beyond this ridge toward the southeast (south­ east from (B)), the valley flat through that area being restricted on the e a st by the higher piedmont f la t of th© Deadman Canyon Sur­ face and on the west by the Dakota ridge (Plate 1), Similar levels, considerably lower in elevation than those Just noted, were developed during the same Interval along th® Little Bear and Little Fountain Creek drainage lines, extending in fan- shape into the piedmont from the mouths of the canyons of these streamsv The coalescence of these valley flats downstream formed the broad piedmont surface preserved between Little Fountain and Rock creeks (Figure 21, (5a) aud (5n))s a remnant of th© lowest level of the Low Level Group, Farther downslope this surface mer­ ged with a similar level along Rock Greek (Plate 1), Following maximum development of these valley flats cam© an interval during which downeutting dominated over valley wideniiig, 84

Portions of the older valley flats were dissected and eventually, at the lower channel elevations, less extensive valley flats were developed. The most widespread of these west of th© Dakota ridge were along Turkey Greek (Figure 21, (6f), (6g), (6h), and (41)), and along tributaries of that stream entering it from th© north­ east t(6d) and (6©)). The same level along little Turkey Creek is represented by (6a), (6b), and (6c). This level is designated the lowest of the Intermediate Group in this paper. Rhyolite is scarce in remnants of this level along Little Turkey Creak, consisting of reworked material derived from higher, older alluvium rather than the deposit of a stream having access to the rhyolite outcrop at (le). By this time the headward portion of the Little Turkey Creek drainage had been diverted by the southward extension of th© Little Bear Creek drainage, an action Involving the southward migration of the drainage divide between these two streams. The lower elevation and steeper gradient of Little Bear Greek were responsible for its comparatively greater erosional ability. This drainage is still en­ croaching in th is manner on the L ittle Turkey Greek drainage. The equivalent of this valley flat level along Little Bear and Little Fountain creeks is the highest of the stream terraces along these streams (Figure 21, (6n), (6o), (6p), (6r), and (6s)). Remnants are also present in Deadman Ganyon ((6k) and (6m)). At maximum development this piedmont fla t formed the bottom of broad, northeast-flaring valleys in the Lower Piedmont Area to the north of the Deadman Canyon Surface, similar in a ll respects to th© modern valley bottoms of that area. This, and the successively lower ter­ races along these valleys, represent alternating episodes of valley widening, during which th© terrace levels were formed, and valley 85 deepening, during which th® terraces were Incised, the next lower of these stream terraces is designated by (7a) and (?c) in figure 21* The remnant marked (7b) i s a f l a t developed by a shorter trib u ­ tary to L ittle fountain Creek entering it from the south, fragments of two lower younger terraces ooour below the higher ones along this portion of the Little Bear-Little fountain Greek drainage, though these are not shown ia the figure, farther east several, additional, minor terrace levels Indicate local valley deepening and widening which did not extend far enough headward to be repre­ sented in this portion of the drainage. Throughout this interpretation of the history of the Dead­ man Canyon area, drainage diversions have been noted as occurring from time to time. Other diversions are likely to occur at many places in the Colorado Springs region. One such locality lies at the place marked (G), in Figure 21 along Little Turkey Greek. Here a L ittle Bear Oreek tributary is encroaching on the channel of Little Turkey Creek. A low, relatively narrow divide separates the two drainages. The smaller stream, developed down the north slope of this divide, drops a vertical distance of more than 100 feet in only a few hundred yards, this gradient being excessively steep in comparison to that of Little Turkey Creek (155 feet per mile). It is suggested that only a slight reduction of this drain­ age divide w ill be required before one of the infrequent torrential floods along Little Turkey Creek w ill be capable of overtopping this divide. The erosive power of even a portion of such a flood w ill deepen the smaller channel and increase th® potential for similar activity in the future. Eventually, complete diversion of the L ittle Turkey Creek channel may occur, adding to the runoff 86 of the L ittle Bear Greek drainage. Buch an increase in the total number of floods occurring in the latter may have considerable ef­ fect on processes obtaining farther downvalley. It Is this writerfs opinion that similar drainage diversions have occurred innumerable times in this region, and may be responsible, at least in part, for the local variations in slope directions on the piedmont surfaces, as well as differences in steepness of slope, size, and elevation of these surfaces. EXPLANATION

HIGH LEVEL GROUP

H ighest Level

Intermediate c o n t a i n ©/- Level

-) /.-s ;\ ; ! o ’ : •• v>, ' / T m ? u x CIK Low est : V*' ' r -A ’ ssff\ .~s X A A. Level i /4~At M' i 4, C --I >/ A & >> ,'7 INTERMEDIATE GROUP y/ £■■ 'j """v^ ?—5 H ighest Level

Intermediate ^ 5 § : ; ^ Level

Low est Level

\ v ^ n T \ \ . '®C LOW LEVEL GROUP

Intermediate Level

Low est Level

TERRACES ALONG LITTLE BEAR- LITTLE FOUNTAIN CREEKS

H ighest -© Next Lower

DAKOTA RIDGE

Granite - Sediment C ontact

Trend of Remnants

Slope of Remnants

Main D ra in a g e/ Turkey C r e e k Tributary Drainage

Colorado Highway 115

Little Bear Greek W atergap

Turkey Greek W atergap

Potential Diversion Little Turkey Creek SCALE I MILE Dakota Ridge 1000 5 0 0 0 FEET @ W indgap

Figure 2J^ AGE 0 QN3IDERATIONS

Finlay (1916 , p. 11) concludes that the presence of a molar tooth of Elephas columbi In the basal portion of the alluv­ ium underlying the Mesa Surface west of Colorado Springs fixes the age of that lowest (youngest) mesa gravel as Pleistocene and there­ for© contemporaneous with the glacial deposits in the higher valleys on Pikes Peak....» .The higher mesa gravels are in part equivalent in age to the Nussbaum g ra v els, mapped in the Pueblo folio, which are regarded as of late Tertiary age.* Finlay further established the age of the "terrace gravels* around Colorado Springs as late Pleistocene, though he did not note the occurrences of these deposits in other localities in the quadrangle. Gilbert (1897# P« 3) made the following notation concerning the Nussbaum formation which he considered to be Neocene in ages * The Nussbaum is not conformable with any underlying form­ ation, but rests on eroded surfaces of the Pierre, Niobrara, and other Cretaceous str a ta . The la r g e st and th ic k e st body is on Baculite Mesa. A second body occupies the mesa north of Blue H ill, and there are others between that and Turkey C reek.* Gilbert also pointed out the existence of other alluvial deposits occurring in step-like arrangement at lower level© in all the prin­ cipal valleys of the Pueblo quadrangle. These he placed as earlier and later Pleistocene in age, observing (p. 3) that: * Each terrace was, in fact, once the floodplain or bottom land of the stream, and their arrangement in steps is a record of the gradual deepening of the valleys by erosion. Their order of position is also their order of age, but in an inverse way, as the lowest is the latest.* The Deadman Canyon Surface was traced southward in to the Pueblo quadrangle, I ts gravels are Nussbaum form ation as described by Gilbert. Except for minor ©rosional breaks in the continuity,

87 aa the Deadman Canyon Surface on the 11 Paso-Fueblo County Lin© Is the same as Gilbert* s surfaces to the south, furthermore, the ele­ vation of the northwestern edge of Baoulita Mesa, and the slope of this surface toward the southeast, strongly suggests that all alluvial deposits considered by Gilbert to be Neocene in age be­ long to surfaces of the High Level Group. The elevation of the main High Level surface on the II Pas© * Pueblo County Line is 5,800 feet, and that of the northwestern edge of Baculite Mesa is 5,300 feet. The 11-mile interval between thee® places is occupied by the valley of Fountain Creek. A profile gradient of about 35 fe e t per mile would connect them, This is a slope which might reasonably be expected for the High Level interstream flats in a locality 30 miles east of the mountain front. The highest terraces, regarded by Gilbert as being of early Pleistocene age, are downvalley (Fountain Creek) continua­ tions of Low Level Group surfaces described herein. Lower terraces, late Pleistocene in age according to Gilbert, occur in relatively continuous fashion from Pueblo northward along the valley of Foun­ tain Creek. These continue upstream along the valleys of the Colo­ rado Springs region. Tan Tuyl and Lovering (1935, P* 1349) call the Deadman Canyon Surface of the High Level Group of this study the Orodell berm, which they consider Pliocene in age. They note further (p* 1329)i " The gravel-strewn rook benches below the high-level gravels associated with the Orodell surface are closely related to the present valleys. Th® character of the gravels, as well as the interval between th© benches on which they 11®, suggests a correlation with rock benches and terrace gravels farther west In th© moun­ tains where the relationship to various Pleistocene glacial epochs is obvious." 89

These authors also state: It is certain that at least two stages of Pleistocene g la c ia tio n occurred in the Front Range* and the inter-* mediate terraces suggest a third the valley® were deepened in successive glacial stages, As the climate became more humid the volume of th© streams Increased, erosion became more marked, and canyon-cutting ensued. As the clim ate became d rier during the in te r g la c ia l per­ iods, valley-deepening ceased, and the streams spent their energy in lateral corrasion and transportation, while the interstream areas were,being lowered by sheet- wash and pedimentatioa. The terrace gravels may, in large part, mark the periods of ice recession and th© related interglacial stages, The climatic changes of the Pleis­ tocene seem adequate to explain th© successive terraces, but, in addition, regional uplifts may be involved,* The age determinations of Finlay, Gilbert, or fan Tuyl and Lovering are not co n clu siv e, The occurrence of RXephas columbi or other evidence cited has little weight, other than the rather ob­ vious suggestion that all gravels and interstream surfaces of this region are comparatively young. Wahlstrom (1947, p. 5&8) regards th© differentiation of levels as being related to mountain uplift, as indicated in the fol­ lowing quotation. " The uplift of the Front Range to its present elevation was not the result of a single upheaval. The presence of more or less poorly developed terraces in the mountains and very well developed terraces in the valleys east of the mountains suggests Intermittent uplifts. Th® ter­ races are cut below and postdate th® early Pleistocene Ice-sheet till." While the postulate of intermittent uplifts might explain the presence of various interstream flats and valley terraces, It seems more likely that the differentiation of levels has been produced in another way, by slight alternations between wetter and drier climatic conditions* Even the uppermost, oldest High Level surfaces appear to be distinctly younger than the so-called Rocky Mountain pensplain. 90

The latter lies at an elevation of from 9,500 to 10,000 feet in the mountains along th© western edge of th® Colorado Springs region. Th© highest piedmont surfaces reach to about 7,500 feet; Projected upslope at a reasonable gradient they fail to attain peneplain ele­ vations by at least 1,500 feet. Wahlstrom assigns a pHosene or early Pleistocene age to th© peneplain. It appears as if there existed a considerable time interval between the development of the Rocky Mountain peneplain^ so-called, and the development of the High level Group of surfaces of this region, one that precludes acceptance of Gilbert*© idea that the Nussbaum gravels are as old as Pliocene (Neocene), furthermore, the Deadman Ganyon Surface could not correlate with Tan Tuyl and Lever­ ing* s Orodell berm, the latter being considered as Pliocene in age by these authors. The higher Interstream flats appear to date from th© Pleis­ tocene. A climatic interpretation of differentlation of various lower surfaces suggests a correlation with alternations between glacial and interglacial stages. The presence of Elephas cGiambi in the low Level Group of interstream flats suggests later Pleist­ ocene. The still younger stream terraces along existing valleys may have developed during the Recent* GOHOLTJSIOKS

The piedmont interstream surfaces of th© Colorado Bprlngs region were developed by a combination of sidewall retreat and stream erosion such as is occurring today. In the region behind the mountain front these processes are producing localised flats below steep canyon walls. In the piedmont, where rocks are less resistant to agencies of sidewall retreat and erosional scour, wider valley flats are being formed. These broaden dowaslope, es­ pecially across the outcrop of the Pierre shale. The fundamental differences between the small canyon flats within th© mountains and the wide, flaring valley flats of the piedmont are those of size alone, and arise because of the contrasts In the surrounding llth o lo g y . The present is a time of semiarid climatic conditions under which the region Is subjected to occasional heavy downpours of rain of localized nature accompanied by flood runoff. Torren­ tial stream flow is able to carry off any surplus weathered debris supplied by valley walls. Streams are able to scour their channels locally into th© bedrock underlying the alluvium of their valleys. Fans from tributary channels, log jams and boulder plugs, and other obstacles to flow actively divert the runoff into new courses across the canyon flats and valley floors. Diversions are so numerous and the channels shift so widely that the canyon flats and valley bottoms experience bedrock scour In praotlcally all places. As the depth of scour is comparatively uniform a relatively flat bedrock base develops under the alluvium. At many places

91 92

streams Impinge directly against canyon or valley walls, The flats are widened by lateral corrosion in such places, Th© normal retreat of sidewalls is aided, not only by lateral corrasion acting locally, but may also take place according to the "gully gravure* thesis of Bryan (1940), particularly in the piedmont valleys. The differentiation of piedmont surfaces into various levels appears to b© related to climatic changes, rather than to intermit­ tent uplifts of the Front Ranges, as suggested by Wahlstrom. Under semiarld climatic conditions eanyon-basin and valley-flat widening prevails, as at present. This is presumably an expression of inter- glacial conditions. Under a more humid regime streams cut channels to lower levels at proportionately faster rates. Valley widening during such times is subordinate. These atrearn-intrenchment episodes apparently mark th© more humid, glacial stages# An alternation be­ tween episodes of valley widening and channel deepening would ac­ count for the differentiation of levels observed, even though moun­ tain uplift continued at a uniform rate. This thesis agrees with known facts of Pleistocene climatic conditions and accepted theories of mountain development far better than the idea of intermittent u p lif t s . One of the most significant conclusions derived from th© study of the piedmont surfaoes concerns the diastrophle history of the Front Ranges. The eastern mountain front is only in a very Indirect way a product of fault activities, though locally the re­ lationship between mountain front and fault may appear striking. Th© presence of a thrust fault at th© boundary between mountain and piedmont, along Cheyenne Mountain and at various other places, might suggest that the ©astern face of th© Front Ranges is 93

steep anS has a comparatively fresh appearance because the mountain block was thrust forward and upward to the east during the Plio­ cene or Pleistocene. Finlay (1916) apparently believed that normal faulting during the Pliocene accounted for the mountain face. In actuality the chief effect of the faults on topography is secondary. Fault displacements have resulted in today*® outcrop patterns in th® bedrock. Topography is primarily related to lith - ology. Gheyenne Mountain rises very abruptly from the piedmont be­ cause it is a block of material that resists erosion far more ef­ fectively than the piedmont rocks to the east. The ©astern face of th® Front Ranges is an expression of differential erosion In contrasting types of bedrock. The thrusting observable in th© Oolorado Springs region may have been inactive since early Tertiary times. The mountains ar© present because they are being slowly uparched. Th© rocks ar© being worn away as th® up- arching proceeds. Where they ar© more resistant they survive longer and form topographic highlands. When the oldest, highest, piedmont flat was formed, it developed between valley walls. An uparched flank of the mountain mass extended considerably eastward from the position of the moun­ tain front today. Canyons were cut where granite and other resis­ tant rocks, such as lie above th© Cheyenne Mountain Thrust Fault, were encountered by streams; and broader flats developed to the east, in the sedimentary section below the fault. This interval of val­ ley widening was long. The locations of the most important mountain canyons wore determined, and th© piedmont flats to th© east became very widespread* 94

With continuation of mountain uparchiag, but an introduc­ tion of a more humid climate, came an interval of stream intrench- ment. Canyons were deepened in the mountains ©rasing a ll or most traces of the canyon basins which had formed during the previous semiarld regime. A return to semlarid conditions brought on the next episode of valley widening, but at a lower level* Three main episodes of valley widening have occurredi (1) that producing the High hovel Group, {%) that producing the Interm ediate and Low Level Groups, and (3) that going on today in the modern valley bottoms# Minor fluctuation® during these epi­ sodes account for the lesser levels within each of the main groups, and for the stream terraces along todayfs valleys# Bailey, R.W, (1914) Floods and accelerated erosion in northern Utah, B.s. Dept, Agric. Misc. Publ., no, 196, 21 pp. Baker, C.L, (1911) Botes of the later Oenozoio history of the Mohave Desert region in southeastern California, Gaiv.

Galif• Publ,, vol. 6 , no, 15, p. 333-333. Berkey, C.P., and Morris, F*K. (192?) Geology of Mongolia, vol.

2 , chapt. 19, p. 323-348. Blackwelder, Eliot (1929) Origin of the piedmont plains of the Great Basin, (Abstract), Geol. Boo. Am,, Bull., vol. 40, p . 168-169. ------(1934) Desert plains, Four. Geol., vol. 39, p- 133-140. Bradley, W.H. (1940) Pediments and pedestals in miniature, Four. Geomorph., vol. 3* P* 244-255 Bryan, Kirk (1922) Erosion and sedimentation in th© Papago Country, Arizona, G.S.Geel. Survey, Bull, 730, p. 19-90 ------(1925) $h© Papago Country, Arizona, 4 U.S.Geol. Survey, Bull., W.3. Paper 499, p. 1-436 ------—------(1936) The formation of pediments, 16th Intern. Geol. Cong. Rept. (1933), vol. 2, p.

765-775 ______—(1936 ) Processes of formation of pedi­ ments at Granite Gap, Hew Mexico, Zeitsohrift fur Geom- orphologie Band IX, p. 125-136. ______—*— -(1940) Gully Gravure, A method of slope r e tr e a t, lo u r. Geomorph. v o l. 3, P* 89-107

95 96

(1946) The retreat of slopes, Annals Assoc. Amer. Geog. Cong., vol. 3 0 , p. 254-263 —,and McCann, F.T. (1936) Successive pediments and terraces of the upper Rio Puerco in Hew Mexico, Jour. Geol., vol. 44, p- 145-172 D avis, W.M* (1905) The geographic cycle in an arid climate, Jour. Geol., vol. 13, p. 3®l-4&6 — — — — (1930) Rook flo o r s of arid and humid clim a tes, Jour. Geol., vol. 3 8, p. 1*27, 136*158 —------(1936) Geomorphology of mountainous deserts, 16th Intern. Geol. Cong. Rept. (1933), vol. 2, p. 663-714 -—------(1938) Sheetfloods and streamfloo&s, Geol. Sec. Am., Bull., vol. 49, p. 1337-1416 Denny, C. 3. (1941) Quaternary geology of the San Acacia Area, Hew Mexico, Jour. Geol., vol. 49, p. 225-260 Bekls, Rollin (1923) Alluvial fens of the Cucamonga D istrict, southern California, Jour. Geol., vol. 36, p. 224-247 Fenneman, N.M. (1905) Geology of the Boulder D istrict, Colorado, U.S. Geol. Survey, Bull., no, 265, p* 11-19 Field, Ross (1935) Stream carved slopes and plains in desert mountains, Am. Jour. 3ol«, 5th ser., vol. 29, p. 313-322 Finlay, G.I. (1916) Description of Colorado Springs folio, U.S.Geol. Survey, Folio no. 203 Frankenfield, H,0. (1923) Rivers and floods, U.S.Monthly Weather Review, vol. 51, p- 420-422 G ilb e rt, O.K. (1377) Report on the geology of the Henry Mountains, Utah, U.S. Geog. Geol. Survey, Rooky Mt. Region, p. 1-160 97

(1B97) Inscription of Pueblo folio, U.S. Geol* Survey, Polio no# 36, p. 1*7 Giiiuly, James (1937) Physiography of the AJo Region, Arizona, Geol. Soc. Am., Bull., vol. 4®, p. 323*348 Glook, Waldo S. (1932) Premonitory planetions in western Colorado, PanAm. Geol., vol. 57, p. 29*37 Hayden, P.P. (1873) U.S.Geog.Geol. Survey of Colorado, p. 36 Howard, A.D. (1942) Pediments and the pediment pass problem, Jour. Geomorph. v o l. 5, p. 1*136 Johnson, B.W. (1931) Plains of lateral normelon, Science, n. s., vol. 73, p. 174*177 — • (193I) Rock fans of arid regions, Am. Jour. S ci., ,5th ser., vol. 23, p- 389*416 (1932) Rock planes of arid regions, Geogr. Rev*,

vol. 22, p. 656-665 K essili, John E. (1941) ^he concept of the graded river, Jour* Geol., vol. 49, p. 561*588 Erumbein, W.O. (1940) flood gravel of San Gabriel Canyon, California, Geol* Boo* Am., Bull., vol. 51, P* 639*676 Erumbein, W.C. (1942) flood deposits of Arroyo See©, Los Angeles County, California, Geol, Soe. Am., Bull., vol. 53, p. 1355*1402 Lawson, A.C. (1915) Epigen© profiles of th© desert, Univ. Calif. Fubl., Geol.,vol. 9, p* 23-48 Lee, W.f. (1900) The origin of th© debris-covered mesas of Boulder, Colorado, Jour. Geol., vol. 8, p. 504*511 Mackin, J.H. (1937) Rrosional history of the Big Horn Basin, Geol. Boo. Am., B ull., vol. 4 8, p. 813*894 Mattiies, IM* (1930) Geologic history of th© Yosemit© Talley, TJ.S.Geol. Purvey, Prof. Paper 160, p. 1-137 McGee, W.J. (1897) Shoetflood ero sio n , G eol. See. Am., B u ll* , vol. 8, p* 87-112 M ortensan, Hans (1927) Bar Formenschatz der ^ordohilenischen Wuste, Abhandl. Gas. Wlss. Gottingen Math-Phys• ICl.R.F., 3d. 12, p. 1-191 O gilivie, I.H. (1905) ^h© high altitude conoplain, Am# Geol., vol. 36, p. 27-34 Paige, Sidney (1912) Rook-out surfaces in desex*t regions, Four. Geol#, vol. 20, p. 442-450 Fassarge, 3. (1904) Me Kalahari, Berlin Ray, L.L., and Smith, J.F. (1941) Geology of the Moreno Tal­ ley, New Mexico, Geol. 3oc, Am*, Bull,, vol. 52, p* 177-210 Rich, John 1. (1935) Origin and evolution of rock fans and pediments, Geol* See. Am., Bull#, vol. 4 6 , p# 999-1024 Sharpe, R.P. (1940) Geomorphology of the Ruby-Baet Humboldt Range, Nevada, Geol. 3oo. Am., Bull., vol. 51, p# 337-371 Tolxaan, C.F. (1905-19O6) Rotes on d esert processes and d esert d e p o sits, Jour. Proo. Ann. Oonv. Arizona Miners A sso c.,

p. 15 • ------(1909) Brosion and deposition in the southern

Arizona bolson region, Jour. Geol. vol. 17, p. 136-163 Tan Tuyl, F. M. and hovering, T*3. (1935) Physiographic development of the Front Range, Geol. 3oc. Am., B ull.,

v o l. 4 6 , p. 1291-1350, Fla. 101 108* Wahlstrom, K.R. (1947) Oenozoic physiographic history of the Front Range, Colorado, Geol* Soc. Am., Bull., vol. 58, p. 551-572 Waibel, I*. (1.92®) Cebirgsbau und oberflachengestalt der Kanasberge in Sudwestafrika, Mitt* deutsch. Schutgeb. vol. 33, p. 2-28, 81-114 Woolley, Ralph R* (1946) Cloudburst floods in TTtah, tr. S. Oeol, Survey W. 3, Paper 994, p* 1-128 XT. 3, Weather Bureau Climatic Summary, (1916), Sect* 24, P Colorado Springs Cassette June 27, 1884 Colorado Springs Cassette August 1, 1885 BIOGRAHIY

The author, Benjamin Almon Tator, was born in Poughkeepsie, New York, August 13, 1914. He recieved his elementary education

in Poughkeepsie High Schoolt graduating in 1932. He entered Columbia U n iv ersity , New York C ity, in 1935 and obtained the degree of Bachelor of Arts in 1939. A Master of Science degree in Geology was conferred on him by Louisiana State University in June, 1941. He is at present a member of the faculty of the School of Geology at Louisiana State University# 5,000

- Mountain 0 Highest Level - Deadman Canyon Surface Surface Canyon Deadman - Level Highest 0 oet ee - " 11 " " - Level Lowest 0 nemdae ee " " " " Level- Intermediate 0 nemdae ee " 1 " " 11 Gr. Surfaces " Turkey Level Little - Intermediate - 0 Level Highest 0 oet ee ~ uky re Surfaces Greek Turkey ~ Level Lowest 0 Rsoe Profiles Restored — © Highest Level - Rock Creek Surfaces Surfaces Creek Rock - Level Highest © oet ee - 1 " 11 " " - " Level Lowest 11 © Level- Intermediate ® B Tre Creek Turkey (B) S Ltl Tre Creek Turkey Little (S) 0) 0) Creek Bear Little (C) □ Ltl Futi Cek X Dkt Rde et f ee 0 Level of West - Ridge Dakota (X) Creek Fountain Little (□) ok re © " Es o Level of East " " © Creek Rock 0 etcl xgeain 3X Exaggeration Vertical LT 3 PLATE PLATE 2 CNO VERTICAL EXAGGERATION) ROCK CREEK SURFACES

NE sw

MIDDLE LEVEL OF ROCK CREEK SURFACES

Cot OenfJt/ £’a.sfurard~dfppjng Sedtmenfa CJCp)

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MIDDLE LEVEL OF ROCK CREEK SURFACES

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Coterva'o U /^ u/ag

NESW

MIDDLE LEVEL OF ROCK CREEK SURFACES LOWEST LEVEL OF ROCK CREEK SURFACES

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RED CREEK SURFACE

SW NE

MIDDLE LEVEL OF THE INTERMEDIATE GROUP

.c .'.-vc;;- -: Ced : CreeA. Oen//y Wesfujcrrd-dipping Sed/msnfj (CfJ

. FIGURE 2. SHOWING CROSS-SECTIONS THROUGH ROCK CREEK SURFACES OF THE LOW LEVEL GROUP AND RED CREEK SURFACE OF THE INTERMEDIATE GROUP ALONG COLORADO HIGHWAY 115. THE LOCATION OF THESE SECTIONS IS INDICATED BY THE APPROPRIATE LETTERS ON PLATE I. NOTE THE CHANNEL-LIKE IRREGULARITIES IN THE OTHERWISE SMOOTH BEDROCK SURFACE. PLATE I. COLORADO SPRINGS QUADRANGLE HfGH LEVEL GROUP

Highest Level

Intermediate Level

Lowest Level

& INTERMEDIATE LEVEL LOW LEVEL Rampart Rang* GROUP GROUP

Highest Level

Highest Level=(equivalent)= Intermediate 1 M.t Cascade Level Intermediate Level Lowest Level 89 COLORADO Lowest Level ./ / /' Mt Mantfou^.-' SPRINGS J^VUMANITOU Dakota Ridge

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