THE
AM ER ICA N AS SO CIA TIO N OF
PE TRO LEU M GE OL OG IST S bUL LE TIN
V. 51, NO. 11 11 (NOVEMBER. (NOVEMBER. 1967), P. :?246-2259.
4 FlGS
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DRAINAGE ANALYSIS IN GEOLOGIC INTERPRETATIO'\
.\ ." CM:MATI0
1
ARTHUR DAVID HOWARD' Stanford, California o.no, AB:-,TRAl'T Drainage analysis is useful in structural interpretation, particularly in areas of low lo w relief. Analysis includes consideration of drainage patterns, drainage texture, individual stream patterns. and drainage anomalies. Drainage patterns generally are subdivided into basic and modified basic. To these might be added pattern varieties. A basic pattern is one whose gross characteristics readily distinguish it from other basic patterns. Modified basic patterns differ from the type patterns in sorne fairly obvious regional aspect as, for example, a tendency toward parallelism of the larger tributaries in a dendritic pattern. Thus many modified patterns are transitional in character between basic patterns, and the naming of such patterns may be a matter of judgment. Pattern varieties are characterized by interna! details, commonly obscure. In a broad sense, the basic patterns, the modified basic patterns, and the pattern varieties are analogous to the genera, species, ancl va rieties of the zoological classificatio n. A complex pattern consists of two contemporaneous patterns adjacent to each other; a compound pattern consists of two unlike superi mposed patterns. The palimpsest pat tern cnnsists of two super imposed patterns, but one is a paleopattern. Drainage texture depends on a variety of o f factors. In any one small area where al! other factors are constant, constant, drainage texture may provide information on underlyin¡.; materials and indirectly on structure. Individual stream patterns may display characteristics similar to th,,se .,f tl1e gross drainage pattern and may be referred to by the same name. Thus individual patterns may be referred to b, such terms as rectangular, angulate, or contorted. Other strcam patterns includc irregular, rectilinear. meandering, braided, misfit, and beaded. Drainage anomalies are local deviations from drainage and stream patterns which elsewhere accord with the known regional geology and/or topography. The expectable pattern is regarded as the norm; the anomalies indicate departures irom t he regional geologic ,ir topographic controls. Analysis of drainage anomalies has revealed structural rhta in ,ome tlatland re inn, whn,· qther melhocls of investigation have been unsatisfactory. lNTRODUCTION
DRAI,AGE l'ATTERNS
Drainage analysis is an importan( too! ín pho togeologic interpretation, particularly in arcas o i low relief. It may provide clues to inactiYe struc tural features exposed at the surface, to slructur al fcature, currently rising, and, possibly, to bur
A Jrainage p,itt,-r11 i, ; h,: design formed by the aggregate of drainage,,a,·., in an area regardless
iccl ,tructural features. The density of drainage may provicle information on permeahility and texture of materials, ancl may may infer the idcntity of materials. The characteristics ancl significancc of drainage pattcrns, drainage !C'xture, indiYidual stream patterns, and drainage anomalies are con sidered herc. Technic¡ucs involvLng grid sampling and thc use of digital computers eventually may rcsult in the application of numerical values to drainage pa1terns 1 Ierriam and Sneath 1966). It is too early. however, to speculate on the advantages and disadvantages of this procedurc. 1
::\fanuscript received, June 25, 1966; accepted, Feb
of whether thcy m· , ,, ,upied by perrnanent streams. A str,-,w1 po11!1 ,-¡1 i, the desi¡m formcd hy a single drainagl'way
Both basic
and
rnodilicd
basic
drainage
pat
terns haw licrn d,·s,rilied ( Zernitz, 1932). In ad dit.ion to thesc· therc are drainage varicties. A /¡asic pattcrn i,; ,11w wlrn,c gross characteristics readily distinguish it frnm 01hcr basic patterns. A modifird basic pattcr11 differ, from the type basic pattern in sorne regi,mal aspee! as, for example, thc clme spacing 1): ,m,ill parallel tributaries in in the pinnate-rlendriti, pat·,·ri, or the preferred or ientation o f longer I ril ,uf aries in t he directional trellis pattern , Fig .. '. B ,111d G). Drainage
vari
eties diffcr from thc lia,i, and modifrcd hasic pat terns in interna! dctail,. Varieties arr legion and the application of indiYir!ml names is impractical.
In a broad sense, the hasi, patterns, the modified
ruary ,;, 1967. 2 Geology Department, Stanford Cniversitv. The writer is indebted to Chester R. Longweli and Stanley - Davis for review of the manuscript, but only he is responsible for its content.
basic patterns, and th¡: pattcrn varieties may he likened to t he gencr:1. s¡Jt-, ir, and varieties of t he zoological rlas,ifü at i1111
!246
DRAI AGE A ALYSIS IN GEOLOGIC INTERPRETATlO::-.J BASIC PATTERNS
::Vfost of the basic patterns are controlled bv regional structure. Zernitz (1932) classified ;s majar (basic?) the following patterns: dendritic, parallel, trellis, rectangular, radial, and annular. Because these are discussed in most elementary geology texts, only a pictorial review (Fig. 1, AF) and a brief summation of characteristics and geologic significance (Table I) are included. Two other pattems, multibasinal and contorted, are grouped with the basic patterns in this report (Fig. 1, G and H; Table I). The original or ear liest known references to most of the basic and modified basic pattems are recorded in the foot notes to Table I. MODIFIED BASIC PATTERNS
Modified basic patterns, although usually rec ognized as belonging to one of the basic types, differ in certain regional characteristics. Far ex ample, the degree of parallelism of the main streams in a region of dendritic drainage is gener ally a function of the regional slope. On different declivities, therefore, there may be ali transitions from dendritic to parallel drainage. Transitional types also may result from changes with time. The change toward parallelism might result from progressive steepening of a slope. Trellis charac teristics may appear in a dendritic pattem as streams are superposed from an overlying cover onto dipping rocks. Transitions among ali the basic types seem possible. Sorne of the modified patterns are considered below.
Dendritic Pattern Modifications Subdendritic.-Tbis pattern differs from the type dendritic only in the lack of perfection. Deviations are presumably due to secondary re gional controls, either structural or topographic. Thus, in part of the Amazon basin recently studied by the writer (Howard 1965), the den dritic pattern, inherited from an unconformable mantle, is being transformed to a trellis pattern by adjustment of tributaries to the strike of underlying formations. Along the lower Yellow stone River in eastern Montana, the dendritic drainage is slowly developing trellis character istics under the influence of a prevailing system of poorly expressed joints (Fig. 2, A). Pinnate.-This pattern is characterized by many closely spaced, more-or-less parallel tribu-
224í
taries entering the larger slreams at an acute angle. The drainage, therefore, has a featherlike or frondlike appearance (Fig. 2, B). The pattern is best developed in fine-textured, easily eroded materials such as loess. The fine texture of the materials accounts far the clase spacing of the small tributaries, and the steep valley sides are the cause of their parallelism. On sorne slopes, particularly solifluction slopes in the Arctic, the closely spaced parallel tributaries are long com pared with those in Figure 2. They are barely in cised into the gentle slopes and extend to the crests of the rounded divides. The pattern resem bles feathery plumes. Anastomotic.-This pattern, characterized by a network of interlocking channels, sloughs, bayous, and oxbow lakes, is found on floodplains and del tas and in tidal marshes (Fig. 2, C). Varieties of the pattern have been termed "reticular" by Par vis (1950, p. 43-44) and "reticulate" by White house (1944, p. 9). Distributary.-This is the branching pattern found on alluvial fans and deltas (Fig. 2, D). It resembles the dendritic pattern except that the tributaries diverge from, rather than converge to ward, the main stream. Parallel Pattern Modifications (Zernitz, Subparallel.-The subparallel pattern 1932, p. 518) shows less parallelism than the basic pattern. If due to slope alone, the pattern resembles that formed by the branches of a pop lar tree. Where due to mild structural control by deformed strata of relatively uniform resistance to erosion, there is sufficient parallelism among segments of the main streams and tributaries to suggest the bedrock control, but streams com monly diverge from the geologic grain. The elon gate streams are not ordinarily as continuous along the strike as those of the trellis pattern. These differences from the trellis pattern also apply to the subparallel pattern of drumlin areas (Fig. 2, E). Colinear.-This pattern (Zernitz, 1932, p. 519) is characterized by remarkably straight parallel streams or channels which alternately disappear and reappear (Fig. 2, F). The pattern is found in areas of linear Joess and sand ridges. Trellis Pattern Modifications Subtrellis.-The subtrellis pattern differs from the type trellis only in the degree of continuity
2248
ARTHUR DAVID HOWARD
FIG. 1.-Basic drainage patterns. Each pattern occurs in a wide range of scale,. Excimples shown may be regarded as types. Dendritic pattern resembles spreading branches of oak nr chest nut tree with tributaries entering at wide angles. In trellis pattern, small tributaries to long parallel sub,equent strcams are about same Jength on both sides of subsequent streams.
DRAINAGE ANALYSIS IN GEOLOGIC INTERPRETATIO:\T TABLE
l.
Basic Den cl ritic 1
SIGNIFICANCE OE BASIC AKD MODIFIED BASIC DRAINAGE PATTERKS Modificd Basic
Significance
Horizontal se
pat
tern resembles spreading oak or chcst nut tree.
-----Subdendritic Pinnate
9
Anastomoticlo Distributary (Dichotomic)ll
Parallel 2
T rellis 3
22-+9
Added ,\'ignificance or Locale
finor secondary control, generally structural. Fine-textured, easily erodable ma terials. Floodplains, deltas, anrl tidal marshes. Alluvial fans and deltas.
General1y indicates moderate to steep slopes but also found in areas of paral lel, elongate landforms. AH transitions possible between this pattern and type dendritic and trellis.
SubparalleJ12
Intermediate slopes or control by subparallel landforms.
Colinearia
Between linea loess and sand ridges.
Dipping ar folded sedimentary, vol canic, or low-grade metasedimentary rocks; areas of parallel fractures; ex posed Jake or sea floors ribbed by beach r idges. All transitions t o paral lel pattern. Type pattern is regarded here as one in which small tributaries are essentially same size on opposite sides of long parallel subsequent streams.
Subtrellis
Parallel elongate landforms.
Directional Trellis
Gentle homoclines. Gentle slopes with beach ridges. Plunging folds.
Recurved Trellis
Fault TreJlis14
Branching, converging, diverging, roughly parallel faults.
Joint Trellis
Straight parallel faults and/or joints.
Rectangular'
Joints and/or faults at right angles. Lacks orderly repetitive quality of trellis pattern; streams and divides lack regional continuity.
Angulate"
Joints and/or faults at other than right angles• A compound rectangular-angulate pattern is com mon.
Radial'
Volcanoes, domes, and erosion residu als. A cornplex of radial patterns in a volcanic field might be called multi radial.
Centripetal"
Craters, calderas, and other de pressions. A complex of centripetal patterns in area of multiple depres sions. might be called multi centnpetal.
Annular6
Structural domes and basins, dia tremes, and possibly stocks.
MultibasinaJ7
Hummock y surficial deposits; differ entially scoured or deflated bedrock; areas of recent volcanism, limestone solution, and permafrost. This de scriptive term is suggested for ali multiple-depression patterns whose exact origins are unknown.
Contorted 8
Contorted, coarsely layered meta morphic rocks. Dikes, veins, and mig matized bands provide the resistant layers in sorne areas. Pattern differs from recurved trellis (Fig. 2, H) in Jack of regional orderlines , disconti nuity of ridges and valleys, and gener ally smaller scale.
Longer tributaries to annular sub sequent streams general1y indicate direction of dip and permit distinc tion between dome and basin.
Glacially Disturbed
Glacial erosion and/or deposition.
Karst
Limestone.
Thermokarst17
Permafrost.
Elongate Bay"
Coastal plains and deltas. The longer tributaries to curved subsequent streams generally indi cate dip of metamorphic layers and permit distinction between plunging antidines and synclines.
1 Described by Dutton (1882, p. 6, 62, 63) and applied as a drainage terrn at least as early as 1898 (Russell, p. 204). Classified as a basic pattern by Zernit z (1932, p. 499).
,
Zernitz (1932, p. 510). Willis (1895, p. 186).
2
• First used in rnodern sense by Zernitz (1932, p. 503), but tbe pattern was recognized much earlier (Daubrée, 1879, p. 357-375; Kemp, 1894, p. 438-440; Hobbs, 1904, pl. 47). 'Radial drainage is described and illustrated in Jaggar (1901, p. 174, pl. XVIII) and is referred to by Dake and Brown (1925, p. 134). • Jaggar (1901, p. 277) refers to annular draniage, but Zernitz (1932, p. 507) may have been the first to apply the name to the drainage pattern. 7 The descriptiv e term "multib asinal" is used here as a substitut e for genetic terms such as "kettl ehole" and "sinkhole" wh ich have been applied to p atterns characterized by numerous depressions. The term "poly basin" (Parvis, 1950, p. Si) would have been appropriate had it not been restricted to tbe area of the Ogallala Formation in the Great Plains and specifically related to the presence of an impervious substratum. • Von Engeln (1942, p. 113,336). 9
Zernitz (1932, p. 512).
10 Described
as a pattern by Zernitz (1932, p. 514). The descriptive adjective "anastomosing," however, had been used long prior to 1932. Johnson (1932, p. 497) restricted the term "braided" to the interlacings of an individual stream. n Parvis (1950, p. 41) attributed the term "dichotomic" to Finch and Trewartha (1942). The writer was unable to locate the term in the 1942 reference or in the first edition of their E/,ements of Geography, but may have overlook ed it. Distributaries are mention ed on pag es 307,342, and 355 of the 1st ed., 1936, and on pages 290, 326, and 340 of the 2d ed., 1942. 12 Zernitz (1932, p. 518). 1 ' Zernitz (1932, p. 519). u Dake and Brown (1925, p. 191). 16 Zernitz (1932, p. 517). ,1
Davis (1889, p. 249).
1, Muller (1943), p. 50.
l8 Parvis (1950), p. 43.
2250
ARTHUR DAVID HOWARI> B. Pinnate
FIG. 2.-Modified basic patterns. Each pattern occurs in a wirlr ran;.,:e of scales.
and parallelism of the dominant drainage. The distinction betrween subtrellis and subparallel is commonly a matter of judgment.
Directional trellis.-This term is suggested ior a modifi.cation of the trellis pattern in rwhich the tributaries to the long sub,equent streams are
DRAINAGE ANALYSIS IN GEOLOGIC INTERl'JU:TATIOX
22S1
consistently longer on one side oí the valley than on the other (Fig. 2, G). The pattern most com monly is found in areas of gently dipping homo clinal beds, but also occurs on gentle slopes with parallel beach ridges.
clearly indicate une re, t angular system with ek ments oriented approximately north-south and eastwest, and anuthcr system oriented northeast southwest and northwcst-srmtheast. A remarkable <·xampk uf joint control is pres
Recurved trellis.-This is a modification of !he
ent in Frcnch Cuiana. where severa! sets of more or less equally spa, ,·el jomb impart a geometric pattern to both tlw clrainage and topography. The pattern has 1 >een referred I o as "honeycomb" by Zonnevclcl el 11/ :q.;_,_ p. IS3). Another ¡reomet ric pattcrn, "n a mur h ,rnaller seale, is found in permafrost arcas 1,hert· i,,· wcdgcs thaw around the margins of soil polvi;,>11.,. This pat.tern is best described as poly on:11
trellis pattern in which the pattern as a whole forms sweeping curves around the noses of plun¡r ín¡r folds (Fig. 2, H). It is more orderly ancl sys tematic, and generally larger in scale, than the contorted pattern in metamorphic terrain. Com parison of the lengths of small tributaries on op posite sides of the curved subsequent ,t reams. particularly at the noses of the folds, commonly permits distinction between plunging anticline., and synclines; the direction of flow of the longer tributaries generally indicatcs the
Fault trellis.-This pattern has been a!t ributed by Dake and Brown (1925, p. 191) to "alternat ing grabens and horsts or a succession of parallel rifts." It is described as less closcly spaced than the trellis pattern on tilted or folded slrata. with a tendency toward dendritic drainage bctween the faults. Right-ang-Ie turns are also less common. In the San :'1.fateo quadrangle, just south of San Francisco, California, the fault-controlled streams, although grossly paralle!, locally diverge. converge, and branch, and the broader i111er stream segments show dendritic, radial. or DI hrr drainage patterns (Fig. 3, A). Joint trellis.-A second fracture trellis pattcrn. characterized by short, remarkably straight paral lel streams, may be referred to as joint trellis. although the fractures may include faul!s. A good example is found in the Zion Park region of Ut ah (Fig. 3, B).
Both of the fracture trellis patterns differ from the rectangular pattern in having one dominant set of parallel streams. Rectangular Pattern Modifications
Angulate.-This pattern (Zernitz, 1932, p. 51 í is
characterized
by
numerous
1
acute-angle
bends and barbed tributaries. It is generally found in areas where an additional set ( or sets l of fractures is superimposed on a rectangular set. There may be two superimposed rectangular sys tems of different orientation. Figure 3C is a generalized portrayal of the drainage of part of the Yellowstone plateau. The drainage alignments
Radial Pat t,:rn .\1oclifications
Centripetal.--Thi pat t,·rn
( Da vis,
1889. p.
249) is a modifiration o! the radial which the st rcams. tlo1\ inwarcl toward nearly closed central dcprC'ssion ( Fig. pattern romrnonly i, .1s.,o, iated with
pattern in a closed or .l. D). The caters, cal deras, and a widt' vari,·ty "f depressions. In sorne areas, such as tht· ··pa11 hclt'· of the Union of South Afri,:a tKing, l'J,J. p. 91 l, there is a com plex of rentripetal pat t ern,. The regional pattern might be 1dcrr,·d r" :r, multicentripetal.
Iultibasinal l'attern Modificatio ns The multibasinal pattcrn orcurs principally in areas of glacial ernsion and deposition, eolian ero sion and deposition, solution, and permafrost. It also is founcl, howevl'r. in regions of recent vol canic activity anrl in lanrlslidc areas. There are many modifications o f ilw p¡tt \ern, even within individual regiom. Thu, in gfaciated areas, the majority of the depre,siDns may be small or largc, closely ;;pared 1>1 wídely scattered, and the drainage may display, aried amounts of integra tion. In sandy a rc:t,. thf rlcpressions may display great clivcrsi t y In ,hape :llld size in accordance with thr rharactni,1i<", (lf the dunes within which they orcur, and may al,o display a rcr!ain amount o[ intcgratcd drainagr. The patlern may then closely re,emhlr· tfw dminage pattcrn in mo rainal arca,. In volcanic areas. t he dcpressions may include cratcrs ancl raldera,. lava-dammed valleys, interflow basins. or , ollap,ecl lava caves or tun nck In many la\"a f1clds, depressions large enough to [)[' shown on topographic maps are less profusc than in morainal or sand areas.
2252
ARTHUR DAVID HOWARD
/
/ ···-.1 /
/
Palimpsesy- /
Y
/;/1 / ¡
J/ 1
11
\\ 1
1
Frc. 3.--Modified hasic patterns (A.-D 1; complex, compound. and palimp"·,t ¡,.ittern, (E-H). Each patlern '"·curs in a wide range ,,f ,calP,.
DRAJ AGE A ALYSIS IN GEOLOGIC INTERPRETATION In landslide areas, depressions are found either behind rotated slump blocks, within chaotically jumbled landslide debris, or where drainage ha, been blocked. This multibasinal pattern is usually of small regional extent. The multibasinal pattern is rarely diagnostic in itself of either process or material; patterns formed by different processes may be remarkably alike. A pitted outwash area in Minnesota illus trated by Cooper ( 1'935, Fig. 4, p. 10) is remark ably similar to the solution-pan landscape of parts of Florida. Multibasinal patterns in areas of moraine, sand
Zernitz (1932, p. 521) proposed the term "complex" for an aggregate of dissimilar patterns reflecting different structural controls in adjoin-
2253
ing areas. Parvis (1950, p. 43) suggested the term "anomalous" for complex patterns found in areas of differing topography and materials. The terms "complex" and "anomalous" have thus been applied to situations that are in part similar and in part dissimilar. Inasmuch as the term "complex" has priority, it should be retained but perhaps with its scope enlarged to include ali pat terns representing an aggregate of adjoining dis similar patterns due to structure, materials, and/ or differences in topography. In Figure 3, E, the contrasted patterns are due to differences in structural features. An example of drainage differences caused by differences in topography on identical materials is the multibasinal drainage of moraine versus the subparallel drainage of drumlin topography. The term "compound" was applied by D. W. Johnson (personal commun., 1931) to drainage consisting of two or more contemporaneous pat terns in the same area, as, for example, the com bination of radial and annular patterns character istic of many domes (Fig. 3, F). Dendritic and multibasinal patterns commonly are combined in areas where streams have cut youthful valleys into a relatively insoluble formation below a solu tion-pitted limestone formation. The depressions are restricted to the limestone-capped divides be tween the streams. A somewhat similar combina tion of patterns results from partía! integration of drainage in morainal areas. The writer encountered an interesting drainage pattern which he has called palimpsest (Howard, 1962, p. 2255). In the palimpsest pattern, an older, abandoned drainage or stream pattern forms the background for the present pattern. The example (Fig. 3, G) is in the western coastal plain of Taiwan. At the site of the anomaly, the present drainage pattern is radial. Faintly visible through the rice paddies is a meandering channel whose presence is indicated primarily by the somewhat smaller size of the paddies within its confines. The meandering channel crosses the present low topographic bulge toward its crest. Clearly, the topographic high was not present when the meandering stream crossed the area. The meandering stream apparently was deflected by the growing arch on which the present radial drainage carne into existence. The situation sug gests either active deformation within the coastal plain, not an unlikely possibility considering the
ARTHUR DAVID HOWARD
2254
instability of the island of Taiwan as a whole, or differential settling over a buried topographic high, or both. Any drainage pattern that includcs traces of an older, unlike pattern may be re ferred to as palimpsest. Remnants of original stream courses are common in many arcas of gla cial and eolian activity, multiple piracy, and re cent warping and faulting. Figure 3H illustrates in generalized fashion the relation oi r he fo souri River (or the Ohio Rivcr) to ahandoncd preglacial vallcys.
deflectinn uf ,treams aruund bodies of relatively unfractured or otherwi,e resistant rock. Comparable varictie, are founcl in each of thc other hasic ancl modil1ed IJasic patterns. A de tailed treatmcnt u I l he,L· i, beyond the scope of this report. Thc irnportam ¡lOint is t hat cardul study uf local departun·· irnm the re_giunal pat terns may n•v1.:al unsuspc, Tt·d information of con siderable \·alu,·. Thr- analy,i, of clrainage varieties and of t he relat ed ,h1in,1g,· anomalies discusscd helow prc·smh ;¡_ 11:1iqw , halll'nge to gist.
thc
geolo
PATTERN VARIETIES
Pattern varieties differ from ba,ic and modi fi.ed basic patterns in interna! details. They com monly provide useful geologic information. Regional differences, such as contrasts in densi ty of drainage, do not distinguish varieties. It is expectable that a dendritic patlern in shalc will be finer than that in sandstone, and that a l rellis
ÜR.\I'.\ \C,E TEXTURE
Drainage textun· rd,:rs 10 the rclative spacing of drainage line, regardle,s uf occupancy by percnnial strcams. Tht tnms ''fine," '·medium,'' ancl "coarse·· gennally
:11,·
uscd in a
relative
,pa, ing. A fine texture is one m whi, h t hl'n· 1, a high degree of ramification oí clraiuag,· lines resulling in a dense network involving myriacl small streams. Fine texture is typical 01 , lav. ,halP. silt. ancl other rclatively impen·iou, mal nials. A coarse tcxturc, in contrast, t·xhihiis \l'rY littlc ramification, and longer. more witkly .,,·par:1tecl valleys prevail. Coarse texturt'. i 1ypiul ,,i permeable materia!s such as sand, grawl. and rocks that wcather into rnarse fragmrnt,. :\ledium lexturc is interme cliate between the two r·xtrcme,. The use of the,,· textura] terms without clariftcation i, inadvisal>lc. not only because they scnse to indica!<'
1 he
pattern in slate will be íiner than that in in terbedded sedimentary strata. Any drainagc pat tern may be fine, medium, or coarse texturerl. Intrapattern differences in texture, huwever, do distinguish varieties. Thus, a dendritic pattern in an area in which thick, horizontal beds of sancl stonc and shale are exposed in the slopes may display a coarse texture in the sandstone and a fi.ncr texture in the shale. The pattern is ·'¡ extur ally zoned." In another variety of the dendritic pattern, many strcams consistently are closer to nnc side of their valleys than the other. In the Lcavcn mean differcnt thirw:s t,, diffcrent people. but be worth quadranglc (Kansas-Missouri). stn·ams cause tcxturr \·aries wit h ,cale. Attempts have that flow generally cast or west hug the stecper becn macle lo cxprc" r nl u 1·cs quantitativcly on south ( north-facing) ,Jopes. The clendritic pattcrn the basis of the numlier ( ,t n:am frcquency) and suggests essentially horizontal sedimentary rucks total length I drainagc den.,i1y) oi clrainagc lincs or bcveled, uniformly resistant crystalline rocks, per unit arca 1Horl1>n 1/-J., Smith, 1950). How but the valley asymmctry suggests an adclitional cver, quantitati\"l: tkt erminations of texture in influence such as a gentle southward clip, allive ,·olve laborious, tirnc-,·1,nsuming procedures, ami tilting. or differences in degree of erosion of thc thc resulting dcgrir:, "1· rdincment are greater valley slope due to direction of exposure. That than ncrcssarv i,n rnany geologic problcms. A the a,ymmetry is not duc to stream dctlection satisfactory procedure •or 1·eports is to prepare resul ting f rom terrestrial rotation is cvident írom diagrams showing the drainage texturcs, at thc the fact that the steep slope is on the left :iirle of scale of the maps or photo,. that are regarded as sorne stream, and on the right side of others.' tine, medium, anti, ,1a1,,· ,ml perhaps as ultrafine Another variety of thc clendritic pattern. t har ami ultramar"·· acteristic of granitic arcas, displays numerous ,ick Drainage text urc i, intlul'ncecl by ( 1) climati lelikc curves. Thesc apparently are the result of cally rnntrolled factors ,u, h as amount ancl dis tribution of prPcipitatiun, \·egetation, anrl per 'The term right and left apply when facing down mafrost; t 2) rn,k , haractnistic,, including tcxcurrent.
DRAIXA(;E AXALYSIS IN GEOLOGIC INTERPRETATIO ture and size of fragments released by weather ing; (3) infiltration capacity; ( 4) topography; and (5) stage and number of erosion cycles. In any one small area of study, the climatic factors, the topography, and the stage and number of ero sion cycles may be reasonably constant, so that the variations in texture will reflect differences in rock characteristics and infiltration capacity.
225S
Vegetation, with its absorbent root mat ami underlying soil, retards runoff and reduces development of rills. Thus, the texture of drain age in humid climates is generally coarser than in arid climates, and the texture is coarser on heav ily vegetated slopes than on barren slopes. Sorne grave! deposits display a medium or even fine texture of drainage. Such gravels may have a high content of "fines"-materially reducing the permeability-or may be exposed on steep slopes, such as terrace scarps or steep dip slopes where the velocity of flow is rapid enough to insure considerable runoff. Drainage texture may vary within the confines of a single drainage pattern depending on the na ture of the rocks exposed. Theoretically, the crosscountry trend of the boundary between tex tura! zones should assist in correlation of rock units from one drainage basin to another.
In unconsolidated sediments, the drainage tex ture is related directly to grain size. On similar declivities, small rills can easily move particles of clay and silt and develop myriad small channels, whereas larger streams, that is, the accumulations from larger watersheds, are required to move sand and gravel. Hence the channels are more widely spaced. As Schumm reported (1956, p. 607), a certain mínimum drainage area is required to maintain a stream channel in an area of uniform lithology and simple structure. He expressed this quantitatively as a constant of ckannel mainte STREAM PATTERNS nance, which is actually an expression of texture. The reader is referred to Schumm's paper for The names applied to stream patterns are self further discussion of this relationship. explanatory, and most of the patterns are so well In areas of hard rock, the size of the frag known that further explanation is not required. ments provided for transport is the decisive fac However, a few comments seem pertinent. tor. The removal of large blocks ordinarily re Sorne individual stream patterns show the quires larger streams than does the removal of characteristics of the overall drainage pattern and small fragments, if there are no strong contrasts are referred to by the same names (J ohnson, in stream gradients. Texture of drainage in gran 1932). Thus, a stream showing right-angle bends ite areas, for example, may range from fine in may be referred to as rectangular; one with acute closely fractured zones to coarse where the frac angle bends, as angulate; and one with tight hair tures are more widely spaced. On very gentle pin turns, as contorted. The geologic implications slopes in humid climates, deep weathering may of these stream patterns are the same as for the result in a fine-textured soil regardless of the rock corresponding drainage patterns. type below. The fine-textured debris, however, Other distinctive stream patterns are: the ir generally influences the texture only of that part regular pattern characterized by a more or less of the drainage system that has not eroded random course and suggesting an absence of through the surficial mantle. structural or topographic control; the rectilinear Infiltration capacity, the rate at which water pattern, with abnormally long straight reaches, soaks into the ground, depends to a large degree generally indicating fracture control; the mean on permeability. Deposits of sand and grave!, as dering pattern, indicating competency on the part well as permeable rocks including those in which of the stream to transport available bed load the permeability is the result of fractures, readily (Leopold and Wolman, 1957, p. 39); and the absorb precipitation. Therefore, they have few braided pattern, indicating an inability to handle surface streams and display a coarse drainage bed load.4 Alternate meandering and braided texture. The pattern may be fmer on steep slopes, reaches, therefore, suggest local differences in the however, where velocity of flow results in re texture of the materials being supplied to the duced infiltration and greater surface runoff. stream and may indicate alternate exposures of Clay, with a low inftltration capacity, has a large surface runoff and a dense network of surface Detailed discussions of floodplain stream patterns appear in Melton (1936) and Russell (1939). drainage. •
2256
ARTHUR DAVID HOWARD
unlike materials. Misfit meandering streams, in which the dimensions of the meanders do not agree with those of meander scars or of flood plain scrolls, suggest geologic or climatic change. The sickle pattern displays sorne arcuate curves and is most common in areas of plutonic rocks and migmatites. The barbed pattern indicates ei ther piracy or the presence of joints, faults, or layers of weak rock trending obliquely across the path of the stream. The term "beaded" has been applied to streams in the subarctic along which small thaw sinks are present at irregular inter vals. Successions of beaver dams give a superficially similar pattern, as do, on a !arger scale, strings of glacial lakes. The writer has named a new pattern, spatulate, which could be included under beaded, but which he believes is distinctive enough to warrant a sep arate designation. In essence, it consists of alter nate broad valley segments and narrow defi!es. The pattern is displayed by sorne of the valleys, such as the Aragva, that drain south from the Caucasus in southern Russia. The Aragva and its sister streams pass intermittently through resis tant and weak Cretaceous sedimentary rocks (Renngarten, 1937, p. 104). The streams are re stricted to defiles where the more resistant car bonate rocks of the Upper Cretaceous are brought down to river leve! in the troughs of synclines, but they meander in broad open reaches in the weaker, sandy-argillaceous Lower Creta ceous sediments of the anticlinal cores. The defilcs and open reaches range in length from 0.5 to 2 mi or more. The pattern is quite regular in these open folds, with the broad, elongate seg ments occurring at uniform intervals along the valley. Other spatulate patterns may have no structur al significance. The spatulate pattern displayed by the Missouri River in eastern Montana and west ern North Dakota is glacial in origin (Howard, 1958). The Missouri trench is locally 1 mi or less in width; in intervening areas its width may ex ceed 4 mi. The narrow segments represent ice marginal paths cut across former divides, whereas the broad elongate segments represent parts of preglacial vaUeys. The pattern is irregu lar in that the broad segments inherit their trends from an ancestral drainage whose trends were opposed to tbe tvend of the ice front. Thus the broad segments are considerably· varied in
orientation and are irregularly distributed along the present valley. DRAINAGE ANOMALIES
Anomalies in dra;nage patterns and in the pat terns of individual streams have been the subject of discussion in recent years. They are of partic ular importance in the flatlands. The analysis of drainage may provide clues to structural features undetectable by other methods.
A drainage anomaly can be defined as a local deviation from the regional drainage and/or stream pattern which elsewhere accords with the known regional structure and/or topography. The expectable pattern is regarded as the norm (DeB!ieux, 1949, p. 1253-1254), and the devia tions are anomalies. An alternation of broad val ley segments and narrow defiles along transverse streams in areas in which the structure is known to consist of folded weak and resistant rock is herein regarded as normal, as are sicklelike curves in granite areas. However, in many other geologic environments these phenomena are anomalous. Anomalies suggest structural or topo graphic deviations from the regional plan. Many composite patterns, for example, involve a small enclave of one pattern within another, rather than two adjacent patterns of equal magnitude. An illustration is the local occurrence of radial and annular drainage within a regional dendritic pattern (Fig. 4, A). Many pattern modifications and varieties also involve anomalies as, for exam ple, local parallelism of streams in a dendritic pattern (Fig. 4, B). Many anomalies are localized along individual streams. Sorne of these are listed below. Rectilinearity.-Long, rectilinear segments of
streams, particularly if aligned across divides with rectilinear segments of other streams, con stitute an anomaly if the regional pattern is other than rectangular, angulate, or fault-trellis. A frac ture, or an easily erodable vein or dike is indi cated. In Figure 4C the arrow indicates a recti linear stream. Abrupt and localized appearance of meanders. DeBiieux (1949, p. 1259) has described an inter esting stream anomaly at the Lafitte oil field in Jefferson Parish, about 15 mi south of New Orleans (Fig. 4, D). The channel of an aban doned Mississippi River distributary is relatively straight and simple for severa! miles upstream
DRAINAGE ANALVSIS I'.\J GEOLOGIC INTERPRET:\'1'101\
2257
A. Dendrit ic w,th rodialannular enclave
D. Locol meandering
E
Compressed
meanders
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1
ocal
bro1d1ng
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Anomalous flore in valley
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, \i,c
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J. Variation in levee width
K
F I ying levees
L. Anomalous :::urves ond fu rns 2
'1 Schemotic
\
'.
t
". '{r{¡( /
Schemot1c
Frc. 4.-Examples of drainage anomalies. A. B, C, G---Amazon basin; E Kent County, Texas, after DeBlieux and Shepherd, 1951; D, F, J- Louisiana, after DeBlieux, 1949: Is: Loui,iwa. generalized after DeBlieux, 1940; I-East Africa, after Holmes, 106 ; H, L generalizecl exarnpk,
and downstream from the Lafittc salt dome. At the dome, however, two meanderlikc curves are present. This interruption of thc normal pattern may be related to a subtle upstream reduction in stream gradient caused by the appearanrc of the dome along its path. Compressed meanders.-DeBlieux and Shep herd (1951, p. 98) describecl a strearn pattcrn in which severa! meanders of an otherwise nor mal and continuous series are squeezed, com pressed, and incised (Fig. 4, E). The anomaly. along the Double Mountain Fork of the Brazos River in Kent County, Texas, b at the site of a subsequently demonstrated structural anomaly.
:,¡¡o
explanation oí lhl' anomaly is offered. Mc Kenzie Creek. a tributar) frnm thc south, dis plays an anomalou, rn rq; apparently influenccd by the dome_ Abrupt 11nd lo(alizul hraiding.-DeBlieux (1949, p. 11259 1 reportcd the abrupt and local ap pearance of braidin.E; al cully salt dome in aban doned distributaries of Bayou Lafourche about 30 mi southwect of J\c'A Orlcan,, Fig. -1. F). Braiding gene rally indicares inability o i a stream to trans port il, bed load I Lrnpolrl and \Volman, 1957, p. 50). Inability rnay result frnm !oral acquisition of a rnarser loacl than th,· .,trearn is competent to handle. los, of \·olum,· due to locally increased
2258
ARTHUR DAVID
HOWARD
underflow, loss of velocity caused by flattening of along the Mississippi River are narrower in sorne the gradient (perhaps by a rising structure), or places than others. He suggested that subsidence sorne other geologic or hy
DRAINAGE ANALYSIS IN GEOLOGIC INTERPRETATION SUMMARY
Drainage analysis may provide information on structural features and type of materials. The analysis should consider not only basic patterns, but also modified basic patterns, pattern varieties, drainage texture, stream patterns, and anomalies. The drainage patterns, individually and in com bination, provide a certain amount of information which, in the flatlands at least, may not be ob tainable by ordinary field methods. The palimp sest pattern is of special interest inasmuch as it may indicate currerÍt tectonic activity. Drainage texture within any one small area in which climate, topography, and erosional history are reasonably constant commonly may be indica tive oí the permeability of materials or of the size oí particles provided by weathering. Individual stream patterns may provide infor mation on structural features, rock type, hydrau lic conditions, or geomorphic changes.
Drainage anomalies may provide information on local structural features, active deformation, differential subsidence, or changes in the hydrolo gic regimen. REFERENCES CITED
Cooper, W. S., 1935, The history of upper Mississippi River in late Wisconsin and postglacíal time: Minn. Geol. Survey Bull., v. 26, 116 p. Dake, C. L., and J. S. Brown, 1925, Interpretation of topographic and geologic maps: New York, Mc Graw-HiH, 335 p. Daubrée, A., 1879, Geologie expérimentale: Paris, Dunod, p. 357-375. Davis, W. M., 1889, Rivers and valleys of Pennsylva nia: Natl. Geog. Mag., v. 1, p. 183-253. DeB!ieux, C. W., 1949, Photogeology in Gulf Coast exploration: Am. Assoc. Petroleum Geologists Bull., v. 33, p. 1251-1259. -and G. F. Shepherd, 1951, Photogeologic study in Kent County, Texas: Oil and Gas J our., v. 50, no. 10, p. 86 , 88, 98-100. Dutton, C. E., 1882, Tertiary history of the Grand Canyon district: U.S. Geol. Survey Mon. 2, 422 p. Engeln, O. D. von, 1942, Geomorphology: New York, Macmi!lan, 655 p. Finch, V. C., and G. T. Trewartha, 1936, Elements of geography, 1st ed.: New York, McGraw-Hill, p. 307,342,355. --and --1942, Elements oi geography 2d ed.: New York, McGraw-Hill, p. 290, 326, 340. Hobbs, W. H., 1904, Lineaments of the Atlantic bor der regían: Geol. Soc. America Bull., v. 15, p. 483-
S06.
Holmes, Arthur, 1965, Principies of physical geology, 2d ed: Kew York, Ronald Press, p. 1058. Horton, R. E., 1945, Erosiona]
development
of
2259
streams and their drainage basins : Hydrophysical approach to quantitative morphology: Geol. Soc. America Bu!!., v. 56, p. 275-370.
Howard, '.A. D., 1958, Drainage evolution in north
eastern Montana and northwestern North Dakota: Geol. Soc, America Bull., v. 69, p. 575-588.
--1962, Palimpsest drainage and Chungchou photogeologic anomaly, Taiwan: Am. Assoc. Pe troleum Geologists Bull., v. 46, p. 2255-2258.
--1965, Photogeological interpretation of structure in the Amazon basin, a test study: Geol. Soc. America Bu!!., v. 76, p. 385-406. Jaggar, T. A., Jr., 1901, The laccoliths of the Black Hills: U.S. Geol. Survey, 21st ann. rept., pt. 3, p. 163-303. Johnson; Douglas, 1932, Streams .and their signifi cance: Jour. Geol., v. 40, p. 481-497. Kemp, J. F., 1894, Preliminary report on the geology of Essex County [N.Y.]: New York State Geol. Survey, ann. rept. 1893, p. 431-472. King, L. C., 1951, South African scenery: London, Oliver and Boyd, 379 p. Leopold, L. B., and M. G. Wolman, 1957, River chan nel patterns: braided, meandering, and straight: U.S. Geolfl Survey Prof. Paper 282, p. 39-85.
Melton, F. A., 1936, An empírica! classification of flood plain streams: Geog. Rev., v. 26, p. 593-609. Merriam, D. F., and P. H. A. Sneath, 1966, Quantita tive comparison of contour maps: Jour. Geophys,
Research, v. 71, p. 1105-1115. Muller, S. W., 1943, Permafrost or permanently fro zen ground and related problems: U.S. Engineers Office, Strategic Eng. Study Spec, Rept. no. 62, 136 p, Parvis, Merle, 1950, Drainage pattern significance in airphoto identification of soils and bedrock : Highway Research Board, Natl. Research Coun cil Bull. 28, p. 36-62.
Renngarten, V., 1937, La route militaire de Géorgie:
17th Internat, Geol. Congress. U.S.S.R., Excur sion au Caucase, Rostov-Tbilisi, p. 70-113. Russell, I. C., 1898, Rivers of North America: New York, G.P. Putnam, 327 p. Russell, R. J., 1939, Louisiana stream patterns: Am. Assoc. Petroleum Geologists Bull., v. 23, p. 11991227. Schumm, S. A., 1956, Evolution of drainage systems and slopes in badlands at Perth Amboy, New Jersey: Geol. Soc. America BuU., v. 67, p. 597646. Smith, K. G., 1950, Standards of grading texture of erosiona! topography: Am. Jour. Sci., v. 248, p. 655-668. Tator, B. A., 1954, Drainage anomalies in coastal plain regions: Photogramm, Eng., v. 20, p. 412417. Whitehouse, F. W., 1944, The natural drainage of sorne very flat monosoonal lands (western Queens land, Australia): The Australian Geographer, June, 1944, p. 3-16. Willis, Bailey, 1895, The northern Applachians: Natl. Geog. Soc. Mon., v. 1, no. 6, p. 169 -202. Zernitz, Emilie R., 1932, Drainage patterns and their significance: Jour. Geol., v. 40, p. 498-521. Zonneveld, J. I. S., et al., 1952, The use of aerial pho tographs in a tropical country (Surinam): Pho togramm. Eng., v. 18, p. 144-168.
