907 ID: 354148
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, 907 926 (2004) , 907 926 (2004) KEY WORDS:hypsometry; glacial erosion; glaciated landscapes * Correspondence to: S. H. Brocklehurst, Department of Earth Sciences, The University of Manchester, Manchester, M13 9PL, UK.E-mail: shb@man.ac.uk , 907 926 (2004)We carried out a comprehensive series of analyses to assess the inuences of the degree of glaciation, theglaciated landscapes. We selected eld sites in the western USA and the South Island of New Zealand in order , 907 926 (2004)(i)Hypsometry is an effective indicator of long-term degree of glaciation.(ii)The position of the ELA within the drainage basin relief has a signicant inuence on the hypsometry of(iii)The hypsometry of large, arbitrary regions can mask the detail and variation shown by individual drainage(iv)Unique local circumstances, such as the presence of iceelds and hanging valleys, can have a profoundWe employed two different methods for analysing hypsometry. The rst method (e.g. Figure 2a c) is a simpleobscuring the signal with scatter in the data with too small a bin size. In practice, we found a 100m bin size maxminanalyses within the USA were carried out using 30m digital elevation models (DEMs) from the USGS, whereasfor the New Zealand examples we used a 50m DEM from TerraLink.0·2mm/yr (Gillespie, 1982). The principal lithologies of the western side of the Sangre de CristoNormal faulting slip rates along the range front in the region of interest have averaged around 0·1 0·2mm/yr , 907 926 (2004) Figure 1.(a) Shaded relief map of drainage basins studied in the eastern Sierra Nevada, California. Location of study site show0·8mm/yr (Tippett and Kamp, 1995a, b) agree well with uplift rates of , 907 926 (2004)maximum (LGM) contained glaciers extending to the range front. The extent of glaciation at the LGM in the Figure 1.(continued , 907 926 (2004)the Sierra Nevada. We followed the same hypsometric methods summarized above, and compared the resultsiceeld, by looking at the hypsometry of basins draining the west side of Mt Cook in the Southern Alps of Figure 1.(continued , 907 926 (2004) Figure 2.Hypsometry of the eastern Sierra Nevada. Modern (dashed) and Last Glacial Maximum (dotted) regional equilibrium line adevelopmentofNevada (Brocklehurst and Whipple, 2002), with hyposmetric integrals given for Table I. We highlight threecurve plot (Figure 2d). In Figure 2a c, the dashed grey lines illustrate the modern and LGM ELAs for eachdrainage basin taken from regional trends (Burbank, 1991). We took ELAs determined using the accumulation , 907 926 (2004)Table I.Summary of Sierra Nevada hypsometry data. Basins listed in alphabetical order. Mean BasinDegree of glaciationHypsometric integral AlabamaNone0·452BlackNone0·532InyoNone0·427PinyonNone0·485South Fork, LubkenNone0·396SymmesNone0·491DiazMinor0·531DivisionMinor0·592ThibautMinor0·443BairsModerate0·478GoodaleModerate0·607HogbackModerate0·521North Fork, BairsModerate0·448North Fork, LubkenModerate0·532Red MountainModerate0·532ArmstrongSignicant0·533GeorgeSignicant0·589North Fork, OakSignicant0·590SardineSignicant0·581SawmillSignicant0·590ShepherdSignicant0·552TabooseSignicant0·569TuttleSignicant0·542BirchFull0·567IndependenceFull0·563Lone PineFull0·575South Fork, OakFull0·589TinemahaFull0·624 before, Figure 3a c illustrate, with dashed grey lines, modern and LGM ELAs from regional trends (Richmond,In comparison with the Sierra Nevada, the Ben Ohau Range has a much stronger gradient in ELA (bothcurrentof the range, to near the crest of the range in the south, as shown by the dashed grey lines in Figure 4a c (Porter, , 907 926 (2004) Figure 3.Hypsometry of the Sangre de Cristo Range. Modern (dashed) and LGM (dotted) regional ELAs for the crest of the range frand western Sangre de Cristos compared with the Ben Ohau Range. We suggest that this is due to the positionWe have attempted to quantify the relative ELA position within the total elevation range of the basin using ELAELAzELAELAmidway between the modern and LGM ELAs (Porter, 1989), ELA , 907 926 (2004)Table II.Summary of Sangre de Cristos hypsometry data. Basins listed in alphabetical order. BasinDegree of glaciationHypsometric integral AlpineNone0·449BurntNone0·437Cedar CanyonNone0·502ColdNone0·401CopperNone0·395DimickNone0·423Hot SpringsNone0·463LimeNone0·500Little MedanoNone0·471MarshallNone0·411MillNone0·523OrientNone0·447ShortNone0·439SteelNone0·510CedarPartial0·533CottonwoodPartial0·516DeadmanPartial0·542GarnerPartial0·432MajorPartial0·432MedanoPartial0·388North CrestonePartial0·532PolePartial0·479SandPartial0·511San IsabelPartial0·558SpanishPartial0·503Wild CherryPartial0·518BlackFull0·469CottonFull0·538Rito AltoFull0·569South CrestoneFull0·483WillowFull0·521 examples of each of the study areas. In each case the LGM glaciers extended at least to the range front, but as , 907 926 (2004) Figure 4.Hypsometry of the Ben Ohau Range. Modern (dashed, grey) and LGM (dotted, grey) regional ELAs for the crest of the rangTable III.Summary of Ben Ohau Range hypsometry data. Basins are listed from south to BasinDegree of glaciationHypsometric integral Darts BushMinor0·523FraserMinor0·519DryMinor0·524GladstoneMinor0·504McMillanMinor0·534Top McMillanMinor0·516MackenzieMinor0·482DuncanMinor0·493BoundaryMinor0·501JacksModerate0·534WhaleModerate0·483TwinModerate0·492Dead HorseModerate0·485BushModerate0·459FredsFull0·466Birch HillFull0·449HoophornFull0·394SawyerFull0·465Black BirchFull0·438 , 907 926 (2004)lies immediately to the south of Callery River (Figure 7b) in the Mt Cook region of the Southern Alps. The two Figure 5.Comparative hypsometries from the western USA. Note varying regional ELA positions; modern (dashed, grey) and LGM (dot , 907 926 (2004)precipitation increases, causing the ELA to fall, the rst stage of glaciation is the formationof a cirque glacier,Table IV.Summary of hypsometry data for other fully glaciated basins in the western BasinRangeHypsometric integral LincolnGlacier National Park0·292HarrisonGlacier National Park0·408WaltonGlacier National Park0·329GrinnellGlacier National Park0·334SwiftGlacier National Park0·344IcebergGlacier National Park0·364SpragueGlacier National Park0·396SnyderGlacier National Park0·411MineralGlacier National Park0·433MillBitterroots0·520BlodgettBitterroots0·510Fred BurrBitterroots0·514SawtoothBitterroots0·508Roaring LionBitterroots0·527RockBitterroots0·438Tin CupBitterroots0·463 , 907 926 (2004) Figure 6.Hypsometry of a large portion of the study region in the eastern Sierra Nevada. (a) Digital elevation model of selecteBairs (medium grey, partially glaciated), and Lone Pine (light grey, fully glaciated) Creeks, taken from Figure 2a c. (c) Hypso , 907 926 (2004)50km), only two of the three styles oflandscape is brought down to lower elevations, culminating in monadnock landscapes with few peakssurroundedis necessary. Local circumstances can inuence hypsometry, sometimes in quite profound ways. Hangingvalleys, Figure 7.Hypsometry of neighbouring basins on the western side of the Southern Alps. Modern (dashed) and LGM (dotted) ELAs from , 907 926 (2004) Figure 8.(a) Digital elevation model of Avalanche Creek, Glacier National Park. Notice how the two tributaries are hanging vallFigure 9.Hypsometric curves for Sawmill Creek (black) and Taboose Creek (grey) in the eastern Sierra Nevada (Figure 2a). Sawmil , 907 926 (2004)can extend to lower in the basin. We caution that the initial condition for this landscape may have been a rising Figure 10.(a) Longitudinal prole of Baker Creek, eastern Sierra Nevada, emphasizing the low relief of the Coyote warp. (b) Fre3100m reects the large, low-relief extent of the Coyote warp, while the3600m reects the cirque oors above this. (c) Hypsometric curves for Baker Creek (black) and nearby Red Mountain , 907 926 (2004) Figure 11.(a) Cartoon to illustrate effects of progressive glacial modication of an initial uvial landscape (dark grey). InitWe have carried out a broad survey of the hypsometry of glaciated landscapes. Both the frequency distributionbasins. We have identied a continuous spectrum of frequency distributions of elevations and hypsometricvalley glaciers as the major inuence on the landscape is reminiscent of the classic uvial landscapedevelopment , 907 926 (2004)presence of ice-caps, major hanging valleys, narrow outlet canyons, and isolated geologic structures, canintroduce329 339.: 282 1 24.: 294 306.: 799 808.. USGS Miscellaneous Field Studies Map MF-1635-B.: 59 64.(ed.). Geological Society of America: 353 356.27 47.: 245 261. , 907 926 (2004)University Press: Princeton, NJ; 217 230.: 597 646.: 109 121.: 123 126.: 115 141.: 153 175.: 169 190.: 39 43.: 611 623.