212Erdkunde Band 30/1976

THE NATURE OF HIGHLAND VALLEYS, CENTRAL With 2 figuresanc^ 2 photos

R. J. Blong and C. F. Pain

Zusammen assung: Die der Hochlandtaler over a area now j Morphogenese wider (Fig. 1) allow re-examination von Central Neu-Guinea. Papua, of the nature of Papua New Guinea highland valleys. Bik andeutete, dafi die des Obgleich (1967) Bergtaler In order to test the hypothesis that the superficial Papua Neu Guinea-Hochlandes oberflachlich den von Louis resemblance between the Papua New Guinea highland beschriebenen ?Flachmuldentalern mit Rah (1957, 1964) and Louis' Flachmuldentdler mit Rahmenhd menhohen" sind erst valleys gleichen, eingehende Untersuchungen hen ismore to kurzlich unternommen worden. than justmorphological, it is necessary the nature and of on the Die Hangfufibereiche in einer Anzahl von Talern erge study age deposits valley ben sich aus dem fortwahrenden Zuwachs von tonreichen slopes and floors; in particular it is necessary to show whether or not the floors are erosio Sedimenten oder aus der spatpleistozanen kolluvialen Ab valley and slopes lagerung. In nahezu jedem untersuchten Tal haben vulkani nal features. zu sche Ablagerungen bis mehreren hundert Metern Dicke die vorher V-formigen Talboden aufgefiillt. In einigen Ta lern setzt sich die Auffiillung mit lakustrischen, organischen Valley footslopes und fluviatilen Sedimenten, die vor mehr als 50 000 Jahren With reference to the Andabare Plain, Bik writes: begann, bis zum heutigen Tage fort. Die machtige Auf . . where the often abut the schuttung und fortlaufende Ablagerung erlaubt die Zuriick footslopes against stream the former are of weisung von Bik's Vorstellung, dafi die Talboden und channels, certainly slopes aus of waste. Hangfufibereiche Erosionsflachen sein konnten, ererbt transport weathering However, sheetwash, as der pleistozanen Absenkung morphoklimatischer Zonen. postulated by Louis the transporting agent, does not on area operate the well vegetated slopes in the In a 1967 with zo essay dealing morphoclimatic of study. In fact the mechanism of waste transport nation of landforms in the central of highlands Papua across gentle footslopes at these altitudes (c. 2525 m) New M. Bik out that the intra Guinea, J. J. pointed is not at all clear, and the subject deserves detailed montane of the and Wasu to plains Andabare, Kandep, research, especially determine whether transport resemble the 'hill-bor ma-Kagua valleys superficially occurs at all at present. If it does occur, as it is dered which Louis saucer-shaped valleys' (1964) known to do above 2500 m, these footslopes are Flachmuldentdler mit Rahmenhdhen designated (Bik, active surfaces of 'ramp-slope' nature. If transport 1967, p. 44). Bik noted that the Papua New Guinea does not occur below this level, could such surfaces are characterized wide central alluvial flats valleys by be inherited features resulting from Pleistocene low concave of l?-3? with rather short footslopes abutting ering of themorphoclimatic zones?' at of 25?-35?. against steep valley sides rising angles (Bik, 1967, p. 45) Implicit in theFlachmulden concept is the notion of long continued erosion under conditions of tectonic stability, rapid weathering and effective subaerial At Kuk Tea Research Station, on the southern foot denudation. The landscape is essentially erosional, the slopes of Ep Ridge, in the centre of the upper Wahgi res valley floor and the ramp slopes (Rampenhang) Valley (Fig. 1), a series of shallow trenches250 m long pectively exhibiting a superficial veneer of transported reveals the footslope stratigraphy. Ep Ridge itself is sediment and a deep residual soil (Bik, 1967; Louis, an outlier of pre-Permian metagreywacke and phyllite 1957; 1964). and Jurassic tuffaceous sandstones and siltstones (Bain On the other hand, A. Guilcher (1970) believed et al.9 1970). These materials are deeply weathered, were the morphological development of the Lake Iviva and mantled during the Late Pleistocene by centres. (Sirunki) depression resulted from continued Quater tephras from Mount Hagen and other eruptive nary tectonism and infillingof the basin with swamp Much of the tephra mantle has subsequently been sediments.Guilcher also postulates that ponding and stripped from the ridge. on fluvial deposition of theAndabare, Kandep and Mari Some exposures the footslopes reveal mudflow ent basins result from tectonism. sediments composed of slightlyweathered angular to comments clasts in a matrix. Although Bik and Guilcher restrict their subangular clayey, tephra-derived, which is sel on basin morphology to only a few valleys, their Buried soils underlie themudflow debris, to dom more than 1 m thick. most descriptions of surface form are equally applicable However, exposures on reveal unbedded de other highland valleys including the upper Wahgi low the footslopes only clay at some lenses of re (particularly theGumants), the upper Kaugel, and the posits, separated sites by thin units The lowerNembi valley around Poroma (Fig. 1 and Photo worked but identifiable tephra (Fig. 2). the of numer 1).Recent detailed stratigraphie studies of theGumants stratigraphy is complicated by presence observations ous drains and other evidence of and Kaugel Valleys, and reconnaissance prehistoric early Hi

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a Kuk Tea Research Station Fig. 2: Cross-section through the lower portion of footslope, Ep Ridge,

stream agriculture (Golson, 1974). In the upper part of the provided by incision reveal bedded weathered to to of at least 6 m. trench the clay-rich sediments extend the surface. subrounded gravels depths Again, As some drains have been filled to the surface with the landforms as well as the deposits are characteristic occur on the northern clay-rich sediments, and the drains are known by of alluvial fans. Similar deposits the lower tephrochronology to date from about 250 years BP, margin of the Gumants Basin and flanking In a it is evident that clay sedimentation has continued to portions of the Sepik-Wahgi Divide. borehole a on 14.5 m the present time. through footslope (D 12 Fig. 1) of grav on a at Other thin tephra units, ranging in age from c. 1,100 elly fan deposits sit peat dated 13,000 years to more than 11,000 years BP and parallelling the BP. can at a number In and present footslope surface, be identified the upper Kaugel Valley (Fig. 1) footslopes a narrow of sites down the slope (Fig. 2), though the tephra fans with slope angles up to 8? occupy strip remnants are not always in situ. As the tephra unit between the valley floor and the commanding slopes are two to note these more than 11,000 years old occurs at a depth of less (Photo2). There points about slo are at and than 1.4 m, and as clay-rich and organic sediments pes. Firstly, they nearly all incised present, are more than 3.5 m thick, accretion spans at least degradation is confined to the floors of channelswhich ex traverse it has been demonstrated post-glacial time. It is evident that the footslopes the slopes. Secondly, owe amined have been accreting slowly for a lengthyperi that both the footslopes and the fans their origin in od of time, and deposition is not balanced by erosion. to colluvial deposition (Pain, 1973; 1975). Thus, Thus, the southern side of Ep Ridge is flanked by a common with the footslopes of Ep Ridge and the are not ero series of slowly-accumulating, coalescing alluvial (and Gumants Basin, the Kaugel Valley forms landforms are sional in places colluvial) fans. Such not'ramp 'ramp-slopes'. slopes' in the sense of Louis' (1964) Rampenhang. In the Yumbis-Karekare Basin (c. 2,500 m, upper - one a On the northern side of Ep Ridge footslopes of Wage Valley Fig. 1) at least exposure through m l?-3? drain to theGumants Basin, Various exposures trenched footslope indicates that 0.5 of fine sediment R. J. Blong and C. F. Pain: The Nature of Highland Valleys, Central Papua New Guinea 215

Photo 1: The infilled valley of the Gumants River. The Gumants and its tributaries have well-developed levees with are extensive accreting backswamps. Low-angle footslopes and alluvial fans still accumulating sediment.

Photo 2: An infilled basin of the Upper Kaugel Valley. Low-angle footslopes result from colluvial deposition. has accumulated since the deposition of a thin tephra Blong, in press) indicate that the uppermost tephra in unit only 250 years old. theKandep area is theTomba Tephra of Pain (1973), Bik notes that the gentle footslopes in theKandep erupted fromMount Hagen, and now believed to be Plain are mantled by tephra which makes it difficult more than 50,000 years BP. Thus, if the footslope sur to determinewhether the surface is degradational (Bik, face is degradational, it is being degraded by excep the 1967, p. 44). Reconnaissance observations (Pain and tionally slow processes. Furthermore, presence of 216 Erdkunde Band 30/1976

Tomba Tephra at the surface on Kandep footslopes at deposits to form the aggraded surface on which Poro an elevation of about 2,225 m is in contrast to its ma is built. The surface is capped with Bune Tephra, removal or burial by at least 3.5 m of sediment on shown by Pain and Blong (in press) to be coeval Wahgi Valley footslopes at c. 1,500 m. No morpho with Tomba Tephra and hence believed to be more climatic significance can be attached to this observation than 50,000 years old. until further reports on the age and rates of erosion/ At Margarima (2,100 m) in theWage Valley (Fig. 1) deposition on valley footslopes become available. exposures show that this valley and its tributaries, the Margarima Valley and the lower Andebare Valley, have been filled by at least 80 m of volcanic predomi floors Valley nantly laharic) deposits derived from Doma Peaks. The has shifted eastward in its Bik notes that to a of 2 m in Wage apparently valley (1967) augering depth at contact Margarima and incised along the between the central portions of the plains which he investigated the valley wall limestone and the volcanic infill. revealed only alluvium. Levees with clastic sediments Against thewestern valley wall, the lowerMargarima occur along some river channels, with peat, keeping River flows southward in a site thatwas once part of pace with river accretion, growing in backswamps theWage Valley. which rise away from the river (Bik, 1967, p. 44; Jennings, 1963). Thus, Bik was unable to determine or were whether not the plains erosional. Conclusions A recent series of boreholes across the Gumants some Basin nowhere reaches bedrock or even in situ weath Valleyside footslopes are, at least in cases, either Pleistocene alluvial and colluvial ered material despite attaining depths of nearly 40 m. largely fans, or fans with Details of the stratigraphy are to be considered else slowly accreting clay-rich alluvial depo at In none where, but the deposits include fluviatile, lacustrine, sition continuing the present time. of the so far examined can the landforms volcanic (laharic), and organogenic sediments. Car valleys footslopes to bon-14 dating of sediments indicates that, at some sites, be considered result from erosional processes. Long continued evolution of the even 10m below the surface,wood samples are beyond deposition dominates the alluviation and contin the range of radiocarbon assay. footslopes. Furthermore, deep at some Similarly, in the upper Kaugel Valley, Pain (1973) uing deposition, least at sites, allow the rejec has demonstrated that the Flachmulden landforms are tion of Bik's (1967, p. 45) suggestion that the surfaces underlain by considerable depths (up to 250 m) of could be inherited features resulting from Pleistocene zones. colluvial, lacustrine, and volcanic sediments, which lowering of morphoclimatic infilled a series of lake basins created by volcanic Although many of the valleys of the central Papua dams formed during eruptive activity from Mount superficially resemble theFlach Giluwe. Here the tephra mantling much of the infill muldentaler mit Rahmenhdhen described by Louis surfaces is again Tomba Tephra, demonstrating the (1964), stratigraphie examinations reveal that many mo are antiquity of much of the valley floor. Moreover, valley floors underlain by considerable thicknesses dification of the valley floor since the deposition of of volcanic, fluvial, lacustrine, and other sediments. Tomba Tephra has resulted from colluvial deposition These sediments have infilled, and in some cases are and vertical river incision, neither of which fit the continuing to infill, depressions which have at least two one Flachmulden concept. kinds of origin. On the hand, many initially At Sirunki, a flat floored basin surrounded by foot V-shaped valleys (Kerbtal) were dammed by Pleisto slopes and draining to the Lai (Fig. 1), D. Walker cene volcanic activity; these include the Tari-Koroba has obtained a peat core more than 22 m in length Basins, the upper Kaugel Basins, the Saka andWabag from the basin floor; this core covers more than 30,000 Wapenamanda Basin, the Gogimp Basin, the lower years of the basin's history (Walker, 1970). Broad Nembi-Ka area near Poroma, and the Wage-Marga m rima-Andebare area near In the valleys near Tari and Koroba have more than 40 junction Margarima. areas of sediment exposed by trenches incised into their upper Kaugel, Tari-Koroba, and lower Nembi floors, and carbon-14 ages of more than 30,000 years at least, infillinghas taken place partly in lakes pon have been obtained from samples only 5 m below the ded by volcanic deposits. Damming of the Kandep Andebare also infill surface (Williams et al., 1972). and Marient and the upper valleys may can on Other valleys with Flachmulden forms have been have followed volcanism, but firm conclusions more detailed work. the deeply trenched by river downcutting leaving only ly follow Similarly, infilling isolated remnants of flat floors with gentle marginal of the Gumants as a consequence of volcanism and at reversal as footslopes. The mission and airstrip Poroma (Fig. 1) drainage proposed by Haantjens (1970, more 200 m cannot be On the other in sit on one such remnant, perched than p. 22) yet proved. hand, to above the Ka River. Good exposures on the new Men filling of the Sirunki Basin is believed follow warp recent movement on the di-Poroma road reveal that the valley of theKa River ing associated with Lagaip zone Dow was filled by at least 200 m of agglomerate and lahar Fault (Guilcher, 1970; et al., 1972, p. 75). Heinz King: Ober die Auswirkungen des projektierten Hamburger Vorhafenbaus 217

and in the In no case can erosion be sustained as a cause of valley Golson, J.: Archaeology agricultural history New Guinea floor formation. Highlands (in press). are al A.: dans les mon Although continuing tectonic adjustments Guilcher, Neo-tectonique Quaternaire Ocean Acta Geo most certainly occuring over wide areas of the high tagues de Nouvelle-Guinea, Pacifique, 1970. lands considered here, it is evident that the majority graphica Lodzieinsia, 24, p. 197-203, of basin forms resultprimarily not from eitherQuater Haantjens, H. A.: Lands of the Goroka-Mount Hagen and New Land re nary tectonism or the development of Flachmulden area, Territory of Papua Guinea, asso search Series No. 27, CSIRO, , 159 pages, 1970. landforms, but from Quaternary volcanism and ciated sedimentation. Jennings, J. N.: Floodplain lakes in the Ka Valley, Au stralian New Guinea, 129, p. 187? Acknowledgements Geographical Journal 1963. Financial support for fieldwork has been provided 190, byMacquarie University, theWahgi Project (Professor Louis, H.: Rumpfflachenproblem, Erosionszyklus und Kli as: J. Golson, Australian National University), and the mamorphologie. Translated The problem of erosion and of Bio surfaces, cycles of erosion and climatic geomorphology, Myer Foundation (RJB) theDepartment - in: E. (Editor) Climatic Geomorphology, geography and Geomorphology, Australian National Derbyshire, Macmillan Geographical Reading Series (1973), p. 153 Professor J.N. Jennings,Australian University (CFP). 170, 1957. National and Dr. E. CSIRO Land University, Loffler, - : Ober Rampfflachen- und Talbildung in den wechsel Use Research, kindly made comments on a draft of feuchten Tropen besonders nach Studien in Tanganykia. the manuscript. Zeitschrift fiir Geomorphologie 8, p. 43-70, 1964.

Pain, C. R: The late Quaternary geomorphic history of References the Kaugel Valley, Papua New Guinea. Unpublished PhD thesis, Australian National University, 225 pages, R. Bain, J. H. C, Mackenzie, D. E. and Ryburn, J.: 1973. Geology of the Kubor anticline, central highlands, New - - : The Kaugel Diamicton a Late Quaternary mudflow Guinea. Bureau of Mineral Resources, Geology and deposit in the Kaugel Valley, Papua New Guinea. Zeit Geophysics, Australia, Record 1970/79 (unpublished), schrift fiir p. 430-442, 1975. 1970. Geomorphologie, 19(4), - and Blong, R. J.: Late Quaternary tephras around Bik, M. J. J.: Structural geomorphology and morphocli Mount Hagen and , Papua New Guinea matic zonation in the central highlands, Australian in Johnson, R. W. (editor), Quaternary volcanism in New Guinea, in: Jennings, J. N. and Mabbutt, J. A. - Australasia, Elsevier (in press). (Editors) Landform studies from Australia and New Guinea, Australian National University Press, p. 26-47, Walker, D.: The changing vegetation of the montane tro 1967. pics, Search, 1(5), 217-222, 1970 D. A. H. C. Dow, B., Smit, J. J., Bain, J. and Ryburn, Williams, P. W., McDougall, I. and Powell, J. M.: R. J.: Geology of the South Sepik Region, New Guinea. Aspects of the Quaternary geology of the Tari- Koroba Bureau Mineral Resources of Bulletin 133, Bull. PNG 4, Area, Papua, Journal, Geological Society, Australia, 88 pages, 1972. 18(4), p. 333-47, 1972.

BERICHTE UND KLEINE M ITTE ILU N G E N

Ober die auswirkungen des projektierten hamburger vorhafenbaus im watt sodlich des elbeastuars

Ein Beitrag zur Angewandten Kustenmorphologie Mit 2 Abbildungen Heinz Klug

Summary: Geomorphological effects of the projected the tidal flats off Cuxhaven. An attempt has been made construction of an outer in the tidal flats of Cux to record assess port and these by relating the connections indi haven. cated by the present dynamics and development to the The an outer projected construction of port of Hamburg changed marginal conditions after the construction of the and its connection a dam with the mainland would as by planned building-work, identified by model-based in lead to far-reaching hydrological-morphological changes in vestigations.