CONTROLS ON RIVER TERRACE FORMATION IN NEW ZEALAND Recibido:2007-01-02 Aceptado:2007-02-02 ©Angel SORIA JAUREGUI* ©Gary BRIERLEY**
*Departamento de Geografía, Prehistoria y Arqueología Universidad del País Vasco C/ Tomás y Valiente s/n 01006 Vitoria-Gasteiz
**Chair of Physical Geography School of Geography and Environmental Science The University of Auckland 10 Symonds Street Private Bag 92019 Auckland New Zealand
Laburpena Artikulu honek, argitaratutako bibliografiaren bidez, Zeelanda Berriko ibai-terrazen garapenari eragiten dieten agente morfogenetikoak aztertzen ditu. Erreferentzia gisa Ipar Irlako 4 kasu eta Hego Irlako 3 kasu erabili dira. Oro har, ibai-terrazak sortzeko orduan, klima, sedimentuen erabilgarritasunan eta prezipitazioan duen eraginaren bitartez, eragile nagusiena da. Altxaketa tektonikoak forma hauen kontserbazioa eragiten du. Hainbat kasutan, gertaera asaldatzaileen ondorioz sortutako sedimentu kopuru handiek, fase morfogenetiko desberdinak eragin dituzte lokal/erregional mailan, nazional/kontinental mailan beharrean. Gertaera asaldatzaileen artean, besteak beste, ekarpen bolkaniko naturalak eta gizakiok bultzatutako lur erabilera aldaketen ondorioz sortutako sedimentu ekarpenak barneratzen dira. Hitz gakoak: Ibaia, terraza, klima aldaketa, altxaketa tektonikoa, sedimentazioa, ebakidura, sedimentu hornidura, maila oinarriaren aldaketa, ekarpen bolkanikoa, landa erabileraren aldaketak.
Resumen Este artículo analiza los agentes morfogenéticos de las terrazas fluviales en Nueva Zelanda mediante una revisión selectiva de la bibliografía existente. Se han tomado como referencia 4 casos localizados en la Isla del Norte y otros 3 en la Isla del Sur. En términos generales, el control climático sobre la disponibilidad de sedimentos y las precipitaciones ejerce la principal influencia en la génesis de las terrazas fluviales. La conservación de estas formas está influida por el levantamiento tectónico. En ciertos casos, grandes aportaciones de sedimentos generados como consecuencia de eventos perturbadores han provocado diferentes fases morfogenéticas a escala local/regional en lugar de a escala nacional/continental. Ejemplos de estos eventos incluyen aportaciones volcánicas naturales y sedimentarias generadas por la acción del hombre como consecuencia de cambios en los usos del suelo. Palabras clave: Río, terraza, cambio climático, levantamiento tectónico, sedimentación, incisión, suministro sedimentario, cambio de nivel de base, aportación volcánica, cambio en los usos de suelo. Abstract This paper analyses controls on river terrace formation in New Zealand through a selective review of published literature. Emphasis is placed on four case studies from the North Island and three case studies from the South Island. In general terms, climatic controls upon sediment availability and discharge exert the primary influence on terrace formation. The preservation of terraces is influenced by tectonic uplift. In some instances, large inputs of sediment in response to disturbance events have induced differing phases of terrace formation at a local/regional rather than a national/continental scale. Examples of disturbance events include ‘natural’ volcanic inputs and human-induced sediment inputs in response to land use changes. Key words: River, terrace, climate change, tectonic uplift, aggradation, degradation, sediment supply, base level change, volcanic input, land use change.
1. Introduction Sections of river courses that are characterised by pronounced shift in the flow/sediment balance tend to experience phases of sediment accumulation on valley floors (aggradation) and phases of incision (degradation). The topographic expression of these adjustments is marked by flights of alluvial (river) terraces. These features provide significant insights into past environmental changes, guiding our interpretation of geomorphic responses to shifts in the boundary conditions (i.e. tectonic uplift/subsidence, climate change) under which rivers operate. Some boundary conditions shift irregularly at local scales (e.g. uplift along a fault line), while others adjust more systematically at continental scales (e.g. Quaternary climate changes). In order to unravel these differing influences upon river evolution, comparisons between river systems must be made. In this study we perform such an analysis through selective review of the literature on terrace formation in New Zealand – a tectonically uplifting landscape that has been subjected to significant climatic variability in the Quaternary. Prior to characterising the New Zealand landscape setting, controls on terrace formation are briefly outlined.
2. Controls of terrace formation
Fluvial systems are influenced by and react to different external and internal forces which operate at different time and space scales (Maddy et al., 2001; Schumm, 1977; Schumm and Litchty, 1965). The balance between stream power and sediment supply exerts a direct control upon river evolution. Channel beds deposit when sediment supply exceeds maximum bedload transport rates (i.e. aggradation) and incise when the reverse is true (i.e. degradation; Figure 1).
Figure 1. Balance model for aggradation and degradation of alluvial channels. Source: (Chorley et al., 1984).
While in the long term geology and climate are dominant factors; during short-term, modifications in flood incidence (magnitude and frequency) and sediment reworking produce adjustments. Terrace flights are one of the most important responses of a fluvial system. They can be formed in response to either long or short term controls. Merrits et al. (1994) define river terraces as “landforms that were at one time constructed and maintained as the active floor of a river but are now abandoned”. Thus, abandoned fluvial sediments are magnificent geomorphological, ecological and sedimentary archives that reflect the different conditions during their formation (Vandenberghe, 2002). In an idealized fluvial system in which there is a river with permanent flow, temperate climatic regime, headwaters in highlands and base-level localised in the sea/ocean, there is a first stage during which, despite vertical incision, lateral movements produce bank erosion, generating channel widening and the creation of a floodplain (Fig. 2 a/c). In the second phase, vertical incision becomes the leading process, incising the current channel and abandoning the initial floodplain, creating a terrace level (Fig. 2 b/d/e) (Leopold et al., 1964). The shift from lateral incision to vertical downcutting is controlled by a combination of climate change, tectonic activity, base-level change and human activity.
Figure 2. Theoretical genesis of a fluvial terrace. Source: (Leopold et al., 1964).
Factors that influence the formation and preservation of terraces can be differentiated into endogenous and exogenous controls.
2.1. Endogenous Controls Internal controls are intrinsic to a fluvial system and reflect the natural capacity for adjustment of a given landscape (Brierley and Fryirs, 2005; Maddy, 1997). These controls can alter the balance between sediment and discharge, ultimately resulting in a complex response and creation of terrace flights (Womack and Schumm, 1977). Given differences in slope and the prevailing sediment balance along long profiles, terraces in lower reaches are controlled by base-level (sea/ocean) adjustments and tend to have a glacioeustatic origin. Intermediate reach (i.e. transfer zone) terraces have a climatic origin, influenced primarily by the flow/sediment regime. Finally, in the upper reaches where erosion is predominant, terraces have an erosive origin (Pedraza, 1996). Any adjustment to sediment of flow input affects the aggradational/degradational tendency of the river, and hence the generation of terrace features. These processes are mutually interlinked along river courses – upstream incision generates large volumes of sediment that may promote aggradation downstream, whereas upstream aggradation that inhibits sediment transfer to downstream reaches may promote degradation in the latter area. These considerations highlight the importance of catchment-scale perspectives in understanding geomorphic relationships, especially in relation to connectivity notions (e.g.Brierley et al., 2006, in press; Fryirs et al.) In general terms, terrace levels generated in response to internal controls are characterized by their small temporal and spatial extension (Womack and Schumm, 1977), even though these forms might be major features at the local scale (Maddy, 1997).
2.2. Exogenous Controls External controls especially concern mainly climate shifts, tectonic activity or eustasy that affect precipitation, vegetation or base-level that, in turn, affect the dynamic of fluvial systems. Climate changes throughout the Quaternary modified runoff and vegetation cover. Resulting adjustments to the sediment-discharge balance triggered differing phases of aggradational or degradational processes and hence generation of terraces (Bridgland, 2000; Vandenberghe and Maddy, 2001). Eustasy has been long recognised as a major control on river evolution. Incision prevails during cold stages and low sea levels. This is initiated in low lands and extends upstream via knickpoint migration (Maddy, 1997). This situation is reversed during warmer intervals. Tectonic activity rejuvenates a landscape (Davis, 1895) Introduction of a higher energy gradient leads to incision, while areas subjected to subsidence experience prolonged filling. In recent years, other factors such as volcanic activity (e.g. Manville and Wilson, 2004) or human-induced changes in land use (e.g. Kasai et al., 2005) have been shown to influence terrace formation through their modification to sediment availability. Prior to reviewing primary controls on terrace formation in New Zealand, the regional setting is briefly outlined.
3. Regional setting New Zealand is located in the south-western Pacific Ocean, extending from 34030’ to 47030 of latitude. Its two main islands (North Island and South Island) cover an area of almost 270,000 km2, stretching over a distance of approximately 1600 km from North to South. The country is positioned in the south-western edge of the Pacific Ocean. It lies atop the Pacific Mobile Belt, a region of tectonic activity commonly known as the “Ring of Fire”. The Pacific plate, thin and dense, subducts under the Indian-Australian plate; this situation is reversed to the south of South Island (Goff et al., 2003). Given this tectonic setting, the dominant landscape feature of the South Island is the Southern Alps, while active volcanoes are evident in the geothermal region of the North Island. The latitudinal is characterised by the collision of subtropical and polar air masses, resulting in a temperate maritime climate.
4. North Island terraces 4.1. Rangitikei River The Rangitikei River is one of the longest rivers in New Zealand (185 km). From its headwaters in the Kaimanawa Ranges in central North Island, it flows to the south to empty into the Tasman Sea 40 km southeast of Wanganui (Figure 3). This basin has been studied mainly by Te Punga (1952), Milne (1973a; 1973c), Pillans (1994), and Litchfield (2003). Milne (1973a) visualized river aggradation as a response to augmented sediment yields from non vegetated high lands during glacial and stadial times. This relationship is supported by the radiocarbon dating of Ohakea terrace sediments (Table 1; Pillans, 1994), and the existence of subalpine pollen traces in Marton terrace alluvium near present sea level, south of Levin (Palmer et al., 1988). In consequence, it is concluded that geomorphic process responses to climate change triggered the shift from degradational to aggradational events.
Table 1. Age structure of river terraces of the Rangitikei River, based on glass fission-track dating. Source: Pillans, 1994
4.2. Waikato River The Waikato River is the longest in New Zealand (Figure 3). It is located in central North Island. It flows from Mount Ruapehu through Lake Taupo, prior to shifting northwestwards to empty into the Tasman Sea south of Auckland. The river has been studied mainly by Schofield (1965), McGlone et al. (1978) and Manville and Wilson (2004). The Waikato River Catchment was affected by the Oruanui eruption (26.5 ka). This volcanic event, which is the origin of the Kawakawa tephra or Aokautere Ash generated c. 430 km3 of fall deposits, c. 320 km3 of pyroclastic density current (PDC) deposits, and c. 420 km3 of primary intracaldera material (Manville and Wilson, 2004). An aggradation period followed as a consequence of the remobilisation of the volcanic material that fell during the eruption. One of the main sedimentary responses was the avulsion of the Waikato River from the Firth of Thames into the Hamilton Basin. The different fluvial terrace sets are referred to as the “Hinuera Formation” (Table 2). This term relates to sediments younger than the 220 ka Mamaku eruption. These deposits occur in lowlands of both the Hauraki Plains and the Hamilton Basin. The Hinuera Formation was generated by a series of fluvial deposits composed of pyroclastic minerals.
Table 2. Fluvial terraces in Waikato River. Source: Manville and Wilson, 2004.
Climate amelioration around the time of the 17.6 ka Rerewhakaatiu eruption reduced sediment yields from the volcanic hinterland, causing incision of their courses and trapping of the Waikato River into the Hamilton Basin. Hence, aggradational processes along this river were a result of volcanic activity, whereas incision was initiated by climate conditions.
4.3. Wairarapa Valley The Wairarapa Valley (Figure 3) is located in the south-eastern corner of the North Island. Terraces in this are have been studied by Vella (1963), Stevens and Palmer (1986), Palmer and Vucetich (1989), Warnes (1992), Vucetich et al. (1996), Formento-Trigilio et al. (2003) and Litchfield (2003). In general, loess and paleosol age and stratigraphy have been used to differentiate between the terrace levels. The different authors distinguish 3 main loess units: Porewa, Rata and Ohakea. Formento-Trigilio et al (2003) found a younger, partially developed loess which they called the Waiohine loess. Their OSL chronology is presented in Table 3.
Table 3. Fluvial terraces in Wairarapa Valley. Source: Formento-Trigilio et al., 2003
Based on these OSL dates, loess stratigraphy and climate proxy data, climate change is considered to be the main control on terrace formation. At the end of cold periods, conditions became wetter while hillslopes remained poorly vegetated. This increased runoff producing an increment in discharge and sediment yield, provoking aggradation. Nevertheless, it has been concluded that tectonic uplift has been a vital influence upon preservation of the different terrace flights (Formento-Trigilio et al., 2003).
4.4. Weraamaia River Terraces along the Weraamaia River, a tributary of Mangaoporo River (Waiapu catchment), located 10 km from Ruatoria in the North-Eastern Cape of New Zealand (Figure 3) have been studied by Kasai et al. (2005) and Kasai (2006). These studies exemplify the impact of human disturbance upon fluvial systems. Extensive deforestation converted forested areas into pasture in this small catchment. This led to huge problems of erosion (landslides and gully complexes), which prompted corrective measures via reforestation. This situation, coupled with the climate conditions characterized by a mean annual rainfall of 2,400 mm, provoked an increase in the sediment yield, which resulted in widespread aggradation. Reforestation since 1979 has reduced sediment availability. In response, the channel has incised, abandoning former floodplains and creating terrace flights. The relationship among human impacts, vegetation, hillslope and fluvial processes demonstrated in this catchment can be extrapolated to many other systems in New Zealand and elsewhere.
4.5. East Coast Rivers In their review, Litchfield and Berryman (2005) correlate the age structure of fluvial terraces for East Coast rivers on the North Island (Figure 3) using loess stratigraphy and tephrachronology – along with radiocarbon and OSL dating (see Table 4). The reasonable correlation among the catchments hints that the different terrace sets have been formed as a consequence of the same set of controls. They conclude that although tectonic activity prompted the record of terrace preservation, this influence cannot be invoked as the cause of the shift from aggradation to degradation processes. Rather, a model based on climate change is used to account for the shift from aggradation to degradation processes that caused terrace formation. This model is based on various pollen analyses (McGlone, 2001; McGlone, 2002; McLea, 1990) which demonstrated that since the last glacial maximum (LGM), climatic conditions have shifted to warmer and wetter conditions (generating an increased stream power which led to downcutting). During the LGM, climatic conditions were drier and windier. Pollen studies (McGlone, 2001), periglacial features, and the erosion of tephras erupted during or prior to the LGM indicate an increased erosion which would have increased sediment supply. This higher sediment yield, combined with the decline in stream power because of lower discharge under drier climatic conditions, would promote aggradation (Terrace T1). Terraces T2, T3, and T4 are linked to cool climatic phases based on their relationship with loess coverbeds which were deposited under dry and windy conditions characteristic of cold stages.
Table 4. Fluvial terraces in Hirukangi Margin rivers. Source: Litchfield and Berryman, 2005
Litchfield and Berryman (2005) conclude that the influence of base level control is restricted to at least the middle, if not the external shelf. LGM aggradational deposits are preserved up to 20 km offshore, showing that sea level-produced downcutting was restricted. The confluence between the modern floodplain and the LGM floodplain surface, which is the furthest point upstream in which the influence of baselevel during highstands is noticeable, occurs between 8 and 47 km upstream (Litchfield and Berryman, 2005). In summary, it is concluded that even if tectonic activity and changes in base-level have been active factors, they have played a minor role in comparison to the one played by changes in climate conditions.
5. South Island terraces 5.1. Awatere River The Awatere River in the northeast of the South Island is one of Marlborough's four largest rivers. It flows for 110 km from its headwaters to Cook Strait, close to the town of Seddon (Figure 3). Eden (1989) recognized 6 terrace sets of two different types (Table 5). The first type is matched ‘fill’ terraces. According to his model, these features were formed in response to cold climatic conditions which generated high amounts of sediments, provoking aggradation. The stratigraphical position of the Aokatere Ash, deposited 21,000 years B.P. (MIS 2), shows that during that cold climate period, processes of aggradation were predominant. Incision is linked to warm periods. The second type is unmatched ‘cut’ terraces that formed in response to base level change associated with fault displacement after major earthquakes. The importance of tectonics in the preservation of the different terrace flights (uplift rates from 1 to 2 mm/year) is noted, but Eden (1989) concluded that climate has been the major factor affecting aggradational and degradational processes.
Table 5. Fluvial terraces in Awatere river. Source: Eden, 1989.
5.2. Charwell River The Charwell River is located in the northeast of New Zealand's South Island (Figure 3). Its headwaters are situated in the Seaward Kaikoura Range. Bull and Knuepfer (1987) describe 12 remnants of paired terraces, the highest of which is related to an aggradational period while the others are degradational terraces. These terraces were dated by cobble-weathering-rind and soil-profile parameters that were calibrated by radiocarbon dates (Table 6). Climate is considered to be the primary control of terrace formation (Bull and Knuepfer, 1987). During periods of cold climates (25-16 ka), periglacial processes were dominant, providing the fluvial system with increased sediment yield. This, combined with reduced stream power as a consequence of a decrease in rainfall, promoted aggradation. In contrast, warm stages provoked an increase in rainfall (increase in runoff), the return of forests, stabilization of hillslopes, and shift from periglacial to fluvial processes. This increased stream power, which prompted incision (Bull and Knuepfer, 1987).
Table 6. Age estimates of the Charwell River terraces. Source: Bull & Knuepfer, 1987.
5.3. Hurunui River The Hurunui River is located in North Canterbury, South Island. Its catchment comprises an area of 1,640 km2. The headwaters are located in Southern Alps and flows eastward to the Pacific Ocean (Figure 3). Powers (1962) recognised 5 terrace flights, 3 of which have glacial origin, but the processes which formed the other two are currently unknown (Table 7). Once more, this invokes climate factors as the key control on terrace formation.
Table 7. Terraces in Hurunui River. Source: Powers, 1962.
Figure 3. Case study locations with their different terrace levels and age.
6. Discussion
Although a range of factors influence terrace formation in New Zealand, climate change has been shown to be the key control. Climatic conditions alter the vegetation cover over hillslopes. Reduced vegetation cover increases runoff, which in turns leads to high erosion rates and sediment delivery, enhancing aggradation. Hence, the time interval since climate changes affected the system, modifications to vegetation cover, and high sediment availability promote aggradation. Despite long-held belief that changes in sea level produced major changes in river behaviour, Litchfield and Berryman (2005) revealed that sea level changes had a restrictive influence on these fluvial systems. Nonetheless, changes in local base level (understanding that each point of a river is the base level of the previous point), processes of capture or migration of knickpoints can trigger the shift from aggradational to degradational processes. Tectonics produced an uplift provoked incision, as the gradient of the longitudinal profiles is higher. In New Zealand, there is no proof that tectonic processes have systematically triggered the shift from aggradational to degradational balances along river courses. However, it is clear that uplift movements have preserved terrace flights. Other factors, such as volcanism or land use changes, have played a vital role in some catchments (Clement and Fuller, 2006). These disturbance events are characterised by their punctual and localised character. In contrast, climate or tectonic forcing are independent factors that constantly affect landscapes in the broadest sense (Schumm and Litchty, 1965). Although climate is the primary external force on terrace formation in New Zealand, this does not exclude the critical role of other controls as primary factors in some systems. As the spatial distribution of forces triggering geomorphic changes vary at local, regional or continental area (Brierley and Fryirs, 2005), so the key determinants of terrace formation may be different. Given these insights, some inconsistencies and uncertainties remain. While climate change is uniformly accepted to promote shifts in the aggradational/degradational balance at wide spatial scales, the age structures of river terraces preserved in New Zealand cannot always be matched. This perhaps reflects the capacity of individual systems to respond to differing external forces. In making these comparisons, due regard must be given to the within-catchment position of terraces, the ‘connectivity’ of any given system, the sensitivity of any given landscape to change and the past history of disturbance events. The balance of erosion and deposition in any given reach reflects catchment-specific considerations. Some parts can be experiencing degradational processes, others aggradational and others might be in equilibrium (Schumm, 1991). Particular regard must be given to the prevailing sediment flux, which reflects patterns of sediment storage within any given system. In many instances, hillslope-channel connectivity is a key determinant of sediment input to river systems (Fryirs et al., in press). Landscape sensitivity, measured as the capacity of landforms to adjust (Brunsden, 2001), varies from catchment to catchment. Hence, the same impelling force may engender quite different outcomes – the principle of complex response. A key control on these relationships is the proximity of a system to a threshold condition at the time of any given event. The influence of these factors on sediment transfer in catchments influences the aggradational/degradational balance in any reach, and hence the formation of terraces. In some instances, this notion of spatial contingency is compounded by temporal contingency, as contemporary features of the landscape may have been shaped primarily by past events. For example, Church and Slaymaker (1989) show that river systems in British Columbia are still reworking sediments delivered to the valleys by glaciers during LGM. The time span of system adjustment to disturbance events may span over tens of thousands of years. This is very important in the case of New Zealand rivers. One of the main issues concerning terrace age and controls of formation are the dating methods and proxy data currently used and available. A consistent time framework is basic for the reconstruction of ancient environments and correlation of different features from diverse sites. Development in dating methods and their widespread application is required to gain further accuracy in the correlation of different terrace sets for various catchments. The search for correspondence between different proxy data is an extremely helpful tool in reconstructing these environments, linking data from alluvium, loess, tephra, pollen, sea cores, ice cores and so on. Great care must be applied in these extrapolations, as most of the ages presented in this report were derived from sediments above alluvium or strath which are referred to as minimum ages for the time for the formation of the surface they cover. So, some of the ages are pure estimations or are derived from logical thinking: if aggradation was occurring during LGM, then every aggradation event is linked with a cold stage. Ultimately, the evidence must speak for itself, rather than being perpetuated by traditional notions within circular, self-reinforcing arguments.
7. Conclusions
8. Acknowledgements This article has been written as a result of the stay made by Angel Soria at the University of Auckland, specifically at the School of Geography, Geology and Environmental Science under the supervision of Dr. Gary Brierley in Auckland, New Zealand. The mentioned stay was sponsored by the Department of Education, Universities and Research of the Basque Government within the plan called “Ayudas para estancias cortas en centros distintos al de aplicación de las becas del programa de formación de investigadores 2005-2006”. The authors would like to thank Alastair Clement (Massey University), Michaela Cowie (University of Auckland) and Hiroki Ogawa (University of Auckland) for their invaluable help.
9. References Bridgland, D.R. 2000. River terrace systems in north-west Europe: an archive of environmental change, uplift and early human occupation. Quaternary Science Reviews, 19: 1293-1303. Brierley, G., Fryirs, K. and Jain, V. 2006. Landscape connectivity: the geographic basis of geomorphic applications. Area, 38: 165-174. Brierley, G.J. and Fryirs, K.A. 2005. Geomorphology and river management. Blackwell Publishing, 398 pp. Brunsden, D. 2001. A critical assessment of the sensitivity concept in geomorphology. CATENA, 42: 99-123. Bull, W.L. and Knuepfer, P.L.K. 1987. Adjustments by the Charwell River, New Zealand, to uplift and climatic changes. Geomorphology, 1: 15-32. Chorley, R.J., Schumm, S.A. and Sugden, D.E. 1984. Geomorphology. Methuen and Co. Ltd., New York. Church, M. and Slaymaker, O. 1989. Disequilibrium of Holocene sediment yield in glaciated British Columbia. Nature, 337: 452-454. Clement, A. and Fuller, I. 2006. New Zealand river dynamics over time: a review and model for catchment response to environmental change during the past ~30 ka. New Zealand Journal of Geology and Geophysics. In review. Davis, W.M. 1895. The development of certain English rivers. Geographical Journal, 5: 127-146. Eden, D.N. 1989. River terraces and their loessial cover beds, Awatere River valley, South Island, New Zealand. New Zealand Journal of Geology and Geophysics, 32: 487-497. Formento-Trigilio, M.L., Burbank, D.W., Nicol, A., Shulmeister, J. and Rieser, U. 2003. River response to an active fold-and-thrust belt in a convergent margin setting, North Island, New Zealand. Geomorphology, 49: 125-152. Fryirs, K.A., Brierley, G.J., Preston, N.J. and Kasai, M. Buffers, barriers and blankets: The (dis)connectivity of catchment-scale sediment cascades. CATENA, In Press, Corrected Proof. Goff, J.R., Nichol, S.L. and Rouse, H.L. 2003. The New Zealand Coast. Dunmore Press, 312 pp. Kasai, M. 2006. Channel processes following land use changes in a degrading steep headwater stream in North Island, New Zealand. Geomorphology, 81: 421-439. Kasai, M., Brierley, G.J., Page, M.J., Marutani, T. and Trustrum, N.A. 2005. Impacts of land use change on patterns of sediment flux in Weraamaia catchment, New Zealand. CATENA, 64: 27-60. Leopold, L.B., Wolman, M.G. and Miller, J.P. 1964. Fluvial processes in Geomorphology. W.H. Freeman, San Francisco, 522 pp. Litchfield, N.J. 2003. Maps, stratigraphic logs and age control data for river terraces in the eastern North Island. Science Report 2003/31, Institute of Geological and Nuclear Science, Lower Hutt. Litchfield, N.J. and Berryman, K.R. 2005. Correlation of fluvial terraces within the Hikurangi Margin, New Zealand: implications for climate and baselevel controls. Geomorphology, 68: 291-313. Maddy, D. 1997. Uplift-driven incision and river terrace formation in southern England. Journal of Quaternary Science, 12: 539-545. Maddy, D., Macklin, M.G. and Woodward, J.C. 2001. River basin sediment systems : archives of environmental change. Balkema, Lisse, 503 pp. Manville, V. and Wilson, C.J.N. 2004. The 26.5 ka Oruanui eruption, New Zealand: a review of the roles of volcanism and climate in the post-eruptive sedimentary response. New Zealand Journal of Geology and Geophysics, 47: 525-547. McGlone, M.S. 2001. A Late Quaternary pollen record from marine core P69, southeastern North Island, New Zealand. New Zealand Journal of Geology and Geophysics, 44: 69-77. McGlone, M.S. 2002. A Holocene and latest Pleistocene pollen record from Lake Poukawa, Hawke's Bay, New Zealand. Global and Planetary Change, 33: 283-299. McGlone, M.S., Nelson, C.S. and Hume, T.M. 1978. Palynology, age and environmental significance of some peat beds in the Upper Pleistocene Hinuera Formation, South Auckland, New Zealand. Journal of the Royal Society of New Zealand, 20: 205-220. McLea, W.L. 1990. Palynology of Pohehe Swamp, northwest Wairarapa, New Zealand: a study of climatic and vegetation changes during the last 41,000 years. Journal of the Royal Society of New Zealand, 20: 205-220. Merritts, D.J., Vincent, K.R. and Wohl, E.E. 1994. Long river profiles, tectonism, and eustasy: A guide to interpreting fluvial terraces. Journal of Geophysical Research, 99: 14,031-14,050. Milne, J.D.G. 1973a. Upper Quaternary geology of the Rangitikei drainage basin, North Island, New Zealand. Unpublished PhD thesis, Victory University of Wellington, Wellington. Milne, J.D.G. 1973c. Map and sections of river terraces in the Rangitikei Basin, North Island, New Zealand. New Zealand Soil Survey Report 4, Department of Scientific and Industrial Research, Wellington, New Zealand. Palmer, A.S., Barnett, R., Pillans, B.J. and Wilde, R.H. 1988. Loess, river aggradation terraces and marine benches at Otaki, southern North Island, New Zealand. In: Loess, its distribution, Geology and Soils (Eds D.N. Eden and R.J. Furkert), pp. 163-174. Balkema, Rotterdam. Palmer, A.S. and Vucetich, C.G. 1989. Last Glacial loess and early Last Glacial vegetation history of Wairarapa valley, New Zealand. New Zealand Journal of Geology and Geophysics, 32: 499-513. Pedraza, J. 1996. Geomorfología. Principios, Métodos y Aplicaciones. Ed. Rueda, Madrid, 414 pp. Pillans, B. 1994. Direct marine-terrestrial correlations, Wanganui Basin, New Zealand: The last 1 million years. Quaternary Science Reviews, 13: 189-200. Powers, W.E. 1962. Terraces of the Hurunui River, New Zealand. New Zealand Journal of Geology and Geophysics, 5: 114-129. Schofield, J.C. 1965. The Hinuera Formation and associated Quaternary events. New Zealand Journal of Geology and Geophysics, 8: 772-791. Schumm, S.A. 1977. The fluvial system. Wiley, New York, 338 pp. Schumm, S.A. 1991. To interpret the Earth: Ten ways to be wrong. Cambridge University Press, Cambridge, 133 pp. Schumm, S.A. and Litchty, R.W. 1965. Time, Space and Causality in Geomorphology. American Journal of Science, 263: 110-119. Stevens, K.F. and Palmer, A.S. 1986. Geological Society of New Zealand 1986 Annual Conference field trip guide. In: Geological Society of New Zealand Annual Conference. Geological Society of New Zealand, Palmerston North. Te Punga, M.T. 1952. The geology of the Rangitikei valley. New Zealand Geological Survey Memoir 8, New Zealand Geological Survey, Wellington. Vandenberghe, J. 2002. The relation between climate and river processes, landforms and deposits during the Quaternary. Quaternary International, 91: 17-23. Vandenberghe, J. and Maddy, D. 2001. The response of river systems to climate change. Quaternary International, 79: 1-3. Vella, P. 1963. Upper Pleistocene succesion in the inland part of Wairarapa valley, New Zealand. Transactions of the Royal Society of New Zealand (Geology), 2: 63-68. Vucetich, C.G., Vella, P. and Warnes, P.N. 1996. Antepenultimate glacial to last glacial deposits in southern Wairarapa, New Zealand. Journal of the Royal Society of New Zealand, 26: 469-482. Warnes, P.N. 1992. Last interglacial and last glacial stage terraces on the eastern side of Wairarapa Valley between Waiohine and Waingawa Rivers. Journal of the Royal Society of New Zealand, 22: 217-228. Womack, W.R. and Schumm, S.A. 1977. Terraces of Douglas Creek, northwestern Colorado: an example of episodic erosion. Geology, 5: 72-76. |
