The Pliocene initiation and Early Pleistocene volcanic disruption of the palaeo-Gediz fluvial...

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Quaternary Science Reviews 26 (2007) 2864–2882

The Pliocene initiation and Early Pleistocene volcanic disruption of thepalaeo-Gediz fluvial system, Western Turkey

Darrel Maddya,�, Tuncer Demirb, David R. Bridglandc, Antonie Veldkampd,Chris Stemerdinka, Tim van der Schrieka, Danielle Schrevee

aDepartment of Geography, University of Newcastle, Daysh Building, Newcastle upon Tyne NE1 7RU, UKbDepartment of Geography, Harran University, 63300 Sanliurfa, Turkey

cDepartment of Geography, Durham University, South Road, Durham DH1 3LE, UKdWageningen University and Research Centre, Duivendaal 10, 6701 AR Wageningen, PO Box 37, 6700 AA Wageningen, The Netherlands

eDepartment of Geography, Royal Holloway University of London, Egham, Surrey TW20 0EX, UK

Received 22 April 2005; accepted 22 January 2006

Abstract

In this paper, we report our latest observations concerning a Pliocene and Early Pleistocene record from Western Turkey. The

sedimentary sequence described comprises the fluvial deposits of an Early Pleistocene palaeo-Gediz river system and its tributaries prior

to the onset of volcanism around Kula and the subsequent lacustrine, volcaniclastic and fluvial deposits associated with the first phase of

volcanism (�1.2Ma) in this area.

Early development of an east–west drainage system in this area resulted from tectonic adjustments to north–south extension and the

formation of east–west-oriented grabens. Headward erosion of drainage entering the main Alas-ehir graben led to the progressive capture

of pre-existing drainage systems as eastward (headward) erosion upstream tapped drainage networks previously formed in internally

draining NNE–SSW-oriented basins. Within one of these, the Selendi Basin, part of this evolutionary sequence is preserved as a buried

river terrace sequence. Eleven terraces are preserved beneath alluvial fan sediments that are, in turn, capped by basaltic lava flows. Using

the available geochronology these terraces are considered to represent sedimentation–incision cycles which span the period

�1.67–1.2Ma. Although progressive valley incision is a fluvial system response to regional uplift, the frequency of terrace formation

within this time period suggests that the terrace formation resulted from sediment/water supply changes, a consequence of obliquity-

driven climate changes. The production of sub-parallel terraces suggests that during this period the river was able to attain a quasi-

equilibrium longitudinal profile adjusted to the regional uplift rate. Thus, the incision rate of 0.16mma�1 during this period is believed to

closely mirror the regional uplift rate.

After the onset of volcanism at �1.2Ma, there is a destruction of the dynamic link between fluvial system behaviour and climate

change. The repeated damming of the trunk river and its tributaries led to the construction of complex stratigraphic relationships.

During the first phase of volcanism the palaeo-Gediz river was dammed on numerous occasions leading to the formation of a series of

lakes upstream of the dams in the palaeo-Gediz valley. Variations in lake level forced localised base-level changes that resulted in

complex fluvial system response and considerable periods of disequilibrium in profile adjustment. Furthermore, response to these base-

level changes most likely disrupted the timing of the incisional adjustment to the on-going regional uplift, thus making the use of this part

of the archive for inferring regional uplift rates untenable.

r 2007 Elsevier Ltd. All rights reserved.

1. Introduction

IGCP449 ‘Global correlation of Late Cenozoic deposits’was conceived as a project not only to bring together

existing information from across the globe concerningfluvial sedimentary sequences, but also to identify andtarget areas where information was lacking. Thus a statedaim of the project was to initiate research that wouldinvestigate these data vacuum areas (Bridgland andMaddy, 2002). One such area, identified early in theproject as an area of substantial potential, was the eastern

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0277-3791/$ - see front matter r 2007 Elsevier Ltd. All rights reserved.

doi:10.1016/j.quascirev.2006.01.037

�Corresponding author. Fax: +44 191 222 5421.

E-mail address: [email protected] (D. Maddy).


sector of the Mediterranean. With river systems unaffectedby the consequences of ice-sheet incursions and extensivepreservation promoted, in many cases, by moderately highuplift rates, these areas seemed ideal targets for furtherinvestigation particularly as the Mediterranean had alreadyyielded exciting results for the later Pleistocene (Kuzucuo-glu, 1995; Macklin et al., 1995, 2002; Woodward et al.,1995; Maas et al., 1998; Rose and Meng, 1999). Further-more, given the nature of the present vegetation in theseareas and the consequent extensive natural exposure oftheir sedimentary record, it is no surprise that during thelife of this project several studies have emerged from thisarea including work in Syria (Bridgland et al., 2003) andTurkey (Westaway et al., 2003; Demir et al., 2004;Westaway et al., 2004; Maddy et al., 2005, in press).Although these are preliminary studies they have yieldedexciting results indicating the wealth of informationwaiting to be recovered from these fluvial archives. Whilethe task of recovering valuable data from these archiveswill take many years, it is already clear that they contain arecord that will equal, if not surpass, that of the majornorth–west European river systems (Bridgland, 2000).

The Plio–Pleistocene evolution of river basins in theWestern Mediterranean has been the focus of specialattention, especially within Spain (e.g. Harvey andWells, 1987; Visera and Fernandez, 1992; Mather, 1993;Harvey et al., 1995; Mather and Harvey, 1995; Matheret al., 1995; Stokes and Mather, 2000; Garcıa-Melendezet al., 2003). Such areas are attractive because they record theinitial phases of drainage development as uplift of in-filled

basins cause embryonic fluvial systems to develop. ThePlio–Pleistocene evolution of these embryonic systems canthen be charted with reference to the sedimentary records.These studies illustrate the interaction of tectonic andclimate change affects on fluvial system behaviour. Thisinteraction produces a sedimentary record which iscomplex, a situation made even more difficult to unraveldue to the overprint of river capture and drainage areaexpansion/contraction processes (e.g. Wenzens and Wen-zens, 1995; Calvache and Viseras, 1997; Wenzens andWenzens, 1997; Stokes et al., 2002). Nonetheless therecording of the inception of a fluvial system is rareand thus these relatively complete studies of drainageevolution are particularly helpful when attempting toconstrain and test theoretical models of landscape devel-opment (Pazzaglia, 2004).In this paper, we report our latest observations

concerning a Plio–Pleistocene record from Western Tur-key. This sequence shows many attributes of thoserecorded from the Western Mediterranean but the precisetectonic setting and its different climate change regimemake an exact comparison unlikely. Furthermore, thestudy reported here records a further and importantcomplication, the disturbance of fluvial system develop-ment by repeated damming of the rivers by the incursion ofbasaltic lava flows into the valley bottom. Although thissituation is more complicated the presence of readilydateable materials, i.e. basalts, does provide encourage-ment for further investigation due to the potential outcomeof quantifying process rates.

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Fig. 1. General tectonic framework of Western Turkey (based upon Aksu et al., 1987). Outline box indicates approximate position of study area (as in

Fig. 3). Open/filled circles designate Late Cenozoic grabens on land. Dotted lines represent major faults. Inset shows position of Fig. 1 in Turkey.

D. Maddy et al. / Quaternary Science Reviews 26 (2007) 2864–2882 2865


Our field area lies north of the city of Kula, some�30 km upstream of the Alas-ehir graben in the Kulavolcanic province (Figs. 1–3). The sedimentary sequencedescribed in this paper comprises the fluvial record of anEarly Pleistocene palaeo-Gediz river system and itstributaries prior to, and immediately succeeding, the onsetof volcanism in the Kula area. After a general introductionto the modern Gediz Basin and its relation to the tectonicsof Western Turkey, we will turn our attention to adescription of the pre-Quaternary sequence and a discus-sion of the initiation of the Quaternary drainage system asa primary response to tectonic events and river capture. Asummary of our recent findings concerning the buriedEarly Pleistocene (pre 1.2Ma) terrace sequence previouslydescribed in detail by Maddy et al. (2005, in press) follows,this describes a period of drainage development driven bythe interaction of climatic and tectonic process. Finally wewill report new observations and interpretations of thedrainage changes associated with the first phase of volcanicactivity in this region and their implications for fluvialsystem behaviour.

1.1. The Gediz River drainage and the Geology of Western

Turkey

The Gediz River is one of the principal rivers of westernTurkey and it drains a catchment area of �17,000 km2

(IWMI and GDRS, 2000). The modern Gediz river rises inmountains which exceed elevations of 2000m north of thetown of Gediz (Fig. 2). It drains westward to the AegeanSea where it forms a delta north of Izmir. Along its 401 kmlength the Gediz crosses some of the principal tectonicstructures of Western Turkey. For most of its downstreamreaches the Gediz flows along the axis of one of the majorgrabens of western Turkey, the Alas-ehir graben (Eyidoganand Jackson, 1985, Fig. 1). This graben is a consequence ofLate Cenozoic crustal extension in the region and reflectsthe wider pattern of extension expressed by a series ofeast–west striking normal faults, which define low-lyinggrabens separated by footwall mountain ranges (Figs. 1and 2) (Aksu et al., 1987; Paton, 1992; Koc-yigit et al.,1999). Bozkurt and Sozbilir (2004) suggest the Alas-ehirgraben has formed within the last �5Ma although

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Fig. 2. Simplified regional geology around the study area based upon the 1:500,000 scale Geological Map of Turkey (1973) and Seyitoglu (1997). Only

selected faults are shown, with supplemental information based upon Purvis and Robertson (2004).

D. Maddy et al. / Quaternary Science Reviews 26 (2007) 2864–28822866

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Fig. 3. Generalised geology map of the study area (based upon the mapping of Ercan et al., 1983, modified by additional observations by the authors). Shaded area represents basaltic plateaux. The map

grid projection is UTM.

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Westaway et al. (2004) suggest a slightly earlier start tograben formation at �7Ma. Whatever the age of the startof graben formation major displacement of Late Pliocene/Early Pleistocene deposits along the main southern faultssuggests that significant footwall uplift occurred during thepast �1.6Ma (Sarıca, 2000; Bozkurt and Sozbilir, 2004),i.e. during the Quaternary.

Our area of study lies north of the graben around Kula(Figs. 1–3), where the Gediz flows westwards across theuplifting footwall block prior to entering the Alas-ehirgraben. The uplift of this footwall block is, in part, drivenby movement on the graben bounding fault system,although the known displacement of faults along the grabenmargin cannot account for the total amount of known upliftand thus it has been suggested that there is a substantialelement of regional uplift in this area (Westaway, 1993).Whatever the mechanism of uplift in our study area, what isclear is that the fluvial response has been a punctuated, butprogressive, incision during the Plio–Pleistocene.

1.2. Pre-Quaternary geology of the study area

The study area lies within the southern sector of the SelendiBasin (Figs. 2 and 3). The Selendi Basin is an in-filled Tertiarystructure formed within the underlying basement rocks(predominantly metasediments and ophiolites) and constitu-tes one of four NNE–SSW aligned basins (Fig. 2) which arecut to the south by the younger E–W aligned Alas-ehir grabenand thus predate that structure. These basins are of disputedorigin with some authors favouring formation as normalfault-bounded grabens during an early phase of east–westextension (e.g. Seyitoglu and Scott, 1994), while it has alsobeen suggested that they originate through post-orogenicsubsidence, i.e. without active faulting (Inci, 2002). Purvis andRobertson (2004) present a further model in which theysuggest these basins relate to an early phase of north–southextension (similar to that which later formed the Alas-ehir andSımav grabens (Fig. 2)) with the basement highs representingundulations of an inferred extensional detachment surface.Whatever their origins the basins are largely in-filled byupwards-fining sequences comprising basal fluvial sedimentsfining to lacustrine deposits towards the top (see below).During this in-filling phase the basin sequences weredisrupted by the eruption of large volcanoes which led tothe widespread deposition of thick volcaniclastic sequences(Fig. 2). In the Selendi Basin, age estimates ranging from�18.9 to �14.9Ma (Seyitoglu, 1997) place these eruptions inthe Early–Middle Miocene. Significantly, these in-fill se-quences are deformed during the latest phase of north–southextension with the formation of numerous high-angle normalfault-bounded east–west-oriented structures (Fig. 2.).

Within the study area (Figs. 2 and 3) the Selendi Basininfill (up to �400m in thickness) comprises basal coarse-clastic sediments of the Hacıbekir Group overlain by theInay Group (Seyitoglu, 1997). The Inay Group can besubdivided into a thick sequence of grey/white, fluvial/colluvial clastic sediments (Ahmetler Formation, Ercan

et al., 1983) overlain by thinner continental carbonates oflacustrine origin (Ulubey Formation, Ercan et al., 1983), alithostratigraphic sequence which represents the progressivein-fill of an internally draining basin (Ercan et al., 1983,Purvis and Robertson, 2004). The stratigraphic relationshipof the volcanic eruptions to the Hacıbekir and Inay Groupsis disputed (Purvis and Robertson, 2004) and thus theprecise chronology of this sequence remains insecure.

2. Plio–Pleistocene drainage development: tectonics and

river capture

The initiation of the modern east–west drainage line is aproduct of Plio–Pleistocene tectonic events and repeatedriver capture. The latest pulse of north–south extensioncreated not only the Alas-ehir and Sımav grabens but alsoled to the formation of numerous east–west aligned mini-grabens (up to 10 km wide), e.g. within the Selendi andUs-ak-Gure Basins (Purvis and Robertson, 2004, Fig. 2).Associated footwall uplift along the main grabens, togetherwith a large component of regional uplift, led to increasingrelief relative to the local graben base level. Theseboundary conditions fashioned the nature of early fluvialsystem development. The onset of footwall uplift acrossthese basins led to the end of the widespread lacustrinesedimentation (Ulubey Formation) and the initiation ofincision. The Asartepe Formation, comprising sands andgravels (Ercan et al, 1978, 1983), has been considered torepresent this phase, however, these deposits are poorlydefined and appear to be of different ages in each basin, i.e.all sediments which relate to the Plio–Pleistocene have beengrouped under this heading and no attempt has been madeto investigate these deposits further. Despite the lack ofsedimentary detail for this period some conclusions can bedrawn concerning the development of the palaeo-Gedizdrainage system.Vigourous headward erosion by a river system at the

northern boundary of the Alas-ehir graben initially led tothe capture of drainage within the Demırcı basin, i.e. theDemırcı river system (Figs. 2 and 4A location C). Laterheadward erosion of an eastern tributary to this system cutthrough the area overlying the basement high whichbounds the Demırcı basin to the east and captured thedrainage of the Selendi Basin (Fig. 4B location D). It isprobable that this erosion was aided by E–W faulting anddisplacement within the Ulubey Formation. This processultimately led to the formation of the modern Selendi riversystem and thus drainage from this area into the Alas-ehirgraben. It is not yet known how drainage in either theDemırcı or Selendi Basin was arranged prior to thesecaptures. It is possible that the uplift and capture tookplace rapidly after the onset of Plio–Pleistocene grabenformation, thus it is likely that both the Demırcı andSelendi Basins could still have been internally drainingbasins (i.e. similar to the situation during the deposition ofthe Ulubey Formation) prior to capture of their respectivedrainage systems.

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Fig. 4. Palaeogeographic reconstruction of the development of palaeo-Gediz drainage: (A) drainage confined to the Demırcı basin; (B) drainage extends to

capture the drainage within the Selendi basin; and (C) drainage extends to capture drainage from the western sector of the Us-ak-Gure basin and

completing the development of the modern Gediz catchment.



Following capture at the south-west of the Selendi Basincatchment (Fig. 4B), ultimately all drainage within theSelendi Basin would have been drawn towards this point,with the effect of capture sending a wave of erosionthroughout the Selendi Basin, the result of a dramatic fallin local base level. Similar responses to capture have beennoted in the Sorbas basin SE Spain (Stokes et al., 2002).This process would have been moderated only by theresistance of the basement high (separating the Selendifrom the Demırcı Basins) which would have formed a localbase level for erosion at its eastern (upstream) boundaryonce any overlying Hacıbekir/Inay Group sediments hadbeen removed. The creation of the modern Gediz networkwould have been completed by headward erosion of one ofthe Selendi river tributaries, eastwards into the westernsector of the Us-ak-Gure Basin (Fig. 2, location A). Onlyafter this latest capture would the system tap the Gedizarea (Figs. 2 and 4C location E). It is within the area of thistributary of the Selendi river that the Early Pleistoceneterrace sequence (described below) is preserved. Theprogressive eastward headward erosion of this systemcontinues at the present time. The modern Gediz drainagesystem is close to capturing the north–south drainage (i.e.Damlilar Derisi) of the eastern sector of the Us-ak-GureBasin around Us-ak (Fig. 4C location F.).

3. Early Pleistocene river terraces: an uplift-driven, climate-

controlled fluvial system

Within the main study area post-depositional uplift of theInay Group has resulted in the progressive dissection of thisTertiary basin fill. Differential erosion has led to theformation of high-level plateaux to the north of the fieldarea (Fig. 3), formed in the resistant carbonates of the UlubeyFormation and, where the carbonates have been completelyremoved, to the creation of lower level extensive badlandsformed within the underlying Ahmetler Formation (Figs. 3and 5A). Where the sediments of the Inay Group have beenremoved by erosion, a pre-Inay landscape is being exhumed(Fig. 3.). The exhumed basement forms ridges whichconstitute the eastern and western watersheds of the south-bank tributary drainage systems of the Sogut and the formerKula river (Fig. 3). The Kula river has been artificiallydiverted into the Sogut during the Holocene and thus thisarea is currently drained by a poorly developed gully system.

Earlier work on drainage evolution in the area aroundKula (Ozaner, 1992) identified important patterns ofdrainage changes during the Quaternary but did notpursue a detailed investigation of the sedimentary record.From beneath the high-level, lava-capped, Sarnıc- andBurgaz plateaux (Figs. 3 and 5B) Maddy et al. (2005, inpress) report the discovery of a well-preserved flight ofburied river terraces (Figs. 6A and B). These terraces arethe result of deposition within a tributary river draining tothe Selendi river (see above), referred to here as the palaeo-Gediz. Extensive outcrops of palaeo-Gediz gravels lieon bounding surfaces with the underlying Ahmetler

Formation which have been shown to form a series ofsteps that fall in altitude from north–south. These steps areinterpreted as representing former valley floors and thus

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A

KavtepeUlubey Fm. Uplands

Burgaz Ba tepe

B

Kale Tepe

Burgaz Plateau

ÇileTepe

Sarn Ba tepe

C

palaeo-Gediz gravels

limestone-rich fan gravels

Fig. 5. (A) General view looking east with the limestone plateau (Ulubey

Formation) to the north and Burgaz plateau to the south; (B) general view

from the current Gediz floodplain looking north-west to the Burgaz and

Sarnıc- plateaux; and (C) exposure at location 40 (Fig. 3A) showing palaeo-

Gediz gravels of terrace VIII beneath limestone-rich alluvial fan gravels.



form a flight of buried river terraces. In all, 11 terraces(I–XI, Figs. 6A and B after Maddy et al., 2005) have so farbeen identified. The palaeo-Gediz gravels are, in mostcases, immediately overlain by limestone-rich gravels,which are believed to represent the deposits of tributaryfluvial ‘fans’ (see below) fed by rivers with catchments inthe limestone plateau to the north (Figs. 2 and 5C). It isprobable that the drainage systems that deposited thesefluvial fans were precursors of the current Hudut andGeren river systems (Fig. 3). Maddy et al. (2005) suggestthat the fluvial incision necessary for the development ofthis terrace flight is a consequence of dynamic fluvialsystem response to regional uplift. Using the availablegeochronology of the lava flows that cap the sequence(�p1.264Ma, Westaway et al., 2004) and inference

concerning the onset of terrace development in response toaccelerating uplift and the onset of volcanism downstream(�1.67Ma, Richardson-Bunbury, 1996), they suggest thatthis terrace sequence spans the time interval 1.67–1.2Ma.Maddy et al. (2005) derive a simple linear age–height modelbased upon these constraints to suggest a link betweenterrace formation and climate change. Fig. 7 shows a plot ofterrace base heights (using the linear age–height modelderived from the independent age estimates) against theODP967 d18O record from the Eastern Mediterranean Basin(Kroon et al., 1998). From this visual comparison Maddyet al. (2005) suggested that the timing of terrace formationwas most likely to have been controlled by sediment/discharge changes driven by regional climate change andthus the terraces represent sedimentation/incision cycles

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Fig. 6. (A) Detailed map of the interpolated buried terraces of the Gediz (after Maddy et al., 2005). Outcrop exposures, numbered 1–47 are accurately

heighted and recorded. The symbol % represents the position of the height reference datum, all heights quoted are relative to this location on the present

Gediz river. The three principal volcanic necks are labelled, a is Toytepe, b Sarnıc- Bagtepe and c Burgaz Bagtepe. (B) A schematic section showing the

Burgaz Bagtepe flows capping the terrace and alluvial fan sediments on the transect A–A0 shown in (A) across the Burgaz plateau (after Maddy et al.,

2005). Base of the lava flow represents the volcaniclastic sequence contact with the underlying fan sediments. The stepped line represents the base of the

terraces, i.e. the palaeo-Gediz gravel-Ahmetler Formation contact.



oscillating at the �41ka obliquity-driven climate changecycle of the Early Pleistocene.

In a later paper Maddy et al. (in press) describe in moredetail how the preservation of this terrace system ispromoted by the successive burial of terraces by alluvialfan progradation. Fig. 8 shows the reconstructed landsur-face prior to the onset of volcanism in this area based uponthe contouring of the heights of the limestone-rich gravelscontact with the overlying volcaniclastic sequence. Thisreconstruction is interpreted as coalescing fan systemsforming an apron, or bajada, immediately south of thelimestone plateau. A similar situation exists today immedi-ately upstream of the study area where volcanism has playedno direct role in landscape development. The reconstructionshows only two fans but it is acknowledged that thisreconstruction is based upon the preserved sections around

the basalt plateaux and thus the information from the areabetween the plateaux is limited. It is therefore possible, evenprobable given the likely drainage density, that at least oneadditional system may have been present.Maddy et al. (in press) suggest that trunk river incision

(and therefore terrace formation) and fan toe progradationare dynamically linked and tend to occur during periods ofclimatic amelioration, when sediment supplies are reduceddue to bank and slope stabilisation by vegetation (Fig. 9A).In contrast, the palaeo-Gediz sediments, together with thebulk of the fan gravels, are considered most likely to

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Fig. 7. Terrace base heights plotted as black shaded circles (scale on

primary axis) against time using a linear age model based upon dated lava

flows (after Maddy et al., 2005). The Marine ODP967 Oxygen Isotope

record (scale shown on secondary axis) is plotted against time based upon

the published age model (Kroon et al., 1998). Marine Isotope Stages are

numbered for interglacials only.

220m

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Fig. 8. Reconstructed pre-eruption landscape. Contours are reconstructed

using the upper fluvial (palaeo-Gediz or alluvial fan) sediment contact

height with the base of the volcaniclastic sequence (after Maddy et al., in

press). Two fan-feeder systems are reconstructed but additional feeders

may have been present.

B

A

Fig. 9. Cartoon demonstrating the relationship between fan systems and

trunk river (after Maddy et al., in press). (A) During periods of vegetation

cover, lowered sediment supply and lowering magnitude of flooding events

lead to fan-head channel entrenchment and lobate fan progradation

within the fan toe area occupied by the active channel. Decoupling of the

fan-main river system leads to reduced sediment supply to the valley floor,

which together with enhanced bank stabilisation promote incision and

terrace development. (B) During non-vegetated periods, high sediment

supply together with competent discharge leads to fan aggradation and an

active fan surface distributary channel network. Coupling of the channel-

fan system leads to high sediment loads and main channel floodplain

aggradation.



accumulate (aggrade) during the intervening periods whensediment supply conditions are higher, a consequence ofreduced vegetation cover resulting in unstable banks andslopes (Fig. 9B). These conditions were most prevalentduring the colder episodes of the Early Pleistocene. Theprogradation of the tributary fans over the terraces protectsthe north bank terraces from later erosion and promotes thesubsequent excavation of the more easily erodible substrateof the Ahmetler Formation to the south during the nextphase of terrace formation. Thus, whatever the preciselinkage between the trunk river system and its tributaries, itis clear that the progradation of fans over the terraces is acritical process in the initial preservation of this sequence.

Typically the sediments within each terrace are 2–3m inthickness but reach 5m on terrace V. The lack of diagnosticsedimentary structures within these deposits makes theprecise style of fluvial deposition difficult to determine.Fig. 10 represents an attempt to establish the possibleterrace gradients. This figure plots the height of the terracebases against an east–west axis using UTM Eastingcoordinates. The exact route of the palaeo-Gediz channelsystem is unknown and therefore the level of possiblesinuosity is also indeterminate. This projection thereforerepresents only one possible model and the uncertainties,especially given the low number of observations at mostlevels and their clustered geographical distributions, aresubstantial. Perhaps the most appropriate level on which toassess this is terrace IV, where there are a comparativelylarge number of well-spaced observations. A simple linearregression through the points suggests a basal gradient of�0.97mkm�1. This is higher than the 0.49mkm�1

gradient for terrace I suggested by Maddy et al. (2005)but still represents a comparatively low-gradient system, atleast compared to the gradient of the modern river whichvaries through the study reaches, due to a succession ofknickpoints, between 5 and 10mkm�1.

Furthermore no preserved terrace tract exceeds 500m inwidth. Although the progressive southward migration ofthe palaeo-Gediz would have led to limited preservation ofeach former floodplain, it is estimated that none of theformer floodplains are likely to have greatly exceeded 1 kmin width through these reaches. Although the evidence forchannel dimensions is limited, an exposure of cementedchannel gravel upturned by collapse at location 31(Fig. 6A) suggests an individual channel width of o5m.Although this might not represent the main channel, ormore than one channel may have been occupied at any onetime, this evidence may suggest that the palaeochanneldimensions were relatively small compared to those of themodern river. The modern Gediz exceeds 10m in channelwidth throughout the study reach.The inference of a low-gradient, relatively small channel

system, taken together with the comparatively smallfloodplain and thin depositional units (only terrace V

could be interpreted as aggradational), may suggest apalaeo-Gediz system that was smaller than that of thepresent day. This interpretation is counter to the moreextensive deposits of the northerly-derived fan systems thatappear to represent more substantial catchments than theirmodern equivalents. These observations point to adrainage system that was still developing. It is probablethat the palaeo-Gediz subsequently gained catchment areaupstream, while the tributaries considered in our presentfield area were undergoing capture of their watershed areasby headward erosion of northwards draining rivers andthus reducing in overall catchment size. The parallel natureof the buried terraces does, however, suggest at leasttemporary quasi-equilibrium conditions during their for-mation and thus any major drainage adjustment toenlargement of the catchment must postdate this period.

4. Drainage system reorganisation: a response to the onset

of volcanism

The onset of volcanism in the Kula region is thought tohave begun some time after 2Ma (Richardson-Bunbury,1996). Melt production is believed to be closely associatedwith the rifting and formation of the Alas-ehir graben(Ercan et al., 1983; Ercan, 1993). The lavas of the Kulavolcanic province form alkali basalts with �79 necksidentified by Erinc- (1970). Despite the high number ofvolcanic necks in the Kula area the volume of lavaproduced (�2.3 km2) is comparatively small (Richardson-Bunbury, 1996). The oldest age estimate currently availableis 1.6770.22Ma, which was obtained from lava flows20 km west of the current field area (Richardson-Bunbury,1996, Fig. 2 location B). This estimate has recently beendisputed by Westaway et al. (2004) who suggest that thematerial used in this estimation procedure was unsuitablefor dating and therefore these results are unreliable.There have been a number of attempts to obtain age

estimates from the lava flows within the field area (Borsiet al., 1972; Richardson-Bunbury, 1996; Westaway et al.,

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130.00

140.00

150.00

160.00

170.00

180.00

190.00

200.00

210.00

220.00

650000 652000 654000 656000 658000 660000

I

II

IV

III

V

VI

VII

VIII

IX

X

XI

He

igh

t A

bo

ve

Da

tum

(m

)

Easting (UTM m)

Fig. 10. Model for reconstructed terrace gradients using terrace gravel/

Ahmetler contact heights (i.e. terrace base heights) from the locations in

Fig. 6A, plotted against UTM Easting coordinate.



2004). It is unfortunate, however, that each attempt atobtaining age estimates using the K-Ar method hasproduced often significantly different results. In thefollowing discussion we use the most recent, and thereforemost technologically advanced, 1.2670.015Ma absoluteage estimate taken from a lava flow emanating from theToytepe neck (Westaway et al., 2004, sample 00YM23) asour tie-point for the stratigraphy. We then use thestratigraphic relationships between the Toytepe flows andthe others to establish the relative sequence of eruptions.We acknowledge that the basalts observed representdeposition during multiple eruption events from eachvolcanic neck and therefore the simplified sequence usedbelow may have to be modified as new results arise.

4.1. Tavs-an and Toytepe eruptions (cones 58 and 73, Erinc- ,

1970)

The Toytepe eruption (Fig. 11A) occurred through avolcanic neck situated above fan gravels that overlie thepalaeo-Gediz gravels of terrace X at locations 45/46 (Fig.6A). The first eruption products include palagonitic tuffsthat indicate rapid cooling, suggesting possible contactwith water. This observation led Richardson-Bunbury(1996) to conclude that this eruption took place close tothe contemporary river valley floor, i.e. where the watertable was high. However, the lavas from Toytepe can betraced in the field south-westwards where they overlie athick sequence of tephras and lacustrine sediments which inturn overlie the palaeo-Gediz gravels of terrace III atlocation 9 (Fig. 11A).

The same lava overlying location 9 can be traced north-eastwards where it infills a channel cut into the underlyingAhmetler Formation (Fig. 12A). The basalt basal contact isnot seen but at its lowest observed point the basalt is at orbelow the base of exposures at location 4 (143.38m abovedatum), i.e. at a height equivalent to the terrace I valleylevel. There is no evidence to suggest that more than onelava flow is present at this location. Hence, we concludethat the contemporary river valley at the onset ofvolcanism in this area was no lower than the base of theterrace I level.

The palagonitic tuffs are considered here to result fromeruption close to lake level. A pre-existing lake (L1Fig. 11A) is indicated by exposures of laminated sedimentsbeneath the volcaniclastic deposits. Up to 3m of laminatedlacustrine sediments, which overlie palaeo-Gediz gravels ofterrace III at location 9, underlie thick (up to 13m) tephradeposits and the capping basalt (Fig. 12B). Laminated lakesediments in excess of 3m in thickness, again beneath athick tephra sequence, are also evident 100m west oflocation 26 suggesting the lake rises to heights in excess of170m above the datum.

The origin of lake L1 must result from blockage of thepalaeo-Gediz by eruption and the creation of a lava damdownstream of the Sarnıc- plateaux. The height of thelacustrine sediments indicates a downstream dam height in

excess of 30m above the terrace I level valley floor. Thetwo volcanic necks on the Ibrahimaga plateau seem theonly plausible source of basalts for this downstream dam(Fig. 3). The Ibrahimaga Bagtepe neck supplies lava flowswhich diverge around the Tavs-an neck confirming that theTavs-an neck is older. The Tavs-an neck lies directly withinthe path of the palaeo-Gediz valley reconstructed using theterrace record. Despite extensive exploration no evidencefor palaeo-Gediz terraces have been found beneath theIbrahimaga plateau and therefore it is most likely that theTavs-an neck erupted basalts which flowed into the palaeo-Gediz valley to the north. Fig. 13 shows a reconstruction ofa schematic cross-section showing the probable relation-ships between the Tavs-an lava flow and the palaeo-Gedizvalley. Fig. 13A shows the situation prior to eruption. Thesouthern valley margin constructed here from the Ibrahi-maga plateau shows a high-level surface cut into theUlubey Formation limestones. This surface at ca 600m issimilar to erosional benches still present on the north-facing limestone escarpment on the southern side of theSelendi river and most probably therefore is a product ofdifferential erosion of strata within the Ulubey Formation.Remnants of this limestone surface crop out above theIbrahimaga plateau lava flows in a number of locationsand large limestone blocks can be observed close to thebase of lava emanating from the Tavs-an neck. Fig. 13Bshows how eruption of the Tavs-an neck would facilitatedamming of the palaeo-Gediz system. Subsequent breach-ing of the lava dam is likely to have occurred at the lowestpoint adjacent to the readily erodible fan/terrace materialon the northern side of the palaeo-valley. This breach islikely to have eroded all remaining remnants of the palaeo-Gediz terrace system north of the Ibrahimaga plateau.Indeed later incision by the palaeo-Gediz in this area hascompletely eroded the Tertiary basin fill, leading toexhumation of the basement surface (Fig. 3).As lake L1 did not drain prior to the onset of eruption of

the Toytepe neck, it is probable that the Tavs-an eruption isnot much older than 1.2Ma. It is not clear how and whenlake L1 drained but there is no evidence at present todemonstrate that the Toytepe basalts were laid down in thelake. It is probable, however, that the Toytepe lava createda new lake upstream of the lava dam created by its flowinto the terrace I valley floor. What is clear is that theToytepe eruption would have necessitated a reorganisationof drainage within the former tributary fan. It is likely thatthis drainage would have taken the easiest route and flowedaround the lavas. The suggested easterly flow aroundToytepe in Fig. 11A perhaps forms part of the precursordrainage to that of the modern day Bozler river whichflows between the Sarnıc- and Burgaz plateaux (Fig. 3).

4.2. Sarnıc- bagTepe eruption (cone 74, Erinc- , 1970)

There are no reliable age estimates for the Sarnıc-Bagtepe lavas. The exact areal extent of the Sarnıc- Bagtepelavas are difficult to determine but they seem to be



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Fig. 11. Palaeogeographic reconstruction of the study area during the first phase of volcanism: (A) Toytepe Eruption phase. Lake L1 sediments pre-date

the Toytepe lava flows at location 9; (B) Sarnıc- Bagtepe Eruption phase; and (C) Burgaz Bagtepe Eruption phase (early).



restricted to a relatively narrow band around the neck(Fig. 11B). Although preservation state is an unreliableindicator of age it can be noted that the Toytepe neck ismore degraded than the Sarnıc- Bagtepe neck which in turnis considerably more degraded than that of the BurgazBagtepe neck, perhaps suggesting progressively shorterexposure times to the forces of erosion. We thus suggestthat the Sarnıc- Bagtepe eruptions are younger than thoseemanating from Toytepe.

The position of the Sarnıc- Bagtepe neck places theeruption close to the palaeo-Gediz valley axis, the result ofwhich must have been to dam the palaeo-Gediz drainageand thus form an upstream lake (Fig. 11B). The existenceof a lake (L2) is supported by the extensive outcrop ofcarbonate-rich lacustrine deposits at location 17 (Figs. 12Cand D) above fan gravels and the palaeo-Gediz gravels ofterrace V. Additional thin laminated sediments can beobserved above either fan gravels or palaeo-Gediz gravelsat locations 1, 2, 24 and 25. Redeposited (slumped) fan

material observed at location 12 may also indicate massmovement due to saturation of the fan toe as the lakeheight rose. Confirmation that the fan sediment supplycontinued, from the north of Burgaz, with deposition intothe lake is indicated by the carbonate-rich nature of thelaminated fines at location 17.The height of these lacustrine deposits, in excess of 170m

above datum level, suggests that the lake required aminimum lava dam height in excess of 25m above the pre-eruption valley floor. This is similar in altitude to lake L1

and given the likelihood that the Toytepe eruption mayalso have created a dam, it is possible that the actualsequence involves the repeated damming of the river toapproximately the same level (the consequences for thepalaeo-Gediz will be discussed below). It is likely that anyoverspill, once the lake had filled to the height of the lavadam, would have routed towards the topographic low, i.e.to the south of the lava flows (Fig. 11B), excavating themore readily erodible Ahmetler Formation. It is likely that

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A

Location 9

Toypete lava flow infilling terraceI valley

Location 4 (at car level)

C D

B

Lacustine beds

Volcaniclastic deposits

Fig. 12. (A) General view across the south-western edge of the Sarnıc- plateau showing lava from the Toytepe eruption filling the terrace I level valley west

of location 4 and east of location 9; (B) lacustrine sediments beneath a thick tephra sequence at location 9; (C) lacustrine sequence at location 17 showing

soft-sediment deformation due to the over-riding by lavas from an early Burgaz Bagtepe eruption; and (D) lacustrine sediments overlying fan gravels south

of location 17.



the erosion of the Ahmetler Formation could have beenachieved relatively quickly. An estimate of the erodibilityof the Ahmetler Formation can be made with reference tothe erosion phase that created the higher terraces. It islikely that the incision part of the terrace formation cyclelasted no more than a few thousand years during thisperiod and thus if we assume an incision event lasting 2 kaand a minimum incision of 5m (i.e. between terrace III andII, Maddy et al., 2005) then this suggests a minimumincision rate of �2.5mka�1. At this rate a dam height of25m could have been reduced, by diversion around theblock, within 10 ka, although repeated lava flow into thevalley may have re-established the dam level on more thanone occasion.

The more gradual adjustment to the lava dam proposedhere is in contrast to the catastrophic failure of lava damsreported elsewhere (Hamblin, 1990; Lucchitta et al., 2000).We have, as yet, been unable to identify basalt-cobbledeposits that, according to Lucchitta et al. (2000, p32),would ‘‘signal the breaching of lava dams followingeruptions’’.

4.3. Burgaz Bagtepe eruption (cone 75, Erinc- , 1970)

The lava flows which emanate from the Burgaz Bagtepeneck cover a greater area than those from the Sarnıc-Bagtepe neck (Fig. 11C). Extensive exposure displays acomplex stratigraphy indicating the presence of multipleeruption events. The eruption of the Burgaz Bagtepe neckoccurred during the life of lake(s) phase L2 (Fig. 11C).

Soft-sediment disturbance of the lacustrine beds at location17 by the overlying lava flow suggests that lake L2 had notdrained prior to the eruption of the Burgaz Bagtepe neck(Fig. 12C). Where similar lava dams have been reportedelsewhere (e.g. Hamblin, 1990) they have been shown to berelatively short-lived, i.e. of the order of a few thousandyears. The relatively short-term constraint comes fromeither the time needed to erode the dam or its surroundingmaterial, or indeed from the complete in-fill of the lake bysediment arriving from upstream. The relatively lowsediment supply from the palaeo-Gediz indicated by thepre-eruption events suggests that dam-breach is more likelyto have occured as a result of erosion around the block. Atpresent there is no evidence to suggest fluvial incisionbetween the lakes of phase L2. This, perhaps, indicates thatthe time between high lake level stands during the L2 lakephase was insufficient to allow fluvial system adjustment tothe on-going regional uplift (see below).A further consequence of these eruptions, as already

noted above, is the disturbance of the northerly-derivedtributary drainage system. It is probable that the flowemanating from the upstream limestone catchment wouldhave been dammed and then subsequently diverted aroundthe edges of the Burgaz Bagtepe lava flows. Once eruptionsceased, diversion of the upstream drainage around the lavaflows may have initiated the development of the modernHudut system (to the east of the lava flow) and contributedto the initiation of the Bozler river system (to the west ofthe lava flow) which today drains the area between theBurgaz and Sarnıc- plateaux. It is likely also that the

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valley lava dam

probable positionof dam breach

300

400

500

Tav an

600

650

B

300

400

500

600

650

{Fault zone}southward

down-dip migration fan sedimentbase of Ulubey Fm

Ahmetler Fm

SW NE

current river

He

igh

t m

OD

He

igh

t m

OD

Basement Rocks

0 1 km

A

Fig. 13. Schematic representation of a cross-section across the palaeo-Gediz valley: (A) prior to the onset of eruptions and (B) immediately after the first

eruption of Tavs-an.



eruptions of the Burgaz Bagtepe neck created a new lakefurther upstream in the Gediz.

An early phase of fluvial incision subsequent to theseeruptions appears to have been preserved upstream withina palaeomeander section (M1, Fig. 14).

4.3.1. Palaeomeander section M1

Buried gravels of typical palaeo-Gediz type composition,but containing significantly high basalt content (o10%),and up to 2m in thickness, outcrop along the eastern sideof an incised gully in the Burgaz plateau (Fig. 14A, M1).A continuous outcrop, with accurate heights surveyed atfour localities (1M1–4M1 Fig. 14A), indicates a consistentpalaeo-Gediz gravels/Ahmetler Formation contact at�144m (range 143.50–145.39m) above the datum level.These gravels can be observed to cut across the buriedterrace sequence and clearly postdate the buried terraces,their overlying fan sediment and the capping lava flowswhich emanate from the Burgaz Bagtepe neck. Despite theobvious younger age, the level of this gravel body is slightlyabove the pre-eruption terrace I valley floor which lies at�140m above the datum level.

Unlike the buried terrace gravels these outcrops exposecharacteristic sedimentary structures. Lateral accretionstructures at location 2M1 suggest deposition in a sinuouschannel, an interpretation supported by the thick (up to2m) preservation of fine-grained overbank sediments.Imbrication measurements on the gravels suggest flow

towards the north. The northward flowing river responsiblefor these gravel would quickly, within a few hundredmetres, encounter the present gully headwall formed in theAhmetler Formation and thus, although no return limbsediments are observed on the western side of the gully, it isreasonable to assume that this section represents apalaeomeander. There is an erosional bench at the samealtitude cut into the headwall of the present gully (5M1,Fig. 14A) and this level is also represented on the westernside of the current gully system by a flat erosional AhmetlerFormation contact with thick overlying slope sediment atlocation 6M1 (Fig. 14A). The interpretation of theseoutcrops as a palaeomeander is further supported by theircreation of a meander core to the south, forming the outlierbasalt outcrop of Kale Tepe (Figs. 2 and 14A).The fluvial sediments on the eastern limb, together with

the erosional bench of the western limb, are overlain by athick sequence (up to 10m) of basalt-rich slope sediment.The nature of this palaeochannel fill sediment denotes anunusual mode of infill but the time gap between meandercut-off and palaeochannel fill is unknown. The reason formeander cut-off is also elusive but a debris-flow depositoverlying the palaeo-Gediz sediments at 1M1 (Fig. 14B)may be a lahar, perhaps triggered by eruption of anupstream volcanic neck (e.g. the neck on Delihasan Tepe,Fig. 3). Alternatively this debris flow may have beentriggered by more localised landslide activity. Whatever itsorigin, this material would have blocked this routeway,assuming the cut-off had not already occurred, forcing thepalaeo-Gediz to the south of Kale Tepe. It is possible thatthe cut-off meander fill represents deposition in a lakeformed behind a lava dam caused by flows emanating fromthe Ibrahimaga Bagtepe neck downstream.

5. An end to quasi-equilibrium?

It has been argued that the buried high-level terracesystem of the palaeo-Gediz indicates a river system thatattained periodic quasi-equilibrium longitudinal profilesadjusted to the long-term regional uplift. Although thiscondition may have been possible when the system waslargely climate-controlled, could this state have beenmaintained after the system was so dramatically disturbedby volcanic events?Fig. 15 shows a schematic representation of the possible

effects on the palaeo-Gediz longitudinal profile in responseto repeated lava damming events. Effective lava damscreate upstream lakes (Hamblin, 1990), disrupting sedi-ment transport and thus requiring subsequent channeladjustment. The effect of natural dams can be estimatedwith reference to modern observations associated withartificial dam creation. In Fig. 15A we assume that theinitial terrace I profile is a graded profile (in quasi-equilibrium) adjusted to regional uplift. In Fig. 15Bdamming downstream creates a lake, thus raising the localbase-level upstream. On the upstream end of the lake,sediment flux builds a small delta composed of the more

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B

Ahmetler Formation

Palaeo-Gediz gravel 1M1

Lahar?

Slope sediment

51 52 53 54 55 56 57 58 59

74

75

76

77

78

Burgaz

M11

23

4

5

6

A

Fig. 14. (A) Location of Meander M1 section and (B) Exposures at

location 1M1.



coarser sediment grades. Immediately upstream of the deltaadjustments include localised aggradation and backfillleading to reduced gradients, although such changes donot progress far upstream. Often the reduced gradient inthese areas may result in a change in fluvial planform andthe development of a highly sinuous channel system. This istypical behaviour upstream of artificially created damstructures (Leopold and Bull, 1979). Downstream of thedam, once overspill begins, erosive power is increased dueto reduced sediment load (clear water erosion) and incisionis possible albeit that flood peaks may be reduced (Petts,1979). Furthermore, migration of nickpoints from down-stream stall in this area, amplifying the channel profileadjustments here with respect to those upstream of thedam. Once the lake drains (Fig. 15C) the former positionof the dam occupies a nickpoint that will migrate upstreaminto the former lake floor area. Furthermore, degradationof the upstream delta area will begin. In Fig. 15D weassume that the next lava dam occurs upstream of that in15B and that the adjustment of profile to the earlierlake drainage is incomplete. This time the upstream endof the lake is outside the area shown and incision is onceagain triggered but in the restricted area downstream ofthe dam.

The end result of this sequence is a longitudinal riverprofile that is still adjusting to the multiple dammingevents. The frequency of these events does not allowcomplete fluvial system adjustment, i.e. the time betweenevents is less than the system relaxation time (Brunsdonand Thornes, 1979) and thus a quasi-equilibrium profilecannot be achieved (Fig. 15D). This situation is amplifiedby the probable complex response (Schumm, 1979)generated by such events. This scenario leads to complexstratigraphical relationships. Even in the simple caseconsidered fluvial gravels of similar age could occur at avariety of different altitudes above the river.In the case of the palaeo-Gediz, the river was dammed

on numerous occasions during the period under study.Although the readily erodible nature of the AhmetlerFormation may eventually allow grade to be re-attainedonce disruption ceases, the intervening stratigraphicalsequence will be difficult to unravel without accurate agecontrol. This situation requires particularly careful atten-tion to be paid when attempting correlation; it is nottenable to continue with the simple altitudinal correlationsthat were possible on the earlier graded terrace system.Other means of correlation will be needed to establishreliable attribution. Furthermore, the complex profile

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downstream gradient increasedue to clear water erosion of bed

graded profileadjusted to regional uplift

headward erosioninto lake floor

incision offormer delta sediment

downstream gradient increasedue to clear water erosion of bed

deltaformation upstream gradient lowering

in response to rising base-level

Fig. 15. Schematic representation of longitudinal profile adjustments associated with repeated lava dam events. For details see text.



adjustments in the study reaches will have knock-on effectsupstream that will result in profile adjustments that lagthose in the study reach. This could be particularlyproblematic upstream in the palaeo-Gediz where the riverflows across more resistant basement rocks. Adjustments inthose reaches may considerably lag those of the studyreaches. Thus a simple altitudinal correlation of fluvialdeposits in far upstream reaches, based upon height abovethe present river, is unrealistic.

This observation has significance for using this sequenceto establish regional uplift rates (e.g. Bunbury et al., 2001).Assuming that the river re-attains grade after the firstphase of volcanism begins, it may be possible to use thepre-disruption and post-disruption levels to calculate thetime-averaged incision rate and thus infer the time-averaged uplift rate for this period. However, as theintervening levels represent dis-equilibrium conditions theycannot be used for this purpose as the incision rates do notequate with the uplift rate. As in Fig. 15D, during thisperiod it is likely that in most reaches in the study area theincision rates will be lower than the background uplift rate.Furthermore, the lack of reliable information betweengraded levels may constitute a considerable time intervalwhich could mask major changes in uplift rates and thuslead to an unreliable uplift history reconstruction. This willbe particularly significant if the intention is to reconstructlocalised block movements, especially where the blocksvary in erodibility and thus their ability to re-attain gradequickly. We hope to gain further understanding byattempting to model the nature of fluvial profile evolution;such an approach has yielded considerable insight insimilar situations (e.g. in Germany, Veldkamp et al., 2002).

6. Conclusion

The Plio–Pleistocene evolution of the modern Gedizriver system results from the interplay of on-going tectoniccontrols on fluvial system behaviour together with majorsediment/water supply changes resulting from river captureand climate changes. During different phases of thisevolutionary sequence these controls have worked collec-tively, as well as independently, to shape river networkdevelopment. Despite the substantial tectonic influences,the Early Pleistocene record preserves a signature ofchanges resulting from high-frequency climate change.Indeed the Pleistocene sequence exposed in the area northof Kula is remarkable. The fortuitous preservation of theburied Early Pleistocene terraces contains an archive offluvial system response to sediment/water supply changes,themselves a consequence of the obliquity-driven climatechanges of that period. This sequence suggests a dynamiclink between fluvial system behaviour and climate changein the Early Pleistocene. This type of record has not yetbeen widely recorded elsewhere, perhaps as a consequenceof the specific requirement for appropriate uplift condi-tions, high enough to allow discrete levels to form in eachcycle, but low enough to allow terrace formation and

prevent subsequent destruction of terrace fragments. Inthis case, initial burial by fan progradation also plays asignificant role in the preservation.The destruction of this dynamic link was inevitable once

volcanism began. The repeated damming of the trunk riverand its tributaries led to complex stratigraphic relation-ships. The sequencing of eruptions disrupted the timing ofthe incisional adjustment to the on-going regional uplift.Although some incision appears to be evident duringquiescent phases between volcanic events there is no reasonto assume that the timing of these events is governed byregional climate change. For most of the time during thisfirst phase of volcanism the river was being repeatedlydammed and its longitudinal profile adjustments wouldthus reflect these local base-level changes. The responses tothese events upstream and downstream of the study reachare, as yet, unknown.Our study of the Gediz sequence continues. Extensive

Middle and Late Pleistocene fluvial, lacustrine and volcanicsequences have already been recognised. Despite thechronology problems, the key to maximising the under-standing of this system is a comprehensive age estimationprogramme. We are currently engaged in an extensiveprogramme of surface exposure dating, together withfurther K–Ar/Ar–Ar age estimates on lavas. To this wewill add luminescence and aminoacid racemisation studiesfor the youngest components of the record. Furthermore,we have just embarked on a new research project(sponsored by the British Institute at Ankara, BIAA)which will exploit the Early Pleistocene record for itspalaeoenvironmental proxies. It is hoped that this workmay allow wider biostratigraphical correlation as well asprovide valuable insights into the nature of EarlyPleistocene climate changes in this region.The substantial results already obtained from this area

underline the potential of the Eastern Mediterraneanfluvial archive. IGCP449 has played a major part in theinitial attempts to unravel this record, thus demonstratingthe pivotal role that IGCP can play in furthering ourknowledge of fluvial system behaviour.

Acknowledgements

The authors would like to acknowledge the support ofNERC (via a small grant NER/B/S/2000/00678 to DM)and the University of Newcastle Research Fund during thisstudy. The British Institute for Archaeology in Ankara isalso thanked for their financial support (2005) and the loanof equipment, without which this work would not havebeen possible. This work forms a contribution to IGCP449‘Global correlation of Late Cenozoic fluvial deposits’ andits successor project IGCP518 ‘Fluvial sequences asevidence for landscape and climatic evolution in the LateCenozoic. Finally we would like to thank the referees ProfAdrian Harvey and Dr. Anne Mather for their useful andconstructive comments.



Appendix A. Supplementary materials

Supplementary data associated with this article can befound in the online version at doi:10.1016/j.quascir-ev.2006.01.037.

References

Aksu, A.E., Piper, D.J.W., Konak, T., 1987. Quaternary growth patterns

of the Buyuk Menderes and Kuc- uk Mederes deltas, Western Turkey.

Marine Geology 76, 89–104.

Borsi, S., Ferrara, G., Innicenti, F., Mazzuoli, R., 1972. Geochronology

and petrology of recent volcanics in the eastern Aegean Sea. Bulletin

Volcanologique 36, 473–496.

Bozkurt, E., Sozbilir, H., 2004. Tectonic evolution of the Gediz graben:

field evidence for an episodic, two-stage extension in western Turkey.

Geological Magazine 141, 63–79.

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.

Bridgland, D.R., Maddy, D., 2002. Global correlation of long Quaternary

fluvial sequences: a review of baseline knowledge and possible methods

and criteria for establishing a database. Netherlands Journal of

Geosciences 81, 265–281.

Bridgland, D.R., Philip, G., Westaway, R., White, M., 2003. A long

Quaternary terrace sequence in the Orontes River valley, Syria: a

record of uplift and of human occupation. Current Science 84,

1080–1089.

Brunsdon, D., Thornes, J.B., 1979. Landscape sensitivity and change.

Transactions of the Institute of British Geographers New Series 4,

463–484.

Bunbury, J.M., Hall, L., Anderson, G.J., Stabbard, A., 2001. The

determination of fault movement history from the interaction of local

drainage with volcanic episodes. Geological Magazine 138, 185–192.

Calvache, M., Viseras, C., 1997. Long-term control mechanisms of stream

piracy processes in Southeast Spain. Earth Surface Processes and

Landforms 22, 93–105.

Demir, T., Yes-ilnacar, I., Westaway, R., 2004. River terrace sequences in

Turkey: sources of evidence for lateral variations in regional uplift.

Proceedings of the Geologists’ Association 115, 289–311.

Ercan, T., 1993. Interpretation of geochemical, radiometric and isotopic

data on Kula Volcanics (Manisa—Western Anatolia). Geological

Bulletin of Turkey 36 (1), 113–129.

Ercan, E., Dınc-el, A., Metın, S., Turkecan, A., Gunay, E., 1978. Us-ak

Y +oresindeki Neojen Havzalarının Jeolojisi. Bulletin of the Geological

Society of Turkey 21, 97–106.

Ercan, E., Turkecan, A., Dınc-el, A., Gunay, E., 1983. Kula-Selendi

(Manisa) dolaylarının jeolojisi (Geology of Kula-Selendi (Manisa)

area). Jeoloji Muhendisligi 17, 3–28.

Erinc- , S., 1970. The young volcanic topography of the Kula-Adala area.

Ystanbul Universitesi Codrafya Enstitutu Dergisi 17, 7–22.

Eyidogan, H., Jackson, J., 1985. A seismological study of normal faulting

in the Demirci, Ales-ehir and Gediz earthquakes of 1969–70 in Westren

Turkey: implications for the nature and geometry of deformation in

the continental crust. Geophysical Journal of the Royal Astronomical

Society 81, 569–607.

Garcıa-Melendez, E., Goy, J.L., Zazo, C., 2003. Neotectonics and

Plio–Quaternary landscape development within the eastern Huerca-

l–Overa Basin (Betic Cordilleras, southeast Spain). Geomorphology

50, 111–133.

Geological Map of Turkey- IZMIR (1:500,000), 1973. Publication of the

Mineral Research and Exploration Institute of Turkey.

Hamblin, W.K., 1990. Late Cenozoic lava dams in the western Grand

Canyon. In: Beus, S.S., Morales, M. (Eds.), Grand Canyon Geology.

Oxford University Press, New York, pp. 385–433.

Harvey, A.M., Wells, S.M., 1987. Response of Quaternary fluvial systems

to differential epirogenic uplift: Aguas and Feos river systems,

southeast Spain. Geology 15, 689–693.

Harvey, A.M., Miller, S.Y., Wells, S.M., 1995. Quaternary soil and river

terrace sequences in the Aguas/Feos river systems: Sorbas basin, SE

Spain. In: Macklin, M.G., Lewin, J., Woodward, J.C. (Eds.),

Quaternary

Fluvial Systems in the Mediterranean Basin. Balkema, Rotterdam,

pp. 263–282.

Inci, U., 2002. Depositional evolution of Miocene coal successions in the

Soma coalfield, Western Turkey. International Journal of Coal

Geology 51, 1–29.

International Water Management Institute (IWMI) and General Direc-

torate of Rural Services (GDRS). Turkey, 2000. Irrigation in the Basin

Context: The Gediz Study. IWMI, Colombo, Sri Lanka.

Koc-yigit, A., Yusufoglu, H., Bozkurt, E., 1999. Evidence from the Gediz

graben for episodic two-stage extension in western Turkey. Journal of

the Geological Society of London 156, 605–616.

Kroon, D., Alexander, I., Little, M., Lourens, L.J., Matthewson, A.,

Robertson, A.H.F., Sakamoto, T., 1998. Oxygen isotope and sapropel

stratigraphy in the Eastern Mediterranean during the last 3.2 million

years. Proceedings of the Ocean Drilling Program, Scientific Results

160, 181–189.

Kuzucuoglu, C., 1995. River response to Quaternary tectonics with

examples from northwestern Anatolia, Turkey. In: Macklin, M.G.,

Lewin, J., Woodward, J.C. (Eds.), Quaternary Fluvial Systems in the

Mediterranean Basin. Balkema, Rotterdam, pp. 115–129.

Leopold, L.B., Bull, W.B., 1979. Base level, aggradation, and

grade. Proceedings of the American Philosophical Society 123,

168–202.

Lucchitta, I., Curtis, G.H., Davis, M.E., Davis, S.W., 2000. Cyclic

aggradation and downcutting, fluvial response to volcanic activity, and

calibration of soil-carbonate stages in the Western Grand Canyon,

Arizona. Quaternary Research 53, 22–33.

Maas, G.S., Macklin, M.G., Kirkby, M.J., 1998. Late Pleictocene and

Holocene river development in Mediterranean steepland environ-

ments, southwest Crete. In: Benito, G., Baker, V.R., Gregory, K.J.

(Eds.), Palaeohydrology and Environmental Change. Wiley, Chiche-

ster,

pp. 153–166.

Macklin, M.G., Lewin, J., Woodward, J.C. (Eds.), 1995. Quaternary

Fluvial Systems in the Mediterranean Basin. Balkema, Rotterdam.

Macklin, M.G., Fuller, I.C., Lewin, J., Maas, G.S., Passmore, D.G., Rose,

J., Woodward, J.C., Black, S., Hamlin, R.H.B., Rowan, J.S., 2002.

Correlation of fluvial sequences in the Mediterranean basin over the

last 200 ka and their relationship to climate change. Quaternary

Science Reviews 21, 1633–1641.

Maddy, D., Demir, T., Bridgland, D.R., Veldkamp, T., Stemerdink, C.,

Van der Schriek, T., Westaway, R., 2005. An obliquity-controlled

Early Pleistocene river terrace record from Western Turkey. Quatern-

ary Research 63, 339–346.

Maddy, D., Demir, T., Bridgland, D.R., Veldkamp, T., Stemerdink, C.,

Van der Schriek, T., Westaway, R., in press. The Early Pleistocene

development of the Gediz River, Western Turkey: An uplift-driven,

climate-controlled system? Quaternary International.

Mather, A.E., 1993. Basin inversion: some consequences for

drainage evolution and alluvial architecture. Sedimentology 40,

1069–1089.

Mather, A.E., Harvey, A.M., 1995. Controls on drainage evolution in the

Sorbas basin, southeast Spain. In: Macklin, M.G., Lewin, J.,

Woodward, J.C. (Eds.), Quaternary Fluvial Systems in the Mediterra-

nean Basin. Balkema, Rotterdam, pp. 65–76.

Mather, A.E., Silva, P.G., Goy, J.L., Harvey, A.M., Zazo, C., 1995.

Tectonics versus climate: an example from late Quaternary aggrada-

tional and dissectional sequences of the Mula basin, southeast Spain.

In: Macklin, M.G., Lewin, J., Woodward, J.C. (Eds.), Quaternary


pp. 77–88.

ARTICLE IN PRESSD. Maddy et al. / Quaternary Science Reviews 26 (2007) 2864–2882 2881


Ozaner, F.S., 1992. Detecting the polycyclic drainage evolution in Kula

region (western Turkey) using aerial photographs. ITC Journal

1992–3, 249–253.

Paton, S., 1992. Active normal faulting, drainage patterns and sedimenta-

tion in southwestern Turkey. Journal of the Geological Society of

London 149, 1031–1044.

Pazzaglia, F.J., 2004. Landscape evolution models. In: Gillespie, A.R.,

Porter, S.C. and Atwater, B.F. (Eds.), The Quaternary Period in the

United States. Developments in Quaternary Science, vol. 1, pp. 247–274.

Petts, G.E., 1979. Complex response of river channel morphology to

reservoir construction. Progress in Physical Geography 3, 329–362.

Purvis, M., Robertson, A.H.F., 2004. A pulsed extension model for the

Neogene–Recent E–W trending Alas-ehir Graben and the NE–SW trending

Selendi and Gordes Basins, western Turkey. Tectonophysics 391, 171–201.

Richardson-Bunbury, J.M., 1996. The Kula volcanic field, western Turkey:

the development of a Holocene alkali basalt province and the adjacent

normal-faulting graben. Geological Magazine 133, 275–283.

Rose, J., Meng, X., 1999. River activity in small catchments over the last

140 ka, northeast Mallorca, Spain. In: Brown, A.G., Quine, T.A.

(Eds.), Fluvial Processes and Environmental Change. Wiley, Chiche-

ster, pp. 91–102.

Sarıca, N., 2000. The Plio–Pleistocene age of the Buyuk Menders and

Gediz grabens and their tectonic significance on N–S extensional

tectonics in West Anatolia: mammalian evidence from the continental

deposits. Geological Journal 35, 1–24.

Schumm, S.A., 1979. Geomorphic thresholds: the concept and its

applications. Transactions of the Institute of British Geographers

New Series 4, 485–515.

Seyitoglu, G., 1997. Late Cenozoic tectono-sedimentary development of

the Selendi and Us-ak-Gure basins: a contribution to the discussion on

the development of east–west and north trending basins in western

Turkey. Journal of the Geological Society of London 134, 163–175.

Seyitoglu, G., Scott, B.C., 1994. Late Cenozoic basin development in west

Turkey: G +ordes basin tectonics and sedimentation. Geological

Magazine 131, 631–637.

Stokes, M., Mather, A.E., 2000. Response of Plio–Pleistocene alluvial

systems to tectonically induced base-level changes, Vera Basin, SE

Spain. Journal of the Geological Society of London 157, 303–316.

Stokes, M., Mather, A.E., Harvey, A.M., 2002. Quantification of

river-capture-induced base-level changes and landscape develop-

ment, Sorbas Basin, SE Spain. In: Jones, S.J., Frostick, L.E.

(Eds.), Sediment Flux to Basins: Causes, Controls and Conse-

quences, Geological Society, London, Special Publication, vol. 191,

pp. 23–35.

Veldkamp, A., van den Berg, M.W., van Dijke, J.J., van den Berg van

Saparoea, R.M., 2002. Reconstructing Late Quaternary fluvial process

controls in the upper Aller Valley (North Germany) by means

of numerical modelling. Netherlands Journal of Geoscience 81,

375–388.

Visera, C., Fernandez, J., 1992. Sedimentary basin destruction inferred

from the evolution of drainage systems in the Betic Cordillera,

Southern Spain. Journal of the Geological Society of London 149,

1021–1029.

Wenzens, E., Wenzens, G., 1995. The influence of Quaternary tectonics on

river capture and drainage patterns in the Huercal–Overa basin,

southeastern Spain. In: Macklin, M.G., Lewin, J., Woodward, J.C.

(Eds.), Quaternary fluvial systems in the Mediterranean basin.

Balkema, Rotterdam, pp. 55–64.

Wenzens, E., Wenzens, G., 1997. The influence of tectonics, sea-level

fluctuations and river capture on the Quaternary morphogenesis of the

semi-arid Pulpi Basin (southeast Spain). Catena 30, 283–293.

Westaway, R., 1993. Neogene evolution of the Denizli region of western

Turkey. Journal of Structural Geology 15, 37–53.

Westaway, R., Pringle, M., Yurtmen, S., Demir, T., Bridgland, D.R.,

Maddy, D., 2003. Pliocene and Quaternary surface uplift of western

Turkey revealed by long-term river terrace sequences. Current Science

84, 1090–1101.

Westaway, R., Pringle, M., Yurtmen, S., Demir, T., Bridgland, D.R.,

Rowbottom, G., Maddy, D., 2004. Pliocene and Quaternary regional

uplift in western Turkey: the Gediz river terrace staircase and the

volcanism at Kula. Tectonophysics 391, 121–169.

Woodward, J.C., Lewin, J., Macklin, M.G., 1995. Glaciation, river

behaviour and the Palaeolithic settlement of upland northwest Greece.

In: Macklin, M.G., Lewin, J., Woodward, J.C. (Eds.), Quaternary


pp. 115–129.


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The Pliocene initiation and Early Pleistocene volcanic disruption of the palaeo-Gediz fluvial...

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