Quaternary colluvium in west-central Anatolia: sedimentary facies and palaeoclimatic signifcance

Quaternary colluvium in west-central Anatolia: sedimentaryfacies and palaeoclimatic signi®cance

W. NEMEC1 and N. KAZANCI2

1Geological Institute, University of Bergen, N-5007 Bergen, Norway (E-mail: [email protected]),and 2Department of Geological Engineering, University of Ankara, TR-06100 BesËevler/Ankara, Turkey(E-mail: [email protected])

ABSTRACT

The Quaternary colluvial aprons in Lake EgÆirdir area, Taurus Mountains,

consist of steep coalescent fans, up to 17±20 m thick and 350±450 m in plan-

view radius, and the sedimentary succession comprises four lithostratigraphic

divisions. The basal red±brown colluvium consists of a chaotic, bouldery

fan-core rubble covered with bedded, openwork to matrix-rich gravel, whose

deposition is attributed to rockfalls and cohesive debris¯ows, with minor

grain¯ows and sheetwash processes. The middle part of this division contains

interbeds of early Pleistocene tephra. The overlying light-grey colluvium

consists of bedded gravel with numerous palaeogullies and its deposition is

attributed to water¯ow, rockfalls and cohesive debris¯ows. The younger,

medium-grey colluvium consists of strati®ed pebbly sand interspersed with

cobble/boulder gravel and its deposition is attributed to sheetwash processes

accompanied by rockfalls and wet snow¯ows/slush¯ows. A bulk-pollen

radiocarbon date indicates Late WuÈ rm age. The youngest, yellow±grey

colluvium consists of bedded, mainly pebbly and openwork gravel, whose

deposition is attributed to dry grain¯ows, rockfalls and minor cohesive

debris¯ows. Based on the sedimentary facies assemblages and available

isotopic dates, the four colluvial divisions are correlated with the following

stages of the region's climatic history: (1) the latest Pliocene to Early

Pleistocene stage of warm±humid climate with pronounced phases of drier

conditions; (2) the Late Pleistocene stage of colder climate, with alternating

phases of higher and lower humidity; (3) the last glacial (WuÈ rm) stage of

coldest climate; and (4) the Holocene stage of warm semi-arid climate. It is

concluded that colluvial depositional systems bear a valuable proxy record of

climatic changes and regional geoclimatic differences.

Keywords Colluvium, debris¯ow, Quaternary, rockfall, sheetwash, Turkey.

INTRODUCTION

Colluvium is a slope-waste clastic material,typically coarse grained and very immature,deposited in the lower part and foot zone of amountain slope or other topographic escarpmentand brought there chie¯y by sediment±gravityprocesses (Holmes, 1965; Bates & Jackson, 1987;Blikra & Nemec, 1993a). Colluvial deposits occurin high-relief terranes in virtually all climatic

zones and have long been recognized by geomor-phologists as an important product of the slope-reducing processes of mass wastage, typicallyincluding a range of avalanches (Blikra & Nemec,1998). Modern geomorphological research oncolluvium dates back to Gilbert (1877) and hiscontemporaries, and the literature abounds inrelevant studies (see review by Blikra & Nemec,1998). The wide interest in the topic is due partlyto the fact that slope avalanches pose a serious

Sedimentology (1999) 46, 139±170

Ó 1999 International Association of Sedimentologists 139

hazard to many populated areas and mountainresorts. Furthermore, colluvium may be avaluable record of tectonic activity (Murton &MacLeod, 1987; Nelson, 1992; Nemec, 1992;McCalpin et al., 1993; Macdonald et al., 1996;Fielding et al., 1997), and the Holocene col-luvium has also been recognized as bearingimportant signatures of climatic changes (Gerson,1982; Pope & van Andel, 1984; Gerson & Gross-man, 1987; Blikra & Nemec, 1993a,b; Frenzelet al., 1993; Bertran et al., 1994; Evans & Clague,1994; GonzaÂlez DõÂez et al., 1996; Matthews et al.,1997; Blikra & Nemec, 1998).

It is therefore surprising that colluvial deposi-tional systems have thus far attracted relativelylittle sedimentological research. Case studies arefew, there is no corresponding facies model, andcolluvium is seldom even mentioned in sedimen-tological textbooks. One can think of three mainreasons why colluvial fans have been regarded bysedimentologists as a proverbial `ugly duckling'among the clastic depositional systems. Firstly,the seemingly `chaotic' nature of colluvial depos-its made them seem almost intractable by con-ventional facies analysis. Secondly, there hasbeen the common assumption that colluvialdeposits `are seldom preserved in the geologicalrecord because they are subject to erosion andremoval' (Selby, 1994, p. 83). Thirdly, the lack of®eld studies meant a lack of diagnostic sedimen-tary criteria, and hence colluvium has seldombeen recognized in the stratigraphic record.

However, the occurrence of colluvium in theancient record may be far more common than hasgenerally been assumed by geologists, and thereare reasons to suspect that many of the ancient`basin-margin breccias', `proximal fanglomerates',`debris slopes', `footwall fans' and `mass-wastageaprons' may in fact include colluvial deposits ±subaerial, transitional or submarine. For example,deposits qualifying as colluvial, although notnecessarily described as such, have been reportedfrom the Tertiary of Arizona (Yarnold, 1993),Spanish Betics (Midtun, 1991; Kjñrefjord, 1992),SW Turkey (Nemec et al., 1998b), SE Cyprus(Murton & MacLeod, 1987; Eaton & Robertson,1993) and SE Korea (Choe & Chough, 1988); theCretaceous of NE Scotland (Andrews et al., 1990;Lawrence, 1993), the Canadian Queen CharlotteIslands (Higgs, 1990) and Baja California (White &Busby-Spera, 1987; Busby-Spera, 1988; Morriset al., 1989); the Upper Jurassic of NE Scotland(Theriault & Steel, 1995) and the northern NorthSea (Nemec, 1992; Fñrseth et al., 1995); theUpper Permian of Queensland, Australia (Field-

ing et al., 1997); the Devonian of NE Scotland(Andrews et al., 1990); the Lower Palaeozoic ofAlberta (Trotter & Hein, 1988) and southernJordan (Powell et al., 1993); and the UpperPrecambrian of northern Greenland (Collinsonet al., 1989). In short, colluvial deposits do occurin the ancient record, and colluvial systemscertainly deserve sedimentological research andfull recognition.

The present study of the Quaternary colluviumin west-central Anatolia is a contribution to thesedimentological understanding of colluvial de-positional systems and the palaeoclimatic signif-icance of their sedimentary facies. The localcolluvial record is described and interpreted interms of the depositional processes involved, andthe physical implications of the colluvium for themountain slope conditions are compared furtherwith the region's climatic history derived fromother types of data. The avalanche terminologyused is according to Blikra & Nemec (1998).

STUDY AREA

Regional geological setting

The study area is in the northern marginal zone ofthe Taurus Mountains, an Alpine orogen branchthat extends west±east across southern Anatolia(Dewey & SËengoÈr, 1979; Mercier et al., 1979; LePichon & Angelier, 1982; Dilek & Moores, 1991;Yõlmaz et al., 1994). The orogen is dominated byMesozoic limestones, but includes other meta-morphic rocks. The Lake EgÆirdir area, where thecolluvium has been studied, is c. 25 km NE ofIsparta (Fig. 1), within the northern tip of theorogen's sharp structural bend known as theIsparta Angle, or Courbure d'Isparta (Ricou et al.,1974; Poisson et al., 1984; Waldron, 1984). Thislarge-scale cuspate structure is thought to repre-sent a Late Cretaceous intercratonic transformsuture transverse to the trend of the Palaeogeneorogenic belt (Dilek & Moores, 1991).

The Anatolian craton was assembled by thetectonic suturing of Africa-derived microconti-nents and associated nappe emplacement duringthe Alpine orogeny (Dilek & Moores, 1991). Thecompound craton was dominated by north±southcompression until Early Miocene time, when thetectonic regime changed to extensional, causingorogen collapse and inviting a marine transgres-sion (Mercier et al., 1979; Dixon & Robertson,1984; OÈ zguÈ l, 1984; Akay et al., 1985). A younger,

140 W. Nemec and N. Kazancõ

Ó 1999 International Association of Sedimentologists, Sedimentology, 46, 139±170

Late Neogene pulse of mild westerly compressioncould be related to the westward tectonic escapeof the Anatolian craton (Dewey & SËengoÈr, 1979;SËengoÈr et al., 1985). The tectonic extension isthought to have been a regional block-faultingphenomenon (SavasËcËin, 1990), probably analo-gous to the broad back-arc stretching in theadjacent Aegean Sea region (Robertson & Grasso,1995). As a result of the continued extension, themountain belt evolved into a mosaic of horsts andsmall grabens, whose morphology has furtherbeen modi®ed by karstic processes.

Lake EgÆirdir

Lake EgÆirdir (Fig. 1, top right) is the southern partof a large, bipartite intramontane lake with a totalsurface area of 468 km2 and water level at analtitude of 916 m. The local bedrock is fracturedMesozoic limestone, chie¯y metamorphic, repre-senting an autochthonous platform and portionsof the overlying Antalya nappe (Brunn et al.,1971; Waldron, 1984). The lake is surrounded byhorst-type mountain ridges of the Anamas DagÆ to

the east, the Barla DagÆ to the west and the DavrasDagÆ to the south. Their highest parts are in excessof 1800 m. The colluvium around the town ofEgÆirdir is associated with the slopes of MountSivri (Fig. 1, bottom), which is a prominent spurof the Davras DagÆ, nearly 1750 m high.

The lake was apparently formed by run-offaccumulation in a tectono-karstic depression atthe con¯uence of three grabens: the NNW-trend-ing Anamas Graben, the N-trending KovadaGraben and the NE-trending EgÆirdir Graben (In-andik, 1965; KocËyigÆit, 1983; see Fig. 3 in Nemecet al., 1998a). The lake's coastal morphology anduneven bottom topography, including the EgÆirdirpeninsula and adjacent small islands, are thoughtto be a result of karstic collapses (AlagoÈz, 1944;Lahn, 1946, 1948). Ardel (1951) suggested that theEgÆirdir±Hoyran lake was formed by the collapseof a karstic polje.

The water depth averages 6 m, reaching 8 m inLake Hoyran and 16á5 m in Lake EgÆirdir. Themodern lake level is fairly stable, with minorseasonal changes and no coastal ¯ooding, becauseof the numerous karstic sinkholes along the coast

Fig. 1. Locality map of the Quater-nary colluvial aprons in EgÆirdir area,west-central Anatolia, showing thelocal topography and the two studyareas referred to in the text. Thecolluvial aprons are arrays of co-alescent fans, with depositionalslopes of 30±45°; the underlyingbedrock slope is mainly 50±60°.

Quaternary colluvium in west-central Anatolia 141


and a canal link with Lake Kovada to the south.Sporadic lake-level rises, by up to 1á2 m inhistorical times, probably marked occasionswhen the drainage capacity of the undergroundkarstic network was exceeded by run-off due toexceptionally abundant winter snow. There areno raised beach terraces or other evidence toindicate that the lake level has ever stood higherthan c. 917á5 m.

The age of the EgÆirdir±Hoyran lake is uncertain.This lacustrine basin has traditionally been in-terpreted as a Pleistocene `pluvial' lake (AlagoÈz,1944; Lahn, 1946, 1948; Inandik, 1965) or possi-bly an early Holocene feature (Ardel, 1951).However, KocËyigÆit (1981, 1983) concluded thatthe tectonic grabens hosting the lake were prob-ably formed in the Late Pliocene time, and it isalso worth noting that the history of many otherAnatolian lakes, including the adjacent Burdurand NigÆde±Kayseri basins, dates back to thePliocene time (Erol, 1969; Innocenti et al., 1975;Erol, 1978, 1984; Karaman, 1986; Kazancõ, 1988;Erol in MTA, 1997). The present study indicatesthat the coastal escarpments of Lake EgÆirdir,apparently formed by karstic collapses, began tobe covered with colluvium in the latest Pliocenetime. The lake may have formed around the sametime, or be younger. In short, the chronostratigra-phy of the lake deposits is unknown, and thelowest outcrops of the ¯anking colluvial aprons,

Fig. 2. Portions of the colluvial aprons in EgÆirdir area:(A) western part of the apron in area 1, and (B) southernpart of the apron in area 2 (cf. locality map in Fig. 1).

Fig. 3. Upslope views of: (A) two coalescent fans in the eastern part of the colluvial apron in area 1, and (B) a fan inthe colluvial apron in area 2, showing the basal, chaotic fan-core colluvium overlain by bedded colluvium.



c. 6 m above the lake level, show no lacustrineintercalations.

Modern climatic conditions

The study area is in the transition zone betweenthe forested, high Taurus Mountains to the southand the arid steppe highland of central Anatoliato the north (Roberts & Wright, 1993). Themountain zone is covered with a Mediterraneanforest dominated by pine and cedar, and has amean annual precipitation in excess of 600 mm.The rugged highland to the north is covered witha steppe forest, ranging between an open, xericwoodland (deciduous pine, oak, pistachio, juni-per and abundant shrubs) and a typical steppicassociation of herbs, shrubs and scattered trees.The precipitation in west-central Anatolia iscontrolled by barometric depressions that formnear the Aegean coast, or around Cyprus, andmove eastwards to the Caspian Sea area (Schwei-zer, 1975). Mean annual precipitation ranges from300 to 600 mm. The meteorological station inAfyon, north of EgÆirdir, shows a mean annualprecipitation of 478 mm, with mean temperaturesaround 0°C for January and 22°C for July. Thehigh mountains are covered with snow in thewinter, and a short-lived snow cover in EgÆirdirarea occasionally reaches 60 cm in thickness. Thelake never freezes over, but a coastal ice-footforms during colder winters, particularly in thenorthern part of Lake Hoyran.

The modern snowline is at an altitude ofc. 3100 m in the mountains of northern Anatolia,but rises to c. 4200 m in the eastern TaurusMountains. The snowline in the central andwestern Taurus Mountains is at intermediatealtitudes, generally decreasing towards the west(ErincË, 1952). In the study area, the snowline is atc. 3500 m, but was probably much lower in theLate Pleistocene time. The Quaternary climatichistory of the region, based on palynological andpalaeolimnological data, is reviewed in a subse-quent section and further used as a framework forthe palaeoclimatic evaluation of the colluvialstratigraphic record.

THE EGÆ IÇRDIÇR COLLUVIUM

The colluvium in the EgÆirdir area includes twoaprons, associated with the northern and theeastern slope of Mount Sivri (see areas 1 & 2 inFig. 1, bottom). The aprons consist of coalescent

colluvial fans (Figs 2 and 3A), whose plan-viewradii are in the range of 350±450 m. The marblebedrock has local slopes in excess of 50°, and thefan depositional slopes are mainly 30±35°, reach-ing 46° in apical zones. The colluvial sedimentarysuccession is well exposed in road-cut sections,up to 10±15 m high.

The deposits are bedded, composed of imma-ture gravel and minor sand. Marker tephra bedsindicate that the depositional axes of the aggrad-ing fans have shifted slightly during the sedi-mentation, whereby the thickest parts of thesuccessive bed packages (depositional lobes) areoften offset relative to one another. The cumula-tive stratigraphic thickness of the colluvium thusreaches 25±26 m, although the aprons are nomore than 17±20 m thick.

The colluvial succession shows four distinctlithostratigraphic divisions, de®ned by the sed-iment colour and differing facies assemblages(Figs 4 and 5). The consecutive divisions, re-ferred to as colluvia A, B, C and D, are describedand interpreted below. The descriptions followconventional sedimentological terminology (Col-linson & Thompson, 1982). The clast fabricnotation is according to Harms et al. (1975) andthe colour code refers to the standard GSA RockColor Chart.

Colluvium A (red±brown)

This lower division of reddish-brown colluviumis the thickest and most extensive. It locallyconstitutes the bulk of the colluvial succession, asthe younger divisions are thinner and pinch outin places.

Colluvium A are gravelly deposits ranging frompebbly to bouldery and from matrix-rich toopenwork. Their colour is mainly red±brown(10R 5/4), although the openwork gravel bedsare paler, often yellow±brown (10Y 6/2) toyellow±grey (5Y 7/2). The muddy sand matrixcontains pollen, but mainly degraded beyondgeneric identi®cation.

Chaotic basal colluvium

The basal core part of at least some of thecolluvial fans consists of a chaotic accumulationof extremely immature, reddish-brown boulderygravel, locally up to 7±8 m thick (Fig. 3B). Thisbasal colluvium is the coarsest, rich in boulderblocks up to several metres in length. Manyblocks show distinct palaeo-weathering features,such as one-sided rotting and broken cavities



®lled with older calcitic precipitates and/or terrarossa mud. The colluvium has no recognizableinternal bedding, but the gravel texture on anoutcrop scale varies from clast- to matrix-sup-ported. Some large interstices are open, devoid ofsediment. It is uncertain whether all the colluvialfans have such bouldery cores, because thesebasal deposits are buried in the inner part of a fan,exposed in a few cases only.

These are the oldest colluvial deposits in thestudy area. Their textural heterogeneity andabundance of boulder blocks suggest depositionby a series of large avalanches, ranging fromrockfalls to cohesive debris¯ows, apparently re-lated to the formation of the local escarpmentsand slope ravines. The volume and extremeimmaturity of the rubble indicate major collapses

of a deeply weathered and karsti®ed bedrock. Theoccurrence of earliest Pleistocene tephra in theoverlying bedded deposits (see below) suggeststhat the colluvial sedimentation probably com-menced in the latest Pliocene time.

Bedded colluvium

The overlying reddish-brown deposits, althoughvery immature, are well-bedded and contain fewboulders larger than 1 m. These deposits are littlemore than 2±4 m thick where covering directlythe bouldery core of a colluvial fan, but thicken toas much as 14±17 m on the core's ¯anks (Fig. 3B)and down-dip slope (Fig. 3A). The beddeddeposits thus constitute the bulk of colluvium Ain most outcrops (Figs 5 and 6).

Fig. 4. Generalized lithostratigraph-ic pro®le of the EgÆirdir colluvium.The thicknesses of the whole col-luvium and its individual litho-stratigraphic divisions are laterallyvariable, due to the morphology ofthe fans and the shifting of theirdepositional axes. Likewise, thecolluvial deposits separating the te-phra have a varied thickness, andthe tephra units, particularly theupper one, locally pinch out due tocontemporaneous erosion. Thissummary pro®le gives the maximummeasured thicknesses.



Importantly, the lower middle part of thiscolluvium contains two units of volcanic tephra(Fig. 4), whose K±Ar isotopic dates of 1á50 � 0á18and 1á38 � 0á13 Ma indicate earliest Pleistoceneage. The tephra are light grey (N7), slightly bluishin colour, occur in both aprons and are importantstratigraphic markers. They are thought to havebeen derived from the GoÈlcuÈk volcano nearIsparta (Fig. 1, top right), and their detaileddescription and interpretation are given else-where (Nemec et al., 1998a).

The reddish-brown colluvium consists ofalternating lenticular beds of pebbly to boulderygravel, whose texture varies from matrix-rich toclast-supported and commonly openwork(Figs 5, 6 and 7). Four sedimentary facies havebeen distinguished and attributed to differentdepositional processes (see facies A1±A4 in(Figs 7±11).

Facies A1 (debris ¯ow deposits)

This facies constitutes up to 40±45 vol% of thebedded red±brown colluvium. The deposits arebeds of matrix-supported gravel, pebbly tocobbly, locally bouldery. The measured bedthicknesses range from c. 10 to 130 cm and themaximum clast sizes range from 4 to 45 cm. Matrixis mainly an unsorted, granule-rich muddy sandor sandy mud, red±brown in colour. The gravelbeds are lenticular, but relatively extensive, up to10±12 m wide and 25±30 m long, respectively, insections transverse and parallel to the downslopedirection (Figs 6 and 7). The bases of the beds arenon-erosive and their geometries re¯ect deposi-tional adjustment to substratum morphology.Many lenses are convex upwards, draping pre-existent mounds (Fig. 7A). The downslope pinch-out of the beds tends to be much more abrupt than

Fig. 5. A transverse outcrop sectionof a colluvial fan in area 2, showingthree successive lithostratigraphicdivisions: colluvium A (red±brown),colluvium B (light grey) and col-luvium C (medium grey). The pal-aeotransport direction is towardsthe viewer.



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their upslope thinning, with the down-dip partsof many beds `swollen' and occasionally richer incoarsest debris. Some beds consist of polymodaldebris, are relatively thick, rich in matrix, andcontain `¯oating' cobbles or boulders (Fig. 10),whereas others are thinner, pebbly and oftennearly clast-supported (Fig. 11). Many beds showa `coarse-tail' inverse grading, with the lower partdevoid of large clasts (Figs 8±11). Conspicuously,the matrix-rich gravel beds of facies A1 overliethe openwork gravels of facies A2 and A3 withoutany evidence of a downward percolation of the®ne-grained matrix (Figs 10 and 11). Clast fabricis disorderly, but isolated cobbles and bouldersshow an a(p) or a(p)a(i) orientation (Fig. 10A).The bed thicknesses and maximum clast sizesshow signi®cant statistical correlation (Fig. 12).

On the basis of their characteristics, the depos-its of facies A1 are attributed to cohesive de-bris¯ows of high to moderately high viscosity(Nemec & Steel, 1984; Blikra & Nemec, 1998). It isknown that such ¯ows `can move across open-work pebble or cobble beds without depositing®ne sediment in the voids between the gravel

particles' (Wasson, 1979, p. 309/Fig. 3C). Thethicker, coarser and polymodal debris¯ows arethought to have been derived by gravitationalfailures of the weathering bedrock cover from themountain ravines and adjacent slopes, whereasthe thinner, pebbly debris¯ows probablyrepresent failures of the fan-head accumulationsof rockfall gravel (see below), illuviated with sandand mud by slopewash. Illuviation, or the perco-lation of ®nes into openwork gravel, is commonin modern fan apices.

Facies A2 (rockfall deposits)

This facies constitutes 30±35 vol% of the beddedred±brown colluvium. The deposits are beds ofclast-supported and predominantly openworkgravel, ranging from cobbly to bouldery and20±150 cm in thickness. The beds are lenticular,mainly 3±9 m wide and 6±15 m in downslopeextent (Figs 6 and 7). Their bases are non-erosive,and their geometries indicate depositional adjust-ment to local substratum morphology. In verticalsections parallel to the dip direction, these beds

Fig. 6. Transverse outcrop sections of colluvial fans in area 1 (A) and area 2 (B), showing portions of the bedded red±brown colluvium A. The palaeotransport direction is towards the viewer. Note the lenticular geometry of the al-ternating beds of openwork and matrix-supported gravel; LTU is the lower tephra unit (Fig. 4).



show conspicuous upslope ®ning, with a rela-tively thick, bouldery or cobbly `head' passinginto a pebbly `tail' that gradually pinches outwhile ®ning in the upslope direction (Fig. 7). Thebeds commonly also show an upward ®ning, ornormal grading, in the direction normal to theirbases (Figs 7±12). Due to these inherent texturaltrends, it is possible to recognize that most of thethicker units of facies A2 are composite, com-prised of two or more successive beds whosedownslope `heads' have been amalgamated(Fig. 7B). Many beds are stacked upon oneanother, or on beds of other facies, in an `imbric-ate' fashion, dipping upslope (Fig. 7). Clast fabricis rather disorderly, although boulders and largecobbles often show an a(t) or a(t)b(i) `rolling'orientation (Figs 6 and 7). The pebbly upslope`tails' of the beds (Fig. 7), although clast-support-ed, are commonly ®lled with a muddy sand,which has in some cases percolated less thanhalfway down into the bed. Where underlyingredeposited tephra, the openwork gravel has its

top ®lled with ash (Fig. 13). The voids in the bed`head' parts show post-depositional calcitic mic-rostalactites (Fig. 14).

The characteristics of facies A2 indicate depo-sition from rockfalls (Blikra & Nemec, 1998). Thepronounced `head-and-tail' structure of the gravelbeds is due to the relatively free segregation of thetumbling clasts according to their individualweight, or momentum, whereas the apparentnormal grading re¯ects the avalanche's frontaldeposit having been overridden by the slower-moving, ®ner-grained `tail'. The in®ll of the `tail'gravel with muddy sand or ash is secondary, dueto contemporaneous slopewash.

Facies A3 (grain¯ow deposits)

This facies is subordinate, constituting less than15 vol% of the bedded red±brown colluvium.The deposits are lenses of clast-supported, main-ly openwork gravel that ranges from pebbles tosmall cobbles in size and characteristically shows

Fig. 7. Longitudinal outcrop sec-tions of colluvial fans in area 1,showing portions of the beddedcolluvium A. The facies symbols(A1±A4) are as in the text; LTU isthe lower tephra unit. The palaeo-transport direction is to the left, atc. 15° (A) and 25° (B) out of thephotograph. Note the lenticular ge-ometry and common `imbricate'stacking of the openwork and ma-trix-supported gravel beds.



inverse grading (Figs 7A, 9B, 10A & C, 11A±C).These lenticular beds are up to 20±50 cm thick,and are 3±6 m wide in transverse sections and 5±15 m in downslope extent. Clast fabric is a(p) ora(p)a(i) in the coarser gravel, but shows littleorder in pebbly beds. The bed bases are non-erosive, and some beds have locally coveredsubstratum convexities (Fig. 11A±C). The basalparts of many beds show a muddy sand in®ll,particularly in upslope segments.

The characteristics of facies A3 indicate depo-sition from grain¯ows (Lowe, 1976; Nemec &Steel, 1984), probably mainly wet. The limitedmodal grain size of the gravel suggests resedi-mentation of fan-head deposits. It is likely thatthe fan-head accumulations of the pebbly rockfall`tails' tended to fail when lubricated by rainwaterand/or shaken by a descending rockfall ava-lanche. The basal muddy sand in®ll, typicallyrelated to bed-sole depressions, suggests perco-lating water run-off.

Facies A4 (sheet¯ow deposits)

This facies constitutes less than 10 vol% of thebedded red±brown colluvium. The deposits arelenses of ill-sorted, very coarse to pebbly sand(Fig. 6) with faint to distinct plane-parallel strat-i®cation (Figs 7A, 8, 9B, 11B). The lenticular bedsare 5±25 cm thick and 1±3 m in lateral extent;have mainly ¯at tops and concave-upward, weak-ly erosive bases; and occasionally contain isolat-ed cobbles or boulders (Fig. 11B).

The characteristics of facies A4 indicate trac-tional deposition from poorly con®ned water¯ow,apparently in the upper ¯ow regime, which pointsto sheet¯ow processes (Blikra & Nemec, 1998). Bedgeometries suggest ®lling of local sur®cial depres-sions. The scattered cobbles and boulders mayrepresent contemporaneous rockfalls, as the latterprocesses on modern slopes often involve largeclasts tumbling downfan in isolation. Some of theoutsized clasts may have rolled down from theupper slope as a result of the sheet¯ow.

Colluvium B (light grey)

The overlying colluvium B (Fig. 4) is nearly aswidespread as colluvium A, but generally thinner,only up to 5á5 m in thickness. It forms broad lenses(coeval depositional lobes) whose coalescence

Fig. 8. Detailed log through a portion of the beddedcolluvium A in area 1.



zones are seldom more than 1±1á5 m thick. Thelower boundary varies from conformable, althoughpitted with scours (Figs 5 and 15A), to dis-conformable and distinctly erosive (Fig. 15B).The erosive base is limited to those apron sectors

where colluvium B has ®lled in depressionsbetween the coalesced lobes of colluvium A, witha compensational offset of the maximum thicknesszones. The colour of colluvium B is mainly lightgrey (N7) to medium±light grey (N6), but pale

Fig. 9. Detailed logs through two different portions of the bedded colluvium A in area 2, showing: (A) a typicalalternation of rockfall and cohesive debris¯ow deposits, and (B) the full range of facies, including the subordinategrain¯ow and sheetwash deposits whose occurrences are more local.



yellow±brown (10Y 6/2) in some beds. The col-luvium is bedded, composed of immature, mainlypebbly to cobbly gravel whose texture varies frommatrix-rich to clast-supported and openwork(Fig. 16). There are also common thinner beds ofgranule gravel and pebbly sand. The matrix con-tains herbaceous and tree pollen, but the materialis strongly degraded, unsuitable for detailed anal-ysis (S. Peglar, personal communication, 1996).

Three sedimentary facies have been distin-guished in colluvium B and ascribed to differentdepositional processes (see facies B1±B3 inFig. 16).

Facies B1 (water¯ow gullies and sheet¯owdeposits)

The most conspicuous feature of colluvium B isthe abundance of relatively deep and narrowscours, often multiple (Figs 5 and 15A). They aremainly V-shaped, 0á7±1á8 m deep, have steppedpro®les and apparently represent gullies formedby ¯owing water, although their sedimentaryin®ll is often heterogeneous and not necessarilywaterlain (Fig. 16). These scours, although not afacies in a strict sense of the term, clearlyrepresent a speci®c state of the sedimentation

Fig. 10. Close-up details of thebedded colluvium A. The faciessymbols are as in the text. The pal-aeotransport directions are to theright (A) and towards the viewer (B& C).



process ± an erosive water¯ow ± and are thusconsidered here jointly with other water¯owproducts. The latter include lenses of strati®ed,ill-sorted coarse sand, 5±30 cm thick, generallyrich in pebbles and/or granules. These depositsare common within the palaeogullies, usuallyintercalated with facies B2 and/or B3, but occuralso as thin lenses outside those channels(Fig. 16). This facies constitutes c. 15±25 vol%of colluvium B.

The deposits of facies B1 are similar to those offacies A4 (see above) and attributed to sheet¯owprocesses. The palaeogullies indicate phases ofhigh sur®cial run-off and are thought to represent`gully gravure' (Bryan, 1940; Mills, 1981; Osterk-amp & Toy, 1994): a rill-and-®ll process of

autohealing slope recession, in which coarse,untransportable debris is deposited in a gullyformed by erosion of a less-resistant material. Thegully, or rill channel, becomes a receptacle foravalanche deposits, including rockfall debris. Theconduit and the high ®ltration capacity of rockfallgravel restrict the sur®cial run-off, while thecoarse in®ll acts as a local slope armour, mini-mizing further erosion; the slope thus stabilizes.However, the coarse debris entraps ®ner sedimentand the permeability of the gully ®ll decreases,whereby the run-off becomes diverted to theperiphery of the debris-plugged conduit. Thein®ll thus initially inhibits gully expansion, butlater expedites it. During high run-off, the loci ofscouring are near the gully margins, causing

Fig. 11. Close-up details of thebedded colluvium A. The faciessymbols are as in the text; LTU isthe lower tephra unit (Fig. 4). Thepalaeotransport direction is towardsthe viewer (A±C) and to the left, atc. 15° out of the photograph (D).



erosion of the less-resistant material and leadingto gully widening (cf. Fig. 15A). The process iscompleted when the contemporaneous avalanch-es eventually ®ll up and bury the gully. The run-off then shifts and proceeds elsewhere on the fansurface. The shifting is more frequent when thegullies are plugged by cohesive debris¯ows,rather than rockfalls (cf. Fig. 16).

Facies B2 (debris¯ow deposits)

This facies constitutes up to 45±50 vol% ofcolluvium B and occurs both outside and withinthe palaeogullies (Fig. 16). The deposits arelenticular beds of pebbly, occasionally cobbly,immature gravel whose texture ranges from ma-trix-supported to very matrix-rich. The muddysand matrix is slightly rubi®ed, rendering thedeposits pale yellow±brown in colour. The gravellenses are mainly 10±40 cm thick and 1±5 mwide; their downslope extent cannot be estimatedfrom the small outcrops, but is unlikely to exceed30 m. Many beds at least locally show `coarse-tail'inverse grading, with `¯oating' outsized clasts,but few have recognizably `swollen' or cobble-rich downslope termini.

The deposits of facies B2, apart from their palecolour, are similar to those of facies A1 (see

above), and are attributed to cohesive debris¯owsof mainly high viscosity (Blikra & Nemec, 1998).The predominance of pebble gravel suggests mainderivation from the fan apices and ravine outlets,where the pebbly rockfall `tails' tend to accumu-late and be richly illuviated with ®nes duringrun-off phases.

Facies B3 (rockfall deposits)

This facies constitutes 30±40 vol% of colluviumB. The deposits are lenticular beds of immature,clast-supported and mainly openwork gravel,ranging from pebbly to cobbly, sporadically boul-dery (Fig. 16). The beds are 20±80 cm thick,commonly show normal grading, and are 1á5±5 m wide in outcrop sections transverse to fanradius. Longitudinal sections are sparse andrelatively small, but the individual beds tend tobe thinner and ®ner-grained in the upslopedirection, whereas their downslope termini,where exposed, are relatively thick and coarsecobbly (Fig. 16). In short, the beds are apparentlycharacterized by an internal pattern of grain-sizesegregation analogous to the `head-and-tail' struc-ture of facies A2 beds (see above). Where depos-ited in gullies, the gravel beds of facies B3 areusually ®lled with sand or a sandy, pale-reddishmud (Fig. 16).

The deposits of facies B3 are similar to those offacies A2 (Figs 8 and 9), and their origin is thusattributed to rockfall processes. The ®ne-grainedin®ll is an illuviation product of water¯owthrough the gullies (see discussion of facies B1).

Colluvium C (medium grey)

This third division of the colluvial successionstands out by its darker colour and relativeabundance of sand (Figs 5 and 15). The colouris medium grey (N5) to light±medium grey (N6),locally close to olive±grey (5Y 6/1). The col-luvium consists of sand and immature gravel,and appears to be relatively rich in Chenopodia-ceae (herbaceous) pollen, although the spores aredegraded (S. Peglar, personal communication,1996). A concentrated bulk-pollen sample fromthe middle part of colluvium C has yielded anAMS 14C-isotopic date of 17 � 0á1 ka, whichsuggests an early Late WuÈ rm age. However, thisdate is to be considered with caution, for thesample may have been contaminated with young-er pollen derived by percolating rainwater.

Colluvium C is relatively thin and unevenlydistributed, reaching a thickness of 1á4±1á6 m in

Fig. 12. Correlation diagram of the bed-thickness andmaximum clast-size data from facies A1, with the cor-responding least-squares regression line. Note that theline is offset relative to the point of origin of the dia-gram's vertical axis, which suggests cohesive de-bris¯ows (Nemec & Steel, 1984; Fig. 19). Symbols:n � number of data; r � linear correlation coef®cient;b � regression coef®cient (line gradient). Student's ttest indicated that the correlation and regression aresigni®cant at a risk-of-error level a £ 1%.



some sectors of an apron, but pinching out inothers. The outcrop sections of this colluvium arepoorly accessible, but the following three compo-nent facies can be distinguished.

Facies C1 (sheet¯ow deposits)

This facies constitutes up to 80±90 vol% ofcolluvium C and consists of coarse to very coarsesand, commonly pebbly and rich in granules. Thesand shows planar-parallel strati®cation andforms sheet-like units, 5±35 cm thick, separated

by low-relief scours lined with pebbles, cobblesand sporadic boulders (Fig. 17A,B). The broadscours often cross-cut one another. Isolated sets ofinclined sand strata occur as small scour-and-®llfeatures in the vicinity of some cobbles andboulders.

The characteristics of facies C1 indicate sheet-¯ow processes related to moderate but prolongedand repetitive run-off. The gravel-lined shallowscours apparently represent peak run-off phases,when the uncon®ned water¯ow had a highertransport competence and tended to erode the

Fig. 13. Redeposited volcanic ash incolluvium A at the upper tephraunit level (Fig. 4); facies symbolsare as in the text. (A) Openworkgravel bed of facies A2 with an ash-®lled top, overlain by an ash-bear-ing gravel bed of facies A1; the ashhad been washed into the formerprior to the emplacement of thelatter. (B) Close-up detail of the toppart of bed A2, showing openworkgravel coated and partly ®lled witha calci®ed ash of `cauli¯ower' tex-ture; the lens cap is 5 cm.

Fig. 14. Close-up details of theopenwork gravel of facies A2 in area2 (A) and area 1 (B), showing calci-tic microstalactites on the lowersurfaces of marble clasts, formed byprecipitation from percolating wa-ter.



substratum. Similar units of strati®ed sand sepa-rated by erosive gravel horizons, in a modernPyrenean colluvium, have been referred to byGuillien (1951, 1964) as `binary rhythms' andattributed to the gradual melting of late-lyingsnowpacks. An analogous origin is suggested forfacies C1, particularly on account of the associ-ated facies (see below). The lack of gullying, inspite of abundant run-off, may indicate a frozensubstratum.

Facies C2 (snow¯ow deposits)

These deposits are subordinate and constitute nomore than 5±10 vol% of colluvium C. Theyinclude convex-upward lenses of faintly paral-lel-strati®ed pebbly sand, up to 10±15 cm thickand 2±3 m wide, containing cobbles and boul-ders, often in vertical or other precarious posi-tions. In a single horizon, two or more such lensesare often found close to each other and coalescedwith one another (Fig. 17A,B). Facies C2 also

includes some of the coarse debris that occursscattered between the strati®ed sand units offacies C1, particularly the local cobbles andboulders that have been piled precariously uponone another, often sheltering `pockets' of unsorted®ner gravel (Fig. 17C,D).

The gravelly sand lenses represent small depo-sitional lobes formed ± often close to one another± by ¯owing water, with an accompanying hap-hazard emplacement of large clasts. The origin ofthese lobes is attributed to the melting of debris-rich `digitated' tongues of wet snow¯ows or slush¯ows (Blikra & Nemec, 1998). Snow¯ow ava-lanches are known to carry abundant debris thathas accumulated on the mountain snowpack dueto rockfalls during the winter or been deriveden route by the ¯ow. The scattered large clasts arethought to have melted out from such cohesivesnow¯ows, whose frontal ®ngers were concur-rently turned into pebbly sand accumulations bythe running meltwater. Although some of thelarge clasts may represent rockfall processes (see

Fig. 15. (A) Colluvium B in one of the fans in area 1;palaeotransport direction towards the viewer. Note thesolitary and multiple internal scours (palaeogullies)and the scour-pitted, but essentially conformable,lower boundary. (B) Colluvium B in one of the fans inarea 2; palaeotransport direction obliquely out of thesection, at 50° to the right. Note the disconformable,erosive lower boundary of colluvium B (arrow).



below), the occurrence of scattered and precari-ously placed outsized clasts on a steep sandyslope points to dense snow¯ows (Blikra & Nemec,1998).

Facies C3 (rockfall deposits)

This facies too is subordinate and constitutes nomore than 5±10 vol% of colluvium C. It includesisolated, convex-upward lenses of clast-support-ed gravel, up to 30±45 cm thick and 3±5 m wide(Fig. 17A,B). These lenses show an internal up-ward ®ning from bouldery or cobbly to pebblygravel, and the large clasts often show a `rolling'a(t) fabric. The clast framework is ®lled withsand, strati®ed in larger interstices.

The deposits of this facies resemble those offacies A2 and B3 (see above), and are attributed torockfall avalanches. Their sandy in®ll is due toburial by contemporaneous sheet¯ow. It is likelyalso that much of the coarse debris scatteredbetween and within the sandy units of facies C1(Fig. 17A,B) is of rockfall origin, although isolat-ed rockfall clasts are objectively dif®cult todistinguish from a similar debris derived bysnow¯ows.

Colluvium D (yellow±grey)

This youngest colluvium, yellow±grey (5Y 7/2) incolour, occurs mainly in the upper and axialzones of the colluvial fans. It reaches 3±5 m inthickness in exceptional cases, but is mainlythinner than 1 m and absent in some sectors,where the apron surface is covered with modernsoil and sparse shrubby vegetation (Figs 3A, 5and 15). The limited extent of colluvium D mayre¯ect partly the advanced stage of an apronaggradation and mountain degradation, with thereduced effective head-scarp height rendering theavalanche run-outs shorter.

Colluvium D consists of a multitude of rela-tively small gravel lenses, mainly 10±40 cm thick,1±3 m wide and 4±15 m in downslope extent(Fig. 18). The gravel is immature, predominantlyopenwork and pebbly to ®ne cobbly, but locallyconsists of granules or contains scattered boul-ders. The lenticular beds are commonly stackedupon one another in an `imbricate' fashion, manyshow marked upslope ®ning, and most showeither inverse or normal grading perpendicular tothe boundaries (Fig. 18). The following threecomponent facies have been distinguished andascribed to different depositional processes.

Facies D1 (grain¯ow deposits)

This facies comprises lenticular beds of open-work, granules to pebbly gravel, 10±20 cm thick,which typically show inverse grading (Figs 18, 19

Fig. 16. Example detailed log through colluvium B inarea 2.



and 20B,C). The thinner beds are as a rule also®ner-grained. Bed bases are non-erosive, clearlyadjusted to the local substratum morphology, andthe tops are often slightly convex upwards.Several beds may be stacked directly upon oneanother, but their tops are commonly ®lled and

draped with silt or a silty, very ®ne sand (Figs 19and 20C). Facies D1 is generally more abundantin a fan's upper segment, but its vertical andlateral distribution is uneven. This facies reaches40±60 vol% in some parts of an outcrop section,but is nearly absent in others.

Fig. 17. (A,B) Outcrop sketches ofthe thickest parts of colluvium C inareas 1 and 2, respectively; the pal-aeotransport direction is towardsthe viewer and the facies symbolsare as in the text. (C,D) Close-updetails of colluvium C in area 1,showing large clasts in precariouspositions, sheltering `pockets' of®ner gravel, interpreted as the melt-out deposits of slush¯ows or wetsnow¯ows; the downslope direc-tion is to the left.

Fig. 18. A longitudinal outcrop section of colluvium D in area 2. The palaeotransport direction is to the left, at c. 15°out of the section. Note the lenticular geometry and `imbricate' stacking of many gravel beds.



The deposits of this facies are similar to those offacies A3 (see above) and are attributed to grain-¯ows, probably mainly dry in the present case.The relatively ®ne gravel sizes and the closeassociation with rockfall deposits (Figs 19 and20B,C) suggest that the grain¯ows have eitherevolved directly from the `tails' of rockfall ava-lanches or been derived by resedimentation ofanalogous fan-head deposits (Fig. 21). The siltdrapes are attributed to aeolian transport, whoseeffects are well-visible on the modern fan surfaces,where an openwork gravel, moist or dry, acts as atrap for wind-blown ®nes. Some of the silty sandveneers may be traces of bypassing grain¯ows.

Dry grain¯ows, derived from ravines or causedby fan-head failures, are common on the activefan surfaces. These ¯ows are mobile tongues ofgranule-rich, ®ne-pebble gravel, 1±2 m wide and15±20 cm thick, that spread downslope overdistances of 3±10 m at velocities of 0á5±3 m s)1,depending on the slope angle and roughness.They usually `freeze' on slopes of less than 37°,leaving a veneer of silty sand along their tracks.Similar grain¯ows have been described fromother modern colluvial slopes (HeÂtu et al., 1995;Van Steijn et al., 1995).

Facies D2 (rockfall deposits)

This facies is relatively widespread and consti-tutes up to 30±40 vol% of colluvium D. Itincludes lenticular beds of cobbly to pebbly,openwork gravel, 15±45 cm thick and up to2±3 m wide, which typically show some internalupward ®ning or normal grading (Figs 19 and 20).Their bases are non-erosive and tops are com-monly convex upwards. In outcrop sectionsparallel to the fan radius, most of these bedsshow a bouldery or coarse cobbly `head' passingupslope into a thinner, pebbly `tail' (Fig. 18). Thelatter often has a sandy or silty in®ll, particularlyat the top, and is commonly covered with agranule-rich pebble gravel of facies D1 or D3(Figs 19 and 20).

The deposits of facies D2 resemble those offacies A2, B3 and C3 (see above), and areattributed to rockfall processes. The ®ne gravelthat accumulates in the fan-head zone, due torockfalls (Fig. 21), subsequently tends to be re-mobilized and avalanche further downslope as agrain¯ow or a secondary rockfall. Therefore, a®ner-grained deposit of facies D2 is often founddown-dip of a coarser one (Fig. 18). The sandy orsilty in®ll is attributed to aeolian transport andminor episodic sheetwash.

Facies D3 (debris¯ow deposits)

This facies, although not uncommon, is volu-metrically subordinate, constituting less than10±15 vol% of colluvium D. It includes beds ofmatrix-supported, ®ne-pebble gravel, mainly10±30 cm thick (Figs 19 and 20A,C). Matrixvaries from muddy sand to sandy mud, usuallyyellowish or very slightly rubi®ed. The gravelbeds show little internal grain-size variation,except for the local `¯oating' large pebbles andsporadic cobbles, which make for a crude `coarse-tail' inverse grading. The bed bases are uneven,but non-erosive, and the tops are often slightlyconvex upwards (Fig. 20A,C).

The deposits of facies D3 are similar to those offacies A1 and B2 (see above), and are attributed tocohesive debris¯ows of high viscosity (Blikra &Nemec, 1998). The relatively ®ne gravel sizes andmuddy sand matrix suggest resedimentation offan-head/ravine material, illuviated with ®nesand lubricated by rainwater (Fig. 21).

LATE CENOZOIC REGIONAL CLIMATE

The Late Cenozoic climatic history of Anatolia isrelatively well-studied, based on pollen andlimnological data, but includes many uncertain-ties. The interpretations are often inconsistentand derive from widely different data types,whose resolution varies, although is generallybetter for the younger epochs. Furthermore, thepalaeoclimatic signal deciphered from the con-ventional data types may not necessarily becomparable with that recorded by a colluvialfacies succession, not least because the climaticsensitivity of a sedimentary system may not bethe same as that of either a plant ecosystem or alake hydrological system (Blikra & Nemec, 1998).The following review is thus meant to providelittle more than a tentative palaeoclimatic frame-work against which the local colluvial record willbe further evaluated.

Pliocene

After the well-known Messinian `salinity crisis'and the early Pliocene invasion of Atlantic watersthat re-established the Mediterranean Sea (Cita,1982; Akay et al., 1985), the climate in Anatolia isthought to have returned to a warm±humid mode.Most of the Anatolian lakes were restored at thattime, and many new lakes developed in theregion's karsti®ed landscape. The present study



suggests that the EgÆirdir±Hoyran lake may haveformed near the end of Pliocene.

The Pliocene lacustrine deposits are commonlymarls, but also include lignites and evaporites(Innocenti et al., 1975). The climate was probablyhumid subtropical, possibly seasonal, but ¯uctu-ated over a longer term, showing pronounceddrier phases (ErincË, 1952, 1954; Luttig & Steffens,

1976; Bertolani-Marchetti, 1985). It is likely thatthe onset of the colder climatic conditions inEurope around 5 Ma BP, marked by the earliestAlpine glaciation, made the polar masses of moistair converge with the tropical air masses in thenorthern Mediterranean, causing frontal precipi-tation and warm±humid climatic conditions.Pronounced dry spells could be due to periodicshifting of the tropical front of the Africancontinental air mass further to the north.

Pleistocene

The Early Pleistocene climate in Anatolia isthought to have been similar to the ¯uctuatingsubtropical conditions of the previous epoch,whereas the Late Pleistocene climate was markedlycolder (Bottema & Van Zeist, 1981; Bertolani-Marchetti, 1985) and involved mountain glaciersof WuÈ rm age (ErincË, 1952; Wright, 1961; Birman,1968; Atalay in MTA, 1997). According to Birman(1968), there is no evidence of older Pleistoceneglaciations in Anatolia, although such eventscannot be precluded; their moraine record mayhave been erased by more extensive WuÈ rm glaciers.

Based on palynological evidence, Bottema &Van Zeist (1981) distinguished three climaticphases in the eastern Mediterranean region,broadly correlative with the European glacialchronology: a pleniglacial phase (from at least50 000 until c. 14 000 years BP), a late-glacialphase (until c. 10 000 years BP) and a postglacialphase (until c. 6000 years BP). The pleniglacialclimate was colder than the modern, but ¯uctu-ated considerably, as indicated by the alterna-tions of forest and steppe pollen. The exactmeaning of these changes is not quite clear, butthe former vegetation is generally taken to indi-cate greater moisture and the latter to representdrier climate. Climatic ¯uctuations are shownalso by the adjacent marine basins. The Black Searecord indicates the onset of WuÈ rm glaciationshortly after 80 000 years BP, with the greatestshrinkage and isolation of the basin around18 000 years BP and the return of marine faunac. 9000 years BP (Tchepalyga in MTA, 1997).

The Late Pleistocene climatic ¯uctuations arere¯ected also in lake-level changes, and thus arecommonly referred to as `pluvial' and `interplu-vial' (ErincË, 1952, 1954; Butzer, 1957; Erol, 1964,1969, 1978, 1984), although their correspondencewith the glacials and interglacials of the Alps andnorthern Europe remains to be proven (Roberts,1983; El-Moslimany, 1984). Furthermore, thenature of those `pluvial' episodes is uncertain,

Fig. 19. Example detailed log through colluvium D inarea 2.



as the increased humidity indicated by the pollenand/or lake record may mean either a higherannual precipitation or a greater sur®cial mois-ture due to reduced evaporation (Roberts, 1983).

Bottema & Van Zeist (1981) suggested that thelow content of arboreal pollen and relatively highcontent of Chenopodiaceous pollen in the LatePleistocene record indicated a cold arid climate,

but it was the summer drought, rather than thewinter cold, that kept the forest vegetation incheck. For example, the expansion of coniferousforest around 11 000±10 000 years BP, reported byBottema & Van Zeist (1981) from Lake Karamik(altitude c. 1000 m) and Lake SoÈguÈ t (altitudec. 1400 m) in western Anatolia, would becoeval with the Younger Dryas cooling in Europe.

Fig. 20. Close-up details of colluvium D in area 2 (A,B)and area 1 (C). Note the difference in the facies as-semblages in (A) and (B), illustrating lateral variation ofthe colluvium. The palaeotransport direction is to-wards the viewer, slightly to the left.



El-Moslimany (1984) contended that the LatePleistocene climate could have a higher annualprecipitation than the modern one, but a shortsummer drought of 3±4 months might still renderthe vegetation `aridic'. She suggested that theprecipitation seasonality was less important thanit is today, and that the snowline depression andextensive winter snow could be more crucial thanaridity in preventing forest expansion. Wright(1961) inferred that the WuÈ rm snowline depres-sion in the eastern Taurus Mountains was of theorder of c. 1200 m, which would mean a semi-permanent snow cover extending down to analtitude of c. 2100 m and abundant winter snowat altitudes possibly as low as 1200±1300 m (El-Moslimany, 1984). The lowest altitudes of theWuÈ rm glacier termini recognized in the TaurusMountains are around 1700 m, but most of theinferred moraines are above c. 1900 m (Birman,1968).

Simulation studies of the last-glacial conditionssuggest that the regional climate could be char-acterized by very cold and relatively dry winters,and by summers that were cooler and cloudier,but not necessarily more rainy, than they aretoday (see review by Harrison & Digerfeldt, 1993).The latest Pleistocene varve record from Lake Vanin eastern Anatolia (Landman et al., 1996; Le-mcke et al. and Wick et al. in MTA, 1997)indicates a cold and dry climate for both OlderDryas (until c. 14 000 years BP) and YoungerDryas (c. 11 500 until 9900 years BP), with anintervening phase of somewhat warmer condi-tions but ¯uctuating humidity. The cooler anddrier conditions are re¯ected in a marked de-crease of chemical weathering and a generaldecline of vegetation, with a decrease in trees

and increase in herbaceous plants. The mean airtemperatures are estimated to have fallen byc. 5°C, but the supply of pelitic material to thelake during the colder phases was relatively high.

Roberts & Wright (1993) have recently re-assessed the regional data and concluded thatthe Late Pleistocene climate was undoubtedlycold, and was suf®ciently dry to keep the forestvegetation in check. However, the predominanceof steppe vegetation (rather than tundra or alpineplants) indicates that the deteriorated climate wasnot as cold as the coeval climate in Europe northof the Alps and Carpathians, and also the sum-mers were not as severely dry as they are atpresent. Notably, the `aridic' pollen record isoften coeval with an evidence of lake-levelhighstands, which has been attributed to theclimate coldness, with an estimated decreaseof seasonal temperatures by 3±6 °C, increasedcloudiness, relatively dry summers and wetwinters. The lower air temperatures and greatercloudiness would reduce the evaporation andrender the effects of spring thaw important. Theseclimatic conditions are thought to have culmi-nated during the last-glacial maximum, whenmany Anatolian lakes had a highly positive waterbudget, although the climate was apparently nomore humid than the modern one, as indicated bysteppic pollen. For example, Lake Van's beachterraces corresponding to the last-glacial maxi-mum, dated to 17 470 � 220 years BP, are 70 mabove the lake's present level, whose modernseasonal variations seldom exceed 0á70 m (Land-man et al., 1996).

The Late Pleistocene lakes show calcareous tonon-calcareous mud with horizons of evaporites,peat or paleosols, and with a diatom record of

Fig. 21. Modern rockfall deposits inthe apical zone of a colluvial fan inarea 2. Note the upslope-®ning ofthe gravel tongues of small rockfalls(1), the analogous `tails' left bylarger rockfalls (2), and the smallmud¯ows (3) generated by therainwater mixing with the fan-apex®nes. The upslope distance shownis c. 12 m.



¯uctuating water salinity (Kazancõ et al., Ku-zucuogÆlu et al. and Reed et al. in MTA, 1997).However, the regional pattern of lake-level chan-ges is by no means simple. Several lakes had thehighest stand around 30 000 or 20 000 until18 000 years BP, then fell rapidly around17 000 years BP and stayed low until c. 11 000±10 000 years BP. Lake Van had reportedly fallen by260 m (Lemcke et al. in MTA, 1997) and LakeKonya dried out (Keller, 1974; KuzucuogÆlu et al.in MTA, 1997), which implies extreme aridity.Some lakes have fallen further, stepwise, to themodern level (Briseid, 1994), while others rose toa minor highstand around 6000 years BP and thenfell markedly after 5000 years BP due to theincreased Holocene aridity (Roberts, 1983; Harri-son & Digerfeldt, 1993; Roberts & Wright, 1993). Inshort, the lake-level changes are often non-corre-lative. The water budget of many lakes has beencontrolled by underground drainage, and mayhave thus been affected by the local collapses andtemporal plugging of the karstic cave networks.

Holocene

The Holocene witnessed a rapid transition to themodern Mediterranean climate, accompanied byan expansion of trees into lower-altitude areaspreviously dominated by steppe vegetation. Theonset of this profound climatic change isgenerally dated to c. 9000 years BP, when theforest vegetation spread rapidly (Bottema & VanZeist, 1981; El-Moslimany, 1984). Signi®canthuman activity probably began around that time,with the ®rst signs of oak decline fromc. 7000 years BP.

The data from Lake Van (Landman et al., 1996;Lemcke et al. and Wick et al. in MTA, 1997)indicate that the Holocene climatic optimum,marked by a tree-pollen maximum of 6200±4500 years BP, was characterized by more humidand possibly warmer conditions than the modernclimate. A major decrease in annual precipitationoccurred around 4200 years BP, accentuating theregional climatic deterioration. The climate inAnatolia became increasingly continental andarid, as the annual precipitation decreased andthe seasonality sharpened, with pronouncedsummer drought and limited winter precipitation(ErincË, 1954; Roberts & Wright, 1993). The IronAge then brought about extensive deforestation,with a marked decrease in oak pollen andincrease in sediment yield from c. 3000 years BP

(Landman et al., 1996). A minor increase inprecipitation occurred from c. 900 until 1300 AD

(ErincË, 1954; Van Zeist & Wright, 1963), just priorto the Little Ice Age in Europe.

The increasing aridity of the Holocene climateis re¯ected also in lake levels (Harrison & Dig-erfeldt, 1993; Roberts & Wright, 1993). For exam-ple, the Pleistocene AksËehir±Eber lake, north-eastof the present study area, had a late-glacialshoreline at an altitude of c. 1000 m and an earlyHolocene shoreline at 975 m, but has since fallenby nearly 20 m and shrunk into two extremelyshallow lakes ± one of them a desiccating mire(Atalay, 1977; Briseid, 1994).

Anatolia receives most of its precipitation inthe winter, in connection with the westerlyatmospheric depressions whose paths arecontrolled by the subtropical air¯ow jet. Theselow-pressure cells of humid Atlantic air deriveadditional moisture from the warm waters of theMediterranean Sea, hence the storms are capableof maintaining or regenerating their strength asthey migrate eastwards. In the summer, the belt ofmoist westerly winds shifts northwards, whilethe subtropical high-pressure zone of subsidingair mass brings warm and dry conditions to theeastern Mediterranean. The climate is furthercontrolled by elevation and the distance fromthe coasts, or continentality, which is why most ofcentral Anatolia has a mean January temperaturearound zero (°C). The mean annual precipitationvaries from c. 900 mm at the Mediterranean andBlack Sea coasts, to less than 400 mm in thecentral Anatolia, but is somewhat greater at highaltitudes. Forest is restricted to the mountainsand controlled chie¯y by precipitation; air tem-perature directly controls the plants at altitudesabove 2000 m. The cloudiness, or the proportionof sky covered with clouds, is now relatively low,with an annual mean of 30±35%, which contrib-utes greatly to the high evaporation and summerdrought.

Signi®cance of fersiallitic pedogenesis

Some palaeoclimatic signi®cance can be attachedto the development of fersiallitic red soils, or terrarossa, which typi®ed the Mediterranean regionand its ubiquitous limestones through most of theCenozoic time. The formation of terra rossa isrelated to warm, temperate or subtropical climaticconditions with alternating humid and dry sea-sons (Duchaufour, 1977). The red soil forms bythe decarbonation of hard limestone in theprocess of gradual sur®cial dissolution. At eachwet stage, a ®lm of silicate impurities (mainlyclay and iron oxides) is released from the corroded



rock surface, and this residue tends to rubifyquickly by oxidation. A warm climate withpronounced seasons of high humidity rendersthe process more rapid.

The fersiallitic pedogenesis in the easternMediterranean region generally came to a haltwith the establishment of the modern, semi-aridclimate in the early Holocene time (Duchaufour,1977). The modern climate is too dry, renderingthe decarbonation and rubi®cation extremelyslow or non-existent. The cessation of the terrarossa weathering in the higher mountains mayhave occurred somewhat earlier, in the latestPleistocene, due to the cold and moist conditionsof the last glacial.

The replacement of the last-glacial podzols byHolocene brown soils is related to the decompo-sition of coniferous litter by thermochemicalchanges (Willis in MTA, 1997).

DISCUSSION OF THE COLLUVIALRECORD

Colluvial sedimentation is widely recognized tobe controlled by both climatic conditions (partic-ularly precipitation and air temperatures) andlocal slope conditions (gradient, ruggedness,altitude, bedrock type, exposure to wind, possibletectonic rejuvenation), and it is the slope'sresponse to climate and climatic changes thatdetermines the depositional processes and resultsin stratigraphic variation in sedimentary facies(Blikra & Nemec, 1998). Seismicity may contrib-ute to slope instability, but different depositionalprocesses are generally related to somewhatdifferent slope/weather conditions, even if notnecessarily different climates.

For example, rockfall avalanches, althoughrelated directly to bedrock weathering, are likelyto be triggered by rainfall, thunderstorms, strongwinds, pronounced air temperature variations,frost action and snowpack effects (load stress andmeltwater run-off). Debris¯ow avalanches aregenerally related to a thick weathering cover orother metastable accumulations of debris, andtend to be triggered by heavy rainfalls or intensemeltwater run-off. Grain¯ows are often triggeredby the impact of rockfalls on intra-ravine or fan-head deposits, but may also be caused by thelubricating effects of freeze±thaw cycles, perco-lating water and wind-blown ®nes. The occur-rence of snow¯ow avalanches is obviously relatedto cold climate, particularly the winterconditions. Wet snow¯ows and slush¯ows are

typically associated with late-lying snowpacks orrelatively mild winters, with abundant snowfalland air temperatures oscillating around the freez-ing point.

Few colluvial facies, in isolation, can be con-sidered as climatically diagnostic, since a partic-ular depositional process, such as a debris¯ow ora rockfall, may occur in widely different climaticsettings. Rather, it is the association of speci®csedimentary facies and the differences betweensuccessive facies assemblages that provide pal-aeoclimatic information.

Palaeoclimatic interpretation

In the light of the preceding palaeoclimaticreview and the stratigraphic studies of cavedeposits in western Anatolia (KoÈkten, 1955;Bostanci, 1959; KoÈkten, 1964, 1967; Bostanci,1968), the following broad stages can be distin-guished in the region's post-Messinian climatichistory: (1) the Pliocene to Early Pleistocene stageof warm±humid climate, with pronounced phasesof drier conditions; (2) the Late Pleistocene stageof colder climate, with the alternating `pluvial'and `interpluvial' phases of higher and lowerhumidity; (3) the last-glacial (WuÈ rm) stage ofdistinctly cold climate; and (4) the Holocenestage of warm semi-arid climate. Based on oursedimentological study and the available isotopicdates, these climatic stages are thought to berepresented by the four lithostratigraphic divi-sions of the colluvium (Fig. 4).

Colluvium A contains earliest Pleistocenetephra, and its facies assemblage, dominated bymultiple debris¯ow deposits and multiple, open-work rockfall/grain¯ow deposits (Table 1), sug-gests humid conditions alternating with pro-longed phases of dry conditions. This notion issupported by the common association of faciesA3 with facies A2, and facies A1 with facies A4(Table 1). The intercalated sheetwash depositsare thin lenses indicating frequent but modestrun-off, limited to sur®cial lows. The associationof facies A2 with the `wet' facies A4 and A1(Table 1) suggests that many rockfalls have prob-ably been triggered by rainfall, possibly thun-derstorms. The reddish-brown colour of thecolluvium implies intense fersiallitic weatheringof the mountain range, which strongly supportsthe notion of a warm±humid but ¯uctuatingclimate. The facies succession has a high entropy(Table 1), as might be expected for the highlylocalized colluvial system dominated by a hap-hazard accumulation of slope-waste deposits



characterized by very limited lateral extent (smalllenses).

Colluvium B is light grey in colour, whichsuggests a marked decrease in fersiallitic weath-ering, apparently due to a signi®cant change in

the ground moisture level, possibly in connectionwith climatic cooling. The facies assemblageindicates phases of slope gullying by copiousrun-off, alternating with drier phases, whenmultiple rockfalls, debris¯ows and minor sheet-wash occurred. During the drier phases, thesur®cial run-off outside the gullies was at aminimum, insuf®cient even to illuviate the open-work gravels with slopewash ®nes. The relativefrequency of the different processes was compa-rable, and the depositional system had increasedits entropy to an extremely high level (Table 1).The repetitions of facies B2 or B3 are no morefrequent than their mutual alternations, or inter-calations with facies B1 (Table 1), which suggestsclimatic conditions lacking pronounced, longarid phases; the climate might rather be seasonal.The rockfalls often occurred in `wet' conditionsand were possibly triggered by rainstorms. Like-wise, the cohesive debris¯ows were probablytriggered by occasional heavy rainfall, say inexcess of 10 mm h)1 or so (Blikra & Nemec, 1998).The phenomenon of gully gravure indicatesdistinctly rainy, `pluvial' climatic phases. Thesheetwash in one-third of the occurrences issucceeded by gully erosion (Table 1), whichsuggests that the gullying was due to the wa-ter¯ow power locally exceeding the threshold ofsubstratum resistance.

Colluvium C is darker, medium grey, apparent-ly due to residual traces of humic litter. Thiscolluvium is relatively rich in herbaceous pollen,and a 14C-date for a bulk pollen sample suggestsLate WuÈ rm age. Notably, the region's last-glacialsoils are often grey, despite their being stronglyoxidized by the summer drought. The sedimen-tary facies indicate abundant sheetwash, accom-panied by rockfalls and occasional slush¯ows orwet snow¯ows. The evidence points to the late-glacial stage of most pronounced climatic cooling.

Colluvial slopes steeper than 22°, when subjectto high run-off, are generally prone to rill erosionand gullying (Osterkamp & Toy, 1994; Selby,1994). The characteristics of colluvium C are thusvery meaningful, indicating conditions of pro-longed but modest run-off, which is consistentwith the inferred melting of late-lying snow-packs. The meltwater run-off in such conditionsis seldom suf®cient to instigate rill erosion(Guillien, 1951; Bertran et al., 1995; Blikra &Nemec, 1998), especially if the substratum isfrozen.

The abundance of pebble gravel, or greÁzes, witha modal size class of 1±3 cm, is widely thought to`imply a periglacial environment with frequent

Table 1. The number frequencies (counts) of observedvertical facies transitions and the number frequencypercentages of individual facies in the four colluvialdivisions.

Colluvium A

Facies A1 A2 A3 A4

A1 debris¯ow 33 35 3 12A2 rockfall 35 25 1 7A3 grain¯ow 2 8 4 1A4 sheetwash 5 10 1 0Frequency (%) 46 37 8 9

n = 182; Esystem = 0á953 (73á6%)

Colluvium B

Facies B1(g) B1(s) B2 B3

B1 gullying 0 6 6 8B1 sheetwash 4 0 2 6B2 debris¯ow 10 0 10 8B3 rockfall 8 1 10 10Frequency (%) 22 13 31 34

n � 89; Esystem = 1á063 (96á6%)

Colluvium C

Facies C1 C2 C3

C1 sheetwash 35 8 18C2 snow¯ow 7 0 1C3 rockfall 15 0 3Frequency (%) 70 9 21

n = 87; Esystem = 0á621 (47á8%)

Colluvium D

Facies D1 D2 D3

D1 grain¯ow 26 7 2D2 rockfall 16 28 11D3 debris¯ow 0 14 2Frequency (%) 33 52 15

n = 106; Esystem = 0á770 (97á0%)n is the total number of facies occurrences counted.The data in each case were derived from several pro-®les to account for the lateral variation of colluvium.Note carefully that the data are number frequencies,whereas the estimates of facies in volume frequencypercentages, based on thicknesses, are given in the text.The facies system's entropy, E, has been calculated byHattori's (1976) method, and is here given also as thestandardized percentage of the system's maximumpossible entropy.



freeze±thaw cycles and no permafrost' (Bertranet al., 1995). Therefore, we suggest that the localmountain ridges, although probably too low tohave ever been glaciated, were covered withabundant snow and characterized by periglacialconditions. It should be noted that the adjective`periglacial' is used by some authors to mean coldclimate, with the air temperatures at the groundlevel falling below the freezing point and signi-®cant frost action taking place, whereas othersuse it to mean conditions peripheral to glaciers,irrespective of the presence or absence of frostaction (Flint, 1971, p. 268). We refer to the formermeaning in our suggestion that the mountainridges had snow caps and were subject to frost-weathering.

The scarcity of debris¯ow deposits in col-luvium C indicates that the mountain slopeconditions, with extensive run-off, did not permita thick weathering cover to accumulate in the fancatchment zones. However, the colluviumabounds in sand and ®ne gravel, and had arelatively high sedimentation rate (see nextsection), which suggests that the ravines andslope catchments were continually rechargedwith debris, probably due to the frost-weatheringcombined with slopewash processes. The denselyfractured marble would be very sensitive to frostaction, yielding abundant ®ne debris.

The depositional system's entropy decreasedby half in comparison to the previous stage(Table 1). The high repetitiveness of facies C1(Table 1) may indicate climatic seasonality. Theubiquitous sheetwash facies is interspersed withrelatively frequent rockfall deposits (Table 1),which suggests that the latter may have beenrelated to freeze±thaw cycles, snowpack effects orpossibly rainstorms.

Colluvium D is light yellowish-grey, and itsfacies assemblage is consistent with the deposi-tion processes occurring on the modern, activecolluvial slopes. The predominance of openworkrockfall and grain¯ow gravel indicates verysparse run-off, whose sole effect has apparentlybeen to illuviate fan-head gravel and lubricate itoccasionally into cohesive debris¯ows. The sed-imentary facies, including veneers of wind-blownsilt, are consistent with the Recent climaticconditions. Notably, the warm semi-arid climatehas apparently permitted some very slight rubi®-cation of the ®nest-grained weathering products.

The high frequency and repetitiveness of rock-fall events (Table 1) suggest that the bedrockslopes were strongly weathered and charged withdebris at the preceding climatic stage, because the

modern weathering is extremely slow and limit-ed. This suggestion is supported by the highapparent sedimentation rate of colluvium D (seenext section), and by the fact that the modalgravel sizes of colluvia D and C are comparable, incontrast to the much coarser gravel of the under-lying colluvia B and A.

The marked association of facies D3 and D2(Table 1) indicates that rockfalls were almostinvariably preceded by debris¯ows, which maysuggest a joint triggering by rainstorms. Thunder-storms are in fact very common in the region'smodern climate. Facies D2 is frequently overlainby facies D1 (Table 1), which suggests thatgrain¯ows often evolved directly from the rock-fall `tails' and/or were triggered by the rockfallimpact on fan-head colluvium. The relativelyhigh frequency and repetitiveness of facies D1correspond rather well with the analogous char-acteristics of facies D2 (Table 1): the repetitiverockfalls probably led to a pronounced accumu-lation of their `tail' gravel in the fan-head zone,which then became prone to failures, sheddingseries of grain¯ows. The middle part of colluviumD indicates a high incidence of cohesivedebris¯ows (Fig. 19), which might re¯ect therelative humidity of the Holocene climatic opti-mum, whereas the subsequent predominance ofrockfalls (Fig. 19) might re¯ect the extensivedeforestation dating back to the Iron Age. Despitethese tendencies, the depositional system's en-tropy reached a maximum at this stage (Table 1).

Sedimentation rates

The rate of colluvial sedimentation can only beestimated roughly, because the slope-waste ava-lanche processes are highly episodic, the deposi-tional axis of a colluvial fan tends to shift, and thesedimentary succession's chronostratigraphy inthe present case is poorly constrained. Further-more, the deposition of colluvium does not occurin a `layer-cake' fashion, the volume and inci-dence of different avalanche processes are widelydifferent and variable, and also the role of ¯owingwater varies from depositional to erosional.

The mean sedimentation rates have been esti-mated by using some representative (not neces-sarily absolute) maximum thicknesses and theapproximate time spans of the climatic chrono-zones suggested in the previous section.

Colluvium A reaches 14±17 m in thickness. Itssedimentation is thought to have commenced inthe latest Pliocene (say 1á9 Ma) and spanned mostof the Early Pleistocene time. This would mean a



sedimentation period of c. 1á2 Myr, and an aver-age sedimentation rate of c. 1á2±1á4 cm kyr)1.

Colluvium B is up to 4±5á5 m in thickness andthought to represent most of the Late Pleistocenetime, or its pre-WuÈ rm interval of c. 645 kyr.The mean sedimentation rate would then bec. 0á6±0á8 cm kyr)1, and this low rate is compat-ible with the evidence of gullying and sloperecession tendencies.

Colluvium C is up to 1á4±1á6 m in thickness andthought to represent chie¯y the last-glacial(WuÈ rm) time. Assuming a time period ofc. 65 kyr, the mean sedimentation rate would bec. 2±2á5 cm kyr)1. This relatively high rate corre-sponds rather well with the abundance of sheet-wash deposits and lack of signi®cant scours.

Colluvium D is thought to represent theHolocene time and locally reaches 3±5 m inthickness, which might suggest a sedimentationrate as high as 30±50 cm kyr)1. However, thedeposition of colluvium D has been highly local-ized by topography, and this estimate re¯ects localextrema rather than being a representative meanrate. Where these colluvial deposits are morewidespread on a fan surface, as in the western partof the apron in area 1 (Fig. 2A), their thicknessseldom exceeds 0á60 m, which implies a meansedimentation rate of the order of 6 cm kyr)1. Thiswould still be a remarkably high rate ± three timeshigher than that of colluvium C and an order ofmagnitude higher than that of colluvium B.

The high sedimentation rate probably re¯ectsthe preceding stage of climatic deterioration,when the mountain ridges were charged withabundant greÂzes material due to intense physicalweathering. The ¯owing water might removemost of the sand and gravel from the smallcatchments, but the remaining debris, arrestedby vegetation and rugged relief on higher slopes,would probably require a longer time to betransferred to the ravines and lower slope zone.This latent stock of debris was probably releasedby the early Holocene climatic change, which hada strong impact on vegetation and was followedby overgrazing and anthropogenic deforestation.A similar effect of mountain slopes prechargedwith sediment, resulting in very high sedimenta-tion rates, is described by Blikra & Nemec (1998).

CONCLUSIONS

Colluvial depositional systems involve a range ofspeci®c processes and comprise distinctive, if notunique, sedimentary facies. The present study

shows further that a colluvial facies successionmay bear a remarkably good proxy record of theregional climatic conditions and their changes.The palaeoclimatic interpretation of the EgÆirdircolluvium thus strongly supports the notion thatthe stratigraphic changes in colluvial facies rep-resent signi®cant climatic changes (Blikra &Nemec, 1998).

Colluvial systems are characterized by highlyepisodic sedimentation and may not necessarilyreact to the same atmospheric factors and envi-ronmental changes that are recorded by a plantecosystem or a lacustrine hydrological system.Some climatic thresholds have to be reached, interms of precipitation, run-off and temperatureconditions, before a recognizable change in thedepositional processes can occur. This is shownhere rather well by the stratigraphic changes inthe colluvial facies assemblages, most notably bythe difference in the record of water¯owprocesses in colluvia B and C. The climaticresolution of a colluvial record may thus not bethe same as that of either the palynological or thelimnological record, although these are prone toother types of `random noise' and not alwayssuperior.

Their episodic sedimentation notwithstanding,colluvial fans are `closed-end' systems character-ized by considerable input and negligible output.Unlike alluvial fans, they are not subject tosweeping ¯oods, are seldom catchments tostreams, and their deposits suffer relatively littlecontemporaneous reworking. It is thus not sur-prising that these speci®c systems are capable ofrecording some highly legible signatures of cli-matic changes.

It is further worth noting that none of the fourlithostratigraphic units of the Anatoliancolluvium, especially its Holocene facies assem-blage, are comparable to the postglacial Scandi-navian colluvium described by Blikra & Nemec(1998). This striking difference indicates thatcolluvial depositional systems are sensitive re-corders of not only regional climatic changes butalso inter-regional geoclimatic differences.

Few coeval colluvial successions have beenstudied in the north-eastern Mediterranean, andthe regional signi®cance of the western Anatolianrecord obviously needs to be veri®ed by broaderresearch (a comparative study in the Peloponni-sos region of Greece is now under way). Ourinterpretation of the EgÆirdir colluvium gains somesupport from a recent study of the Quaternarypiedmont deposits in southern Crete (Nemec &Postma, 1993, 1995), where the Early Pleistocene



coastal climate promoted intense ferrosialliticweathering and generated abundant debris¯ows.The Late Pleistocene climate there was relativelydry, periglacial, but with several phases of pow-erful water¯ow issuing from the intramontanevalleys, apparently due to melting of high-alti-tude glaciers. (By `periglacial', Nemec & Postmameant conditions peripheral to an alpine ice-cap,not necessarily frost action.) Crete's Holoceneclimate has been warm and arid, with little or noferrosiallitic weathering. The mountain peaks,more than 2450 m high, still host semi-permanentsnowpacks, although Crete has long become partof the so-called `European Sahara'.

The present study concurs with Blikra &Nemec's (1998) conclusion that the colluvialdepositional systems, with their unique faciesassemblages and valuable proxy record of climat-ic changes, are a fascinating frontier of clasticsedimentology.

ACKNOWLEDGEMENTS

The study was sponsored by NATO grant CRP-910052 and Bergen University, with further sup-port from Ankara University and TUBITAK. Wethank Levent Karadenizlõ, Cafer Seri® and OÈ zden_Ileri (Ankara) for help in sediment sampling, andSylvia Peglar (Bergen) for examining pollen sam-ples. The isotopic dating was performed at theuniversity laboratories in Trondheim and New-castle-upon-Tyne. The manuscript was criticallyreviewed by Lars Blikra, Brian Bornhold, BrianJones, Francesco Massari and R.W. Young. Thestudy represents activities of the NorwegianResearch Group for Quaternary Sedimentology(NFKS).

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Manuscript received 18 September 1997; revision ac-cepted March 1998



Quaternary colluvium in west-central Anatolia: sedimentary facies and palaeoclimatic signifcance

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