Oligocene–Miocene basin evolution in SE Anatolia, Turkey

26 Pages·2008·3.24 MB·English

1 Oligocene–Miocene basin evolution in SE Anatolia,
2
Turkey: constraints on the closure of the eastern Tethys gateway
3
4
5 SILJAK.HU¨SING1*,WILLEM-JANZACHARIASSE2,DOUWEJ.J.VANHINSBERGEN1,
6 WOUTKRIJGSMAN1,MURATINCEO¨Z3,MATHIASHARZHAUSER4,
7
8 OLEGMANDIC4&ANDREASKROH4
9 1PaleomagneticLaboratory“FortHoofddijk”,DepartmentofEarthSciences,Utrecht
10
University,Budapestlaan4,3584CDUtrecht,TheNetherlands
11
12 2StratigraphyandPaleontologyGroup,DepartmentofEarthSciences,UtrechtUniversity,
13
TheNetherlands
14
15 3DepartmentofGeology,FıratUniversity,Elazıg˘,Turkey
16
17 4NaturalHistoryMuseumVienna,Austria
18
*Correspondingauthor(e-mail:[email protected])
19
20
21
Abstract: TheOligocene–Miocenewasatimecharacterizedbymajorclimatechangesaswellas
22 changingplateconfigurations.TheMiddleMioceneClimateTransition(17to11Ma)mayeven
23 have been triggered by a plate tectonic event: the closure of the eastern Tethys gateway, the
24 marineconnectionbetweentheMediterraneanandIndianOcean.Toaddressthisidea,wefocus
25 ontheevolutionofOligoceneandMioceneforelandbasinsinthesouthernmostpartofTurkey,
26 themostlikelycandidatestohaveformedthisgateway.Inaddition,wetakethegeodynamicevol-
27 utionoftheArabian–Eurasiancollisionintoaccount.
TheMus¸andElazıg˘ basins,locatedtothenorthoftheBitlis–Zagrossuturezone,weremost
28
likely connected during the Oligocene. The deepening of both basins is biostratigraphically
29
datedbyustooccurduringtheRupelian(EarlyOligocene).Deepmarineconditions(between
30
350and750m)prevaileduntiltheChattian(LateOligocene),whenthebasinsshoaledrapidly
31 tosubtidal/intertidalenvironmentintropicaltosubtropicalconditions,asindicatedbythemacro-
32 fossilassemblages.WeconcludethattheemergenceofthisbasinduringtheChattianseverely
33 restrictedthemarineconnectionbetweenaneastern(IndianOcean)andwestern(Mediterranean)
34 marinedomain.IfaconnectionpersisteditwaslikelylocatedsouthoftheBitlis–Zagrossuture
35 zone. The Kahramanmaras¸ basin, located on the northern Arabian promontory south of the
36 Bitlis–Zagrossuturezone,wasaforelandbasinduringtheMiddleandLateMiocene,possibly
linkedtotheHataybasintothewestandtheLicebasintotheeast.Ourdataindicatesthatthisfore-
37
landbasinexperiencedshallowmarineconditionsduringtheLanghian,followedbyarapiddee-
38
peningduringLanghian/Serravallianandprevailingdeepmarineconditions(between350and
39
750m)untiltheearlyTortonian.Wehavedatedtheyoungestsedimentsunderneathasubduc-
40 tion-relatedthrustatc.11Maandsuggestthatthiscorrespondstotheendofunderthrustingin
41 theKahramanmaras¸region,i.e.theendofsubductionofArabia.Thisagecoincidesintimewith
42 the onset of eastern Anatolian volcanism, uplift of the East Anatolian Accretionary Complex,
43 andtheonsetoftheNorthandEastAnatolianFaultZonesaccommodatingwestwardescapetec-
44 tonicsofAnatolia.Afterc.11Ma,theforelandbasinsouthoftheBitlisformednot(ornolonger)a
45 deepmarineconnectionalongthenorthernmarginofArabiabetweentheMediterraneanSeaand
the IndianOcean.We finallyconcludethat a causal link betweengatewayclosureand global
46
climatechangetoacoolermode,recordedintheMi3bevent(d18Oincrease)datedat13.82Ma,
47
cannotbesupported.
48
49
50
51
Tectonicclosureandopeningofmarinegatewaysis et al. 2005; Schneider & Schmittner 2006). The
52
suggestedtohaveledtosubstantialreorganization opening of the Drake Passage allowed the start of
53
ofsurfaceanddeepoceanwatercurrentsandmay the Antarctic Circumpolar Current which might
54
have caused important changes in global climate. have initiated the abrupt climate cooling around
55
The closure of the Panama Isthmus between 3.0 theEocene/Oligoceneboundaryandtheextensive
56
and2.5MahasinfluencedtheGulfStream,trigger- growth of Antarctic ice sheets (Livermore et al.
57
ingmajorNorthernHemisphereglaciations(Bartoli 2005). The restriction of water exchange across
58
From:VANHINSBERGEN,D.J.J.,EDWARDS,M.A.&GOVERS,R.(eds)CollisionandCollapseatthe
Africa–Arabia–EurasiaSubductionZone.TheGeologicalSociety,London,SpecialPublications,311,107–132.
DOI:10.1144/SP311.4 0305-8719/09/$15.00#TheGeologicalSocietyofLondon2009.
108 S.K.HU¨SINGETAL.
59 the former straits between Spain and Morocco Gulf(Hessamietal.2001).Therefore,wedecided
60 resulted in the desiccation of the Mediterranean to study the southernmost flysch deposits in
61 SeaduringitsMessinianSalinityCrisis(Hsu¨ etal. eastern Anatolia (Fig. 1), these being the most
62 1973). Likewise, the disconnection of the Indian likely candidates to represent the youngest sedi-
63 Ocean and the Atlantic/Mediterranean water ments deposited just prior to the disconnection of
64 masseshasbeensuggestedtohavecausedamajor theIndian–Arabiangateway.
65 middleMioceneclimatechange,widelyrecognized
66 inboththemarine(Woodruff&Savin1989;Flower
67 & Kennett 1994; Zachos et al. 2001; Bicchi et al. Geodynamicandgeologicalcontext
68 2003) and the terrestrial record (Krijgsman et al.
69 1994).Itisthisdisconnectionthatformsthescope The continental collision of the African–Arabian
70 ofthispaper. platewiththe Eurasianplate resultedina tectonic
71 ThemiddleMioceneisaperiodcharacterizedby collageineasternAnatoliathatisgenerallysubdi-
72 major environmental changes during which the vided into: (1) the eastern Rhodope–Pontide Arc
73 Earth’s climate gradually progressed into a colder in the north; (2) the East Anatolian Accretionary
74 mode (Zachos et al. 2001). The Miocene Climate Complexconsistingofanophioliticme´langeover-
75 Optimum between 17 to 15Ma was followed by lain by Paleocene to upper Oligocene sediments;
76 an interval of global climate variability between and(3)theBitlis–Po¨tu¨rgeMassiftectonicallyover-
77 15and14Ma,markedbyatmosphericandoceanic lying the northern part of the Arabian margin
78 cooling, East Antarctic Ice Sheet growth, and (Fig. 1) (S¸engo¨r & Yılmaz 1981; Yılmaz 1993;
79 carbon cycle variability (Woodruff & Savin 1989; Tu¨ysu¨z & Erler 1995; Robertson 2000; S¸engo¨r
80 Flower & Kennett 1994; Zachos et al. 2001). et al. 2003; Agard et al. 2005). As north–south
81 Seven major d18O shifts, Mi1 to Mi7, to higher shorteningcontinuedbetweentheconvergingEura-
82 (¼ colder) values documented in marine records sianandArabianplate,therelativelysoftandirre-
83 of the Atlantic reflect brief periods of increased sistant East Anatolian Accretionary Complex took
84 glaciations(Milleretal.1991;Wrightetal.1992; up most of the initial post-collisional convergent
85 Miller et al. 2005). The Mi3a, Mi3b and Mi4 strain by shortening and thickening (Yılmaz et al.
86 events between about 14.5 and 12.5Ma represent 1998).Around13–11Ma,easternAnatoliaunder-
87 the middle Miocene d18O increase, leading the wentrapidupliftandwasconfrontedwithonsetof
88 globalclimateintoacoldermodeatthesametime widespread volcanism (Dewey et al. 1986; Pearce
89 as the onset of the Antarctic glaciations (van der et al. 1990; Keskin 2003; S¸engo¨r et al. 2003),
90 Zwaan & Gudjonsson 1986; Abels et al. 2005; which has been associated with detachment of
91 Milleretal.2005). northward dipping subducted lithosphere (Keskin
92 A direct relationship between the Middle 2003; Faccenna et al. 2006; Hafkenscheid et al.
93 Miocene Climate change, whether recorded in 2006). From this moment onward, the ongoing
94 oxygen or carbon isotopes, marine or terrestrial northwardmotionofArabia(stillcontinuingtoday)
95 fauna, and the closure of the eastern Tethys (McClusky et al. 2000; Reilinger et al. 2006;
96 gateway has so far never been proven, although Allmendinger et al. 2007), and the retreat of the
97 many studies suggest a causal link between the Hellenicsubductionzonetothewest(Berckhemer
98 two events (e.g. Woodruff & Savin 1989; Ro¨gl 1977; Le Pichon et al. 1982; Jolivet 2001) led to
99 1999; Flower & Kennett 1993). Part of the westward tectonic escape of Anatolia along the
100 problem is that the sediments that were deposited NorthandEastAnatolianFaults(Dewey&S¸engo¨r
101 in the eastern Tethys gateway have on many 1979;S¸engo¨retal.1985).
102 occasions not been recognized or properly dated. The present-day plate boundary of the African
103 Inaddition,thechronologicalsequenceoftectonic and Eurasian plates is determined by the Bitlis–
104 processes involved in the convergence of the Zagrossuturezone(Robertson2000andreferences
105 Eurasia and African–Arabian plates is complex therein;Westaway2003).OntheArabianplate,to
106 and actively debated (see Garfunkel 1998, 2004; the south of the suture zone, Eocene and younger
107 Golonka 2004). To assess the timing of gateway (volcano-)sedimentsarerelativelyflatlying.North
108 closure along the northern Arabian promontory, of the Bitlis–Po¨tu¨rge zone, Tertiary marine sedi-
109 the major geodynamic processes of the Arabia– mentscropoutrarelyandthegeologyisdominated
110 Eurasiacollisionandtheirtectonicresponseshave by pre-Neogene basement rocks (metamorphic
111 tobetakenintoaccount.According toreconstruc- rocks) and Neogene volcanic rocks. The Bitlis–
112 tions of Jolivet & Faccenna (2000) and Bellahsen Po¨tu¨rgeMassifitselfischaracterizedbyastackof
113 et al. (2003), Arabia collided first in the eastern nappes originated on the Eurasian side of the
114 Anatolian/western Iranian region around 30Ma Neotethys(Robertson2000;Robertsonetal.2004).
115 ago. Consequently, it gradually rotated counter- TheBitlis–Po¨tu¨rgeMassifrunsfromsoutheast-
116 clockwiseleadingtodiachronouscollisioneastward ernTurkeytotheeasternMediterraneanbasininto
from Southeastern Anatolia towards the Persian the Cyprus arc, where it meets the East Anatolian
OLIGO–MIOCENESETURKISHTETHYSFORELAND 109
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143 Fig.1. OutlineoftectonicmapoftheMiddleEastregion,showingmajorstructuressuchastheBitlis–Zagros
144 Suturezone,theNorthandEastAnatolianFaultZones(NAFZandEAFZ),andmountainrangesrelatedtothe
145 convergenceofAfrica–ArabiaandEurasia(drawnafterGeologicalmapofTurkey(S¸enel2002)).
146
147
148 Fault (EAF). Here the structure becomes more suggested that this subduction led to southward
149 complex with several sub-parallel southwestwards migratingaccretionofnappesandoverlyingdeep-
150 running faults and thrusts. The East Anatolian marine foreland basin deposits, even though indi-
151 Fault is a 2–3km wide, active left-lateral strike- vidual basins that may reflect such evolution have
152 slip fault extending from Antakya in the west to notbeenidentifiedinthegeologicalrecord,which
153 Karliova in the NE, where it meets the eastern is, at least in part, due to the young volcanic
154 termination of the North Anatolian Fault (NAF) sequencescoveringalargepartofeasternTurkey.
155 (Figs1&2;EAFZandNAFZ).TheNAFisaright- If southward accretion of nappes indeed occurred,
156 lateral strike-slip fault extending over a length of oneshouldbeabletoidentifysouthwardyounging
157 about 1300km westward. The relative Africa– flysch deposits. A foredeep likely remains present
158 Arabia motion is taken up by strike-slip displace- untilcontinent–continentcollisionandsubsequent
159 mentalongtheDeadSeaFault(Jolivet&Faccenna slab break-off stalls convergence and the collision
160 2000), while the Africa–Anatolia motion is taken zone is uplifted. Even though small marine basins
161 upbysubductionsouthofCyprus.Theoverallcon- mayremain,thelongdistancebetweenthePersian
162 vergencebetweenArabiaandAnatoliaistakenup Gulf and the Mediterranean Sea makes foredeeps
163 along the North and East Anatolian fault zones the most promising basins to have formed the
164 (NAFZ and EAFZ) (Fig. 2) (e.g. McClusky et al. gatewaybetweenthesewatermasses.Inthefollow-
165 2000;S¸engo¨retal.2005).Thereisgeneralconsen- ingparagraphswewillpresentanddiscusstheevol-
166 sus that the NAFZ and EAFZ had the majority of utionofforedeepbasinsinSETurkeyinthelightof
167 their displacement in Plio-Pleistocene times theclosureoftheeasternTethysgateway.
168 (Barka1992;Westaway2003,2004;Hubert-Ferrari
169 et al. 2008) although incipient motion may have
170 been as early as late Serravallian/early Tortonian Basinevolution
171 (c.12to11Ma)(Deweyetal.1986;Hubert-Ferrari
172 Q1 etal.2002;Bozkurt2003;S¸engo¨retal.2005). The Arabian foreland is separated from the East
173 The region that comprises the eastern Tethys Anatolian Accretionary Complex (EAAC) by the
174 gateway has thus been subjected to plate conver- Bitlis–Po¨tu¨rge Massif (Fig. 1). The area of this
gence and subduction. S¸engo¨r et al. (2003) massifcorrespondstothecompressionzonelocated
110 S.K.HU¨SINGETAL.
175
176
177 of
178 Mus¸map
179
118801 areas:ogical
182 diedGeol
118834 hestuafter
185 gtwn
186 atindra
118878 sindicZone(
111899901 eeboxeSuture
192 ethrgros
193 thZa
119945 s.NoteBitlis–
196 urehe
197 uctoft
112229900089012 ortectonicstrnmaras¸south
203 majma
a
220045 withKahr
220067 Turkeyneand
222200118901 outheasternosSuturezo
212 Sgr
na
222111345 natoliaiBitlis–Z
A
216 Ehe
222111789 mapofSnorthoft
220 caloth
221 gib
222223 cgeolo˘Elazıg,
222222456 schematipartand2)).
222222222333789012 Fig.2.OutlineofintheeasternmostTurkey(S¸enel200
OLIGO–MIOCENESETURKISHTETHYSFORELAND 111
233 between the two continental crusts, Eurasia and Mioceneandyoungercontinentalclasticsandvol-
234 African–Arabian.Themassifwasstackedto form canics (S¸arog˘lu & Yılmaz 1986; Sancay et al.
235 a nappe complex during the closure of the Neo- 2006). Detailed biostratigraphy was carried out
236 Tethys by the middle Miocene (Dewey 1986 and mainlybasedondinoflagellatesandpalynomorphs
237 referencesherein). yieldingaRupelian(earlyOligocene)toAquitanian
238 Wehavestudiedthesouthernmostflyschdepos- (early Miocene) age (Sancay et al. 2006). The
239 itsintheeasternAnatolianorogenicsystem.These occurrence of the benthic foraminiferal family of
240 arefoundintheMus¸andElazıg˘basins,bothnorthof Miogypsinidaewasinterpretedaspossibleindicator
241 theBitlis–Po¨tu¨rgeMassif,andtheKahramanmaras¸ for a connection with the Indo-Pacific during the
242 basinlocatedsouthoftheBitlis–Po¨tu¨rgeMassifand Oligocene(Sancayetal.2006).
243 nearthetriplejunctionoftheArabian,Eurasianand We sampled two sections in the Mus¸ basin
244 Anatolianplates(Fig.2). (Fig. 3). The eastern transect comprises allegedly
245 Eocene–Oligocene clastics in the northern part of
246 GeologicalsettingoftheMus¸ basin thebasin,andOligoceneflyschsedimentsfollowed
247 bymarinelimestoneswhicharecoveredbyvolca-
248 The Mus¸ basin is an elongated structure located nics.Thesecondtransectinthewesternpartofthe
249 north of the Bitlis–Po¨tu¨rge Massif and east of the basincoversthetransitionfrommarlstolimestones,
250 North and East Anatolian Fault (Figs 2 & 3). assumingitisequivalenttotheuppermostpartofthe
251 According to previous studies (S¸arog˘lu & Yılmaz eastern succession. The entire succession gently
252 1986;Sancayetal.2006)thebasincontainsupper dipstowardstheNW.
253 EocenetolowerMiocenelimestones,marlsandtur- Thebaseoftheeasternsection(easttransectin
254 biditic sandstones with marine sedimentation con- Fig. 3) is determined by a thrust zone emplacing
255 tinuous from the Oligocene to Aquitanian. These allegedly Eocene clastic sediments onto Pliocene
256 deposits overlay an upper Cretaceous ophiolitic deposits (see geological map of Turkey, S¸enel
257 me´lange. S¸arog˘lu & Yılmaz (1986) suggested that 2002) (Fig. 3). The first 20m of the studied
258 lower Miocene limestones are widespread in the section is characterized by an alternation of con-
259 northern part of the Mus¸ area, while middle glomerates,clays,sands,andsilts(Fig.4).Alayer
260 Miocene strata were not found. These sequences of limestone (1.5m) with shell fragments and the
261 are unconformably covered by allegedly upper presenceoflargegastropodsclearlyindicateshallow
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
Fig.3. SimplifiedtectonicandgeologicalmapoftheMus¸areaincludingthetrajectoriesofthetwostudiedsections:
288 anabout1.4kmlongtransectintheeasternpartofthebasinandadditionallyanabout500mlongtransectinthe
289 westernpartofthebasinequivalenttotheuppermostpartofthewesterntransect.RefertoLegendforkeytolithology
290 and/orageofoutcrops(drawnafterGeologicalmapofTurkey(S¸enel2002)).
112 S.K.HU¨SINGETAL.
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
Fig.4. LithologicalcolumnofthestudiedsectionsintheMus¸basinwiththebiostratigraphicresults.Theagemodel
346
isbasedonplanktonicforaminiferoccurrencesandthemacrofossilassemblageintheuppermost40m(mainly
347
limestonesandsands)ofthestratigraphy.Planktonicforaminiferoccurrenceshavebeencorrelatedtoplanktonic
348 foraminiferzones,which,inturn,aretiedtostagesduringtheOligoceneleadingtoacorrelationtotheGeologicalTime
Scale.Seelegendforkeytolithologies,structuresandfossils.
OLIGO–MIOCENESETURKISHTETHYSFORELAND 113
349 marineconditions.This sequenceisfollowedbya which together with the highest occurrence of
350 thick(about1.3km)successionofalternatingclay Paragloborotalia opima opima (at 1045m
351 and sandstone. Occasionally conglomeratic layers, (TR222)) indicates that the middle part of the
352 characterized by angular, unsorted material, occur Mus¸ section correlates to planktonic foraminiferal
353 inthesuccession.Theselayershavethicknessesof biozone P21 of Blow (1969) and Berger & Miller
354 upto10mandareinterpretedasdebrisflows.The (1988) which is latest Rupelian to early Chattian
355 sandstone layers show typical transport character- in age (Berggren et al. 1995). The absence of
356 istics such as fining upwards, Bouma sequence, Paragloborotalia opima opima from sample level
357 flutecastsandfossilfragmentsindicatingaturbidi- 1045m (TR 222) upward in the eastern transect
358 tic origin. These turbidites occur as massive sand- and the occurrence of typical Paragloborotalia
359 stone layers of thicknesses of up to 15m or as pseudokugleri and even of forms transitional
360 severalthinner(upto50cm)turbiditelayers,prob- between Paragloborotalia pseudokugleri and
361 ably representing individual events. Only minor Paragloborotalia kugleri at the top of the section
362 slumping, indicating an unstable submarine paleo- (1360m (TR 232)) indicate that the upper part
363 slope,andfoldingoccurthroughoutthesuccession. extends upwards into the lower part of planktonic
364 Theupperpartofthesectionshowsshoalingcharac- foraminiferal biozone P22 of Berger & Miller
365 terized by shallow marine limestone, containing (1988)beingChattianinage(Berggrenetal.1995).
366 echinoderms, bivalves and gastropods, followed ThisisconfirmedbythepresenceofParagloborota-
367 bycontinentalclastics. liasiakensisandGlobigerinoidesprimordiusinthe
368 Thewesterntransect(westtransectinFig.3)is youngest samples. Both species make their first
369 dominatedbybluishclaywithoccasionalredsedi- appearanceinthelowerpartofbiozoneP22together
370 ments. This is followed by a thick, about 100m, with Paragloborotalia pseudokugleri (Berger &
371 sequenceofalternatingsofterbluishsands,brown- Miller1988;Spezzaferri1994).
372 ish sands and indurate bluish sands, probably all In the western section, the co-occurrence of
373 of marine origin. These sediments are overlain by Globigerina angulisuturalis and Paragloborotalia
374 coral limestones, which, in turn, are covered by opima opima at 2m and 195m (TR 202 and
375 volcanicrocks,probablyofMioceneage.Thissuc- TR 210) indicates that the lower 200m correlates
376 cession also clearly indicates shoaling towards to the interval between 900 and 1100m in the
377 thetop. eastern section. Both these intervals belong to
378 biozoneP21.Thisintervalisfollowedbysediments
379 BiostratigraphicresultsoftheMus¸ basin thatarebarreninplanktonicforaminifersbutrela-
380 tivelyrichinshallowwaterbenthicforaminifers.
381 Forbiostratigraphy,sampleswerecollectedatabout The macrofossil assemblage of the uppermost
382 every20mfromboththewesternandeasterntrans- 40mintheeasterntransectcomprisesbivalves,gas-
383 ect(Fig.3).Noteverysampleprovedtobeusefulfor tropodsandechinoids.Theassemblageisdiminished
384 biostratigraphyorpaleobathymetry.Thenumberof by complete aragonite leaching. Nevertheless, the
385 foraminifers is extremely variable and most likely faunaisageindicative andallowspalaeoecological
386 fluctuate in pace with changes in terrigenous interpretations.Themolluscfaunacomprisestypical
387 clastic input. Preservation is generally poor with OligocenetaxasuchasthegastropodAmpullinopsis
388 specimensmostlyrecrystallizedandfrequentlydis- crassatina(Lamarck1804)andthebivalvesAmussio-Q2
389 torted.Samplesfromtheupper300mofthewestern pecten labadyei (d’Archiac & Haime 1853) andQ3
390 sectionarebarreninplanktonicforaminifers. Ringicardium buekkianum (Telegdi-Roth 1914).Q4
391 The low diversity in planktonic foraminiferal Some species such as Dilatilabrum sublatissimus
392 faunainbothsectionsisdominatedbygloboquadri- (d’Orbigny1852),Strombuscf.praecedensSchafferQ5;Q6
393 nids and catapsydracids with occasional occur- 1912, Cordiopsis incrassatus (Nyst 1836),Q7
394 rencesofGlobigerinaciperoensisandGlobigerina Amussiopecten subpleuronectes (d’Orbigny 1852),
395 angulisuturalis and clearly points to an Oligocene and Hyotissa hyotis (Linnæus 1758) appear duringQ8
396 age for the eastern and lower western section theChattianandpersistintotheMiocene.
397 (Fig. 4) (Berger & Miller 1988; Spezzaferri & An important biostratigraphic feature is the
398 PremoliSilva1991). co-occurrenceofthepectinidsAmussiopectenlaba-
399 Thebasalpartoftheeasternsectioncorrelatesto dyeiandA.subpleuronectesandtheoccurrenceof
400 planktonic foraminiferal biozone P19 of Berger & transitional morphs. This evolutionary phase is
401 Miller (1988) on the basis of trace occurrences of recorded so far only from the upper Chattian
402 specimensidenticaltoTurborotaliaampliapertura. (Mandic 2000). Especially in the Iranian Qom
403 This biozone is Rupelian (early Oligocene) in age Basin,thisassemblageco-occurswiththelargerfor-
404 (Fig. 4) (Berggren et al. 1995). The lowermost aminifera Eulepidinadilatata. The last occurrence
405 occurrence of Globigerina angulisuturalis is ofAmussiopectenlabadyeiprecedesthefirstoccur-
406 recorded at 950m (TR 221) in the eastern section rence of Miogypsinoides which roughly coincides
114 S.K.HU¨SINGETAL.
407 with the base of the early Miocene. The entire Palaeoenvironmentalinterpretations
408 mollusc assemblage is therefore pointing to a late fortheMus¸ basin
409 Chattian age. This dating is supported by the
410 echinoid fauna. Parascutella subrotundaeformis Benthic foraminifers in the sections were further-
411 Q9 (Schauroth1865),asanddollarwhichoccursmost more used to estimate the depositional depth. The
412 commonly in Northern Italy, is restricted to the commonly used method of calculating depth by
413 ChattianandAquitanian. determining the ratio between planktonic and
414 Comparableassemblagesaredescribedfromthe benthic foraminifers (van der Zwaan et al. 1990;
415 upper Chattian of the central Iranian Qom For- van Hinsbergen et al. 2005b) is not reliable here
416 mation (Mandic 2000; Harzhauser 2004; Reuter duetosignificantdownslopetransport(seeninpre-
417 et al. 2007) and along the entire northern coast of sence of notorious epifytes and shallow water
418 the Western Tethys (Harzhauser et al. 2002). A benthic foraminifers such as Pararotalia and
419 relation to the Central Paratethys is indicated by Amphistegina) and poor preservation. Instead, we
420 the occurrence of Ringicardium buekkianum, focus on the deepest water benthic foraminiferal
421 which is known from the Lower Egerian (Upper depth markers (for list see van Hinsbergen et al.
422 Chattian) deposits of Hungary (Ba´ldi 1973). The 2005b) and the macrofossils. In the eastern
423 faunistic relations towards the east are low. Only section, the depositional environment of the lower
424 Dilatilabrum sublatissimus (d’Orbigny 1852) 20mischaracterizedbyshallowmarineconditions,
425 reaches to the Zagros Basin and the Arabian shelf indicated by shell fragments in the limestone.
426 during the Aquitanian (Harzhauser et al. 2007). However, a rapid deepening trend occurs at about
427 The echinoderm Clypeaster waageni (Duncan & 50mindicatedbythepresenceofbenthicforamini-
428 Q10Sladen 1883), in contrast, represents ties with the feral depth markers (typically Cibicides (pseudo)
429 echinoidfaunaoftheLowerIndusBasin. ungerianus, Gyroidina spp. Uvigerina spp. and
430 Numericalagesforthebasinfillareprovidedby occasionally Oridorsalis spp.), and the absence of
431 threeplanktonicforaminiferalbioevents.However, markersfordeeperwater,whichpointsatadeposi-
432 equating highest and lowest occurrences (ho and tionaldepthrangeof350to750m(theupperlimitis
433 lo)withtheLastOccurrence(LO)andFirstOccur- constraint by the occurrence of Oridorsalis spp.
434 rence(FO)ofthesesspeciesshouldbeacceptedwith after van Hinsbergen et al. 2005b). Towards the
435 reservation because the positions are poorly deli- topoftheeasternsectionrapidshoalingisevident
436 neated due to large sampling distances in combi- from the presence of macrofossils. Both the mol-
437 nation with scarcity and poor preservation of the luscsandechinodermsoftheuppermost40mindi-
438 agediagnosticspecies. cate a shallow marine, tropical to subtropical,
439 The oldest bioevent in the Mus¸ section is the depositional environment with sand bottoms and
440 lowest occurrence of Turborotalia ampliapertura algal or sea grass patches. Giant conchs such as
441 some 300m above the base of the eastern section Dilatilabrum sublatissimus (d’Orbigny 1852) are
442 (TR 190). The LO of this species is calibrated at found today in sea grass meadows and sheltered
443 30.3Ma (Berggren et al. 1995) providing a lagoons, where they live partly buried in the soft
444 minimumageforthebaseoftheMus¸section.The substrate (Bandel & Wedler 1987). Similarly, the
445 age for the top of the eastern section should be extantrepresentativesoftheoysterHyotissahyotis
446 slightlyyoungerthantheageof25.9MafortheFO prefer shallow subtidal habitats where they are
447 ofParagloborotaliapseudokugleri(Berggrenetal. attached to rocks and corals (Slack-Smith 1998).
448 1995)becauseofthepresenceofparagloborotalids Extant Echinolampas and Clypeaster, too, occur
449 being transitional between Paragloborotalia pseu- mostcommonlyonsandysedimentswithseagrass
450 dokugleriandParagloborotaliakugleri.Thehoof patches(Hendleretal.1995).
451 Paragloborotaliaopimaopimaat1045m(TR222) In the western section a shoaling trend in the
452 in the eastern section provides an extra age cali- upper 250m is observed by the relatively rich
453 brationpointof27.456Mabeingthecalibratedage occurrence of shallow water benthic foraminifers
454 for the LO of Paragloborotalia opima opima at and occasional red sediments. The differences
455 ODP Site 1218 (Wade et al. 2007). The dating of between west and east suggest that the western
456 thetopofthesectionisinaccordancewiththemacro- part of the Mus¸ basin shoaled more rapidly or
457 faunawhichstronglyindicatesalateChattianagefor earlierduringtheChattianthantheeasternpart.
458 theupper40mtheeasterntransect.
459 Nonumericalagesareprovidedforthewestern ImplicationsfortheMus¸ basin
460 section. However, based on the co-occurrence of
461 Globigerina angulisuturalis and Paragloborotalia Based on the occurrence of turbidites, slumping
462 opimaopimainthelower200m,thisintervalcorre- and minor folding, this about 1.5km thick marine
463 latestothebiozoneP21.Theupper300mlackany succession is interpreted as deposits of a deep
464 agediagnosticplanktonicforaminifer. marinebasin.
OLIGO–MIOCENESETURKISHTETHYSFORELAND 115
465 ShallowmarineconditionsduringtheRupelian compression.Later,PliocenetoPleistocenealluvial
466 (P19) were replaced by rapid deepening of the fan,fluvialandlacustrinesedimentsweredeposited
467 basin during biozone P22, late Chattian. The end covering Early Miocene sediments (Cronin et al.
468 of the flysch deposition during the Chattianmarks 2000a,b;Aksoyetal.2005).
469 the emergence of the basin which probably Inthissetting,westudiedasectionsituatedinthe
470 remainedshallowmarineuntilthelateChattian. easternmost partofthe Elazıg˘ basin.Accordingto
471 Consideringthebiostratigraphicages,asedimen- the geologicalmapofTurkey(S¸enel2002), inthe
472 tation rate between 15 and 27cm/ is calculated. area east of the town Basyurt (Fig. 5), Lower to
ka
473 The constant water depth of 350 to 750m during MiddleEocenecontinentalclasticsunconformably
474 deposition indicates approximately 2km of subsi- overly Mesozoic ophiolitic me´lange. These clastic
475 dencethroughouttheOligocene,followedbyrapid sedimentsare,inturn,overlainbyeitherMiocene–
476 upliftandexposureofthesuccessionafterthelate Plioceneclasticorvolcanicrocks.
477 Chattian.Ourbiostratigraphicdatesbasedonplank- ThebasalpartofthestudiedGevlasuccession,
478 tonicforaminifersintheflyschdepositscorroborate about 15km NE of Basyurt, starts with bluish
479 theagespublishedpreviouslybasedondinoflagel- marine clay containing bivalves, followed by an
480 latesandpalynomorphs(Sancayetal.2006). alternation of clay and sandstone (the sandstones
481 are up to 50cm thick or about 5m thick with
482 GeologicalsettingoftheElazıg˘ basin crossbedding)(Fig.6).Adistinctlayerwithabun-
483 dant bivalves and gastropods is located at about
484 ThestudiedGevlasectionissituatedintheeastern- 50mstratigraphicposition.Threedistinctlimestone
485 most part of the Elazıg˘ basin, about 40km NE of layersoccurbetweenabout100mand260mstrati-
486 Elazıg˘ (Fig. 2). The basin has been studied by graphic level. The first one, at about 100m, is a
487 several workers; however, the literature has been nodular limestone with shell fragments, sponges
488 published mostly in Turkish (see Aksoy et al. (upto30cm)andcorals,followedbytwonummu-
489 2005) and no detailed information is available for liticlimestonehorizons,at244mand255m.Thisis
490 the easternmost part of the basin. At present, the followedbyabout400mofblueclaygradinginto
491 basin fill is exposed in an NE–SW belt in the a 600m thick succession of alternating clay and
492 easternTauridesofAnatolia.Thegeneralizedstrati- sandstone, whereby the sand layers show typical
493 graphyoftheTertiarysedimentshasbeendescribed transport characteristics, such as shell fragments,
494 as:lowerPaleocenecontinentaldepositsatthebase,
495 followed by upper Paleocene to lower Miocene
496 marinedepositsandfinallyPliocenetoQuaternary
497 continental deposits. The basement of the Elazıg˘
498 basin is formed by Permo-Triassic metamorphic
499 rocks, namely Keban Metamorphics, which were
500 emplaced over upper Cretaceous magmatic rocks
501 north of Elazıg˘ (Perinc¸ek 1979; Perinc¸ek &
502 O¨zkaya 1981; Aktas¸ & Robertson 1984; Bingo¨l
503 1984;Aksoyetal.2005).
504 Detailed stratigraphic, sedimentological and
505 tectonic characteristics of the Elazıg˘ area have
506 been discussed elsewhere (e.g. Perinc¸ek 1979;
507 Perinc¸ek & O¨zkaya 1981; Aktas¸ & Robertson
508 1984; Bingo¨l 1984; Cronin et al. 2000a, b; Aksoy
509 et al. 2005). From the late Paleocene, shallow
510 marine carbonates, deposited in an extensional
511 back-arcsetting,wereaccumulatedwhenthebasin
512 further subsided until Middle to Late Eocene
513 (Aksoy et al. 2005). During Oligocene to early
514 Miocene, after reaching its maximum extend
515 during the Middle to Late Eocene, deposition was
516 restrictedtotheN–NWandbecameprogressively
Fig.5. Simplifiedtectonicandgeologicalmapofthe
517 shallower,indicatedbyOligocenereefallimestones
easternmostpartoftheElazıg˘basin.Thetrajectoryofthe
518 until the final subaerial exposure at the end of
studiedsection,calledGevla,isabout15kmNEofthe
519 Oligocene.MarineMiocenedepositsarerestricted
cityBasyurtandcoverstheintervalbetweenEocene
520 to small areas in the basin and more widespread limestonesandMiocenevolcanicstothenorth.Forkey
521 northofthebasin.FromMiddleMioceneonwards tothelithologiesand/oragesrefertoLegend(drawn
522 the basin was affected by a strong, North–South, afterGeologicalmapofTurkey(S¸enel2002)).
116 S.K.HU¨SINGETAL.
523 displacednummulitesandgastropods(forinstance
524 at 663m and 1158m), fining upward sequences
525 and cross bedding. These layers are interpreted as
526 turbiditicinorigin.Thissuccessionisfollowedby
527 about 300m of blue clay, and the section ends
528 with a 50m thick limestone with bivalves (up to
529 5cm), and clayey intervals with well preserved
530 echinoderms,spongesandcorals.Theselimestones,
531 inturn,arecoveredbyMiocenevolcanicrocks.In
532 total,thesectionisabout1.6kmthick.
533 Slumpingatseverallevelswithinthesuccession
534 indicates an unstable submarine slope. Internal
535 foldingis notobserved withinthe succession. The
536 entiresuccessiongentlydipstowardstheNW.
537
538
BiostratigraphicresultsoftheElazıg˘ basin
539
540 Handsampleswerecollectedfromaboutevery20m
541 throughouttheentiresection,butnoteverysample
542 contained (diagnostic) planktonic and/or benthic
543 foraminifers. The number of foraminifers is extre-
544 mely variable and most likely fluctuates with
545 changes in terrigenous clastic input. Preservation
546 isgenerallypoor,withspecimensmostlyrecrystal-
547 lized and frequently distorted. The overall aspects
548 of the planktonic foraminiferal fauna in this
549 sectionissimilartothatoftheMus¸section,which
550 means that the foraminiferal fauna is dominated
551 by globoquadrinids and catapsydracids with
552 occasional occurrences of Globigerina ciperoensis
553 and Globigerina angulisuturalis pointing to an
554 Oligocene age for this section (Fig. 6) (Berger &
555 Miller 1988; Spezzaferri & Premoli Silva 1991).
556 The presence of Turborotalia ampliapertura up to
557 and including level 287m (TR 244) provides
558 evidencethatthelowerpartofthesectioncorrelates
559 with planktonic foraminiferal biozone P19 of
560 Berger & Miller (1988), which is late Rupelian,
561 early Oligocene, in age (Berggren et al. 1995).
562 ThelowestoccurrenceofGlobigerinaangulisutur-
563 alisisrecordedat477m(TR250)whichinterms
564 of the zonal scheme of Berger & Miller (1988)
565 would mark the top of biozone P20 although it
566 shouldbenotedthatGlobigerinaangulisuturalisis
567 neither frequent in this section nor does it display
568 veryprominentU-shapedsutures.TypicalParaglo-
569 borotaliaopimaopimaispresentfromlevel317m
570 (TR245)uptoandincludinglevel1445m(TR293)
571 indicating that the larger part of the Gevla section
572 correlates with planktonic foraminiferal biozone
573
574
575
576 Fig.6. LithologicalcolumnofthestudiedGevlasection Fig.6. (Continued)toplanktonicforaminiferzones,
577 intheElazıg˘basinwiththebiostratigraphicresults. which,inturn,aretiedtostagesduringtheOligocene
Theagemodelisbasedonplanktonicforaminifersand resultingintoacorrelationtotheGeologicalTimeScale.
578
macrofossilassemblageinthe50mofstratigraphy. RefertoLegendinFigure4forkeytolithologies,
579
Planktonicforaminiferoccurrenceshavebeencorrelated structuresandfossils.
580