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Turkish Journal of Earth Sciences (Turkish J. Earth Sci.), Vol. 17, 2008, pp. 263–296. Copyright ©TÜB‹TAK First published online 26 December 2007

Cretaceous Pelagic Red Beds and Black (-), NW Turkey: Global Oceanic Anoxic and Oxic Events

‹SMA‹L ÖMER YILMAZ

Department of Geological Engineering, Middle East Technical University, TR–06531 Ankara, Turkey (E-mail: [email protected])

Abstract: The study areas located near the towns of Göynük, Mudurnu and Nall›han in the central northwestern part of Turkey lie on the ‘Sakarya Continent’, which is one of the tectonic entities of the geology of Turkey. Measured stratigraphic sections comprise the Aptian pelagic carbonates and the overlying turbiditic sequences, which are all capped by a Late Santonian red pelagic succession. Lower and Upper Aptian, Upper Albian and / marine black shales recognized in the sections are followed by Lower and Upper Aptian, Upper Albian and Turonian marine red beds. The black shales are generally silty, laminated, and include pyritized radiolarian and planktonic . The red beds are composed of red-pink , which are of packstone with abundant planktonic foraminifera, bivalve, echinoidea, iron infillings and coatings. They also include red silty marls with , iron and glauconite minerals as well as bivalve fragments. Sedimentologic, sequence stratigraphic and cyclostratigraphic properties of black shales and red beds recorded along the measured stratigraphic sections have been determined and Fischer plot analysis has been applied for their correlation and coherency. Their sequence stratigraphic positions and cyclic nature indicate that black shales were generally deposited in the early transgressive system tracts. However, red beds represent the late transgressive/high-stand systems tracts. In some areas, the Upper Santonian red beds are observed in association with a drowning event and overlie a Type-3 sequence boundary. Their stratigraphic position and sedimentology are used to better understand the oceanic events and tectonic movements recorded in this basin. These black shales and red beds are recognized within coeval biostratigraphic intervals as in their global counterparts.

Key Words: Cretaceous, red beds, black shales, global anoxic and oxic events, sedimentology, cyclostratigraphy, sequence stratigraphy, NW Turkey

Kretase Pelajik K›rm›z› Tabakalar› ve Siyah fieylleri (Apsiyen–Santoniyen), Kuzey Bat› Türkiye: Küresel Anoksik ve Oksik Olaylar

Özet: Türkiye’nin orta kuzeybat›s›nda yeralan ve Göynük, Mudurnu ve Nall›han yak›nlar›n› kapsayan çal›flma alanlar› Türkiye’nin Kretase jeolojisinin önemli tektonik dilimlerden biri olan Sakarya K›tas› üzerinde bulunmaktad›r. Ölçülü stratigrafik kesitler Apsiyen pelajik karbonatlar›n› ve üzerine gelen Üst Santoniyen–Kampaniyen k›rm›z› tabakalar› ile örtülmüfl Albiyen–Koniyasiyen türbiditik istiflerini içermektedir. ‹stiflerde tan›mlanm›fl olan Alt ve Üst Apsiyen, Üst Albiyen ve Senomaniyen/Turoniyen denizel siyah fleyllerinin Alt ve Üst Apsiyen, Üst Albiyen ve Turoniyen denizel k›rm›z› tabakalar› ile takip edildi¤i gözlenmifltir. Siyah fleyller genellikle siltli, laminal› ve piritleflmifl radyolarya ve planktonik foraminifer içermektedir. K›rm›z› tabakalar ise bol planktonik foraminifera, bivalve, ekinid, demir dogular› ve kaplamalar› içeren istif tafl› fasiyesindeki k›rm›z›-pembe renkli kireçtafllar› ile bivalve k›r›nt›lar›, glakoni, demir ve kuvars içeren siltli k›rm›z› marnlardan oluflmaktad›r. Bu çal›flmada ölçülü kesitler boyunca incelenmifl olan siyah fleyllerin ve k›rm›z› tabakalar›n sedimentolojik, sekans stratigrafik ve devirsel stratigrafik özellikleri tespit edilmifl ve Fischer e¤rileri ç›kar›larak kontrolleri ve karfl›lat›rmalar› yap›lm›flt›r. Sekans stratigrafik pozisyonlar› ve devirsel stratigrafik yap›lar› siyah fleyllerin genellikle erken transgresif sistemlerde çökeldi¤i fakat k›rm›z› tabakalar›n ise geç transgresif/yüksek durufl sistemleri temsil etti¤ini göstermektedir. Yer yer, Üst Santoniyen k›rm›z› tabakalar›n›n bo¤ulma olaylar› ile iliflkili olduklar› ve Tip-3 sekans s›n›rlar›n› üzerledikleri görülmüfltür. Sedimantolojisi ve stratigrafik konumlar› havza içerisindeki kay›tlanm›fl okyanusal olaylar›n ve tektonik hareketlerin daha iyi anlafl›lmas›nda kullan›lm›flt›r. Tespit edilmifl olan siyah fleyller ve k›rm›z› tabakalar küresel efllenikleri ile benzer biyostratigrafik aral›klarda gözlenmifltir.

Anahtar Sözcükler: Kretase, k›rm›z› tabakalar, siyah fleller, küresel anoksik ve oksik olaylar, sedimantoloji, devirsel stratigrafi, sekans stratigrafisi, KB Türkiye

263 CRETACEOUS OCEANIC ANOXIC AND OXIC EVENTS, NW TURKEY

Introduction In Turkey, Upper Cretaceous red beds were recorded The Cretaceous period has long been analyzed worldwide in the Pontides by Görür et al. (1993), Eren & Kadir for oceanic, climatic and tectonic events. Several studies, (1999), Eren & Taslı (2002) and Tüysüz (1999, 2002, especially those concerning organic carbon-rich black 2003) within Upper Cretaceous turbidite sequences. Eren occurrences within pelagic successions in the & Kadir (1999) studied the major oxide elements and Cretaceous are related to ‘Cretaceous oceanic anoxic emphasized the diagenetic colouring of the red beds in events’ (Schlanger & Jenkyns 1976; Jenkyns 1980; the eastern Pontides. Reyment & Bengtson 1985; Rawson et al. 1996; Erba The black shale interval recorded in the Lower Aptian 2004; Erbacher et al. 2007 and many others). A number deposits in the Nallıhan area of northwestern Turkey has of discussions have been published on the origin and been studied by Yılmaz et al. (2004a) and interpreted as causes of the global oceanic anoxic events in the OAE1a. The black shale interval at the , Aptian, Albian, Cenomanian/Turonian and Cenomanian/Turonian boundary in the Antalya area of Late Santonian– stages from many parts of the southwestern Turkey was studied by Yurtsever et al. world (Schlanger & Cita 1982; Herbert & Fischer 1986; (2003), and interpreted as equivalent to the ‘Bonarelli’ Jenkyns & Clayton 1986; Bralower et al. 1994; Barrera level (OAE 2). & Johnson 1999; Herrle et al. 2003; Skelton et al. 2003; The present study mainly focuses on the Erba 2004; Coccioni et al. 2006). Carbon and oxygen sedimentology and stratigraphy of the Lower and Upper stable isotopes together with other geochemical analyses Cretaceous pelagic red beds and black shales recorded carried out on these anoxic sediments have been of special within an intra-basinal trough on the Sakarya Continent interest (Weissert & Bréhéret 1991; Weissert & Lini (Figure 1). Their petrographic, sequence stratigraphic 1991; Menegatti et al. 1998; Jenkyns & Wilson 1999; and cyclostratigraphic analyses are discussed and a Stoll & Schrag 2000; Wissler et al. 2001; Price 2003; correlation is established based on their Yılmaz et al. 2004a). Cyclostratigraphic and sequence chronostratigraphic positions within the basin. stratigraphic analyses of these black facies have also been Comparison of the results with coeval global Cretaceous applied to explain their mode of occurrences (Herbert & oceanographic events is presented as evidence of global Fischer 1986; Einsele et al. 1991; Claps & Masetti 1994; anoxic and oxic events also recorded on the Sakarya Claps et al. 1995; House & Gale 1995; Yılmaz et al. Continent. 2000, 2004a, b; Einsele 2001; Yılmaz 2002). Pelagic red bed occurrences in the Cretaceous within the concept of global oceanographic events have been less Geologic Setting studied compared to black shales. In the The study areas are located on the former Sakarya (, Aptian, Albian) and Continent, which is surrounded by the Intra-Pontide (Cenomanian–Turonian, Santonian–Campanian, suture zone to the north, and the ‹zmir-Ankara-Erzincan Maaestrichtian) epochs, pelagic red beds are documented suture zone to the south. Both are related with the all around the world from the north Atlantic to China closure of the northern branch of the Neotethyan Ocean (Malata et al. 2002; Tüysüz 2002, 2003; Jansa 2003; (Figure 1). The areas studied on this former continent Hu et al. 2005a, b; Wang et al. 2005; Yılmaz & Altıner include, from west to east, Göynük, Mudurnu and 2005a, b, c, 2006). Their consistent occurrences during Nallıhan, which are parts of a rift basin along the Sakarya certain time intervals have been interpreted as evidence Continental margin called the Mudurnu Trough (Koçyi¤it of global oceanographic events (Hu et al. 2005a, b). et al. 1991) as shown in Figure 2. Furthermore, geochemical analyses carried out on the red The Palaeozoic metamorphic basement, and the beds have also been used as an important tool to overlying Mesozoic and Cenozoic sedimentary succession understand their genesis (Hu et al. 2005a, b; Wang et al. can be observed as three main rock units on the ‘Sakarya 2005). However, sequence stratigraphic and Continent’. Palaeozoic basement metamorphic rocks were cyclostratigraphic approaches to analyse their mode of overthrust by metamorphics and their non- occurrences and genesis have not been used extensively in metamorphic equivalents during the Karakaya Orogeny. their study. All these amalgamated rock assemblages are in turn

264 ‹.Ö. YILMAZ o o o 38 40 45 N 100 km Van Lake 0 EAAC

SUTURE o 40

EASTERN PONTIDES ANATOLIAN ARABIAN PLATFORM Sea 1997).

FRAGMENT et al.

SOUTHEAST BLOCK

o SUTURE 35 o 35 Sea BLOCK

RHODOPE - PONTIDE TAURIDE KIRÞEHÝR Lake Tuz INNER

ANATOLIDE Ankara

SUTURE SUTURE o 30

Black ÝSTANBUL ZONE ÝSTANBUL ANTALYA o

30 TAURIDE CONTINENT

Mediterranean

study area

NCAN

Ý Sea ERZ

Marmara ANKARA

- ÝZMÝR Geographic locations of the study areas on the tectonic suture map of Turkey (modified from Yılmaz SAKARYA

o o o 38 Sea Aegean 36 40 Figure 1.

265 CRETACEOUS OCEANIC ANOXIC AND OXIC EVENTS, NW TURKEY

AKTAÞ BÝGA-BURSA-BÝLECÝK MUDURNU TROUGH SEKÝNÝNDORUK CARBONATE PLATFORM HIGH

Korkayasý Yedimezarlar WSW High High ENE KinikGünören Vezirhan Mudurnu Edremit High Trough Trough Göynük Nallýhan

Hauterivian - Aptian pelagic limestones Valanginian (Soðukçam ) shallow water carbonates (Bilecik Group) Callovian pelagic calciturbidites (Yosunlukbayýrý basement Formation) (a) rocks (Koçyigit et al. 1991) Aptian Bajocian -

Göynük Mudurnu Nallýhan WSW ENE

pelagic limestone and marl/shale alternation (Vezirhan Formation) siliciclastic-volcaniclastic turbidites (Üzümlü Member)

(Soðukçam Formation) pelagic limestones shallow water carbonates (Günören Limestone) pelagic limestones (Soðukçam Limestone)

pelagic calciturbidites (b) (Yosunlukbayýrý Formation)

Göynük Mudurnu Nallýhan

WSW ENE

Degirmenözü Member (Yenipazar Formation)

pelagic limestone and marl/shale alternation siliciclastic-volcaniclastic turbidites (Vezirhan Formation) (Üzümlü Member)

(Sogukcam Formation) Pelagic limestones shallow water carbonates (Günören Limestone) pelagic limestones (Soðukçam Limestone)

(c) pelagic calciturbidites (Yosunlukbayýrý Formation)

Figure 2. Schematic reconstruction of tectono-stratigraphic development in the Mudurnu Trough, (a) Aptian (Koçyi¤it et al. 1991), (b) Albian–Cenomanian, (c) Late Santonian–Campanian. The drawings are not to scale.

266 ‹.Ö. YILMAZ

unconformably overlain by transgressive Liassic (Lower (Sigal) zones, respectively; the last zone is recognized in ) successions, including ‘Ammonitico Rosso’ facies the Late Albian within the of B. breggiensis (Altıner et al. 1991). The overlying Upper Jurassic to (Gandolfi) (Figure 3). Cretaceous succession starts with alternating shelf Deposits assigned to the Late Cretaceous show two carbonates, pelagics, volcanics, cherts, and volcaniclastics, levels of red beds. One is within the D. asymmetrica and continues with Upper Cretaceous slope and basinal (Sigal) zone assigned to the Late Santonian age, and the deposits. In the Göynük, Mudurnu and Nallıhan areas, the other is in the W. archaeocretacea (Pessagno) zone Barremian–Aptian slope/basin pelagic carbonates corresponding to the Latest Cenomanian to Early represented by the So¤ukçam Limestone form the lower Turonian age (Figure 3). part of the studied successions. These pelagic deposits have been interpreted to represent transgressive cover that developed over the Mudurnu Trough (Önal et al. Lithostratigraphy 1988; Altıner 1991; Altıner et al. 1991) and are The Lower Cretaceous pelagic red beds constitute associated with a drowning event (Figure 2). The prominent levels at the top of the So¤ukçam Limestone So¤ukçam Limestone is characterized by pelagic and within the lower part of the Üzümlü Member of the carbonates without any visible volcanic or chert Yenipazar Fomation (Figure 3). The Lower and Upper intercalations, and can be distinguished from other Aptian red beds occur just at the boundary between the formations by its distinctive limestone-shale/marl So¤ukçam Limestone and the Üzümlü Member and are couplets. Unconformably overlying the So¤ukçam overlain by turbiditic successions. They are underlain by Limestone is the Üzümlü Member of the lower part of the an alternating sequence of white-cream coloured pelagic Yenipazar Formation, which is characterized by an limestone and marl/shale. The Upper Albian red beds Albian–Cenomanian turbiditic succession. This unit is a occur within the marly interval of turbidites which are part of the turbiditic basin that developed widely on the composed of alternation of thin- to medium-bedded, ‘Sakarya Continent’ (Figure 2). The upper units in the parallel laminated or partly bioturbated, arkosic, studied successions consist of red-pink litharenitic or wacke with normal graded Santonian–Campanian pelagic limestones and marls bedding, shales/mudstones and thin-bedded polygenic (De¤irmenözü Member of Yenipazar Formation) (Timur conglomerates with fining-upward structures displaying & Aksay 2002), which form a prominent marker interval part of a Bouma sequence. in the basin (Figure 2). They show an unconformable contact with the underlying turbiditic sequence, whereas They are overlain by grey coloured marl/shales and the upper part grades into the superjacent succession of turbiditic sandstones, whereas they are underlain by Campanian– age (Yenipazar Formation), interbeds of purple-brown turbiditic and dark which consists of turbidites. grey-black coloured marl/shale (Figure 3). Twelve stratigraphic sections have been measured and The Upper Cretaceous pelagic red beds (De¤irmenözü correlated in between and within the basin. Member) unconformably overlie Lower Cretaceous turbiditic successions, and intergrade with overlying turbiditic successions (Yenipazar Formation). The Red Beds

Biostratigraphy Sedimentology The biostratigraphic framework of the pelagic red beds is The red beds recorded in the Early and Late Aptian (both conformable to the of planktonic foraminifera in G. blowi - L. cabri zone and G. algerianus - P. given in De Graciansky et al. (1998). The Early cheniourensis zones) consist of red to pink (ranging from Cretaceous includes three levels of red beds in the moderate pink [5R 7/4], light red [5R 6/6], moderate red studied sections: two are recognized in the Lower and [5R 4/6] to very dark red [5R 2/6], of The Rock-Colour Upper Aptian within the upper part of the G. blowi (Bolli) Chart [Geological Society of America 1995]) limestones – and the lower part of the L. cabri (Sigal) and G. and marls in the Mudurnu and Göynük areas (So¤ukçam, algerianus (Cushman and Ten Dam) - P. cheniourensis De¤irmenözü, Samsaçavufl, Mudurnu and Sünnetgölü

267 CRETACEOUS OCEANIC ANOXIC AND OXIC EVENTS, NW TURKEY

Nannofossil zones Ma Polarity Planktonic / NC OAEs Formations anomaly foraminiferal zones Lithology Stages 65 65 29R /Members 30N1 23 A. mayaroensis 31N Late Degirmenözü MAA D. assymetrica 22 C. contusa R. fructicosa Santonian Member 70 31R 21 71.3 32N1 G. gansseri unconf. 32R1 32N2 G. aegyptiaca 32R2 20 75 G. havanensis G. calcarata 33N 19 G. ventricosa CAM not zoned 80

33R 18 G. elevata Coniacian? 83.5 85 SAN 17 D. asymetrica 85.8 16 H. helvetica ? CON D. concavata OAE3? 89 15 W. archaeocretacea ? 90 14 D. primitiva M. sigali TUR H. helvetica 13 93.5 12 W. archeocretacea OAE2 95 Dicarinella R. cushmani ‘Bonarelli’ - ‘Thomel’ CEN 11 algeriana R. reicheli R. greenh. ‘Bahloul’ R. cushmani - Turonian - 98.9 R. brotzeni

100 10 R. appenninica OAE1d Cenomanian Upper R. ticinensis ‘Pialli’ - ‘Breistroffer’ not zoned Yenipazar Formation Yenipazar R. subticinensis Üzümlü Member 9B OAE1c T. praeticinensis not zoned 105 ALB May ‘Amadeus’ - ‘Toolebuc’ contain 9A B. breg - giensis brief subchrons T. primula

8B H. rischi 110 H. planispira OAE1b 112.2 8A

T. bejaouaensis ‘Urbino’ - ‘Leenhardt’ 7B ‘Monte Nerone’ - ‘Paquier’ 115 H. trocoidea ‘113’ - ‘Jacob’ ISEA Acme N. trutti APT G. algerianus Albian Upper 7A B. breggiensis G. ferreolensis OAE? ‘Renz’-‘Thalmann’-‘Fallot3’ 120 L. cabri OAE1a 6 121 CMO ‘Selli’-‘Goguel’ G. blowi CM1 5 not zoned Uncf. BAR CM2 D+E H. similis-H.mitra 125 CM3 G. algerianus -

125.8 Nannoconid CRISIS FARAONI CM4 5C H. sigali-H.semielongata CM5 P. cheniourensis CM6 5B OAE CM7 5A CM8 HAUT CM9 4B 130 CM10 H. sigali-H.infracretacea G. ferroelensis So•ukçam CM10N 4A Limestone 131.5 CM11 WEISSERT CM11A 3B

VAL CM12 OAE G. blowi - Aptian Upper CM12A H. sigali-H.intermedia 135 CM13 3A L. cabri 135.9 CM14 CM15 2 not to scale CM16 Caucasella hoterivica BER CM17 1 140 Nannoconid DECLINE Coccioni et al. 2006

white to beige coloured sandy pelagic limestone and marl alternation red to pink coloured pelagic marls/mud stones

yellowish to orange coloured radiolarian chert turbiditic sandstone - shale/mud stone alternations

white to cream coloured pelagic limestone and marl/shale alternation red to pink colored pelagic limestones and marls

black shales/mud stones

Figure 3. Biostratigraphic framework of the studied intervals in the Mudurnu and Göynük areas, and the position of black shales and red beds. sections) presently separated from each other by a moderate red; 5R 5/6) are of packstone facies (Figure distance of 60 km (Figures 4–9). Compared to the 10a) and the red marls (moderate-very dark red; 5R 3/6) underlying limestones, these facies show a sudden and limestones include reddish iron crystals, a few green increase in the abundance of planktonic foraminifera, minerals (glauconite) in the micritic/clayey matrix bivalves and echinoidea. The red limestones (light- together with reddish iron infillings within the chambers

268 ‹.Ö. YILMAZ

Sogukçam Section biozone/ sample chronozone stages 25 m numbers

red to pink pelagic limestones and marls B. breggiensis ?

5 UPPER ALBIAN UPPER white to cream pelagic limestones and marls ? ?

dark grey to greenish P. cheniourensis 4 pelagic shales and 3 mudstones

G. algerianus 2 grey to greenish turbiditic sandstones UPPER APTIAN UPPER 1 0 m

Figure 4. The So¤ukçam measured stratigraphic section. of planktonic foraminifera. Silicilastic silt/sand 8) are composed of quartz silt/sand, phosphorite clasts, components are rarely observed in the limestones, and reddish iron minerals, planktonic foraminifera, and there is no apparent bioturbation in the red limestones calcareous micritic matrix (Figure 10d) and display fine and marls. Marl facies exhibit fine laminae composed of parallel laminae. Reddish iron crystals are disseminated in an alternation of quartz silt and iron rich mud. the micritic/clayey matrix, and the chambers of foraminifera are also filled with very fine reddish iron In the Mudurnu section (Figures 8 & 11a, b), red to oxides. pink limestones are cut across by ‘Neptunian dyke’-like structures at the contact with superjacent Upper Albian Planktonic foraminifera are relatively more abundant turbidite successions. These structures are filled with in these red marls than in the underlying sandy beds as purple to brown (between greyish red purple [5RP 4/2] well as in the overlying grey marls and mudstones (Figure and pale purple [5P 4/2]) calcareous sand that includes 11c). angular quartz and feldspar grains, glauconite, iron The Turonian in the Göynük-Sünnet section (Figure minerals, abundant planktonic foraminifera and 12) shows red coloured marls/shales (moderate red; 5R belemnites. Cracks penetrate into the underlying 4/6) overlying the yellow to reddish (between dark limestones to about 1 meter (Figures 8–10). Sandy yellowish orange; 10YR 6/6) and greyish orange (10YR limestones with abundant bivalve shells occur just above 7/4) cherty interval. The red marls/shales are succeeded the contact zone (Figures 8, 10b & 11a, b). The sandy by the alternation of white-cream coloured bioturbated limestones contain intraclasts of underlying pelagic limestones with calcareous sandstones which is in turn is limestones, quartz and feldspar grains, glauconite, iron followed upwards by Upper Cretaceous Red Beds of Late minerals and Upper Albian planktonic foraminifera. This Santonian age (Figure 13d). boundary is interpreted as an unconformity The Upper Cretaceous (Upper Santonian) red beds (disconformity) between two different formations and (moderate-very dark red; 5R 3/6) occur in all sections best observed in the Mudurnu section. studied, and crop out extensively in the study areas. They In the Upper Albian, red marls/shales (moderate-very are mainly composed of alternating red-pinkish dark red; 5R 3/6) that occur in the Mudurnu area (Figure limestones and marls, and occasional thin volcanic tuff

269 CRETACEOUS OCEANIC ANOXIC AND OXIC EVENTS, NW TURKEY

Çavuþdere Section

biozone/ sample numbers stages chronozone 80 m red to pink pelagic limestones UPPER SANT. D. asym. 9 unconformity white to cream pelagic limestones

red to pink pelagic marls ?

orange to brownish cherts

dark grey to greenish pelagic shales and mudstones 8

? black shales 7 dark grey to grey UPPER CENOMANIAN - TURONIAN ? 6 turbiditic 5 sandstones 4

3 dark grey to grey calcareous 2 sandstones UPPER R. cushmani

CENOMANIAN grey to beige 1 limestones 0 m

? grey to greenish sandstones

Figure 5. The Çavufldere measured stratigraphic section. layers intercalated with the reddish limestones. A some levels within the limestones. In addition to Globotruncana packstone facies is the characteristic structures like ‘Neptunian dykes’ filled with sandy feature of the red beds (Figure 10f). In the Mudurnu materials, some iron oxide nodules or impregnations and area, these red levels unconformably overlie siliciclastic some bioturbations filled with dark red or purple muddy turbidite successions (Figure 11d). In the ‹smailler materials also occur at the contacts with the red beds. (Figure 14) and the Mudurnu sections (Figure 8), red The presence of transported/reworked ‘Inoceramus’ chert (very dark red; 5R 2/6) nodules are present at shells in the limestones of the Mudurnu area indicates

270 ‹.Ö. YILMAZ

Deðirmenözü Section sample biozone/ numbers stages chronozone 70 m red to pink pelagic marls UPPER D. asym. 16 SANT. 15 unconformity? red to pink pelagic limestones

white to cream pelagic limestones

14 dark grey to greenish 13 pelagic shales and mudstones 12 11 10 9 grey to beige 8 limestones 7

P. cheniourensis P. 6 5 black shales 4 3 dark grey to grey turbiditic

UPPER APTIAN UPPER 2 1 sandstones

dark grey to grey calcareous 0 m sandstones G. algereanus ? G. algereanus

Figure 6. The De¤irmenözü measured stratigraphic section. that calcareous materials from shallower environments In the sequence stratigraphic concept, the red beds were occasionally transported into the pelagic display two different positions in the basin. One is related environment. Iron oxide is present as crystals to a Type-3 sequence boundary and the other is related disseminated within the micritic matrix and as a fine- to late transgressive system tracts. The Upper Aptian red- grained infilling material within the chambers of pinkish limestones/marls are interpreted as related to planktonic foraminifera. high-stand/still-stand system tracts below a Type-3 sequence boundary (Schlager 1999). At this boundary, red Upper Aptian pelagic limestones are overlain by Upper Sequence Stratigraphy and Cyclostratigraphy Albian–Cenomanian siliciclastic turbidites in the Mudurnu High resolution cyclostratigraphic and sequence area. The unconformity surface between turbidites and stratigraphic analyses have been carried out in the red beds is easily marked by the presence of the infillings Mudurnu and ‹smailler sections. The other sections were of the overlying siliciclastic materials down into the analyzed at lower resolution, but in conjunction with the underlying limestones through ‘Neptunian dyke’ like results of these two sections and within their same structures (Figure 11a, b). Belemnites are abundant biostratigraphic framework and their coeval global throughout the turbiditic succession and even within the counterparts (Figure 3). infilling of sandy materials. Just above this boundary, the

271 CRETACEOUS OCEANIC ANOXIC AND OXIC EVENTS, NW TURKEY

Samsaçavuþ Section

biozone/ sample numbers stages chronozone 80 m

UPPER SANT. D. asym. red to pink 11 pelagic limestones Unconformity? ? ? white to cream pelagic limestones 10

red to pink pelagic marls 9

8 dark grey to greenish pelagic shales and mudstones

T. roberti ?-B. breggiensis roberti T. 7

dark grey to grey turbiditic

UPPER ALBIAN UPPER 6 sandstones 5

B. breggiensis ? B. breggiensis dark grey to grey calcareous sandstones ?

LOWER L. cabri 4 grey to beige APTIAN G. blowi 3 limestones 2 1 purple to brownish 0 m sandstones BARREMIAN - BARREMIAN APTIAN ?

Figure 7. The Samsaçavufl measured stratigraphic section. presence of shell accumulations with some iron and deposited in upper slope pelagic conditions, but relatively glauconite minerals is interpreted as sediment starvation shallow. Because there are no deep pelagic environment conditions and sudden increase in accommodation space. indicators, such as deep marine ichnofacies, deep marine Therefore, the Type-3 sequence boundary took place on benthic formaninifera or other organisms. Moreover, the these red beds, which were deposited during high- presence of iron minerals that can be terrestrial/volcanic stand/still-stand conditions and in comparison with in origin and a hiatus at the boundary indicate that these underlying succession are characterized by abrupt red beds are subjected to exposure conditions or very increase in abundance of planktonic foraminifera, bivalve shallow water conditions which can be enhanced by and echinoid fragments (Figure 10b), and the presence of extensional tectonics creating also ‘Neptunian dykes’. iron oxide minerals. The pelagic red beds were probably There is also no indication of CCD fluctuation to generate

272 ‹.Ö. YILMAZ

Mudurnu Section

sample biozone/ numbers stages chronozone 44.73 m red to pink pelagic limestones 19

UPPER white to cream SANTONIAN D.asymmetrica 18 pelagic limestones unconformity 17

16 red to pink pelagic marls 15 dark grey to bluish pelagic shales 14 and mudstones R.cushmani

dark grey to greenish pelagic shales and mudstones 13 UPPER CENOMANIAN

black shales ?

dark grey to grey 12 turbiditic sandstones

ALBIAN - 11

dark grey to grey calcareous sandstones CENOMANIAN UPPER 10 grey to beige 9 limestones 8 purple to brownish 7 sandstones 6

grey to greenish 5 conglomerates B. breggiensis UPPER ALBIAN UPPER

uncf. 4 purple to brownish sandy limestones with abundant bivalve 3 APTIAN penetration features 2 of “Neptunian Dyke” like structures infilled

P. cheniourensis P. with sandy materials

UPPER 0 m 1

Figure 8. The Mudurnu measured stratigraphic section.

273 CRETACEOUS OCEANIC ANOXIC AND OXIC EVENTS, NW TURKEY

biozone/ sample stages chronozone numbers Sünnetgölü Section

11

red to pink pelagic limestones L. cabri

10 white to cream pelagic limestones

9 black shales

8 7

6

APTIAN 5

4 32 m

G. blowi 15

3

14 G. algerianus

2

13 APTIAN G. ferrolensis 0 m 1 12

Figure 9. The Sünnetgölü measured stratigraphic section.

274 ‹.Ö. YILMAZ

a b

c d

e f

Figure 10. Photomicrographs of microfacies. White scale bar is 0.5 mm and applies for all. (a) Packstone with planktonic foraminifera of pink-red Aptian limestone in the Mudurnu section (Sample no. 20, Figure 15); (b) calcareous /sandstone with abundant bivalve shells of Late Albian age resting on the unconformity surface in the Mudurnu section (Sample no. 21, Figure 15); (c) arkosic-litharenite of the Mudurnu section (Sample no. 42, Figure 15); (d) purple-brownish silty marn with iron and phosphatic minerals in the Mudurnu section (Sample no. 75a, Figure 15); (e) silty black shale of Aptian age in the Sünnetgölü section (Sample no. 5, Figure 9); (f) red packstone with planktonic foraminifera of Late Cretaceous age in the ‹smailler section (Sample noç 12, Figure 14).

275 CRETACEOUS OCEANIC ANOXIC AND OXIC EVENTS, NW TURKEY

Üzümlü Member infilling sand and silts of Üzümlü Member

infilled cracks at the contact

Soðukçam Lmst. “Neptunian Dyke” like structures

a b

grey - dark grey marls and mudstones

purple -brownish c marls and mudstones d

black shale red beds

e f

g

276 ‹.Ö. YILMAZ

Figure 11. Field photographs of red beds and black shales: (a) The contact between the So¤ukçam Limestone (white unit) and Uzumlu Member (dark unit) in the Mudurnu secion (samples between 15–25, Figure 15); (b) close-up view of the penetration of sand/ along ‘Neptunian dyke’-like structures in a; (c) grey to dark grey marl/mudstones overlying purple-brownish marls/mudstones of Late Albian age in the Mudurnu section (samples between 75a–85, Figure 15); (d) red pelagic limestones of Santonian–Campanian age overlying black/dark shales/mudstones of Cenomanian age in the upper part of the Mudurnu section (samples between 16–19, Figure 8); (e) red- pink pelagic limestones and marls of L. cabri-G. blowi zone over the white limestones of Aptian age in the Samsacavus section (samples between 2–3, Figure 7); (f) Upper Aptian red to pink limestones/marls overlain by Upper Aptian turbiditic succession including black shale interval in the Degirmenözü section (samples between 7–14, Figure 6); (g) Aptian black shales in the Sünnetgölü section (samples between 4–7, Figure 9). Göynük-Sünnet Section

biozone/ sample red to pink stages chronozone cherty pelagic numbers limestones 65 m

white to cream pelagic limestones UPPER

D.asymmetrica 13 SANTONIAN Unconformity? 12 red to pink pelagic marls ?

orange to brownish 11 cherts TURONIAN H.helvetica 10 9 dark grey to greenish

LOWER-MIDDLE pelagic shales 8 and mudstones 7 Black shales W.archeocretcea

6 dark grey to grey turbiditic sandstones 5

dark grey to grey 4 calcareous sandstones R.cushmani 3 grey to beige 2 limestones UPPER CENOMANIAN

0 m 1 grey to dark grey mudstone/shale

Figure 12. The Göynük-Sünnet measured stratigraphic section.

277 CRETACEOUS OCEANIC ANOXIC AND OXIC EVENTS, NW TURKEY

a b

c d

Figure 13. Field views of outcrops of ‹smailler section: (a) shale-dominated bottom part of the section; (b) carbonate-dominated mid-part of the section; (c) chert interval in the upper part; (d) Upper Santonian red beds covering the top part of the section. this type of reddish carbonate successions overlain by that might have resulted from the sudden increase in calcareous sand that includes angular quartz and feldspar relative sea level, and interpreted as related to a Type-3 grains, glauconite, iron minerals, abundant planktonic boundary (Schlager 1999). foraminifera and belemnites. In the Early Aptian, of the G.blowi-L.cabri zone, red The De¤irmenözü section in the Göynük area (Figure marls/limestones (moderate red; 5R 4/6) are recorded 6), also includes upper Aptian red-pinkish only in the Samsaçavufl section, in the Göynük area limestones/marls (moderate-very dark red; 5R 3/6), but (Figure 7 & 11e), and they rest on Barremian–Aptian they are overlain by siliciclastic turbidites, including an white/cream coloured thin-bedded limestones alternating Upper Aptian black shale interval. The boundary is sharp with marls/shales. The contact between these units is and does not contain any exposure or hardground sharp and does not show any exposure/hardground structures, and neither hiatus. Although the content of structures. These red beds are overlain by a silciclastic the Upper Aptian red beds in the Mudurnu and Göynük turbidite succession of Late Albian age. However, the areas are the same, their respective contact with the boundary between red beds and turbidites could not be overlying successions is different. In both cases, the red observed because of the soil and vegetation cover. The beds are overlain by facies indicative of a drowning event presence of red beds in the G.blowi-L. cabri zone, which

278 ‹.Ö. YILMAZ

corresponds to the ‘Selli’ interval elsewhere (Yılmaz et al. generally rhythmicity occurs mainly as alternation of 2004a) has been interpreted to be related to a local sandstones and marls/black shales, or limestones and tectonic event associated with differential tectonic uplift marls/black shales, throughout the sections. Intervals of within the basin. This tectonism may have enhanced the the sections that show some degree of cyclicity such as formation of black shales within depressions, while the Albian red marls/mudstones include rhythmic allowing deposition of red beds on uplifted horst-like alternation with purple-brownish sandstones, as shown in blocks by percolating and upwelling waters, which might the middle part of the Mudurnu section (Figures 8 & 15). be rich in Fe and nutrients at that time and/or may be Also over the Late Santonian, the transition between red associated with volcanic or hydrothermal sources in the beds and the overlying turbiditic successions appears as area. alternating grey-greenish mudstone/sandstone and red- pink marls/mudstones. Therefore, the presence of The Upper Albian red marls/shales are interpreted as rhythmic alternation between red beds and turbidites related to late transgressive system tract. In the Mudurnu indicates that this transition may coincide with an increase and Göynük areas, these red beds are recorded within the in sea level in the sequence stratigraphic scheme. marly interval of the siliciclastic turbidites, which contain abundant phosphorite clasts and reddish iron minerals. Cyclicity observed in the ‹smailler section occurs as However, the adjacent marly intervals of the turbidite alternation of white to light grey bioturbated sequence do not contain any phosphorite clasts and iron limestones/marls and black shales/dark grey silty minerals. These marly intervals rest on sandy intervals mudstones in most of the section (Figure 16). They are and their positions are probably related to a late overlain by orange to brownish radiolarian cherts and transgressive system tract. Perhaps, they are related to grey marls, which are succeeded by red coloured sudden increase in nutrient and Fe content in the water marls/limestones that do not present any cyclicity. Since and associated with upwelling conditions during that the ‹smailler section is dominated by alternation of time. bioturbated limestones/marls and black shales/dark grey In the Late Cretaceous (Late Santonian), a 10–50-m- silty mudstones, changes in thickness increments of thick interval of alternating red limestones and limestones or shales are used to set up correlative marls/shales unconformably overlies the siliclastic conformities of sequence boundaries and system tracts turbidite succession of Late Albian–Cenomanian age (Figure 16). In the sequence stratigraphic framework, (Figures 5–8, 12 & 14). These red beds are interpreted carbonate-dominated intervals are taken as representing to be related to a drowning event that probably took the high-stand, and shale dominated intervals as place during sudden subsidence succeeding a major uplift transgressive system tracts in general. The red beds may phase in the basin. This drowning event could also be have taken place in late transgressive system tracts. The related to the sudden submergence of emerging ridges positions assigned to the sequence boundaries and system around the basin, as proposed in the case of the Outer tracts have been independently correlated within the Carpathian Cretaceous Basins between same biozones of the global sequence stratigraphy chart Albian–Cenomanian (Bak 2006). With this assumption, of De Graciansky et al. (1998), and it is found that the these red beds can thus be interpreted to be related to a number of sequences and the position of the red beds tectonically-affected Type-3 sequence boundary in the conform to the same numbers and transgressive intervals sequence stratigraphic concept. in the global chart, respectively (Figures 3 & 17). The intercalating pattern of the red beds indicates The recurrent variations of facies in the sections have that they are actually acyclic or arhythmic (Einsele et al. also been analyzed for sequence stratigraphic purpose. 1991; Einsele 2001). They display random occurrence in The parameters used include: appearance and clustering the ‹smailler section around the Cenomanian–Turonian of conglomerates at particular position within the boundary. However, some rhythmic alternations within sections (Figure 15); change in thickness of cycles along the red beds occur in the Late Albian interval in the the sections; change in position of carbonate or shale Mudurnu section (Figures 15 & 16). From detailed dominated intervals. They are used to set up sequence sampling in the Mudurnu and ‹smailler sections, the high- boundaries/correlative conformities, and system tracts in resolution cyclostratigraphic study further indicates that this type of pelagic settings. Independently from facies

279 CRETACEOUS OCEANIC ANOXIC AND OXIC EVENTS, NW TURKEY

Ýsmailler Section biozone/ stages chronozone sample numbers 95 m UPPER

D.asymmetrica 12 SANTONIAN unconformity? red to pink cherty pelagic limestones

white to cream pelagic limestones 11

H.helvetica red to pink pelagic marls

TURONIAN 10 9 orange to brownish 8 cherts

W.archeocretcea 7

6 dark grey to greenish pelagic shales and mudstones 5

black shales 4

grey to beige limestones 3 R.cushmani grey to dark grey 2 mudstone/shale UPPER CENOMANIAN 0 m 1

Figure 14. The ‹smailler measured stratigraphic section. analysis, Fischer plot curves (Sadler et al. 1993) have correspond to the end of the falling limbs of the curves been prepared for the Mudurnu and ‹smailler sections by indicating decreased accommodation space, whereas using patterns of change in cycle thicknesses along each black shales and red marls correspond to rising limbs thus section (Figure 18–20). They are analyzed for change in implying increased accommodation space. Red limestones accommodation space in relation to sea level fluctuations. associated with a type-3 sequence boundary are observed Sequence boundaries obtained by facies analysis towards the falling limbs due to high-stand conditions,

280 ‹.Ö. YILMAZ

Mudurnu Section sample numbers 44.73 m 163 sample numbers

87 86 85 84 83

82 R.cushmani ? 81 162 80 79 78 7776 CENOMANIAN ?

75b

75a 74 161 73 72 71 70 69 68 67 66 160 65 6463 62 61 60 159 59

58 57b ALBIAN 57a 158 56 157 55 54 156

53 ALBIAN ? 52 5051 155 49 154 48 153 47 152

B. breggiensis 46 45 151 44 150149 43 148147 146 42 145 144 41c 143 142 41b 141 41a 140 40 139 3938 138 37 137 36 136 135 35 134 133132 34 131 33 130 32 129 128 3130 29 126 127 28 125 27 124 123 26 25 122 24 121 23 120 119 SB 22 21 118 117 20 116 115 19 SB 114 18 ALBIAN ? 113 17 112111 16 110 1415 109 13 108 107106 1112 105 10 103 104 89 102 101 7 100 6 99 APTIAN 5 9897 4 96 94 95 3 92 93 2 91

P. cheniourensis P. 90 0 m 1 8889

Figure 15. High resolution lithostratigraphy of the Mudurnu measured section. Short black arrows represent cycles and long red arrows represent sequences. For facies descriptions see Appendix.

281 CRETACEOUS OCEANIC ANOXIC AND OXIC EVENTS, NW TURKEY

Ýsmailler Section

sample sample numbers numbers 22.48 m 44.44 m

35

34

45 33 32

31

30 44 29

43 28 sample numbers

27 58.93 m 26 56 25 42 55

24 54

23 41 TURONIAN 22 21 53 20

UPPER CENOMANIAN 19 18 UPPER CENOMANIAN

17 52 16 15

14

R.cushmani 40 R.cushmani

13

W.archeocretacea 51 12 50 39 11 49 10 38 48 9 37 8 7 6 47 5 36 4 3 46

2 UPPER CENOMANIAN 1 0 m 22.48 m 44.44 m

Figure 16. High resolution lithostratigraphy of the ‹smailler measured section. Short black arrows represent cycles and long arrows represent sequences. For facies descriptions see Appendix.

282

‹.Ö. YILMAZ

interval

shale dominated

Black black shale black chert red bed interval interval Section sequence boundary sequence boundary Ýsmailler not studied

Sünnet Section

Göynük- ? this study ? ries and system tracts with global Section

not studied not studied Çavuþdere ?

? Not observed Not WE boundary Sequence Section Mudurnu 93.29 93.90 94.50 H. helvetica R. cushmani W.archaeocretacea 95.39 (2004). ‘Global’

et al. H. helvetica Globotruncanids R. cushmani W. archaeocretacea W. top of low stand interval planktonic Foraminifera biochronostratigraphy maximum transgression/shematic condenced intervals (1998) R. cushmani H. helvetica 91.31 et al. Ce 4 Ce 5 Tu 1 Tu Tethyan De Graciansky 92.36 94.41 95.27 sequences major sequence boundaries minor sequence boundaries 1998). The age assigned in the brackets is from Gradstein

et al. Tu 1 Tu Ce 4 Ce 5 sequence Tu 1 Tu Ce 4 Boreal Europe / America North 94.99 93.99 92.36

Correlation of sequence boundaries, and occurrences of black shales and red beds in the ‹smailler section, with sequence bounda charts (De Graciansky

CENOMANIAN

0.2) ± LATE EARLY TURONIAN 93.5 ( Figure 17.

283 CRETACEOUS OCEANIC ANOXIC AND OXIC EVENTS, NW TURKEY

Fischer plot of Mudurnu Section 200

0 0 102030405060 -200

Albian Albian -400 black red beds shales Cenomanian -600 black shales -800

-1000

-1200

deviation of cycle thicknes from the mean deviation of cycle thicknes from -1400 sequence sequence boundary number of cycles boundary (Type-3)

Figure 18. Fischer plot curve of the Mudurnu detailed measured section.

Fischer Plot of Ýsmailler Section 300

0 0 102030405060708090 -300 Turonian -600 red bed interval -900

-1200

-1500

deviation of cycle thicknes from the mean deviation of cycle thicknes from -1800 sequence sequence boundary boundary number of Cycles

Figure 19. Fischer plot curve of the ‹smailler detailed measured section.

284 ‹.Ö. YILMAZ 180 170 Lower red beds Turonian 2004a). Dotted 2004a). 160

et al. et Yılmaz 150 black shale Cenomanian (this study, Üzümlü Member Mudurnu and 140 Ýsmailler sections) 130 red beds Upper Albian Upper

black shale

Upper Albian Upper Time gap Time 120 110 red beds Upper Aptian Upper 100 90 80 number of cycles number 70 60 Aptian black shale 50 40 30 Fischer Plot Curve of the Üzümlü Member and Soðukçam Limestone Plot Curve of the Üzümlü Member Fischer 20 (Yilmaz et al., 2004) (Yilmaz Sogukçam Limestone Fischer plot curve of the Üzümlü Member (Mudurnu and ‹smailler sections) and So¤ukçam Limestone (data from Nallıhan section of section Nallıhan from (data Limestone So¤ukçam and sections) ‹smailler and (Mudurnu Member Üzümlü the of curve plot Fischer line represents the boundary between two formations. 10 Figure 20. 0 0

800 600 400 200 -200 -400 -600 -800

1000

-1000 -1200 -1400 -1600 -1800 -2000 -2200 -2400 -2600

Mean

deviation from the mean cycle thickness cycle mean the from deviation Daviation from the from Daviation

285 CRETACEOUS OCEANIC ANOXIC AND OXIC EVENTS, NW TURKEY

which implies a high-stand system tracts/falling stage Mudurnu area that includes the Lower Aptian black shale system tracts just before the sudden drowning. interval (Sünnetgölü section) (Figure 9). Alternating beds The low-stand system tracts are not clearly defined in of white/cream pelagic limestones and black/grey the measured sections due to lack of exposure of marls/shales occur above and below the black shale geometrical relationship of the beds in the study areas, interval of the So¤ukçam Limestone. An Upper Aptian and dominance of pelagic successions of the drowned black shale/mudstone (ranging from dark grey [N3] to margin. However, in the Mudurnu section (Figures 15), a black [N1]) interval is also recognized just above the fining-upward trend occurs within the sandstones Upper Aptian red-bed succession within the Üzümlü superjacent to the sequence boundary associated with Member in the Göynük area (De¤irmenözü section) conglomerates (Figure 15, samples between 125 and (Figure 6). 160). This may be interpreted as the short record of low The Upper Albian black shale/mudstone (ranging from stand condition related to a drop (cf. Catuneanu 2006), dark grey [N3] to black [N1]) interval is recognized in the and abruptly followed by transgressive system tracts. In Mudurnu (Figure 8) and Göynük areas within the Üzümlü the ‹smailler section (Figure 16), it is not possible to Member of the Yenipazar Fomation. The black shale differentiate low-stand deposits, therefore one may infer interval is intercalated in a unit composed of purple, that the site was located in a more distal position within medium- to thick-bedded, parallel-laminated sandstones the basin, or that tectonic subsidence was enough to that include belemnite and siliciclastic with feldspars and destroy the signals of low stand system tracts and amplify lithic fragments (Figure 10c). The lower boundary the signal of transgressive system tracts. between sandstones and shales is sharp and sandstones in this interval do not display intense bioturbation as compared to sandstones at higher stratigraphic intervals. The Black Shales/Mudstones The black shale (ranging from dark grey [N3] to black [N1]) interval of the Late Cenomanian and around the The biostratigraphic framework of the black Cenomanian/Turonian boundary is recognized within the shales/mudstones is constructed by using planktonic upper part of the Üzümlü Member of the Yenipazar foraminifera zonation (De Graciansky et al. 1998). The Formation and well exposed in the Mudurnu (Figure 8) Early Cretaceous comprises four distinct levels of black and Göynük (Figure 12) sections. These black shales shales/mudstones in the studied sections. Two are overlie the turbiditic successions composed of alternating recognized in the Early and Late Aptian within the upper grey (between dark grey [N3] and medium dark grey part of the G. blowi – and lower part of the L. cabri and [N4]) sandstone and marl/shale, and are overlain by a G. algerianus-P. cheniourensis zones, respectively. The succession of interbedded white-cream (between white other two are recognized in the Late Albian within the B. [N9], very light grey [N8] and yellowish grey [5Y 8/1]) breggiensis chronozone, and the Late Cenomanian within pelagic limestone rich in Radiolaria and planktonic the zone of R. cushmani (Morrow) zone (Figure 3). foraminifera, and grey marl/shale of the same member.

Lithostratigraphy Sedimentology Black shales/mudstones occur in the Lower Cretaceous The Lower Aptian black shales/mudstones are about 10 m within the So¤ukçam Limestone and within the lower and thick and have been recorded in two of the studied upper part of the Üzümlü Member of the Yenipazar sections: the Mudurnu (Mudurnu area) and Sünnetgölü Fomation (Figure 3). The Lower Aptian black shales (Figures 9 & 11g) sections in this study. Yılmaz et al. (ranging from dark grey [N3] to black [N1]) are (2004a) recorded the ‘Selli’ level, OAE 1a in the Mudurnu recognized in the Göynük (Sünnetgölü sections) (Figure and the Nallıhan areas, where the event occurs in the 9) and Mudurnu (Mudurnu-2 section) (Figure 8) areas. same black shale in a coeval biozone. Hence, they can be Yılmaz et al. (2004a) previously recognized the Lower correlated over a distance of about 100 km from Nallıhan Aptian black shale in the Nallıhan and Mudurnu areas, to Göynük. Moreover, there is no considerable change in within the same biozone as in the So¤ukçam Limestone. the facies of the black shales between these areas. In this study, a second section has been measured in the

286 ‹.Ö. YILMAZ

Black shales occuring within the lower part of the belemnites. The triple appearance of black shales within succession show no clear evidence of bioturbation, and the sandstones in this interval presents an important some are well laminated (Figure 11g). However, some marker level within the R. breggiensis chronozone. The bioturbation appears in the black shales in the upper part dark grey/black shales also include some quartz silt/sand, of the successions. Silty and/or sandy black shale facies and some plant fragments. The presence of pyritized are recorded throughout the interval (Figure 10e). As radiolaria, disseminated minerals in the matrix carbonate content increases upward in the succession, the (Figure 10), and abrupt decrease in planktonic colour changes from black to grey, between dark grey foraminifera concurrent with an increase in organic (N3) and medium dark grey (N4); and pale grey, between matter in the black shale beds are corroborative evidence medium dark grey (N4) and medium bluish grey (5B 5/1). of anoxic conditions during deposition. The lower and upper black shales include pyritized A black shale zone of about 20 m thick occurs in the radiolarian, and some planktonic foraminifera show iron Late Cenomanian of the Mudurnu area (Figure 8). It is coatings around the chambers (Figure 10). Yılmaz et al. 13 composed of alternating dark grey-black silty (2004a) detected a positive C isotope excursion within shale/mudstone and grey marl. Around the the same black shale interval in the Nallıhan area. The Cenomanian/Turonian boundary in the Göynük area sedimentological properties of the black shales in the (‹smailler and Göynük-Sünnet sections; Figures 12–14), Nallıhan area are similar to the black shales of the the black shale interval is overlain predominantly by Sünnetgölü and Mudurnu sections, however, in the white-cream bioturbated pelagic limestone with Nallıhan area, an iron enrichment level and an arkosic planktonic foraminifera (Figure 13a, b). Dark grey-black sandstone bed occur just after the dark black shale part shales and marls intercalate with these limestones of the interval. Ammonites are present just before the 13 forming couplets at the base of the interval and decrease positive C excursion level in the same black shale toward the upper part where limestones dominate in the interval. Shales and marls varying in colour between dark section. This succession is overlain by a yellow-reddish grey (N3) and medium dark grey (N4); and pale grey, cherty interval. Red marls/shales overlie this cherty between medium dark grey (N4) and medium bluish grey interval (Figure 13). (5B 5/1), overlie or alternate with the dark black shale forming couplets within the black shale interval in the Nallıhan section. Sequence Stratigraphy and Cyclostratigraphy All black shale intervals, intergrade with the overlying Sequence stratigraphy and cyclostratigraphy have been limestone-dominated intervals and the transition is applied with different resolutions in the different marked by the appearance of interbedded limestone and sections, and they are based on petrographic and black shales, which decrease in thickness within statistical methods as explained in previous sections. predominantly carbonate interval. The cyclicity in the Mudurnu and ‹smailler sections The Upper Aptian black/dark grey shale interval is (Figure 15 & 16) is expressed as alternation of recognized within the turbiditic sandstones and marls of sandstones and marls/black shales or limestones and the Üzümlü Member in the Göynük area (De¤irmenözü marls/black shales throughout. section; Figure 6). The basal contact of the turbiditic In the sequence stratigraphic framework, black sandstones with the underlying Upper Aptian red beds is shales/mudstones are interpreted to have been deposited sharp, although there is no evidence of hardground or in the early transgressive systems tracts (Schlanger & Cita unconformity in between. The microfacies of the Upper 1982; Einsele et al. 1991; Tyson & Pearson 1991; Aptian black shale are similar to the ones in the Lower Emery & Myers 1996; Miall 1997; Barrera & Johnson Aptian, and are characterized by the presence of pyritized 1999; Einsele 2001; Coe 2003; Skelton et al. 2003; radiolaria, organic matter and some silt/sand sized Catuneanu 2006) and are all observed before the red quartz. beds. The Lower Aptian black shales are recognized The Upper Albian black shales represent an interval within the transgressive systems tracts of the Nallıhan between purple and medium- to thick-bedded and Mudurnu sections. Their positions within the sandstones, which are bioturbated and include biostratigraphic framework corresponding to the upper

287 CRETACEOUS OCEANIC ANOXIC AND OXIC EVENTS, NW TURKEY

G. blowi/ lower L. cabri zone also concur with the The black shales/mudstones in the Late Cenomanian biochronozones in the global sea-level charts (De or around the Cenomanian/Turonian boundary (Figures Graciansky et al. 1998) and they fit into the main 12, 14 & 16; ‹smailler section) are observed as a zone transgressive phase before the Lower Aptian sea level fall. that includes alternation of thinner bioturbated Yılmaz et al. (2004a) presented the stable isotope (C and limestones/marls with thicker black shales/mudstones. O) curves of the Aptian black shale interval in the Nallıhan This zone is overlain by a limestone-dominated interval section, and discussed as well the sequence stratigraphic with thinner black shale/mudstone intercalations. and cyclostratigraphic implications of the Nallıhan and Changes in thickness of cycles along the sections, as well Mudurnu sections. They indicated that the position of the as changes in the position of carbonate or shale- black shale interval corresponds with the transgressive dominated intervals are used to set up sequence systems tracts supported by the evidence from the boundaries/correlative conformities and system tracts in isotope curve, sequence stratigraphy and this type of pelagic setting. Within the sequence cyclostratigraphy. stratigraphic framework, this relationship with The black shale/mudstone intervals in the Upper bioturbated limestones and cyclic alternations further Aptian occur within the turbiditic succession just above indicate that the black shale/mudstone interval took place the Upper Aptian red limestones (De¤irmenözü section; within the early transgressive system tracts. Figures 6 & 11f). Poor exposure of the rest of the When the determined positions of sequence succession in the section does not allow us to define their boundaries and system tracts are correlated with the sequence stratigraphic or cyclostratigraphic positions. global sequence stratigraphy chart of De Graciansky et al. However, because of their relationship with the (1998), they fall within the same biozones, and the underlying red limestone which is suddenly replaced by number of sequences and the position of black shale thin beds of sandstones and black shales, these facies can intervals conform to the same numbers of transgressive be interpreted to represent a sudden increase in intervals in the global chart (Figures 3 & 17). Two accommodation in relation to early transgressive system sequence boundaries have been determined in the B. tracts. This Upper Aptian black shale/mudstone interval breggiensis zone in the Mudurnu section. The positions of has been recorded within the G. algerianus (Cushman and these sequence boundaries and positions of red bed Ten Dam) - P. cheniourensis (Sigal) zones in the De¤irmenözü section. However, Coccioni et al. (2006) interval and black shale/mudstone intervals in this section reported that the Upper Aptian Oceanic was can be correlated with the ones in the global chart recorded around the boundary between G. ferreolensis (Figures 3 & 21). However, due to poor exposures above (Moullade) and G. algerianus (Cushman and Ten Dam) and below the red bed and black shale intervals of the zones as: the Thalmann level in the Calera Limestone of So¤ukçam and the Samsaçavufl sections, these sequence the Franciscan Complex of Northern California; as the boundaries are not determined in these sections. In the Niveau Fallot 3 level of the Vacontian Basin and Mazagon Early Aptian, the correlative conformities of sequence Plateau (DSDP site 545); and as the Renz level in upper boundaries and the levels of black shale/mudstone of the black shale levels of the Fucoidi Formation in . The Sünnetgölü, Mudurnu and Nallıhan sections lie in the slight shift between the zones can be attributed to local same biozones of the global chart (Figures 3, 21 & 22). diachronism in the event or as a biostratigraphic As explained earlier in the sequence stratigraphic calibration problem. The position of the black shale in the concept, Fischer plot curves (Sadler et al. 1993) were global sequence stratigraphic chart can be seen in the prepared for the Mudurnu and ‹smailler sections by using transgressive system tracts. cycle thickness change patterns along the section (Figures The Albian black shales constitute a zone in the 18–20). The sequence boundaries based on change in Mudurnu and Göynük sections characterized by an position of carbonate and shale dominated intervals, and alternation of black shales and purple sandstones (Figures increase or decrease in thickness of carbonates and 8 & 15; Mudurnu section). They are overlain by red marls shales, correspond to the end of the falling limbs of the that precede the sequence boundary represented by curves. Such correlation is indicative of decreased conglomerates. Thus, as stated earlier this zone can be accommodation space, whereas black shales are generally interpreted to fit early transgressive systems tracts. observed in the rising limbs.

288 ‹.Ö. YILMAZ red bed interval black shale Section sequence boundary sequence boundary Mudurnu (2004) ? ? covered Section covered et al. Samsaçavuþ this study ns, with sequence boundaries and ? ? covered covered

Section

WE Soðukçam B. breggiensis B. (2004). (106.2) Gradstein et al. 100.85 102.65 102.12 R. ticinensis B. breggiensis T. praeticinensis T. ‘Global’ R. subticinensis biochronostratigraphy R. ticinensis R. subticinensis T. praeticinensis T. Globotruncanids top of low stand interval planktonic Foraminifera 100.00 R. appenninica maximum transgression/shematic condensed intervals 101.59 (1998) et al. 1998). The age assigned in the brackets is from Gradstein zones Al 9 Al 8 Al 7 Al 10 Tethyan

et al. De Graciansky with Tethyan Ammonite Tethyan with Sequences not callibrated 102.12 100.00 100.53 101.59 sequences minor sequence boundaries medium sequence boundaries major sequence boundaries Al 8 Al 9 Al 6 Al 10 Al 7 sequence chronostratigraphy Al 7 Al 8 Boreal Europe / America North 102.12 100.63 104.82 101.48 100.00 system tracts with global charts (De Graciansky Correlation of sequence boundaries, and occurrences of black shales and red beds in the Mudurnu, Samsaçavufl and So¤ukçam sectio LATE ALBIAN MIDDLE ALBIAN Figure 21. 102.12 (106.2)

289 CRETACEOUS OCEANIC ANOXIC AND OXIC EVENTS, NW TURKEY et al. ? 2004) covered Section Nallýhan (Yýlmaz Section Mudurnu unconformity ? Section covered this study (2004) Sünnetgölü (2004). rnu, and Nallıhan sections, with sequence et al.

et al. ? ? (Yýlmaz 2002) red bed interval black shale sequence boundary covered Section covered Deðirmenözü ? ? covered covered Section Soðukçam WE (121.00) Gradstein 117.37 115.50 114.50 G. ferreolensis G. G. algerianus G. T. bejaouaensis T. P. cheniourensis P. ‘Global’ G. ferreolensis G. G. algerianus G. P. cheniourensis P. L. cabri blowi G. T. bejaouaensis T. T. bejaouaensis T. L. cabri Globotruncanids top of low stand interval 116.48 112.67 L. cabri 116.87 planktonic Foraminifera biochronostratigraphy 118.37 maximum transgression/shematic condensed intervals G. algerianus G. (1998) 1998). The age assigned in the brackets is from Gradstein 115.21

et al. et al. Ap 3 Ap 5 Ap 4 Ap 6 Tethyan De Graciansky 120.00 117.07 112.51 115.90 sequences medium sequence boundaries major sequence boundaries Ap 6 Ap 5 Ap 3 Ap 4 sequence chronostratigraphy Ap 4 Ap 5 Boreal Europe / America North 117.07 120.00 112.57 115.96 Correlation of sequence boundaries, and occurrences of black shales and red beds in the So¤ukçam, De¤irmenözü, Sünnetgölü, Mudu boundaries and system tracts with global charts (De Graciansky LATE EARLY APTIAN APTIAN 117.07 (121.00) 117.07 Figure 22.

290 ‹.Ö. YILMAZ

As stated before, low-stand system tracts are not In the Upper Albian series, silty black shales appear clearly defined in the measured sections. This discrepancy within the purple sandstones in the Mudurnu section. The may be related to lack of exposure of geometrical presence of fine parallel laminae, very rare fauna, relationship of the beds in the study areas, as well as pyritized radiolaria, foraminifera, some plant fragments, predominance of pelagic successions of the drowned and the absence of bioturbation are indicative of margin. anoxic/dysoxic condition (OAE 1c) in this part of the basin. This shale interval is placed within the B. breggiensis chronozone. An Upper Albian black shale Evidence for Global Anoxic and Oxic Events interval is also reported in many parts of the world such The presence of black shales within pelagic/hemipelagic as Italy in Europe (Reyment & Bengtson 1985; Erba successions within nearly the same biostratigraphic zones, 2004). indicates that anoxic or dysoxic conditions developed on The red-purple silty marls/mudstones overlying the the Sakarya Continent. Upper Albian black shales are also in the same biozone in The Aptian ‘Selli’ OAE 1a event is recorded within the the Mudurnu section, they include phosphatic clasts, iron pelagic carbonates of the Nall›han, Mudurnu and Göynük and some glauconite minerals. They display fine parallel areas, or from east to west of the Sakarya Continent over laminae and are partially bioturbated. Identical with a distance of nearly 100 km. The ‘Selli’ event is marls/mudstones are recorded west of the Mudurnu area represented by silty, parallel laminated, and locally by at a distance of 25 km away from the previous section. finely bioturbated, black shales with sparse fauna, This marl/mudstone interval is interpreted as the record pyritized radiolaria and foraminifera. The presence of a of another oxidizing condition that took place following black shale interval within the pelagic limestone this anoxic event in the basin. As implied before, a sudden successions indicates a time interval with sudden change change in the circulation pattern, sea level and nutrient in sedimentation and depositional pattern at the site of availability in the basin may have resulted in such a facies the Sakarya Continental block characterized by a drop in relationship. An Upper Albian red marl/mudstone interval carbonate production and increasing preservation of is also recorded in Italy (Hu et al. 2005b). organic matter. Yılmaz et al. (2004a) showed that the C stable isotope curve of the black shale interval in the In the Late Cenomanian and around the Nallıhan section corresponds with the global C curve Cenomanian/Turonian boundary distinct black shales within the same biostratigraphic interval that includes occur within the R. cushmani zone. The presence of silty, global anoxic events such as those found in Italy (Umbria- finely laminated, black shales with sparse fauna and pyrite Marche Basin; Erba 2004), in the Mediterranean Tethys, minerals punctuates the anoxic conditions during this the North Atlantic, the Central Pacific, and some areas in time interval in this part of the continent. This event is Europe (Reyment & Bengtson1985). coeval with the black shale interval (OAE 2) that has been Succeeding the black shales, carbonate sedimentation reported from several locations worldwide (Coccioni & prevailed in the Upper Aptian, and the presence of red- Galeotti 2003; Coccioni et al. 2006), and especially in pink coloured pelagic limestones/marls with abundant Italy, in the Umbra-Marche basin that is the type section planktonic foraminifera, iron minerals, gastropoda, for the Bonarelli level (Erba 2004). echinoidea and bivalves may indicate an increase in The black shale interval is succeeded in the Early nutrient and oxygenation in the water column. This may Turonian by white pelagic carbonate, which is in turn be due to the change in circulation in relation to tectonic overlain by red-purple marls/mudstones. The presence of movements, or sea level change, or both, that took place abundant planktonic foraminifera and iron minerals in this part of the continent. The switch from Lower within these marls/mudstones indicates that Aptian ‘Selli’ anoxic conditions to Upper Aptian oxidized sedimentation took place under oxidizing conditions. pelagic successions may also be associated with large- Sudden change in facies, increase in the abundance of scale global oceanographic changes. A similar red planktonic foraminifera and iron minerals are interpreted marl/limestone interval is recorded in Italy (Hu et al. as related to the sudden change in circulation pattern, sea 2005b). level or nutrient availability in the basin. The same type of

291 CRETACEOUS OCEANIC ANOXIC AND OXIC EVENTS, NW TURKEY

red marl/mudstone interval is also recorded in Italy whereas black shales accumulated in the subsided and (Rawson et al. 1996). restricted areas in between. The position of the Upper The presence of unaltered silt or fine sand-sized Albian red beds within the sequence stratigraphic feldspar and quartz minerals in the Aptian, Albian and framework is interpreted as the record of late Cenomanian black shales of the areas studied may provide transgressive systems tracts. However, in the Late Aptian further evidence of a relationship between anoxic event and Late Santonian, the red beds are associated with and global volcanic eruptions (Erba 2004; Wignall 2005), Type-3 sequence boundary. The Upper Santonian red as well as the effects of erosion and transportation in beds transgressively overlie the boundary, however the relation to regional tectonic movements. ones in the Upper Aptian are below the boundary and represent late high-stand or still-stand conditions followed by sudden drowning. The Upper Aptian black Conclusions and Interpretations shales were deposited in the nearby trough areas This study presents the analytical results based on surrounding the red beds. The effect of tectonism is sedimentology and stratigraphy of pelagic successions of reflected in the deposition of these different facies within the Mudurnu Trough that includes black shales and red short distances in the basin. A Fischer plot curve (Sadler beds ranging from Early Aptian to Late Santonian. Field et al. 1993) obtained from the cyclostratigraphic analysis and laboratory analyses of facies indicate that black shales of the upper part of the So¤ukçam Limestone and and red beds reveal respective anoxic and oxic conditions. overlying Üzümlü Member displays third-order relative Their occurrences in the Mudurnu Trough of the Sakarya sea level changes. In this curve, it is possible to see Continent (Figure 3) are synchronously recorded with relative fall of sea level followed by sudden rise just over their global counterparts. The black shales recorded in the Aptian red beds of the So¤ukçam Limestone at the the Early Aptian are the equivalent of OAE 1a ‘Selli’ level. bottom of the Üzümlü Member. This independent method The one in the Late Aptian is recorded only at one locality also reveals red beds associated with the rise of sea level, in this study, and is interpreted as the Upper Aptian and the drowning at the bottom of the Üzümlü Member Oceanic Anoxic Event reported by Coccioni et al. (2006) that follows the sudden rise (Figure 20). Background as the Thalmann level in the Calera Limestone of the tectonic effects can also be inferred as long relative fall Franciscan Complex of Northern California; as the Niveau with gentle slope in the upper part of the So¤ukçam Fallot 3 level of the Vocontian Basin and Mazagon Plateau Limestone. The positions of the Aptian, Albian and (DSDP site 545); or as the Renz level in upper black shale Cenomanian red beds and black shales within the Fischer levels of the Fucoidi Formation in Italy. The black shales plots can also be determined, although the curve includes recorded in the Late Albian are interpreted to correspond tectonic effects. Development of Type-3 sequence to OAE 1c. The black shale levels recorded at the boundary at the bottom of the Üzümlü Member recorded Cenomanian/Turonian boundary are the equivalent of as drowning event can be clearly seen in the Fischer plot OAE2 ‘Bonarelli’ level. All black shale intervals are curve as associated with sudden development of a pelagic interpreted as the record of early transgressive system marine turbiditic basin over the pelagic carbonate tracts within the sequence stratigraphic framework succession (So¤ukçam Limestone) in the Mudurnu region (Figures 17–22). The red beds recorded in the Late (Figure 20). The iron content and red colouring of the Albian that succeeded the black shales are interpreted as red beds are probably related to volcanic or terrestrial the record of oxic conditions switched on after the anoxic source and could have been modified by burial . conditions. However, Lower Aptian red beds are coeval Hydrothermal source for colouring could also be possible, with the Lower Aptian black shale at one location in but other hydrothermal minerals, structures and Turkey. These red beds are interpreted to be related to alteration zones are not recorded in association with the local tectonic movements in the basin that created horst red beds. and graben-like structures controlling the deposition of Moreover, consistent positioning of red beds at reddish beds on elevated structures within the basin, certain levels is more compatible with sediment dynamics

292 ‹.Ö. YILMAZ

and sea level changes and not related to hydrothermal ÇAYDAG-104Y010, Ankara, Turkey) and the Middle East events. Further corroborative evidence is given by the Technical University (Ankara, Turkey). I am very thankful fact that the red bed levels observed occur in the same to Demir Altıner for his identifications of planktonic biochronozones as red beds in other parts of the world. foraminifera along the measured stratigraphic sections and helpful discussions. I am also grateful to two anonymous reviewers for their constructive comments. Acknowledgments Darrel Maddy edited the English of the final text. This work was supported by the Turkish Scientific and Technological Research Council (TÜB‹TAK, Project No:

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Received 12 July 2006; revised typescript received 07 August 2007; accepted 09 October 2007

295 CRETACEOUS OCEANIC ANOXIC AND OXIC EVENTS, NW TURKEY

APPENDIX

Symbols used in the detailed measured sections

purple to pinkish coloured pink coloured pelagic limestone calcareous pebbly sandstone

white to ream coloured pelagic light brownish coloured limestone polygenic

dark grey to brownish coloured sandy pelagic dark grey coloured polygenic limestone conglomerate

light grey coloured dark grey to khaki coloured sandy/silty pelagic marl/mudstone limestone

grey to bluish coloured grey coloured pelagic marl/mudstone limestone

red to pink coloured marl/mudstone pink coloured pelagic limestone with ‘Neptunian dyke’-like penetration and nodular structures purple to brownish coloured bioturbated marl/mudstone purple to pink coloured calcareous sandstones with parallel laminations black shale/mudstone

purple coloured sandy limestone with abundant bivalve and belemnites light grey to greenish coloured marl/mudstone

grey coloured bioturbated calcareous red to pink coloured sandstone with plant fragments and pelagic marls parallel laminations

white to cream coloured bioturbated orange to brownish pelagic limestone with planktonic coloured cherts foraminifera and radiolaria

plant fragments light grey coloured marls

cross lamination

296