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Kilop Cretaceous Hardground (Kale, Gümüshane, NE Turkey):description and origin
Journal of Asian Earth Sciences 20 (2002) 433±448
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Kilop Cretaceous Hardground (Kale, GuÈmuÈshane, NE Turkey):description and origin Muhsin Eren*, Kemal Tasli È niversitesi MuÈhendislik FakuÈltesi, Jeoloji MuÈhendislik BoÈluÈmuÈ 33342 CËiftlikkoÈy, Turkey Mersin U Received 12 March 2001; accepted 15 March 2001
Abstract A hardground surface is well exposed in the Kilop area of Kale (GuÈmuÈshane, NE Turkey) which forms part of the Eastern Pontides. Here, the hardground is underlain by shallow water Lower Cretaceous limestones, and overlain by Upper Cretaceous red limestones/marls which contains a planktonic microfauna including Globotruncanidae. In the ®eld, the recognition of the hardground is based on the presence of extensive burrows (especially vertical burrows), the encrusting rudistid bivalve Requienia, neptunian-dykes with in®lls of pelagic sediments and synsedimentary faults. Skolithos and Thalassinoides-type burrows are present. Some burrow walls show iron hydroxide-staining. The extensive burrowing occurred prior to lithi®cation. On the other hand, the neptunian-dykes and synsedimentary faults, which cut the hard ground, occurred after the lithi®cation. These features indicate the progressive hardening of the substrate. The burrowed limestone consists of an intrabioclastic peloidal grainstone which was deposited in an intertidal to shallow, subtidal, moderate to relatively high energy environment. The peloidal limestone shows little or no evidence of submarine cementation, characterized by only scarce relics of isopachous cement rims of bladed calcite spar. The grainstone cement is composed predominantly of blocky calcite and overgrowth calcite cements on the echinoid-fragments. The origin of this cement is controversial. Biostratigraphic analysis of the limestones demonstrates that there is a marked stratigraphic gap (hiatus), spanning the Aptian to the Santonian, in the Cretaceous of the Kilop area. The formation of the Kilop Hardground is related to the break-up and subsidence of the Eastern Pontides carbonate platform during the formation of the Black Sea backarc basin. Hardground development was initiated in a shallow marine environment of slow sedimentation and with moderate to high energy indicating slow subsidence. Later, the hardground subsided abruptly, as shown by the deposition of pelagic sediments on the hardground surface. During drowning, the Kilop area was converted to a bypass-margin where currents were effective. The formation of the hardground may also have been associated with an eustatic rise in sea-level. q 2002 Elsevier Science Ltd. All rights reserved. Keywords: Hardground; Sedimentology; Stratigraphy; Diagenesis; Cretaceous
1. Introduction Hardgrounds are surfaces of synsedimentary lithi®cation and represent a break in sedimentation (Shinn, 1969; Bromley, 1975; Kennedy and Garrison, 1975; Bathurst, 1975; Tucker, 1991; Wilson and Palmer, 1992). These surfaces may be recognized by the presence of abrasion, encrustations and borings and may cut across fossils and sedimentary structures. Some hardgrounds develop from loose sediments, through ®rmgrounds, to lithi®ed layers, and indicate a progressive hardening which is characterized by a change in the fauna, particularly the burrowing organisms, and by sedimentary features (Tucker, 1991; FuÈrsich et al., * Corresponding author. E-mail address: [email protected] (M. Eren).
1981). Some hardgrounds are mineralized, with iron hydroxides (goethite-limonite), and glauconite and phosphorite impregnating the sediment, burrow walls and fossils, and occurring as discrete grains (Tucker and Wright, 1990). Both intense submarine cementation and borings and/or burrowing indicate slow sedimentation in the depositional environment (Shinn, 1969; Tucker and Wright, 1990; Macintyre, 1977; James and Ginsburg, 1979). In the recognition of hardgrounds, geologists face two main problems. The ®rst problem is hardground identi®cation. The second problem is the recognition of the diagenetic environment in which lithi®cation took place Ð either submarine or subaerial (Bathurst, 1975). Research on hardground recognition has been published by Shinn (1969), Purser (1969), Kennedy and Garrison (1975), Garrison et al. (1987), Marshall and Ashton
1367-9120/02/$ - see front matter q 2002 Elsevier Science Ltd. All rights reserved. PII: S 1367-912 0(01)00027-X
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È zsayar et al., 1981) and location of the study area. (1) Kilop section, (2) KecËidere section, (3) CËukutbasi Fig. 1. Schematic map showing the Eastern Pontides (O Tepe section.
(1980), Goldring and Kazmierczak (1974), Dravis (1979) and Brett and Brook®eld (1984). This paper aims to introduce the Kilop Hardground as a Cretaceous example, and to investigate its origin. Chronostratigraphic interpretation of the carbonate platform sequences underlying the Kilop Hardground has been made using benthic foraminifers and calcareous algae. Sequences representing the facies of the drowning È zsayar (1997). platform were studied by Tasli and O 2. Kilop Cretaceous hardground The hardground surface is well exposed in the Kilop area of Kale (GuÈmuÈshane, NE Turkey), a small town located on the road between GuÈmuÈshane and Bayburt (Fig. 1). Here the hardground caps a burrowed peloidal limestone (grainstone) of the Berdiga Formation, covering an area of 0.5 km 2. The Berdiga Formation is made up of platform carbonates of Late Jurassic to Early Cretaceous age (Eren, 1983; Tasli, 1991). In the ®eld, the Kilop Hardground is overlain, apparently conformably, by the Kermutdere Formation, which consists mainly of Upper Cretaceous turbiditic sequences
(Tokel, 1972). The basal unit of the Kermutdere Formation, immediately overlying the hardground surface, is a red argillaceous limestone/marl which contains a planktonic microfauna, such as Globotruncanidae (Fig. 2A). This condensed sequence occurs as a thin, but continuous stratigraphic level in the Eastern Pontides, and plays a fundamental role in stratigraphic correlation, both regionally and globally. This unit passes upward into the turbiditic facies which is made up of an alternation of thin-bedded marl, pelagic biomicrite and sandstone. In the ®eld, the hardground surface is characterized by extensive burrowing (Fig. 2B and C) with large encrusting sessile organisms, such as the rudistid bivalve Requienia (Fig. 2D) that required a ®rm or hard substrate on which to live. Two types of burrows are present. The ®rst are simple vertical tubes of Skolithos Ð type burrows (Fig. 2B). Their cross-sections are circular having an average diameter of 1 cm. Some of them demonstrate concentric zonations, with a central nucleus, with a yellow stained burrow wall, surrounded by a halo affecting the zone of bioturbation. The second type of burrow forms anastomosing networks of selectively silici®ed Thalassinoides(?) burrows (Fig. 2C).
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Fig. 2. Field photographs of the Kilop Cretaceous hardground. (A) A ®eld photograph of the Kilop hardground surface (H) which is apparently conformably overlain by the red argillaceous limestone/marl (R), and later by turbiditic sediments (T). (B) Plan view of Skolithos-type trace fossils. Most burrow walls have yellow ferruginous staining (arrow). (C) Plan view of Thalassinoides(?)-type trace fossils (arrows) selectively silici®ed and showing branching. (D) Body fossils of Requenia sp. (arrows) encrusting the hardground surface. (E) A neptunian-dyke with in®ll of red pelagic limestone (arrow). (F) A syn-sedimentary fault (arrow) associated with the hardground surface. C: Platform carbonate, R: red argillaceous limestone/marl.
These burrow systems consists of horizontal branching burrows with an average diameter of 1 cm. The burrows show up as brownish mottling on the hardground surface (Fig. 2C). Furthermore, the hardground surface is cut by several neptunian dykes, with in®lls of red pelagic limestone (Fig. 2E), showing similar features to the overlying red beds, and by a syn-sedimentary fault (Fig. 2F). The
strike of the neptunian dykes and the fault plane is approximately N±S. Microscopic studies show that the burrowed limestone consists mainly of peloidal grainstone (Fig. 3A). In addition to peloids, other constituents are echinoderm debris, benthic foraminifers and intraclasts. Some relics of matrix are present locally. Primary pores are ®lled
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predominantly by blocky calcite cement (Fig. 3A) and syntaxial overgrowth cements on the echinodermfragments (Fig. 3B). Very locally relic-textures of isopachous marine cement rims of bladed spar can also be seen (Fig. 3C). 3. Regional and tectonic settings The GuÈmuÈshane region, in which the Kilop Harground occurs, is a part of the Eastern Pontides (Fig. 1), extending in E±W direction along the southern shore of the Eastern Black Sea. The geotectonic evolution of the Eastern Pontides is still debated. According to Sengor et al. (1984), it forms the eastern part of the Rhodope-Pontid Fragment. It is generally accepted that the RhodopePontid fragment lies entirely to the north of the Neo-Tethyan oceanic sutures and therefore formed the northern margin of the Jurassic±Cretaceous Neo-Tethys (e.g. Sengor and Yilmaz, 1981; Sengor et al., 1984; Sengor, 1984; Robertson and Dixon, 1984). The main points of contention focus on the palaeo-subduction direction, whether to the north beneath Eurasia, or to the south beneath Gondwana. Sengor and Yilmaz (1981) suggest that the Neo-Tethys was consumed from the Early Jurassic to middle Eocene by northward-directed subduction (Fig. 4A). In this view the Black Sea represents the remnant of a back-arc basin which opened to the north of the Eastern Pontides during the Late Cretaceous. However, Dewey et al. (1973) and Bektas et al. (1984) suggest that the Eastern Pontides were attached to a segment of the Neo-Tethys which was subducted towards the south. In this model the Black Sea represents a remnant of the Palaeo-Tethys Ocean. The GuÈmuÈshane region, including the site of the Kilop Hardground is situated on the northern margin of the Rhodope-Pontid Fragment facing onto the Black Sea (Fig. 4A). The Jurassic±Lower Cretaceous carbonate platform of the GuÈmuÈshane region was broken up by extensional tectonic movements during Albian-Santonian time (Albian in Yilmaz, 1997). This conclusion has been con®rmed by Bektas et al. (1995) for the Eastern Pontides, and by GoÈruÈr et al. (1993) for the Western Pontides, with a slight time difference. This rifting is considered to be related to opening of a back-arc basin (Sengor and Yilmaz, 1981; Sengor 1984; Bektas et al., 1984). However, Gedik et al. (1996) explain the rifting as the result of subduction and shear tectonics. The Berdiga Formation (platform carbonates) and the Kermutdere Formation (turbidites) in the GuÈmuÈshane region record and transition from platform to lower slope and basinal settings, respectively. In this region tectonic drowning of the carbonate platform resulted in the formation of paleo-rises and depression areas; hardgrounds, such as the Kilop Hardground, characterize local environments within this depositional setting (Fig. 4B).
Fig. 3. (A) Photomicrograph of burrowed limestone consisting of peloidal grainstone showing sparry calcite cement in intergranular pores. Dark grains are peloids (arrows). (B) Syn-taxial overgrowth calcite cement (c) on an echinoderm-fragment (e). (C) A relic of isopachous marine cement rim of bladed spars (arrow). p: peloid.
4. Biostratigraphy and environmental setting of the Cretaceous sequences In the GuÈmuÈshane area, Upper Jurassic±Lower Cretaceous platform carbonates have been correlated with the Berdiga Formation ®rst described by Pelin (1977) from the Alucra (Giresun) area. The Upper Cretaceous
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Fig. 4. (A) A geotectonic cross-section, showing the main features of the Eastern Pontides, modi®ed from Sengor and Yilmaz (1981). (B) A depositional model for the Upper Cretaceous sediments in the Kale area (GuÈmuÈshane) and the hardground location.
conglomerates, calcarenites (Fig. 7, unit E), red pelagic limestones (Fig. 7, unit F) and siliciclastic turbidites have been named the Kermutdere Formation (Tokel, 1972). Albo-Cenomanian to Turonian-Coniacian outer shelf to slope carbonates (Fig. 8, units C and D) were ®rst described È zsayar (1997), but have not been named. by Tasli and O Detailed microfacies analysis of three different measured sections, from Kilop and adjacent areas, permits recognition of ®ve informal lithostratigraphic units within the Cretaceous carbonate sequence. The same symbols are used for the same units in different section localities. The stratigraphic distribution of microfossils in the sections is illustrated in Figs. 5±7. Biostratigraphic control is provided by benthic and planktic foraminifers identi®ed from thin sections. The descriptions are given from bottom to top of the sections. Unit A, which terminates with the hardground surface in the Kilop area, is represented by medium- to thick-bedded gray limestones and subordinate dolomitic limestones in the lower part. It consists mainly of intraclastic, peloidal grainstones and packstones with benthic foraminifers and calcareous algae. Stromatolitic algal laminations with fenestral fabric alternate with the aforementioned grain/packstones, and contain oligotypic microfauna composed of ostracoda and Miliolidae. The lower part of Unit A corresponds to an assemblage of benthic foraminifers known from the Berriasian-Valanginian interval (Arnaud-Vanneau and Darsac, 1984). The following benthic foraminifers have been identi®ed: Pseudotextulariella salevensis CHAROLLAIS, BRONNIMAN and ZANINETTI (Fig. 10D1, D2), Haplophragmoides sp. (Fig. 9C1, C2), Trocholina sp. A3 DARSAC (Fig. 10H1,
H2), Trocholina elongata (LEUPOLD and BIGLER) (Fig. 10F), Trocholina cf. alpina (LEUPOLD and BIGLER) (Fig. 10G), Barkerina cf. barkerensis FRIZZEL and SCHWARTZ (Fig. 9A1, A2), Pseudocyclammina lituus (YOKOYAMA) (Fig. 10D), Arenobulimina sp. (Fig. 10E1, E2), Charentia nana ARNAUD-VANNEAU, Miliolidae and Textulariidae. Calcareous algae are represented by Salpingoporella annulata CAROZZI (Fig.11B), Actinoporella sp., Acicularia/Terquemella (Fig. 11H), Bakalovaella sp., Thaumatoporella parvovesiculifera (RAINERI) (Fig. 11I). In the overlying biozone, some of the aforementioned benthic foraminifers are completely missing and some new forms appear; Pseudolituonella gavonensis FOURY (Fig. 10B), Everticyclammina sp. (Fig. 9F), Pseudotextulariella sp., Praechrysalidina sp. (Fig. 10A1, A2), Vercorsella cf. laurentii (SARTONI and CRESCENTI) (Fig. 10 C1, C2), Everticyclammina hedbergi (MAYNC) (Fig. 9F), Haplophragmoides sp., Bolivinopsis spp. (Fig. 9H, I). Calcareous algae are sporadically abundant; Actinoporella nigra (CONRAD and PEYBERNES) (Fig. 11G), Bakalovaella cf. elitzae (BAKOLOVA) (Fig. 11D1, D2), Salpingoporella annulata CAROZZI, Salpingoporella hispanica CONRAD and GRABNER (Fig. 11E), Cylindroporella sp. (Fig. 11C), Acicularial/Terquemella, Clypeina sp. (Fig. 11F), Bacinella irregularis RADOICIC, Thaumatoporella parvovesiculifera (RAINERI), Solenopora sp. In the Mediterranean realm, this association ranges from the Hauterivian to Aptian. Salpingoporella hispanica is known from the Barremian in Italy (Chiocchini et al., 1979; Sokac, 1996) and from Barremian-Bedoulian in
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Fig. 5. Kilop stratigraphic section showing distribution of foraminifers and calcareous algae used for biostratigraphic subdivision, and also biogenic constitutents, textures and rock units.
Hungary (PeyberneÁs and Conrad, 1979). Concerning the benthic foraminifers, Vercorsella laurentii occurs in the Aptian of Italy (Chiocchini et al., 1984) and in the Barremian-lower Aptian of NE Turkey (Kirmaci et al., 1996). Sedimentary structures (algal laminations, fenestral fabric) and the microfossil content of unit A indicate an intertidal to very shallow subtidal depositional environment. Unit B marks a change of depositional pattern. It consists of monotonous cherty micrites with bryozoa, sponge and fossil fragments, such as echinoderm, pelecypoda and ostracoda, which are partly silici®ed. There are also
typical foraminifers of the outer platform environment, such as lenticulina sp., Spirillinidae and very rare Globuligerina sp. (Protoglobigerina). The depositional environment gradually evolved into a deeper shelf sea with open circulation, thus the pre-existing biota and facies was completely drowned. A probable Aptian-Albian age is suggested here for unit B, because it rests conformably on unit A of Hauterivian to Aptian age. The upper boundary of unit B could not be observed in the sections, therefore this portion of the Cretaceous sequence was not sampled.
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Fig. 6. KecËidere stratigraphic section showing distribution of foraminifers and calcareous algae used for biostratigraphic subdivision, and furthermore biogenic allochems, textures and rock units.
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Fig. 7. CËukutbasy stratigrapic section showing distribution of calcispheres and planktonic foraminifers used for biostratigraphic subdivision, and also biogenic È zsayar, 1997). allochems, textures and rock units (Tasli and O
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Fig. 8. Lithostratigraphic correlation of the three measured sections from the Kale area showing the presence of a stratigraphic gap within the Kilop section. The stratigraphic gap spans the period from Aptian to Santonian.
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Unit C is represented by thick- to very thick-bedded cherty limestones, composed of interbedded wackestones and intraclastic peloidal grainstones, with small benthic foraminifers (Fig. 11N), such as Gaudryina sp., Glomospira sp., Bolivinopsis sp., Lenticulina sp., small Valvulinidae and Textulariidae. The wackestones contain siliceous sponge spicules (Fig. 11M), subordinate echinoderm debris, bryozoa, ostracoda and extremely rare Calcisphaerula innominata BONET. Some beds are comprised of up 10 percent of silt-sized quartz grains. The presence of small benthic foraminiferal assemblage, and biomicrite with sponge spicules, indicates that the depositional environment was outer shelf, nearby upper slope. Signi®cant biomarkers are lacking. Units C is conformably overlain by Turonian-Coniacian limestone (unit D). Thus it is tentatively ascribed to the Upper Albian-Cenomanian. According to Adams et al. (1967) (in Andri, 1972, small-sized and thick-walled forms of Calcisphaerula innominata predominate in the Upper Albian-Cenomanian. Unit D is made of by thin- to thick-bedded, bioturbated argillaceous limestones with thin layers of shale/marl. It is sporadically interrupted by graded and very thick-bedded calcarenites. The contact with the underlying unit is even and sharp. The argillaceous limestones are composed of wackestones with abundant calcispheres and planktonic foraminifers; Calciphaerula innominata BONET, Pithonella ovalis KAUFMANN, Marginotruncana coronata (BOLLI) / pseudolinneiana PESSAGNO, Whitinella/ Hedbergella, Heterohelicidae, Planomalinidae. This assemblage indicates an age span from Turonian to Santonian (Caron, 1985). Organisms and sedimentary structures (slumpings and nodular beds) indicate a slope depositional environment. The calcarenitic intercalations are interpreted as a transported shelf materials, because of their close association with the surrounding pelagic wackestones. Limestones occupying the same stratigraphic position and with the same facies are also present in Ikisu (east of GuÈmuÈshÈ zsayar, 1997). ane) (Tasli and O Unit D is overlain unconformably by Unit E, which consists mainly of monomictic conglomerates with intercalactions and lenses of calcarenite, siltstone and red mudstone. Clasts are mainly limestone, subordinate chert and volcanic rock. The conglomerates pass upwards through a thick gastropoda (Nerinea and Actaeonella) biostrome and a bioclastic limestone bed into red argillaceous limestones/
marls (Unit F). The red limestones are composed of wackestones with planktonic foraminifers and rare radiolaria. The basal beds of unit E contain an assemblage comprising Dicarinella concavata (BROTZEN) (Fig. 11L) which is indicative of a latest Coniacian-Santonian age (Caron, 1985), while the upper part contains Globotruncanita elevata (BROTZEN) (Fig. 11J), characteristic of the Campanian. Unit F has a great lateral extent with a remarkably uniform lithology, forming a lithostraphic marker horizon in the Eastern Pontides. It is overlain by siliciclastic turbidites, composed mainly of a marl±shale±sandstone alternation. Fig. 8 shows the correlation of three measured sections, showing the stratigraphic position of the hardground and the absence of units B, C and D in the Kilop pro®le. 5. Hardground origin Extensive burrows (especially vertical burrows), encrusting organisms and very rare marine cement relics are characteristics of the Kilop Hardground, and indicate slow sedimentation (Wilson, 1975; Pienkowski, 1985; Shinn, 1969). Dwelling traces of suspension feeders, such as Skolithos and Thalassinoides (?) indicate a soft substrate (Frey and Pemberton, 1984; FuÈrsich et al., 1981). Thalassinoides commonly forms a burrow-system below many hardgrounds (Bromley, 1967, 1975; Goldring and Kazmierczak, 1974; Palmer, 1978; Brown and Farrow, 1978). Burrowing may have been intense before lithi®cation, as the sedimentation rate slowed down. Furthermore, the presence of neptunian dykes and a synsedimentary fault suggests a hard substrate, rather that a soft substrate, at that time (Winterer and Sarti, 1994; James and Choquette, 1983). All these features indicate progressive hardening of the substrate with time. The burrowed peloidal grainstone does not show any clear evidence of marine cementation, except for some relics of an isopachous marine cement rim with bladed spars. The grainstone has a predominantly blocky calcite cement with syntaxial overgrowth on echinoid fragments. The origin of these cements is controversial. Both blocky calcite and syntaxial overgrowth cements are known to be precipitated from supersaturated meteoric water in either the phreatic or vadose zones. However, several authors have
Fig. 9. Benthic foraminifers from the Early Cretaceous of the Kale (GuÈmuÈshane) area (northeastern Turkey). (A) Barkerina cf. barkerensis FRIZZEL and SCHWARTZ. This form is very similar to the type species of the genus Barkerina described originally from Texas Albian (Frizzell and Schwartz, 1950; in Hamaoui, 1973) and it is restricted to upper part of the Pseudotextulariella salevensis cenozone (upper Valanginian) in the GuÈmuÈshane region (Tasli, 1991). (A1) Equatorial section, sample GL 61-3, A2. Subaxial section, sample GL 61-1. (B) Charentia cuvillieri NEUMANN. (B1) Equatorial±longitudinal section showing a marked uniserial stage, sample GL 127-6, B2. Oblique equatorial±longitudinal section showing the single, simple aperture in the uniserial stage, sample GL 127-5, (B3) Equatorial section, sample GL 127-7, B4. Axial section, sample GL 127-4.(C) Haplophragmoides sp. (C1) Axial section, sample GL 130, (C2) Equatorial section, sample GL 109. (D) Pseudocyclammina lituus (YOKOYAMA). Subaxial section, sample GL 57-3. (E) Pseudochoffatella sp. (E1) Equatorial section, sample GL 57-2, (E2) Subaxial section (form B), sample GL 57-1. (F) Everticyclammina sp. Subequatorial±longitudinal section, sample GL 68-6. (G) Everticyclammina hedbergi (MAYNC). Subaxial section, sample HUR 103. (H) Bolivinopsis sp. (B) Equatorial±vertical section, sample GL 103-2. (I) Bolivinopsis sp. (A) Equatorial±vertical section, sample GL 76-2. Bar scales: 0.25 mm.
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suggested a marine origin for these cements when associated with hardgrounds (Wilkinson et al., 1982; Wilkinson et al., 1985; Garrison et al., 1987; Kim and Lee, 1996). Meyers (1974) and Lohmann and Meyers (1977) also report that precipitation of syntaxial overgrowth of Mg-calcite cement in a shallow marine environment is a common phenomenon. No evidence exists for the emergence of the sea ¯oor. So we interpret the early diagenetic lithi®cation as having occurred in a submarine environment, based on the truncation of body fossils (Fig. 2D), the presence of neptunian dykes, with pelagic sediment in®lls, a syn-sedimentary fault and an abrupt change from shallow marine to relatively deep marine conditions. In general, vertical burrows such as Skolithos-type dominate where high-energy conditions keep sur®cial sediments mobile, whereas horizontal burrows dominate where energy conditions are low and nutrients are abundant within the substrate. Therefore, the trace fossil assemblages of the Kilop area are indicative of intertidal to shallow subtidal environments and moderate to high energy conditions (Pienkowski, 1985; Pemberton et al., 1990; Frey and Pemberton, 1984). Microfacial analysis of unit A, which terminates with a hardground surface in the Kilop area, provides supportive evidence for a similar depositional environment. Comparison of three measured stratigraphic sections from Kilop and adjacent areas reveals that the kilop pro®le lacks the uppermost part of Berdiga Formation and some basal units of Kermutdere Formation, such as the conglomerate (Fig. 8). During non-deposition or slow sedimentation in the Kilop area, carbonate sedimentation continued in the adjacent areas, including the resedimentation of materials such as calcarenite and calcilutite, from uplifted areas of the carbonate platform. Resedimented materials suggest erosional process and the effects of currents on the surrounding areas. Features mentioned above suggest that the Kilop Hardground probably formed on a bypass margin which was the site of carbonate deposition; its development representing a cessation of sedimentation. Hardground formation almost invariably coincides with a marked lithological change from shallow marine platform carbonates below, to probably considerably deeper marine red argillaceous limestone/marl with a planktonic microfauna, above. This surface, therefore, separates regressive carbonates and transgressive deeper red pelagic argillaceous limestone/marls. The stages in the drowning of the carbonate platform are represented by the sediments missing from
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the Kilop pro®le, including units B, C and D. This vertical transition marks a drastic change in tectonic conditions, which resulted in sudden deepening of the carbonate platform by vertical movements. Transgression may have been associated with these vertical movements. During the Upper Cretaceous the Eastern Pontide carbonate platform was broken up at a progressively increasing rate, and was converted into a narrow and long deep marine trough trending in a ENE±WSW direction. Turbiditic sediments of Upper Cretaceous age were deposited in this trough. The break-up of the carbonate platform resulted a long stratigraphic gap spanning an interval from Aptian to Santonian. If we consider the progressive deepening of the environment, we may say that submarine lithi®cation began in a shallow environment. Shinn (1969) has noted that submarine lithi®cation is especially active in water depths of around 20 m. The formation of the neptunian-dykes and the syn-sedimentary fault took place in a deeper environment, where red argillaceous limestone/marl could accumulate. 6. Conclusions An ancient hardground surface is exposed in the Kilop area, characterized by extensive burrows, large encrusting organisms and scarce relics of submarine rim cement. Neptunian dykes and a syn-sedimentary fault with regular boundary indicate that the substrate was well lithi®ed prior to the deposition of the overlying deeper marine argillaceous sediments which also in®ll the sedimentary dykes. The hardground occurs at the top of the regressive sequences of the Berdiga Formation, where it presents a marked stratigraphic gap (hiatus) which spanning the Aptian to Santonian. The hardground formation is related to breaking up of the Eastern Pontides carbonate platform, and may also be associated with an eustatic rise of sea-level. This break-up was probably associated with the development of a back-arc basin. Acknowledgements The authors are indebted to Prof. Alastair Robertson and Dr Mark Wilson for their constructive comments on an earlier version of the paper, and to Dr A.J. Barber for improvements to the English.
Fig. 10. Benthic foraminifers from the Early Cretaceous of the Kale (GuÈmuÈshane) area (northeastern Turkey). (A) Praechrysalidina sp. A1. Subaxial section, sample HUR 92, A 2. Transverse section, sample HUR 80. (B) Pseudolituonella gavonensis FOURY. Subaxial section, sample GL 76-2. (C) Vercorsella cf. laurentii (SARTONI and CRESCENTI). (C1) Subaxial section, sample GL 109-4. (C2) Transverse-oblique section, sample GL 130-5. (D) Pseudotextulariella È NNIMANN and ZANINETTI. (D1) Parallel section, sample GL 55-3. (D2) Oblique-transverse section passed through the salevensis CHAROLLAIS, BRO aperture, sample GL 51. (E) Arenobulimina sp. (E1) Transverse section, sample GL 89-1. (E2) Oblique-transverse section, sample GL 113-4. (F) Trocholina elongata (LEUPOLD and BIGLER). Axial section, sample HUR 70.G. Trocholina cf. alpina (LEUPOLD and BIGLER) Axial section, sample GL 89-1. (H) Trocholina sp. A3 DARSAC (in Arnaud-Vanneau and Darsac, 1984). (H1) Axial section showing the spheric proloculus (form A), sample HUR 69, H2. Oblique axial section, sample HUR 70. Bar scales: 0.25 mm.
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References Adams, T.D., Khalili, M., Khosrovi Said, A., 1967. Stratigraphic signi®cance of some oligosteginid assemblages from Lurestan Province, northwest Iran. Micropaleontology 13 (1), 55±67. Andri, E., 1972. Mise au point et donneÂes nouvelles sur la famille des Calcisphaerulidae BONET (1956): les genres Bonetocardiella, Pithonella, Calcisphaerula et Stomiosphaera. Revue de MicropaleÂontology 15 (1), 12±34. Arnaud-Vanneau, A., Darsac, C., 1984. CaracteÂres et eÂvolution des peuplements de foraminifeÂres benthiques dans les principaux biotopes des plates-formes carbonateÂes du CreÂtace infeÂrieur des alpes du Nord (France). Geobios, Memoir Special N8 8, 19±23. Bathurst, R.G.C., 1975. Carbonate Sediments and their Diagenesis. Elsevier, Amsterdam p. 338. Bektas, O., Pelin, S., Korkmaz, S., 1984. Mantle uprising in the Eastern Pontide Back-Arc Basin and the concept of a polygenetic ophiolite. Geological Society of Turkey, 38th Scienti®c and Technical Congress, Ihsan Ketin Symposium (in Turkish with English Abstract), Ankara, pp. 175±188. È zguÈr, S., 1995. Cretaceous Bektas, O., Yilmaz, C., Tasli, K., Akdag, K., O rifting of the eastern Pontide carbonate platform (NE Turkey): The formation of carbonate breccias and turbidites as evidence of a drowned platform. Giornale di Geologia 57 (1±2), 233±244. Brett, C.E., Brook®eld, M.E., 1984. Morphology, faunas and genesis of Ordovician hardgrounds from southern Ontario, Canada. Palaeogeography, Palaeoclimatology, Palaeoecology 46, 233±290. Bromley, R.G., 1967. Some observations on burrows of thalassinidean Crustacea in chalk hardgrounds. Quarterly Journal of the Geological Society of London 123, 157±182. Bromley, R.G., 1975. Trace fossils at omission surfaces. In: Frey, R.W. (Ed.). The Study of Trace Fossils. Springer, New York, pp. 399±428. Brown, B.J., Farrow, G.E., 1978. Recent dolomitic concretions of crustacean burrow origin from Loch Sunart, West Coast of Scotland. Journal of Sedimentary Petrology 48 (3), 825±834. Caron, M., 1985. Cretaceous planktic foraminifera. In: Bolli, H., Saunders, J.B., Perch-Nielsen, K. (Eds.). Plankton Stratigraphy. Cambridge Earth Science Series, pp. 17±86. Chiocchini, M., Mancinelli, A., Molinari-Paganelli, V., Tiliari-Zuccari, A., 1979. ReÂpartition stratigraphique des algues dasycladales et codiaceÂes dans les successions MeÂsozoõÈques de plateforme carbonateÂe du Lazio centre-meÂridional (Italie). Bulletin des Centres de Recherches Exploration±Production Elf-Aquitanie 3 (2), 525±535. Chiocchini, M., Mancinelli, A., Romano, A., 1984. Stratigraphic distribution of benthic Foraminifera in the Aptian, Albian and Cenomanian carbonate sequences of Aurunci and Ausoni Mountains (Southern Lazio, Italy). Benthos'83; Second International Symposium on Benthic Foraminifera, pp. 167±181. Dewey, J.F, Pitman, W.C., Ryan, W.B.F., Bonnin, J., 1973. Plate tectonics and the evolution of the Alpine system. Geological Society of America Bulletin 84, 3137±3180. Dravis, J., 1979. Rapid and widespread generation of recent oolitic hardgrounds on a high energy Bahamian Platform, Eleuthera Bank, Bahamas. Journal of Sedimentary Petrology 49, 195±508.
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Eren, M., 1983. Geology and microfacies analysis of the GuÈmuÈshane-Kale area. Unpublished MSc Thesis, Karadeniz Technical University, Trabzon (in Turkish), 197pp. Frey, R.W., Pemberton, S.G., 1984. Trace fossil facies models. In: Walker, R.G. (Ed.). Facies models. 2nd ed. Geoscience Canada Reprint Series 1, pp. 189±207. Frizzell, D.L., Schwartz, E., 1950. A new lituolid foraminiferal genus from the Cretaceous with an emendation of Cribrostomoides Cushman. University of Missouri, Bulletin, Technical Series, 76. FuÈrsich, F.T, Kennedy, W.J., Palmer, T.J., 1981. Trace fossils at a regional discontinuity surface: The Austin/Taylor (Upper Cretaceous) contact in Central Texas. Journal of Paleontology 55, 537±551. Garrison, R.E., Kennedy, W.J., Palmer, T.J., 1987. Early lithi®cation and hardgrounds in Upper Albian and Cenomanian calcarenites, southwest England. Cretaceous Research 8, 103±140. Gedik, I., Kirmaci, M.Z., Capkinoglu, S., Ozer, E., Eren, M., 1996. Geological development of the Eastern Pontides. In: Kormaz, S., Akcay, M. (Eds.), Symposium Proceedings of the 30th Anniversary of the Geological Engineering Department, Karadeniz Teknik Universitesi, Trabzon, pp. 654±677 (in Turkish with English Abstract). Goldring, R., Kazmierczak, J., 1974. Ecological succession in intraformational hardground formation. Paleontology 17, 949±962. GoÈruÈr, N., TuÈysuÈz, O., Akyol, A., SakyncË, M., Yigitbas, E., AkkoÈk, R., 1993. Cretaceous red pelagic carbonates of northern Turkey: their place in the opening history of the Black Sea. Eclogae Geologicae Helvetiae 36 (3), 819±838. Hamaoui, M., 1973. Barkerina et formes voisines (ForaminifeÁres). Bulletin de Centre de Recherches de Pau-SNPA 7 (2), 337±359. James, N.P., Choquette, P.W., 1983. Diagenesis 6. Limestones Ð the sea ¯oor diagenetic environment. Geoscience Canada 10, 162±179. James, N.P., Ginsburg, R.N., 1979. The seaward margin of Belize barrier and atoll reefs. International Association of Sedimentologists, Special Publication 9, 131. Kennedy, W.J., Garrison, R.E., 1975. Morphology and genesis of nodular chalk and hardgrounds in the Upper Cretaceous of southern England. Sedimentology 22, 311±386. Kirmaci, M.Z., Koch, R., Bucur, J.I., 1996. An early Cretaceous section in the Kircaova area (Berdiga Limestone, NE Turkey) and its correlation with platform carbonates in W-Slovenia. Facies 34, 1±22. Kim, J.C., Lee, Y.I., 1996. Marine diagenesis of lower Ordovician carbonate sediments (Dumugol Formation), Korea Ð cementation in a calcite sea. Sedimentary Geology 102, 241±257. Lohmann, K.C, Meyers, W.J., 1977. Microdolomite inclusions in cloudy prismatic calcites Ð a proposed criterion for former high magnesium calcites. Journal of Sedimentary Petrology 47, 1078±1088. Macintyre, I.G., 1977. Distribution of submarine cements in a modern Caribbean fringing reef, Galeta Point, Pananma. Journal of Sedimentary Petrology 47 (2), 503±516. Marshall, J.D., Ashton, M., 1980. Isotopic and trace element evidence for submarine lithi®cation of hardgrounds in the Jurassic of eastern England. Sedimentology 27, 271±289. Meyers, W.J., 1974. Carbonate cement stratigraphy of the Lake Valley formation (Mississippian), Sacramento Mountains, New Mexico. Journal of Sedimentary Petrology 44, 837±861.
Fig. 11. Calcareous algae from the Early Cretaceous platform carbonates (Fig. 10A±I), planktonic foraminifers from the Late Cretaceous pelagic limestones (Fig. 10J±L) and facies types of middle Cretaceous limestones (Fig. 10M, N) in the Kale area. (A) Salpingoporella sp Oblique section, sample GL 76-4. (B) Salpingoporella annulata (CAROZZI). Longitudinal section, sample GL 68-2. (C) Cylindroporella sp. Oblique longitudinal section, sample GL 68. (D) Bakalovaella cf. elitzae (BAKALOVA). (D1) Longitudinal±tangential section, sample GL 68-5, (D2) Oblique section, sample GL 68-1. (E) Salpingoporella hispanica CONRAD and GRABNER. Oblique section, sample GL 73-2. (F) Clypeina sp. Oblique section, sample GL 130-5. (G) Actinoporella nigra (CONRAD and PEYBERNES). Transverse section, sample GL 76-3. (H) Acicularia/Terquemella. Sample GL 127-2. (I) Thaumatoporella parvovesiculifera (RAINERI). Tangential section, sample GL 72. (J) Globotruncanita elevata (BROTZEN). Oblique axial section, sample CËT 34, from upper part of red pelagic limestone (unit F). (K) Marginotruncana pseudolinneiana PESSAGNO. Axial and subaxial sections, sample CËT 20, from gray pelagic limestone (Unit D) of Turonian-Coniacian age. (L) Dicarinella concavata (BROTZEN). Subaxial section, sample CËT 30, from the base of red pelagic limestone (Unit F). (M) Biomicrite with sponge spicules (Unit C). Sample C Ë T 6. (N) Biopelsparite with small benthic foraminifers (Unit C). Sample C Ë T 5. Bar scales: 0.25 mm.
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È zsayar, T., Pelin, S., Gedikoglu, A., 1981. Cretaceous in the Eastern O Pontides. Black Sea Tech. University, Earth Science Bulletin, Geology 1 (2), 65±114. Palmer, T.J., 1978. Burrows at certain omission surfaces in the middle Ordovician of the Upper Mississippi Valley. Journal of Paleontology 52 (1), 109±117. Pelin, S. 1977. Geology of the southeastern Alucra (Giresun) region regarding the possibilities of oil. Publication of Karadeniz Technical University, 13, 103pp. (in Turkish). Pemberton, S.G, Frey, R.W, Sounders, T.D, 1990. Trace fossils. In: Briggs, D.E., Crowther, P.R. (Eds.). Palaeobiology Ð A Synthesis. Blackwell Science Publication, London, pp. 355±362. PeyberneÁs, B., Conrad, M.A., 1979. Les Algues du CreÂtace infeÂrieur de Hongrie. Bulletin des Centres de Recherches. Exploration±Production Elf-Aquitaine 3 (2), 743±752. Pienkowski, G., 1985. Early Liassic trace fossil assemblages from the Holy Cross Mountains, Poland: Their distribution in continental and marginal marine environments. In: Curran, H.A. (Ed.). Biogenic Structures: Their Use in Interpreting Depositional Environments. Society of Economic Paleontologists Mineralogists Special Publication 35, pp. 37±51. Purser, B.h., 1969. Syn-sedimentary marine lithi®cation of middle Jurassic limestones in the Paris Basin. Sedimentology 12, 205±230. Robertson, A.H.F., Dixon, J.E., 1984. Introduction: aspects of the geological evolution of the Eastern Mediterranean. In: Dixon, J.E., Robertson, A.H.F. (Eds.). Geological Society of London Special Publication 17. pp. 1±74. Sengor, A.M.C., 1984. The Cimmeride orogenic system and the tectonics of Eurasia. Geological Society of America Special Publication 195, 82. Sengor, A.M.C., Yilmaz, Y., 1981. Tethyan evolution of Turkey: a plate tectonic approach. Tectonophysics 75, 181±241. Sengor, A.M.C, Yilmaz, Y., Sungurlu, O., 1984. Tectonics of the Mediterranean Cimmerides: nature and evolution of the western termination of Palaeo-Tethys. In: Dixon, J.E., Robertson, A.H.F. (Eds.). Geological Evolution of the Eastern Mediterranean. Geological Society of London Special Publication 17, pp. 77±112. Shinn, E.A., 1969. Submarine lithi®cation of Holocene carbonate sediments in the Persian Gulf. Sedimentology 12, 109±144.
Sokac, B., 1996. Taxonomic review of some Barremian and Aptian calcareous algae Dasycladales) from the Dinaric and Adriatic Karst Regions of Croatia. Geologia Croatica 49 (1), 1±79. Tasli, K., 1991. Stratigraphy, paleogeography and micropaleontology of Upper Jurassic±Lower Cretaceous carbonate sequence in the GuÈmuÈshane and Bayburt areas (NE Turkey), Unpublished PhD Thesis (in Turkish), Black Sea Technical University, Trabzon, 223pp. È zsayar, T., 1997. Stratigraphy and paleoenvironmental setting of Tasli, K., O the Albian-Campanian deposits within the GuÈmuÈshane province (Eastern Pontides, NE Turkey). Turkish Association of Petroleum Geologists Bulletin 9 (1), 13±29. Tokel, S., 1972 Stratigraphical and volcanic history of the GuÈmuÈshane region (Turkey), Unpublished PhD Thesis, University College, London. Tucker, M.E., Wright, V.P., 1990. Carbonate Sedimentology. Oxford, Blackwell Scienti®c Publication, 482. Tucker, M.E., 1991. Sedimentary Petrology Ð An Introduction to the Origin of Sedimentary Rocks. Blackwell Scienti®c Publication, Oxford 260pp. Wilkinson, B.H, Janecke, S.U., Brett, C.E., 1982. Low-magnesian calcite marine cement in Middle Ordovician hardgrounds from Kirk®eld, Ontario. Journal of Sedimentary Petrology 52, 47±57. Wilkinson, B.H, Smith, A.L., Lohmann, K.C., 1985. Sparry calcite marine cement in Upper Jurassic limestones of southeastern Wyoming. In: Schneldermann, N., Harris, P.M. (Eds.), Carbonate Cements. Society of Economic Paleontologists and Mineralogists Special Publication 36, pp. 169±184. Wilson, I.G., 1975. Carbonate Facies in Geologic History. Springer, Berlin 471pp. Wilson, M.A., Palmer, T.J., 1992. Hardground and hardground faunas. University of Wales, Aberystwyth, Institute of Earth Study Publication 9, 131. Winterer, E.L., Sarti, M., 1994. Neptunian dykes and associated features in southern Spain: mechanics of formation and tectonic implications. Sedimentology 41, 1109±1132. Yilmaz, C., 1997. The sedimentological records of the Cretaceous platform-basin transition in the GuÈmuÈshane region (NE Turkey). Geologie MediterraneÂenne 24 (1±2), 125±135.
www.elsevier.com/locate/jseaes
Kilop Cretaceous Hardground (Kale, GuÈmuÈshane, NE Turkey):description and origin Muhsin Eren*, Kemal Tasli È niversitesi MuÈhendislik FakuÈltesi, Jeoloji MuÈhendislik BoÈluÈmuÈ 33342 CËiftlikkoÈy, Turkey Mersin U Received 12 March 2001; accepted 15 March 2001
Abstract A hardground surface is well exposed in the Kilop area of Kale (GuÈmuÈshane, NE Turkey) which forms part of the Eastern Pontides. Here, the hardground is underlain by shallow water Lower Cretaceous limestones, and overlain by Upper Cretaceous red limestones/marls which contains a planktonic microfauna including Globotruncanidae. In the ®eld, the recognition of the hardground is based on the presence of extensive burrows (especially vertical burrows), the encrusting rudistid bivalve Requienia, neptunian-dykes with in®lls of pelagic sediments and synsedimentary faults. Skolithos and Thalassinoides-type burrows are present. Some burrow walls show iron hydroxide-staining. The extensive burrowing occurred prior to lithi®cation. On the other hand, the neptunian-dykes and synsedimentary faults, which cut the hard ground, occurred after the lithi®cation. These features indicate the progressive hardening of the substrate. The burrowed limestone consists of an intrabioclastic peloidal grainstone which was deposited in an intertidal to shallow, subtidal, moderate to relatively high energy environment. The peloidal limestone shows little or no evidence of submarine cementation, characterized by only scarce relics of isopachous cement rims of bladed calcite spar. The grainstone cement is composed predominantly of blocky calcite and overgrowth calcite cements on the echinoid-fragments. The origin of this cement is controversial. Biostratigraphic analysis of the limestones demonstrates that there is a marked stratigraphic gap (hiatus), spanning the Aptian to the Santonian, in the Cretaceous of the Kilop area. The formation of the Kilop Hardground is related to the break-up and subsidence of the Eastern Pontides carbonate platform during the formation of the Black Sea backarc basin. Hardground development was initiated in a shallow marine environment of slow sedimentation and with moderate to high energy indicating slow subsidence. Later, the hardground subsided abruptly, as shown by the deposition of pelagic sediments on the hardground surface. During drowning, the Kilop area was converted to a bypass-margin where currents were effective. The formation of the hardground may also have been associated with an eustatic rise in sea-level. q 2002 Elsevier Science Ltd. All rights reserved. Keywords: Hardground; Sedimentology; Stratigraphy; Diagenesis; Cretaceous
1. Introduction Hardgrounds are surfaces of synsedimentary lithi®cation and represent a break in sedimentation (Shinn, 1969; Bromley, 1975; Kennedy and Garrison, 1975; Bathurst, 1975; Tucker, 1991; Wilson and Palmer, 1992). These surfaces may be recognized by the presence of abrasion, encrustations and borings and may cut across fossils and sedimentary structures. Some hardgrounds develop from loose sediments, through ®rmgrounds, to lithi®ed layers, and indicate a progressive hardening which is characterized by a change in the fauna, particularly the burrowing organisms, and by sedimentary features (Tucker, 1991; FuÈrsich et al., * Corresponding author. E-mail address: [email protected] (M. Eren).
1981). Some hardgrounds are mineralized, with iron hydroxides (goethite-limonite), and glauconite and phosphorite impregnating the sediment, burrow walls and fossils, and occurring as discrete grains (Tucker and Wright, 1990). Both intense submarine cementation and borings and/or burrowing indicate slow sedimentation in the depositional environment (Shinn, 1969; Tucker and Wright, 1990; Macintyre, 1977; James and Ginsburg, 1979). In the recognition of hardgrounds, geologists face two main problems. The ®rst problem is hardground identi®cation. The second problem is the recognition of the diagenetic environment in which lithi®cation took place Ð either submarine or subaerial (Bathurst, 1975). Research on hardground recognition has been published by Shinn (1969), Purser (1969), Kennedy and Garrison (1975), Garrison et al. (1987), Marshall and Ashton
1367-9120/02/$ - see front matter q 2002 Elsevier Science Ltd. All rights reserved. PII: S 1367-912 0(01)00027-X
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È zsayar et al., 1981) and location of the study area. (1) Kilop section, (2) KecËidere section, (3) CËukutbasi Fig. 1. Schematic map showing the Eastern Pontides (O Tepe section.
(1980), Goldring and Kazmierczak (1974), Dravis (1979) and Brett and Brook®eld (1984). This paper aims to introduce the Kilop Hardground as a Cretaceous example, and to investigate its origin. Chronostratigraphic interpretation of the carbonate platform sequences underlying the Kilop Hardground has been made using benthic foraminifers and calcareous algae. Sequences representing the facies of the drowning È zsayar (1997). platform were studied by Tasli and O 2. Kilop Cretaceous hardground The hardground surface is well exposed in the Kilop area of Kale (GuÈmuÈshane, NE Turkey), a small town located on the road between GuÈmuÈshane and Bayburt (Fig. 1). Here the hardground caps a burrowed peloidal limestone (grainstone) of the Berdiga Formation, covering an area of 0.5 km 2. The Berdiga Formation is made up of platform carbonates of Late Jurassic to Early Cretaceous age (Eren, 1983; Tasli, 1991). In the ®eld, the Kilop Hardground is overlain, apparently conformably, by the Kermutdere Formation, which consists mainly of Upper Cretaceous turbiditic sequences
(Tokel, 1972). The basal unit of the Kermutdere Formation, immediately overlying the hardground surface, is a red argillaceous limestone/marl which contains a planktonic microfauna, such as Globotruncanidae (Fig. 2A). This condensed sequence occurs as a thin, but continuous stratigraphic level in the Eastern Pontides, and plays a fundamental role in stratigraphic correlation, both regionally and globally. This unit passes upward into the turbiditic facies which is made up of an alternation of thin-bedded marl, pelagic biomicrite and sandstone. In the ®eld, the hardground surface is characterized by extensive burrowing (Fig. 2B and C) with large encrusting sessile organisms, such as the rudistid bivalve Requienia (Fig. 2D) that required a ®rm or hard substrate on which to live. Two types of burrows are present. The ®rst are simple vertical tubes of Skolithos Ð type burrows (Fig. 2B). Their cross-sections are circular having an average diameter of 1 cm. Some of them demonstrate concentric zonations, with a central nucleus, with a yellow stained burrow wall, surrounded by a halo affecting the zone of bioturbation. The second type of burrow forms anastomosing networks of selectively silici®ed Thalassinoides(?) burrows (Fig. 2C).
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Fig. 2. Field photographs of the Kilop Cretaceous hardground. (A) A ®eld photograph of the Kilop hardground surface (H) which is apparently conformably overlain by the red argillaceous limestone/marl (R), and later by turbiditic sediments (T). (B) Plan view of Skolithos-type trace fossils. Most burrow walls have yellow ferruginous staining (arrow). (C) Plan view of Thalassinoides(?)-type trace fossils (arrows) selectively silici®ed and showing branching. (D) Body fossils of Requenia sp. (arrows) encrusting the hardground surface. (E) A neptunian-dyke with in®ll of red pelagic limestone (arrow). (F) A syn-sedimentary fault (arrow) associated with the hardground surface. C: Platform carbonate, R: red argillaceous limestone/marl.
These burrow systems consists of horizontal branching burrows with an average diameter of 1 cm. The burrows show up as brownish mottling on the hardground surface (Fig. 2C). Furthermore, the hardground surface is cut by several neptunian dykes, with in®lls of red pelagic limestone (Fig. 2E), showing similar features to the overlying red beds, and by a syn-sedimentary fault (Fig. 2F). The
strike of the neptunian dykes and the fault plane is approximately N±S. Microscopic studies show that the burrowed limestone consists mainly of peloidal grainstone (Fig. 3A). In addition to peloids, other constituents are echinoderm debris, benthic foraminifers and intraclasts. Some relics of matrix are present locally. Primary pores are ®lled
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predominantly by blocky calcite cement (Fig. 3A) and syntaxial overgrowth cements on the echinodermfragments (Fig. 3B). Very locally relic-textures of isopachous marine cement rims of bladed spar can also be seen (Fig. 3C). 3. Regional and tectonic settings The GuÈmuÈshane region, in which the Kilop Harground occurs, is a part of the Eastern Pontides (Fig. 1), extending in E±W direction along the southern shore of the Eastern Black Sea. The geotectonic evolution of the Eastern Pontides is still debated. According to Sengor et al. (1984), it forms the eastern part of the Rhodope-Pontid Fragment. It is generally accepted that the RhodopePontid fragment lies entirely to the north of the Neo-Tethyan oceanic sutures and therefore formed the northern margin of the Jurassic±Cretaceous Neo-Tethys (e.g. Sengor and Yilmaz, 1981; Sengor et al., 1984; Sengor, 1984; Robertson and Dixon, 1984). The main points of contention focus on the palaeo-subduction direction, whether to the north beneath Eurasia, or to the south beneath Gondwana. Sengor and Yilmaz (1981) suggest that the Neo-Tethys was consumed from the Early Jurassic to middle Eocene by northward-directed subduction (Fig. 4A). In this view the Black Sea represents the remnant of a back-arc basin which opened to the north of the Eastern Pontides during the Late Cretaceous. However, Dewey et al. (1973) and Bektas et al. (1984) suggest that the Eastern Pontides were attached to a segment of the Neo-Tethys which was subducted towards the south. In this model the Black Sea represents a remnant of the Palaeo-Tethys Ocean. The GuÈmuÈshane region, including the site of the Kilop Hardground is situated on the northern margin of the Rhodope-Pontid Fragment facing onto the Black Sea (Fig. 4A). The Jurassic±Lower Cretaceous carbonate platform of the GuÈmuÈshane region was broken up by extensional tectonic movements during Albian-Santonian time (Albian in Yilmaz, 1997). This conclusion has been con®rmed by Bektas et al. (1995) for the Eastern Pontides, and by GoÈruÈr et al. (1993) for the Western Pontides, with a slight time difference. This rifting is considered to be related to opening of a back-arc basin (Sengor and Yilmaz, 1981; Sengor 1984; Bektas et al., 1984). However, Gedik et al. (1996) explain the rifting as the result of subduction and shear tectonics. The Berdiga Formation (platform carbonates) and the Kermutdere Formation (turbidites) in the GuÈmuÈshane region record and transition from platform to lower slope and basinal settings, respectively. In this region tectonic drowning of the carbonate platform resulted in the formation of paleo-rises and depression areas; hardgrounds, such as the Kilop Hardground, characterize local environments within this depositional setting (Fig. 4B).
Fig. 3. (A) Photomicrograph of burrowed limestone consisting of peloidal grainstone showing sparry calcite cement in intergranular pores. Dark grains are peloids (arrows). (B) Syn-taxial overgrowth calcite cement (c) on an echinoderm-fragment (e). (C) A relic of isopachous marine cement rim of bladed spars (arrow). p: peloid.
4. Biostratigraphy and environmental setting of the Cretaceous sequences In the GuÈmuÈshane area, Upper Jurassic±Lower Cretaceous platform carbonates have been correlated with the Berdiga Formation ®rst described by Pelin (1977) from the Alucra (Giresun) area. The Upper Cretaceous
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Fig. 4. (A) A geotectonic cross-section, showing the main features of the Eastern Pontides, modi®ed from Sengor and Yilmaz (1981). (B) A depositional model for the Upper Cretaceous sediments in the Kale area (GuÈmuÈshane) and the hardground location.
conglomerates, calcarenites (Fig. 7, unit E), red pelagic limestones (Fig. 7, unit F) and siliciclastic turbidites have been named the Kermutdere Formation (Tokel, 1972). Albo-Cenomanian to Turonian-Coniacian outer shelf to slope carbonates (Fig. 8, units C and D) were ®rst described È zsayar (1997), but have not been named. by Tasli and O Detailed microfacies analysis of three different measured sections, from Kilop and adjacent areas, permits recognition of ®ve informal lithostratigraphic units within the Cretaceous carbonate sequence. The same symbols are used for the same units in different section localities. The stratigraphic distribution of microfossils in the sections is illustrated in Figs. 5±7. Biostratigraphic control is provided by benthic and planktic foraminifers identi®ed from thin sections. The descriptions are given from bottom to top of the sections. Unit A, which terminates with the hardground surface in the Kilop area, is represented by medium- to thick-bedded gray limestones and subordinate dolomitic limestones in the lower part. It consists mainly of intraclastic, peloidal grainstones and packstones with benthic foraminifers and calcareous algae. Stromatolitic algal laminations with fenestral fabric alternate with the aforementioned grain/packstones, and contain oligotypic microfauna composed of ostracoda and Miliolidae. The lower part of Unit A corresponds to an assemblage of benthic foraminifers known from the Berriasian-Valanginian interval (Arnaud-Vanneau and Darsac, 1984). The following benthic foraminifers have been identi®ed: Pseudotextulariella salevensis CHAROLLAIS, BRONNIMAN and ZANINETTI (Fig. 10D1, D2), Haplophragmoides sp. (Fig. 9C1, C2), Trocholina sp. A3 DARSAC (Fig. 10H1,
H2), Trocholina elongata (LEUPOLD and BIGLER) (Fig. 10F), Trocholina cf. alpina (LEUPOLD and BIGLER) (Fig. 10G), Barkerina cf. barkerensis FRIZZEL and SCHWARTZ (Fig. 9A1, A2), Pseudocyclammina lituus (YOKOYAMA) (Fig. 10D), Arenobulimina sp. (Fig. 10E1, E2), Charentia nana ARNAUD-VANNEAU, Miliolidae and Textulariidae. Calcareous algae are represented by Salpingoporella annulata CAROZZI (Fig.11B), Actinoporella sp., Acicularia/Terquemella (Fig. 11H), Bakalovaella sp., Thaumatoporella parvovesiculifera (RAINERI) (Fig. 11I). In the overlying biozone, some of the aforementioned benthic foraminifers are completely missing and some new forms appear; Pseudolituonella gavonensis FOURY (Fig. 10B), Everticyclammina sp. (Fig. 9F), Pseudotextulariella sp., Praechrysalidina sp. (Fig. 10A1, A2), Vercorsella cf. laurentii (SARTONI and CRESCENTI) (Fig. 10 C1, C2), Everticyclammina hedbergi (MAYNC) (Fig. 9F), Haplophragmoides sp., Bolivinopsis spp. (Fig. 9H, I). Calcareous algae are sporadically abundant; Actinoporella nigra (CONRAD and PEYBERNES) (Fig. 11G), Bakalovaella cf. elitzae (BAKOLOVA) (Fig. 11D1, D2), Salpingoporella annulata CAROZZI, Salpingoporella hispanica CONRAD and GRABNER (Fig. 11E), Cylindroporella sp. (Fig. 11C), Acicularial/Terquemella, Clypeina sp. (Fig. 11F), Bacinella irregularis RADOICIC, Thaumatoporella parvovesiculifera (RAINERI), Solenopora sp. In the Mediterranean realm, this association ranges from the Hauterivian to Aptian. Salpingoporella hispanica is known from the Barremian in Italy (Chiocchini et al., 1979; Sokac, 1996) and from Barremian-Bedoulian in
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Fig. 5. Kilop stratigraphic section showing distribution of foraminifers and calcareous algae used for biostratigraphic subdivision, and also biogenic constitutents, textures and rock units.
Hungary (PeyberneÁs and Conrad, 1979). Concerning the benthic foraminifers, Vercorsella laurentii occurs in the Aptian of Italy (Chiocchini et al., 1984) and in the Barremian-lower Aptian of NE Turkey (Kirmaci et al., 1996). Sedimentary structures (algal laminations, fenestral fabric) and the microfossil content of unit A indicate an intertidal to very shallow subtidal depositional environment. Unit B marks a change of depositional pattern. It consists of monotonous cherty micrites with bryozoa, sponge and fossil fragments, such as echinoderm, pelecypoda and ostracoda, which are partly silici®ed. There are also
typical foraminifers of the outer platform environment, such as lenticulina sp., Spirillinidae and very rare Globuligerina sp. (Protoglobigerina). The depositional environment gradually evolved into a deeper shelf sea with open circulation, thus the pre-existing biota and facies was completely drowned. A probable Aptian-Albian age is suggested here for unit B, because it rests conformably on unit A of Hauterivian to Aptian age. The upper boundary of unit B could not be observed in the sections, therefore this portion of the Cretaceous sequence was not sampled.
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Fig. 6. KecËidere stratigraphic section showing distribution of foraminifers and calcareous algae used for biostratigraphic subdivision, and furthermore biogenic allochems, textures and rock units.
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Fig. 7. CËukutbasy stratigrapic section showing distribution of calcispheres and planktonic foraminifers used for biostratigraphic subdivision, and also biogenic È zsayar, 1997). allochems, textures and rock units (Tasli and O
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Fig. 8. Lithostratigraphic correlation of the three measured sections from the Kale area showing the presence of a stratigraphic gap within the Kilop section. The stratigraphic gap spans the period from Aptian to Santonian.
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Unit C is represented by thick- to very thick-bedded cherty limestones, composed of interbedded wackestones and intraclastic peloidal grainstones, with small benthic foraminifers (Fig. 11N), such as Gaudryina sp., Glomospira sp., Bolivinopsis sp., Lenticulina sp., small Valvulinidae and Textulariidae. The wackestones contain siliceous sponge spicules (Fig. 11M), subordinate echinoderm debris, bryozoa, ostracoda and extremely rare Calcisphaerula innominata BONET. Some beds are comprised of up 10 percent of silt-sized quartz grains. The presence of small benthic foraminiferal assemblage, and biomicrite with sponge spicules, indicates that the depositional environment was outer shelf, nearby upper slope. Signi®cant biomarkers are lacking. Units C is conformably overlain by Turonian-Coniacian limestone (unit D). Thus it is tentatively ascribed to the Upper Albian-Cenomanian. According to Adams et al. (1967) (in Andri, 1972, small-sized and thick-walled forms of Calcisphaerula innominata predominate in the Upper Albian-Cenomanian. Unit D is made of by thin- to thick-bedded, bioturbated argillaceous limestones with thin layers of shale/marl. It is sporadically interrupted by graded and very thick-bedded calcarenites. The contact with the underlying unit is even and sharp. The argillaceous limestones are composed of wackestones with abundant calcispheres and planktonic foraminifers; Calciphaerula innominata BONET, Pithonella ovalis KAUFMANN, Marginotruncana coronata (BOLLI) / pseudolinneiana PESSAGNO, Whitinella/ Hedbergella, Heterohelicidae, Planomalinidae. This assemblage indicates an age span from Turonian to Santonian (Caron, 1985). Organisms and sedimentary structures (slumpings and nodular beds) indicate a slope depositional environment. The calcarenitic intercalations are interpreted as a transported shelf materials, because of their close association with the surrounding pelagic wackestones. Limestones occupying the same stratigraphic position and with the same facies are also present in Ikisu (east of GuÈmuÈshÈ zsayar, 1997). ane) (Tasli and O Unit D is overlain unconformably by Unit E, which consists mainly of monomictic conglomerates with intercalactions and lenses of calcarenite, siltstone and red mudstone. Clasts are mainly limestone, subordinate chert and volcanic rock. The conglomerates pass upwards through a thick gastropoda (Nerinea and Actaeonella) biostrome and a bioclastic limestone bed into red argillaceous limestones/
marls (Unit F). The red limestones are composed of wackestones with planktonic foraminifers and rare radiolaria. The basal beds of unit E contain an assemblage comprising Dicarinella concavata (BROTZEN) (Fig. 11L) which is indicative of a latest Coniacian-Santonian age (Caron, 1985), while the upper part contains Globotruncanita elevata (BROTZEN) (Fig. 11J), characteristic of the Campanian. Unit F has a great lateral extent with a remarkably uniform lithology, forming a lithostraphic marker horizon in the Eastern Pontides. It is overlain by siliciclastic turbidites, composed mainly of a marl±shale±sandstone alternation. Fig. 8 shows the correlation of three measured sections, showing the stratigraphic position of the hardground and the absence of units B, C and D in the Kilop pro®le. 5. Hardground origin Extensive burrows (especially vertical burrows), encrusting organisms and very rare marine cement relics are characteristics of the Kilop Hardground, and indicate slow sedimentation (Wilson, 1975; Pienkowski, 1985; Shinn, 1969). Dwelling traces of suspension feeders, such as Skolithos and Thalassinoides (?) indicate a soft substrate (Frey and Pemberton, 1984; FuÈrsich et al., 1981). Thalassinoides commonly forms a burrow-system below many hardgrounds (Bromley, 1967, 1975; Goldring and Kazmierczak, 1974; Palmer, 1978; Brown and Farrow, 1978). Burrowing may have been intense before lithi®cation, as the sedimentation rate slowed down. Furthermore, the presence of neptunian dykes and a synsedimentary fault suggests a hard substrate, rather that a soft substrate, at that time (Winterer and Sarti, 1994; James and Choquette, 1983). All these features indicate progressive hardening of the substrate with time. The burrowed peloidal grainstone does not show any clear evidence of marine cementation, except for some relics of an isopachous marine cement rim with bladed spars. The grainstone has a predominantly blocky calcite cement with syntaxial overgrowth on echinoid fragments. The origin of these cements is controversial. Both blocky calcite and syntaxial overgrowth cements are known to be precipitated from supersaturated meteoric water in either the phreatic or vadose zones. However, several authors have
Fig. 9. Benthic foraminifers from the Early Cretaceous of the Kale (GuÈmuÈshane) area (northeastern Turkey). (A) Barkerina cf. barkerensis FRIZZEL and SCHWARTZ. This form is very similar to the type species of the genus Barkerina described originally from Texas Albian (Frizzell and Schwartz, 1950; in Hamaoui, 1973) and it is restricted to upper part of the Pseudotextulariella salevensis cenozone (upper Valanginian) in the GuÈmuÈshane region (Tasli, 1991). (A1) Equatorial section, sample GL 61-3, A2. Subaxial section, sample GL 61-1. (B) Charentia cuvillieri NEUMANN. (B1) Equatorial±longitudinal section showing a marked uniserial stage, sample GL 127-6, B2. Oblique equatorial±longitudinal section showing the single, simple aperture in the uniserial stage, sample GL 127-5, (B3) Equatorial section, sample GL 127-7, B4. Axial section, sample GL 127-4.(C) Haplophragmoides sp. (C1) Axial section, sample GL 130, (C2) Equatorial section, sample GL 109. (D) Pseudocyclammina lituus (YOKOYAMA). Subaxial section, sample GL 57-3. (E) Pseudochoffatella sp. (E1) Equatorial section, sample GL 57-2, (E2) Subaxial section (form B), sample GL 57-1. (F) Everticyclammina sp. Subequatorial±longitudinal section, sample GL 68-6. (G) Everticyclammina hedbergi (MAYNC). Subaxial section, sample HUR 103. (H) Bolivinopsis sp. (B) Equatorial±vertical section, sample GL 103-2. (I) Bolivinopsis sp. (A) Equatorial±vertical section, sample GL 76-2. Bar scales: 0.25 mm.
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suggested a marine origin for these cements when associated with hardgrounds (Wilkinson et al., 1982; Wilkinson et al., 1985; Garrison et al., 1987; Kim and Lee, 1996). Meyers (1974) and Lohmann and Meyers (1977) also report that precipitation of syntaxial overgrowth of Mg-calcite cement in a shallow marine environment is a common phenomenon. No evidence exists for the emergence of the sea ¯oor. So we interpret the early diagenetic lithi®cation as having occurred in a submarine environment, based on the truncation of body fossils (Fig. 2D), the presence of neptunian dykes, with pelagic sediment in®lls, a syn-sedimentary fault and an abrupt change from shallow marine to relatively deep marine conditions. In general, vertical burrows such as Skolithos-type dominate where high-energy conditions keep sur®cial sediments mobile, whereas horizontal burrows dominate where energy conditions are low and nutrients are abundant within the substrate. Therefore, the trace fossil assemblages of the Kilop area are indicative of intertidal to shallow subtidal environments and moderate to high energy conditions (Pienkowski, 1985; Pemberton et al., 1990; Frey and Pemberton, 1984). Microfacial analysis of unit A, which terminates with a hardground surface in the Kilop area, provides supportive evidence for a similar depositional environment. Comparison of three measured stratigraphic sections from Kilop and adjacent areas reveals that the kilop pro®le lacks the uppermost part of Berdiga Formation and some basal units of Kermutdere Formation, such as the conglomerate (Fig. 8). During non-deposition or slow sedimentation in the Kilop area, carbonate sedimentation continued in the adjacent areas, including the resedimentation of materials such as calcarenite and calcilutite, from uplifted areas of the carbonate platform. Resedimented materials suggest erosional process and the effects of currents on the surrounding areas. Features mentioned above suggest that the Kilop Hardground probably formed on a bypass margin which was the site of carbonate deposition; its development representing a cessation of sedimentation. Hardground formation almost invariably coincides with a marked lithological change from shallow marine platform carbonates below, to probably considerably deeper marine red argillaceous limestone/marl with a planktonic microfauna, above. This surface, therefore, separates regressive carbonates and transgressive deeper red pelagic argillaceous limestone/marls. The stages in the drowning of the carbonate platform are represented by the sediments missing from
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the Kilop pro®le, including units B, C and D. This vertical transition marks a drastic change in tectonic conditions, which resulted in sudden deepening of the carbonate platform by vertical movements. Transgression may have been associated with these vertical movements. During the Upper Cretaceous the Eastern Pontide carbonate platform was broken up at a progressively increasing rate, and was converted into a narrow and long deep marine trough trending in a ENE±WSW direction. Turbiditic sediments of Upper Cretaceous age were deposited in this trough. The break-up of the carbonate platform resulted a long stratigraphic gap spanning an interval from Aptian to Santonian. If we consider the progressive deepening of the environment, we may say that submarine lithi®cation began in a shallow environment. Shinn (1969) has noted that submarine lithi®cation is especially active in water depths of around 20 m. The formation of the neptunian-dykes and the syn-sedimentary fault took place in a deeper environment, where red argillaceous limestone/marl could accumulate. 6. Conclusions An ancient hardground surface is exposed in the Kilop area, characterized by extensive burrows, large encrusting organisms and scarce relics of submarine rim cement. Neptunian dykes and a syn-sedimentary fault with regular boundary indicate that the substrate was well lithi®ed prior to the deposition of the overlying deeper marine argillaceous sediments which also in®ll the sedimentary dykes. The hardground occurs at the top of the regressive sequences of the Berdiga Formation, where it presents a marked stratigraphic gap (hiatus) which spanning the Aptian to Santonian. The hardground formation is related to breaking up of the Eastern Pontides carbonate platform, and may also be associated with an eustatic rise of sea-level. This break-up was probably associated with the development of a back-arc basin. Acknowledgements The authors are indebted to Prof. Alastair Robertson and Dr Mark Wilson for their constructive comments on an earlier version of the paper, and to Dr A.J. Barber for improvements to the English.
Fig. 10. Benthic foraminifers from the Early Cretaceous of the Kale (GuÈmuÈshane) area (northeastern Turkey). (A) Praechrysalidina sp. A1. Subaxial section, sample HUR 92, A 2. Transverse section, sample HUR 80. (B) Pseudolituonella gavonensis FOURY. Subaxial section, sample GL 76-2. (C) Vercorsella cf. laurentii (SARTONI and CRESCENTI). (C1) Subaxial section, sample GL 109-4. (C2) Transverse-oblique section, sample GL 130-5. (D) Pseudotextulariella È NNIMANN and ZANINETTI. (D1) Parallel section, sample GL 55-3. (D2) Oblique-transverse section passed through the salevensis CHAROLLAIS, BRO aperture, sample GL 51. (E) Arenobulimina sp. (E1) Transverse section, sample GL 89-1. (E2) Oblique-transverse section, sample GL 113-4. (F) Trocholina elongata (LEUPOLD and BIGLER). Axial section, sample HUR 70.G. Trocholina cf. alpina (LEUPOLD and BIGLER) Axial section, sample GL 89-1. (H) Trocholina sp. A3 DARSAC (in Arnaud-Vanneau and Darsac, 1984). (H1) Axial section showing the spheric proloculus (form A), sample HUR 69, H2. Oblique axial section, sample HUR 70. Bar scales: 0.25 mm.
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References Adams, T.D., Khalili, M., Khosrovi Said, A., 1967. Stratigraphic signi®cance of some oligosteginid assemblages from Lurestan Province, northwest Iran. Micropaleontology 13 (1), 55±67. Andri, E., 1972. Mise au point et donneÂes nouvelles sur la famille des Calcisphaerulidae BONET (1956): les genres Bonetocardiella, Pithonella, Calcisphaerula et Stomiosphaera. Revue de MicropaleÂontology 15 (1), 12±34. Arnaud-Vanneau, A., Darsac, C., 1984. CaracteÂres et eÂvolution des peuplements de foraminifeÂres benthiques dans les principaux biotopes des plates-formes carbonateÂes du CreÂtace infeÂrieur des alpes du Nord (France). Geobios, Memoir Special N8 8, 19±23. Bathurst, R.G.C., 1975. Carbonate Sediments and their Diagenesis. Elsevier, Amsterdam p. 338. Bektas, O., Pelin, S., Korkmaz, S., 1984. Mantle uprising in the Eastern Pontide Back-Arc Basin and the concept of a polygenetic ophiolite. Geological Society of Turkey, 38th Scienti®c and Technical Congress, Ihsan Ketin Symposium (in Turkish with English Abstract), Ankara, pp. 175±188. È zguÈr, S., 1995. Cretaceous Bektas, O., Yilmaz, C., Tasli, K., Akdag, K., O rifting of the eastern Pontide carbonate platform (NE Turkey): The formation of carbonate breccias and turbidites as evidence of a drowned platform. Giornale di Geologia 57 (1±2), 233±244. Brett, C.E., Brook®eld, M.E., 1984. Morphology, faunas and genesis of Ordovician hardgrounds from southern Ontario, Canada. Palaeogeography, Palaeoclimatology, Palaeoecology 46, 233±290. Bromley, R.G., 1967. Some observations on burrows of thalassinidean Crustacea in chalk hardgrounds. Quarterly Journal of the Geological Society of London 123, 157±182. Bromley, R.G., 1975. Trace fossils at omission surfaces. In: Frey, R.W. (Ed.). The Study of Trace Fossils. Springer, New York, pp. 399±428. Brown, B.J., Farrow, G.E., 1978. Recent dolomitic concretions of crustacean burrow origin from Loch Sunart, West Coast of Scotland. Journal of Sedimentary Petrology 48 (3), 825±834. Caron, M., 1985. Cretaceous planktic foraminifera. In: Bolli, H., Saunders, J.B., Perch-Nielsen, K. (Eds.). Plankton Stratigraphy. Cambridge Earth Science Series, pp. 17±86. Chiocchini, M., Mancinelli, A., Molinari-Paganelli, V., Tiliari-Zuccari, A., 1979. ReÂpartition stratigraphique des algues dasycladales et codiaceÂes dans les successions MeÂsozoõÈques de plateforme carbonateÂe du Lazio centre-meÂridional (Italie). Bulletin des Centres de Recherches Exploration±Production Elf-Aquitanie 3 (2), 525±535. Chiocchini, M., Mancinelli, A., Romano, A., 1984. Stratigraphic distribution of benthic Foraminifera in the Aptian, Albian and Cenomanian carbonate sequences of Aurunci and Ausoni Mountains (Southern Lazio, Italy). Benthos'83; Second International Symposium on Benthic Foraminifera, pp. 167±181. Dewey, J.F, Pitman, W.C., Ryan, W.B.F., Bonnin, J., 1973. Plate tectonics and the evolution of the Alpine system. Geological Society of America Bulletin 84, 3137±3180. Dravis, J., 1979. Rapid and widespread generation of recent oolitic hardgrounds on a high energy Bahamian Platform, Eleuthera Bank, Bahamas. Journal of Sedimentary Petrology 49, 195±508.
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Eren, M., 1983. Geology and microfacies analysis of the GuÈmuÈshane-Kale area. Unpublished MSc Thesis, Karadeniz Technical University, Trabzon (in Turkish), 197pp. Frey, R.W., Pemberton, S.G., 1984. Trace fossil facies models. In: Walker, R.G. (Ed.). Facies models. 2nd ed. Geoscience Canada Reprint Series 1, pp. 189±207. Frizzell, D.L., Schwartz, E., 1950. A new lituolid foraminiferal genus from the Cretaceous with an emendation of Cribrostomoides Cushman. University of Missouri, Bulletin, Technical Series, 76. FuÈrsich, F.T, Kennedy, W.J., Palmer, T.J., 1981. Trace fossils at a regional discontinuity surface: The Austin/Taylor (Upper Cretaceous) contact in Central Texas. Journal of Paleontology 55, 537±551. Garrison, R.E., Kennedy, W.J., Palmer, T.J., 1987. Early lithi®cation and hardgrounds in Upper Albian and Cenomanian calcarenites, southwest England. Cretaceous Research 8, 103±140. Gedik, I., Kirmaci, M.Z., Capkinoglu, S., Ozer, E., Eren, M., 1996. Geological development of the Eastern Pontides. In: Kormaz, S., Akcay, M. (Eds.), Symposium Proceedings of the 30th Anniversary of the Geological Engineering Department, Karadeniz Teknik Universitesi, Trabzon, pp. 654±677 (in Turkish with English Abstract). Goldring, R., Kazmierczak, J., 1974. Ecological succession in intraformational hardground formation. Paleontology 17, 949±962. GoÈruÈr, N., TuÈysuÈz, O., Akyol, A., SakyncË, M., Yigitbas, E., AkkoÈk, R., 1993. Cretaceous red pelagic carbonates of northern Turkey: their place in the opening history of the Black Sea. Eclogae Geologicae Helvetiae 36 (3), 819±838. Hamaoui, M., 1973. Barkerina et formes voisines (ForaminifeÁres). Bulletin de Centre de Recherches de Pau-SNPA 7 (2), 337±359. James, N.P., Choquette, P.W., 1983. Diagenesis 6. Limestones Ð the sea ¯oor diagenetic environment. Geoscience Canada 10, 162±179. James, N.P., Ginsburg, R.N., 1979. The seaward margin of Belize barrier and atoll reefs. International Association of Sedimentologists, Special Publication 9, 131. Kennedy, W.J., Garrison, R.E., 1975. Morphology and genesis of nodular chalk and hardgrounds in the Upper Cretaceous of southern England. Sedimentology 22, 311±386. Kirmaci, M.Z., Koch, R., Bucur, J.I., 1996. An early Cretaceous section in the Kircaova area (Berdiga Limestone, NE Turkey) and its correlation with platform carbonates in W-Slovenia. Facies 34, 1±22. Kim, J.C., Lee, Y.I., 1996. Marine diagenesis of lower Ordovician carbonate sediments (Dumugol Formation), Korea Ð cementation in a calcite sea. Sedimentary Geology 102, 241±257. Lohmann, K.C, Meyers, W.J., 1977. Microdolomite inclusions in cloudy prismatic calcites Ð a proposed criterion for former high magnesium calcites. Journal of Sedimentary Petrology 47, 1078±1088. Macintyre, I.G., 1977. Distribution of submarine cements in a modern Caribbean fringing reef, Galeta Point, Pananma. Journal of Sedimentary Petrology 47 (2), 503±516. Marshall, J.D., Ashton, M., 1980. Isotopic and trace element evidence for submarine lithi®cation of hardgrounds in the Jurassic of eastern England. Sedimentology 27, 271±289. Meyers, W.J., 1974. Carbonate cement stratigraphy of the Lake Valley formation (Mississippian), Sacramento Mountains, New Mexico. Journal of Sedimentary Petrology 44, 837±861.
Fig. 11. Calcareous algae from the Early Cretaceous platform carbonates (Fig. 10A±I), planktonic foraminifers from the Late Cretaceous pelagic limestones (Fig. 10J±L) and facies types of middle Cretaceous limestones (Fig. 10M, N) in the Kale area. (A) Salpingoporella sp Oblique section, sample GL 76-4. (B) Salpingoporella annulata (CAROZZI). Longitudinal section, sample GL 68-2. (C) Cylindroporella sp. Oblique longitudinal section, sample GL 68. (D) Bakalovaella cf. elitzae (BAKALOVA). (D1) Longitudinal±tangential section, sample GL 68-5, (D2) Oblique section, sample GL 68-1. (E) Salpingoporella hispanica CONRAD and GRABNER. Oblique section, sample GL 73-2. (F) Clypeina sp. Oblique section, sample GL 130-5. (G) Actinoporella nigra (CONRAD and PEYBERNES). Transverse section, sample GL 76-3. (H) Acicularia/Terquemella. Sample GL 127-2. (I) Thaumatoporella parvovesiculifera (RAINERI). Tangential section, sample GL 72. (J) Globotruncanita elevata (BROTZEN). Oblique axial section, sample CËT 34, from upper part of red pelagic limestone (unit F). (K) Marginotruncana pseudolinneiana PESSAGNO. Axial and subaxial sections, sample CËT 20, from gray pelagic limestone (Unit D) of Turonian-Coniacian age. (L) Dicarinella concavata (BROTZEN). Subaxial section, sample CËT 30, from the base of red pelagic limestone (Unit F). (M) Biomicrite with sponge spicules (Unit C). Sample C Ë T 6. (N) Biopelsparite with small benthic foraminifers (Unit C). Sample C Ë T 5. Bar scales: 0.25 mm.
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