1-s2.0-S0195667197900616-main

Cretaceous Research (1997) 18 , 331 – 353

Fossil occurrences in the Upper Cenomanian – Lower Turonian at Ganuza , northern Spain : an approach to Cenomanian / Turonian boundary chronostratigraphy 1

Marcos A . Lamolda , *Amalia Gorostidi , † Ricard Martı ́ nez , † Gregori Lo ́ pez and ‡ Danuta Peryt

* Facultad de Ciencias - UPV , Campus de Lejona , 4 8 9 4 0 Lejona , Spain † Dept . de Geologia , Fac . de Ciencias , Univ . Autonoma , Campus de Bellaterra , 0 8 1 9 3 Bellaterra , Spain ‡ Institute of Palaeobiology , Polish Academy of Sciences , Al . Zwirki i Wigury 9 3 , 0 2 - 0 8 9 Warsaw , Poland

Revised manuscript accepted 2 2 January 1 9 9 7

An Upper Cenomanian to Lower Turonian section has been sampled in the vicinity of Ganuza , northern Spain . Ammonoids , inoceramids and microfossils including foraminifera and calcareous nannofossils have been studied . We recognize three planktonic foraminiferal biozones : the Rotalipora cushmani , Whiteinella archaeocretacea and Helvetoglobotruncana helvetica Zones . We also characterize the Eif fellithus turriseif felii and Quadrum gartneri Zones , based on nannofossil biostratigraphy . Macrofaunal occurrences are scarce but allow us to characterize the Metoicoceras geslinianum and Mammites nodosoides Zones , and two inoceramid assemblages .

In the Rotalipora cushmani Zone the following sequence of biohorizons is recorded from bottom to top : (a) last occurrence (LO) of Corollithion kennedyi ; (b) LO of Rotalipora greenhornensis ; (c) LO of Axopodorhabdus albianus ; (d) first occurrence (FO) of Euomphaloceras septemseriatum , (e) LO of Lithraphidites acutus ; (f) LO of Rotalipora cushmani .

In the Whiteinella archaeocretacea Zone the sequence of events is as follows : (g) FO of Calycoceras naviculare ; (h) LO of Microstaurus chiastius ; (i) FO of Quadrum intermedium ; (j) FO of Helvetoglobotruncana praehelvetica ; (k) FOs of Kamerunoceras sp . and Mytiloides submytiloides ; (l) FO of Mytiloides kossmati kossmati ; (m) FO of Kamerunoceras calvertense ; (n) FO of Quadrum gartneri ; (o) FO of Mammites nodosoides ; (p) FO of Mytiloides mytiloides . The top of this zone is marked by the FO of Helvetoglobotruncana helvetica . A possible Cenomanian-Turonian (C / T) boundary can be drawn between FOs of Kamerunoceras sp . and Mytiloides submytiloides and the FO of Mytiloides kossmati kossmati . Successive FOs of H . praehelvetica and Q . gartneri are also good proxies for the C / T boundary . ÷ 1997 Academic Press Limited

K E Y W O R D S : Cenomanian / Turonian boundary ; chronostratigraphy ; planktonic foraminifera ; nan- nofossils ; inoceramids ; ammonoids ; northern Spain .

1 . Introduction

The stratigraphic succession at Ganuza , northern Spain , is a composite section of an expanded Cenomanian – Turonian (C / T) transition where the Whiteinella archaeocretacea Zone is about 45 – 50 m thick . It is located to the west of Estella , in the eastern Bascocantabrian Region (Figure 1) . There is no evidence of stratigraphic gaps in the section which consists of an alternation of marl , marly limestone and limestone , with marl becoming more common towards the top , and some silty beds occurring towards the base . The sediments were deposited in a middle-outer shelf environment , according to the ostracod and foraminifera assemblages recovered (Colin et al ., 1982 ; Lamolda & Peryt , 1995) . The macrofauna , microfauna and calcareous nannofossil biostratigraphy allows us to 1 Contribution to IGCP Project 362 : Tethyan and Boreal Cretaceous .

0195 – 6671 / 97 / 030331 1 23 $25 . 00 / 0 / cr970061 ÷ 1997 Academic Press Limited

M . A . Lamolda et al . 332

Figure 1 . Location of the Ganuza section in northern Spain .

recognize several key events (according to Birkelund et al ., 1984) relating to C / T boundary definition .

A summary of the stratigraphy and regional geology is given in Lamolda (1982) . Macrofaunal assemblages were described by Wiedmann (1980) and Lamolda et al . (1989) from part of the Ganuza sections . Additional data on inoceramids and ammonoids were provided by Lo ́ pez (1990) and Santamarı ́ a (1991) respectively . Lamolda & Peryt (1995) described the detailed biostratig- raphy of the Upper Cenomanian of the section , and noted that bottom water conditions at the time of deposition of the uppermost part of Rotalipora cushmani Zone were dysaerobic . This correlates with the worldwide Cenomanian / Turonian Boundary Event (CTBE) , which is also defined by nannofossil events in the section studied (Lamolda & Gorostidi , 1996) .

In a similar section at Menoyo , 70 km west of Ganuza , both nannofossil assemblages and a d 13 C excursion have been discussed (Paul et al ., 1994) . The Menoyo section provides a continuous sequence through the C / T transition in outer shelf and upper bathyal facies—limestone and marl alternations , but it is very poor in macrofauna . Lamolda (1978) noted occurrences of Inoceramus gr . labiatus and Mammites sp . Recently , we have found inoceramid specimens belonging to Mytiloides wiedmanni . All of the macrofauna is of Early Turonian age , being recorded between the first occurrences (FOs) of Quadrum gartneri and Helvetoglobotruncana helvetica .

The Ganuza section represents deposition on a subsiding platform , when more than 2000 m of sediments accumulated during the Cenomanian and Turonian (Lamolda , 1982) . Last occurrences (LOs) of the planktonic foraminifera

Fossils in the Upper Cenomanian – Lower Turonian 333

Rotalipora greenhornensis and R . cushmani and the FO of the nannofossil species Q . gartneri are events recognized worldwide and are commonly used for correlation . Comparison of bed thicknesses between these events in the Ganuza section with coeval sections elsewhere which are considered to be the most expanded and complete record of the C / T boundary , has revealed that the Ganuza succession is about five times thicker than that at Pueblo , Colorado (USA) , seven times that at Dover , southeast England (Lamolda & Peryt , 1995) , and twice that at Eastbourne , southern England (Lamolda et al ., 1996) . Therefore , the Upper Cenomanian and lowermost Turonian succession at Ganuza is particularly complete . In addition , its rich macro- and microfossil record makes this section especially suitable for characterizing the C / T boundary .

2 . Material and methods

The section at Ganuza is exposed on both sides of the road , 200 – 300 m south of Ganuza village . It is a composite section (Figure 2) whose lower and upper parts could have some levels in common ; they are separated by a small fault . The succession comprises about 15 cycles of limestone and marl alternations . This cyclicity is also found in sections at Menoyo (Paul et al ., 1994) and Dover (Lamolda et al ., 1994) .

The lower part of the section studied , G (Figure 2) , consists of two marly / silty and two calcareous sequences . At the bottom there is a 16 . 5-m-thick sequence of siltstone and marl with interbeded limestone as thin layers and lenticular bodies . The sequence is overlain by a 6 . 1-m-thick calcareous series composed mainly of limestones and nodular limestones interbedded with thin marlstones and silt- stones . Higher up the section there is a 3 . 1-m-thick series of marly siltstone with irregular and scarce limestone interbeds . The top 4 . 3 m of the section comprises limestone and marlstone alternations . GS is a similar section about 100 m to the south of G . Both sections are on the east side of the road . The two uppermost G units are partly present in the base of the lower part of the GZ succession (Figure 2) , although an accurate correlation between G and GZ has not been possible . The G sequence was dated as middle-late Late Cenomanian by means of macrofauna and foraminifera (Wiedmann , 1980) . Lamolda et al . (1989 , fig . 2) defined ‘A’ and lower ‘B’ units in the sequence , which were dated as Late Cenomanian by means of planktonic foraminifera .

The GZ succession consists of 40 m of 10 or 11 cycles of marl and limestone alternations . The GZ part was dated by Wiedmann (1980) as Early Turonian on the basis of planktonic foraminifera . Neither he nor Lamolda et al . (1989) found macrofauna in GZ , but in the upper part , we have found foraminiferal assemblages characteristic of the Whiteinella archaeocretacea Zone of probable Early Turonian age according to its correlation with other neighbouring sections . The first macrofaunal data from the upper part of GZ sequence were reported by Lo ́ pez (1990) and Santamarı ́ a (1991) .

Forty-three samples from a 70-m-thick sequence of the Ganuza section (the G and GZ parts) , were studied for foraminifera . Four to five hundred specimens from the . 100 m m size fraction were picked and for each sample all species were identified . Forty-four samples in the GS and GZ parts were studied for nannofossils using a light microscope at a magnification of 3 1000 and quan- titative procedures described by Lamolda et al . (1994) . Counting of 500 nannoliths per sample gives a 99% ( p , 0 . 01) confidence level of not overlooking

M . A . Lamolda et al . 334

Figure 2 . Composite section at Ganuza to show lithology , location of micropalaeontological samples , and macrofaunal occurrences .

Fossils in the Upper Cenomanian – Lower Turonian 335

any taxon present at 1% or more of the total population (Denisson & Hay , 1967) . The macrofaunal assemblages were checked bed by bed throughout the section . Although generally sparsely distributed , some beds contain many fossils , such as sample GZ 4 , which records an inoceramid event , and G 22 , GZ 5 and GZ 6 , which yield numerous ammonoids .

3 . Nannofossil biostratigraphy

The abundance of nannoliths in the samples studied proved to be low , with only 1 nannolith per field of view (Nan . / FOV) or less . Their preservation is also poor . 54 species have been identified . The number of taxa per sample is between 15 and 30 . The assemblages are dominated by six taxa : Eif fellithus turriseif felii , Eprolithus floralis , Prediscosphaera spp ., Retecapsa spp ., Rhagodiscus achlyostaurion and Watznaueria barnesae (Figure 3) . Each of these comprises more than 5% of the assemblages . W . barnesae comprises 40 – 50% .

In the uppermost Cenomanian several major assemblage changes are recog- nised . These include LOs of , from the base of the section upwards (Figures 3 , 4) , Corollithion kennedyi (sample GS 12 ; 13 . 2 m) , Axopodorhabdus albianus (GS 16 ; 15 . 7 m) , Lithraphidites acutus (GS 18 ; 18 . 6 m) and Microstaurus chiastius (GZ 73 ; 6 . 3 m 5 approximately 13 . 4 m above GS 18) . First occurrences of biostratig- raphically important taxa include Quadrum intermedium (GZ a ; 7 . 3 m) , Eprolithus octopetalus and Nannoconus multicadus (GZ 58 ; 14 . 6 m) , and Q . gartneri (GZ 1 ; 16 . 5 m) . Rhagodiscus asper occurs throughout the section and overlaps the range of Q . gartneri , Eprolithus octopetalus and E . eptapetalus (Gorostidi , 1993 , pp . 174 , 175) .

Nannofossils are less common in the lower part , with a minimum at the level of the Rotalipora cushmani extinction , about 3 m above the LO of Lithraphidites acutus (Figure 4) . The assemblages recovered are similar to those reported from Menoyo (Gorostidi & Lamolda , 1991 ; Paul et al ., 1994) , southeast England (Crux , 1982 ; Jarvis et al ., 1988 ; Lamolda et al ., 1994) , and various localities in Northern Europe and North America (Bralower , 1988) . At Ganuza ‘blooms’ of Eprolithus floralis occur above the FO of Q . gartneri , comprising up to 32% of the total assemblage , which is even greater than has been found in the Dover (10%) and Menoyo (18%) sections .

We found Crux’s (1982) biozonation , established in southeast England , to be appropriate for our assemblages (Lamolda & Gorostidi , 1996) . Two biozones are partly distinguished , the Eif fellithus turriseif felii and Quadrum gartneri Zones . The former is characterized by the association of Eif fellithus turriseif felii , Eprolithus floralis , Glaukolithus compactus , Prediscosphaera avitus , P . cretacea , Retecapsa spp ., Rhagodiscus achlyostaurion , Tranolithus phacelosus , Watznaueria barnesae , W . biporta and Zeugrhabdotus embergeri .

LOs of Corollithion kennedyi , Axopodorhabdus albianus , Lithraphidites acutus and Microstaurus chiastius indicate that the Upper Cenomanian sequence is complete and their order of disappearance is similar to those in other sections (Figures 3 , 4) (Lamolda & Gorostidi , 1996) . This sequence of bioevents is important for the biostratigraphical characterization of the uppermost Cenomanian and the C / T boundary . Furthermore , FOs of Quadrum intermedium (GZ a ; 7 . 3 m) (Paul et al ., 1994) , and Nannoconus multicadus (GZ 58 ; 14 . 6 m) (Deres & Ache ́ rite ́ guy , 1980 ; Zeighampour , 1981 ; Crux , 1982) , enhance correlation and completeness of this C / T transition . In contrast the LO of Allemanites striatus , Rhagodiscus

M . A . Lamolda et al . 336

Figure 3 . Range chart for calcareous nannofossils from the Ganuza section . Abundance : C 5 1 – 10 Nan . / FOV ; R 5 1 Nan . / 1 – 10 FOV . Preservation : F 5 fair ; P 5 poor .

achlyostaurion , R . angustus , and R . asper cited by Crux (1982) in the English Upper Cenomanian , are recorded from Lower Turonian or younger deposits in northern Spain (Gorostidi , 1993) .

The lower boundary of the Quadrum gartneri Zone is defined by the first occurrence of the nominate taxon (sample GZ 1 ; 16 . 5 m) , which overlies the FO of Eprolithus octopetalus (GZ 58 ; 14 . 6 m) , a good indicator of the C / T boundary

Fossils in the Upper Cenomanian – Lower Turonian 337

Figure 4 . Ranges of planktonic foraminifera , ammonoids and inoceramids , and nannofossil event locations .

(Varol , 1992) . Its lower part is characterized by the taxa E . turriseif felii , E . floralis , G . compactus , Nannoconus spp ., P . cretacea , Retecapsa spp ., R . achlyostaurion , T . phacelosus , W . barnesae , W . biporta and Z . embergeri . The main dif ferences from the Eif fellithus turriseif felii Zone assemblages are higher proportions of P . cretacea

M . A . Lamolda et al . 338

and Nannoconus spp ., especially the latter , which is rare in the Upper Cenoma- nian and increases up to 3 – 9% of the total in Turonian assemblages , even higher than at Menoyo (3% ; Gorostidi , 1993 , p . 232) . Also , E . floralis is present in higher proportions in this Turonian material , usually more than 10% (between 50 and 160 specimens counted per sample studied) , whereas in the Upper Cenomanian it is less than this (between 1 and 50 specimens per sample studied) . In contrast , P . avitus decreases in abundance from 5% to less than 1% . The LO of R . asper has been cited as an important indicator of the C / T boundary (Crux , 1982 ; Jarvis et al ., 1988 ; Lamolda et al ., 1994) , but at Ganuza this species occurs throughout the section , and at Menoyo its LO is in Lower Turonian deposits (Paul et al ., 1994) . The data from northern Spain agree better with the probable events of Bralower (1988) and with results from Kalaat Senan in Tunisia (Gartner in Robaszynski et al ., 1990) . The LO of R . asper is probably diachronous depending on paleolatitude . It can no longer be regarded as biostratigraphically useful , but may have biogeographical and palaeoecological significance (Lamolda & Gorostidi , 1996) .

4 . Foraminifera

The diversity of planktonic foraminifera is low to moderate . Abundances are highly variable throughout the Ganuza section . In the Upper Cenomanian (samples G 33 to GZ 54) their contribution to the total foraminiferal assemblage varies from 12 – 80% ; in the lowermost Turonian these values are very high and almost stable at 72 – 88% .

The Late Cenomanian changes in planktonic / benthonic (P / B) ratio probably reflect sea-level fluctuations and indicate an inner to outer shelf environment ; the high P / B ratio in the upper part of the section suggests a rise in sea level during the latest Cenomanian and earliest Turonian to outer shelf depths .

In terms of palaeoecology the composition of the planktonic foraminiferal fauna from the Ganuza section shows that the sampled interval can be divided into three parts :

(1) A lower part from 4 . 2 – 25 . 8 m (samples G 33 to G 11 ; Figure 2) characterized by mixed , diverse assemblages , with a high proportion of keeled forms , such as the genera Rotalipora and Praeglobotruncana , and in the top part of this interval , Dicarinella .

(2) A relatively short interval approximately 11 . 6 m thick (samples G 11 to GZ 56) characterized by a temporary , almost complete , disappearance of keeled forms from the assemblages . Dicarinella spp . are very rare scarce . They may be found with rare specimens of Praeglobotruncana spp . Low diversity planktonic foraminiferal assemblages are dominated by non-keeled , globular forms—mainly hedbergellids . This interval corresponds to the benthic faunules III and IV of Lamolda & Peryt (1995) which are characteristic of low-oxygen bottom waters .

(3) An upper part approximately 27 . 5 m thick (samples GZ 56 to GZ 8) in which planktonic foraminifera diversify again and become very abundant ; both keeled and non-keeled forms occur . Within keeled morphogroups Dicarinella spp . dominate .

The change in morphotypic composition of planktonic foraminiferal fauna , e . g ., the extinction of species of Rotalipora and almost complete disappearance from assemblages of Dicarinella spp ., probably reflect changes in palaeoceanog- raphic conditions related to the CTBE .

Fossils in the Upper Cenomanian – Lower Turonian 339

The following planktonic foraminiferal events were identified in stratigraphic order from bottom upwards : LO of Rotalipora greenhornensis , sample G 26 (13 . 6 m) ; FO of Dicarinella spp ., sample G 19 (19 . 4 m) ; LO of Rotalipora cushmani , sample G 14 (22 . 2 m) ; FO of Helvetoglobotruncana praehelvetica , sample GZ 53 (9 . 4 m 5 13 . 3 m above G 14) ; FO of Helvetoglobotruncana helvetica , sample GZ 8 (38 . 8 m) .

The studied interval comprises the uppermost part of the Rotalipora cushmani Zone , which is characterized by occurrences of dif ferent species of Dicarinella , mainly Dicarinella algeriana (Figure 7s , t) and D . imbricata (Figure 7q , r) , but also D . elata (Figure 7i , j) , D . hagni (Figure 7l – n) , D . oraviensis (Figure 6q , r) , Globigerinelloides bentonensis (Figure 5q , r) , Guembelitria cenomana (Figure 5t) , Hedbergella delrioensis (Figure 7k) , H . planispira (Figures 5g , h ; 7o) , H . simplex (Figure 5a , b) , Heterohelix moremani (Figure 5p) , Praeglobotruncana aumalensis (Figure 6d , h) , P . delrioensis (Figure 7c , d) , P . gibba (Figure 6k , l , o , p) , P . stephani (Figure 6s , t) , Rotalipora greenhornensis (Figure 6a , c) , and common taxa such as Rotalipora cushmani (Figure 6e , g) , Whiteinella aprica (Figure 5i , j) , W . archaeocretacea (Figure 5o) , W . baltica (Figure 5k , l) , W . brittonensis (Figure 5c , d , m , n) , and W . paradubia (Figure 5e , f) , mainly in the upper part of the Rotalipora cushmani Zone .

The Whiteinella archaeocretacea Zone is dominated by the hedbergellids Hedbergella spp . and Whiteinella spp ., and a few Praeglobotruncana spp . Rare Dicarinella spp . are also found in the lower and middle parts (uppermost Cenomanian) of this zone . Main dif ferences from the underlying zone are occurrences of Helvetoglobotruncana praehelvetica (Trujillo) (Figure 6m , n) in most samples from the GZ sequence (Figures 2 , 4) , and no occurrences of rotaliporids , the LO of which marks the top of the Rotalipora cushmani Zone .

The FO of the species Helvetoglobotruncana helvetica (Figures 6i , j ; 7a , b) , lies in sample GZ 8 , at the top of the section studied . Therefore , the Whiteinella archaeocretacea Zone has a complete biostratigraphic record .

5 . Inoceramids

Inoceramid faunas are not abundant in the C / T transition at Ganuza . No characteristic Cenomanian inoceramid assemblages have been found . There are five levels in the Turonian with a record of inoceramids , and a lowermost level with Mytiloides submytiloides (Figure 8b) and Mytiloides sp . (sample GZ 56 ; 11 . 6 m) , of doubtful age but very close to the C / T boundary . It is possible to characterize two assemblages , the lower of which is a typical earliest Turonian inoceramid association .

5 . 1 . Mytiloides submytiloides Assemblage This is the oldest inoceramid assemblage recognized at Ganuza . It is defined by the first occurrence of the genus Mytiloides , and in particular of specimens of M . submytiloides and Mytiloides sp . (sample GZ 56) , and M . kossmati kossmati (GZ 57 , 1 m above GZ 56 ; Figures 4 ; 8c) . These species are associated with M . wiedmanni (Figure 8d) and M . cf . kossmati kossmati 8 . 4 m higher up the section (sample GZ 4 ; Figure 4) , which records an inoceramid event .

Figure 5 . a , b , Hedbergella simplex , G 26 ; c , d , Whiteinella brittonensis , G 26 ; e , f , W . paradubia , G 31 ; g , h , H . planispira (Tappan) , G 31 ; i , j , W . aprica , GZ 8 ; k , l , W . baltica , GZ 8 ; m , n , W . brittonensis , G 31 ; o , W . archaeocretacea , G 26 ; p , Heterohelix moremani , GZ 53 ; q , r , Globigerinelloides bentonensis , G 23 ; s , H . sp ., GZ 60 ; t , Guembelitria cenomana , G 23 . Scale bar 5 100 m m .

Fossils in the Upper Cenomanian – Lower Turonian 341

5 . 2 . Mytiloides kossmati ganuzaensis Assemblage The M . k . ganuzaensis Assemblage is defined by the FO of this subspecies . Unfortunately , it has not been found in the section studied , but it is frequent in nearby sections (Lo ́ pez , 1994 ; Martı ́ nez et al ., 1996) . By contrast , M . mytiloides (Figure 8a) , which is also characteristic of this assemblage , is present (samples GZ 6 and GZ 6a , about 12 m above GZ 4 ; Figure 4) . Therefore , the M . k . ganuzaensis Assemblage is probably indicated in the section studied , despite the absence of the nominate taxon . The uppermost inoceramid level with M . hercynicus (Figure 8e) and M . cf . transiens (sample GZ 8 , Figure 4) occurs about 7 m above the latter .

6 . Ammonoids

Ammonites are rare in the section ; only a few beds have yielded relatively rich assemblages (Figures 2 , 4) . It is dif ficult to distinguish a biozonation . Nevertheless , our data are of significance in the context of determining the C / T boundary .

Typical Upper Cenomanian species are recorded between samples G 22 and G 12 . The oldest species identified is Euomphaloceras septemseriatum (Figure 9b) from sample G 22 (17 . 3 m) associated to Calycoceras sp . and Forbeciceras sp . In sample G 12 , 7 . 5 m above sample G 22 , we found Protacanthoceras sp . and Thomelites sp . af f . hancocki (Figure 9a) . A specimen of Calycoceras naviculare , not recorded in situ , was found about 10 m above the occurrence of E . septemseriatum . This cosmopolitan species is typical of the Metoicoceras geslini- anum Zone in Europe , North Africa , Angola , Madagascar , Middle East , South India , Japan and the USA .

A specimen of Kamerunoceras sp . was identified in sample GZ 56 , and another specimen of Kamerunoceras calvertense (Figure 9c) in level GZ 57 / 58 , 5 m and 2 . 5 m respectively below the FO of Q . gartneri (sample GZ 1) , an index for the C / T boundary according to the proposals of Birkelund et al . (1984) . A specimen of Spathites ( Jeanrogericeras ) sp . was found in level GZ 59 (1 m below the FO of Q . gartneri ) .

All ammonites identified above the FO of Q . gartneri are clearly Turonian in age . In sample GZ 3 , 2 . 5 m above the FO of Q . gartneri , we found specimens of Mammites nodosoides (Figure 9d) and Spathites ( Jeanrogericeras ) obliquus . One metre above this sample Watinoceras sp . is recorded (GZ 4) , and 1 m higher , there is a level with Kamerunoceras puebloense , Fagesia cf . pachydiscoides , F . af f . rudra and Thomasites gr . gongilensis - koulavicus . A rich ammonite assemblage 11 m above (samples GZ 6 and GZ 6a) was found to comprise Scaphites ? sp ., Mammites ? sp ., Pachydesmoceras linderi , F . cf . pachydiscoides , K . puebloense , Lecointriceras fleuriasianum (Figure 9f) and Fagesia sp . F . pachydiscoides and Chof faticeras pavillieri (Figure 9 e) are recorded 1 . 8 m above this assemblage . At a higher level still , 5 m above (GZ 8 , at the top of the section studied) , F . af f . rudra and C . pavillieri have been found .

7 . Discussion

Occurrences of relevant biostratigraphical indicators for the C / T transition in the Ganuza section are summarized in Figure 10 . LOs of the foraminifers R . greenhornensis and R . cushmani , and the nannofossil A . albianus have been

Figure 6 . a – c , Rotalipora greenhornensis , G 26 ; d , h , Praeglobotruncana aumalensis , G 31 ; e – g , R . cushmani , G 26 ; i , j , Helvetoglobotruncana helvetica , GZ 8 ; k , l , P . gibba Klaus , G 31 ; m , n , H . praehelvetica , GZ 8 ; o , p , P . gibba , GZ 8 ; q , r , Dicarinella oraviensis , GZ 8 ; s , t , P . stephani , GZ 8 . Scale bar 5 100 m m .

Fossils in the Upper Cenomanian – Lower Turonian 343

calibrated with d 13 C curves from the literature and unpublished data from the Ganuza G section (C . R . C . Paul , pers . comm . ) . The FOs of the nannofossil Q . gartneri have also been calibrated with d 13 C data provide by Paul et al . (1994 ; following observations by Gale et al ., 1993) . Lithostratigraphical correlation between Anglo-Paris Basin localities have been used , especially within the Plenus Marls .

7 . 1 . Planktonic foraminifera and nannofossils Planktonic foraminifera and nannofossil occurrences characterize the C / T transition and its completeness (Lamolda et al ., 1994) . Graphic correlation between Menoyo and Dover (Shakespeare Clif f) revealed the completeness and similar pattern of deposition in these localities (Paul et al ., 1994) . This can be extended to the Ganuza section studied because of its similarity with Menoyo (Lamolda & Peryt , 1995 ; Lamolda & Gorostidi , 1996) . Two of our bioevents , LOs of R . cushmani and A . albianus , were used by Gale et al . (1993) to compare bioevents and d 13 C for Eastbourne and Pueblo , showing their usefulness on both sides of the Atlantic Ocean . Nevertheless , LOs of both R . greenhornensis and R . cushmani at Pueblo are younger than elsewhere (Figure 10) . This rotaliporid persistence continues with the record of endemic Anaticinella in the Western Interior Basin (USA) during Late Cenomanian . This region was a refuge for rotaliporids , which had disappeared by this time elsewhere . Successive LOs of L . acutus , R . cushmani and M . chiastius , and FOs of Q . intermedium , H . praehelvet- ica and Q . gartneri , characterize sediments from Upper Cenomanian ( Metoicoceras geslinianum Zone) to lowermost Turonian ( Watinoceras devonense Zone) All occurred during the d 13 C excursion of the C / T transition .

Unfortunately , these bioevents have not been well documented in the proposed C / T boundary stratotype at the Rock Canyon Anticline section , Pueblo (Bengt- son , 1996) which , by contrast , favours macrofaunal events .

7 . 2 . Inoceramids The first occurrence of the genus Mytiloides is useful for recognizing the C / T boundary (Seibert , 1979 ; Tro ̈ ger , 1981 ; Birkelund et al ., 1984) . On a broad scale , the basal Turonian of North America and Europe is characterized by occurrences of M . submytiloides . Tro ̈ ger (1989) cited his Zone 8 (Lower Turonian) as the stratigraphical range of this species . This species has also been found in southeast France (Jolet et al ., 1995) associated with M . kossmati ganuzaensis , which is a Lower Turonian species . Nevertheless , some authors , such as Harries et al . (1996) , have considered that M . submytiloides may occur in uppermost Cenomanian rocks .

M . wiedmanni is found in the GZ section at Ganuza just above the FO of M . nodosoides (Figures 4 , 10) . In addition , we have recently also found some specimens of M . wiedmanni in Lower Turonian rocks of the Menoyo section . This species in the lowermost Turonian of Saumurois , western France was referred to as Inoceramus hercynicus by Sornay (1982) . Moreover , it has been identified in Cassis , southeast France (Lo ́ pez , in prep . ) associated with M . submytiloides , and in the lowermost Turonian of the Bohemian Basin (S . Cech , pers . comm ., 1995) . M . wiedmanni is a widespread species and also occurs at Pueblo (Bengtson , 1996) , associated with M . hattini and very close to the LO of Neocardioceras judii and the FO of Kamerunoceras sp . —less than 1 m below Bed

Figure 7 . a , b , Helvetoglobotruncana helvetica , GZ 8 ; c , d , Praeglobotruncana delrioensis , GZ a ; e , f , P . sp ., G 31 ; g , h , P . sp ., GZ a ; i , j , Dicarinella elata , GZ 57a ; k , Hedbergella delrioensis , GZ 7 ; l , p , D . hagni , G 26 ; m , n , D . hagni , GZ 59 ; o , H . planispira , G 23 ; q , r , D . imbricata , GZ 7b ; s , t , D . algeriana , GZ 8 . Scale bar 5 100 m m .

Fossils in the Upper Cenomanian – Lower Turonian 345

Figure 8 . a , Mytiloides mytiloides , right valve of the specimen PalUAB no . 38222 ; b , M . submytiloides , left valve of the specimen PalUAB no . 38711 ; c , M . kossmati kossmati , right valve of the specimen PalUAB no . 38847 ; d , M . wiedmanni , left valve of the specimen PalUAB no . 38764 ; e , M . hercynicus , left valve of the specimen PalUAB no . 38490 . Scale bar 5 1 cm .

M . A . Lamolda et al . 346

Fossils in the Upper Cenomanian – Lower Turonian 347

86 of the proposed C / T boundary stratotype . Therefore , its range is from uppermost Cenomanian to Lower Turonian (Figure 10) .

The species M . k . kossmati had been found in the Ganuza section studied (GZ 57 and GZ 4 ; Figure 4) and in a neighbouring section ( 5 Inoceramus ( Mytiloides ) goppelnensis goppelnensis ; Lamolda et al ., 1989 , text-fig . 2) . It is present in Lower Turonian deposits at Bastide de Virac , Gard , southeast France (Lo ́ pez , in prep . ) , and at Cassis (Jolet et al ., 1995) . Tro ̈ ger (1989) gave its stratigraphical range in western Europe as lower Middle Turonian . This wider range is in agreement with data reported by Lo ́ pez (1992) and Walaszczyk (1992) , and correlates with middle and upper parts of the Watinoceras coloradoense Zone .

Therefore , sample GZ 57 should be of earliest Turonian age , and we can conclude that M . submytiloides and M . wiedmanni associated with M . k . kossmati in sample GZ 4 , just above M . nodosoides , represents a Lower Turonian assemblage . But the presence of only a few specimens of M . submytiloides in sample GZ 56 (1 m below GZ 57) does not allow us to distinguish between uppermost Cenomanian or lowermost Turonian in this bed .

7 . 3 . Ammonites Euomphaloceras septemseriatum and Calycoceras naviculare are largely known as cosmopolitan species , characteristic of the Upper Cenomanian Metoicoceras geslinianum Zone elsewhere (Wright & Kennedy , 1990 , p . 294 and Kennedy & Juignet , 1981 , p . 38 , respectively) . The ammonite fauna from samples G 22 to G 12 should belong to this Upper Cenomanian ammonite zone .

The exact location of the C / T boundary cannot be identified by ammonites at Ganuza , but we recognize its approximate position to be very close to the FO of Kamerunoceras —a specimen of Kamerunoceras sp . was recorded from sample GZ 56—and level GZ 57 / 58 , where Kamerunoceras calvertense occurs 2 . 5 m above . Kamerunoceras is a typical Turonian taxon , although there are occurrences in uppermost Cenomanian deposits , e . g ., in bed 84 of the Bridge Creek Limestone Member of the Pueblo section , just 1 m below the FO of Watinoceras devonense (Kennedy & Cobban , 1991) . Moreover , Kamerunoceras appears to have been derived from typical Upper Cenomanian E . septemseriatum (Wright & Kennedy , 1981 , p . 56) , which is recorded from both the Pueblo and Ganuza sections below the first occurrence of Kamerunoceras . The species K . calvertense , associated with Pseudaspidoceras flexuosum in a condensed bed , is known only in west Texas , USA and northern Chihuahua , Mexico (Kennedy et al ., 1987) . These authors noted its primitive characteristics , which are close to Upper Cenomanian Acanthoceratinae .

Successive upwards occurrences of Kamerunoceras sp . and M . submytiloides (GZ 56) , M . k . kossmati (GZ 57) and K . calvertense (GZ 57 / 58 ; Figures 4 , 10) are similar to those in the Pueblo sequence , where Kamerunoceras sp . is associated with N . judii , and abundant Mytiloides ( M . hattini ; Elder , 1991 ; M . wiedmanni , Bengtson , 1996) , all below the FO of W . devonense , which is overlain by a P .

Figure 9 . a , Thomelites sp . af f . hancocki , lateral view of the specimen PalUAB no . 47894 , G 12 ; b , Euomphaloceras septemseriatum , ventral view of the specimen PalUAB no . 12419 , G 22 ; c , Kamerunoceras calvertense , ventral view of the specimen PalUAB no . 12415 , GZ 57-58 ; d , Mammites nodosoides , lateral view of the specimen PalUAB no . 47860 , GZ 3 ; e , Chof faticeras pavillieri , lateral view of the specimen PalUAB no . 12122 , GZ 6 top ; f , Lecointriceras fleuriasianum , lateral view of the specimen PalUAB no . 12116 , GZ 6b . Scale bar 5 1 cm .

M . A . Lamolda et al . 348

Figure 10 . Relative position of key bioevents associated with the C / T boundary according to several authors . Vertical scale arbitrary (Ganuza , this paper ; Shakespeare Clif f after Lamolda et al ., 1994 ; Dover after Jarvis et al ., 1988 ; Pueblo after Kennedy & Cobban , 1991 and Bengtson , 1996 ; Texas after Kennedy et al ., 1987 ; B 5 Boulonnais after Robaszynski et al ., 1980) .

Fossils in the Upper Cenomanian – Lower Turonian 349

flexuosum assemblage , the latter recording the species K . calvertense in West Texas (see above) . Furthermore , in the Ganuza section (Figures 4 , 10) Q . gartneri and M . nodosoides occur above K . calvertense . Hence , the GZ 57 / 58 level with K . calvertense should be lowermost Turonian , and GZ 56 , 2 . 5 m lower with Kamerunoceras sp . and M . submytiloides , should be uppermost Cenomanian ; this is consistent with the FO of M . k . kossmati between both levels (see 7 . 2 above) .

Lower Turonian sediments can be identified by species such as M . nodosoides and S . ( J . ) obliquus . The latter species cannot be used for worldwide correlation as it is endemic to the Bascocantabrian Region . It has been found in localities at Arenillas and Soncillo , Burgos (Karrenberg , 1935 , p . 136) , Puentedey , Burgos (Santamarı ́ a , 1995 , p . 47) as well as in the Ganuza section , but M . nodosoides is characteristic of its nominate zone , from late Early Turonian (Chancellor et al ., 1994) . Therefore , we have an interval in the lowermost Turonian with very few ammonites , which is similar to Kalaat Senan , Tunisia (Robaszynski et al ., 1990) , central Tunisia (Chancellor et al . , 1994) and Touraine , France (Hancock et al ., 1993) . K . puebloense and C . pavillieri occur in the Pueblo section below the FO of M . nodosoides (Figure 10) , and C . pavillieri is recorded from the Thomasites rollandi Zone in central Tunisia (Chancellor et al ., 1994) , which is also below the FO of M . nodosoides . The Turonian species Lecointriceras fleuriasianum has been reported from several localities in Lower Turonian beds (Lamolda et al ., 1989) . We have not , therefore , recognized a definitive Middle Turonian ammonoid assemblage .

8 . Conclusions

The Cenomanian / Turonian boundary in the Ganuza section should lie within the 1-m-thick interval between samples GZ 56 and GZ 57 . A good proxy for this boundary is the FOs of both Mytiloides kossmati kossmati and Kamerunoceras spp . Successive LOs of Lithraphites acutus , Rotalipora cushmani and Microstaurus chiastius , and FOs of Quadrum intermedium , Helvetoglobotruncana praehelvetica and Quadrum gartneri characterize the completeness of C / T transitions and may be a good proxy for the C / T boundary .

The FO of H . praehelvetica in levels coeval with Kamerunoceras sp . and Mytiloides submytiloides , and below FO of M . k . kossmati , is a good index for characterizing the C / T boundary . Although earlier records of Q . gartneri might have been overlooked , its FO is recorded below Mamnites nodosoides but above Mytiloides submytiloides , H . praehelvetica , M . kossmati kossmati and Kamerunoceras calvertense . It is , therefore , a good proxy for the C / T boundary .

Acknowledgements

We are indebted to David Batten , Chris Paul and an anonymous referee for their critical remarks , which have improved this manuscript . The financial support for this project to D . Peryt was provided by a research grant of the Programa de Perfeccionamiento y Movilidad del Personal Investigador / 1994 of the Basque Government . The SEM photographs of the foraminifera were taken in the Institute of Palaeobiology , Polish Academy of Sciences , Warsaw . This is a contribution to the DGICYT project nos . PS90-91 and PB95-0505-C02 , MEC .

M . A . Lamolda et al . 350

References

Bengtson , P . 1996 . The Turonian stage and substages boundaries . In Proceedings , Second International Symposium on Cretaceous Stage Boundaries (eds Rawson , P . F ., Dhondt , A . V ., Hancock , J . M . and Kennedy , W . J . ) . Bulletin de l ’ Institut Royal des Sciences Naturelles de Belgique , Sciences de la Terre 66 , supplement , 69 – 79 .

Birkelund , T ., Hancock , J . M ., Hart , M . B ., Rawson , P . F ., Remane , J ., Robaszynski , F ., Schmid , F . & Surlyk , F . 1984 . Cretaceous stage boundaries—proposals . Bulletin of the Geological Society of Denmark 33 , 3 – 20 .

Bralower , T . J . 1988 . Calcareous nannofossil biostratigraphy and assemblages of the Cenomanian – Turonian boundary interval : implications for the origin and timing of oceanic anoxia . Paleoceanography 3 , 275 – 316 .

Chancellor , G . R ., Kennedy , W . J . & Hancock , J . M . 1994 . Turonian ammonite faunas from central Tunisia . Special Papers in Palaeontology 50 , 1 – 118 .

Colin , J . -P ., Lamolda , M . A . & Rodrı ́ guez Lazaro , J . M . 1982 . Los ostracodos del Cenomaniense superior y Turoniense de la Cuenca Vasco-Canta ́ brica . Revista Espan ̃ ola de Micropaleontologı ́ a 14 , 187 – 220 .

Crux , J . A . 1982 . Upper Cretaceous (Cenomanian to Campanian) calcareous nannofossils . In Stratigraphical index of calcareous nannofossils (ed . A . R . Lord) , pp . 81 – 135 (British Micropaleon- tological Society , Special Publication ; Ellis Horwood , Chichester) .

Dennison , J . M . & Hay , W . W . 1967 . Estimating the needed sampling area for subaquatic ecologic studies . Journal of Paleontology 41 , 706 – 708 .

Deres , R . & Ache ́ rite ́ guy , J . 1980 . Biostratigraphie des Nannoconide ́ s . Bulletin des Centres de Recherches Exploration - Production Elf - Aquitaine 4 , 1 – 53 .

Elder , W . P . 1991 . Mytiloides hattini n . sp . A guide fossil for the base of the Turonian in the Western Interior of North America . Journal of Paleontology 65 , 234 – 241 .

Gale , A . S ., Jenkyns , H . C ., Kennedy , W . J . & Corfield , R . M . 1993 . Chemostratigraphy versus biostratigraphy : data from around the Cenomanian – Turonian boundary . Journal of the Geological Society , London 150 , 29 – 32 .

Gorostidi , A . 1993 . Nanofo ́ siles calca ́ reos y eventos del Creta ́ cico Medio - Superior de la Regio ́ n Vascocanta ́ brica . Tesis Doctoral , Universidad del Paı ́ s Vasco , pp . 1 – 331 . [Unpublished]

Gorostidi , A . & Lamolda , M . A . 1991 . El paso Cenomaniense-Turoniense de Menoyo (Alava) : variaciones de la nanoflora calca ́ rea . Geogaceta 10 , 54 – 57 .

Hancock , J . M ., Kennedy , W . J . & Cobban , W . A . 1993 . A correlation of the Upper Albian to basal Coniacian sequences of northwest Europe , Texas and the United States Western Interior . In Evolution of the Western Interior Basin (eds Caldwell W . G . E . & Kauf fman , E . G . ) , Geological Association of Canada , Special Paper 39 , 453 – 476 .

Harries , P . J ., Kauf fman , E . G . & Crampton , J . S . (eds) , and Bengston , P ., Cech , S ., Crame , J . A ., Dhondt , A . V ., Ernst , G ., Hilbrecht , H ., Lo ́ pez , G ., Mortimore , R ., Tro ̈ ger , K . A ., Walaszczyk , I . & Wood , C . J . 1996 . Lower Turonian Euramerican Inoceramidae : a mor- phologic , taxonomic , and biostratigraphic overview . Proceedings , 4 th International Cretaceous Symposium (ed . Spaeth , C . ) , Mitteilungen Geologisches - Pala ̈ ontologiches Institut , Universita ̈ t Ham- burg 77 , 641 – 668 .

Jarvis , J ., Carson , G . A ., Hart , M . B ., Leary , P . N ., Tocher , B . A ., Horne , D . & Rosenfeld , A . 1988 . Microfossil assemblages and the Cenomanian – Turonian (Late Cretaceous) Oceanic Anoxic Event . Cretaceous Research 9 , 3 – 103 .

Jolet , P ., Thomel , G ., Philip , J ., Lo ́ pez , G ., Tronchetti , G . & Babinot , J . F . 1995 . New biostratigraphical data on the Cenomanian – Turonian boundary on the South Provence Basin (S . E . France) : the Cassis section . Abstracts , 2 nd International Symposium on Cretaceous Stage Boundaries , p . 61 (Brussels) .

Karrenberg , H . 1935 . Ammonitenfaunen aus der Nordspanischen oberkreide . Palaeontographica A 82 , 125 – 161 .

Kennedy , W . J . & Cobban , W . A . 1991 . Stratigraphy and interregional correlation of the Cenomanian – Turonian transition in the Western Interior of the United States near Pueblo , Colorado , a potential boundary stratotype of the base of the Turonian Stage . Newsletters on Stratigraphy 24 , 1 – 33 .

Kennedy , W . J . & Juignet , P . 1981 . Upper Cenomanian ammonites from the environs of Saumur , and the provenance of types of Ammonites vibrayeanus and Ammonites geslinianus . Cretaceous Research 2 , 19 – 49 .

Kennedy , W . J ., Wright , C . W . & Hancock , J . M . 1987 . Basal Turonian ammonites from West Texas . Palaeontology 30 , 27 – 74 .

Lamolda , M . A . 1978 . Le passage Ce ́ nomanien-Turonien dans la Coupe de Menoyo (Ayala , Alava) . Cahiers de Micropale ́ ontologie 1978 (4) , 21 – 27 .

Lamolda , M . A . 1982 . Le Turonien Basco-Cantabrique et ses faunes caracteristiques . Me ́ moires du Museum National d ’ Histoire Naturelle C49 , 101 – 112 .

Lamolda , M . A . & Gorostidi , A . 1996 . Calcareous nannofossils at the Cenomanian – Turonian

Fossils in the Upper Cenomanian – Lower Turonian 351

Boundary Event in the Ganuza Section , northern Spain . In Prof . L . Rama Rao - IGCP 3 5 0 Volume , The Geological Society of India , Memoir 37 , 251 – 265 .

Lamolda , M . A ., Gorostidi , A . & Paul , C . R . C . 1994 . Quantitative estimates of calcareous nannofossil changes across the Plenus Marls (latest Cenomanian) , Dover , England : implications for the generation of the Cenomanian – Turonian Boundary Event . Cretaceous Research 15 , 143 – 164 .

Lamolda , M . A ., Gorostidi , A ., Paul , C . R . C ., Mitchell , S . & Vaziri , R . 1996 . Late Cenomanian microfossil assemblages at Eastbourne (S . England) : their response to the Cenomanian – Turonian Boundary Event . Abstracts , 3 0 th International Geological Congress , Beijing 2 – 3 , 66 .

Lamolda , M . A ., Lo ́ pez , G . & Martı ́ nez , R . 1989 . Turonian integrated biostratigraphy in the Estella Basin (Navarra , Spain) . In Cretaceous of the Western Tethys (ed . Wiedmann , J . ) , pp . 145 – 159 (Schweizerbart’sche , Stuttgart) .

Lamolda , M . A . & Peryt , D . 1995 . Benthonic foraminiferal response to the Cenomanian – Turonian boundary event in the Ganuza section , northern Spain . Revista Espan ̃ ola de Paleontologı ́ a , Homenaje al Dr . Guillermo Colom (ed . Lamolda , M . A . ) , pp . 101 – 118 .

Lo ́ pez , G . 1990 . Inocera ́ midos ( Bivalvia ) del Creta ́ cico Superior de la Cuenca Navarroca ́ ntabra y la Plataforma Norcastellana . Paleontologı ́ a y bioestratigrafı ́ a . Tesis Doctoral , Universidad Auto ́ noma de Barcelona , pp . 1 – 515 . [Unpublished]

Lo ́ pez , G . 1992 . Paleontologı ́ a y bioestratigrafı ́ a de los inocera ́ midos (Bivalvia) del Creta ́ cico Superior de la Cuenca Navarroca ́ ntabra y de la Plataforma Norcastellana . Parte II : Estudio sistema ́ tico de los subge ́ neros Mytiloides Brongniart y Magadiceramus Seitz . Boletı ́ n Geolo ́ gico y Minero 103 , 478 – 543 .

Lo ́ pez , G . 1994 . Bioestratigrafı ́ a de los inocera ́ midos (Bivalvia) de la Cuenca Navarroca ́ ntabra y de la Plataforma Norcastellana . Comparacio ́ n con zonaciones de otras a ́ reas de Europa . Cuadernos de Geologı ́ a Ibe ́ rica 18 , 309 – 336 .

Martı ́ nez , R ., Lamolda , M . A ., Gorostidi , A ., Lo ́ pez , G . & Santamarı ́ a , R . 1996 . Bioestratigrafı ́ a integrada del Creta ́ cico Superior de la Regio ́ n Vascocanta ́ brica . Revista Espan ̃ ola de Paleontologı ́ a n o extraord . , 160 – 171 .

Paul , C . R . C ., Mitchell , S ., Lamolda , M . & Gorostidi , A . 1994 . The Cenomanian – Turonian Boundary Event in northern Spain . Geological Magazine 131 , 801 – 817 .

Robaszynski , F . & Amedro , F . (coord . ) , and Foucher , J . C ., Gaspard , D ., Magniez-Jannin , F ., Manivit , H . & Sornay , J . 1980 . Synthe ̀ se biostratigraphique de l’Aptien au Santonien du Boulonnais a ̀ partir de sept groupes pale ́ ontologiques : foraminife ̀ res , nannoplankton , dinoflagelle ́ s et macrofaunes . Zonations micropale ́ ontologiques inte ́ gre ́ es dans le cadre du Cre ́ tace ́ bore ́ al nord-europe ́ en . Revue de Micropale ́ ontologie 22 , 195 – 321 .

Robaszynski , F ., Caron , M ., Dupuis , Ch ., Amedro , F ., Gonza ́ lez Donoso , J . M ., Linares , D ., Hardenbol , J ., Gartner , S ., Calandra , F . & Delof fre , R . 1990 . A tentative integrated stratigraphy in the Turonian of central Tunisia : formations , zones and sequential stratigraphy in the Kalaat Senan area . Bulletin des Centres de Recherches Exploration - Production Elf - Aquitaine 14 , 213 – 384 .

Santamarı ́ a , R . 1991 . Ammonoideos del Creta ́ cico Superior de la Plataforma Norcastellana y parte de la Cuenca Navarroca ́ ntabra . Paleontologı ́ a y Bioestratigrafı ́ a . Tesis Doctoral , Universidad Auto ́ noma de Barcelona , pp . 1 – 397 . [Unpublished]

Santamarı ́ a , R . 1995 . Los ammonoideos del Cenomaniense superior al Santoniense de la plataforma nord-castellana y la cuenca navarroca ́ ntabra . Parte II . Sistema ́ tica : Acanthocerataceae . Treballs del Museu de Geologia de Barcelona 4 , 15 – 131 .

Seibert , E . 1979 . Biostratigraphie im Turon des SE-Mu ̈ nsterlandes und Aupassung an die internationale Gliederung aufgrund von Vergleichen mit anderen Oberkreide-Gebieten . Newsletters on Stratigraphy 8 , 111 – 123 .

Sornay , J . 1982 . Inoceramus du Saumourois . In Le Turonien de la re ́ gion - type : Saumourois et Touraine . Stratigraphie , biozonations , se ́ dimentologie (eds Robaszynski , F ., Alcayde G ., Amedro , F ., Badillet , G ., Damotte , R ., Foucher , J . C ., Jardine ́ , S ., Legoux , O ., Manivit , H ., Monciardini , C . & Sornay , J . ) , Bulletin des Centres de Recherches Exploration - Production Elf - Aquitaine 6 , 138 – 140 .

Tro ̈ ger , K . A . 1981 . Zu Problemen des Biostratigraphie der Inoceramen und der Untergliederung des Cenomans und Turons in Mittel- und Osteuropa . Newsletters on Stratigraphy 9 , 139 – 156 .

Tro ̈ ger , K . A . 1989 . Problems of Upper Cretaceous inoceramid biostratigraphy and paleobiogeog- raphy in Europe and Western Asia . In Cretaceous of the Western Tethys . Proceedings , 3rd International Cretaceous Symposium (ed . Wiedmann , J . ) , pp . 911 – 930 (Schweizerbart’sche , Stuttgart) .

Varol , O . 1992 . Taxonomic revision of the Polycyclolithaceae and its contribution to Cretaceous biostratigraphy . Newsletters on Stratigraphy 27 , 93 – 127 .

Walaszczyk , I . 1992 . Turonian through Santonian deposits of the Central Polish Uplands ; their facies development , inoceramid paleontology and stratigraphy . Acta Geologica Polonica 42 , 1 – 122 .

Wiedmann , J . 1980 . Itineraire ge ́ ologique a ̀ travers le Cre ́ tace ́ moyen des chaines vascogotiques et celtibe ́ riques (Espagne du Nord) . Cuadernos de Geologı ́ a Ibe ́ rica 5 , 127 – 214 .

Wright , C . W . & Kennedy , W . J . 1981 . The ammonoidea of the Plenus Marls and the Middle Chalk . Palaeontographical Society Monographs 134 , 148 pp .

M . A . Lamolda et al . 352

Wright , C . W . & Kennedy , W . J . 1990 . The Ammonoidea of the Lower Chalk . Part 3 . Palaeontographical Society Monographs 144 , 219 – 294 .

Zeighampour , M . R . 1981 . Biozonation du Cre ́ tace ́ (Albien-Santonien) a ̀ partir des coccolithes des craies de Haute-Normandie (France) . Revue de Micropale ́ ontologie 24 , 172 – 186 .

Appendix

The fossils used in this study have been deposited in the collections of M . A . Lamolda (microfossils) and the Departament de Geologia , Universita ̀ t Autonoma de Barcelona (macrofauna) .

List of species mentioned in text with authors and dates

Nannofossils Allemanites striatus (Stradner) , 1963 ( Arkhangelskiella ) Axopodorhabdus albianus (Black) , 1967 ( Podorhabdus ) Braadurosphaera regularis Black , 1973 Broinsonia enormis (Shumenko) , 1968 ( Arkhangelskiella ) B . signata (Noe ̈ l) , 1969 ( Aspidolithus ) Corollithion kennedyi Crux , 1981 C . signum Stradner , 1963 Cretarhabdus conicus Bramlette & Martini , 1964 Cribrosphaerella ehrenbergii (Arkhangelsky) , 1912 ( Cribrosphaera ) Discorhabdus ignotus (Gorka) , 1957 ( Tremalithus ) Eif fellithus turriseif felii (Deflandre) , 1954 ( Zygolithus ) Eprolithus eptapetalus Varol , 1992 E . floralis (Stradner) , 1962 ( Lithastrinus ) E . octopetalus Varol , 1992 Gartnerago obliquum (Stradner) , 1963 ( Arkhangelskiella ) Glaukolithus compactus (Bukry) , 1969 ( Zygodiscus ) Haqius circumradiatus (Stover) , 1966 ( Coccolites ) Helicolithus traveculatus (Gorka) , 1957 ( Discolithus ) Lithraphidites acutus Verbeek & Manivit , 1977 L . carniolensis Deflandre , 1963 Loxolithus armilla (Black) , 1959 (Cyclolithus) Mannivitella pemmatoidea (Deflandre) , 1965 ( Cricolithus ) Microrhabdulus belgicus Hay & Towe , 1963 M . decoratus Deflandre , 1959 Microstaurus chiastius (Worsley) , 1971 ( Helenea ) Nannoconus elongatus Bro ̈ nnimann , 1955 N . multicadus Deflandre & Deflandre-Rigaud , 1959 N . truitti truitti Bro ̈ nnimann , 1955 Prediscosphaera avitus (Black) , 1973 ( Deflandrius ) P . cretacea (Arkhangelsky) , 1912 ( Coccolithophora ) P . ponticula Bukry , 1969 P . spinosa (Bramlette & Martini) , 1964 ( Deflandrius ) Quadrum gartneri Prins & Perch-Nielsen , 1977 Q . intermedium Varol , 1992 Raghodiscus achlyostaurion (Hill) , 1976 ( Parhabdolithus ) R . angustus (Stradner) , 1963 ( Parhabdolithus ) R . asper (Stradner) , 1963 ( Discolithus ) Rotelapillus laf fittei (Noe ̈ l) , 1957 ( Stephanolithion ) Stoverius achylosus (Stover) , 1966 ( Chiphragmalithus ) Tranolithus exiguus Stover , 1966 T . gabalus Stover , 1966 T . minimus (Bukry) , 1969 (Zygodiscus) T . phacelosus Stover , 1966 Watznaueria barnesae (Black) , 1969 ( Tremalithus ) W . biporta Bukry , 1969 W . ovata Bukry , 1969 Zeugrhabdotus acanthus Reinhardt , 1965 Z . elegans (Gartner) , 1968 ( Zygodiscus ) Z . embergeri (Noe ̈ l) , 1958 ( Discolithus )

Foraminifera Dicarinella algeriana (Caron) , 1966 ( Praeglobotruncana ) D . elata Lamolda , 1977

Fossils in the Upper Cenomanian – Lower Turonian 353

D . hagni (Scheibnerova) , 1962 ( Praeglobotruncana ) D . imbricata (Mornod) , 1949 ( Globotruncana ) D . oraviensis (Scheibnerova) , 1960 ( Praeglobotruncana ) Globigerinelloides bentonensis (Morrow) , 1934 ( Anomalina ) Guembelitria cenomana Keller , 1935 Hedbergella delrioensis (Carsey) , 1926 ( Globigerina ) H . planispira (Tappan) , 1940 ( Globigerina ) H . simplex (Morrow) , 1934 ( Hastigerinella ) Helvetoglobotruncana helvetica (Bolli) , 1945 ( Globotruncana ) H . praehelvetica (Trujillo) , 1960 ( Rugoglobigerina ) Heterohelix moremani (Cushman) , 1938 ( Guembelina ) Praeglobotruncana aumalensis (Sigal) , 1952 ( Globigerina ) P . delrioensis (Plummer) , 1931 ( Globorotalia ) P . gibba Klaus , 1960 P . stephani (Gandolfi) , 1942 ( Globotruncana ) Rotalipora cushmani (Morrow) , 1934 ( Globorotalia ) R . greenhornensis (Morrow) , 1934 ( Globorotalia ) Whiteinella aprica (Loeblich & Tappan) , 1961 ( Ticinella ) W . archaeocretacea Pessagno , 1967 W . baltica Douglas & Rankin , 1969 W . brittonensis (Loeblich & Tappan) , 1961 ( Hedbergella ) W . paradubia (Sigal) , 1952 ( Globigerina )

Inoceramids

Inoceramus gr . labiatus (Schlotheim) , 1813 ( Ostracites ) Mytiloides hattini Elder , 1991 M . hercynicus (Petrascheck) , 1903 ( Inoceramus ) M . kossmati ganuzaensis Lo ́ pez , 1992 M . kossmati kossmati (Heinz) , 1933 ( Striatoceramus ) M . mytiloides (Mantell) , 1822 ( Inoceramus ) M . submytiloides (Seitz) , 1934 ( Inoceramus ) M . cf . transiens (Seitz) , 1934 ( Inoceramus ) M . wiedmanni Lo ́ pez , 1992

Ammonites

Calycoceras naviculare (Mantell) , 1822 ( Ammonites ) Chof faticeras pavillieri (Pervinquie ̀ re) , 1907 ( Pseudotissotia ) Euomphaloceras septemseriatum (Cragin) , 1893 ( Scaphites ) Fagesia pachydiscoides Spath , 1925 F . af f . rudra (Stoliczka) , 1865 ( Ammonites ) Kamerunoceras calvertense (Powell) , 1963 ( Acanthoceras ) K . puebloense (Cobban & Scott) , 1972 ( Kanabiceras ) Lecointriceras fleuriasianum (D’Orbigny) , 1841 ( Ammonites ) Mammites nodosoides (Schlu ̈ ter) , 1871 ( Ammonites ) Neocardioceras judii (Barrois & Guerne) , 1878 ( Ammonites ) Pachydesmoceras linderi (Grossouvre) , 1894 ( Pachydiscus ) Pseudaspidoceras flexuosum Powell , 1963 Spathithes ( Jeanrogericeras ) obliquus (Karrenberg) , 1935 ( Mammites ) Thomelites sp . af f . T . hancocki Juignet & Kennedy , 1976 Watinoceras devonense Wright & Kennedy , 1981