 Geologia Croatica 65/3 393–410 5 Figs. 2 Tabs. 2 Pls. Zagreb 2012 Ab sTrA CT This work is the first attempt to undertake a biostratigraphic study on calcareous nannofossil assemblages of the exposed Upper Cretaceous to Lower Eocene rocks at the Malaqet and Mundassah sections, western flank of the Northern Oman Mountains. The Upper Cretaceous to Lower Eocene rocks belong to the Simsima Formation and the Muthaymimah Formation. Specimens of calcareous nannofossils identified during this study have been ascribed to 67 different species. The Cretaceous/Palaeocene boundary can be placed in correspondence with the unconformity between the mentioned formations. The presence of a big hiatus in this area is suggested by the absence of the latest Maastrichtian Micula prinsii nannofossil Zone, and the Palaeocene NP1 and NP2 nannofossil Zones. In the two study sections, the Danian/Selandian boundary is placed at the level of the first occurrence (FO) of Fasciculithus tympaniformis (base of NP5 Zone). At Jabal Mundassah, the Selandian/Thanetian boundary is positioned at the FO of Discoaster mohleri, which is used to define the base of NP7/8 Zone. Unfortunately, a major hiatus is detected at the Selandian/Thanetian boundary at the Jabal Malaqet section as indicated by the absence of NP6 and NP7/8 Zones. The Paleocene/Eocene boundary is placed at the base of Subzone NP9b at Jabal Mundassah, whereas at Jabal Malaqet the Paleocene/Eocene boundary interval is missing and a major hiatus is testified by the absence of the NP9b Sub- zone and NP10 Zone. Keywords: Jabals: Malaqet and Mundassah, Calcareous Nannofossils, Simsima Formation, Muthaymimah Formation, Upper Cretaceous, Paleocene, Lower Eocene, Biostratigraphy, Northern Oman Mountains Upper Cretaceous to Lower Eocene calcareous nannofossil biostratigraphy from Malaqet and Mundassah sections western flank of the Northern Oman Mountains  Mahmoud Faris1 Osman Abdelghany2 and Mahmoud Abu Saima2 1 Geology Department, Faculty of Science, Tanta University, Tanta, Egypt; (corresponding author: mhmfaris@yahoo.com) 2 Geology Department, Faculty of Science, United Arab Emirates University, Al-Ain, P.O. Box 17551, United Arab Emirates doi: 104154/gc.2012.29 1. INTrODUCTION The Upper Cretaceous – Lower Eocene rocks are widely ex- posed in the western foothills of the Northern Oman Moun- tains (Fig. 1). Upper Cretaceous rocks are the oldest units lying unconformably upon the Semail Ophiolite and folded, thrusted Hawasina and Sumeini groups of Permian-Late Cretaceous age (GLENNIE et al., 1974, and WILSON, 2000). The stratigraphy and facies of the Upper Cretaceous- Eocene Neoautochthonous sequence of the Northern Oman Mountains have been discussed in numerous papers, includ- ing GLENNIE et al. (1974); HAMDAN (1990); Al SHARHAN & KENDALL (1991); ANAN (1993); NOWEIR & EL OUTEFI (1997); NOWEIR et al. (1998); SAYED & MERSAL (1998); BOUKHARY et al. (1999); ALSHARHAN et al. (2000); NOWEIR & ABDEEN (2000); ABD-ALLAH Geologia CroaticaGeologia Croatica Geologia Croatica 65/3Geologia Croatica 394 Figure 1: Simplified geologic map (modified from ABDEL-GAWAD et al., 2010 showing the location of the studied sections. Figure 2: Field photographs of the study area: 1, 2 – Jabal Mundassah; 3, 4 – Jabal Malaqet. Faris et al.: Upper Cretaceous to Lower Eocene calcareous nannofossil biostratigraphy from Malaqet and Mundassah sections... Geologia Croatica 395 Figure 3: Lithostratigraphic description of Jabal Malaqet section. Geologia Croatica 65/3Geologia Croatica 396 Figure 4: Lithostratigraphic description of Jabal Mundassah section. Faris et al.: Upper Cretaceous to Lower Eocene calcareous nannofossil biostratigraphy from Malaqet and Mundassah sections... Geologia Croatica 397 (2001); WILSON & TAYLOR (2001); ABDELGHANY (2003); BAGHDADY & ABU-ZEID (2003); SHEBL (2004) and ABDEL GAWAD et al. (2010). Discussion of the calcareous nannofossil biostratigraphy of Upper Cretaceous to Lower Eocene rock units (Simsima and Muthaymimah formations) cropping out at Jabals Malaqet and Mundassah is presented here. In addition, an attempt is made to identify the Maastrichtian/Danian, Da- nian/Selandian, Selandian/Thanetian and the Thanetian/ Ypresian boundaries by means of calcareous nannofossil bi- ostratigraphy. 2. MATErIALs AND METHODs Two sedimentary successions have been measured and sam- pled at Jabals Malaqet and Mundassah. All together ca. 250 rock samples were collected for this study (Figs. 1–4). Smear slides for calcareous nannofossil investigation were prepared according to the techniques proposed by BRAMLETTE & SULLIVAN (1961) and HAY (1964, 1970). The slides were examined using a Carl Zeiss micro- scope at 1250x magnification in both plane polarized light and crossed nicols. Our data is reported in Tables 1 and 2. Photomicrographs of some representative taxa are provided in Plates 1 and 2. 3. sTrATIGrAPHIC bACKGrOUND The post-obduction neoautochthonous Upper Cretaceous- Eocene sedimentary succession unconformably overlies Up- per Cretaceous serpentinite, peridotite and pyroxenite of the Semail Ophiolite. The first marine transgression initiated de- position of shallow marine sediments and fluvial facies in- land (Qahlah Formation) over the eroded knappes of the Se- mail Ophiolite (GLENNIE et al., 1974). The Qahlah Formation is overlain by deposition of shallow-water lime- stones referred to as the Simsima Formation. They are ex- posed at Jabals Qarn El Barr, El Faiyah Range Mountains, El Rawdah, Malaqet and Mundassah. However, farther to the north at Jabal Qarn El Barr, the Simsima Formation is represented by deep marine deposits of pelagic sediments, based on the evidence of the occurrence of planktonic fora- minifera. The Simsima Formation is unconformably over- lain by the Muthaymimah Formation. 3.1. simsima Formation The Simsima Formation was first described by GLENNIE et al. (1974). Since the type section of the Simsima Forma- tion is no longer accessible, NOLAN et al. (1990) designated the Jabal Buhays section, El Fayiah Range Mountains, on the western side of the Northern Oman Mountains (19 km Table 1: Stratigraphic ranges of calcareous nannofossils of Jabal Malaqet. Paleocene Early Eocene Age Danian Selandian Thanetian Ypresian Muthaymimah Formation 3 4 5 6 15 17 20 24 25 26 29 36 43 47 48 49 54 55 56 57 58 61 Sample no. C C C C VR VR VR VR VR VR VR VR VR VR VR VR R VR F R R F Abundance M M G G P P M M M P P P P P P P P P M M P M Preservation NP4 NP5 NP9a NP11 Biozones (NP) R R R R Thoracosphaera operculata F R R F Cruciplacolithus primus R R R F Cruciplacolithus tenuis* R F F F Chiasmolithus danicus* R R R R Placozygus sigmoides R R R R Neochiastozygus medestus VR VR VR Ellipsolithus macellus* F F F F VR VR VR VR VR VR R VR R VR R Ericsonia cava VR VR VR VR VR VR R R Sphenolithus primus VR VR VR VR VR VR VR VR VR VR VR R VR VR Fasciculithus tympaniformis* VR VR VR VR R VR R R R Discoaster multiradiatus* VR VR R VR R Coccolithus pelagicus VR R VR R Discoaster barbadiensis VR R VR R Discoaster binodosus VR Zygrhablithus bijugatus VR Braarudosphaera bigelowii VR Tribrachiatus orthostylus* Abundance: A= Abundant, C= Common, F= Frequent, R= Rare, VR= Very rare Preservation: G= Good, M= Moderate, P= Poor, *= Marker species Geologia Croatica 65/3Geologia Croatica 398 Ta bl e 2: S tr at ig ra ph ic ra ng es o f c al ca re ou s n an no fo ss ils o f J ab al M un da ss ah . La te C re ta ce ou s Pa le oc en e Ag e La te M aa st ric ht ia n D an ia n Si m si m a M ut ha ym im ah Fo rm at io n 2 5 6 7 8 9 11 12 13 14 15 16 17 18 20 21 22 23 24 25 26 27 28 29 29 30 30 31 32 33 34 35 36 37 38 39 Sa m pl e no . VR VR VR VR VR R VR VR R VR R R VR VR VR VR R VR R VR R R F F F F F F C C R R F R VR VR Ab un da nc e M M M M M M M M M M M M M M M M M M M M M G G M M G G G G G M M G M M M Pr es er va tio n M ic ul a m ur us Ch ia sm ol ith us d an ic us (N P3 ) CN B io zo ne VR VR VR VR VR VR VR VR VR VR VR VR VR VR VR VR VR VR W at zn au er ia b ar ne sa e VR VR VR VR VR VR VR VR VR VR VR VR VR VR VR VR VR M ic ul a m ur us * VR VR VR VR VR VR VR VR VR VR VR VR VR VR VR VR VR M ic ul a de cu ss at a VR VR VR VR Ar kh an ge lsk ie lla cy m bi fo rm is VR Cr ib ro sp ha er el la e hr en be rg ii VR M ic ul a co nc av a VR VR Lu ci an or ha bd us ca ye ux ii VR St ra dn er ia cr en ul at a VR Ei ffe lli th us tu rr isi eff el ii VR VR Cr uc ip la co lit hu s p rim us VR R R R R F F F F VR F R F R Er ic so ni a ca va VR VR VR VR VR R VR VR VR VR VR VR VR Th or ac os ph ae ra o pe rc ul at a R R R VR R R VR VR VR VR VR Ch ia sm ol ith us d an ic us * VR R R R VR VR Cr uc ip la co lit hu s t en ui s* VR F F F F F F R VR Er ic so ni a su bp er tu sa VR R R R VR Co cc ol ith us p el ag ic us VR VR VR VR VR VR VR Pl ac oz yg us si gm oi de s Faris et al.: Upper Cretaceous to Lower Eocene calcareous nannofossil biostratigraphy from Malaqet and Mundassah sections... Geologia Croatica 399 Ta bl e 2: c on tin ue d. Pa le oc en e Ag e D an ia n Se la nd ia n M ut ha ym im ah Fo rm at io n 40 41 42 43 44 45 46 47 48 49 50 52 53 54 55 56 57 58 59 60 61 62 63 65 67 69 71 72 73 75 76 78 79 84 91 92 95 99 10 0 10 1 10 3 10 4 10 5 Sa m pl e no . F F C F R R C F F F C F R F R VR VR R VR R F c C F F R VR VR VR VR VR VR VR VR R VR R R VR R R F R Ab un da nc e M M M M M P M M M G M M M M M M M M M M M M M M M M M M M M M M M M M M M M M M M M M Pr es er va tio n N P4 N P5 N P6 CN B io zo ne R R F F F R VR VR VR R F R VR VR VR VR VR VR VR R Er ic so ni a ca va VR VR VR R R R R R F F R R VR VR VR VR VR VR R R F R VR VR VR VR VR VR VR VR VR Th or ac os ph ae ra o pe rc ul at a VR VR VR VR VR VR VR VR VR VR VR R VR VR VR VR VR R F F F VR VR Ch ia sm ol ith us d an ic us * R R C F F C R VR R F R R R Er ic so ni a su bp er tu sa VR VR R VR VR VR VR VR VR VR VR VR VR VR VR VR VR R Co cc ol ith us p el ag ic us R VR VR VR El lip so lit hu s m ac el lu s* VR VR VR VR VR VR R R VR VR Pl ac oz yg us si gm oi de s VR VR R VR VR VR VR R VR Cr uc ip la co lit hu s t en ui s* VR VR VR VR VR VR R VR VR N eo ch ia st oz yg us m ed es tu s VR M ar ka liu s i nv er su s F VR R F Th or ac os ph ae ra sa xe a VR F VR Ch ia sm ol ith us co ns ue tu s VR F VR VR VR VR VR VR VR VR Fa sc ic ul ith us ty m pa ni fo rm is* VR F R R VR VR VR VR VR VR VR VR VR R VR R Sp he no lit hu s p rim us R VR VR Bo m ol ith us e le ga ns VR VR VR Fa sc ic ul th us b ill ii VR N eo ch ia st oz yg us im br ie i R Fa sc ic ul th us b ob ii VR VR VR VR VR VR VR VR Fa sc ic ul ith us u lii VR VR VR Fa sc ic ul ith us p ile at us VR VR VR H el io lit hu s k le in pe lli i* Fa sc ic ul ith us st on eh en ge i Geologia Croatica 65/3Geologia Croatica 400 Ta bl e 2: c on tin ue d. La te P al eo ce ne Ag e Th an et ia n M ut ha ym im ah Fo rm at io n 10 6 10 7 10 9 11 0 11 2 11 3 11 4 11 5 11 7 11 8 12 0 12 1 12 2 12 3 12 4 12 5 12 6 12 7 12 8 12 9 13 0 13 1 13 2 13 3 13 4 13 5 13 6 13 7 13 8 13 9 14 0 14 1 14 2 14 3 14 4 14 5 14 6 14 7 14 8 14 9 15 0 15 1 15 2 15 3 15 4 Sa m pl e no . C C C c VR R R R R F F F F F F VR VR VR VR R VR F F R R VR F F R R F F C C C R R R C C C F F R C Ab un da nc e M M M M M M M M M G M M G G M M M M M M M M M M M M M M M M M M M M M M M M G G G M M M G Pr es er va tio n N P7 /8 N P9 a CN B io zo ne VR VR VR VR VR VR VR Th or ac os ph ae ra o pe rc ul at a R R R F VR VR R Er ic so ni a ca va R R VR F VR VR R VR R VR R R F R R VR VR VR VR VR F R VR VR VR R R VR VR R R R F F VR VR VR R R R VR VR VR R Co cc ol ith us p el ag ic us F F F R VR VR VR R R VR VR VR VR VR R R R VR VR VR F F VR VR VR VR R F R R VR VR Fa sc ic ul ith us ty m pa ni fo rm is* F F F C VR VR VR R VR R VR VR F R R VR VR R R VR VR VR VR VR R VR VR F F R R VR VR VR F F R F VR F Sp he no lit hu s p rim us VR VR VR VR VR VR VR VR VR R VR VR D isc oa st er m oh le ri* VR VR VR Bo m bo lit hu s c on ic us VR VR Bo m ol ith us e le ga ns VR VR Ch ia sm ol ith us d an ic us * VR VR R H el io lit hu s k le in pe lli i* VR VR D isc oa st er oi de s b ra m le tt ei VR Fa sc ic ul ith us a la ni i VR VR Ch ia sm ol ith us ca lif or ni cu s VR H el io lit hu s c an ta br ia e VR Fa sc ic ul ith us cl in at us VR VR VR VR VR Ch ia sm ol ith us co ns ue tu s VR VR Fa sc ic ul ith us u lii R VR VR VR VR F R VR R R VR VR R R Er ic so ni a su bp er tu sa VR VR VR VR VR Fa sc ic ul ith us li lli an ae VR VR VR VR VR VR VR VR VR Fa sc ic ul th us b ob ii VR VR VR R VR VR VR VR Fa sc ic ul th us b ill ii VR VR El lip so lit hu s m ac el lu s* VR R R F VR F VR F F F F R F R F D isc oa st er m ul tir ad ia tu s* VR VR VR R VR VR VR R R D isc oa st er b in od os us VR VR R VR R Fa sc ic ul ith us in vo lu tu s VR R VR VR VR Fa sc ic ul ith us b ite ct us VR R VR Fa sc ic ul ith us sc ha ub i R D isc oa st er fa lc at us VR Fa sc ic ul ith us th om as ii VR VR Fa sc ic ul ith us to ni i VR VR VR VR Fa sc ic ul ith us a ub er ta e R R D isc oa st er le nt ic ul ar is Faris et al.: Upper Cretaceous to Lower Eocene calcareous nannofossil biostratigraphy from Malaqet and Mundassah sections... Geologia Croatica 401 Table 2: continued. Early Eocene Age Ypresian Rus Formation 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 172 173 175 176 177 178 181 182 183 184 185 186 187 Sample no. F F C F C F R R C C C C F R R F F F VR F R F F C C R C F C Abundance M M G M M M M M G G M M M M M M M M M M M M M M M M G M G Preservation NP9b NP10 NP11 CN Biozone a b VR VR VR VR VR VR VR VR R VR VR VR VR VR R VR VR VR R Coccolithus pelagicus VR VR F VR VR R VR R F F F R VR VR Fasciculithus tympaniformis* R R R R R F VR R F F F F VR VR R R VR R VR VR R R VR F F VR F Sphenolithus primus F R F F F F VR R R F F F VR VR VR VR F R VR F R F R R R VR R VR Discoaster multiradiatus* VR VR F R R R VR VR VR R VR VR VR VR VR VR VR VR R Discoaster binodosus VR VR VR VR VR VR VR VR VR VR Fasciculthus bobii VR VR VR VR VR VR Fasciculithus schaubi VR VR VR VR VR VR VR VR Discoaster araneus* VR VR VR VR VR VR VR Fasciculithus aubertae VR VR VR VR VR VR Discoaster falcatus VR VR VR VR Fasciculithus alanii VR VR VR VR VR Fasciculithus richardii VR VR R VR R R R VR VR VR VR VR VR VR R F Sphenolithus moriformis VR VR R VR VR R VR VR VR VR VR VR F VR R VR R R R VR VR VR R Ericsonia cava VR VR VR VR Fasciculithus bitectus VR VR VR VR VR VR VR VR VR VR VR VR Fasciculithus involutus VR VR VR VR VR F VR VR VR VR R VR F F F Zygrhablithus bijugatus VR VR VR VR VR VR VR Braarudosphaera bigelowii VR Fasciculithus lillianae VR VR VR VR VR VR VR VR VR VR VR VR VR VR Thoracosphaera operculata VR Chiasmolithus consuetus VR VR Fasciculithus clinatus VR VR VR VR VR Discoaster mahmoudii* VR Fasciculithus richardii VR R VR VR VR Neochiastozygus junctus VR VR Tribrachiatus bramlettei* VR VR F R VR F Discoaster barbadiensis R R Tribrachiatus digitalis* VR R VR R Discoaster diastypus* VR VR VR F Tribrachiatus orthostylus* VR Pontosphaera multipora VR Camplylosphaera dela R Ericsonia formosa VR Sphenolithus radiatus VR Chiasmolithus solitus Geologia Croatica 65/3Geologia Croatica 402 PLATE 1 1 Micula murus (MARTINI, 1961) BUKRY (1973), sample #12, Mundassah section 2 Thoracosphaera saxea STRADNER (1961), sample #35, Mundassah section 3–4 Eiffellithus turriseiffelii (DFLANDRE in DEFLANDRE & FERT, 1954), sample #17, Mundassah section 5 Braarudosphaera bigelowii (GRAN & BRAARUD, 1935), sample #61, Malaqet section 6 Watznaueria barnesae (BLACK in BLACK & BARNES, 1959), sample #25, Mundassah section 7–8 Arkhangelskiella cymbiformis VEKSHINA (1959), sample #16,Mundassah section 9 Micula concava (STRADNER in MARTINI & STRADNER, 1960), sample #13, Mundassah section 10 Cribrosphaerella ehrenbergii (ARKHANGELSKY, 1912), sample #13, Mundassah section 11 Lucianorhabdus cayeuxii DELLANDRE (1959), sample #13, Mundassah section 12 Ericsonia subpertusa (HAY & MOHLER, 1967), sample #30, Mundassah section 13–14 Chiasmolithus solitus (BRAMLETTE & SULLIVAN, 1961), sample #187, Mundassah section 15–16 Pontosphaera multipora (KAMPTNER, 1948) ROTH (1970), sample #187, Mundassah section 17 Fasciculithus pileatus BUKRY (1973), sample #75, Mundassah section 18 Fasciculithus involutus BRAMLETTE & SULLIVAN (1961), sample #164, Mundassah section 19 Sphenolithus radians DEFLANDRE in GRASSE (1952), sample #187, Mundassah section 20 Zygrhablithus bijugatus (DEFLANDRE in DEFLANDRE & FERT, 1954), sample #168, Mundassah section 21–22: Sphenolithus primus PERCH-NIELSEN (1971), sample #15, Malaqet section 23 Neochiastozygus junctus (Bramlette & Sullivan, 1961), sample #181, Mundassah section 24 Discoaster barbadiensis Tan (1927), Sample #183, Mundassah section *all figures X 1250 Faris et al.: Upper Cretaceous to Lower Eocene calcareous nannofossil biostratigraphy from Malaqet and Mundassah sections... Geologia Croatica 403 PLATE 2 1 Chiasmolithus danicus (BROTZEN, 1959), sample # 6, Jabal Malaqet. 2–3 Ellipsolithus macellus (BRAMLETTE & SULLIVAN, 1961), sample #52, Jabal Mundassah 4–5 Heliolithus kleinpellii SULLIVAN (1964), sample #109, Jabal Mundassah 6 Placozygus sigmoides (BRAMLETTE & SULLIVAN, 1961), sample # 6, Jabal Malaqet 7–8 Fasciculithus tympaniformis HAY & MOHLER in HAY et al. (1967), sample #24, Jabal Malaqet 9–10 Tribrachiatus orthostylus SHAMRAI (1963), sample #184, Jabal Mundassah 11–12 Discoaster mahmoudii PERCH-NIELSEN (198 l), sample #175, Jabal Mundassah 13–14 Tribrachiatus bramlettei (BRONNIMANN & STRADNER, 1960), sample #173, Jabal Mundassah 15–16 Tribrachiatus digitalis AUBRY (1996), sample #182, Jabal Mundassah 17–18 Discoaster multiradiatus BRAMLETTE & REIDEL (1954), sample #56. Jabal Malaqet 19–20 Discoaster araneus BUKRY (1971), sample #158, Jabal Mundassah *all figures X 1250 Geologia Croatica 65/3Geologia Croatica 404 northwest of Jabal El Rawdah) as an alternative type-sec- tion. The Simsima Formation is unconformably overlain by the Muthaymimah Formation and overlies the Semail Ophi- olite. At Jabal Malaqet, it consists of an 8 m-thick dolomitic limestone, with the presence of iron oxide and a rich assem- blage of large foraminifera. At Jabal Mundassah, the Sim- sima Formation also consists of a basal dolomitic limestone with iron oxide and rich in large foraminifera, followed by approximately 30 m of greenish-grey to reddish-yellow lam- inated marls, rich in planktonic foraminifera, and calcareous nannofossils (Fig. 5). Figure 5: Correlation between the identified calcareous nannofossil zones and the studied foraminiferal zones (ABDELGHANY, 2003). Faris et al.: Upper Cretaceous to Lower Eocene calcareous nannofossil biostratigraphy from Malaqet and Mundassah sections... Geologia Croatica 405 3.2. Muthaymimah Formation This formation was firstly described by NOLAN et al. (1990) on the northwestern side of Sayh Muthaymimah, southeast of Buraymi, Sultanate of Oman. The formation unconform- ably overlies the Simsima Formation and consists of shale, marl, clay nodules and argillaceous limestone, mudstone, and breccia with conglomerate interbeds including clasts of Simsima Limestone, reworked rudists, coral fragments, re- worked ophiolite and Hawasina chert. It is both ferruginous and highly fossiliferous. At Jabal Malaqet, the lower parts of the Muthaymimah Formation are composed of greenish grey marl, mudstone and limestone with intraformational conglomerate layers at the base. The middle part of the for- mation is represented by a 160 m thick sequence of breccia beds with limestone and chert fragments derived from the older rocks (Figs. 2, 3). It is topped by marl interlayered with nummulitic, alveolinid limestone of Early Eocene age. The formation measures about 490 m in thickness. Otherwise, at Jabal Mundassah (Figs. 3, 4), the Muth- aymimah Formation unconformably overlies the Upper Cre- taceous Simsima Formation and consists of interlayered clay- rich marl with gypsum veinlets, followed by fossiliferous and argillaceous limestone. Its measured thickness is about 340 m. It unconformably overlies the Upper Cretaceous Simsima Formation, and is topped by marl interlayered with nummu- litic, alveolinid limestone of Early Eocene age. 4. CALCArEOUs NANNOFOssIL bIOsTrATIGrAPHY Calcareous nannofossils are a valuable tool in biostratigra- phy, and it was decided to test the use of Paleogene calcare- ous nannofossil zonations (MARTINI, 1971) and successive emendation by ROMEIN (1979), and AUBRY et al. (2000) in the studied area. The present paper describes the distribu- tion of calcareous nannofossil taxa throughout the Simsima and Muthymimah formations. The identified calcareous nan- nofossils are generally diverse and abundant in the studied sections, and have enabled subdivision of the studied strati- graphic intervals into nine biozones (Tables 1 to 2). The list of the Upper Cretaceous, Paleocene and Early Eocene cal- careous nannofossil taxa is documented in Appendix (1), follows that outlined in PERCH-NIELSEN (1985a,b). 4.1. Upper Cretaceous biostratigraphy The Upper Cretaceous Zonal Scheme of ROMEIN (1979) is adapted here. Abbrevations used in the present work are: FO = First Occurrence, LO= Last Occurrence. 4.1.1.- The Micula murus Zone (rOMEIN, 1979) The Micula murus Zone of ROMEIN (1979) is defined by the FO of M. murus for the base and the Last Occurrence of Micula murus and other Cretaceous taxa and the AB of Tho- racosphaera and Braarudosphaera for the top. Age: Late Maastrichtian Occurrence: Jabal Mundassah section Common species: M. murus Zone of ROMEIN (1979) is equivalent to the lower part of Nephrolithus frequens Zone (CC 26) of SISSINGH (1977). At Jabal Mundassah, this in- terval is characterized by a well-diversified nannofossil as- semblage which include Watznaueria barnesiae, Micula dec- ussata, Arkhangelskiella cymbiformis, Cribrosphaerella ehrenbergii, Eiffellithus turriseiffelii, Lucianorhabdus spp., Prediscosphera spp., Lithraphidites quadratus and Zygodi- sus spiralis. 4.2. The Paleocene and Eocene biostratigraphy For the Paleocene and Eocene, we adopt the biozonation proposed by MARTINI (1971) and emended by AUBRY et al. (2000). 4.2.1. The Chiasmolithus danicus Zone (NP3) This is defined as the interval from the first occurrence FO of Chiasmolithus danicus to the FO of Ellipsolithus macel- lus. Age: Early Palaeocene (latest Danian). Occurrence: Jabal Mundassah section. Common species: Thoracosphaera operculata, and Pla- cozygus spp. The following Palaeocene nannofossil species first appeared in this zone: Cruciplacolithus tenuis, C. primus, Coccolithus pelagicus, Ericsonia subpertusa and C. danicus. 4.2.2. The Ellipsolithus macellus Zone (NP4) Author: MARTINI (1970) The Ellipsolithus macellus Zone is defined as the inter- val from the FO of Ellipsolithus macellus to the FO of Fas- ciculithus tympaniformis. Age: Early Paleocene (late Danian). Occurrence: Jabals Malaqet and Mundassah sections Common species: The nannofossil taxa present in the NP4 Zone are those recorded in the NP3 Zone, plus Ellipso- lithus macellus. The first taxon ascribable to genus Spheno- lithus, S. primus, is observed in the upper part of this zone. The first radiation of the Fasciculithus genus occurs within NP4 Zone. 4.2.3. The Fasciculithus tympaniformis Zone (NP5) Authors: MOHLER & HAY in HAY et al. (1967) The Fasciculithus tympaniformis Zone is defined as the interval from the FO of Fasciculithus tympaniformis to the FO of Heliolithus kleinpellii. Age: Middle Palaeocene (Selandian) Occurrence: Jabals: Malaqet and Mundassah sections Common taxa: In the studied sections (Mundassah, Malaqet), this zone contains a similar assemblage to Zone NP4 but it is distinguished by the presence of Fasciculithus tympaniformis, and Bomolithus elegans. A big hiatus is detected in the Jabal Malaqet section, as shown by the absence of the complete NP6 and NP7/8 Zones. Geologia Croatica 65/3Geologia Croatica 406 4.2.4. The Heliolithus kleinpellii Zone (NP6) Authors: MOHLER & HAY in HAY et al. (1967) The Heliolithus kleinpellii Zone is defined as the inter- val from the FO of Heliolithus kleinpellii) to the FO of Dis- coaster mohleri. Age: Middle Paleocene (Selandian) Occurrence: Jabal Mundassah section Common species: This zone includes the same nanno- fossil species observed in the F. tympaniformis Zone plus H. kleinpelli, H. cantabriae and Bomolithus conicus. The NP6 Zone occupies a thin interval at Jabal Mundas- sah and is completely absent at Jabal Malaqet. 4.2.5. The Discoaster mohleri Zone (NP7/8) Authors: HAY (1964) and MOHLER in HAY et al. (1967) emend ROMEIN (1979) Since Heliolithus riedeli has not been observed in many localities worldwide, ROMEIN (1979) emended the defini- tions of the NP7 and NP8 Zone as originally proposed by MARTINI (1971), defining the Discoaster mohleri Zone (Zone NP7/8) as the interval from the FO of D. mohleri to the FO of D. multiradiatus, thus merging together the NP7 and NP8 Zones. We have also combined NP7 Zone and NP8 Zone into a NP7/8 because H. riedeli is missing in these sec- tions. Age: Late Palaeocene (Thanetian) Occurrence: Jabal Mundassah section Common species: The NP7/8 Zone is well represented at Jabal Mundassah. The NP7/8 Zone includes the same nannofossil assem- blage recorded in the NP6 Zone, with D. mohleri, D. bram- lettei, Fasciculithus alanii, F. clinatus, F. lilianae and Helio- lithus cantabriae. 4.2.6. The Discoaster multiradiatus Zone (NP9) Authors: BRAMLETTE & SULLIVAN (1961) emend. MARTINI (1971) and BUKRY & BRAMLETTE (1970). The Discoaster multiradiatus Zone is defined as the in- terval from the FO of D. multiradiatus to the FO of Tribra- chiatus bramlettei. Age: Late Paleocene – Early Eocene Occurrence: Jabals: Malaqet and Mundassah sections Common species: In the studied sections, the diversity of nannofossil assemblages reaches its maximum within the NP9 Zone. The Discoaster multiradiatus Zone is recorded in the Jabal Malaqet and Mundassah sections with variable thick- nesses. The second radiation of new Fasciculithus species is initiated in Zone NP9 and includes the FOs of F. involutus, F. schaubii, F. thomasii, F. tonii, F. aubertae and F. richardii, which is consistent with previous data (e.g. PERCH- NIELSEN, 1985; AGNINI et al., 2007). Other taxa first ap- pearing in this zone include: Discoaster mahmoudii, D. bino- dosus, D. falcatus, D. lenticularis, D. araneus D. bar ba diensis, D. diastypus and Zygrhablithus bijugatus. AUBRY et al. (2000) and FARIS & ABU SHAMA (2007) subdivided the D. multiradiatus Zone (NP9) into two Subzones NP9a and NP9b using the FOs of Rhamboaster spp. and/ or D. araneus. These biohorizons were proposed by the International Subcommission on Palaeogene Stratigraphy (ISPS) to approximate the Paleocene/Eocene (P/E) bound- ary. At Jabal Mundassah, The FO of D. areneus has been observed in sample 155 and is used to mark the P/E bound- ary in this section. At the Malaqet section, the top of the NP9a Subzone cannot be pinpointed due to the absence of Rhamboaster taxa and Discoaster araneus (markers of the base of the NP9b Subzone), and the absence of Tribrachia- tus contortus (the marker of the base of the NP10 Zone). This suggests the presence of a major hiatus at the P/E transition in this section. 4.2.7. The Tribrachiatus contortus Zone (NP10) Authors: HAY (1964) and BUKRY (1973) The Tribrachiatus contortus Zone is defined as the in- terval from the FO of Tribrachiatus bramlettei to the LO of T. contortus. Age: Early Eocene (Ypresian) Occurrence: Jabal Mundassah section Common species: The NP10 Zone has been subdivided into four Subzones (NP 10a–d) based on the successive bio- horizons, the FO of Tribrachiatus bramlettei, the FO and LO of T. digitalis, the FO and LO of T. contortus (AUBRY, 1996). The T.digitalis morphotype shows intermediate morpho- logical features between T. contortus and T. orthostylus and disappears within the lower part of the range of the latter species (RAFFI et al., 2005). On the other hand, the However, the FO of T. digitalis at ODP Site 1262 is recorded within the lowermost part of the range of T. contortus (AGNINI et al., 2007), in agree- ment with the previous findings of RAFFI et al. (2005), in palaeoequatorial Pacific and North Atlantic sections. This implies that the previously proposed subdivision of MARTINI’S (1971) Zone NP10 (NP10a-NP10d of AU- BRY, 1999) collapses. Consequently the exact duration of Subzone NP10b (= range of digitalis) remains uncertain. The Tribrachiatus digitalis morphotype is often reported from only a few samples. It was recorded in single samples at DSDP Site 577 and ODP Site 1051 (CRAMER et al., 2003), in two samples from DSDP Site 550 (AUBRY, 1995, AUBRY et al., 1996), in six samples in the poorly recovered cores 5 and 6 at DSDP Hole 117A (AUBRY, 1995), and in probably only two samples from the proposed P/E GSSP section of Dababiya in Egypt (DUPUIS et al., 2003). The T. contortus Zone (NP10) is tentatively recognized at Jabal Mundassah (T. bramlettei, is observed in samples Faris et al.: Upper Cretaceous to Lower Eocene calcareous nannofossil biostratigraphy from Malaqet and Mundassah sections... Geologia Croatica 407 173 and 184), and T. digitalis is identified from samples 182 and 183 (Table 2). It is remarkable that Zone NP10 is miss- ing at Jabal Malaqet, suggesting either a small hiatus within the Early Eocene or a potential sampling gap. 4.2.8. The Discoaster binodosus Zone (NP11) Authors: MOHLER & HAY in HAY et al. (1967) The Discoaster binodosus Zone is defined as the inter- val from the LO of T. contortus and the FO of Discoaster lodoensis. Age: Early Eocene (Ypresian) Occurrence: Jabals: Malaqet and Mundassah sections Common species: The LO of T. orthostylus is usually found in the uppermost part of Zone NP10 in many locali- ties in the world (PERCH-NIELSEN, 1985b). PERCH- NIELSEN, (1985b) mentioned that in case of the absence of T. contortus (its highest occurrence defines the base of the NP11 Zone) the FO of T. orthostylus can be used to approx- imate the base of NP11 Zone. Following the reasoning of PERCH-NIELSEN (1985b), the FO of T. orthostylus has been utilized here in order to place the base of NP11 Zone in the studied two sections. Besides the nannofossil taxa identified in the NP10 Zone, other species that first appeared in the NP11 Zone include T.orthostylus, Sphenolithus radi- ans, Ericsonia formosa and Chiasmolithus solitus. 4.3. stage boundaries The studied Upper Cretaceous – Lower Eocene sequence contains a set of biozones covering several stages. The cal- careous nannofossils provide a useful global marker for the precise placement of stages and boundaries. In terms of the identified calcareous nannofossils, the Cretaceous/Palaeo- gene (K/Pg), the Danian/Selandian, the Selandian/Thanetian and the Paleocene/Eocene (P/E) boundaries are briefly dis- cussed below. 4.3.1. The K/Pg boundary The Global Stratotype Section and Point (GSSP) for the K/ Pg boundary which has been voted by the International Committee on Stratigraphy (ICS) and ratified by the Inter- national Union of Geological Science (IUGS) are defined in the El Kef section in Tunisia. The boundary lies at the base of the boundary clay which consists of a 2.0 mm thick, rust colored ferruginous layer overlain by a 1.0m thick black clayey bed within a monotonous succession of marl. This level coincides with the largest extinction event in plank- tonic foraminifera, together with an Iridium anomaly and an abrupt change in the stable isotope values as well as the car- bonate content (ARENILLAS et al., 2002). At the Jabal Mundassah section, there is a stratigraphic gap around the K/Pg boundary interval which includes the uppermost Maastrichtian (Micula prinsii Zone) and the Early Danian (Markalius inversus and Cruciplacolithus tenuis Zones). Cretaceous nannofossils rarely occurred above the K/P boundary in the NP3 Zone at the Jabal Mundassah section. In the present study, the authors believe that not all of the Cre- taceous forms present in the Lower Danian sediments are due to reworking, but some of them may represent surviving taxa. 4.3.2. The Danian/selandian boundary The subdivision of the Palaeocene into the Danian, Se- landian and Thanetian was proposed by the ISPS (JENKINS & LUTERBACHER, 1992). The Global Stratotype Section and Point (GSSP) for the base of the Selandian Stage coincides with; the second evo- lutionary radiation of the calcareous nannofossil genus Fas- ciculithus, a sharp decrease in the abundance of Braaru- dosphaera and is close to the NP4/NP5 zonal boundary (BERNAOLA et al., 2009). In the Thamad area, east central Sinai, Egypt, the Danian/Selandian boundary is tentatively placed at the base of Zone NP5 (FARIS & ABU SHAMA, 2007). The base of Danian Stage can be approximated by the base of the NP1 Zone, while the base of the Selandian Stage can be approximated at the base of NP 5 Zone (CLEM- MENSEN & THOMSEN, 2005). In the studied two sections, the FO of F. tympaniformis was used to delineate the Danian/ Selandian boundary which coincides with the NP4/NP5 zonal boundary. 4.3.3. The selandian/Thanetian boundary The base of the Thanet Formation in Kent, England was used to define the Selandian/ Thanetian boundary. It corresponds to the lower part of the planktonic foraminiferal P4 Zone (BERGGREN et al., 1995). The calcareous nannofossil stud- ies showed that the base of the Thanetian Stage could be re- ferred to the uppermost part of NP6 or NP6/ NP7 (undiffer- entiated) (BERGGREN et al., 1995). At Jabal Mundassah, the Selandian Stage comprises the NP5 and NP6 Zones and the Selandian/Thanetian boundary is marked at the base of Zone NP7/8 (D. mohleri Zone). At the Malaqet section, a major hiatus is suggested at the Se- landian/Thanetian transition because the NP6 and NP7/8 p.p. Zones cannot be recognized. 4.3.4. The P/E boundary The Palaeocene/Eocene working group placed the GSSP for the base of the Eocene series in the abandoned Quarry of Dababiya at the base of the Dababiya Quarry Beds (DQB), Luxor, Nile Valley, Egypt and it is defined at the onset of the Carbon Isotope Excursion (CIE) (AUBRY et al., 2007). Ac- cording to DUPUIS et al. (2003) the base of the Eocene Series (base NP 9b Subzone) can be approximated by the FO of warm-water species (e.g. Rhamboaster spineus, R.cuspis, R. intermedia, R. calcitrapa, R. bitrifida and Discoaster araneus). At the Jabal Mundassah section, the FO of Discoaster araneus (which defines the base of the NP9b Subzone,) is used to approximate the base of the Eocene. At the Malaqet section, the P/E boundary interval is missing and a major hiatus is present as indicated by the absence of the NP9b Subzone, in addition to the complete absence of the NP10 Zone (see Table 1). Geologia Croatica 65/3Geologia Croatica 408 5. sUMMArY AND CONCLUsIONs This work presents a calcareous nannofossil biostratigraphic study spanning the Maastrichtian – Ypresian interval at Malaqet and Mundassah (southeast of Al-Ain City, UAE). Two rock stratigraphic units were recognized in the study area; the Simsima Formation (Late Maastrichtian), and the Muthayminah Formation (Palaeocene-Early Eocene). A stratigraphic gap is located around the K/Pg boundary at the Mundassah section, where the M. prinsii Zone (latest Maas- trichtian) and NP1 to NP3 Zones (Early Danian) are absent. The Danian/ Selandian boundary is positioned where Fas- ciculithus tympaniformis first occurred (at the base of Zone NP5). The Selandian/Thanetian boundary is placed at the level of the FO of Discoaster mohleri (base of the NP7/8 Zone), at the Jabal Mundassah section. A major hiatus is present around the Selandian/Thanetian boundary at the Jabal Malaqet section as indicated by the absence of the NP6 and NP7/8 Zones. The Palaeocene/Eocene boundary is placed at the base of Zone NP9b (which is defined by the FO of Discoaster araneus) at the Jabal Mundassah section. At the Jabal Malaqet section the Palaeocene/Eocene boundary interval is missing and a major hiatus is testified by the absence of the NP9 b Subzone and NP10 Zone. ACKNOWLEDGEMENT The authors wish to thank UAE University for providing the necessary facilities to complete this work. We thank Mr. Hamdi KANDIL, Geology Department, UAE University for his help in enhancement of the figures and plates of this pa- per. AppENdix Taxonomy in general follows that outlined in PErCH-NIELsEN (1985a and b). UPPEr CrETACEOUs CALCArEOUs NANNOFOssIL TAxA Arkhangelskiella cymbiformis VEKSHINA (1959) Cribrosphaerella ehrenbergii (ARKHANGELSKY, 1912) DEFLANDRE in PIVETEAU (1952) Eiffellithus turriseiffelii (DEFLANDRE in DEFLANDRE and FERT, 1954) REINHARDT, 1965. Lucianorhabdus cayeuxii DEFLANDRE (1959) Micula concava (STRADNER in MARTINI & STRAD- NER, 1960) VERBEEK (1976b) Micula decussata VEKSHINA (1959) Micula murus (MARTINI, 1961) BUKRY (1973) Stradneria crenulata (BRAMLETTE & MARTINI, 1964) NOEL (1970) Thoracosphaera operculata BRAMLETTE & MARTINI (1964) Watznaueria barnesiae (BLACK in BLACK & BARNES, 1959) PERCH-NIELSEN (1968) PALEOCENE AND EOCENE CALCArEOUs NANNOFOssILs TAxA Bomolithus conicus (PERCH-NIELSEN, 1971) PERCH- NIELSEN (1984a) Bomolithus elegans ROTH (1973) Braarudosphaera bigelowii (GRAN & BRAARUD, 1935) DEFLANDRE (1947) Campylosphaera dela (BRAMLETTE & SULLIVAN, 1961) HAY & MOHLER (1967) Chiasmolithus californicus (SULLIVAN, 1964) HAY & MOHLER (1967) Chiasmolithus consuetus (BRAMLETTE & SULLIVAN, 1961) HAY & MOHLER (1967) Chiasmolithus danicus (BROTZEN, 1959) HAY & MOHLER (1967) Chiasmolithus solitus (BRAMLETTE & SULLIVAN, 1961) LOCKER, 1968 Coccolithus pelagicus (WALLICH, 1877) SCHILLER (1930) Cruciplacolithus primus PERCH-NIELSEN (1977) Cruciplacolithus tennuis (STRADNER, 1961) HAY & MOHLER in HAY et al. (1967) Discoaster araneus BUKRY (1971) Discoaster barbadiensis TAN (1927) Discoaster binodosus MARTINI (1958) Discoaster diastypus BRAMLETTE & SULLIVAN (1961) Discoaster falcatus BRAMLETTE & SULLIVAN (1961) Discoaster lenticularis BRAMLETTE & SULLIVAN (1961) Discoaster mahmoudii PERCH-NIELSEN (198l) Discoaster mohleri BUKRY & PERCIVAL (1971) Discoaster multiradiatus BRAMLETTE & REIDEL (1954) Discoasteroides bramlettei (BUKRY & SULLIVAN,1971) Ellipsolithus macellus (PERCH-NIELSEN, 1961) SULLI- VAN (1964) Ericsonia cava (HAY & MOHLER, 1967) PERCH- NI ELSEN (1969) Ericsonia formosa (KAMPTNER, 1963) HAQ (1971) Ericsonia subpertusa HAY & MOHLER (1967) Fasciculithus alanii PERCH-NIELSEN (1971) Fasciculithus aubertae HAQ & AUBRY (1981) Fasciculithus billii PERCH-NIELSEN (1971) Fasciculithus bitectus ROMEIN (1979) Fasciculithus bobii PERCH-NIELSEN (1971) Faris et al.: Upper Cretaceous to Lower Eocene calcareous nannofossil biostratigraphy from Malaqet and Mundassah sections... Geologia Croatica 409 Fasciculithus clinatus BUKRY (1971) Fasciculithus involutus BRAMLETTE & SULLIVAN (1961) Fasciculithus lilianae PERCH-NIELSEN (1971) Fasciculithus pileatus BUKRY (1973) Fasciculithus richardii PERCH-NIELSEN (1971) Fasciculithus schaubii HAY& MOHLER (1967) Fasciculithus stonehengei HAQ & AUBRY, 1981 Fasciculithus thomasii PERCH-NIELSEN (1971) Fasciculithus tonii PERCH-NIELSEN (1971) Fasciculithus tympaniformis HAY & MOHLER in HAY et al. (1967) Fasciculithus ulii PERCH-NIELSEN (1971) Heliolithus cantabriae PERCH-NIELSEN (1971) Heliolithus kleinpellii SULLIVAN (1964) Markalius inversus (DEFLANDRE in DEFLANDRE & FERT, 1954) BRAMLETTE & MARTINI (1964) Neochiastozygus imbriei HAQ & LOHMANN (1976) Neochiastozygus junctus (BRAMLETTE & SULLIVAN, 1961) PERCH -NIELSEN (1971) Neochiastozygus modestus PERCH-NIELSEN (1971) Placozygus sigmoides (BRAMLETTE & SULLIVAN, 1961) ROMEIN (1979) Pontosphaera multipora (KAMPTNER, 1948) ROTH (1970) Sphenolithus moriformis ((BRONNIMANN & STRAD- NER, 1960) BRAMLETTE & WILCOXON (1967) Sphenolithus primus PERCH-NIELSEN (19710) Sphenolithus radians DEFLANDRE in GRASSE (1952) Thoracosphaera operculata BRAMLETTE & MARTINI (1964) Thoracosphaera saxea STRADNER (1961) Tribrachiatus bramlettei (BRONNIMANN & STRAD- NER, 1960) PROTO DECIMA et al. 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Manuscript received August 30, 2011 Revised manuscript accepted June 18, 2012 Available online October 30, 2012