Albian calcareous nannofossils from the Gault Clay of Munday’s Hill (Bedfordshire, England)

Abundant and diverse Middle and Upper Albian nannofossil assemblages are present in the Gault Clay exposed at Munday’s Hill, Bedfordshire, England. The section was deposited between the first appearance datums of Tranolithus orionatus and Eiffellithus turriseiffeli. This interval can be further subdivided, using the last appearance of Braloweria boletiformis and the first appearances of Axopodorhabdus albianus, Owenia hilli sp. nov. and Eiffellithus monechiae sp. nov. The presence of Braloweria boletiformis, Ceratolithina hamata and Gaarderella granulifera, only at this and other north-west European localities, defines a unique endemic nannofloral province. Low latitude species are present throughout the studied section and first and last appearance datums of species are nearly synchronous, both at Munday’s Hill and in other areas. This indicates continuous marine connections between Munday’s Hill and low latitude areas through the Mid and Late Albian. Abundance patterns of high latitude nannofossils, primarily Repagulum parvidentatum and Seribiscutum primitivum, suggest that relatively cold waters dominated in the Munday’s Hill area near the base of the Middle Albian. The abundance of high latitude taxa gradually decreased towards the end of the Middle Albian, but temporarily increased at the base of the Upper Albian. The abundance of high latitude taxa was relatively low throughout the lower half of the Upper Albian and intermediate to low in the upper half of the Upper Albian. Two new genera, Braloweria gen. nov. and Owenia gen. nov., and two new species, Owenia hilli sp. nov. and Eiffellithus monechiae sp. nov., are described.


INTRODUCTION
During the Mid and Late Albian, an epicontinental sea covered much of what is now north-west Europe. This sea was connected to the Tethys-Proto-Atlantic seas in the south and to the high northern latitudes via narrow passageways (Fig. 1). North-west Europe was during this time, intermittently influenced by water masses from both the south and the north due to regional transgressions and regressions and tectonic processes. Studies of ammonites (Owen, 1971(Owen, , 1973 have shown that the north-west European faunas of the Middle and Upper Albian sometimes showed strong provincialism and sometimes varying degrees of influence of Tethyan or high latitude elements. Black (1972Black ( ,1973 describednumerous calcareous nannofossil species from the Gault Clay (Middle and Upper Albian) of south-east England which have never been recorded elsewhere. Manivit (1976) suggested that these species formed a distinct nannofloral province restricted to north-west Europe.
This study aims to study the stratigraphic distribution of calcareous nannofossils present in the Gault Clay at Munday's Hill, Bedfordshire, England. Furthermore, to compare the results with nannofossils from other areas and to ammonite and foraminifera1 faunas in order to trace palaeoceanographic variations in north-west Europe during the Middle and Upper Albian.

MATERIALS AND METHODS
A section of Gault Clay exposed in the Munday's Hill pit, near Leighton Buzzard (Grid ref. SP 939279), is chosen for this study (Fig.   1). The Munday's Hill pit contains well preserved and diverse nannofossil assemblages which show great variation through time. During the Mid and Late Albian, the area was connected to open marine seas to the south and north and was influenced by both low and high latitude waters. The section has previously been analysed for ammonite faunas (Owen, 1972) and details of the ammonite stratigraphy, to which the nannofossil samples are correlated, are presented in Fig. 2. Forafulldescriptionof the Munday's Hill section, see Owen (1972) Thirty six samples were collected from the Middle Albian Hoplites dentatus ammonite Zone, to the Upper Albian Mortoniceras injlatum ammonite Zone. The very base of the dentatus Zone was not sampled, thus the lowermost Middle Albian is not represented. A stratigraphic break occurs in the middle of the section with part of the Euhoplites loricatus, all of the E . lautus and part of the injlatum ammonite Zones missing. The Stoliczkaia dispar ammonite Zone from the uppermost Albian is also missing. Details of the samples are presented in Appendix 1 . Of the 36 samples, the lowermost (sample 11) was barren of nannofossils, but the remaining 35 samples contained abundant and diverse nannofloras. Diversity ranged from 39 to 54 species (Fig. 3). All assemblages showed signs of etching, with some overgrowth of secondary calcite in the higher samples examined. Roth and Krumbach (1986) considered dominance of the nannofossil assemblages by Watznaueria barnesae as a sign of poor preservation. In the samples studied, W. barnesae was very abundant only in samples 22,33 and 34. Samples 33 and 34 did show low diversities, however, sample 22, contains SO different species. The nannofossil content of the rock samples increases in the Upper Albian relative to the Middle Albian. Samples 27 -29 are slightly less well preserved than the other samples.
The samples were prepared for examination in the light microscope using the methods described in Crux (1989). Visual abundance estimates of all species observed were made at X 1562 magnification. Detailed abundance counts on selected species were made at XlOOO magnification following a method described by Backman and Shackleton (1983). All specimens were counted in 2. 5 fields ofview withadiameterof25Opn-1. (A wide field lens wasused.) These abundances are presented as number of specimens per square millimeter in the slide. Selected samples were also examined in the ccanning electron microscope (SEM) using a centrifuge preparation technique described by Taylor and Hamilton ( 1982).

NANNOFOSSIL BIOSTRATIGRAPHY
The whole of the stratigraphic interval exposed in Munday's Hill lies between the first appearance datums of the nannofossils Tranolithus orionatus and Eiffellithus turriseiffeli. This interval equates to the upper part of the Prediscosphaera cretacea Zone of Thierstein (1971), Zone 8b of Sissingh (1977) emend Perch-Nielsen ( 1979 and the Prediscosphaera cretacea tohopodorhabdus albianus Zones NC 8-9 of Roth (1978). There is potential to further subdivide this timehock interval using nannofossil datums of both a local and more cosmopolitan scale. In ascending order these are:

Last appearance datum (LAD) of Braloweria boletiformis
This species has never been recorded outside south-east England. Black (1972) reported it to have a LAD in Bed 111 (niobe Subzone) at Copt Point, Folkestone, 1 Sft above the base of the Gault Clay. He also recorded its occurrence in the basal beds of the Lower Gault in Cambridgeshire, Norfolk and Suffolk. This agrees with the present study where this LAD is recorded in sample 21, which was collected from near the intermediuslniohe Subzonal boundary.
Braloweria holetiformis is probably endemic to north-west Europe. Its LAD is a useful event in this area but is unlikely to be recorded elsewhere.

LAD of Hayesites albiensis
Hayesites albiensis has previously been recorded to co-occur with E. turriseiffeli by Roth and Thierstein (1972), Romein (197S), Thierstein (1976), Manivit et al. (1977), Verbeek (1977), Noel (1980), Amedro et al. (1981), Taylor (1982), Watkins and Bowdler (1984) and Wiegand (1984). Manivit et al. (1977) defined the Hayesites albiensis Subzone as the interval where E. turriseiffelli and H. albiensis co-occur. In the present s t u d y a . alhiensis was found to have its LAD below the first occurrence of Eiffellithus monechiae, the ancestral species of E. turriseiffeli. HayCesites alhiensis has a LAD in the niobe Subzone at Munday's Hill, which is earlier than recorded in most other studied sections. Some of the difference in this record may be due to the hiatus which results in the absence of part of the niobe, all of the subdelaurei to daviesi and part of the cristatum Subzones in the Munday's Hill section. Wise (1983) also recorded an early LAD for H. albiensis before the FAD of E. turriseiffeli in the high latitude South Atlantic DSDP Site 51 1. It thus appears that H . alhiensis has a shorter stratigraphic range in high latitudes and is probably unreliable for biostratigraphical purposes in such areas. Sample distribution compared to the ammonite zonal scheme of the north-west European province (Owen, 1984).
and Cepek (1982) all recorded the FAD of A . alhianus before the FAD of T. orionarus. Cepek's (1982) samples may have been contaminated as he also records Micula staurophora in the Lower Albian. Hill's ( I 976) FAD of T. orionatus (exiguus) lies within the Upper Albian and thus this record is probably not its true first occurrence. Romein (1975) only found A . alhianus in one sample below T. orionatus. In conclusion, it is more likely that the correct order of events is: the FAD of T. orionatus followed by the FAD of A. alhianus.
The FAD of A . alhianus lies within the niohe Subzone at Munday's Hill. This is slightly younger than its FAD recorded by Amedro et al. (1981) from Boulonnais in the intermedius Subzone, but slightly older than Black's (1972) record from Bed V at Copt Point (nitidus Subzone). The FAD of A. albianus thus appears to be a reliable cosmopolitan biostratigraphical datum.

FAD of Owenia hilli
The only previous record of this species is by Hill (1976) who recorded it in the Upper Albian of Texas under the name Amphizygus brooksii ssp. nanus. His observation of a FAD of this species at the base of the Upper Albian agrees with the findings of the present study, although at Munday's Hill, the base of the Upper Albian is absent due to a break in sedimentation. This species is rare in both Texas and England but its distinctive appearance may make it useful in future biostratigraphical studies.

FAD of Corollithion signum
Corollithion signum has been recorded in strata as old as the Early Albian (Bukry, 1969) and by several authors in the Middle Albian: Wise and Wind (1977), Perch-Nielsen (1979) and Roth (1983). Many authors don't record this species until the Upper Albian. These inconsistencies in the level of the FAD of C. signum are possibly caused by differences in taxonomic concepts. Corollithion signum probably evolved from Corollithion achylosum (Perch-Nielsen, 1985) through an intermediate form; Corollithion protosignum. The lineage involves the change from the circular C . achylosum to the hexagonal C. signum. This change is gradual and thus the FAD of C. signum is difficult to define precisely.
In the present study, the FAD of C. signum is recorded in the cristatum Subzone at Munday's Hill. The usefulness of this event as a biostratigraphical datum is limited by the inconsistency of identification between different authors and its rare occurrence in most areas.

Last common/abundan t occurrence of Repagulum parvidentatum
This biostratigraphical datum was used by Jakubowski (1987) to define the top of his R. parvidentatum Zone (NLK 5 ) in the Middle Albian of the Moray Firth (North Sea, offshore UK).
At Munday's Hill, common/abundant R. parvidentatum occurs through the Middle Albian and into the base of the Upper Albian (cristatum Subzone). Repagulum parvidentatum is also common in sample 45 from the varicosum-auritusSubzones. It has been observed to be common/abundant when co-occumng with E. turriseiffelli on the Mre-Trondelag Platform offshore Norway (Crux, unpublished). It thus appears that the last common/abundant occurrence of R. parvidenfatum is unreliable as a biostratigraphical event. It is diachronous and can repeat itselfin the same area. A further problem is that Jakubowski (1987) did not define the terms common and abundant.

FAD of Tegulalithus tessellatus
The FAD of T. tessellatus is recorded in the varicosuwur-itus Subzones of Munday's Hill. Other records of this species include Stradner, etal. (1968) from the Albian of Holland, Black (1973) from the Upper Albian of England, Thierstein (1973) from the Upper Aptian (Lithastrinus septentr-ionalis) and Roth ( 1983) from the Upper Aptian to Lower Albian of the western North Atlantic (L.  septentrionalis). Roth's (1983) record is not illustrated and his range chart shows two occurrences ofL. septentrionalis. It is probable that the higher record is of T. tessellatus, which many authors consider synonymous with T. septentrionalis. It appears that T. tessellatus has an earlier first occurrence outside north-west Europe than it does in the English Gault. The FAD of this species could be used as a local biostratigraphical event, but it is unreliable over great distances.
been documented by Hill (1976), Verbeek (1977), Perch-Nielsen (1979, 1985 and Hill and Bralower (1987). In the Munday's Hill section, this first Eiffellithus species, E. monechiae, occurs in samples 45 and 46 from the varicosuauritus Subzones. This biostratigraphical datum has been recorded from Tunisia, northern Europe and the USA. It therefore appears to be useful for inter-regional correlation

FAD of Eiffellithus monechiae
Opinions on the taxonomic divisions recognised in the early Eiffellithus species differ from author to author. Most authors agree that in the Upper Albian, species of Eiffellithus, with a central cross approximately aligned with the long and short axes of the elliptical coccolith (although often referred to as Vekshinella angusta), occur below the level ofthe first E. turrisezffeli. This sequence of events has

REGIONAL PALAEOGEOGRAPHY AND PALAEOCEANOGRAPHICAL RECORD
The north-west European Mid and Late Albian epicontinental seaextended from south-east Englandacross the North Sea, Denmark, northern Germany, Poland and into the USSR (Fig. 1). A shallow marine connection existed across north-east France to Tethys. Intermittent shallow marine connections may have existed along the Albian calcareous nannofossils present day English Channel. These are shown on the generalised marine clays were deposited at the Munday's Hill area. At the end of palaeogeographic maps for the Aptian-Albian and Albian of both the Middle Albian, a short but widespread period of regression and Ziegler (1982) and Tyson and Funnel1 (1987). Owen's (1976) erosion removed the uppermost Middle Albian sediments from reconstruction of the Middle Albian shows no such connection. A Munday's Hill and much of north-west Europe. This regression has narrow deep marine connection between the Shetland Platform and been linked to the onset of sea floor spreading in the Rockall Trough Norway linked this north-west European sea with Svalbard and east (Roberts et al., 1981). Owen (1976) considered that these tectonic Greenland and possibly the Arctic Ocean. Another deep water disturbances at the end of the Middle Albian opened an ephemeral connection is shown by Z,iegler (1982) linking the proto-Atlantic connection between the Arctic and the European seas. Tectonic with the northern North Sea along the Rockall Trough-Faroe Rift.
disturbances caused a further transgression in the crisfutztni Subzone The extent of the north-west European epicontinental seavaried at the beginning of the Late Albian. Marine connections were once with the occurrenceof regional transgressions and regressions. These again established with the Tethys-Proto-Atlantic area through the also affected the marine connections with other areas. Owen (1976) Polish Trough and the Paris Basin and presumably the Bay of Biscay reportedanexpansion ofthe areaofmarinedeposition at the beginning and the Rockall Trough (Ziegler, 1982). The two transgressions of the Middle Albian. This transgression reached a maximum in the discussed above can possibly be related to the global 3rd order cycles infermedius Subzone when the first Albian nannofossil bearing UZA-1.3 to UZP-1.4 and UZA-1.5 to the base of UZA-2. I of coastal Albian calcareous nannofossils onlap change as described by Haq et al. (1988), although these correlations are tentative partly because of local tectonics and erosion. Haq et al. (1988) used sections in nearby northern France to define their cycles, so some relationship would be expected. Owen( 1971Owen( ,1973Owen( and 1976recognisedarelationship between palaeogeography and the distribution of ammonite faunas during the Albian. He defined a Hoplitinid ammonite province in the Middle Albian European epicontinental sea. The hoplitinids were the predominant group of ammonites from the Anglo-Paris Basin eastwards to the USSR. The ammonite faunas show evidence for links with the Arctic north of Spitsbergen and east Greenland only during the dentatus Zone. Although marine connections with Tethys to the south exisited, the hoplitinids remained in northem Europe. Typical Tethyan ammonites did occasionally migrate northwards, especially in the lyelli and the subdelaueri Subzones. Tectonic disturbance and renewed transgression at the beginning of the Late Albian allowed the Arctic-North American genus Gastropolites to enter and co-occur with the hoplitinid fauna in Spitsbergen, east Greenland and southern England. At the same time, in the cristutum Subzone, Tethyan ammonite genera entered from the south and persisted in the north-west European region throughout the Late Albian. A distinct Hoplitinid province was still present in the European area throughout the Late Albian. Michael (1979) recognised a relationship between palaeogeography and the distribution of foraminifera. He identified increases of warm water dextrally coiled benthic and planktonic foraminifera1 faunas into the European sea at the base of the Middle Albian and during the Late Albian and Cenomanian. Michael (1979) also observed an increase in Tethyan planktonic and benthic foraminifera from the Middle to Upper Albian.

Results of abundance counts
Abundance counts were performed on ten taxa in order to evaluate their significance as palaeoenvironmental indicators (Figs. 3 and 4). The species were chosen because it was observed in the initial analysis that they significantly varied in abundance in different parts of the section, and that they were common enough to make abundance counts meaningful.
Rhagodiscus achlyostaurion, R. asper and R. splendens show a preference for conditions during the topmost niobe Subzone and during the cristatum, orbigny and the lower half of the varicosullt auritics Subzones, afteralowpoint in the lowermostcristatum Subzone. Rhagodiscus asper and R. splendens were previously sugested to prefer warm surface waters by Roth and Krumbach (1986). As R. achlyostaurion shows a similar distribution pattern to these two species, it appears that R. achlyostaurion may also prefer warm waters.
Repagulum parvidentatum, S. primitivum and S. matalosus have similar distributidn patterns and show distinct preferences for conditions during the spathi to niobe Subzones. Amedro et al. (1981) recorded S. primitivum as common in the E . turriseiffeli Zone at Boulonnais, northern France. In the North Sea, Jakubowski (1987) found this species to be abundant up to a level just below the top of the Albian, although his record is based on oil company ditch cuttings samples which give less precise information. Seribiscutumprimitivum co-occurs with E. turriseiffeli incore samples from the Mre-Trondelag Platform (offshore Norway) where it comprises up to 5% of the nannofossil flora (Crux, unpublished) which confirms that S. primitivum is a high latitude species. Repagulum parvidentatum is known to prefer high latitudes which thus appear to be the case also for S. matalosus. Lithastrinus sp. and T. orionatus possibly prefer high latitudes, however, they show a slightly different abundance pattern to R. pawidentatum and S. primitivum, as they are most common in the upper part of the varicosu-uritus Subzones. Tranolithus orionatus, which has been reported as a high latitude species (Roth, 1983) is most abundant at the beginning of the cooling event in the upper Albian. However, T. orionatus evolved shortly before the base of the studied section, and its relatively low abundance in the middle Albian may reflect that this species was not yet established. Common for all the high latitude nannofossil species are low abundances in the orbigny through the lower half of the varicosum--auritus Subzones and higher abundances in the Middle Albian, in the cristatum Subzone and in the upper half of the varicosu-uritus Subzones. It appears that R. angustus has a weak preference for the conditions preferred by high latitude nannofossil species. The abundance pattern of P . cretacea is ambiguous to interpret and may indicate nutrient levels.

Low latitude and endemic species
Nannofossil taxathought to prefer low latitudes occur in relatively low numbers throughout the Munday 's Hill section. Hayesites albiensis appears to have a shorter stratigraphic range than in lower latitudes and R. irregularis is absent. Rhagodiscus asper, R. splendens, Z. erectus, F. oblongus and Nannoconus spp. are less common than they are reported to be in lower latitudes.
Braloweria boletiformis and Ceratolithina hamata have never been observed outside north-west Europe and appear to be endemic to this area. This may also be the case for Gaarderella granulifera, which outside north-west Europe has only been tentatively observed in thePacific and Atlantic oceans (Roth, 1981(Roth, ,1983. (See discussion in Taxonomy). Gaarderella granulifera occurs in both the Middle and Upper Albian at Munday's Hill. It has also been recorded from the Middle and Upper Albian at Copt Point and localities in eastern England (Black, 1973). The only reported observations of B. boletiformis are restricted to the Middle Albian, where it also occurs at Munday's Hill. A closely related form, Braloweriajudithae, was reported by Black (1972) from the Upper Albian of eastern England. Ceratolithina hamata is present in both the Middle and Upper Albian at Munday's Hill. It has previously been recorded from the Middle Albian of Germany (Martini, 1967), Middle Albian Copt Point (Perch-Nielsen, 1988) together with the closely related forms C. cruxii and C. bicornutu (Middle to Upper Albian) and from the Albian of an oil well onshore The Netherlands (Crux, unpublished).

High latitude nannofossil species
Nannofossils identified in previous studies to have high latitude preferences occur throughout the Munday's Hill section but their abundance vary at different levels, being most common in the cristatum Subzone and in the upper half of the varicosu-uritus Subzones (Figs. 5 -7). Biscutum dissimilis and S. falklandensis were not observed. These species have only ever been recorded from the high latitudes of the southern hemisphere.

Environmental indicators
Most of the species identified in previous studies as being more common in epicontinental and continental margin seas, show little variation in their distribution through the Munday's Hill section (Figs. 5-7). The two most common species in this group are B. ellipticum and Z. noeliae which are slightly more abundant in the Upper Albian than in the Middle Albian. Braarudosphaera spp. and Nannoconus spp. are absent in the lower part of the Middle Albian at Munday's Hill.
No distinctive patterns are observed in the distribution of species previously found to indicate high fertility and unstable environments. Watznaueria barnesae, the only species whose high abundance has been identified as indicating oceanic conditions, is abundant throughout the section, becoming very abundant in two poorly preserved samples (33 and 34) and also in sample 22.

NANNOFLORAL DEVELOPMENT AND PALAEOCEANOGRAPHICAL IMPLICATIONS
The earliest stratigraphic records of Crucicribrum anglicum are from the Aptian and Lower to Middle Albian of the relatively shallow water, high latitude, Falkland Plateau and the marginal epicontinental seas of Texas and north-west Europe. It thus appears that this species evolved in shallow, high latitude seas and only occurred in low latitude deep water areas from the Late Albian to Cenomanian. This pattern would agree with other authors observations concerning the closely related genera Broinsonia, Gartnerago and Kamptnerius. These have been recognised to occur more abundantly inshallow shelf seas (Thierstein, 1976;Hartneretal., 1981;Rothand Bowdler, 1981) and to occur earlier in high latitudes (Kamptnerius magnificus (Thierstein, 1976)).
A decrease in abundance of R. parvidentatum was noted by Jakubowski (1987) in the Moray Firth and by and Erba et al. (1989) in the Middle Albian of southern England. Wise (1983) shows in his nannofossil distribution chart of DSDP Site 5 1 1 from the Falkland Plateau, a reduction in numbers of R. parvidentatum at the top of his T. orionatus Subzone. At the same level occurs the 1astS.falklandensis.

Albian calcareous nannofossils
The record of the abundance decrease of R. parvidentatum by Erba et al. (1989) is stratigraphically earlier than observed in the present study. This would suggest that the abundance decrease of R. parvidentatum is diachronous, occurring later at Munday 's Hill than in southern England. It is possible that the reduction in abundance of this cold waterprefening species, occurred first at lower latitudes and moved diachronously towards higher latitudes in both hemispheres. Unfortunately, neither Wise's (1983) or Jakubowski's (1987) records are precisely dated by ammonites to give us further data on this. However, it is likely that this event indicates reduced influences of cold surface watermasses. Erbaetal. (1989) favoured a transgressive event displacing the Arctic watermasses of which R. pawidentaturn was characteristic, to have caused its abundance decrease. In the Munday 's Hill section, R. parvidentatum returns with increased abundances in the upper half of the varicosum-auritius Subzones, however, it does not become as common as in the Middle Albian. No return of R. parvidentatum during the Albian is noted in the southern hemisphere at DSDP Site 5 1 1.
Other species previously identified to have high latitude affinities also show some increase towards the top of the Munday's Hill section, in particular, S. primitivum, S. horticus, Z . noeliae and T. tessellatus in combination with species suggested in this study to prefer colder waters; Lithastrinus sp., R. angustus and S . matalosus. In the southern hemisphere, Wise (1983) reportedS.primitivum to be common through the upper part of his P . cretacea Zone, becoming abundant just before the FAD of E. turriseiffeli. This abundant occurrence continues through the E. turriseiffeli Zone. A similar pattern was also recorded by Wise and Wind (1977) from the Falkland Plateau and by Thierstein (1974) at DSDP Site 258 in the high latitudes of the Indian Ocean. It thus appears that the advance of colder surface waters in the late inflatum-dispar Zone occured in both the northern and southern hemispheres.
When marine sedimentation commenced at Munday's Hill in the spathi Subzone, the nannofloras were abundant and diverse. Forty species were present in the lowermost sample from the spathi Subzone, rising to 59 species in the niobe Subzone (Fig. 3). High total abundances and diversified nannofossil assemblages persisted throughout the studied section, suggesting that the Munday 's Hill area continuously had marine connections with areas outside northwest Europe. The continuous presence, although in relatively low abundances, of species with low latitude affinities, indicates inflow of waters from the Tethys and proto-Atlantic seas. The approximately synchronous FAD'S of Axopodorhabdus albianus, Owenia hilli and Ezflellithus monechiae, at Munday's Hill and at more southerly localities, supports this view.
The distribution of low latitude and endemic nannofossil species is similar to their ammonite counterparts. The species identified as being endemic to north-west Europe, could possibly also be present in the high latitude Boreal/Arctic as we know little about the nannofossils of these areas. However, they were not reported from the Moray Firth area (North Sea, offshore UK) by Jakubowski (1987) and have not been observed by the author in oil company wells offshore Norway. Furthermore, they do not have the bipolar distribution patterns of other high latitude nannofossil species. However, further studies outside north-west Europe are needed to definitely prove the existence of an endemic nannoflora, although these species were not reported in recent studies by Bralower (pers. comm.).
The nannofossil abundancepatterns in north-west Europe suggest that the relatively colder environment near the beginning of the Middle Albian gradually warmed up towards the regressive event at the end of the Middle Albian. In the Upper Albian, this general trend was temporarily interrupted in the lower cristatum Subzone, where high latitude species increase in abundance. Warmer conditions were established by the orbigny Subzone and persisted through the lower half of the varicosu-uritus Subzones. During the upper half of the varicosumauritus Subzones, intermediate to cold surface waters may have prevailed.
This does not completely agree with Kemper (1987), who studied the distribution of pseudomorphs of glendarites and considered the Middle to Late Albian to be a period of climatic stability. The nannofossil abundance patterns show similarities to results obtained from foraminifera. Michael (1979) analysed the coiling direction of the foraminifera Gavelinella spp. (benthic) and Hedbergella (planktonic) through the Albian. During the Middle Albian 50 -60 % were sinistrally coiled, indicating cold water conditions. However, a peak of dextrally coiled forms were found at the base of the Middle Albian. This is probably below the base of the Munday 's Hill section. The number of sinistral forms dropped rapidly to 40% at the Middle to Upper Albian boundary, indicating somewhat warmer conditions. Higher in the Upper Albian, 50 % of the foraminifers were sinistrally coiled, before dropping to 35 % by the end of the Albian. Unfortunately, it is not possible to precisely correlate the foraminifer results to the nannofossils, as Michael (1979) did not relate his study against ammonite zones and subzones. His definitions of the Middle and Upper Albian may be different from those used in this study.
The decline in abundance of high latitude nannofossils observed through the uppermost dentatus to loricatus ammonite Zones

SYSTEMATICS
Taxonomic references not included in the reference list can be found in Perch-Nielsen (1985) and in the INA Newsletter.

Class Haptophyaceae Christensen 1962
Order Prymnesiales Papenfuss 1955Suborder Coccolithineae Kamptner 1928 Family Biscutaceae Reinhardt 1964 Genus Crucibiscutum Jakubowski 1986 Crucibiscutum hayi (Black 1971) Jakubowski 1986 Crucibiscutum salebrosum (Black 1971) Jakubowski 1986 Remarks. Large and small forms of Crucibiscutum have been divided into C. hayi and C. salebrosum respectively. Jakubowski (1987) used the extinction of C. salebrosum to define a zone within the Barremian of the Moray Firth. However, several authors have recorded this species from younger strata. In addition Crux (1989;PI. 8.10, figs 29-30) recorded the large forms (C. hayi) from the Hauterivian. It thus appears that both forms range throughout most of the Lower Cretaceous and their division on size alone is of doubtful value. The two forms were counted as one taxonomic unit in the present study.
Genus Gaarderella Black 1973 Gaarderella granulifera Black 1973 Remarks. Roth (1981) reported G . cf. G . granulifera from the Mid Pacific Mountains, and illustrated the species with a light micrograph (Roth (1981) P1. 1, figs 5a, b). The illustrated specimen has a narrow .rim with both the outer and inner parts brightly birefringent. In the specimens of this study, the rim is broader and only the inner part is observed to be bright (Pl. 2, fig. 20). In Roth's specimen, the birefringence pattern of the rim indicates that it is imbricate, however, Black (1973) described G. granulifera as having anon imbricate rim. Roth (1983) also recorded G. granulifera from the Aptian of DSDP Site 534 located on the Blake Bahama Basin, but did not illustrate the rare specimen recorded. In conclusion, the presence of G. granulifera in both the Atlantic and Pacific oceans are not verified. (Pl. 2, Family Calyptrosphaeraceae Boudreaux andHay 1969 Genus Calculites Prim andSissingh in Sissingh 1977 Calculites sp. 1 (Pl. 1, fig. 4; P1.2, figs 5 and 6) Description. Small elliptical holococcolith with a central perforation.

Remarks.
No distal view of this species was seen in the scanning electron microscope (SEM). Its assignment to the genus Calculites is only tentative, it does not appear to fit into any other described genus of holococcolith.
Calculites sp. 2 (Pl. 2, Fig. 7) Description. Small bright holococcolith which was only observed under the light microscope. It appears to have a single large central perforation. It differs from Calculites sp. 1 by possessing a distinctive extinction pattern between x-nicols which divides the rim into four unequal segments, two small and two large. Remarks. Its assignment to Calculites is only tentative, it does not appear to fit into any other described genus of holococcolith.  al. (1990). The two species differ in the construction of their bridges, 0. partium is reported and illustrated as appearing to have a cross formed of four elements in X-nicol light. The bridge of 0. hilli is composed of numerous crystals, which do not appear as a cross in X-nicol light. Family Crepidolithaceae Black 197 1 Genus Braloweria gen. nov. Black 1972 Derivation of name. After T. J. Bralower, nannofossil specialist. Diagnosis. Elliptical heterococcolith with a loxolith rim structure, the central areas is completely filled with a large single hollow spine composed of numerous laths of calcite. This spine may flare or taper distally. Remarks. This genus differs from Parhabdolithus Deflandre 1952 in its rim structure. In Braloweria, the rim is of a loxolith structure  Fig. 6. Owenia hilli n. sp., distal view, sample 23. Fig. 7. Crucicribrum anglicum, proximal view, sample 12. Fig. 8. Braloweria holetiformis, side view, sample 17. Fig. 9. Braloweria holetiformis, distal view, sample 17. Fig. 10. Braloweria boletiformis, side view, sample 17. Fig. 11. Braloweria boletiformis, distal view, sample 17. Fig. 12. Repagulum parvidentatum,  Derivation of name. After S. Monechi, nannofossil specialist Diagnosis. A species of Eiffellithus whose central cross is aligned within 20 of the major axes of the elliptical coccolith. The blocky plates of the central area are equal or greater in width than the rim, but do not tat%lly fill the centre. Holotype. Hill and Bralower, 1987, P1.2, fig. 3. Type locality and horizon. Locality 6264 Hill (1976). North bank of Red River just E. of bridge of US highway 75 just below Texhoma Dam Oklahoma. Duck Creek Formation, Upper Albian.

Type species Parhabdolithus boletiformis
Dimensions. Length 4.7 -6 p , width 3.4 -4.6 pn, 3 specimens measured. Remarks. Eiffellithus monechiae is differentiated from E. eximius by its stratigraphic range, Upper Albian to lowest Cenomanian, rather than the Turonian to Maastrichtian of E. eximius. It is also differentiated by a narrower cycle of blocky elements in the central area although this may vary considerably due to preservation.
Hill andBralower (1987) groupedE. monechiae withE. eximius on the basis that they found E. eximius in the basal Turonian sediments and that they considered it probable that it was present throughout the Cenomanian in very low numbers and as yet undetected by them and other authors. I believe that E. monechiae evolved from S . angustus in the Late Albian and in turn E. turriseiffeli evolved from it. In the Turonian, E. eximius evolved from E. turrisecffeli. Thus the two forms, although morphologically similar, are different species. This is also a pragmatic approach as the first occurrences of both species are useful as biostratigraphical datums. Staurolithites angustus is differentiated from E. monechiue as the blocky elements in the central area are narrower than the outer rim. This definition may be difficult to apply in poorly preserved material where the elements are overgrown, but has worked in sections I have examined from northwest Europe.
Description. Large species oflithastrinus, with 10 ormore elements. It appears to be similar to L. planus but has more elements.
Family Prediscosphaeraceae Rood, Hay and Bamard 1971 Genus Prediscosphaera Vekshina 1959 Prediscosphaera cretacea (Arkhangelsky 19 12) Gartner 1968 Remarks. Prediscosphaera cretacea as used in this study also probably includes Prediscosphaera columnata (Stover 1966) Perch-Nielsen 1984. The two species can only be differentiated when their spines are preserved, which is infrequently, thus a more practical approach is to group them as one species.

CONCLUSIONS
The last occurrence of Braloweria boletiformis is a reliable biostratigraphic datum within south-east England. The first occurrences ofhopodorhabdus albianus, Owenia hilli and Ezffellithus monechiae appear to be reliable world-wide biostratigraphical datums. The last occurrence of commonlabundant Repagulumparvidentatum is diachronous, occurring earlier in low latitudes. The last occurrence of Hayesites albiensis is also diachronous, occurring earlier in high latitudes. The first occurrence of Corollithion signum is an unreliable biostratigraphic event. This species evolves gradually from Corollithion achylosum and thus, its FAD is difficult to define consistently.
A nannofossil floral province, unique to north-west Europe, existed through both the Middle and Upper Albian. Three species, B . holetijiomis, Ceratolithina hamata (and the closely related C. hicornuta and C. cruii), and Gaarderella granulifera, appear to be endemic to north-west Europe.
The occurrence of low latitude nannofossil species throughout the Munday's Hill section, and the nearly synchronous first and last occurrences of species both at Munday's Hill and in other areas, indicates marine connections with the Tethys-Proto-Atlantic areas throughout the Middle and Upper Albian interval studied.
Decreasing abundances of high latitude nannofossil species, primarily R. parvidentatum and S. primitivum, through the Middle Albian suggest that arelatively cold environment near the base of the Middle Albian gradually warmed up towards the regressive event at the end of the Middle Albian. This general trend was temporarily interrupted at the base of the Upper Albian (lower cristatum Subzone), when high latitude species increased in abundance. Low abundances of high latitude nannofossil species suggest that relatively warm surface water conditions were established by the orbigny Subzone and persisted through the lower half of the varicosunz--auritus Subzones. These trends are supported by conclusions based on ammonite and foraminifera1 data in previous studies.
This study suggests that Rhagodiscus achlyostaurion increases in abundance in warmer waters and that Rhagodiscus angustus shows a weak preference for colder conditions. Also, Staurolithites matalosus is a cold water preferring species.