Chatangiella islae and Trithyrodinium zakkii, new species of peridinioid dinoflagellate cysts (Family Deflandreoideae) from the Coniacian and Campanian (Upper Cretaceous) of the Norwegian Sea

Review of Palaeobotany and Palynology 271 (2019) 104080

Contents lists available at ScienceDirect

Review of Palaeobotany and Palynology journal homepage: www.elsevier.com/locate/revpalbo

Research papers

Chatangiella islae and Trithyrodinium zakkii, new species of peridinioid dinoflagellate cysts (Family Deflandreoideae) from the Coniacian and Campanian (Upper Cretaceous) of the Norwegian Sea Martin A. Pearce a,⁎, Catherine E. Stickley a, Linn M. Johansen b a b

Evolution Applied Limited, Cotswold Business Centre, 2 A P Ellis Road, Upper Rissington, Gloucestershire GL54 2QB, UK Equinor Energy AS, Svanholmen 8, Forus, Norway

a r t i c l e

i n f o

Article history: Received 19 February 2019 Received in revised form 12 May 2019 Accepted 16 June 2019 Available online 20 June 2019 Keywords: Chatangiella Trithyrodinium Dinoflagellate cyst New species Late Cretaceous

a b s t r a c t Two new species of deflandreoid dinoflagellate cysts are described from the Coniacian and Campanian from the 6406/3–6 well, Tyrihans Field in the Norwegian Sea. Chatangiella islae sp. nov. possesses spines that are uniquely restricted to the cingulum, while Trithyrodinium zakkii sp. nov. is distinguished from other species of the genus by spines arising from the endophragm. These species have been known under various informal (and invalid) names and are very important biostratigraphic markers in the North, and Norwegian–Greenland seas. © 2019 Elsevier B.V. All rights reserved.

1. Introduction

2. Materials

During a study of multiple production wells from the Equinor Energy AS Heidrun and Heidrun North wells (block 6507/7) in the Norwegian Sea, two distinctive undescribed dinoflagellate cyst (hereafter dinocyst) species were observed. As the Heidrun fields are currently being actively produced, all biostratigraphic data from production wells are deemed strictly confidential by Equinor Energy AS and its licence partners and therefore, the necessary information required to publish species from Heidrun material is unavailable. In an effort to find publicly available material containing these species close to the Heidrun fields, the Equinor Energy AS well 6406/3–6 from the Tyrihans Field, ca. 60 km SSW of the Heidrun Field, was identified as a candidate. From the 6406/3–6 well, holotype, paratype and additional specimens for the new species Chatangiella islae sp. nov. and Trithyrodinium zakkii sp. nov. have been described, photographed and are presented here. The biostratigraphic data for this well are available online from the NORLEX database, hosted by the University of Oslo, and our chronostratigraphic interpretation is based on these data. Lithostratigraphic information is available from the Norwegian Petroleum Directorate.

The Tyrihans field is located between blocks 6406/3 and 6407/1 in the Halten Bank on the Norwegian continental shelf, approximately 225 km to the NW of Trondheim (Fig. 1). Tyrihans was discovered in 1983 by Equinor Energy AS (then Statoil ASA) with the 6407/1–2 exploration well, and the 6406/3–6 well (64° 47′ 43.56” N, 6° 57′ 55.17″ E) was drilled by Equinor Energy AS in 2002 to appraise the western flank of the discovery. Gas and condensate production from Tyrihans commenced in 2009. Equinor Energy AS kindly supplied palynological slides for the 6406/3–6 well, from which holotypes, paratypes and additional specimens for the two new species were described and photographed.

⁎ Corresponding author. E-mail address: [email protected] (M.A. Pearce).

https://doi.org/10.1016/j.revpalbo.2019.06.003 0034-6667/© 2019 Elsevier B.V. All rights reserved.

3. Systematic paleontology The classification herein follows Fensome et al. (1993) and Williams et al. (2017a, 2017b). The Kofoidian notation is applied to tabulation, and morphological terminology is taken mainly from Lentin and Williams (1975), Bujak and Davies (1983) and Evitt (1985). All slides are lodged at the British Geological Survey (BGS), in Keyworth, Nottingham, UK. England Finder (EF) coordinates are provided for type and reference specimens. The coordinates are taken with the slide label to the right. Division: DINOFLAGELLATA (Bütschli, 1885) Fensome et al., 1993 Subdivision: DINOKARYOTA Fensome et al., 1993

M.A. Pearce et al. / Review of Palaeobotany and Palynology 271 (2019) 104080

3

Fig. 1. Location map of the Heidrun and Heidrun Nord fields and the study wells.

Class: DINOPHYCEAE Pascher, 1914. Subclass: PERIDINIPHYCIDAE Fensome et al., 1993 Order: PERIDINIALES Haeckel, 1894. Suborder: PERIDINIINEAE (Autonym). Family: PERIDINIACEAE Ehrenberg, 1832. Subfamily: DEFLANDREOIDEAE Bujak and Davies, 1983. Genus: Chatangiella Vozzhennikova, 1967 emend. Lentin and Williams, 1975 emend Fensome et al., 2016 Type species: Chatangiella niiga Vozzhennikova, 1967, pl. 56, fig. 1; pl. 57, fig. 1. Remarks: Vozzhennikova (1967) described Chatangiella essentially for bicavate dinocysts, sculptured on the periphragm, with an apical horn, two antapical horns and a large polygonal archaeopyle. Lentin and Williams (1975) emended the generic description to include weakly circumcavate forms that may possess a smooth to sculptured periphragm, and significantly, with a pentapartite cingulum. The Type I2a periarchaeopyle, was also stated to be omegaform. An emendation by Marshall (1988), who broadened the generic description to include forms with sutural ridges, was rejected by Lentin and Vozzhennikova (1990), who transferred such species to Arvalidinium. Although not being a formal emendation, Fensome et al. (2009) provided a synopsis that accepted a periarchaeopyle range from iso-deltaform to (typically) iso-omegaform. This variability in the archaeopyle shape was reconsidered by Fensome et al. (2016) to be lati- to iso-omegaform in their emended generic description. However, the use of archaeopyle shape in peridiniods as a generic feature is not clear-cut. For example, morphological variability in the Deflandreoideae occurs in Deflandrea (originally Isabelidinium) majae (Schiøler, 1993) Fensome et al., 2016, where a range of archaeopyle shapes from steno-deltaform to lati-deltaform is apparent from Schiøler's material and our personal observations. In D. majae, archaeopyle width appears to be directly related to pericyst width, but Fensome et al. (2016) recommend that the steno-deltaform variants be included in another genus. Also, the wetzelielloideans Petalodinium sheppeyense Williams et al., 2015 and Rhadinodinium politum (Bujak et al., 1980) Williams et al., 2015 have an arguably identical ambitus, and excluding the archaeopyle shape, apparently only differ by ornamentation. In both examples above, the generic assignments are based essentially on differences in archaeopyle width. Variations in the length of

H2–H3 and H5–H6 (see Lentin and Williams, 1975, text-fig. 3a) at the left and right lateral margin of the 2a periarchaeopyle (i.e., from deltaform to omegaform) is also apparent in deflandreoid dinocysts associated with the development of ‘shoulders’ on the epicyst. Examples include the holotypes of Chatangiella turbo Harker et al., 1990 ex Harker and Sarjeant, 1991 that has a deltaform H2–H3 (left lateral) margin and possibly a thetaform H5–H6 (right lateral) margin and poorly developed shoulders, C. ditissima (McIntyre, 1975) Lentin and Williams, 1975 and C. spectabilis (Alberti, 1959) Lentin and Williams, 1975 have a thetaform 2a and moderately developed shoulders, whereas C. coronata (McIntyre, 1975) Lentin and Williams, 1975 and C. verrucosa (Manum, 1963) Lentin and Williams, 1975 have an omegaform 2a (possibly also in the type species, C. niiga Vozzhennikova, 1967) and well-developed shoulders. A re-evaluation of deflandreoid genera is clearly needed, but beyond the scope of the present work. Chatangiella islae sp. nov. Plate I, 1–9; Plate II, 1–9, Plate III, 1–9, Fig. 3. (?)1967 Chatangiella victoriensis Cookson and Manum — Clarke & Verdier, pl.3, figs. 8–9. 2015 Chatangiella “spinosa” Radmacher et al., fig. 5. Derivation of name: For Isla, daughter of M.A. Pearce and C.E. Stickley. Holotype: Plate I, 1–3, from a cuttings sample from the Kvitnos Formation at 2980 m, Tyrihans Well 6406/3–6 (Coniacian?); England Finder co-ordinate: J8/1. Endocyst (width × length): 42 × 50 μm, pericyst length: 67 μm, maximum spine length: 3 μm. BGS catalog number UKBGS.MPK14660. Paratypes: All from a Kvitnos Formation cuttings sample at 2980 m, Tyrihans Well 6406/3–6. Paratype 1, Plate I, figs. 4–6, endocyst (width × length) 40 × 43 μm, pericyst length 76 μm, maximum spine length 4 μm, EF: K9/2. Paratype 2, Plate I, figs. 7–9, endocyst (width × length) 48 × 51 μm, pericyst length 83 μm, maximum spine length 4 μm, EF: J7/2. Paratype 3, Plate II, figs. 1–3, endocyst (width × length) 53 × 50 μm, pericyst length 86 μm, maximum spine length 4 μm, EF: K17/2. Paratype 4, Plate II, figs. 4–6, endocyst (width × length) 36 × 39 μm, pericyst length 77 μm, maximum spine length 3 μm, EF: K24/2. Paratype 5, Plate II, figs. 7–9, endocyst (width × length) 48 × 46 μm, pericyst length 79 μm, maximum spine length 3 μm, EF: J10/2. Paratype 6, Plate III, figs. 1–3, endocyst (width × length) 45 × 54 μm, pericyst length 96 μm, maximum spine length 5 μm, EF: J14/1. Paratype 7, Plate III, figs.

4

M.A. Pearce et al. / Review of Palaeobotany and Palynology 271 (2019) 104080

Plate I. 1–9 Chatangiella islae sp. nov. Specimens recovered from Tyrihans 6406/3–6 well, cuttings sample 2980 m (Kvitnos Formation), lacking epicystal ‘shoulders’. 1–3, holotype, EF: J8/1. 4–9 Paratype 1, EF: K9/2. 7–9, Paratype 2, EF: J7/2. The scale bar represents 20 μm.

M.A. Pearce et al. / Review of Palaeobotany and Palynology 271 (2019) 104080

5

Plate II. 1–9 Chatangiella islae sp. nov. Specimens recovered from Tyrihans 6406/3–6 well, cuttings sample 2980 m (Kvitnos Formation), with moderately developed epicystal ‘shoulders’. 1–3 Paratype 3, EF: K17/2. 4–6 Paratype 4, K24/2. 7–9 Paratype 5, J10/2. The scale bar represents 20 μm.

6

M.A. Pearce et al. / Review of Palaeobotany and Palynology 271 (2019) 104080

Plate III. 1–9 Chatangiella islae sp. nov. Specimens recovered from Tyrihans 6406/3–6 well, cuttings sample 2980 m (Kvitnos Formation). 1–3 Paratype 6, EF: J14/1. 4–6 Paratype 7, EF: J33/ 3. 7–9 Paratype 8, EF: J34/4. The scale bar represents 20 μm.

M.A. Pearce et al. / Review of Palaeobotany and Palynology 271 (2019) 104080

7

Fig. 2. Biostratigraphic distribution chart of marker species from the 6406/3–6 well. The position of the 9 5/8 in. casing shoe is indicated. Ly = Lysing Formation. The event suffixes in parentheses: C = common, A = abundant. Abbreviations in the gamma log trace indicate the position of the type material of Chatangiella islae sp. nov. (Ci) and Trithyrodinium zakkii (Tz).

4–6, endocyst (width × length) 50 × 53 μm, pericyst length 93 μm, maximum spine length 4 μm, EF: J33/3. Paratype 8, Plate III, figs. 7–9, endocyst (width × length) 48 × 49 μm, pericyst length 79 μm, maximum spine length 3 μm, EF: J34/4. Diagnosis: A species of Chatangiella with a granular endophragm and a periphragm possessing spines on the anterior and posterior margin of the cingulum only.

Description: Intermediate-sized, bicavate, deflandreoid peridinioid dinoflagellate cyst. The wall is two-layered composed of a finely to moderately granular endophragm (1 μm thick) and a smooth to finely granular periphragm (~0.5 μm thick) that possesses spines on the anterior and posterior margin of the cingulum only. The spines are typically 4 μm in length (varying between and within specimens), rounded, pointed or minutely bifurcating distally and may be connected at the

8

M.A. Pearce et al. / Review of Palaeobotany and Palynology 271 (2019) 104080

Fig. 3. Measurements of Chatangiella islae sp. nov. Black circles = endocyst dimensions, white diamonds = pericyst dimensions. Black and white star represents the dimensions of the holotype endocyst and pericyst, respectively.

base to 2 or 3 other spines. The spines are hollow or appear to be solid when they are particularly thin and delineates a pentapartite cingulum. The pericyst is ventrodorsally compressed, longitudinally elongate, forming a short and blunt apical horn, two antapical horns (right antapical horn shorter), and a bulge around the cingulum. Below the apical horn, the epipericyst typically lacks ‘shoulders’ and the ambital outline is typically slightly convex to the cingulum. Occasionally, specimens with moderately well-developed rounded to sub-angular shoulders are present. The hypopericyst is straight to tapering posteriorly. The endocyst is typically rounded, appressed to the lateral margin of the periphragm, resulting in a bicavation. Circumcavate forms have not been observed. The tabulation is defined by the nature of the archaeopyle and pentapartite cingulum, and the formula is presumably peridinioid. The parasulcus is not obvious. The endoarchaeopyle is Type I2a, the periarchaeopyle is typically Type I2a, iso-deltaform to isothetaform, and the perioperculum is detached. Rare specimens have been observed with well-developed ‘shoulders’ and an iso-omegaform periarchaeopyle. These are included in Chatangiella islae sp. nov., but are considered atypical. Dimensions in type material: Endocyst (width × length): 36(45.7)56 μm × 39(47.1)57 μm, pericyst length 67(83.2)98 μm (Fig. 3), maximum spine length, 1(3.6)5 μm. Number of specimens measured, 23.

Fig. 4. Measurements of the endocyst of Trithyrodinium zakkii sp. nov. The black star represents the dimensions of the holotype.

Comparison: Chatangiella islae sp. nov. differs from all other species of Chatangiella by possessing spines restricted to the anterior and posterior margin of the cingulum. It most closely resembles Chatangiella eminens Pearce, 2010 that differs by possessing intratabular spines on the precingular and postcingular plates. The cingular spines in C. eminens are also broader-based. Remarks: Chatangiella islae sp. nov. is known to occur in high relative numbers in the mid-Upper Cretaceous of the Norwegian–Greenland Sea, typically reaching over 20% of the entire assemblage (e.g., Fig. 2). Radmacher et al. (2015) state that C. islae sp. nov. (as Chatangiella “spinosa”) is common to abundant at the base of their Dinoptergyium alatum Zone that has a range of? intra Early Coniacian to Santonian. This species is well known to biostratigraphers working on material from the North Sea and Norwegian–Greenland seas, and has been reported under various informal names including Chatangiella “cingulispinosa” or C. “spinosa”. Genus: Trithyrodinium Drugg, 1967 emend. Lentin and Williams, 1975 emend. Marheinecke, 1992 emend. nov. Type species: Trithyrodinium evittii Drugg, 1967, pl. 3, fig. 2. Emended diagnosis: The emended generic diagnoses of Lentin and Williams (1975) and Marheinecke (1992) are accepted but the genus is further emended here to include species that possess spines on the endophragm. Remarks: Trithyrodinium was described by Drugg (1967) as differing from Deflandrea by exhibiting an intercalary Type 3I archaeopyle (apparently in both wall layers, judging by his illustration pl. 9 fig. 2) rather than intercalary Type I. Both the emendations of Davey (1969) and Lentin and Williams (1975) refer to the clear Type 3I endoarchaeopyle, but found the periarchaeopyle apparently problematic. Davey (1969) consider the latter to be intercalary Type I2a, and Lentin and Williams (1975) state that although frequently indeterminate, it is Type 3I(1a– 3a) with a standard (i.e., approximately iso-deltaform or slightly narrower) hexa 2a. Interestingly, Lentin and Williams (1975, p. 98) also mention the presence of a mesophragm: “Present in some specimens when it is appressed to the endophragm”, but did not provide more detail. This may be pertinent in considering T. partridgei Willumsen and Vajda (2010) as a legitimate species of Trithyrodinium. Marheinecke (1992) emended the description of the genus further in stating that the 2a plate is iso-deltaform. However, as pointed out by Fensome et al. (2016) many of the specimens from Marheinecke's material have a distinctly elongate (steno-deltaform) 2a. In discriminating species of Trithyrodinium, ornamentation is particularly significant and the generic emendation of Lentin and Williams (1975) state that the endophragm surface is laevigate, punctate, granulate, tuberculate or vermiculate; while in a modified description, Stover and Evitt (1978, p. 127) state that it is: “…variously ornamented with features of low to moderate relief”. In their synopsis of Trithyrodinium, Fensome et al. (2009, 2016), make no reference to ornamentation, and we therefore, consider the presence of spines in T. zakkii sp. nov. should not preclude this combination following a minor emendation. Trithyrodinium zakkii sp. nov. Plate IV, 1–12; Plate V, 1–12, Plate V, 1–6, Fig. 4. Derivation of name: For Zakk, son of M.A. Pearce and C.E. Stickley. Holotype: Plate IV, 1–3, from a cuttings sample from the Nise Formation at 2570 m, Tyrihans Well 6406/3–6 (Campanian); England Finder co-ordinate: T25/4. Endocyst (width × length): 65 × 64 μm, maximum spine length: 4 μm. BGS catalog number UKBGS.MPK14661. Paratypes: All from a Nise Formation cuttings sample at 2570 m, Tyrihans Well 6406/3–6. Paratype 1, Plate IV, figs. 4–6, endocyst (width x length) 68 × 70 μm, maximum spine length 3 μm, EF: L24/3. Paratype 2, Plate IV, figs. 7–9, endocyst (width × length) 63 × 68 μm, maximum spine length 4 μm, EF: P9/1. Paratype 3, Plate V, figs. 10–12, endocyst (width × length) 63 × 69 μm, maximum spine length 5 μm, EF: J25/1. Paratype 4, Plate V, figs. 1–3, endocyst (width x length) 65 × 63 μm, maximum spine length 4 μm, EF: J33/2. Paratype 5, Plate V, figs. 4–6, endocyst (width x length) 60 × 62 μm, maximum spine length

M.A. Pearce et al. / Review of Palaeobotany and Palynology 271 (2019) 104080

9

Plate IV. 1–9 Trithyodinium zakkii sp. nov. Specimens recovered from Tyrihans 6406/3–6 well, cuttings sample 2570 m (Kvitnos Formation). 1–3 Holotype, EF: T25/4. 4–6 Paratype 1, EF: L24/3. 7–9 Paratype 2, EF: P9/1. 10–12 Paratype 3, EF: J25/1. The scale bar represents 20 μm.

10

M.A. Pearce et al. / Review of Palaeobotany and Palynology 271 (2019) 104080

Plate V. 1–9 Trithyodinium zakkii sp. nov. Specimens recovered from Tyrihans 6406/3–6 well, cuttings sample 2570 m (Kvitnos Formation). 1–3 Paratype 4, EF: J33/2. 4–6 Paratype 5, EF: F17/1. 7–9 Paratype 6, EF: E30/4. 10–12 Paratype 7, EF: T30. The scale bar represents 20 μm.

M.A. Pearce et al. / Review of Palaeobotany and Palynology 271 (2019) 104080

11

Plate VI. 1–6 complete specimen of Trithyrodinium zakkii sp. nov. from a well in the Heidrun Field. The scale bar represents 20 μm.

4 μm, EF: F17/1. Paratype 6, Plate V, figs. 7–9, endocyst (width × length) 63 × 65 μm, maximum spine length 4 μm, EF: E30/4. Paratype 7, Plate V, figs. 10–12, endocyst (width × length) 72 × 68 μm, maximum spine length 4 μm, EF: T30. Diagnosis: A species of Trithyrodinium possessing short, minutely bifurcating spines on the endophragm.

Description: Intermediate to large (when complete) bicavate peridinioid dinoflagellate cyst. The wall is two-layered composed of a relatively thick and fibrous to spongy endophragm (~4 μm thick), and a thin and smooth periphragm (b1 μm) that is rarely attached. From the endophragm, densely arranged solid, non-tabular spines occur that are around 2–9 μm in length (although consistent on individual specimens) and flared to very weakly bifurcate distally. The

12

M.A. Pearce et al. / Review of Palaeobotany and Palynology 271 (2019) 104080

periphragm, when present, is longitudinally elongate, forming a broadbased and blunt apical horn, and two broad-based and blunt antapical horns (the right antapical horn being shorter), and being relatively loose fitting elsewhere. There is no evidence of tabulation, other than indicated by the archaeopyle. The endoarchaeopyle is intercalary Type 3I (1a–3a) and the endoperculum is detached. Too few specimens have been observed to identify the nature of the periarchaeopyle. The cingulum and sulcus are not clearly expressed. Dimensions in type material: Endocyst (width x length) = 53(65)75 × 61(68.3)77 μm (Fig. 4), maximum spine length = 2(4.3)9 μm. Number of specimens measured, 23. A complete specimen was observed from a Heidrun development well (Plate VI figs. 1–6): endocyst (width × length): 63 × 66 μm, pericyst (width × length): 74 × 130 μm, spine length (max.) 9 μm. In two specimens from the 6406/3–6 well, the maximum length of the antapical horns were 10 and 12 μm. Comparison: Trithyrodinium zakkii sp. nov. differs from Trithyrodinium suspectum (Manum and Cookson, 1964) Davey, 1969, to which it is most similar, by possessing spines. Trivalvadinium Islam, 1983 also possesses a Type 3I(1a–3a) archaeopyle and non-tabular spines. It was the synopsis of Stover and Williams (1987) and the formal emended diagnosis of Khowaja-Ateequzzaman and Garg (1995) that improved the original description by stating that the spines are formed from the periphragm. Despite occurring in the Middle Eocene, Trivalvadinium formosum Islam, 1983 also differs in possessing a rounded pentagonal ambitus, and tubular spines that are much less densely distributed. Remarks: We have opted to use the term periphragm for the outer wall layer of T. zakkii sp. nov. rather than ectophragm. It is clear that spines on the endocyst do not support the outer wall layer, particularly in the vicinity of the apical horn (Plate VI, figs. 1–6) or antapical horns (Plate IV, figs. 7–9; Plate V, figs. 4–6, Plate VI, figs. 3–5) and are obviously not an integral part of the wall design. Trithyrodinium zakkii sp. nov. is well known to biostratigraphers working o material from the North Sea and Norwegian–Greenland seas, and has been reported under the informal names Trithyrodinium “echinatum”, T. “hirsutum”, T. “spinosum”, or Trithyrodinium sp. (spines). 4. Biostratigraphy The stratigraphic distribution data of marker species from the 6406/ 3–6 well are illustrated on Fig. 2. The biostratigraphy is interpreted based on these data and not on additional information held by Equinor Energy AS. Chronostratigraphic intervals that contain the new species are discussed briefly below. The position of the Maastrichtian/Campanian boundary is picked between the Last Common Occurrence (LCO) of Heterosphaeridium bellii Radmacher et al., 2014 and the Last Occurrence (LO) of Palaeohystrichophora infusorioides Deflandre, 1935. We follow Radmacher et al. (2014) in taking high numbers of H. belli as a downhole indicator of early Maastrichtian–late Campanian interval, and Costa and Davey (1992) and Fensome et al. (2008) who use P. infusorioides as a Late Campanian, or intra-late Campanian marker, respectively. The position of the Campanian/Santonian boundary is taken at the highest occurrence of Surculosphaeridium longifurcatum that is used by Costa and Davey (1992) as a marker for the Late Santonian in the North Sea. It should be noted both Williams et al. (2004) and Fensome et al. (2008) place this event in the Early Campanian. Personal observations from European Chalk province sections from the Trunch borehole (Norfolk, UK) and the Santonian / Campanian boundary stratotype candidate at Bocieniec (southern Poland) also show that S. longifurcatum ranges well into the Campanian. No species events have been identified that adequately pick the top of the Coniacian. Ironically, this is traditionally done in the biostratigraphic industry on the highest abundant occurrence of Chatangiella islae sp. nov., and so the upper limit of the Coniacian is not placed to avoid a circular reasoning. The upper limit of the Turonian is, however, taken at the LO of Stephodinium coronatum

following Costa and Davey (1992). This interpreted chronostratigraphy for the 6406/3–6 well, is also consistent with the accepted age range of the lithostratigraphic units according to Dalland et al. (1988) for the Springar Formation (Campanian to Maastrichtian), Nise Formation (Santonian to Campanian), and Kvitnos Formation (Turonian to Santonian; see Fig. 2). The lowest stratigraphic occurrence of Chatangiella islae sp. nov. cannot be placed with certainty as caving of cuttings samples cannot be ruled out. The complete specimen of Trithyrodinium zakkii sp. nov. from a Heidrun well (Plate VI, figs. 1–6) occurs together with Heterosphaeridium bellii, H. difficile, Odontochitina diducta, Rhynchodiniopsis saliorum, Surculosphaeridium convocatum and S. longifurcatum, and below the LO of Alterbidinium ioannidesii and above the LO of Cassiculosphaeridia reticulata, LO of Palaeoglenodinium cretaceum and LO of Odontochitina porifera. Alterbidinium ioannidesii, Rhynchodiniopsis saliorum and Surculosphaeridium convocatum have a highest stratigraphic occurrence in the Early Campanian according to Louwye (1997), Pearce (2010) and Fensome et al. (2016) respectively, while Cassiculosphaeridia reticulata and Heterosphaeridium difficile are traditionally taken as downhole markers for the late Santonian (see Costa and Davey, 1992; Fensome et al., 2016). However, it should be noted that the LO of Cassiculosphaeridia reticulata has been recorded persistently into the Campanian of the southern North Sea Basin (Pearce, pers. obs.). Prince et al. (1999) record Odontochitina porifera from macrobiostratigraphically calibrated outcrop material of early late Santonian (U. socialis Zone) well into the early Campanian of southern England, and Siegl-Farkas (1997) records the species (as O. poriferastriatoperforata) from the latest Santonian well into the mid-Campanian of Hungary. Heterosphaeridium bellii was also rare in this sample, and on comparison with its distribution from the 6406/3–6 well, the base common occurrence occurs in the lowermost Campanian. Therefore, a general late Santonian/early Campanian age range for this sample is reasonable, but with a preferred age of late Santonian based on the overlapping range of Heterosphaeridium difficile and Odontochitina porifera, and rare numbers of H. belii. As caving cannot be ruled out, the complete specimen of T. zakkii sp. nov. from the Heidrun well cannot definitively be taken as in situ, and additional records are needed to confidently extend the range into late Santonian. Acknowledgements Our thanks to the Equinor Energy AS Heidrun asset and partners Petoro, ConocoPhillips and Eni for providing samples from the Heidrun Field and permission to illustrate a complete specimen of Trithyrodinium zakkii sp. nov. Johannes Schönenberger (Equinor Energy AS) kindly provided information on the Heidrun fields, but which could unfortunately not be published. Our sincere thanks to Dr. Paul Dodsworth and Dr. Ian Harding for their comments that improved the original draft. GeoStrat Limited generated the original biostratigraphic data for the 6406/3-6 well. References Alberti, G., 1959. Zur Kenntnis der Gattung Deflandrea Eisenack (Dinoflag.) in der Kreide und im Alttertiär Nord- und Mitteldeutschlands. Mitteilungen aus dem Geologischen Staatsinstitut in Hamburg 28, 93–105. Bujak, J.P., Davies, E.H., 1983. Modern and fossil Peridiniineae. American Association of Stratigraphic Palynologists, Contributions Series, 13, p. 203. Bujak, J.P., Downie, C., Eaton, G.L., Williams, G.L., 1980. Dinoflagellate cysts and acritarchs from the Eocene of southern England. Spec. Pap. Palaeontol. 24, 100. Bütschli, O., 1885. Erster Band. Protozoa. Dr. H.G. Bronn's Klassen und Ordnungen des Thier-Reichs, wissenschaftlich dargestellt in Wort und Bild. C.F. Winter'sche Verlagsbuchhandlung, Leipzig and Heidelberg, Germany, pp. 865–1088. Clarke, R.F.A., Verdier, J.-P., 1967. An investigation of microplankton assemblages from the Chalk of the Isle of Wight, England. Verhandelingen der Koninklijke Nederlandse Akademie van Wetenschappen, Afdeeling Natuurkunde, Eerste Reeks 24, 1–96. Costa, L.I., Davey, R.J., 1992. Dinoflagellate cysts of the Cretaceous System. In: Powell, A.J. (Ed.), A Stratigraphic Index of Dinoflagellate Cysts. Special Publication of the British Micropalaeontological Society, London, pp. 99–131. Dalland, A., Worsley, D., Ofstad, K., 1988. A lithostratigraphic scheme for the Mesozoic and Cenozoic succession offshore mid- and northern Norway. NPD Bulletin 4 (65 pp.).

M.A. Pearce et al. / Review of Palaeobotany and Palynology 271 (2019) 104080 Davey, R.J., 1969. Some dinoflagellate cysts from the Upper cretaceous of northern Natal, South Africa. Palaeontol. Afr. 12, 1–23. Deflandre, G., 1935. Considérations biologiques sur les microorganisms d'origine planctonique conservés dans les silex de la craie. Bulletin biologique de la France et de la Belgique 69, 213–244. Drugg, W.S., 1967. Palynology of the Upper Moreno Formation (Late Cretaceous–Paleocene) Escarpado Canyon, California. Palaeontogr. Abt. B 120, 1–71. Ehrenberg, C.G., 1832. Über die Entwickelung und Lebensdauer der Infusionsthiere; nebst ferneren Beiträgen zu einer Vergleichung ihrer organischen Systeme. Abhandlungen der Königlichen Akademie der Wissenschaften zu Berlin, aus dem Jahre 1831, Physikalische Klasse 1–154. Evitt, W.R., 1985. Sporopollenin Dinoflagellate Cysts: Their Morphology and Interpretation. American Association of Stratigraphic Palynologists Foundation, Dallas, p. 333. Fensome, R.A., Taylor, F.J.R., Norris, G., Sarjeant, W.A.S., Wharton, D.I., Williams, G.L., 1993. A Classification of Fossil and Living Dinoflagellates. Micropaleontology Press Special Paper, 7 p. 351. Fensome, R.A., Crux, J.A., Gard, G., MacRae, R.A., Williams, G.L., Thomas, F.C., Fiorini, F., Wach, G., 2008. The last 100 million years on the Scotian Margin, offshore eastern Canada: an event-stratigraphic scheme emphasizing biostratigraphic data. Atl. Geol. 44, 93–126. Fensome, R.A., Williams, G.L., MacRae, R.A., 2009. Late Cretaceous and Cenozoic fossil dinoflagellates and other palynomorphs from the Scotian Margin, offshore eastern Canada. J. Syst. Palaeontol. 7, 1–79. Fensome, R.A., Nøhr-Hansen, H., Williams, G.L., 2016. Cretaceous and Cenozoic dinoflagellate cysts and other palynomorphs from the western and eastern margins of the Labrador-Baffin Seaway. Geol. Surv. Denmark and Greenland Bull. 36, 146. Haeckel, E., 1894. Systematische Phylogenie. Entwurf eines natürlichen Systems der Organismen auf Grund ihrer Stammegeschichte, I. Systematische Phylogenie der Protisten und Pflanzen, Berlin, Reimer, p. XV+400. Harker, S.D., Sarjeant, W.A.S., 1991. Late Cretaceous (Campanian) organic-walled microplankton from the interior plains of Canada, Wyoming and Texas: validation of new taxa. Neues Jb. Geol. Paläontol. Monat. 12, 707–710. Harker, S.D., Sarjeant, W.A.S., Caldwell, W.G.E., 1990. Late Cretaceous (Campanian) organic-walled microplankton from the interior plains of Canada, Wyoming and Texas: biostratigraphy, palaeontology and palaeoenvironmental interpretation. Palaeontogr. Abt. B 219, 243. Islam, M.A., 1983. Dinoflagellate cyst taxonomy and biostratigraphy of the Eocene Bracklesham Group in southern England. Micropaleontology 29, 328–353. Khowaja-Ateequzzaman, Garg, R., 1995. Jainiella—a new dinoflagellate cyst genus from the Upper Cretaceous of Cauvery Basin, India. The Palaeobotanist 42, 245–248. Lentin, J.K., Vozzhennikova, T.F., 1990. Fossil dinoflagellates from the Jurassic, Cretaceous and Paleogene deposits of the USSR — a re-study. American Association of Stratigraphic Palynologists, Contributions Series, 23, p. 221. Lentin, J.K., Williams, G.L., 1975. A monograph of fossil peridinioid dinoflagellate cysts. Bedford Institute of Oceanography, Report Series, BI-R-75-16, p. 237. Louwye, S., 1997. New dinoflagellate cyst species from the Upper cretaceous subsurface deposits of western Belgium. Ann. Soc. Geol. Belg. 118, 147–159. Manum, S.B., 1963. Some new species of Deflandrea and their probable affinity with Peridinium. Norsk Polarinstitutt, Årbok 1962, 55–67. Manum, S.B., Cookson, I.C., 1964. Cretaceous microplankton in a sample from Graham Island, arctic Canada, collected during the second "Fram" expedition (1898-1902). With notes on microplankton from the Hassel Formation, Ellef Ringnes Island. Norske

13

Videnskaps-Akademi i Oslo, I. Matematisk-Naturvidenskapelig Klasse, Skrifter, Ny Serie 17, 1–36. Marheinecke, U., 1992. Monographie der Dinozysten, Acritarcha und Chlorophyta des Maastrichtium von Hemmoor (Niedersachsen). Palaeontogr. Abt. B 227, 1–173. Marshall, N.G., 1988. A Santonian dinoflagellate assemblage from the Gippsland Basin, southeastern Australia. In: Jell, P.A., Playford, G. (Eds.), Palynological and Palaeobotanical Studies in Honour of Basil E. Balme. Memoir of the Association of Australasian Palaeontologists. 5, pp. 195–215. McIntyre, D.J., 1975. Morphologic changes in Deflandrea from a Campanian section, District of Mackenzie, N.W.T., Canada. Geosci. Man 11, 61–76. Pascher, A., 1914. Über Flagellaten und Algen. Deutsche Botanische Gesellschaft, Berichte 32, 136–160. Pearce, M.A., 2010. New organic-walled dinoflagellate cysts from the Cenomanian to Maastrichtian of the Trunch borehole, UK. J. Micropalaeontol. 29, 51–72. Prince, I.M., Jarvis, I., Tocher, B.A., 1999. High-resolution dinoflagellate cyst biostratigraphy of the Santonian-basal Campanian (Upper Cretaceous): new data from Whitecliff, Isle of Wight, England. Rev. Palaeobot. Palynol. 105, 143–169. Radmacher, W., Mangerud, G., Tyszka, J., 2015. Dinoflagellate cyst biostratigraphy of Upper Cretaceous strata from two wells in the Norwegian Sea. Rev. Palaeobot. Palynol. 216, 18–32. Radmacher, W., Tyszka, J., Mangerud, G., 2014. Distribution and biostratigraphical significance of Heterosphaeridium bellii sp. nov. and other Late Cretaceous dinoflagellate cysts from the southwestern Barents Sea. Rev. Palaeobot. Palynol. 201, 29–40. Schiøler, P., 1993. New species of dinoflagellate cysts from Maastrichtian–Danian chalks of the Danish North Sea. J. Micropalaeontol. 12, 99–112. Siegl-Farkas, A., 1997. Dinoflagellate stratigraphy of the Senonian formations of the Transdanubian Range. Acta Geol. Hung. 41, 73–100. Stover, L.E., Evitt, W.R., 1978. Analyses of pre-Pleistocene organic-walled dinoflagellates. Stanford Univ. Publ., Geol. Sci. 15, 300. Stover, L.E., Williams, G.L., 1987. Analyses of Mesozoic and Cenozoic organic-walled dinoflagellates 1977–1985. American Association of Stratigraphic Palynologists, Contributions Series, 18, p. 243. Vozzhennikova, T.F., 1967. Iskopaemye peridinei Yurskikh, Melovykh i Paleogenovykh otlozheniy SSSR. Izdatelstvo Nauka, Moscow, U.S.S.R., p. 347. Williams, G.L., Brinkhuis, H., Pearce, M.A., Fensome, R.A., Weegink, J.W., 2004. 5. Southern Ocean and Global Dinoflagellate Cyst Events Compared: Index Events for the Late Cretaceous–Neogene. Proceedings of the Ocean Drilling Program, Scientific Results. 189, pp. 1–98. Williams, G.L., Damassa, S.P., Fensome, R.A., Guerstein, G.R., 2015. Wetzeliella and its allies — the 'hole' story; a taxonomic revision of the Paleogene subfamily Wetzelielloideae. Palynology 39, 289–344. Williams, G.L., Fensome, R.A., MacRae, R.A., 2017a. The Lentin and Williams Index of Fossil Dinoflagellates. 2017 edition. vol. 48. American Association of Stratigraphic Palynologists, p. 1097. Williams, G.L., Fensome, R.A., MacRae, R.A., 2017b. DINOFLAJ3. American Association of Stratigraphic Palynologists, Data Series No. 2. Willumsen, P.S., Vajda, V., 2010. A new early Paleocene dinoflagellate cyst species, Trithyrodinium partridgei: its biostratigraphic significance and paleoecology. Alcheringa 34, 523–538.