179

On Arenomeandrospira gen.nov. (Foraminiferida, Ammodiscidae), and its association with Natural Gas Seepage

R. W. JONESI and A.A.H. WONDERS2 1. BP Exploration Operating Company Ltd., Chertsey Road, Sunbury-on-Thames, Middlesex, TW16 7LN, UK

2. The Bridge, 14 Lakeland Drive, Frimley, Surrey, GU16 5LD, UK.

ABSTRACT The new ammodiscid genus Arenomeandrospira is erected. The genus is diagnosed by its modified streptospiral or "meandrospiral" coiling. The only recorded occurrences to date are from the Holocene of Scandinavia, Trinidad and Croatia, and the Miocene of Vietnam and Borneo. In certain cases, the occurrences may be associated with natural gas seepage.

INTRODUCTION In 1947, in his now classic monograph of the Holocene foraminifera of the Gullmar Fjord and Skagerak, Hans Hoglund described a new ammodis­cid species which he called Glomospira glomernta n.sp .. Hoglund distinguished it on the basis of the arrangement of the post-prolocular chamber, which he described as "wound up in sharp, meandering turns around the initial part".

We believe that this species is so distinct in terms of this modified streptospiral or "meandrospiral" coiling (reminiscent of the "thal­mannamminiform" coiling of Platon (1997)) that it merits a genus to itself. We formally describe Arenomeandrospira gen.nov. below, with A. glom­erata (Hoglund, 1947) [Glomospira glomerata Hoglund, 1947) as type species by monotypy. We supplement the description with illustrations of the holotype and para types from the Holocene of the Gullmar Fjord and Skagerak (deposited by Hoglund in the Department of Invertebrate Zoology of the Swedish Museum of Natural History (Natur­historika Riksmusset), Stockholm, Sweden) and of hypotypes from the Miocene of Vietnam (deposited by us in the Department of Palaeontology of the Natural History Museum, London).

We also include data on its ecological and stratigraphic distribution.

SYSTEMATIC MICROPALAEONTOLOGY

Order ASTRORHIZIDA Brady, 1881 Superfamily AMMODISCACEA Reuss, 1862 Family AMMODISCIDAE Reuss, 1862 Genus Arenomeandrospira gen. nov.

Type species. Arenomeandrospira glomerata (Hoglund, 1947) [Glomospira glomerata Hoglund, 1947); OD(OM). Scandinavia, Trinidad, Venezuela, Croatia, Vietnam, Borneo; Miocene-Holocene. Derivation of Name. Areno(sus)- (L.), sandy, with reference to the wall structure + Meandrospira, a porcelaneous foraminiferal genus. Diagnosis. An ammodiscid genus diagnosed by modi­fied streptospiral or "meandrospiral" coiling (see below). Description. As type species (see below) Ecological Distribution. As type species (see below). Stratigraphic Distribution. As type species (see below).

Arenomeandrospira glomerata (Hoglund, 1947)

Figure 1, Nos 1-4 Plate 1, Figs 1a-d, 2a-b.

Glomospira glomerata n.sp. Hoglund, 1947, pp. 130-131, pI. 3, figs 8-10 (reproduced herein as text-figs. 1-3), text-fig. 104 (reproduced herein as text-fig. 4).

Glomospira glomerata Hoglund.- Todd & Bronnimann, 1957, p. 22, pI. 1, fig. 2l.

Glomospira glomerata Hoglund.- Daniels, 1970, p. 67, pI. 1, fig. 6, text-fig. 42.

Glomospira glomerata Hoglund.- Alve & Nagy, 1986, p. 282, pI. 1, fig. 14. .

Gfomosplra glomerata (Hoglund) (sic).- van Borren, Koopman & Schreurs, in Sandal, 1996, p. 90, fig. 4.4m.

See also Simmons et al. (1999) and Bidgood et al. (this volume). Material. Several hundred specimens. Repository. The syntypes (holotype and paratypes) of Hoglund's (1947) Glomospira glomerata n.sp. (Figure 1, nos. 1-4; Plate 1, Figs la-d) from the Holocene of Scandinavia are housed in the Swedish

In: Hart, M.B., Kaminski, M.A., & Smart, C.W. (eds) 2000. Proceedings of the Fifth International Workshop on Agglutinated Foraminifera. Grzybowski Foundation Special Publication, 7,179-184.

R.W. Jones & A.A.H. Wonders

Figure 1. Enlarged reproductions of original line drawings of Hoglund (1947). la-c. A "regularly built" syntype (para type) from Bjorkholmen in three different aspects. x116. 2. Another syntype (para type) from Bjorkholmen x116. 3a-b. Details of wall of syntype (para type) from Bjorkholmen. a = tangential section; 0 = transverse section. x1896. 4. Section through central part of proloculus of syntype (para type) from Bjorkholmen x403.

Museum of Natural History (Naturhistorika Riksmusset) in Stockholm, Sweden. The holotype (Plate I, Fig. la-d) is housed in inside a cottonwool­stoppered alcohol-filled glass phial labelled "Glomospira glomerata n.sp." which in turn is inside a larger glass phial labelled "Glomospira glomerata n.sp.: Stat. Bjorkholmen, 16/8/1927: c. 30 m: Holotyp" and signed Hans Hoglund. The holo­type no. is 2054.

Figured and other representative hypo types from the Miocene of Vietnam (Plate I, Fig. 2a-b) are housed in the Department of Palaeontology of the Natural History Museum, London. Description (syntypes). Test free, spherical, consist­ing of a spherical proloculus and an elongate tubular post-prolocular second chamber; chamber arrange­ment modified streptospiral or "meandrospiral" (second chamber formed into a line of tight folds with subparallel axes, each fold approximately four times as high as wide, line of folds wound streptospirally around proloculus, typically four to six folds per whorl, only those of final whorl visible externally); wall finely arenaceous, cemented, inner and outer surfaces smooth; aperture terminal, at open end of tube. Dimension. Test diameter 0.2-0.3 mm; proloculus diameter 23-30 Jlm; coil diameter (proximal) 8-10 Jlm to 0.08-0.10 mm (distal); wall thickness 10 Jlm (Hoglund,1947).

Variability. Hoglund (1947) noted some variability in the coiling of this species, stating that not all specimens is his collections were as regular as those he illustrated. A similar range of variability is evident among studied hypotypes from the Miocene of Vietnam, which also exhibit varying degrees of compression due to burial. Type Locality. Bjorkholmen, Gullmar Fjord, Scandinavia. Type Level. Holocene. Comment. Glomospira glomerata Hoglund, 1947 is a junior homonym of G. glomerata (Grzybowski, 1898) auctt. [Ammodiscus glomeratus Grzybowski, 1898]. However, it does not require a replacement name, nor has one been proposed, as it is clearly not congeneric with Grzybowski's species, and in any case the homonymy is only secondary (subjective). Ecological and Palaeoecological Distribution. Hoglund (1947) recorded Arenomeandrospira glom­erata [as Glomospira glomerata n.sp.] as rare (up to 12 specimens per sample) in Cores G14a, G26, G27, G54, G57, G58, G65, G71, G74 and G7S from the Gullmar Fjord (water depths 24-67 m) and Core K30 from the Kattegat (48 m), and abundant (>200 spec­imens) in a dredge from Bjrokholmen (the holotype locality) in the Gullmar Fjord (30 m). Station loca­tions are shown on Figures 2-3. Location, depth and substrate data from the stations where A. glomerata was recorded are shown on Table 1. The depth distribution of the species in the Gullmar Fjord is

On Arenomeandrospira gen.nov. and its association with natural gas 181

+ Dynan

'lPtJ' J ...I!S. • a(\ ,- ~ . .n; ;r , }!i t!>. ~ q ';, .' • ..lJ •

~;: ,

o

Figure 2. The Gullmar Fjord (from Hoglund, 1947). Arenomeandrospira glomerata (Hoglund, 1947) was recorded by Hoglund (as Glomospira glomerata n. sp,) in cores from Stations G14a, G26, G27, G54, G57, G58, G65. G71, G74 and G75 (water depths 24-67 m) and in a dredge sample adjacent to station G26 (30 m),

7" 1(1' II'

lagand

Sf!' · - • Quantitative (core sampler) stations . ' .' 5f!'

+ Qualitative stations

~ Shallow Gas

o Pockmarks

/" Contours (metres)

50100 ,

511' 511'

7" 1(1'

Figure 3. The Sk~gerak and Kattegat (from Hoglund, 1947 (shallow gas and pockmark occurrences from Hovland, 1992c)). Arenomeandrosplra glomerata (Hoglund, 1947) was recorded by Hoglund (as Glomospira glomerata n.sp.) in a core from station K30 in the Kattegat (48 m).

182

Om

25m

50m

75m

100m

Figure 4. Depth Distribution of Arenomeandrospira glom­erata (Hoglund, 1947) in the Gullmar Fjord (modified after Hoglund, 1947). Hoglund referred to this type of distribution as "stenobathic middle water".

shown on Figure 4. Alve & Nagy (1986) later recorded A. glomerata [as Glomospira glomerata Hoglund, 1947] at 11 stations in the Sandebukta (a branch of the Oslo Fjord) at depths ranging from 16 to 66m.

Todd & Bronnimann (1957), Bermudez (1966) and Daniels (1970) recorded A. glomerata [as Glomospira glomerata Hoglund, 1947] between 2-18 fathoms (4-36 m) in the Eastern Gulf of Paria, off­shore Trinidad, off the central and eastern coasts of Venezuela, and in a depth of 32 m in the Limski Channel in the Northern Adriatic, offshore Croatia respectively. Incidentally, one of us (RWJ) has also come across uncorroborated records (in proprietary reports) of "GIomospira glomerata" in the Mio­Pliocene of the Gulf of Paria.

We have recently recorded locally abundant (up to 50 specimens per sample) occurrences in the Miocene of a recent BP Exploration well drilled in the Nam Con Son Basin, offshore Vietnam, the pre­cise details of which cannot be disclosed for reasons of commercial sensitivity.

Van Borren et al., in Sandal (1996), Simmons et al. (1999), and Bidgood et al. (this volume) have recently recorded occurrences in interpreted shallow and deep marine environments in the Miocene of Northwest Borneo.

In the case of the Miocene of the well in Vietnam, A. glomerata occurs in the drowning (seal) sequence immediately overlying the shallow marine carbon-

R.W. Jones & A.A.H. Wonders

ate reservoir target, and forms part of an assemblage interpreted as associated with natural gas seepage (on the basis of analogy with work by Jones (1992, 1993, 1996) and Coles et al. (1996)). The gas seepage was evidently taking place as the seal sequence was being deposited and the trap formed.

It is conceivable that the occurrences in the Kattegat and Skagerak are also associated with gas seepage. These are areas of known shallow gas occurrence characterised by periodic explosive release and the development of "pockmarks" (e.g., Hovland, 1991, 1992a-c, 1993; Laier, 1993; Figure 3). Methane-derived carbonate forms "pseudoreefs" that favour the epifauna at the expense of the infauna (Dando, Jensen et al., 1994). Some macro­faunal species host symbiotic methanotrophic bacteria (Dando, Bussmann et aI., 1994). Stratigraphic Distribution: Miocene-Holocene.

ACKNOWLEDGEMENTS Karine Sindemark of the Department of Invertebrate Zoology of the Swedish Museum of Natural History (Naturhistorika Riksmusset), Stockholm, Sweden, is thanked for arranging the loan of the holotype of Glomospira glomerata Hoglund, 1947, John Whittaker of the Department of Palaeontology of the Natural History Museum, London, for assistance with photography and plate production. BP Exploration provided word-process­ing and drafting facilities, and are also thanked for permission to publish.

REFERENCES Alve, E. & Nagy, J. 1986. Estuarine foraminiferal distribu­

tion in Sandebukta, a branch of the Oslo Fjord. Journal of Foraminiferal Research, 16(4), 261-284.

Bermudez, P.J. 1966. Consideraciones sobre los Sedimentos del Mioceno Medio al Reciente de las Costas Central y Oriental de Venezuela. Primera Parte. Boletin de Geologia, 7(14), 333-412.

Bidgood, M.D., Simmons, M.D. & Thomas, e.G.e., this vol­ume. Agglutinated foraminifera from Miocene sediments of northwest Borneo.

Coles, G.P., Ainsworth, N.R, Whatley, Re. & Jones, RW. 1996. Foraminifera and Ostracoda from Quaternary car­bonate mounds associated with gas seepage in the Porcupine Basin, offshore Western Irelancf. Revista Espanola de Micropaleontologia, 23(2), 113-151.

Dando, P.R., Bussmann, I., Niven, S.J., O'Hara, S.e.M., Schmaljohann, R & Taylor, L.J. 1994. A methane seep area in the Skagerrak, the habitat of the pogonophore Siboglinum poseidoni and the bivalve mollusc Thyasira sarsl. Marine Ecology Progress Series, 107, 157-167.

Dando, P.R, Jensen, P., O'Hara, S.e.M., Niven, S.J., Schmaljohann, R, Schuster, U. & Taylor, L.J. 1994. The effects of methane seepage at an intertidal/shallow sub­tidal site on the shore of the Kattegat, Vendsyssel, Denmark. Bulletin of the Geological Society of Denmllrk, 41,65-79.

Daniels, e.H. von, 1970. Quantitative okologische Analyse der zeitlichen und raumlichen Verteilung Rezenter Foraminiferen im Limski Kanal bei Rovinj (Nordliche Adria). Giittinger Arbeiten zur Geologie und PalCiontologie, 8,1-109.

Hoglund, H. 1947. Foraminifera in the Gullmar Fjord and Skagerak. Zoologiska Bidrag fran Uppsala, 26, 328 pp + 31 pIs.

On Arenomeandrospira gen.nov. and its association with natural gas 183

Hovland, M. 1991. Large pockmarks, gas-charged sediments and possible clay diapirs in the Skagerrak. Marine and Petroleum Geology, 8, 311-316.

Hovland, M. 1992a. The effects of shallow gas in the Skagerrak surficial sediments. Geologiska Foreningens I Stockholm Forlzandlingar, 114, 242-243.

Hovland, M. 1992b. Hydrocarbon seeps in northern marine waters - their occurrence and effects. Palaios, 7, 376-382.

Hovland, M. 1992c. Pockmarks and gas-charged sediments in the eastern Skagerrak. Contlllental Shelf Research, 12(10), 1111-1119.

Hovland, M. 1993. Submarine gas seerage in the North Sea and adjacent areas. In: Parker, .R (ed.): Petroleum Geology of North-West Europe: Proceedings of tlze FOllrth Conference. The Geological Society, London, 1333-1338.

Jones, RW. 1992. Benthonic foraminifera associated with natural petroleum seeps. European Journal of Protistology, 28(3), 344 (abstract).

Jones, RW. 1993. Preliminary observations on benthonic foraminifera associated with a biogenic gas seep in the North Sea. In: Jenkins, D.G. (ed.), Applied Micropalaeontology. Kluwer Academic Publishers, Dordrecht, 69-91.

Jones, RW. 1996. Micropalaeontology in Petrolelllll Exploration. Oxford University Press, xv + 432 pp.

Laier, T. 1992. Shallow gas in northern Kattegat and southern Skagerrak. Geologiska Foreningens I Stockhol1ll Forhandlingar, 114, 244-245.

Platon, E. 1997. Coiling modes in the Family Plectorecur­voididae (Foraminifera). Annales Societatis Geologorum Poloniae, 67, 339-343.

Sandal, S.T. (ed.), 1996. The Geology and Hydrocarbon Resources of Negara Brllnei Darussala1ll. Sybas (Bandar Seri Begawan), Brunei Darussalam.

Simmons, M.D., Bidgood, MD., Brenac, P., Crevello, P.D., Lambiase, J.J. & Morley, c.K. 1999. Microfossil assem­blages as proxies for precise palaeoenvironmental deter­mination - an example from Miocene sediments of north­west Borneo. In: Jones, RW. & Simmons, M.D. (eds), Biostratigraphy in Production Geology. Geological Society (London) Special Publication, 152, 219-241.

Todd, R & Bronnimann, P. 1957. Recent Foraminifera and Thecamoebina from the Eastern Glllf of Paria, trinidad. Cushman Foundation for Foraminiferal Research Special Publication, 3.

------~~~~-------

Table 1. Location, depth and substrate data on stations where Arenomeandrospira glomerata (Hoglund, 1947) was found (compiled from Hoglund, 1947).

Station General Specific Location

Depth Substrate Location Latitude Longitude

G14a Gullmar Fjord 58° 16.80' N 11·? 28.50' E 32m Light greenish grey sandy clay

G26 Gullmar Fjord 58° 23.85' N 11° 38.90' E 24m YellowiSh brown intensely sandy clay

G27 Gullmar Fjord 58° 24.20' N 11° 36.10' E 33m Yellowish grey clay

G54 Gullmar Fjord 58° 19.45' N 11° 32.40' E 67m Yellowish grey sandy clay

G57 Gullmar Fjord 58° 20.40' N 11° 33.10' E 34m Yellowish grey intensely sandy clay

G58 Gullmar Fjord 58° 20.85' N 11° 35.35' E 45m Yellowish grey sandy clay

G65 Gullmar Fjord 58° 21.85' N 11° 34.50' E 30m Yellowish grey intensely sandy clay

G71 Gullmar Fjord 58° 24.15' N 11 ° 57.80' E 48m Yellowish grey sandy clay

G74 Gullmar Fjord 58° 23.45' N 11° 34.55' E 32m Brownish grey clay

K30 Kattegat 57° 25.00' N 11° 32.00' E 48m -

Bj6rkholmen Gullmar Fjord 30m Intensely sandy clay (dredge) (close to G26) - -

R.W.JolIa '" A.A.H. Wond~",

rllt~ 1. h·d. F.nvironmmtal chilmbtor SEM m!crophotogr~ph' of v.r;ou~ aspects of the holotype, Holocene. Bjorkholmm. 2.·b. SEM microphotogr~phs of vari"", upecto of. hypOlype. Miocene. Vietnom.