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Journal ofForaminifera1Research, v. 16, no. 2, p. 135-140, pl. 1, April 1986

DISTRIBUTION OF FRONDICULARIA RAKA UROANA (FINLAY) IN THE SOUTHERN HIGH LATITUDES BRIANT. HUBER AND PETER N. WEBB Institute of Polar Studies and Department of Geology and Mineralogy, The Ohio State University, Columbus, OH 43210 ABSTRACT

particularly the Globotruncanidae, were restricted to tropical low-latitude and temperate mid-latitude seas during the Cretaceous. They placed these regions in the Tethyan and Transitional provinces, respectively. They also defined a microfaunal Austral Province on the absence ofwarm-water taxa within Late Cretaceous marine sediments of the higher latitudes. However, neither Webb, Scheibnerovh nor Sliter recognized distinctive foraminiferal assemblages, families or genera restricted only to the Austral Province. In this study we discuss the distribution of one unusual foraminiferal species of Frondicularia, which appears to be restricted to the southern high latitudes, and we explore the implication of this species for the Late Cretaceous paleogeography of the Antarctic region.

The palmate nodosariid Frondicularia rakauroana (Finlay) is reported from upper Campanian through lower Maestrichtian sediments of the Lopez de Bertodano Formation on Seymour Island, within the James Ross Island basin (Antarctic Peninsula). Hitherto, distribution of this distinctive taxon has been confined to the upper Haumurian Stage (Maestrichtian) of New Zealand and the Lord Howe Rise (DSDP Site 208). Frondicularia rakauroana may have had a diachronous distribution, being first recognized in upper Campanian strata on Seymour Island and occurring in younger sediments on Lord Howe Rise and New Zealand. Restriction of this species to the southern high latitudes provides support for the presence of a southern marine faunal realm or province during the Late Cretaceous. Furthermore, the restriction of F. rakauroana to the three localities cited points to some form of marine communication around the southern Pacific margin of Antarctica or through trans-Antarctic passages.

DEPOSITIONAL ENVIRONMENT The Lopez de Bertodano Formation is a mid-to outer-shelf deposit (Macellari, 1984a, b; Huber, 1984). Quiet-water conditions persisted throughout its deposition, as shown by the high mud (silt and clay) content, the occurrence of predominantly articulated molluscs, the preservation of macro-invertebrates in life position (Macellari, 1984a)and the absence of traction current structures. The presence of large fossil marine reptiles and abundant fossil wood throughout the Cretaceous-Tertiary boundary sequence indicates proximity to a coast (Gasparini and Del Valle, in press). The presence of diverse and abundant macro-invertebrates, numerous nodosariids, and diverse calcareous and siliceous microplankton throughout this formation indicates normal marine conditions, which probably did not exceed depths greater than outer noritic. The entire Cretaceous marine sequence on Seymour Island was probably deposited rapidly. The stratigraphic thickness (> 1,100 m) and time represented (< 10 my) indicate a sedimentation rate of over 100 m/my. The abundance of clay and fine silt throughout the Lopez de Bertodano Formation indicates that turbid conditions persisted during deposition of most of this sequence. The source of this fine-grained material may have been an estuary or river delta (Macellari, 1984a).

INTRODUCTION Recent work by Huber and others (1983) and Huber (1984) has revealed the presence of well-preserved and diverse foraminiferal assemblages in fossiliferous outcrops of the Lopez de Bertodano Formation on Seymour Island (latitude 64"15'S, longitude 56"45'W, Fig. 1). This eastward dipping homoclinal sequence consists of more than 1,100 m of predominantly friable sandy siltstone with occasional lithified silty sandstone and concretionary horizons; it ranges in age from the late Campanian through Maestrichtian. The continuous exposure, abundance of well-preserved macro-invertebrates (Macellari, 1984a, b) and high latitude position of this unit, provide a unique opportunity for detailed study of Late Cretaceous, southern, high-latitude faunas. Webb (in Hornibrook, 1969) favored the existence of a temperate climatic zone (Austral macrofossil realm of Fleming, 1962;southern extra-Tethyan area of Webb, 1973a, b) for the southern high-latitude Cretaceous, at least in the region of New Zealand. He noted the absence of such characteristically Tethyan genera as Schackoina, Clavihedbergella, Ticinella, Rotalipora, Praeglobotruncana, Planoglobulina, Pseudotextularia and common Globotruncana. In contrast, planktonic taxa such as Hedbergella, Globigerinelloides,Rugoglobigerina, Abathomphalus, Rugotruncana, Heterohelix, Guembelitria and Gublerina are quite common. Scheibnerovh (197 1, 1973) and Sliter (1 976) also noted that certain planktonic foraminiferal species,

FORAMINIFERA OF THE LOPEZ DE BERTODANO FORMATION

An assemblage of 73 genera and 156 species of foraminifera, including 37 agglutinated, 101 calcareous benthic and 18 planktonic species, has been documented from the Lopez de Bertodano Formation 135

136

HUBER AND WEBB

TABLE 1. Selected measurements of five specimens. PI. 1, PI. I , PI. I , Fig. 1 Fig. 2 Fig. 3 Holotype Paratype OSU OSU OSU TF TF 38551 38552 38553 1103/1 110312 S.I.-IOl S.1.-386 S.1.-429

Length (mm) Breadth (mm) Chamberthickness (mm) Prolocular thickness (mm) Ratio L/B OSU

=

, "

3.15 1.65 0.25 0.30 1.91

1.12 0.60 0.20 0.30 1.87

1.15 1.09 1.34 0.71 0.64 0.76 0.19 0.16 0.22 0.30 0.30 0.28 1.62 1.70 1.76

Ohio State University, S.I. = Seymour Island.

(Finlay). The palmate genera Neoflabellina, Palmula, Falsopalmula and Citharinella are conspicuously absent from these strata. SYSTEMATIC PALEONTOLOGY FIGURE1. Location map and geology of the western portion of Seymour Island. Sample localities shown in the Cretaceous sequence are referred to in the text.

(Huber, 1984). This assemblage has yielded a mixture of cosmopolitan, provincial and locally endemic taxa. Among the planktonic species, closest affinity is with coeval Falkland Plateau assemblages reported by Sliter (1976) and Krasheninnikov and Basov (1983). The benthic assemblages bear closest resemblance to New Zealand Haumurian (late Campanian-Maestrichtian) assemblagesreportedby Webb(1966a, b, 1971, 1973a, b), although only 27% of the benthic species are common to both areas. Fourteen percent of the total Seymour Island foraminiferal assemblage are considered to be new species. The Lopez de Bertodano Formation on Seymour Island has been assigned a late CampanianMaestrichtian age based on the presence of several diagnostic foraminiferal and calcareous nannoplankton taxa (Huber and others, 1983). The lowermost interval, which includes the oldest stratigraphic occurrence of Frondicularia rakauroana (sample 386; Fig. 1). is assigned a late Campanian-earliest Maestrichtian age based on the distribution of the coccolith Nephrolithus corystus Wind and the foraminifera Hedbergella monmouthensis (Olsson), Rugoglobigerinapilula (Belford and Rugoglobigerina rugosa (Plummer). Samples 101 and 429, which also yield specimens of F. rakauroana, are assigned a Maestrichtian age based on the co-occurrence of the coccolith Nephrolithus frequens (G6rka) and the foraminifera Rugoglobigerina rotundata Bronnimann and Globotruncanella havanensis (Voorwijk). The family Nodosariidae (classification of Loeblich and Tappan, 1964) is represented in the Lopez de Bertodano Formation by cosmopolitan species of Dentalina, Nodosaria, Lenticulina and Lagena. Palmate nodosariids are quite rare in this formation and include several specimens of Citharina plumoides (Plummer), Citharina sp. and three specimens (in three separate samples) of the distinctive Frondicularia rakauroana

Superfamily NODOSARIACEA Ehrenberg, 1838 Family NODOSARIIDAE Ehrenberg, 1838 Frondicularia De France, in d'orbigny, 1826 Frondicularia rakauroana (Finlay) P1. 1, Figs. 1-9 Palmula rakauroana FINLAY, 1939, p. 314, pl. 26, figs. 51-52. FINLAY and MARWICK, 1940, p. 104. FINLAY, 1948, in Macpherson, p. 294. Neoflabellina rakauroana (Finlay).-HORNIBROOK, 1968,p. 41, 45, fig. 4. Frondicularia rakauroana (Finlay).- WEBB, 1966a,p. 203,pl. 14, figs. 6, 11. WEBB, 1966b,p. 14. WEBB, 1972,p. 94-100, pl. 1, figs. 1-27; pl. 2, figs. 1-5. WEBB, 1978, in Suggate, p. 365, figs. 6, 8,no. 19. HUBER, 1984,p. 140-141, pl. 5, figs. 3, 4.

Description. Test palmate, large proloculus bearing basal spine on well-preserved specimens; apertural end tapered to a point; test usually flat but may be twisted or curved about the long axis; generally exhibits bilateral symmetry; peripheral margin surrounded by distinct paired keels, which extend from near basal spine to aperture; keels separated by shallow groove, sometimes bearing faint longitudinal costellae (Pl. 1, Figs. 5 , 6, 9); chambers increase gradually in size as added, equitant in shape; 3-4 chambers follow proloculus; sutures slightly depressed. Aperture terminal, produced on short neck and square in cross section (Pl. 1, Fig. 4). Wall calcareous, surface smooth (Pl. 1, Fig. 8); ornamented by 5-6 ribs extending completely or part way up the longitudinal axis of the proloculus, on each side of the paired keels (Pl. 1, Figs. 1-3); these ribs and several later pairs cross the equitant chambers, bending as much as 50" away from the long axis of the test and becoming nearly perpendicular to the equitant sutures; single discontinuous rib extends up the center of the equitant chambers; faint reticulate pattern may occur among ribs on third or fourth equitant chamber (Pl. 1, Figs. 2, 3); ornament pattern may differ somewhat on either side of test. Discussion. Three specimens collected from Seymour Island are nearly identical in size and morphology (Pl. 1, Figs. 1-3, 5-7). They exhibit closest similarity (Fig. 2) to Finlay's (1 939, pl. 26, fig. 52) paratype (TF 1 103/2), which was re-figured by Webb (1972, pl. 1, figs. 13-1 5). Finlay's type specimens were collected

FRONDICULARIA RAM UROANA

137

TF 1103/1

FIGURE 3. Late Cretaceous paleogeographic reconstructionof the Southern Hemisphere showing localities at which Frondicularia rakauroana (Finlay) has been reported. Arrows show possible communication routes for this species. la = Marlborough, New Zealand; l b = Southern Hawke's Bay, New Zealand; I C = Northland, New Zealand; 2 = Lord Howe Rise, DSDP Leg 2 1 , Site 208; 3 = Seymour Island; 4 = Minilya Well no. 1, Carnarvon Basin, Australia. Reconstruction after Smith and others (1 98 1) for 80 Ma.

F. rakauroana has not been reported for Frondicularia outside the southern high-latitude regions. GEOGRAPHIC AND STRATIGRAPHIC DISTRIBUTION

1

I

1.0

I

2.0

I

Breadth (mm)

FIGURE 2. Length-breadth measurements for specimens of Frondicularia rakauroana (Finlay) from Seymour Island (plotted by sample number) and the dimensions of primary type specimens from New Zealand (Finlay, 1939). Shaded area shows length-breadth field for all specimens of New Zealand material investigated by Webb (1972).

from the Haumurian (Maestrichtian) Laidmore Formation (middle Waipara River, New Zealand; Webb, 197 1). The angle between the long axis and equitant sutures appears to be slightly greater in the Seymour Island specimens (30"-3 5") than in the New Zealand material (