The Earliest Occurrence of Angiosperms in Southern Africa

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The earliest occurrence of Angiosperms in southern Africa

MS Zavada

Department of Biology, Providence College, 549 River Avenue, Providence, Rhode Island 02918-0001, United States of America e-mail: [email protected]

Received 22 December 2003, accepted in revised form 4 June 2004

Three outcrop localities and 28 onshore and offshore Beginning in the Albian, tricolpate and tricolporate cores and wells were sampled from the east coast, pollen types occur in low frequency with the monosul- Zululand and Durban Basins, the south coast onshore cate angiosperm pollen. This first occurrence of Algoa and the offshore Outeniqua Basins, and the west angiosperms in South Africa is more than 25 million coast Orange Basin. Samples ranging in age from the years later than the earliest global appearance of Late Jurassic to the Late Cretaceous were examined for angiosperms in the Middle East and north Africa. The megafossils, microfossils, and fossilised wood to deter- concurrent presence of monosulcate and tri-aperturate mine the first occurrence of angiosperms in southern pollen suggests that angiosperms migrated to South Africa. In all three regions angiosperms first appear in Africa via dispersal corridors and that angiosperms did the Aptian and they are represented by monosulcate, not originate in southern Africa. reticulate pollen genera, e.g. Clavatipollenites.

Introduction

Angiosperms are a monophyletic group (Judd et al. 2002). what bearing this may have on the subsequent development Although the time and the place of their origin is equivocal, of angiosperm floras in this region. their monophyly necessitates derivation from a common ancestor in a specific geographic location. It can be argued Material and Methods that with increasing distance from the geographic origin, angiosperms should appear proportionally later in the geo- Sample localities logic time. South Africa occupied a central position in Gondwana, Onshore and offshore Cretaceous sediments in South Africa having direct crustal connection to South America, were sampled for megafossils, microfossils and fossilised Antarctica, and Madagascar/India (Smith et al. 1994). East wood (Table 1, Figure 1). The easternmost Cretaceous Gondwana (Australia, Antarctica, Madagascar, India) started basin (Mozambique Basin) outcrops along the southeastern separation from West Gondwana (Africa and South America, coast of South Africa (Flores 1973, Dingle et al. 1983, Brown and the Falkland Plate) in the mid-Jurassic approximately et al. 1995, Figure 1). These Early Cretaceous sediments 170My before the final separation of South America and extend and thicken northward into Mozambique. The lower Africa in the Cenomanian (100My). The separation and sub- Cretaceous sediments are primarily comprised of the sequent breakup of Gondwana began in the late Jurassic Makatini Formation, which ranges in age from the Barremian and continued into the Cretaceous severing the continental to the late Aptian (McLachlan and McMillian 1979). There is dispersal corridors with the adjacent land masses (Brown et an outlier of the Makatini Fm. in the vicinity of the Umfolosi al. 1995). The earliest unequivocal global record of River, south of Mtubatuba in Zululand (Umkwelane Outlier, angiosperms is from the earliest Cretaceous (Berriasian– Frankel 1960) that is believed to represent the more wide- Valanginian) of Israel (Brenner 1996). There are earlier spread occurrence of the Makatini Fm. in the past. Two out- reports of angiosperm-like pollen from the Triassic of eastern crop localities were sampled in this basin, one locality in the North America (Cornet 1989, also see Litwin 1985, Doyle Mkuze Game Reserve, and the Umkwelane Outlayer (Table and Hotton 1991) and the Late Jurassic of France (Cornet 1, Figure 1). Four onshore cores (Figure 1(1–3 and 7), Table and Habib 1992), however, the taxonomic position of these 1), and three offshore wells (Figure 1(4–6), Table 1) were remains are equivocal. sampled for palynomorphs. The plant fossils recovered from The purpose of this study is to determine the earliest all of the localities in this basin include impression fossils, occurrence of angiosperms in southern Africa and discuss fossilised wood, and palynomorphs. South African Journal of Botany 2004, 70: 646–653 647

Table 1: First occurrence of angiosperms in outcrops and wells from the major depositional basins along the east, south and west coasts of southern Africa. The table gives the depth of the first occurrence and the age of the first occurrence based on foraminifera (Brown et al. 1995). Unless noted all wells are offshore (OS = Onshore). ‘Absent’ indicates that no angiosperms were recovered from that interval in that particu- lar outcrop or well. SWC = Side Wall Core

Well type Depth (m) Age of first occurrence Sample type East Coast (Mozambique Basin) 1) ZC (OS) 1 462 Albian Core 2) B (OS) 1 283 Albian Core 3) NZA (OS) Below 310 Albian Core 4) JC-C1 2 205 Aptian SWC 5) JC-A1 N/A Absent – Barremian – Aptian SWC 6) JC-B1 N/A Absent – Barremian SWC 7) ZU 1/77 (OS) N/A Absent – Barremian Core Mkuze Game Reserve N/A Absent – Barremian – Aptian Outcrop Umkwelane N/A Absent – Barremian – Aptian Outcrop

South Coast (Outeniqua and associated basins) 8) E-1 1 102–1 105 Aptian SWC 9) E-AA1 2 523 L. Aptian – Albian SWC 10) E-AD1 N/A Absent – Barremian – Aptian SWC 11) E-B1 1 205–1 210 Aptian Cutting 12) F-E1 1 702 Aptian SWC 13) PB-A1 N/A Absent – L. Jurassic – Barremian SWC 14) GA-B1 1 036–1 097 Aptian Cutting 15) G(b)Gemsbok-1 1 145–1 150 Albian Cutting 16) G(b)Springbok-1 1 481.7 Albian SWC 17) Hb-A1 910–920 Albian Cutting 18) AL 1/69 (OS) N/A Absent – Valanginian – Hauterivian SWC 19) BR 1/71 (OS) N/A Absent – Portlandian – Hauterivian SWC 20) BT 1/74 (OS) N/A Absent – Valanginian – Hauterivian SWC Dunbrodie N/A Absent – Berriasian – Aptian Outcrop

West Coast (Orange Basin) 21) DSDP-361 1 050 Albian Core 22) K-E1 3 752 Albian SWC 23) K-B1 3 900 Albian SWC 24) K-D1 3 174 Albian SWC 25) A-C1 2 612 Albian SWC 26) BA-A1 1 052–955 Albian Cutting 27) A-A1 2 452 E. Aptian – Albian SWC 28) A-D1 2 515 E. Aptian – Albian SWC

The Outeniqua and associated onshore basins occur Both the onshore and offshore localities from all three along the south coast of Africa. A single outcrop locality was regions collectively range in age from the Late Jurassic to sampled in the Kirkwood and Sundays River Formations the Late Cretaceous, and yielded a variety of plant fossil near Dumbrodie (Table 1, Figure 1). These formations range material. Plant fossils from some of the localities have been in age from Berriasian to early Aptian (Dingle et al. 1983). previously studied, e.g. the Makatini Fm, Zululand Basin Three onshore wells (Figure 1(18–20), Table 1) and ten off- (Frankel 1960, Flores 1973, Anderson and Anderson 1985), shore wells were sampled for palynomorphs. (Figure the Kirkwood and Sundays River Formations, Algoa and 1(8–17), Table 1). Compression and impression fossils, fos- Outeniqua Basins (Scott 1976, Stapleton and Beer 1977, silised wood and microfossils were recovered from this Anderson and Anderson 1985, Bamford 1986) and Orange basin. Basin (DSDP-361, McLachlan and Pieterse 1978, Bamford The Orange Basin occurs along the West coast, and eight and Corbett 1994, 1995). offshore wells were examined for palynomorphs (Figure The fossils collected from the outcrops during this study 1(21–28), Table 1). Among the eight offshore wells exam- are part of the permanent fossil collections of the Bernard ined, Deep Sea Drilling Project 361 located off the south- Price Institute of Palaeontology, University of the west coast of South Africa has been previously studied Witwatersrand, Johannesburg, RSA. The collections are (Figure 1(21), Table 1) (McLachlan and Pieterse 1978). currently housed in the Department of Biology, Providence Sample interval 48-23 of DSDP-361 was re-examined in this College, Providence, RI, USA. All residues and slides pre- study. This interval ranges in age from Aptian to pared from the cores, side wall cores, and cuttings are Cenomanian (MacLachlan and Pieterse 1978, Davey 1978). deposited at the Petroleum Agency, Parow, South Africa. 648 Zavada

southern Africa and India (Singh 1972, Herngreen and Chlonova 1981 and references therein, e.g. Figures 2–8). The earliest occurrence of angiosperms in southern Africa is BOTSWANA pollen from the Aptian interval of the offshore and onshore wells (Table 1). All of the Aptian occurrences of angiosperm

NAMIBIA MOZAMBIQUE pollen are derived from sidewall cores or cuttings, and are 1 susceptible to down hole contamination, and may be derived 2 from younger sediments (possibly Albian or younger). 3 7 Angiosperms may have been present in southern Africa by Mkuze Game Reserve the Aptian, however, they were not widespread, eleven of 28 22 the thirty-one localities produced no record of angiosperm 27 Umkwelane Outlayer 23 remains in intervals that ranged as high as Aptian. However, SOUTH AFRICA 5 24 6 in all of the offshore and onshore wells angiosperms are 25 4 present in Albian and younger sediments. 26 Dunbrodie 20 19 18 The most commonly recorded angiosperm pollen from 13 N Aptian aged sediments in the offshore and onshore wells are Clavatipollenites, Retimonocolpites, and/or Liliacidites 8 12 17 (Figures 9–16) all occur in low frequency, and are often sin- 11 0 400km 21 141516 gle occurrences (McLachlan and Pieterse 1978). Multiaperturate pollen (tricolpate and tricolporate types, Figures 17–26) is restricted to Albian and younger age sed- Figure 1: Map showing the approximate locations of the collection iments in all of the offshore and onshore wells examined in sites and the onshore and offshore wells. The black shaded areas this study. are the approximate extent of Cretaceous sediments within these depositional areas, the numbers correspond to the numbered wells Systematic palynology listed in Table 1 Pollen of possible Gnetalean affinity

Sample preparation The occurrence of Equisetosporites and Steevesipollenites, in association with Concavisporites sp., Cicatricosporites Fossil pollen in this study was macerated from the sedi- australiensis (Cookson) Potonie, Monosulcites sp., and an ments using a modified version of Barss and Williams abundance of Classopollis sp. relate the South Africa floras (1973). Pollen from the samples was examined using light, (Scott 1976, Mclachlian and Pieterse 1978) to those of early scanning electron (SEM), and transmission electron Cretaceous floras of South America (Doyle et al. 1977, microscopy (TEM). Light microscopic slides were prepared Herngreen and Chlonova 1981), and support the hypothesis by dehydration of the pollen residue in an alcohol series that a strong South American-African exchange of both (10%, 50%, 95%, 100%) followed by acetone, then xylene. plants and animals existed prior to the break up of Once in xylene, the sample was mixed with the polystyrene Gondwana (Amedegnato 1993, Storch 1993, Buffetaut and mounting medium ProTexx and permanent slides were Rage 1993). In addition, Cyclusphaera, a distinctive Lower made for examination on a Zeiss Axiophot light microscope. Cretaceous pollen type recovered from Argentina, is also The isolation of individual pollen grains from the pollen present in South African wells (Volkheimer et al. 1977, residues for SEM and TEM followed the method of Zavada Zavada 1987, 1992, Taylor et al. 1987), but is absent by the (2003). late Early Cretaceous, indicating that terrestrial dispersal Examination of the impression and compression fossils corridors were severed by this time. was done on a Zeiss SV-11 Stereomicroscope equipped for photomicroscopy. Petrographic thin sections were made of a Equisetosporites concinnus cross, radial and tangential section of the petrified wood recovered from various localities. Singh (1964) Figure 2: this pollen type is widespread in Lower Cretaceous sediments throughout the world and is Results common in the Lower Cretaceous section in southern Africa. It may have gnetalean affinities (Osborn et al. 1993). The collections of compression, impression, and petrifaction megafossils from the outcrop localities produced no speci- Steevesipollenites sp. mens that can unequivocally be considered angiosperm. None of the palynological samples taken from outcrop local- (McLachlan and Pieterse 1978), Figures 3–5. Several ities produced angiosperm pollen. All records of first species of this genus are present in the Triassic–Jurassic of angiosperm occurrence are based on pollen recovered from North America, South America and Africa (Cornet 1989). the onshore and offshore wells. Gross morphology of this pollen type suggests an affinity The pollen floras described in this study include taxa that with the Gnetales (Osborn et al. 1993). The pollen wall ultra- are typical of early Cretaceous floras from South America, structure of the form recovered from DSDP-361 also sug- South African Journal of Botany 2004, 70: 646–653 649

Figures 2–8: (2) SEM of Equisteosporites concinnus, scale bar = 5µm; (3–5) Steevesipollenites sp.; (3) SEM showing the robust ribs, scale bar = 5µm; (4) TEM showing two ribs, the thin footlayer, granular infrastructural layer and relatively thin tectum, scale bar = 2.5µm; (5) Longitudinal TEM section of a rib showing the continuous granular infrastructure, scale bar = 1.25µm; (6–8) Cycadopites sp.; (6) SEM, scale bar = 5µm; (7) TEM showing the columellate infrastructure. Note as the section becomes more tangential the cross sections of the columellae are circular (arrow) scale bar = 1µm; (8) TEM showing the thick tectum with small perforations (arrow), the thin cylindrical columellae, and thin footlayer, scale bar = 0.5µm gests a gnetalean affinity. The robust ribs (Figure 3) possess Clavatipollenites hughesii a thin tectum, a granular infrastructure and a thin continuous basal layer (Figures 4–5). Steevesipollenites has a pollen Couper (1958), Figures 9–11: this species is characterised morphology similar to that found in Ephedra and Welwitchia by being oval in outline, monosulcate with reticulate exine (Osborn et al. 1993), except for the thin basal layer, which is sculpturing (Figures 9–10). The muri of the reticulum appear thick in Ephedra and Welwitchia. somewhat angular (Figures 9–10). The pollen wall structure is tectate columellate, the tectum is thin, however, the basal Pollen of possible Angiosperm affinity layers appears thick and massive (Figure 11). It is believed to have chloranthalean affinities. Similar forms have been cf. Cycadopites sp. (Scott 1976, McLachlan and Pieterse recovered from fossil floral remains of the Chloranthaceae 1978), Figures 6–8. The specimens recovered from DSDP- (Archangelsky and Taylor 1993, Eklund et al. 1997, Friis et 361 have a gross morphology similar to Cycadopites, which al. 1997). is characterised by a monosulcate aperture, circular to oval shape, and a wall structure presumed to be alveolar or gran- Clavatipollenites minutus ular. All of these characteristics are indicative of pollen of cycadalean or bennettitalean affinity. The form recovered Brenner (1963), Figures 12–16: this species is characterised from DSDP-361 (Figures 6–8), however, possesses a thick by oval shape, monosulcate aperture and the reticulate tectum that is traversed by minute channels (i.e. the tectum exine sculpturing (Figures 12–14). The perforations of C. is microperforate) (Figures 7–8), an infrastructural layer of minutus are smaller then those of C. hughesi (compare thin cylindrical shaped columellae that rest on a thin basal Figure 9 and Figure 12). The pollen wall structure differs layer (Figures 7–8), a suite of characteristics more indicative from that of C. hughesi in having a thick tectum, thin stout of angiosperms. This pollen type can only be distinguished columellae (Figure 16), and a thin basal layer (Figure 15). C. from monosulcate, round to oval, psilate, cycad- or bennet- minutus is widespread in Lower Cretaceous sediments of titalean pollen with an alveolor or granular homogeneous South Africa. wall structure by pollen wall ultrastructure. Only one speci- men recovered from DSDP-361 was examined with TEM, Tri-aperturate Angiosperm pollen hence the stratigraphic range and distribution of this columellate pollen type in South Africa is unknown. Beginning in the Albian a low frequency of tricolpate or tri- 650 Zavada

Figures 9–15: (9–11) Clavatipollenites hughesii: (9) SEM, scale bar = 5µm; (10) SEM, scale bar = 5µm; (11) TEM of the same grain in Figure 10 showing massive footlayer, columellate infrastructure and thin tectum, scale bar = 5µm; (12–16) Clavatipollenites minutus: (12) SEM, scale bar = 5µm; (13) SEM of a grain similar to those in Figures 12 and 14, scale bar = 5µm; (14) SEM, scale bar = 5µm; (15) TEM of the same grain in Figure 12 showing thin footlayer, the columellate infrastructure and thick tectum, scale bar = 3.5µm; (16) TEM of the same grain in Figures 12 and 15 showing columellate infrastructure and thick tectum, scale bar = 0.75µm colporate pollen occurs concurrently with the monosulcate, in the Albian. Few of these pollen types from South Africa angiosperm pollen. This suggests that the migration of the have been investigated with SEM and TEM. These tech- earliest angiosperms into the South African region was soon niques can potentially increase the number of taxonomic followed by the more derived eudicots. Below is a represen- characters to better understand the botanical affinities of tri- tative suite of tri-aperturate pollen types recovered from aperturate pollen. Tricolporopollenites sp., recovered from DSDP-361. DSDP-361, is tricolporate, triangular in shape, oblate, the Fraxinoipollenites venustus: Singh (1971), Figure 17; colpi extending nearly to the poles (Figure 23). Exine sculp- Tricolpites sp. 4 (McLachlan and Pieterse 1978), Figure 18; turing is slightly rugulate (Figure 23). In non-apertural areas Tricolpites sp. 9 (McLachlan and Pieterse 1978), Figure 19; the pollen is atectate, homogeneous, and endexine Gemmatricolpites scabratus Van Hoeken-Klinkenberg 1964, appears to be present (a less electron dense inner layer Figures 20–21; than the outer atectate, homogeneous ectexine) (Figure Tricolpites sp. (McLachlan and Pieterse 1978), Figure 22; 24). Adjacent to the apertural region the tectum is thick and Tricolporopollenites sp. (Similar to Plate 5, Figure 25; is underlain by a granular to columellate infrastructure McLachlan and Pieterse 1978), Figures 23–26. which rest on a irregular basal layer (Figures 25–26), endexine appears to be present and thickens toward the Based on pollen size, shape, sculpturing and aperture type aperture (Figures 25–26). a variety of eudicots are present in South Africa beginning South African Journal of Botany 2004, 70: 646–653 651

Figures 17–26: (17) SEM of Fraxinoipollenites venustus, scale bar = 10µm; (18) SEM of Tricolpites sp. 4 (McLachlan and Pieterse 1978), scale bar = 5µm; (19) SEM of Tricolpites sp. 9 (McLachlan and Pieterse 1978), scale bar = 10µm; (20–21) Gemmatricolpites scabratus: (20) SEM, scale bar = 5µm; (21) SEM of the flip side of the grain illustrated in Figure 20, scale bar = 5µm; (22) SEM of Tricolpites sp., scale bar = 5µm; (23–26) Tricolporopollenites sp.; (23) SEM, scale bar = 5µm; (24) TEM of the apertural region of the same grain in Figure 23 showing the thick tectum, the infrastructural layer with irregular shaped columellae and the thickened inner layer, scale bar = 3µm; (25) TEM of the same grain in figure 23 in the region of the aperture showing the columellate-like structures in the the infrastructural region and what appears to be a less dense endexine (E), scale bar = 1.5µm; (26) TEM of the same grain in Figure 23 showing the homogeneous non-apertural wall, note the ragged, less dense inner layer which may represent endexine, scale bar = 1.5µm 652 Zavada

Discussion Cretaceous with gnetalean affinitiy and the widespread Gondwana occurrence of corystosperms and peltasperms South Africa occupied a central position in Gondwana during the early Mesozoic (Anderson and Anderson 1983, throughout the Triassic and the Early–Mid Jurassic (Brown 1985, Anderson et al. 1999) plant groups considered, at one et al. 1995). The South African region had land connections time or another, to be possible angiosperm sister groups, to southern South America, Antarctica, Madagascar/India, suggests that these Gondwana species are not involved in and Australia, and shared common faunal and floristic ele- the origin of angiosperms. Although southern Gondwana ments during the Triassic through the lowermost Cretaceous may not have been the geographic centre of the origin of the (Srivastava 1978, 1981, Herngreen and Chlonova 1981, angiosperms and may have occupied a distant and margin- Dettmann 1992, Doyle 1999). The breakup of the southern al relationship to the diversification of angiosperms in the continents began in the Late Jurassic and by the Barremian Cretaceous, all of the continents that comprised Gondwana, the South African region was separated from South America, except Antarctica (South America, Southern Africa, Antarctica and Madagascar/India. The rifting that took place Madagascar, Australia and India) are among the most floris- during these tectonic events led to the formation of deposi- tically diverse regions in the world today. The migration of tional basins that now occupy the east, south, and the west angiosperms via fluctuating dispersal corridors from a vari- coast of South Africa (Dingle et al. 1983). Palynological evi- ety of exotic sources during the Cretaceous into marginal dence from the Middle East and North Africa suggests that Gondwana regions, and the subsequent development of angiosperm originated during the earliest Cretaceous new dispersal corridors in the Tertiary due to the changing (Berriasian) (Brenner 1996), or at some time prior to the ear- positions of the continents, may have contributed to the high liest Cretaceous, and the diversification of the angiosperms floristic diversity observed in these regions. was centered in the North African–South American region (Doyle 1999). From the first unequivocal record of Acknowledgements — I wish to thank Dr James Benson of Santos angiosperms in Middle East and North Africa during the Ltd, Adelaide Australia who generated much of the palynological Berriasian (Brenner 1996) (145My), by the Barremian well data while at the Soekor, South Africa, and Dr Ian McLachlan of (115My) early angiosperm pollen records were consistently the Petroleum Agency, Parow, South Africa, and the Petroleum Agency who graciously allowed me to view their material and use present in North America, Europe, South America, north the data in Table 1. Africa and Asia and made up a small, but distinctive percentage of palynofloras from these regions (Traverse 1988, References Hughes 1994, and references therein). The first occurrence of angiosperms in South Africa is in Amedegnato C (1993) African-American relationships in the acridi- the Aptian, more than 25 million years after the first occur- ans (Insecta, Orthoptera). In: George W, Lavocat R (eds) The rence of angiosperm pollen in Middle East and North Africa African–South American Connection. Oxford Monographs on (Brenner 1996). In addition, angiosperm pollen records from Biogeography No. 7, Oxford Science Publications, New York, pp the Aptian in southern Africa are not widespread and make 59–75 up an almost negligible percentage of the palynofloras. All of Anderson JM, Anderson HM (1983) Palaeoflora of southern Africa: the Aptian angiosperm occurrences are from SWC, or cut- Molteno Formation (Triassic), Vol. 1: Part 1 — Introduction, Part tings. These types of samples are susceptible to down hole 2 — Dicroidium. AA Balkema, Rotterdam, 227pp contamination. The first unequivocal occurrence of Anderson JM, Anderson HM (1985) Palaeoflora of Southern Africa. Prodromus of South African Megafloras, Devonian to Lower angiosperms is in the Albian, however, if the Aptian occur- Cretaceous. AA Balkema, Rotterdam, 423pp rences and distribution of angiosperm pollen are accepted, Anderson JM, Anderson HM, Archangelsky S, Bamford M, Chandra angiosperms are not widespread floristic elements in South S, Dettmann M, Hill R, Mcloughlin S, Rosler O (1999) Patterns of Africa during the Aptian. The Albian occurrences of Gondwana plant colonisation and diversification. Journal of angiosperm pollen become more widespread and the occa- African Earth Sciences 28: 145–167 sional occurrence of tri-aperturate pollen types (tricolpates Archangelsky S, Taylor TN (1993) The ultrastructure of in situ and tricolporates) suggests that by the end of the Early Clavatipollenites pollen from the early Cretaceous of Patagonia. Cretaceous the frequency and abundance of angiosperms American Journal of Botany 80: 879–885 was rising throughout the South African region. 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It is during the Cenomanian that angiosperms Namaqualand coast, South Africa, onshore material. become consistently present in South African floras, and Palaeontologia Africana 32: 67–74 comprise a significant percentage of these palynofloras Barss MS, Williams GL (1973) Palynology and nannofossil process- (McLachlan and Pieterse 1978). ing techniques. Geological Survey of Canada, Paper 73-26, 25pp The relatively late arrival and diversification of Brenner GJ (1963) The spores and pollen of the Potomac Group of angiosperms in South Africa implies that the origin of Maryland. Maryland Department of Geology, Mines and Water Resources, Bulletin 27: 1–215 angiosperms did not occur in the South African region. The Brenner GJ (1996) Evidence for the earliest stage of angiosperm occurrence of plant remains from the Triassic through Early pollen evolution: a paleoequatorial section from Israel. In: Taylor South African Journal of Botany 2004, 70: 646–653 653

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