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Late Permian to early triassic microfloral assemblages from the Maji ya chumvi formation, Kenya
Review q] Palaeohotany and Palvnology, 72 ( 1992): 129 147 Elsevier Science Publishers B.V., Amsterdam
129
Late Permian to Early Triassic microfloral assemblages from the Maji ya Chumvi Formation, Kenya O. H a n k e l Sonder]brschungshereich 69, Technische Universit?it Berlin, Ackerstrafle 71 76, 1000 Berlin 65, Germany (Received October I, 1991; revised and accepted January 8, 1992)
ABSTRACT Hankel, O., 1992. Late Permian to Early Triassic microfloral assemblages from the Maji ya Chumvi Formation, Kenya. Rev. Palaeobol. Palynol., 72:129-147. Plant microfossils are recorded from a possible Permian Triassic transition in the Karoo Sequence of the Mombasa Basin of Kenya. The material examined comes from a shallow borehole which penetrates the Fish bed of the Maji ya Chumvi Formation. The section drilled is only 41 m thick and shows no obvious break of sedimentation. Productive samples from the lower and upper part of the bore have yielded microfloral assemblages which are distinct in their qualitative and quantitative composition. A comparison with microfloras of Australia shows that the assemblage from the lower part of the section can be correlated with those of the (upper) Protohaploxypinus microcorpus Zone (Late Permian) while the assemblages from the upper part of the section may be equated with those of the succeeding Lunatisporites pellucidus Zone (Early Triassic). If the P. microc~,rpus/ L. peUucMus zonal boundary is taken as the Permian Triassic boundary, then the correlation suggests that the section studied contains rocks of latest Permian and earliest Triassic age. The Permian Triassic boundary in the Mombasa Basin may then be expected to occur near the base of the Fish bed.
Introduction In the M o m b a s a Basin o f K e n y a ( F i g . l ) , the Permian, Triassic, and L o w e r Jurassic are represented by the K a r o o strata o f the D u r u m a G r o u p , a thick sequence o f p r e d o m i n a n t l y a r e n a c e o u s sediments o f c o n t i n e n t a l origin. W h i l e the lithos t r a t i g r a p h i c subdivision o f the D u r u m a G r o u p seems well-established ( C a n n o n et al., 1981; RaisAssa, 1988), the precise age o f the K a r o o f o r m a tions is uncertain, since age diagnostic fossils are rare. C o n s e q u e n t l y , previous a t t e m p t s to locate the P e r m i a n - T r i a s s i c b o u n d a r y a n d the Triassic Jurassic b o u n d a r y m u s t be considered as rather provisional. N o direct p a l a e o n t o l o g i c a l evidence exists for the p l a c e m e n t o f the T r i a s s i c - J u r a s s i c b o u n d a r y . Correspondence to: Dr. O. Hankel, Technische Universit~it Berlin. Sonderforschungsbereich 69, Ackerstral3e 71-76, WI000 Berlin 65, Germany. 0025-3227/92/$05.00
Some evidence, however, m a y be inferred from a c o m p a r i s o n with the u p p e r K a r o o Sequence o f Tanzania. T h e r e is a striking similarity between the m u l t i c o l o u r e d s a n d s t o n e s a n d siltstones o f the L o w e r M a z e r a s F o r m a t i o n a n d those o f the M a d a b a F o r m a t i o n in the Luwegu Basin which have been d a t e d as Early Jurassic (Hankel, 1987). If the L o w e r M a z e r a s F o r m a t i o n is o f the same age, then the Triassic Jurassic b o u n d a r y beds are p r o b a b l y not preserved in the M o m b a s a Basin since the M a z e r a s F o r m a t i o n rests with a m a j o r u n c o n f o r m i t y at its base on older f o r m a t i o n s o f Triassic age ( M a t o l a n i , M a r i a k a n i , U p p e r Maji ya Chumvi). The T r i a s s i c - J u r a s s i c b o u n d a r y w o u l d thus lie within the hiatus between the M a t o l a n i F o r m a t i o n a n d the M a z e r a s F o r m a t i o n , In contrast, there is a greater likelihood o f finding P e r m i a n Triassic b o u n d a r y beds in the M o m b a s a Basin. The present study provides palynological evidence for a possible P e r m i a n Triassic transition within the M a j i ya C h u m v i F o r m a t i o n .
~" 1992 - - Elsevier Science Publishers B.V. All rights reserved.
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M I ( ' R O F L O R A [ A~S[ MBLAGES FROM THE MAJI YA CHUMVI FORMATION. KENYA
In view of the debate concerning the position of the Permian-Triassic boundary it must be noted that the author follows the conventional scheme which regards the Griesbachian as the basal substage of the Triassic.
Stratigraphy Coarse clastics dominate the lithology of the Karoo strata of the Duruma Group. A notable exception are the sediments of the Maji ya Chumvi Formation with their general fine-grained lithology. In the type area the Maji ya Chumvi Formation has a thickness of 1200 m. A threefold subdivision has been proposed by Cannon et al. ( 1981 ). The lower and upper member of the formation are composed of fluviolacustrine deposits. Whitish to bright grey, medium- to coarse-grained sandstone and black shale characterize the lower member while grey, yellow and greenish, fine- to medium-grained, platy sandstones are typical of the upper member. The intervening sequence of the middle member is a lacustrine black shale. The basal part of this shale sequence is formed by a characteristic horizon which contains nodules with fish remains (Fish bed). The Fish bed is a thin (30-50 m), but consistent mudstone horizon that can be traced in N S direction over a strike length of at least 80 km (Cannon et al.. 1981). Fish remains from this marker horizon have been compared to the species Boreosomus gillioti Priem rather than identified (Miller, 1952). A specimen from a later collection has been identified as Australosomus sp. (Cannon et al., 1981). These two taxa are known from the Karoo of Malagasy where they occur in brackish water horizons of the Middle Sakamena Group of the Morondava Basin and in the marine Fish and Ammonite Beds of the Diego Basin (Besairie, 1971, pp.31, 306, 337: Uyeno, 1978). The ammonite fauna dates the latter unit as Early Triassic (Gyronitian/Upper Induan) (Besairie, 1971, p.29; Bando, 1977, p. 142). Based on these relationships an Early Triassic age has been accepted also for the Fish bed of Kenya (Cannon et al., 1981). This age assignment is consistent with the palynological data presented here. However, there is some doubt whether the Fish bed of Kenya may
13 l
be correlated with the Fish and Ammonite Beds of Malagasy. There seems to be an equal possibility that the Fish bed may be an equivalent of the Claraia Shale which underlies the Fish and Ammonite Beds (Fig.2). The Claraia Shale which represents the oldest Triassic sediments in the Diego Basin, contains fish-remains as well, and is of comparable lithology, thickness and stratigraphic position to the Fish bed of Kenya. A horizon coeval with the Fish bed occurs probably also in the Karoo of the Luwegu Basin of Tanzania where Australosomus has been recorded from strata of the Sumbadzi Member near Vikindu (Haughton, 1936: Stockley, 1936). The sediments of the Sumbadzi Member have been previously assigned in total to the Late Permian based on palynological data (Hankel, 1987). The microflora recovered is characterized by the abundance of Guttulapollenites harmonious Goubin and has been equated with the Lower Sakamena assemblages recorded by Goubin (1965). This microflora cannot be younger than those of the Pla3;lbrdiaspora crenulata Zone of Australia. A similar microflora has been reported by Dr. R. Weis from the laterally equivalent sediments of the Pangani Member (see Wopfner and Kaaya, 1991) and from Karoo sediments of the Rukwa Basin (Wescott et al., 1991). Recent investigations have shown that the sediments from higher parts of the Sumbadzi Member contain a younger microfloral assemblage which is equivalent either to the (upper) Protohaploxypinus microcorpus Zone or Lunatisporites pellucidus Zone of Australia (Hankel, unpubl, data). This assemblage resembles those of the P. microcorpus Zone of Foster (1982) but contains Lunatisporites pellucidus as a rare element. The microflora may correspond to assemblages reported earlier by Kreuser (1983). This suggests that the Permian Triassic boundary in Tanzania may be expected somewhere in the upper part of the Sumbadzi Member. The fish-bearing horizon recorded by Stockley (1936) may be taken provisionally to mark the base of the Triassic in the Karoo of the Luwegu Basin. It has been argued that the Fish bed of Kenya represents a brief marine incursion (Cannon et al., 1981). This may be true because the fish remains are known from marine sediments of the Diego
132
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Fig.2. Position of the Permian Triassic boundary in Karoo basins of East Africa and Madagascar.
Basin. However, the Fish bed may also represent a brackish water deposit since the fish remains are also known from horizons in the Middle Sakamena of the Morondava Basin which are probably not truly marine but brackish. It is, however, also possible that the sediments of the Fish bed are of lacustrine origin. The possibility that these fishes inhabited also a freshwater environment (anadromy) cannot be excluded. There is no palynological evidence for a marine influence. The microfloral assemblages recorded here do not contain marine phytoplankton. Their palynofacies is characterized by land-derived components only (spores and pollen, plant debris, fungal(?) remains). Other age diagnostic fossils known from the Maji ya Chumvi Formation are freshwater bivalves which have been recorded from a section outside the type area (Sabaki shale). The Sabaki shale was formerly believed to belong to the Taru Formation but was later shown to be an equivalent of the lower member of the Maji ya Chumvi Formation (Sanders, 1959). The freshwater bivalves have been identified as Palaeanodonta fischeri Amalitsky, a species which is believed to be of Late Permian (Tatarian) age (Gregory, 1921: Weir, 1938; Sanders, 1959). A Late Permian age of the Lower Maji ya Chumvi is consistent with the palynological results. Material The material examined comes from borehole PS-2 drilled by Chevron in 1984 in the central part
of the Mombasa Basin. Borehole PS-2 is located on the water pipeline road between the villages Samburu and Maji ya Chumvi, 3.7 km south of the M o m b a s a Nairobi road and 0.75 km west of the Matope road (sheet 197/4; coordinates 39 19'21"E 03 49'20"S). The core material is stored at the National Oil Corporation of Kenya (Nairobi). The borehole PS-2 reached a total depth of 41.0 m (Fig.3). Silty shale of the Middle Maji ya Chumvi extends from surface to a depth of 9.15 m. The bore then penetrated the organic rich mudstone of the Fish bed (9.15 38.2 m) which towards the top becomes more silty. From 38.2 m to total depth gritty sandstone and interbedded silty shale of the Lower Maji ya Chumvi occur. Detailed sampling of this core section resulted in 123 shale samples which have been processed using a standardized palynological technique (Hankel, 1991, p.130). Whether the section drilled is continuous or not is very difficult to judge. It can only be stated with confidence that at least no break of sedimentation is obvious but the presence of a hiatus cannot be ruled out. If a hiatus is present it probably occurs at the boundary between the lower and middle member of the Maji ya Chumvi Formation where a coarse sandstone bed is in contact with the succeeding mudstone of the Fish bed. The presence of a hiatus above this contact seems unlikely. This part of the section actually indicates a continuous sedimentation with a gradual transition from mud-
133
M I ( R O F L O R A [ ASS} M B L A G E S F R O M T H E MAJI YA C H U M V I F O R M A I I O N , KENYA
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Of the 123 core samples processed 19 samples yielded moderate to rich microfloral assemblages on which this study is based, 70 samples proved to be totally barren, the other 34 samples yielded unidentifiable spores and pollen grains in very low numbers, generally less than 5 specimens per slide. Their residues contained an abundance of pyrite framboids together with plant debris (cuticles and tracheids). The pyrite formation indicates that the shales were deposited in a strongly reducing environment. Of the 19 productive samples only one sample comes from the lower part of the bore (39.2 m) while the other 18 samples all come from the upper part (interval 6.8 15.0m). The assemblage from the lower part of the section has been recovered from a siltstone, 1 m below the base of the fish bed (Lower Maji ya Chumvi). The assemblages from the upper part of the section have been recovered from silty mudstones and siltstones below and above the top of the Fish bed (Middle Maji ya Chumvi). The intervening barren interval spans the lower and middle part of the Fish bed. The preservation of the palynomorphs in all samples is generally poor. Well-preserved speci-
mens are rare and have been found in only a few samples. In most cases it was only possible to assign the spore and pollen grains to major miospore groups or to identify them at the generic level. Identification at the species level was the exception. The material is held at the author's collection (catalogue number KE-88-PS-2).
List of taxa identified
Pteridophytic spores (A) Triletes (I) Laevigate forms Punctatisporites Ibrahim emend. Potonie et Kremp 1954 Punctatisporites sp. Retusotriletes Naumova emend. Streel 1964 Retusotriletes sp. (Plate V, 7) (2) Apiculate forms Apiculatisporis Potonid et Kremp I956 Apiculati, sT~oris sp. (Plate V, 4, 5) Osmundacidites Couper 1953 Osmundacidites senectus Balme 1963 (Plate 11, 5) Raistrickia Schopf, Wilson et Bentall emend. Potoni6 et Kremp 1954 Raistrickia sp. (Plate llI, I) I~,rrucosisporites Ibrahim emend. Smith et Butterworth 1967 Verrucosisporites sp. (Plate III, 3) (3) Murornate forms Dictvotriletes Naumova emend. Potonie et Kremp 1955 Dictyotriletes sp. (Plate V, 8)
O HANKEL
134
PLATE 1
9
10 (for e x p l a n a t i o n see p. 137)
11
MICROFI ORAl ASSI MBLAGES FROM THE MAJI YA CHUMVI FORMATION, KENYA
PLATE 11
(for explanation
see p . 1 3 7 )
135
1~6
P L A T E Ill
(} HANKIiL
MICROFLORAL ASSEMBLAGESFROM THE MAJI YA CHUMVI FORMATION.KENYA
Retitrih'tes Pierce emend. D6ring, Krutzsch, Mai el Schulz 1963
Retitriletes sp, Triplexisporites Foster 1979 Triplexisporites plmJbrdii (De Jersey et Hamilton) Foster 1979 (Plate I, I )
137
Lirnatulasporites limatulus (Playford) Helby ct Foster in Foster 1979 (Plate IV, 4, 5, 6, 7)
Lundhladispora Balme emend. Playford 1965 Lundhladispora willmottii Balme 1963 (Plate I, 5; Plate V, I) Lundhladispora spp. (Plate I, 4; Plate 11, 7; Plate IV, 8; Plate V, 11) (5) Zonate forms
(4) Cingulate forms Densoisporites Weyland et Krieger emend. Dettmann 1963 Densoisporiles complicatus Balme 1970 (Plate l, 3; Plate Ill, 4, 5; Plate V, 6) Densoisporites pla)Jbrdii (Balme) Dettmann 1963 (Plate I, 6, 10) Densoisporites sp. Limatuhtsporites Helby el Foster in Foster 1979
PLATE l (see p.134) All figures x 1000 unless otherwise stated. Number of single grain mount is indicated in parenthesis. I. Triph, xisporites pla31lbrdii (39,2-27) 2. Ephedripites sp. (15,0-8) 3. Densoisporites complicatus (11,0-3) 4. l.undbladispora sp. (8,2-2) 5. Lundbladispora willmottii (39,2-22) 6. Densoisporiles pla31/i~rdii ( I 1,9-1 ) 7. Lueckisporites virkkiae (39,2-28) 8. Prolohaploxypinus samoilovichii (9,6-15) 9. Lunatisporites pellucidus (9,6-7) 10. Densoi.sporites pla)Jbrdii ( 11,9-1 I ) 11. Lunatisporites mn'iaulensis (39,2-73 PLATE 11 (see p.1351 All figures x 1000 unless otherwise stated. Number of single grain mount is indicated in parenthesis. 1. Protohaploxypinus microcorpus (39,2-25) 2. Grebespora concentrica (8,8-9) 3. Maculalasporite.s sp. ( 11,0-1) 4. Kraeuselisporites cu.~pidus (15,0-14) 5. Osmunda~'Mites senectus ( 15,0-15) 6. Lunatisporites noviauh, nsi,~ (39,2-23) 7. Lundbladispora sp. (39,2-32) 8. Chordecystia chalasta, × 500 (39,2-1) PLATE Ili All figures × 1000 unless otherwise stated. Number of single grain mount is indicated in parenthesis. I. Raistrickia sp. (9,8-2) 2. Pla3Jbrdiaspora crenulata (39,2-26) 3. Verrucosisporites sp. (9,0-73 4. DensoisT~orites complicatus (9,6-13) 5. Densoisporites complicatu; (11,9-8) 6. Lunatisporites noviaulensis (39,2-13) 7. Lunatisporites pellucidus ( 15,0-11 ) 8. Lunatisporites pellucidus (9,6-11)
Kraeuseli~'porites Leschik emend. Scheuring 1974 Kraeuselivporites cuspMus Balme 1963 (Plate II, 4; Plate IV, 2)
Kraeuselisporiles spp. (6) Monopseudosaccate forms Pla3Jordiaspora Maheshwari el Banerji 1975 Pla3Jordiaspora crenulata (Wilson) Foster 1979 (Plate I11, 2)
OHANKEL
PLATE IV
MICROFLORAI ASSEMBLAGESFROM THE MAJI YA CHUMVI FORMATION,KENYA
139
Striatopodocarpites Sedova emend. Hart 1964 Striatopodocarpites spp. (Plate IV, 9)
G y m n o s p e r m o u s pollen (A) Monosaccites
(C) Monosulcate forms
Plicatipolh,nites Lele 1964 Plieatipolh,nites spp.
Cycadopites Wodehouse ex Wilson et Webster 1946 Cycadopitesjbllicularis Wilson et Webster 1946 (Plate V, 9, 10) Ephedripites Bolkhovitina ex Potoni6 1958 Ephedripites sp. (Plate 1, 2) Weylandites Bharadwaj et Srivastava 1969 Wevlandites sp.
(B) Disaccites ( 1) Non-taeniate forms Ali~porites Daugherty emend. Jansonius 1971 Ali.~porites sp. [kdcisporites Leschik emend. Klaus 1963 Faleisporites australis (De Jersey) Stevens 1981 Khmsipollenites Jansonius 1962 Klausipollenites sp. Pinuspollenites Raatz 1937 Pinuspolh,niles sp. Platvsaecus N a u m o v a ex Potoni6 et Klaus 1954 Phaysaceus spp. (Plate V, 12) Sulcatisporites Leschik emend. Nilsson 1958 Suh'atisporiles sp. l'itreisporites Leschik emend. Jansonius 1962 Vitreisporites sij~nalus Leschik 1955 (2) Taeniate forms Lueckisporites Potoni6 et Klaus emend. Klaus 1963 Lueckisporites virkkiae Potoni~ et Klaus emend. Clarke (Plate I, 7) Lunatisporites Leschik emend. De Jersey 1979 Lunatisporites mn,iaulensis (Leschik) Foster 1979 (Plate Plate II, 6; Plate Ili, 6) Lunalisporites pellucidus (Goubin) Helby ex De Jersey (Plate I, 9: Plate lIl, 7, 8) Lunatisporites spp, Protohaplox~7~inu~s Samoilovich emend. Hart 1964 Protohaploxypinus mierocorpus (Schaarschmidt) Clarke (Plate 11, I) Protohaploxypinus samoilovichii (Jansonius) Hart (Plate I, 8; Plate V, 2, 3) Protohaploxypinus spp.
Aletes
Grebespora Jansonius 1962 Grebespora concentrica Jansonius 1962 (Plate I1, 2: Plate IV, 3) Maculatasporites Tiwari 1965 Maculatasporites sp. (Plate [1, 3) lncertae sedis
Chordeeystia Foster 1979 Chordecystia ehalasta Foster 1979 (Plate 11, 8: Plate IV, 1, 10) 1976
Composition 1, 11 ;
PLATE IV All figures x I000 unless otherwise stated. N u m b e r of single grain m o u n t is indicated in parenthesis. 1. Chordecystia ehalasta (39,2-3) 2. Kraeuseli.q~oritescuspidus (11,0-4) 3. Grehesporaconcentrica (11,9-9) 4. Limatulasporites limatulus (9,4-2) 5. Limatulasporites limatulus (9,6-6) 6. Limatulosporites limatulus (11,3-2) 7. L#natulosporites limatulus (10,7-5) 8. Lundbladispora sp. (39,2-12) 9. Striatopodocarpites sp. (39,2-35) 10. Chordecystia chalasta (39,2-2)
1972
1965 1964
Two distinct microfloral assemblages have been recognized. The assemblage from the lower part of the section ("older assemblage") differs from the assemblages from the upper part of the section. The latter are very similar in their composition and can be treated, therefore, as a single assemblage ("younger assemblage"). The differences between the "older assemblage"
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M I ( R O F L O R A i A.SSEMBLAGES FROM THE MAJI YA ('HUMVI FORMATION. KENYA
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(39.2 m) and the "younger assemblage" (interval 6.8 15.0 m) exist in the qualitative as well as quantitative composition (Table I; Fig.4). However, they possess some unifying features. Both,
PLATE V All ligures x 1000 unless otherwise stated. Number of single grain mount is indicated in parenthesis. 1. Lundhladispora willmottii (39,2-15) 2. Protohaplo.x3'pinus samoilovichii (9,6-1) 3. Protohaploxypinus samoilovichii (15,0-10) 4. Apiculatisporis sp. (39,2-14) 5. Apiculatisporis sp. (10,7-2) 6. Densoisporites complicatus (9,4-3) 7. Retusotriletes sp. (9,6-14) 8. Dictyolriletes sp. (15,0-1) 9. Cvcadopites.[ollicularis (9,6-3) [O. Cvcadopites Jollicularis ( 15,0-12) 11. Lundbladispora sp. (10,7-4) 12. P/alysaccus sp. (11,9-10)
141
the "older assemblage" and the "younger assemblage", are dominated by cavate, trilete spores and taeniate, disaccate pollen. Among the cavate spores most frequent are forms assignable to Lundbladispora. The taeniate pollen are mainly represented by various species of Protohaploxypinus. Furthermore a characteristic constituent of all assemblages is Chordecystia chalasta Foster 1979, a taxon of unknown affinities. C. chalasta is very similar to Tympanicysta stoschiana Balme 1980, which, as Balme states, may be of fungal, algal or even animal origin. There are also no significant discrepancies concerning the proportion of non-taeniate, disaccate pollen ("older assemblage": 5%; "'younger assemblage": 3 -12%). The same applies to the monosulcate pollen ("older assemblage": 7%; younger assemblage: 2 9%). Monosaccate pollen and alete sporomorphs are present in some of the assemblages but these are extremely rare. No monolete spores have been observed. Of the 39 miospore taxa identified 15 taxa occur in the "older" and the "younger assemblage". The stratigraphically important species among these common elements are Lunatisporites noviauh, nsis and Pro t ohaplox)'pinus samoilo vichii. Apart from these unifying features the "older assemblage" and the "younger assemblage" differ markedly by the frequency of acavate and cavate, trilete spores and taeniate, disaccate pollen. Moreover, there is also a significant difference in the abundance of Chordecystia chalasta. The "older assemblage" is spore-dominated and contains 32% acavate spores, 38% cavate spores and only 18%
142
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MI('ROFLORAL ASSEMBLAGES FROM THE MAJI YA CHUMVI FORMATION. KENYA
taeniate pollen. Chordecystia chalasta constitutes 24% of the total assemblage. In contrast, the "younger assemblage" is pollen-dominated and contains 8 23% acavate spores, 12 37% cavate spores and 37 56% taeniate pollen. Chordecystia chalasta composes 4 10% of the total assemblage. Beside these quantitative differences there are also significant qualitative differences. The taxa which have been found only in the "older assemblage" are Triplexisporites pla3fordii, Lundbladi-
spora willmottii, PlaAfordiaspora crenulata, Lueckisporites virkkiae, Protohaploxypinus microcorpus and Weylandites sp. These species with the exception of L. willmottii are rare elements. Among the taxa identified which seem to be confined to the "younger assemblage" are such characteristic species as Densoisporites cornplicatus, D. playfordii,
Limatulasporites limatulus, Kraeuselisporites cuspidus and Lunatisporites pellucidus. With the exception of L. pellucidus which reaches proportions between 5 9% of the total assemblage all of these species are rare elements. The compositional differences suggest an age difference between the "'older" and the "younger assemblage", while their unifying features indicate that no floral break is present. Correlation The association of the palynomorph taxa which characterizes the "older assemblage" is typical of microfloras of the Late Permian. In contrast, the "'younger assemblage" contains some characteristic elements which demonstrate a close affinity with microfloras of the Early Triassic. This contrasting aspect of the assemblages together with their close stratigraphic association in borehole PS-2 suggests a comparison with Gondwana microfloras of latest Permian and earliest Triassic age (Fig.5). In Australia, microfloras of this age are repre~ sented by assemblages of the (upper) Protohaploxypinus microcorpus Zone and the succeeding Lunatisporites pellucidus Zone of Helby et al. (1987). Assemblages of these two palynozones are known principally from continental strata of eastern Australia through the work of Evans (1966), Helby (1974), De Jersey (1979) and Foster (1979,
143
1982). For intra-Australian correlation see Foster (1982, fig.4; 1983, p.116), Helby et al. (1987, fig.3), and Balme (1990, fig.10). A comparison shows that the "older assemblage" is similar to those of the P. microcorpus Zone of Foster (1982) and the upper P. microcorpus Zone of Helby et al. (1987), while the "younger assemblage" resembles those of the L. pellucidus Zone. The base of the L. pellucMus Zone is defined by the first common occurrence of Lunatisporites pellucidus which is generally not present in assemblages of the subjacent P. microcorpus Zone but may occur locally as a rare and inconsistent element (Foster, 1982: Helby et al., 1987). L. pellucMus is a consistent and common element of the "younger assemblage" and is absent in the "older assemblage". Correspondence exists also with respect to the presence of fungal(?) remains assigned to Chordecvstia chalasta. This taxon is a key element of assemblages described by Foster (1982) from the basal Rewan Formation of the Bowen Basin of Queensland. The species does not occur in the Play/brdiaspora crenulata Zone but first appears in the P. microcorpus Zone of Foster (1982). C, chalasta is a consistent element of the present assemblages. It is very abundant in the "'older assemblage" and common in the "younger assemblage". Other significant elements which are common in the P. microcorpus Zone and the "'older assemblage" are Triplexisporites pla3!Jbrdii, Play[brdia-
spora crenulata, Falcisporites australis, Lunatisporites noviaulensis, Protohaploxypinus microcorpus, P. samoilovichii, and the genera Lueckisporites and Weylandites. In contrast, assemblages of the L. pellucidus Zone and the "younger assemblage" share such characteristic species as
Densoisporites pla3fordii, Limatulasporites limatulus, Kraeuselisporites cuspidus, Falcisporites australis, Lunatisporites noviaulensis, L. pellucidus, and Protohaploxypinus samoilovichii. These similarities indicate that the "'older assemblage" may be correlated with the (upper) P. microcorpus Zone while the "younger assemblage" may be correlated with the L. pellucidus Zone of Australia. The precise age of the two succeeding zones has not been established yet, It is clear, however, that they span the Permian-Triassic boundary. Gen-
144
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Fig.5. Correlation of microfloral assemblages of Kenya with Late Permian:Early Triassic microfloras of Madagascar, Australia and Pakistan.
erally, the (upper) P. microcorpus Zone is regarded as Late Permian in age, while the L. pellucidus Zone is assigned to the lowermost Triassic (Griesbachian) (Helby et al., 1987; Balme, 1990). Whether their zonal boundary coincides with the Permian Triassic boundary or not is unknown. In the present study the top of the P. microcorpus Zone is taken provisionally as the Permian Triassic boundary. Assemblages of the Kraeuselisporites saeptatus Zone (Griesbachian-Smithian) recorded by Balme (1963) and Dolby and Balme (1976) from the Kockatea Shale of Western Australia are here regarded as younger than the L. pellucidus Zone. The Protohaploxypinus samoilovichii Zone is probably equivalent to the K. saeptatus Zone (Foster, 1983). Microfloral assemblages of Kenya that are closely comparable with those of the K. saeptatus Zone and the P. samoilovichii Zone are those reported from the Lower Mariakani Formation (Hankel, 1990, 1991). Plant microtbssil assemblages of Late Permian to Early Triassic age have been reported also from lhe Salt Range of Pakistan by Balme (1970). There, however, the Permian Triassic boundary lies within the hiatus between the Chhidru Formation and Mianwali Formation. The present assemblages are here regarded as younger than the Chhidru assemblages and older than the Mianwali assemblages. In Madagascar, the Permian-Triassic boundary
in the southern Morondava Basin has been located by Wright and Askin (1987) near the Lower/ Middle Sakamena contact using microfloras which correspond to Zone IsC and Zone llsA of Goubin (1965). Wright and Askin (1987) suggest that the Lower Sakamena assemblages may be correlated with the Pla£[brdias'pora crenulata Zone (see Foster, 1982), while the Middle Sakamena assemblages are said to be time equivalent with the (upper) P. microcorpus Zone and the L. pellucidus Zone of Australia. The Middle Sakamena assemblages have been distinguished principally by the frequency of L. pellucidus. Assemblages characterized by the abundance of L. pellucidus (up to 32%) have been correlated with the L. pellucidus Zone while assemblages which contain 2 12% L. pellucidus have been correlated with the (upper) P. microcorpus Zone. This view, however, is not advocated here. The majority of the assemblages equated with the (upper) P. microcorpus Zone by Wright and Askin (1987) is regarded here as equivalent to the L. pellucidus Zone as defined by Foster (1982). With the exception of samples C1, C6, 23 v, w, and x, which are characterized by the abundance of L. pellucidus, the Middle Sakamena assemblages reported by Wright and Askin (1987) are comparable with those of the "younger assemblage". Similarities exist with regard to the frequency of L. pellucidus, the presence of Densoisporites playJordii, L. noviaulensis, and species of Densoisporites,
MI( R O F L O R A I . ~,SSI M B L A G F S F R O M T H E MAJI YA ( ftl. MVI F O R M A l ION, K [ N Y A
Lundbladi.spora, Kraeuseli~porites, Protohaploxpinus, Ephedripites, and Chordeo'stia. Assemblages which are equivalent to the (upper) P. microcorpus Zone of Australia and comparable with the "older assemblage" may be present in the lower part of the Middle Sakamena. One possibility is that they are represented by Middle Sakamena assemblages which contain L. pellucidus as a rare element. The other possibility is that they may be present in a relatively thin interval not covered by the studies of Wright and Askin (1987). This problem, however, can only be resolved by further detailed studies near the Lower/Middle Sakamena contact. Other Gondwana microfloras which possibly come from near the Permian-Triassic boundary are only mentioned here. These are assemblages which have been recorded from the Raniganj/ Panther boundary of India (Bharadwaj and Tiwari, 1977), the Kurunegala area of Sri Lanka (Dahanayake et al., 1989), the Assango Member of Gabon (Jardin6, 1974), and the Beaufort Group and Molteno Formation of South Africa (Stapleton, 1978). Their relationship to the Permian Triassic boundary is unknown. No correlation with these assemblages is proposed here. With respect to the Permo-Triassic(?) microflora of Sri Lanka it is interesting to note that recent investigations indicate a Gondwanaland position of Sri Lanka close to Madagascar rather than India (Kr6ner, 1991). A significant link, between the present assemblages and microfloras of comparable age of the Northern Hemisphere exists, with respect to the presence of palynomorphs which may be of fungal origin. These fungal(?) remains occur in abundance in the "older assemblage" and are still relatively frequent in the "younger assemblage". In the present study they have been assigned to Chorde~Tstia chalasta Foster 1979, although they could as well be assigned to Tympani~3,sta stoschiana Balme 1980. The latter taxon has been described from strata of Griesbachian age of Greenland. Palynomorphs assignable to Tympanicysta occur in Late Permian and/or Early Triassic strata of Alaska, Canada, Europe, Pakistan and Western Australia (see Balme, 1980). Tympanic.vsta has been recorded
145
meanwhile also from the Permian-Triassic boundary beds of Italy (Visscher and Brugman, 1988), Israel (Eshet, 1990), and China (Ouyang Shu and Utting, 1990). Visscher and Brugman (1988) discussed the stratigraphic and ecologic importance of the phenomenon that microfloral assemblages of latest Permian and/or earliest Triassic age are often characterized by the abundance of fungal(?) remains assignable to the genus T.vmpanicysta. This "fungal event" at the transition from the Permian into the Triassic can be recognized in various parts of the Tethys, Europe and boreal regions (Visscher and Brugman, 1988). The presence of Chordecystia in assemblages from near the Permian Triassic boundary in eastern Australia (Foster, 1979), Madagascar (Wright and Askin, 1987) and Kenya as well as the records of TympanicTsta from the Lower Triassic of Western Australia and Pakistan (Balme, 1980) may indicate that this "fungal event" also occurred in various parts of Gondwana. As the "acritarch spike" of the Early Triassic (Balme, 1970) the "fungal event" is probably of worldwide importance. In this context the abundance of Chorde~Tstia in the present assemblages demonstrates their general affinity with microfloras of latest Permian/earliest Triassic age.
Conclusions
(I) The "older" and the "younger" assemblages have a clear affinity with microfloras known from near the Permian Triassic transition. (2) The assemblage from the uppermost part of the Lower Maji ya Chumvi ("older assemblage") may be correlated with those of the (upper) P. microcorpus Zone of Australia. (3) The assemblage from the lower part of the Middle Maji ya Chumvi ("younger assemblage") may be time equivalent with the L. pellucidus Zone of Australia and the lower Middle Sakamena assemblages of Madagascar. (4) The correlation suggests that the studied section of borehole PS-2 may contain rocks of latest Permian (Dorashamian?) and earliest Triassic (Griesbachian) age. (5) The Permian Triassic boundary in the Morn-
146
basa Basin may be expected to occur near the Lower/Middle Maji ya Chumvi contact. (6) The "fungal event" at the transition from the Permian into the Triassic known from various regions of the Northern Hemisphere can also be recorded from the Karoo of Kenya.
Acknowledgements This study is part of the research project "Karoo Kenya" (DFG-Ref. Pf 21/35-1). The financial support by the German Research Foundation (Bonn) is gratefully acknowledged. Thanks go to the project leaders H.D. Pflug (J.L.U. Giessen) and E. Klitzsch (T.U. Berlin). The permission to conduct research in Kenya was granted by the Office of the President (Research Permit No. OP. 13/001/17 C 240/'10). The author thanks the Department of Geology of the University of Nairobi, the National Oil Corporation of Kenya and the Chevron Overseas Petroleum Inc. (San Ramon) for their support.
References Balme, B.E., 1963. Plant microfossils from the Lower Triassic of Western Australia. Palaeontology, 6:12 40. Balme, B.E., 1970. Palynology of Permian and Triassic strata in the Salt Range and Surghar Range, West Pakistan. In: B. Kummel and C. Teichert (Editors), Stratigraphic Boundary Problems: Permian and Triassic of West Pakistan. Univ. Press Kansas, Spec. Publ., 4: 306-453. Balme, B.E., 1980. Palynology of Permian-Triassic boundary beds at Kap Stosch, East Greenland. Medd. om Gronl., 200(6}: 1-37. Balme, B.E., 1990. Australian Phanerozoic timescales: 7. Triassic biostratigraphic charts and explanatory notes. Bur. Miner. Resour. Aust., Record 1989/37, 28 pp. Bando, Y.. 1977. On some Lower Triassic ammonoids from Ankilokaza, Madagascar. Bull. Nat. Sci. Mus. Ser. C (Geol.), 3(2): 133- 142. Besairie, H., 1971. G~ologie de Madagascar. I. Les terrains s6dimentaires. Ann. Geol. Madagascar. 35: 1-463. Bharadwaj, D.C. and Tiwari, R.S., 1977. Permian Triassic miofloras from the Raniganj coalfield, India. Palaeobotanist, 24:26-49. Cannon, R.T., Simiyu Siambi, W.M.N. and Karanja, F.M., 1981. The proto-Indian ocean and a probable Palaeozoic Mesozoic triradial rift system in East Africa. Earth Planet. Sci. Lett., 52:419 426. Dahanayake, K., Jayasena, H.A.H., Singh, B.K., Tiwari, R.S. and Tripathi, A., 1989. A Permo-Triassic(?) plant microfossil assemblage from Sri Lanka. Rev. Palaeobot. Palynol., 58: 197- 203. De Jersey, N.J.. 1979. Palynology of the Permian Triassic
o H,'kNKEL transition in the western Bowen Basin. Publ. Geol. Surv. Queensl., 374, Palaeontol. Pap., 46: I 39. Dolby, J.H. and Balme, B.E. (1976): Triassic palynology of the Carnarvon Basin, Western Australia, Rev. Palaeobot. Palynol., 22:105 168. Eshet, Y., 1990. The palynostratigraphy of the Permian Triassic boundary in Israel: Two approaches to biostratigraphy. lsr. J. Earth Sci., 39: I 15. Evans, P.R., 1966. Mesozoic stratigraphic palynology in Australia. Australas. Oil Gas J., 12(6): 58 63. Foster, C.B., 1979. Permian plant microfossils of the Blair Athol Coal Measures, Baralaba Coal Measures, and basal Rewan Formation of Queensland. Publ. Geol. Surv. Queensl., 372, Paleontol. Pap., 45: I 244. Foster, C.B., 1982. Spore pollen assemblages of the Bowen Basin, Queensland (Australia): their relationship to the Permian Triassic boundary. Rev. Palaeobot. Palynol., 36: 165 183. Foster, C.B., 1983. Review of the time frame for the Permian of Queensland. In: Proc. Syrup. Permian Geol. Queensland, Geol. Soc. Aust. Queensl. Div., Brisbane, pp.107 120. Goubin, N., 1965. Description et r6partition des principaux pollenites permiens, triasiques et jurassiques des sondages du bassin de Morondava (Madagascar). Rev. Inst. Fr. Pat., 20: I415- 1461. Gregory, J.W., 1921. The Rift Valleys and Geology of East Africa. Seeley, London, 479 pp. Hankel, O., 1987. Lithostratigraphic subdivision of the Karoo rocks of the Luwegu Basin (Tanzania) and their biostratigraphic classification based on microfloras, macrofloras, fossil woods and vertebrates. Geol. Rundsch., 76:539 -565. Hankel, O., 1990. Lower Triassic spores and pollen from a borehole in the Lower Mariakani Formation (Karoo) of Kenya. Berl. Geowiss. Abh., A 120(2): 639 678. Hankel, O., 1991. Early Triassic plant microfossils from the Kavee Quarry section of the Lower Mariakani Formation, Kenya. Rev. Palaeobot. Palynol., 68:127 145. Haughton, S.H., 1936. On some Karoo tishes from East Africa. Q. J. Geol. Soc. London, 92:58 61. Helby, R., 1974. Review of Late Permian and Triassic palynof ogy of New South Wales. Geol. Soc. Aust. Spec. Publ., 4: I41 155. Helby, R., Morgan, R. and Partridge, A.D., 1987. A palynological zonation of the Australian Mesozoic. Mem. Assoc. Australas. Paleontol., 4:1 94. Jardin6, S., 1974. Microflores des formations du Gabon attribuees au Karroo. Rev. Palaeobot. Palynol., 17:75 112. Kreuser, T., I983. Stratigraphie der Karroo-Becken in OstTanzania. Geol. Inst., Univ. K61n, Sonderver6ffentl., 45, 217 pp. Kreuser, T., 1990. Permo-Trias im Ruhuhu-Becken (Tansania) und anderen Karoo-Becken von SE-Afrika. Geol. Inst.. Univ. K61n, Sonderver6ffentl., 75, 131 pp. Kr6ner, A., 1991. African linkage of Precambrian Sri Lanka. Geol. Rundsch., 80: 429-440. Miller, J.M., 1952. Geology of the Mariakani Mackinnon road area. Rep. Geol. Surv. Kenya, 20:1 32. Ouyang Shu and Utting, J., 1990. Palynology of Upper Permian and Lower Triassic rocks, Meishan, Changxing County,
M I ( ' R O F L O R A L A S S E M B L A G E S F R O M T H E MAJI YA ( ' H U M V [ F O R M A T I O N , K t N Y A
Zhejiang Province, China. Rev. Palaeobot. Palynol., 66: 65 103. Rais-Assa, R., 1988. Stratigraphy and geodynamics of the Mombasa Basin (Kenya) in relation to the genesis of the prolo-lndian Ocean. Geol. Mag., 125:141 [47. Sanders, L.D.. I959. GeoLogy of the Mid-Galana area. Rep. Geol. Surv. Kenya, 46: I 50. Stapleton, RP., 1978. A microflora from a possible Permo Triassic transition in South Africa. Rev. Palaeobot. Palynol., 25:253 258. Stockley, G.M., 1936. A further contribution on the Karroo rocks of Tanganyika Terrilory. Q. J. Geol. Soc. London, 92: I 31. Uyeno. T., 1978. On some Lower Triassic tishes from Ankilokaza, Madagascar. Bull. Nat. Sci. Mus. Ser. C. (Geol.), 4(4): 193 198. Venkatachala. B.S. and Rawat, M.S., 1978. Early Triassic palynoflora from the subsurface of Purnea, Bihar, India. J. Palynol.. 14:59 70.
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Visscher, H. and Brugman, W.A., 1988. The Permian Triassic boundary in the southern Alps: a palynological approach. Mem. Soc. Geol. Ital., 34: 121-128. Weir, J., 1938. Palaeanodonta from Kenya and Burma. In: J. Weir (Editor), Oll a second collection of tk)ssils and rocks fl'om Kenya made by Miss M. McKinnon Wood. Monogr. Geol. Dept. Hunt. Mus. Glasgow Univ., 5:12 15. Wescolt, W.A.. Krebs, W.N., Engelhardl, D.W. and Cunningham, S.M., 1991. New Biostratigraphic age dates from the Lake Rukwa Rift Basin in western Tanzania. AAPG Bull., 75(7): 1255 1263. Wopfner, H. and Kaaya, C.Z., 1991. Stratigraphy and morphotectonics of Karoo deposits of the northern Selous Basin, Tanzania. Geol. Mag., 128(4): 319 334. Wright, R.P. and Askin. R.A., 1987. The Permian Triassic boundary in the southern Morondava Basin as defined by planl microfossils. In: G.D. McKenzie (Editor), Gondwana Six. Stratigraphy, Sedimentology and Paleontology. Geophys. Monogr.,Washington, 41:157 166.
129
Late Permian to Early Triassic microfloral assemblages from the Maji ya Chumvi Formation, Kenya O. H a n k e l Sonder]brschungshereich 69, Technische Universit?it Berlin, Ackerstrafle 71 76, 1000 Berlin 65, Germany (Received October I, 1991; revised and accepted January 8, 1992)
ABSTRACT Hankel, O., 1992. Late Permian to Early Triassic microfloral assemblages from the Maji ya Chumvi Formation, Kenya. Rev. Palaeobol. Palynol., 72:129-147. Plant microfossils are recorded from a possible Permian Triassic transition in the Karoo Sequence of the Mombasa Basin of Kenya. The material examined comes from a shallow borehole which penetrates the Fish bed of the Maji ya Chumvi Formation. The section drilled is only 41 m thick and shows no obvious break of sedimentation. Productive samples from the lower and upper part of the bore have yielded microfloral assemblages which are distinct in their qualitative and quantitative composition. A comparison with microfloras of Australia shows that the assemblage from the lower part of the section can be correlated with those of the (upper) Protohaploxypinus microcorpus Zone (Late Permian) while the assemblages from the upper part of the section may be equated with those of the succeeding Lunatisporites pellucidus Zone (Early Triassic). If the P. microc~,rpus/ L. peUucMus zonal boundary is taken as the Permian Triassic boundary, then the correlation suggests that the section studied contains rocks of latest Permian and earliest Triassic age. The Permian Triassic boundary in the Mombasa Basin may then be expected to occur near the base of the Fish bed.
Introduction In the M o m b a s a Basin o f K e n y a ( F i g . l ) , the Permian, Triassic, and L o w e r Jurassic are represented by the K a r o o strata o f the D u r u m a G r o u p , a thick sequence o f p r e d o m i n a n t l y a r e n a c e o u s sediments o f c o n t i n e n t a l origin. W h i l e the lithos t r a t i g r a p h i c subdivision o f the D u r u m a G r o u p seems well-established ( C a n n o n et al., 1981; RaisAssa, 1988), the precise age o f the K a r o o f o r m a tions is uncertain, since age diagnostic fossils are rare. C o n s e q u e n t l y , previous a t t e m p t s to locate the P e r m i a n - T r i a s s i c b o u n d a r y a n d the Triassic Jurassic b o u n d a r y m u s t be considered as rather provisional. N o direct p a l a e o n t o l o g i c a l evidence exists for the p l a c e m e n t o f the T r i a s s i c - J u r a s s i c b o u n d a r y . Correspondence to: Dr. O. Hankel, Technische Universit~it Berlin. Sonderforschungsbereich 69, Ackerstral3e 71-76, WI000 Berlin 65, Germany. 0025-3227/92/$05.00
Some evidence, however, m a y be inferred from a c o m p a r i s o n with the u p p e r K a r o o Sequence o f Tanzania. T h e r e is a striking similarity between the m u l t i c o l o u r e d s a n d s t o n e s a n d siltstones o f the L o w e r M a z e r a s F o r m a t i o n a n d those o f the M a d a b a F o r m a t i o n in the Luwegu Basin which have been d a t e d as Early Jurassic (Hankel, 1987). If the L o w e r M a z e r a s F o r m a t i o n is o f the same age, then the Triassic Jurassic b o u n d a r y beds are p r o b a b l y not preserved in the M o m b a s a Basin since the M a z e r a s F o r m a t i o n rests with a m a j o r u n c o n f o r m i t y at its base on older f o r m a t i o n s o f Triassic age ( M a t o l a n i , M a r i a k a n i , U p p e r Maji ya Chumvi). The T r i a s s i c - J u r a s s i c b o u n d a r y w o u l d thus lie within the hiatus between the M a t o l a n i F o r m a t i o n a n d the M a z e r a s F o r m a t i o n , In contrast, there is a greater likelihood o f finding P e r m i a n Triassic b o u n d a r y beds in the M o m b a s a Basin. The present study provides palynological evidence for a possible P e r m i a n Triassic transition within the M a j i ya C h u m v i F o r m a t i o n .
~" 1992 - - Elsevier Science Publishers B.V. All rights reserved.
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OCEAN
M I ( ' R O F L O R A [ A~S[ MBLAGES FROM THE MAJI YA CHUMVI FORMATION. KENYA
In view of the debate concerning the position of the Permian-Triassic boundary it must be noted that the author follows the conventional scheme which regards the Griesbachian as the basal substage of the Triassic.
Stratigraphy Coarse clastics dominate the lithology of the Karoo strata of the Duruma Group. A notable exception are the sediments of the Maji ya Chumvi Formation with their general fine-grained lithology. In the type area the Maji ya Chumvi Formation has a thickness of 1200 m. A threefold subdivision has been proposed by Cannon et al. ( 1981 ). The lower and upper member of the formation are composed of fluviolacustrine deposits. Whitish to bright grey, medium- to coarse-grained sandstone and black shale characterize the lower member while grey, yellow and greenish, fine- to medium-grained, platy sandstones are typical of the upper member. The intervening sequence of the middle member is a lacustrine black shale. The basal part of this shale sequence is formed by a characteristic horizon which contains nodules with fish remains (Fish bed). The Fish bed is a thin (30-50 m), but consistent mudstone horizon that can be traced in N S direction over a strike length of at least 80 km (Cannon et al.. 1981). Fish remains from this marker horizon have been compared to the species Boreosomus gillioti Priem rather than identified (Miller, 1952). A specimen from a later collection has been identified as Australosomus sp. (Cannon et al., 1981). These two taxa are known from the Karoo of Malagasy where they occur in brackish water horizons of the Middle Sakamena Group of the Morondava Basin and in the marine Fish and Ammonite Beds of the Diego Basin (Besairie, 1971, pp.31, 306, 337: Uyeno, 1978). The ammonite fauna dates the latter unit as Early Triassic (Gyronitian/Upper Induan) (Besairie, 1971, p.29; Bando, 1977, p. 142). Based on these relationships an Early Triassic age has been accepted also for the Fish bed of Kenya (Cannon et al., 1981). This age assignment is consistent with the palynological data presented here. However, there is some doubt whether the Fish bed of Kenya may
13 l
be correlated with the Fish and Ammonite Beds of Malagasy. There seems to be an equal possibility that the Fish bed may be an equivalent of the Claraia Shale which underlies the Fish and Ammonite Beds (Fig.2). The Claraia Shale which represents the oldest Triassic sediments in the Diego Basin, contains fish-remains as well, and is of comparable lithology, thickness and stratigraphic position to the Fish bed of Kenya. A horizon coeval with the Fish bed occurs probably also in the Karoo of the Luwegu Basin of Tanzania where Australosomus has been recorded from strata of the Sumbadzi Member near Vikindu (Haughton, 1936: Stockley, 1936). The sediments of the Sumbadzi Member have been previously assigned in total to the Late Permian based on palynological data (Hankel, 1987). The microflora recovered is characterized by the abundance of Guttulapollenites harmonious Goubin and has been equated with the Lower Sakamena assemblages recorded by Goubin (1965). This microflora cannot be younger than those of the Pla3;lbrdiaspora crenulata Zone of Australia. A similar microflora has been reported by Dr. R. Weis from the laterally equivalent sediments of the Pangani Member (see Wopfner and Kaaya, 1991) and from Karoo sediments of the Rukwa Basin (Wescott et al., 1991). Recent investigations have shown that the sediments from higher parts of the Sumbadzi Member contain a younger microfloral assemblage which is equivalent either to the (upper) Protohaploxypinus microcorpus Zone or Lunatisporites pellucidus Zone of Australia (Hankel, unpubl, data). This assemblage resembles those of the P. microcorpus Zone of Foster (1982) but contains Lunatisporites pellucidus as a rare element. The microflora may correspond to assemblages reported earlier by Kreuser (1983). This suggests that the Permian Triassic boundary in Tanzania may be expected somewhere in the upper part of the Sumbadzi Member. The fish-bearing horizon recorded by Stockley (1936) may be taken provisionally to mark the base of the Triassic in the Karoo of the Luwegu Basin. It has been argued that the Fish bed of Kenya represents a brief marine incursion (Cannon et al., 1981). This may be true because the fish remains are known from marine sediments of the Diego
132
0
KENYA HOHBBSA BASIN This
Haji
work
TANZANIA LUMEGU BASIN
TANZANIA RUHUHU BASIN
HALAfiA5Y HORONDAUB BASIN
HELAfiASY DIEGO BASIN
Hanke|data) (unpubl.
Kreuser 199B
+ BMPight l k i n LgB7
Belairie 1971
Middle yl ChuRvt
Kingori Sunbadzi
TRIASSIC
Fish
PERMIAN Haji
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bed
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~
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Beds
Fig.2. Position of the Permian Triassic boundary in Karoo basins of East Africa and Madagascar.
Basin. However, the Fish bed may also represent a brackish water deposit since the fish remains are also known from horizons in the Middle Sakamena of the Morondava Basin which are probably not truly marine but brackish. It is, however, also possible that the sediments of the Fish bed are of lacustrine origin. The possibility that these fishes inhabited also a freshwater environment (anadromy) cannot be excluded. There is no palynological evidence for a marine influence. The microfloral assemblages recorded here do not contain marine phytoplankton. Their palynofacies is characterized by land-derived components only (spores and pollen, plant debris, fungal(?) remains). Other age diagnostic fossils known from the Maji ya Chumvi Formation are freshwater bivalves which have been recorded from a section outside the type area (Sabaki shale). The Sabaki shale was formerly believed to belong to the Taru Formation but was later shown to be an equivalent of the lower member of the Maji ya Chumvi Formation (Sanders, 1959). The freshwater bivalves have been identified as Palaeanodonta fischeri Amalitsky, a species which is believed to be of Late Permian (Tatarian) age (Gregory, 1921: Weir, 1938; Sanders, 1959). A Late Permian age of the Lower Maji ya Chumvi is consistent with the palynological results. Material The material examined comes from borehole PS-2 drilled by Chevron in 1984 in the central part
of the Mombasa Basin. Borehole PS-2 is located on the water pipeline road between the villages Samburu and Maji ya Chumvi, 3.7 km south of the M o m b a s a Nairobi road and 0.75 km west of the Matope road (sheet 197/4; coordinates 39 19'21"E 03 49'20"S). The core material is stored at the National Oil Corporation of Kenya (Nairobi). The borehole PS-2 reached a total depth of 41.0 m (Fig.3). Silty shale of the Middle Maji ya Chumvi extends from surface to a depth of 9.15 m. The bore then penetrated the organic rich mudstone of the Fish bed (9.15 38.2 m) which towards the top becomes more silty. From 38.2 m to total depth gritty sandstone and interbedded silty shale of the Lower Maji ya Chumvi occur. Detailed sampling of this core section resulted in 123 shale samples which have been processed using a standardized palynological technique (Hankel, 1991, p.130). Whether the section drilled is continuous or not is very difficult to judge. It can only be stated with confidence that at least no break of sedimentation is obvious but the presence of a hiatus cannot be ruled out. If a hiatus is present it probably occurs at the boundary between the lower and middle member of the Maji ya Chumvi Formation where a coarse sandstone bed is in contact with the succeeding mudstone of the Fish bed. The presence of a hiatus above this contact seems unlikely. This part of the section actually indicates a continuous sedimentation with a gradual transition from mud-
133
M I ( R O F L O R A [ ASS} M B L A G E S F R O M T H E MAJI YA C H U M V I F O R M A I I O N , KENYA
BOREHOLE
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=
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Fig.3. Stratigraphic position of the section of borehole PS-2 showing source of material examined. stones at the base to silty mudstones and finally silty shales at the top. Miospore yield and preservation
Of the 123 core samples processed 19 samples yielded moderate to rich microfloral assemblages on which this study is based, 70 samples proved to be totally barren, the other 34 samples yielded unidentifiable spores and pollen grains in very low numbers, generally less than 5 specimens per slide. Their residues contained an abundance of pyrite framboids together with plant debris (cuticles and tracheids). The pyrite formation indicates that the shales were deposited in a strongly reducing environment. Of the 19 productive samples only one sample comes from the lower part of the bore (39.2 m) while the other 18 samples all come from the upper part (interval 6.8 15.0m). The assemblage from the lower part of the section has been recovered from a siltstone, 1 m below the base of the fish bed (Lower Maji ya Chumvi). The assemblages from the upper part of the section have been recovered from silty mudstones and siltstones below and above the top of the Fish bed (Middle Maji ya Chumvi). The intervening barren interval spans the lower and middle part of the Fish bed. The preservation of the palynomorphs in all samples is generally poor. Well-preserved speci-
mens are rare and have been found in only a few samples. In most cases it was only possible to assign the spore and pollen grains to major miospore groups or to identify them at the generic level. Identification at the species level was the exception. The material is held at the author's collection (catalogue number KE-88-PS-2).
List of taxa identified
Pteridophytic spores (A) Triletes (I) Laevigate forms Punctatisporites Ibrahim emend. Potonie et Kremp 1954 Punctatisporites sp. Retusotriletes Naumova emend. Streel 1964 Retusotriletes sp. (Plate V, 7) (2) Apiculate forms Apiculatisporis Potonid et Kremp I956 Apiculati, sT~oris sp. (Plate V, 4, 5) Osmundacidites Couper 1953 Osmundacidites senectus Balme 1963 (Plate 11, 5) Raistrickia Schopf, Wilson et Bentall emend. Potoni6 et Kremp 1954 Raistrickia sp. (Plate llI, I) I~,rrucosisporites Ibrahim emend. Smith et Butterworth 1967 Verrucosisporites sp. (Plate III, 3) (3) Murornate forms Dictvotriletes Naumova emend. Potonie et Kremp 1955 Dictyotriletes sp. (Plate V, 8)
O HANKEL
134
PLATE 1
9
10 (for e x p l a n a t i o n see p. 137)
11
MICROFI ORAl ASSI MBLAGES FROM THE MAJI YA CHUMVI FORMATION, KENYA
PLATE 11
(for explanation
see p . 1 3 7 )
135
1~6
P L A T E Ill
(} HANKIiL
MICROFLORAL ASSEMBLAGESFROM THE MAJI YA CHUMVI FORMATION.KENYA
Retitrih'tes Pierce emend. D6ring, Krutzsch, Mai el Schulz 1963
Retitriletes sp, Triplexisporites Foster 1979 Triplexisporites plmJbrdii (De Jersey et Hamilton) Foster 1979 (Plate I, I )
137
Lirnatulasporites limatulus (Playford) Helby ct Foster in Foster 1979 (Plate IV, 4, 5, 6, 7)
Lundhladispora Balme emend. Playford 1965 Lundhladispora willmottii Balme 1963 (Plate I, 5; Plate V, I) Lundhladispora spp. (Plate I, 4; Plate 11, 7; Plate IV, 8; Plate V, 11) (5) Zonate forms
(4) Cingulate forms Densoisporites Weyland et Krieger emend. Dettmann 1963 Densoisporiles complicatus Balme 1970 (Plate l, 3; Plate Ill, 4, 5; Plate V, 6) Densoisporites pla)Jbrdii (Balme) Dettmann 1963 (Plate I, 6, 10) Densoisporites sp. Limatuhtsporites Helby el Foster in Foster 1979
PLATE l (see p.134) All figures x 1000 unless otherwise stated. Number of single grain mount is indicated in parenthesis. I. Triph, xisporites pla31lbrdii (39,2-27) 2. Ephedripites sp. (15,0-8) 3. Densoisporites complicatus (11,0-3) 4. l.undbladispora sp. (8,2-2) 5. Lundbladispora willmottii (39,2-22) 6. Densoisporiles pla31/i~rdii ( I 1,9-1 ) 7. Lueckisporites virkkiae (39,2-28) 8. Prolohaploxypinus samoilovichii (9,6-15) 9. Lunatisporites pellucidus (9,6-7) 10. Densoi.sporites pla)Jbrdii ( 11,9-1 I ) 11. Lunatisporites mn'iaulensis (39,2-73 PLATE 11 (see p.1351 All figures x 1000 unless otherwise stated. Number of single grain mount is indicated in parenthesis. 1. Protohaploxypinus microcorpus (39,2-25) 2. Grebespora concentrica (8,8-9) 3. Maculalasporite.s sp. ( 11,0-1) 4. Kraeuselisporites cu.~pidus (15,0-14) 5. Osmunda~'Mites senectus ( 15,0-15) 6. Lunatisporites noviauh, nsi,~ (39,2-23) 7. Lundbladispora sp. (39,2-32) 8. Chordecystia chalasta, × 500 (39,2-1) PLATE Ili All figures × 1000 unless otherwise stated. Number of single grain mount is indicated in parenthesis. I. Raistrickia sp. (9,8-2) 2. Pla3Jbrdiaspora crenulata (39,2-26) 3. Verrucosisporites sp. (9,0-73 4. DensoisT~orites complicatus (9,6-13) 5. Densoisporites complicatu; (11,9-8) 6. Lunatisporites noviaulensis (39,2-13) 7. Lunatisporites pellucidus ( 15,0-11 ) 8. Lunatisporites pellucidus (9,6-11)
Kraeuseli~'porites Leschik emend. Scheuring 1974 Kraeuselivporites cuspMus Balme 1963 (Plate II, 4; Plate IV, 2)
Kraeuselisporiles spp. (6) Monopseudosaccate forms Pla3Jordiaspora Maheshwari el Banerji 1975 Pla3Jordiaspora crenulata (Wilson) Foster 1979 (Plate I11, 2)
OHANKEL
PLATE IV
MICROFLORAI ASSEMBLAGESFROM THE MAJI YA CHUMVI FORMATION,KENYA
139
Striatopodocarpites Sedova emend. Hart 1964 Striatopodocarpites spp. (Plate IV, 9)
G y m n o s p e r m o u s pollen (A) Monosaccites
(C) Monosulcate forms
Plicatipolh,nites Lele 1964 Plieatipolh,nites spp.
Cycadopites Wodehouse ex Wilson et Webster 1946 Cycadopitesjbllicularis Wilson et Webster 1946 (Plate V, 9, 10) Ephedripites Bolkhovitina ex Potoni6 1958 Ephedripites sp. (Plate 1, 2) Weylandites Bharadwaj et Srivastava 1969 Wevlandites sp.
(B) Disaccites ( 1) Non-taeniate forms Ali~porites Daugherty emend. Jansonius 1971 Ali.~porites sp. [kdcisporites Leschik emend. Klaus 1963 Faleisporites australis (De Jersey) Stevens 1981 Khmsipollenites Jansonius 1962 Klausipollenites sp. Pinuspollenites Raatz 1937 Pinuspolh,niles sp. Platvsaecus N a u m o v a ex Potoni6 et Klaus 1954 Phaysaceus spp. (Plate V, 12) Sulcatisporites Leschik emend. Nilsson 1958 Suh'atisporiles sp. l'itreisporites Leschik emend. Jansonius 1962 Vitreisporites sij~nalus Leschik 1955 (2) Taeniate forms Lueckisporites Potoni6 et Klaus emend. Klaus 1963 Lueckisporites virkkiae Potoni~ et Klaus emend. Clarke (Plate I, 7) Lunatisporites Leschik emend. De Jersey 1979 Lunatisporites mn,iaulensis (Leschik) Foster 1979 (Plate Plate II, 6; Plate Ili, 6) Lunalisporites pellucidus (Goubin) Helby ex De Jersey (Plate I, 9: Plate lIl, 7, 8) Lunatisporites spp, Protohaplox~7~inu~s Samoilovich emend. Hart 1964 Protohaploxypinus mierocorpus (Schaarschmidt) Clarke (Plate 11, I) Protohaploxypinus samoilovichii (Jansonius) Hart (Plate I, 8; Plate V, 2, 3) Protohaploxypinus spp.
Aletes
Grebespora Jansonius 1962 Grebespora concentrica Jansonius 1962 (Plate I1, 2: Plate IV, 3) Maculatasporites Tiwari 1965 Maculatasporites sp. (Plate [1, 3) lncertae sedis
Chordeeystia Foster 1979 Chordecystia ehalasta Foster 1979 (Plate 11, 8: Plate IV, 1, 10) 1976
Composition 1, 11 ;
PLATE IV All figures x I000 unless otherwise stated. N u m b e r of single grain m o u n t is indicated in parenthesis. 1. Chordecystia ehalasta (39,2-3) 2. Kraeuseli.q~oritescuspidus (11,0-4) 3. Grehesporaconcentrica (11,9-9) 4. Limatulasporites limatulus (9,4-2) 5. Limatulasporites limatulus (9,6-6) 6. Limatulosporites limatulus (11,3-2) 7. L#natulosporites limatulus (10,7-5) 8. Lundbladispora sp. (39,2-12) 9. Striatopodocarpites sp. (39,2-35) 10. Chordecystia chalasta (39,2-2)
1972
1965 1964
Two distinct microfloral assemblages have been recognized. The assemblage from the lower part of the section ("older assemblage") differs from the assemblages from the upper part of the section. The latter are very similar in their composition and can be treated, therefore, as a single assemblage ("younger assemblage"). The differences between the "older assemblage"
() H&NKI~L
14O
PLATE V
9
M I ( R O F L O R A i A.SSEMBLAGES FROM THE MAJI YA ('HUMVI FORMATION. KENYA
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i io
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Fig.4. Frequency of major miospore groups and fungal(?) remains (Chordecystia chalasta)in borehole PS-2.
(39.2 m) and the "younger assemblage" (interval 6.8 15.0 m) exist in the qualitative as well as quantitative composition (Table I; Fig.4). However, they possess some unifying features. Both,
PLATE V All ligures x 1000 unless otherwise stated. Number of single grain mount is indicated in parenthesis. 1. Lundhladispora willmottii (39,2-15) 2. Protohaplo.x3'pinus samoilovichii (9,6-1) 3. Protohaploxypinus samoilovichii (15,0-10) 4. Apiculatisporis sp. (39,2-14) 5. Apiculatisporis sp. (10,7-2) 6. Densoisporites complicatus (9,4-3) 7. Retusotriletes sp. (9,6-14) 8. Dictyolriletes sp. (15,0-1) 9. Cvcadopites.[ollicularis (9,6-3) [O. Cvcadopites Jollicularis ( 15,0-12) 11. Lundbladispora sp. (10,7-4) 12. P/alysaccus sp. (11,9-10)
141
the "older assemblage" and the "younger assemblage", are dominated by cavate, trilete spores and taeniate, disaccate pollen. Among the cavate spores most frequent are forms assignable to Lundbladispora. The taeniate pollen are mainly represented by various species of Protohaploxypinus. Furthermore a characteristic constituent of all assemblages is Chordecystia chalasta Foster 1979, a taxon of unknown affinities. C. chalasta is very similar to Tympanicysta stoschiana Balme 1980, which, as Balme states, may be of fungal, algal or even animal origin. There are also no significant discrepancies concerning the proportion of non-taeniate, disaccate pollen ("older assemblage": 5%; "'younger assemblage": 3 -12%). The same applies to the monosulcate pollen ("older assemblage": 7%; younger assemblage: 2 9%). Monosaccate pollen and alete sporomorphs are present in some of the assemblages but these are extremely rare. No monolete spores have been observed. Of the 39 miospore taxa identified 15 taxa occur in the "older" and the "younger assemblage". The stratigraphically important species among these common elements are Lunatisporites noviauh, nsis and Pro t ohaplox)'pinus samoilo vichii. Apart from these unifying features the "older assemblage" and the "younger assemblage" differ markedly by the frequency of acavate and cavate, trilete spores and taeniate, disaccate pollen. Moreover, there is also a significant difference in the abundance of Chordecystia chalasta. The "older assemblage" is spore-dominated and contains 32% acavate spores, 38% cavate spores and only 18%
142
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MI('ROFLORAL ASSEMBLAGES FROM THE MAJI YA CHUMVI FORMATION. KENYA
taeniate pollen. Chordecystia chalasta constitutes 24% of the total assemblage. In contrast, the "younger assemblage" is pollen-dominated and contains 8 23% acavate spores, 12 37% cavate spores and 37 56% taeniate pollen. Chordecystia chalasta composes 4 10% of the total assemblage. Beside these quantitative differences there are also significant qualitative differences. The taxa which have been found only in the "older assemblage" are Triplexisporites pla3fordii, Lundbladi-
spora willmottii, PlaAfordiaspora crenulata, Lueckisporites virkkiae, Protohaploxypinus microcorpus and Weylandites sp. These species with the exception of L. willmottii are rare elements. Among the taxa identified which seem to be confined to the "younger assemblage" are such characteristic species as Densoisporites cornplicatus, D. playfordii,
Limatulasporites limatulus, Kraeuselisporites cuspidus and Lunatisporites pellucidus. With the exception of L. pellucidus which reaches proportions between 5 9% of the total assemblage all of these species are rare elements. The compositional differences suggest an age difference between the "'older" and the "younger assemblage", while their unifying features indicate that no floral break is present. Correlation The association of the palynomorph taxa which characterizes the "older assemblage" is typical of microfloras of the Late Permian. In contrast, the "'younger assemblage" contains some characteristic elements which demonstrate a close affinity with microfloras of the Early Triassic. This contrasting aspect of the assemblages together with their close stratigraphic association in borehole PS-2 suggests a comparison with Gondwana microfloras of latest Permian and earliest Triassic age (Fig.5). In Australia, microfloras of this age are repre~ sented by assemblages of the (upper) Protohaploxypinus microcorpus Zone and the succeeding Lunatisporites pellucidus Zone of Helby et al. (1987). Assemblages of these two palynozones are known principally from continental strata of eastern Australia through the work of Evans (1966), Helby (1974), De Jersey (1979) and Foster (1979,
143
1982). For intra-Australian correlation see Foster (1982, fig.4; 1983, p.116), Helby et al. (1987, fig.3), and Balme (1990, fig.10). A comparison shows that the "older assemblage" is similar to those of the P. microcorpus Zone of Foster (1982) and the upper P. microcorpus Zone of Helby et al. (1987), while the "younger assemblage" resembles those of the L. pellucidus Zone. The base of the L. pellucMus Zone is defined by the first common occurrence of Lunatisporites pellucidus which is generally not present in assemblages of the subjacent P. microcorpus Zone but may occur locally as a rare and inconsistent element (Foster, 1982: Helby et al., 1987). L. pellucMus is a consistent and common element of the "younger assemblage" and is absent in the "older assemblage". Correspondence exists also with respect to the presence of fungal(?) remains assigned to Chordecvstia chalasta. This taxon is a key element of assemblages described by Foster (1982) from the basal Rewan Formation of the Bowen Basin of Queensland. The species does not occur in the Play/brdiaspora crenulata Zone but first appears in the P. microcorpus Zone of Foster (1982). C, chalasta is a consistent element of the present assemblages. It is very abundant in the "'older assemblage" and common in the "younger assemblage". Other significant elements which are common in the P. microcorpus Zone and the "'older assemblage" are Triplexisporites pla3!Jbrdii, Play[brdia-
spora crenulata, Falcisporites australis, Lunatisporites noviaulensis, Protohaploxypinus microcorpus, P. samoilovichii, and the genera Lueckisporites and Weylandites. In contrast, assemblages of the L. pellucidus Zone and the "younger assemblage" share such characteristic species as
Densoisporites pla3fordii, Limatulasporites limatulus, Kraeuselisporites cuspidus, Falcisporites australis, Lunatisporites noviaulensis, L. pellucidus, and Protohaploxypinus samoilovichii. These similarities indicate that the "'older assemblage" may be correlated with the (upper) P. microcorpus Zone while the "younger assemblage" may be correlated with the L. pellucidus Zone of Australia. The precise age of the two succeeding zones has not been established yet, It is clear, however, that they span the Permian-Triassic boundary. Gen-
144
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.u.
Zone DJULFINH
Fig.5. Correlation of microfloral assemblages of Kenya with Late Permian:Early Triassic microfloras of Madagascar, Australia and Pakistan.
erally, the (upper) P. microcorpus Zone is regarded as Late Permian in age, while the L. pellucidus Zone is assigned to the lowermost Triassic (Griesbachian) (Helby et al., 1987; Balme, 1990). Whether their zonal boundary coincides with the Permian Triassic boundary or not is unknown. In the present study the top of the P. microcorpus Zone is taken provisionally as the Permian Triassic boundary. Assemblages of the Kraeuselisporites saeptatus Zone (Griesbachian-Smithian) recorded by Balme (1963) and Dolby and Balme (1976) from the Kockatea Shale of Western Australia are here regarded as younger than the L. pellucidus Zone. The Protohaploxypinus samoilovichii Zone is probably equivalent to the K. saeptatus Zone (Foster, 1983). Microfloral assemblages of Kenya that are closely comparable with those of the K. saeptatus Zone and the P. samoilovichii Zone are those reported from the Lower Mariakani Formation (Hankel, 1990, 1991). Plant microtbssil assemblages of Late Permian to Early Triassic age have been reported also from lhe Salt Range of Pakistan by Balme (1970). There, however, the Permian Triassic boundary lies within the hiatus between the Chhidru Formation and Mianwali Formation. The present assemblages are here regarded as younger than the Chhidru assemblages and older than the Mianwali assemblages. In Madagascar, the Permian-Triassic boundary
in the southern Morondava Basin has been located by Wright and Askin (1987) near the Lower/ Middle Sakamena contact using microfloras which correspond to Zone IsC and Zone llsA of Goubin (1965). Wright and Askin (1987) suggest that the Lower Sakamena assemblages may be correlated with the Pla£[brdias'pora crenulata Zone (see Foster, 1982), while the Middle Sakamena assemblages are said to be time equivalent with the (upper) P. microcorpus Zone and the L. pellucidus Zone of Australia. The Middle Sakamena assemblages have been distinguished principally by the frequency of L. pellucidus. Assemblages characterized by the abundance of L. pellucidus (up to 32%) have been correlated with the L. pellucidus Zone while assemblages which contain 2 12% L. pellucidus have been correlated with the (upper) P. microcorpus Zone. This view, however, is not advocated here. The majority of the assemblages equated with the (upper) P. microcorpus Zone by Wright and Askin (1987) is regarded here as equivalent to the L. pellucidus Zone as defined by Foster (1982). With the exception of samples C1, C6, 23 v, w, and x, which are characterized by the abundance of L. pellucidus, the Middle Sakamena assemblages reported by Wright and Askin (1987) are comparable with those of the "younger assemblage". Similarities exist with regard to the frequency of L. pellucidus, the presence of Densoisporites playJordii, L. noviaulensis, and species of Densoisporites,
MI( R O F L O R A I . ~,SSI M B L A G F S F R O M T H E MAJI YA ( ftl. MVI F O R M A l ION, K [ N Y A
Lundbladi.spora, Kraeuseli~porites, Protohaploxpinus, Ephedripites, and Chordeo'stia. Assemblages which are equivalent to the (upper) P. microcorpus Zone of Australia and comparable with the "older assemblage" may be present in the lower part of the Middle Sakamena. One possibility is that they are represented by Middle Sakamena assemblages which contain L. pellucidus as a rare element. The other possibility is that they may be present in a relatively thin interval not covered by the studies of Wright and Askin (1987). This problem, however, can only be resolved by further detailed studies near the Lower/Middle Sakamena contact. Other Gondwana microfloras which possibly come from near the Permian-Triassic boundary are only mentioned here. These are assemblages which have been recorded from the Raniganj/ Panther boundary of India (Bharadwaj and Tiwari, 1977), the Kurunegala area of Sri Lanka (Dahanayake et al., 1989), the Assango Member of Gabon (Jardin6, 1974), and the Beaufort Group and Molteno Formation of South Africa (Stapleton, 1978). Their relationship to the Permian Triassic boundary is unknown. No correlation with these assemblages is proposed here. With respect to the Permo-Triassic(?) microflora of Sri Lanka it is interesting to note that recent investigations indicate a Gondwanaland position of Sri Lanka close to Madagascar rather than India (Kr6ner, 1991). A significant link, between the present assemblages and microfloras of comparable age of the Northern Hemisphere exists, with respect to the presence of palynomorphs which may be of fungal origin. These fungal(?) remains occur in abundance in the "older assemblage" and are still relatively frequent in the "younger assemblage". In the present study they have been assigned to Chorde~Tstia chalasta Foster 1979, although they could as well be assigned to Tympani~3,sta stoschiana Balme 1980. The latter taxon has been described from strata of Griesbachian age of Greenland. Palynomorphs assignable to Tympanicysta occur in Late Permian and/or Early Triassic strata of Alaska, Canada, Europe, Pakistan and Western Australia (see Balme, 1980). Tympanic.vsta has been recorded
145
meanwhile also from the Permian-Triassic boundary beds of Italy (Visscher and Brugman, 1988), Israel (Eshet, 1990), and China (Ouyang Shu and Utting, 1990). Visscher and Brugman (1988) discussed the stratigraphic and ecologic importance of the phenomenon that microfloral assemblages of latest Permian and/or earliest Triassic age are often characterized by the abundance of fungal(?) remains assignable to the genus T.vmpanicysta. This "fungal event" at the transition from the Permian into the Triassic can be recognized in various parts of the Tethys, Europe and boreal regions (Visscher and Brugman, 1988). The presence of Chordecystia in assemblages from near the Permian Triassic boundary in eastern Australia (Foster, 1979), Madagascar (Wright and Askin, 1987) and Kenya as well as the records of TympanicTsta from the Lower Triassic of Western Australia and Pakistan (Balme, 1980) may indicate that this "fungal event" also occurred in various parts of Gondwana. As the "acritarch spike" of the Early Triassic (Balme, 1970) the "fungal event" is probably of worldwide importance. In this context the abundance of Chorde~Tstia in the present assemblages demonstrates their general affinity with microfloras of latest Permian/earliest Triassic age.
Conclusions
(I) The "older" and the "younger" assemblages have a clear affinity with microfloras known from near the Permian Triassic transition. (2) The assemblage from the uppermost part of the Lower Maji ya Chumvi ("older assemblage") may be correlated with those of the (upper) P. microcorpus Zone of Australia. (3) The assemblage from the lower part of the Middle Maji ya Chumvi ("younger assemblage") may be time equivalent with the L. pellucidus Zone of Australia and the lower Middle Sakamena assemblages of Madagascar. (4) The correlation suggests that the studied section of borehole PS-2 may contain rocks of latest Permian (Dorashamian?) and earliest Triassic (Griesbachian) age. (5) The Permian Triassic boundary in the Morn-
146
basa Basin may be expected to occur near the Lower/Middle Maji ya Chumvi contact. (6) The "fungal event" at the transition from the Permian into the Triassic known from various regions of the Northern Hemisphere can also be recorded from the Karoo of Kenya.
Acknowledgements This study is part of the research project "Karoo Kenya" (DFG-Ref. Pf 21/35-1). The financial support by the German Research Foundation (Bonn) is gratefully acknowledged. Thanks go to the project leaders H.D. Pflug (J.L.U. Giessen) and E. Klitzsch (T.U. Berlin). The permission to conduct research in Kenya was granted by the Office of the President (Research Permit No. OP. 13/001/17 C 240/'10). The author thanks the Department of Geology of the University of Nairobi, the National Oil Corporation of Kenya and the Chevron Overseas Petroleum Inc. (San Ramon) for their support.
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