Devonian palynology of Saudi Arabia

Review of Palaeobotany and Palynology

Elsevier Publishing Company, Amsterdam - The Netherlands

D E V O N I A N P A L Y N O L O G Y OF SAUDI ARABIA D A R W I N O. H E M E R AND P A U L W. N Y G R E E N

Arabian American Oil Company, Dhahran (Saudi Arabia) Chevron Oil Company, Oklahoma City, Okla. (U.S.A.)

(Received August 28, 1966)

SUMMARY

Palynological zonation has been established in a Devonian section encountered in a borehole in northern Saudi Arabia, and comparison is made with the published palynological zonation of the Russian Platform. The environmenta. significance of differing assemblages in three different lithologies of a single 30-ftl stratigraphic interval is discussed.

INTRODUCTION

The .VaufFormation of Saudi Arabia has been dated lower Middle and Lower Devonian on the basis of a small megafossil collection. A borehole, S-462, latitude 30°30'N, longitude 40°25'E, was drilled by the Arabian American Oil Company approximately 50 miles from the Jauf Formation type section exposed at Jabal A1-Abd in northern Saudi Arabia (Fig.l). Devonian sediments, 1,341 ft. thick, were encountered in the well, consisting of sandstone and shale, with minor amounts of coal. Palynological analysis indicates the presence of a probable Upper Devonian, Lower Frasnian section and a Middle Devonian, Givetian section (Table I). Marine microplankton were not found in the well and a palynological study of the marine Jauf outcrop has not been made. It is concluded the Devonian sections found in S-462 are an extension of the formation not previously identified.

TECHNIQUE Samples of 30 ft. of consolidated cuttings, separated by 40-ft. intervals, as well as several core samples, were processed from the 1,341 ft. of Devonian sediments. The various lithologies were separated from one composite sample and the fractions processed individually. Rev. Palaeobotan. PalynoL, 5 (1967) 51-61

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RESULTS Starting at depth 1,465 ft. in the bore-hole, four palynological zones have been recognized underlying the Sakakah Formation of Cretaceous age. These zones are listed below. 54

Re v. Palaeobotan. Palynol.,

5 (1967) 51-61

Zone I (depth 1,465-1,670ft.) Lithology: Gray and light blue, in part carbonaceous, shale. Remarks: The species Chomotriletes vedugenesis, Emphanisporites rotatus, Geminospora lemurata, and spores of the Ancyrospora ancyrea form are represented in this zone as well as species of the genera Acanthotriletes, Spinozonotriletes, and probably Ibrahimispores. A probable Upper Devonian age assignment for this uppermost zone is based on the presence of Chomotriletes vedugensis which has been reported from the Frasnian of Russia and Australia, on abundance of the species Geminospora lemurata described from the Australian Frasnian, and comparison of other forms in the zone with Frasnian forms reported by Russian investigators. The species of Aneyrospora reported in the Middle Devonian of Russia and Spitzbergen are different from those found in the Arabian section. However, A. ancyrea as described by RICHARDSON (1960, 1962) from the Middle Devonian of Scotland is similar to the Arabian species, but because of the differing assemblages it can be assumed that the Arabian A. ancyrea type is restricted to the Upper Devonian.

Zone H (depth 1,670-1,940ft.) Lithology: Gray, argillaceous, carbonaceous sandstone and blue siltstone and shale. Remarks: The large number of species representing the genus Calyptosporites and the upper occurrence of Samarisporites are distinguishing features of this zone. Arabian Calyptosporites species are conspecific with some described by NAUMOVA (1953) under the generic names Hymenozonotriletes and Archaeozonotriletes from the Lower Frasnian, indicating an Upper Devonian age for this zone.

Zone III (depth 1,940-2,300ft.) Lithology: Green blue and dark gray shale; tan, micaceous, pyritic, slightly shaly, carbonaceous sandstone and minor amounts of coal. Remarks: The predominance of very large spores in this zone as represented by the genera Biharisporites, Spinozonotriletes, and Hymenozonotriletes is characteristic of the Middle Devonian assemblages described by NAUMOVA (1953), KEDO (1955), CHmRIKOVA (1959), MCGREGOR (1960), RICHARDSON (1960, 1962, 1965), and ALLZN (1965). This characteristic is a significant factor in assigning a Middle Devonian age to this zone. The Arabian species Lophozonotriletes sp.1, which is similar to L. exeisus NAUMOVA, is the most common form in this zone. This species is distinguished by eccentrically concentrated equatorial protuberances which vary in size and shape.

Rev. Palaeobotan.Palynol., 5 (1967) 51-61

55

Zone IV (depth 2,700-2,750ft.) Lithology: Tan, micaceous, pyritic, shaly, in part carbonaceous sandstone and gray, silty, micaceous, carbonaceous shale. Remarks: All species of this zone are found in the overlying sections and the zone is characterized by a marked reduction in the number of species. This is coincident with a marked lithological change from a predominant sandstone section of Zone IV to the overlying shale section which contains coal. The zone is dated by comparison with published sources as probable Givetian.

DISCUSSION

One of the more striking aspects of the Arabian section is the occurrence of forms with bifurcating spines in only the uppermost zone. Species of Ancyrospora are recorded elsewhere from sediments of Middle Devonian age and would seem to dictate such an age assignment for the uppermost zone. As noted previously, the accompanying species of this palynological zone strongly suggest an Upper Devonian age. It has been postulated by RICHAROSON (1965) that the presence of such forms might be related to the presence of the parent plants in an environment in close proximity to fresh water. The Arabian well section, however, does not support this hypothesis as the sections in which the Ano,rospora florule is absent is more carbonaceous and is in part a coal, indicating swamp conditions. Zone II, with its distinct group of Calyptosporites species and the absence of forms with bifurcating spines and of the very large forms found inZones II1 and IV is definitely a transitional zone between typical Upper and typical Middle Devonian assemblages. This zone is comparable with Naumova's zones XII-XIV, basal Erasnian. One 30-ft. sample from Zone III contained three conspicuous lithologies. These were separated into fractions of: (l)blue-gray shale; (2)coal, black carbona-

PLATE I 1. 2. 3. 4. 5. 6. 7. 8. 9.

Chomotriletes sp.1, × 500. Ancyrospora ancyrea type, x 2 5 0 . Emphanisporites rotatus MCGREGOR, × 500. Acanthotriletes sp.1, ×300. Geminospora lemurata BALME, × 500. Calyptosporites sp.2, ×300. ?Chelinospora, x 5 0 0 . Geminospora sp.2, x 500. Geminospora sp.2, x 5 0 0 . 10. Spinozonotriletes spA, x 3 0 0 . 11. Bullatisporites sp., × 500. 12. Biharisporites sp., x 200. 56

Rev. Palaeobotan. Palynol., 5 (I 967) 51-61

PLATE I

ceous shale and brown shale; (3) green shale. These lithologies are interpreted to represent a swamp and closely related inorganic sediments. Marked changes in number of species and total abundance occur among these three lithologies representing three related but different environments. Similar changes from comparative environmental controlled sediments have been noted by HOVVMEISTER et al. (1955), NEVES (1958, 1961), STAPLIN (1960), SULLIVAN(1962), SMITH (1964), and were extensively detailed by MARSHALLand SMITH(1964). in the coal and associated shales the spores found in the largest numbers were Samarisporites, Lophozonotriletes, ?Chelinospora, large Spinozonotriletes, Forms 1 and 7, and many small spores with ornamentation of the apiculate type. The gray-shale fraction contained the greatest variety of species and in particular Hymenozonotriletes incisus, Retusotriletes sp. 1, Samarisporites, Rhabdosporites, ?Hystricosporites sp.l, Spinozonotriletes naumovii, Biharisporites, and Forms 1, 5, 6, and 7. MARSHALL and SM1TH (1964) found that the greatest variety of species occur in underclays and the blue-gray shale fraction possibly represents an underclay. The green-shale fraction contained the fewest number of species and of particular significance was the almost exclusive restriction of specimens of Emphanisporites to this lithology. Also found in relative abundance in this fraction were Retusotriletes sp.1, and Forms 2 and 5.

CONCLUSIONS (1) The palynological assemblages recovered from this well are closely related to the florules of Devonian age reported by Russian investigators, and particularly with Zones X and XVII of NAUMOVA (1953), Middle Frasnian-Lower Givetian. (2) Devonian spore suites change composition and percentages very rapidly in response to minor ecological shifts.

P L A T E II 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 58

Forma 6, ×300. Forma 4, × 500. Lophozonotriletes sp, I, × 300. RhabdosporitesspA, × 300. Rhabdosporitessp.2, × 300. Retusotriletes sp. 1, ~ 500. Retusotriletes sp.3, ×300. ?Hystricosporites sp.l, × 75. Spinozonotriletes naumovii (KEDo), × 300. Hymenozonotriletes incisus, ×300. Rev. Palaeobotan. Palynol., 5 (1967) 51-61

PLATE 11

I 3

ACKNOWLEDGEMENT T h i s p a p e r is p u b l i s h e d with the p e r m i s s i o n o f the A r a b i a n A m e r i c a n Oil C o m p a n y a n d the C h e v r o n Oil C o m p a n y .

REFERENCES ALLEN, K. C., 1965. Lower and Middle Devonian spores of north and central Vestspitsbergen. Palaeontology, 8: 687-748. BALME,B.E., 1960. Upper Devonian (Frasnian) spores from the Carnarvon Basin, Western Australia. Palaeobotanist, 9(1962): 1-10. BALME, B. E. and HASSELL,C. W., 1962. Upper Devonian spores from the Canning Basin, Western Australia. Micropaleontology, 8: 1-28. CHmRIKOVA, E,, 1959. Spores of the Devonian and older deposits of Bashkir. In: Materials on palaeontology and stratigraphy of Devonian and older deposits of Bashkir. Dokl. Akad. Nauk S.S.S.R., 1959:3-116 (in Russian). HOFFME1STER,W. S., STAPLIN,F. L. and MALLOY,R. D. 1955. Mississippian plant spores from the Hardinsburg Formation of Illinois and Kentucky. J. Paleontol., 29: 372-99. KEDO, G. I., 1955. Spores of the Middle Devonian of the northeastern Byelorussian S.S.R. Tr. Inst. Geol. Nauk, Akad. Nauk Belorussk. S.S.R., Ser. Stratigraf. Paleontol.,pp.5-59 (in Russian). MARSHALL, A. E. and SMITH, A. H. V., 1964. Assemblages of miospores from some Upper Carboniferous coals and their associated sediments in the Yorkshire coalfield. Palaeontology, 7: 656-673. MCGREGOR, D. C., 1960. Devonian spores from Melville Island, Canadian Arctic Archipelago. Palaeontology, 3: 26-44. McGREGOR, D.C., 1961. Spores with proximal radial pattern from the Devonian of Canada. Geol. Surv. Can., Dept. Mines Tech. Surv., 76: 1-11. NAUMOVA, S. N., 1953. Spore and pollen assemblage from the Upper Devonian of the Russian platform and their stratigraphic significance. Tr. Inst. Geol. Nauk, Akad. Nauk S.S.S.R., Geol. Ser., 143(60): 1-204 (in Russian). NEVES, R., 1958. Upper Carboniferous plant spore assemblage from the Gastrioeeras subcrenatum horizon, North Staffordshire. Geol. Mag., 95: 1-19. NEVES, R., 1961. Namurian plant spores from the southern Pennines, England. Palaeontology, 4: 247-79. RICHARDSON, J. B., 1960. Spores from the Middle Old Red Sandstone of Cromarty, Scotland. Palaeontology, 3: 45-63. RICHARDSON, J. B., 1962. Spores with bifurcate processes from the Middle Old Red Sandstone of Scotland. Palaeontology, 5: 171-94. RICHARDSON, J. B., 1965. Middle Old Red Sandstone spore assemblages from the Orcadian Basin, northeast Scotland. Palaeontology, 7: 559-605. SMITH, A. H. V., 1964. Palaeoec01ogy of Carboniferous peats. In: A. E. M. NAIRN (Editor), Problems in Palaeoelimatology. lnterscience, London, pp.57-66. STAPLIN, F. L., 1960. Upper Mississippian plant spores from the Golata Formation, Alberta, Canada. Palaeontographiea, B, 107: 1-40. STAPL1N, F. L , 1961. Reef-controlled distribution of Devonian microplankton in Alberta. Palaeontology, 4: 392-424. SULLIVAN, H. J., 1962. Distribution of miospores through coals and shales of the Coal Measures sequence exposed in Wernddu clay pit, Caerphilly (South Wales). Quart. J. Geol. Soc. London, 118:353 73.

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TILINA-STANICHNIKOVA,M. S., 1964. Discovery of Devonian spores in deposits beneath the faunistically characterized Devonian of some regions of Second Baku. Tr. Vses. Nauchn. Issled. Geologorazved. Inst., Sb. Paleofitologicheskii, 239:47-52 (in Russian). VIGRAN, J., 1964. Spores from Devonian deposits, Mimerda|en, Spitzbergen. Norsk Polarinstitutts Skrifter, 132: 1-32.

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