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Some Aspects of Late Cambrian and Early Ordovician Acritarchs

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Some Aspects of Late Cambrian and Early Ordovician Acritarchs Some aspects of late Cambrian and early Ordovician acritarchs b y F. MARTIN A b s t r a c t . Late Cambrian and early Ordovician acritarch assemblages dated by means of trilobites and graptolites have been little studied; their stratigraphie usefulness for establishing detailed interregional correlations is consequently limited. Acritarchs from the Upper Cambrian, T remadoc Series, and Arenig Series of eastern Newfoundland are reviewed in relation to those of the Mediterranean region, western Europe, and North Africa, to which they bear a marked resemblance. F. Martin, Institut Royal des Sciences Naturelles de Belgique, Département de Paléontologie, Rue Vautier 31, B-1040 Brussels, Belgium. A c r i t a r c h s occur frequently in marine sediments established trilobite and graptolite zones has so far of the Upper Cambrian (Merioneth Series), Tre- limited the detailed stratigraphie usefulness of the madoc Series, and Arenig Series. The importance of group over a wide geographical area. This paper their diversity and abundance was indicated by reviews acritarch microfloras of late Cambrian, Downie (1973, fig. 1), while Cramer and Diez (1979) Tremadoc, and Arenig ages obtained by the author noted the publications devoted to their study; the from the Avalon Platform, eastern Newfoundland latter are few for the late Cambrian but numerous for (M artin in Dean and Martin 1978, in Martin and the early Ordovician. In general the lack of published Dean 1981) and compares them with data as com­ monographs dealing with the palynology of type piled in summer 1980 from many sources (text-fig. 1). sections and/or sediments dated with reference to the Thirty-eight taxa from the Avalon Platform (text- 37-39 16-18, t e x t - f i g . 1. Generalized map of localities from which late Cambrian, Tremadoc, and Arenig acritarchs listed in text-figs. 2 and 3 are recorded. Numbers are those printed in bold type on the right-hand side of text-fig. 3. [Pp. 29-40 la BASSETT, M. G. and DEAN, W. T. (eds.). The Cambrian-Ordovician boundary: sections, fossil distributions, and correlations. 227 pp. National Museum of Wales, Geological Series No. 3, Cardiff.] 30 F. MARTIN fig. 2) are selected here to illustrate the evolutionary Random Island and Bell Island is reviewed here. At succession of microfloras, but none of the steps in thisRandom Island, situated in Trinity Bay, the Elliott succession are designated as a formal biostratigraphic Cove Formation contains, according to Dean(in unit because of the lack of sufficient comparative Martin and Dean 1981), five of the six trilobite zones data. With the exception of Marrocanium simplex recognized in Scandinavia and the Anglo-Welsh Cramer, Kanes et al., 1974 and Tetraniveum areni­ area; in ascending order these are the Agnostus gum (Vavrdová) Vavrdová, 1976, both of which are pisiformis Zone, Olenus Zone, Parabolina spinulosa figured here (PI. 1), all the taxa have been discussed or Zone, Leptoplastus Zone, and Peltura Zone. The figured by Martin (in D ean and M artin 1978, in presence of the Acerocare Zone, the youngest zone of Martin and Dean 1981). the Upper Cambrian, has not been proved and it may As the above data are the only ones at present be that part of the overlying Clarenville Formation, available for the late Cambrian and early Ordovician containing Araiopleura beothuk Dean, 1970 and of eastern North America, the degree of reliability Conophrys sp., belongs to this level by analogy with of the age assignments for the relevant strata at corresponding strata in North Wales (A. W. A. EXPLANATION OF PLATE 1 Locality numbers with prefix GSC refer to the locality index of the Geological Survey of Canada, Ottawa, where specimens with numbers prefixed GSC are also housed. Specimen numbers with prefix IRScNB are in the Institut Royal des Sciences Naturelles de Belgique, Brussels. Details of certain localities are noted in the section on New Locality Data; others are listed in Martin and Dean (1981). Fig. 1. Tetraniveum arenigum (Vavrdová) Vavrdová, 1976. Lower Arenig, GSC loc. 94424, Bell Island, eastern New­ foundland. GSC 65675, x 700. Fig. 2. Marrocanium simplex Cramer, Kanes et al., 1974. Lower Arenig, GSC loc. 94424, Bell Island, eastern Newfound­ land. GSC 65676, x 1000. Fig. 3. Vogtlandia flosmaris (Deunff) Martin, 1978. Lower Arenig, LDR-15, Montagne Noire, Hérault, France. IRScNB b 1302, x 1000. Fig. 4. Dicrodiacrodium normale Burmann, 1968. Upper Arenig, FM-75-lc, Massif of Dave, Belgium. IRScNB bl303, x 960. Fig. 5. Aureotesta cte/vata Vavrdová, 1972. Lower Arenig, LDR-17, Montagne Noire, Hérault, France. IRScNB bl304, x 1000. Fig. 6. Striatotheca principalis Burmann, 1970. Lower Arenig, LDR-17, Montagne Noire, Hérault, France. IRScNB bl305, x 700. Fig. 7. Saharidia fragile (Downie) Combaz, 1967. Lower Tremadoc, GSC loc. 92999, Random Island, eastern New­ foundland. GSC 65677, x 500. Fig. 8. Baltisphaeridium crinitum Martin, 1978. Probably lower Arenig, GSC loc. 94419, Bell Island, eastern Newfoundland. GSC 65678, x 1000. Fig. 9. Pirea sp. Upper Arenig, FM-75-lc, Massif of Dave, Belgium. IRScNB bl306, x 700. Fig. 10. Vulcanisphaera africana Deunff, 1961. Probably Lower Arenig, GSC loc. 94419, Bell Island, eastern Newfound­ land. GSC 65679, x 1000. Fig. 11. Acanthodiacrodium sp. Probably Lower Arenig, GSC loc. 94419, Bell Island, eastern Newfoundland. GSC 65680, x 700. Fig. 12. Cymatiogalea cuvillieri (Deunff) Deunffet al., 1974. Lower Tremadoc, ARG-6, Salta Province, Argentina. IRScNB bl307, x 1000. Fig. 13. Acanthodiacrodium angustum (Downie) Combaz, 1967. ARG-6, Salta Province, Argentina. IRScNB bl308, x 1000. Fig. 14. Trunculumarium revinium (Vanguestaine) Loeblich and Tappan, 1976. Upper Cambrian, GSC loc. 92997, Random Island, eastern Newfoundland. GSC 65681, x 1000. Fig. 15. Timofeevia microretis Martin in Martin and Dean, 1981. Upper Cambrian, GSC loc. 92990, Random Island, eastern Newfoundland. GSC 57794, x 700. Fig. 16. Arbusculidium rommelaerei Martin in Martin and Dean, 1981. Upper Cambrian, GSC loc. 94435, Random Island, eastern Newfoundland. GSC 57819, x 1000. Fig. 17. Veryhachium dumontii Vanguestaine, 1973. Upper Cambrian, GSC loc. 92997, Random Island, eastern Newfoundland. GSC 65682, x 1000. Fig. 18. Cristallinium randomense Martin in Martin and Dean, 1981. Upper Cambrian, GSC loc. 92998, Random Island, eastern Newfoundland. GSC 57806, x 1000. Fig. 19. Vulcanisphaera turbata Martin in Martin and Dean, 1981. Upper Cambrian, GSC loc. 92989, Random Island, eastern Newfoundland. GSC 57764, x 1000. Fig. 20. Timofeevia lancarae (Cramer and Diez) Vanguestaine, 1978. Upper Cambrian, GSC loc. 92993, Random Island, eastern Newfoundland. GSC 57789, x 1000. PLA TE 1 MARTIN, Cambrian-Ordovician acritarchs F. MARTIN O l CL □ m ¡3 z l/l oí < LO MACROFOSSIL CG —I LU o O ZONES AND CD Z -—- -ri fe I C < é=; . O) Ui ZG OTHER FOSSILS OF < c= Z _ LU 00 e r < er LU STRATIGRAPHIC < s z: ae -2 ae LU CL 00 VALUE 1 < 00 CD oo ae oo :c "I 5 < u LU oo CD £ _j ■ä 6 LU 3 ae — 5 5 ;§ i . 8- Lj 'S oo o a o _i -c: Q ID b ae z: Z £: S s ^ s: lo < < < csi m CO O ' O T— CNJ CL LD Not exposed at surface LD Ogyginus terranovicus, DC Q Neseuretus vaningeni Z m < < in top D. extensus Zone _J i 00 CL LD CD Z O LU Appearance of acritarch a ae ¡ae ta x a 2 2 - 3 4 z cl < CD < —I oo Trace fossils Not exposed o u O CD a ( a t Bell Island < x LU Parabolina argentina Zone DC and 7 part of Acerocare Zone ? Acerocare Zone Q Z < Pel tura Zone __I 00 Leptoplastus Zone o a o z OU < o oc Parabolina spinulosaZone ae with Orusia lenticularis Olenus Zone Agnostus pisiformis Zone t e x t -f i g . 2. Vertical distribution o fselected late Cambrian and early Ordovician acritarchs in eastern Newfound­ land (not to scale). Taxa listed as Martin, in press are now published by Martin in Martin and Dean (1981). LATE CAMBRIAN-EARLY ORDOVICIAN ACRITARCHS Cd < c n ' < r - I 2: CO 2 Cd r~~ 0 $ : 0 ( ) Cd C d ZD o M ' n < a CD OS C X (Y CD < ZI cd Z Cd I a nr § q : l- í §S -' i d I < < a C d y I Cd < Cd 2_ I < y < ,L3 21 00 C d I Cd kta D7 _ j LU D3 C QJ -CD c: OC O. CD £ Q. CD D -Q -C I 00 t r CD a Q- CD < S oc X S 00 ,D) CD £ § 13 CD e 5 CD ^ S a - CD .=3 .Dj S Qj tai D3 <c .CD UJ ]S a ai .CD ’"S .5 'S 'S CD 2= I o c I Si «J ^D ;S 'S 'S "CD C CD h - o c: c ■ lo 00 .ÇO a -c a </i CD DJ I I O 3 CD -C; CD c: -C ~Cn Sj 1D b ■s -s Z $ S CQ l3> a I U) Lo I CD T— (VI < Osl Os) Cta c^irsicvjcvjcsiosimm Cl­ io LO occ a_ CD } LO CL < 00 CD O a < CL $ ! corresponding trilobite zone uncertain o p re sen t also in Middle oc Cambrian at Random Island 34 F. MARTIN Rushton 1979, and pers. comm, to W. T. Dean 1980). concerned but without necessarily being illustrated in The greater part of the Claren ville Formation, con­ the work quoted here. In order to avoid confusion taining the Parabolina argentina Zone as identified with possibly reworked material, the references cited by Dean (1976, p. 243, in M artin and D ean 1981), is do not refer to deposits younger than the Arenig considered to belong to the Lower Tremadoc by Series; consequently, taxa such as Frankea sart- comparison with the succession established in Argen­ bernardensis, Dicrodiacrodium normale, Striatotheca tina by Harrington and Leanza (1957), though it is quieta (as ‘S.
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