Geological Quartcrly, 2000, 44 (3): 3
17- 331
Acritarch assemblages from the Silurian Pomeranian Caledonides and their foreland
Monika J AC
HOWICZJachowicz M. (2000) - Acritarch assemblages from the Silurian Pomeranian Caledonides and their foreland. Grot. Quart., 44 (3):
311-331. Wal'SUlWL
Comprehensive palynological swdies of the Silurian rocks of Ihe Pomeranian Caledonides arc described, the first since Eisenack"
(1972) work, 250 clastic rock samples were analysed, all from deep boreholes. Three ofthcsc boreholes (~bork IG I, Gdansk IG I and Koodcrl.yna IG I) are located NB oflhe Tcisseyrc·Tomquist Zone (1TZ) and contain horizontal sliccessions oflhe westcrn, marginal part of the East European Craton. Other boreholes studied (DydGo,s7.cZ IG I, Klosnowo IG I and Stobno I) pencttllled folded Lower Palaeozoic $Cdimcnts, and lie SE oftheTrZ. Thc investigations included a completc Silurian profile from the Llandovery to the Pfidoli, which is documentcd in detail by graptoliles. Assoeiations of mieroflora (Aerilarcha. Prminophyceue, Sparlta) and microfauna (Chilz"nowa. Scolecodonta) varied in quality and quantity. There was considerable variability in the preservation and thermal maturity of the organic·waUed microfossils. Detailed investigations of the acritarehs are deseribed. 1 characteristic acritareh assemblages have been distinguished, and these arc eom:lated with tlK: graptolite bi07.0ncs. Llandovery rocks conl.i1in assemblagcs with DomlUlD,Ammonldium and Tylolopulla genenll. Wenlock deposits include Tylo/opaUa, IAplobrachlon and C)"IrIbruphDeridium. The Upper Ludlow deposits con·
tain well preserved assemblages Wilh Visbysphaera, Veryhachium, Onondugeffa and UiJnltfla, accompanied by Neoveryhachium cuntlinae, Gero" gracilis, and some DrJlandra.urum and Visbysphaera species generally eOlUidcrcd characteristic of Gondwana.
Throughout thc Silurian profile, individual specimens of typical On:Iovieian genera such as Acanlhodiaerodium, Frankea, Striaioiheca and Caryphidium occur. The acritarch assemblages overall ,how mixed characters, typical of both Oaltica and Gondwana.
Maniko Jaclrowicz, Upper Silesiun Branch. Polish Geologicallnstilute. Krolowrj Jadwig; I, P['.41·200 Srunowlec. Poland (received:
March 24. 2000; accrpttd: April 17, 2000).
Key words: Pomenllnia, Caledonides, Silurian. acritarch assemblages.
INTRODUCfION
Microscopic fossils called acritarchs have been known since the 19th century, but their nature and systematic position
remain controversial (Downie, 1984;Martin,
1993).
It is generally accepted that
these were
unicellular organ·isms, probably planktonic, with an extremely resistant organic wall. Some of
the researchers considerthat this group is polyphyletic, embracing algae,
cystsand probably also some plant spores (Downie,
1984;Martin,
1993). Taxonomically,acritarchs have been associated with diff
erent groups of algae.Many acritarchs also resemble, in tenns of their general struc-
turedinoflagellate cysts. Some acritarchs also seem related to the Prasinophyeeae.
The distinctive morphologies of ucritarchs and their ab
un-dance in marine deposits has led to their widespread application in biostratigraphical and pulacogeographica\ s
tudies. They were most widespread, abundant and diverse in the Cambrian
and Ordovician periods. After the Upper Devonian, they de·
clined considerably decreased and younger deposits contain only scarce representatives of this group (Downie, 1984; Mar·
tin, 1993).
Acritarchs are abundant and diverse in Silurian marine de- posits. They were first described by White (
1862)from lime·
stone in the New York State, USA. In 193
1, A.Eisenack discovered them in the Baltic area. Since then, they have been found in many parts of Europe, Africa and North and South America (Marti
n, 1989).In
1969, F.
Martin correlated acritarch associations from Si-lurian deposits in Belgium with the 16 graptolite biozones dis-
tinguished inlhat area. In
1963-1977, F.
H. Cramer with hisro-workers studied acritarch assemblages in Wenlock
to LowerDevonian deposits in northern Spain, and successfully applied
the results to effect correlations across Algeria, Tunisia, Florida, Turkey and the southern part of Arabia.
In Great Brit·ain, in the period
1959-1963, C.
Downie studied Silurianacritarchs from the Wenlock shales. Using these, he proposed a
'IS Monika lKhowiez
- ,
o , SO lOll , uo~. IFig.l. Location map oflhc boreholes
I _ Trans-European Suture Zone (TESZ) (supposed crou), 2 - jnv~li
gated boreholes
threefold division of the Wen10ck shales and determined typi·
cal ranges for Silurian genera such as Domasia and Deunffia.
Lister (1970), in his work on the Acanthomorphilae from Lud- low deposits, created typical Silurian genera such as Ammonidium, Di/atisphaera and Visbysphaera. Hill (1974) de- scribed Lower Silurian acritarchs from tbe Llandovery area and the Welsh Borderlands, distinguishing acritarch biozones in the Llandovery to Lower Wenlock interval. Doming (198Ib) es- tablished 7 acritarch biozones in British Wenlock and Ludlow deposits then, together with P. J. Hill (Hill and Doming, 1984), he distinguished 4 zones in the Llandovery. Le Hl:risse ( 1989), in his work on acritarchs and prasinophytes from Sweden, es.- tablished II acritarch zones. Local Silurian zonations have been proposed for Africa (Jardine el 01. , 1974). So far, these microfossils have not been systematically investigated in Aus- tralia, China, Antarctica and South America (Molyne ux et 01.,
1996).
There has been little detailed study of Silurian acritarchs in Poland. I n the 30s and 70s, acritarchs from the Baltic area were investigated by A. Eisenack, part of his material coming from boreholes in Poland. Recently, preliminary results ofinvestiga- tions on the Silurian acritarch associations of the Malopolska Block (lacbowicz et aI., 1987; Jachowicz. 1993, 1994) and Holy Cross Mountains (Stempien, 1990; Masiak, 1996, 1999) have been published.
For the last two years, the Polish Geological Institute has carried out detailed palynological investigations of Silurian rocks from deep boreholes in Western Pomerania (Fig.!). This paper represents the first general account of these investiga-
lions. In all, 250 samples from 6 boreholes were analysed Three of the boreholes studied (U;.bork IG I, GdaTisk IG I and Koscierzyna JG I) are located NE of the TfZ and contain hori- wntal strata of the western, marginal part of the East European Craton. Other samples came from the boreholes (Bydgos- .l:cz IG I, Klosnowo IG I and Stobno I) which penetrated folded Lower Palaeozoic sediments, SE of the TTZ.
An the samples were macerated using standard methods (Wood el 01., 1996). The samples were crushed into 5- 10 mm diameter particles and then were macerated using 36% hydro- chloric acid and
4()01ohydrofluoric acid . The material obtained was passed through a nylon sieve with a mesh 10 11m in diame- ter, and used to prepare standard microscopic slides. The
P~P?rations were subjected to planimetric microscope analYSIS LO transmitted light.
PALYNOLOGICAL RESULTS fROM SILURIAN BOREHOLE CORES FROM THE MARGINAL ZONE
OF THE EAST EUROPEAN CRATON
Most of the material studied came from the l4bork IG I, Gdansk IG I and Ko§cienyna IG I boreholes. Silurian strata reach considerable thicknesses in the profiles studied, from 1400 m in the Gdansk IG I borehole to 2300 m in the Koscierzyna IG I borehole. These rocks mainly comprise mudstones with graptolites of Llandovery to Pfidoli age (Tomczyk, 1 982; Tomczykowa, 1989). Sedimentation was continuous, and the thickness of individual Silurian stages in- creases upwards. Llandovery rocks are thin, from 23 m in the 4bork profile to 65.2 m in the KoScierzyna profile. The thick- ness of Wenlock deposits ranges from 131.3 m
(~borkIG I) to 323.5 m (Ko§cierzyna IG I). In the Upper Silurian, the sedi- mentation rate increased and Ludlow and Pl'idoli strata reach thicknesses from 1271.5 m (Gdansk IG I)
102053 m (Ll(bork IG 1). This distinctive thickness pattern is seen in the . three
pr~files investigated (Tomczyk, 1982, 1989). The stratIgraphy IS based on graptolites, and follows Tomczyk (1963, 1 982), Tomczykowa (1989), Urbanek and Teller ( 1997) as interpreted by Jaworowski (1999 - unpublished data). All
thesamples analysed are calibrated by graptolite biostratigraphy.
The analyses revealed the presence of rich organic-walled microfloras, belonging
totwo groups:
I. Acritarchs an autochthonous component of these deposits.
2. Microspores of terrestrial plants (Sporires), transported into the basin and representing allochthonous component.
There were also numerous Chitinozoa and scolecodonts, both autochthonous to this basin.
The analyses show that similar assoc iations and identica l successions ofmierotlora occur in the l.I(.bork IG 1, Gdansk I G
1 and Ko§cierzyna IG 1 boreholes.
Acritarchs have been found in most of the samples studied.
The only exception
isin Lower Ludlow (Gorstian) strata , in
which, despite detailed investigation, no specimens of . this
group have been found (fable 1). The samples here contalOed
only numerous amorphous organic fragments, fragmentary
Acrilarch IlUCmblagcs from the Silurian Pomeranian C.ledooidcs and their foreland
"9
chitinozoans and graptolites. 7 acritarch assemblages have been dislinguishcd.
ASSUMBLAGE I; LLANDQVI;RY - RHUDDANIAN. AERONIAN
Gdansk IG I (depth in metre: 3087.5, 3085.0) - ocuminoms, otovus.
K~ierzyna
IG
I(depth in metre: 4390.2, 4380.1, 4378.7) - ael/milla/Ils, convolmus.
4bork IG 1 (depth in metre: 3270.5, 3267.5, 3267.5)- cyphus, Iriongulotus.
These rocks contain very restricted associations of or- ganic-wailed microfossils. Simple spherical fonns (Leiosphaeridia) are typical. The material contains only li3g- mcnts of typical Silurian genera such as Diexollophasis and Oppilotala. Despite detailed investigations, no index acritarch genera known elsewhere have been detennined. This confonns to a general pattern. Acritarch associations obtained from Silu- rian strata elsewhere show the poorest generic and specific dif- ferentiation at this level (Kaljo et 01., 1995).
The material is poorly preservcd, (he specimens showing much damage to th e walls in the fonn of perforations and cracks. Thc specimens are dark or very dark in colour. There usually only a fcw specimcns per slidc.
ASSEMBLAGE 11: LLANDOVERY - 1"I!LYCHIAN
Gdansk IG 1 (depth in mctre: 3080.4,3075.5,3072. 1, 3068.6, 3066.5, 3063.3, 3060.2) - crispus, griestonensis, crenulata, spiralis.
Ko~cierzyna
IG
I(depth in mctre: 4365.5, 4360.4, 4355.1, 4349.7, 4340.3, 4344.8, 4329.3, 4329.3) - IIIrriculatus, grieslonel/sis, crellllla/a, spiralis.
~bork
IG I (depth in metre: 3263.5, 3261.0, 3255.0, 3253.0) - crisplls, gries/onensis. spiralis.
Telychian rocks contain acritarch assemblages differenti- ated in terms of both quality and quantity. These are quitc dif- ferent from the associations identified in Rhuddanian and Aeronian strata and also from associations determined in Wen- lock, Ludlow and Pfidoli sediments.
Thesamples studied con- tained many acritarchs- more thnn 1 00 specimcns per sl ide.
The more important species and genera identified here in- clude: Domasia lrispinosa, D. Iimaciform e, D. amphora, Salo- pidium granuiiferum. Evittia sanpelrensis. 1'ylolopallo caeiameniclltis, AmmonidiwlI Iis/eri,
A.microcladum.
Visby.fpltaera
lIIesOIland V. oligofilrcata. The material also contained numerous representatives of gencra characteristic of long expansion, nnmcly Leiosphaeridia, Diexallophasis, Veryhachium, Leio/usa, Micrhystridium, Multiplicisphaeri- dium, Ollomlagel/a and Oppilatala. Scarce specimens of Geron, Lcphodiacrodium pepino and Moyeria were idcntified, as well as individual speci mens of Neoverylwchillfll canllinae.
Acritarch associations of similar generic and specific com- position are known from the Lower Silurian of othcr areas. Thc Tclychilln was marked by many short-ranged species occurred.
This was the time onhe largest generic and specific differentia- tion of Silurian acritarchs. Acritarch assemblages obtained from Telychian sedimcnts of Pomerania urc very similar to
those described from Great Britain (Hill, 1 974), Norway (Smelror, 1987), Baltic area (Eisenack, 1965, 1968; Cramer
elal., 1 979; Le Herisse, 1989), Rllss ia (Sheshegova, 1971 , 1975, 1984; Kirjanov, 1978), Belgium (Martin, 1969, 1974), Czech Republic (Dufka and Pacltova, 1988; Dufka, 1990) and North Amcrica (Cramer and Diez, 1972). Most of the fonns docu- mented in the profiles studied are also known from North Af- rica (Le HCrisse, 1992; Keegan et 01., (990) and South America (Rubinstein, (996).
Thc preservation of the specimens is not very good. There are many damaged fonns, which makes taxonomic identifica- tion difficult. The damage consists of irregular perforations, cracks and damagc to sculpture elements. Microflora in the
CriSPIiS
Biozone is especially badly preservcd. Microfossils here are dark brown or sometimes even black in colour.
Microfossils in the gries/ollellsis and spiralis Biozones arc better preserved, though showing brown and dark brown ther- mal ahemtion colours (P I. I).
ASSEMBu\GE III; WENLOCK - SHEINWOQDlAN
Gdansk fG
I(depth in metre: 3035.7, 3032.6) - jlexilis.
Ko~cierzyna
IG
I(dcpth in metre : 4312.0, 4308.8, 4305.6, 4295.3, 4275.2) - amefllliarius,jlexilis, ellesae.
Lj(bork IG I (depth in metre: 3247.0, 3245.0, 3240.5, 3238.0, 3228.0, 3221.0, 32 15.0, 3209.0, 3205.0. 3201.5, 3195.0, 3 1 90.0, 3 185.0, 31 80.0, 3 175.0) - celltrifuglls.
mllrchisoni, riccartonensis, ontenufarius, jlexilis, rigidlls, ellesae.
Despite detailed investigations, only poorly differentiated microfossil associations were encountered. The speci mens are poorly preserved and there were only severa l specimens per slidc. Most genera are long-ranging, such as Leiosphaeridia, Diexallophasis, Micrhystridium, Velyhachium and Leiofllsa.
The preservation of thc specimens wus not good enough to can)' out specific detennination.
The genus Leiosphaeridia is dominant comprising 90"10 of the identified specimens. Specimens range from 10-200 J.1m in diameter. Other genera are rare. The microfossils are dark brown in colour.
ASSEMBLAGE IV; WUNLOCK - IIOMURIAN
Gdansk IG I (depth in metre: 2979.2,2924.3)-lulldgreni.
spifloSlls.
Koscicrzyna IG I (depth in metre: 4254.7, 4236.9, 4 1 63.5, 4140.7, 4060.5) - /IIIIdgreni, lIossa. ludensis, spinosus.
t...c:;bork f G I (depth in metre: 3170.0, 3165.0, 3160.0, 3 155.0, 31 50.0, 3138.5, 3115.0, 31 10.0, 3085.0, 3080.0, 3075.0,3070.0, 3065.0)-lundgrelli. ludellsis. spinoslls.
Acritarchs are numerous at this level, with 100-150 speci- mens p<:r slide. l..eiosphaeridia is common, and accompanied by Moyeria. which locally comprises 50010 of the assemblage.
These are accompanied by Diexallophasis, Tylotopolla and
?Cymbosphaeridilllll.
Despite its low gcneric and specific diversity the Homerian
assemblage is distinctive, especially as regards the abundance
o f Moye";o. This genus, generally classified as an acritarc h
320
Monih
JachowiczTa b I e I Stn tillrllphiclIll'1Inge oflhe Investigated tuons
SilLirian
Llandovery Wenlock Ludlow
Aerilan;h.
•
cj t • . ~ •
c• :g
~ ••
c ·c• ]
~ ~~
e
~ e
~, •
.~ c c ~~
<
X 0,
~ ~
~
1 2 l 4 S 6 7 8
,
uio.sphaeridia sp.
Diuallophruls dentleu/ala DI~lIophfUts 5p.
Moyen"a Cllbolti Micrhystridium .rIel/alum
Yuyhachium lalrdjj Yflrylrochlum trlsplnosum Dictyolldirlm sp.
Oppilatafa 'p.
Domasia lrispino.ra Domruia limaci/omre
Domasia omphOTtJ Sofopidlum granull/tnml Sa[opldium sp. I
Salopidiunr sp. 2 Anrmonidium lisltr/
Ammonldium mir:rocfodum
Domasia e/ong%
Lophodiacrodium pepino Evil/ia sOllpetrouis Yisbysphoua muon Yisbysphoera oJigo/urcata Ty/otoPQl/o c:ellon/ens/s
Tylotopalla coe/rmlenlau/Is Gero" sp. I
OnOIUJogelfa QJ)'I1Imelrlca
Tunisplraeridium minI/tum Muftiplicisphoflridium Sp.
Tyfotopalla sp.
Moyerio sp.
Nrroveryhochlum conn'nof!
AeriLarch assemblages from the Silurian Pomeranilln Caledonides lind their foreland 321
I 2 3
eymbosphaerldillm sp. 1 Dilolisphaera sp.
TyIOlopalla wenlock/a EapoikiloJusa strlalifera Elektoriskos aurora Leol/iello carminae /lisbysphaera gOllondica /lisbysphoera mfcrospillOSO /lisbysphaera dilalispillosa /lisbyspfwero e/'/'Q/ica Visbysphoera b/'t!vifurcatu Visbysphaera janlinae /lishyspJwero sp. 1 Dt!jlandfas/nllll millepiedii Eupoiki/oJllsa cantabrico Geron KlIeriflerlis Gerol/ gracilis Leplobrachion sp.
Pterospernlelfa sp.
Visbysphaera sp. 2 Dictyolidillm sp. 2 Hemibaltispbaeridium deriosmllerlosi
group, is considered by some authors to represent the oldest freshwater Protozoa, due to its similarity to modem euglenoids (Gray and Boucot, 1 989).
The preservation of the microfossils is poor. Only ITag- ments of Diexa/{ophasis and Cymbosphaeridium are pre- served, so their detennmation is approximate. The specimens are brown and dark brown (PI. II).
ASSEMBLAGE V; LUDLOW - LOWER LUDFORDIAN
Gdansk IG I (depth in metre: 2795.5, 2791.1, 2787.2, 273 1.0, 2722.0, 2667.2, 2584.0) - ?/eintwardillellSis, praecornulus, conllltus.
Koscierzyna IG 1 (depth in metre: 3214.9) - /eintwardinens is.
4bork IG 1 (depth in metre: 2825.0, 2775.0, 2755.0, 2725 . 0, 2705.0, 2675.0, 2645 .0, 2625.0, 2570.0, 2510.0, 2410.0, 2400.0, 2320.0, 23 15.0, 2270.0, 2200.0, 2 125.0,
4
Continuation of Table 1
5 6 7 8
,
r-- I - I -
- r---
-
-
2095.0,2044.0, 1963.3, 1934.0, 1882.4) -/eintwardinensis, praecornu/us. cornutus. auricula/us, inexpectatus. kozlows/di.
Acritarchs are abundant in rocks of this age (300 speci mens per slide). The most abundant forms include Dilatisphaera, Cymbosphaeridiwn, Ty/otopalla, Diexalfophasis den/ieu/ala, Leiofusa. Eupaikilofusa. Elektoriskos and Leiosphaeridia.
Genera such as Micrhystridium, Geron and TUllisphaeridium were also determined. In terms of quantity, Cymbosphaeridium is the most nwnerous genus and may locall y reach 60-70% of the total assemblage. The taxon Cymbosphaeridium sp. I is short-ranged.
The acritarchs are quite well preserved and largely undam- aged. The specimens are brown and dark brown (PI. 1lI).
ASSEMBLAGE VI; LUDLOW - UPPER LUDFORDIAN
Gdansk IG 1 (depth in metre: 1995.8) - ?spinel/s.
PLATE!
(~/
8;r:-- ! \
l e i
9r \ J ' I r
10
11
-
17
Llandovery (Tclycilian) acrilarch usemblage, lC 800; J. Domruia lrispillosa Downie, 1960. 2. DonICuio IimQcifDml~ (Stockroam ct Willicrc) Cramer, 1970.1. Tylolopolla cuelamenicufis Locblich Jr., 1970. 4, I. Ammon/dlum /lsleriSmc:lror, 1981. S, 6. Ammon/dlum 'p. 7. 14. El>ittia sanpdrerui.T(Cramcr) Lister, 1910.9, 12. Domosia omphorrl Martin, 1969. 10, J 1. Do/flas/a trisp/lltuQ Downie, 1960. 13. TylolopDllo cf. deerlijfdono (Martin) Martin, 1978. J 5, II, Sa/opld,'wrr gronufi/erum (Downie) Doming, 1981. 16, 17. Salopfdium 'p. /9. Oppll%/Qjrofldis (Cramer cl Di~) Doming. 1981. 20, 13. Yisbysphoua ofigo./uralltJ (Eisenack) Lister, 1970. 21. Ammonldillm mlcroc;lodum (Downie) Lister, 1970. 22. Dlual/ophasis sp. J~, U - <k:pth 3263.S m; 9-13, 15-11 - depth 32SS.0m; l."bork 10 I borehole
PLATE II
3
,
.~;,(
.;.
•
.
;. -
, •
1. ...
~" • · ,
'.,.. '.
-··r •
( --V
~I~_~... ,'..
~-,;"~,,
, · . ,.-
;
19
Wenlock (Horm:rian) acritarch assemblage, x 800; I, 1. Mo~ri(l sp. J, 4, S. Mo~"'o coborti (Cramer) Miller et Eames. 1982. 6, 10, 11, 12, 11.
Micrhystridium sp. 7. AmbitisporilQ $po I. Tylotopollo sp. 9. Cylllbosplloflridimn sp. 1.14, IS, 16, 17. Vubysphoflrtl mir:rQSpinoso(Ei5en~ck) Listcr, 1970.
18,19,10. Lei08plluflridio sp.lX:pth 4140.7 m, Kokica)'OD 10 I borehole
1
2
8
•
l
"/'
" j '
'~, ,,~,
3
- ,
11
~ .:;. }' ~~~ : , ~'~ ;- ' 1.'1- " - . >:r- ,
~ :.~"I,,~ . ' . ).;
I~ J . ,~l''!<.. :
'f'"
.~,y"
7 " " .'
• • i ' •
"
.
, ~'
~ t~ ,/
t'f'&,~ . 13'
PLATE III
o
9
Ludlow (lower Ludfordian) acritarch assemblage, It 800; 1. DUarisph(lero wff/lcreafl Martin, 1966; 264S.0 m. 2, 3, S, 6. CymbosphQerldilim sp.; 2795.5 m.
4. Leia/usa 'p.; 2195.S m. 7. Plerl»~nnQpsll 'P.; 2320.0 m. 8. Pm:ll/iUphoera sflphrospillola Lister, 1970; 2270.0 m. 9. £itdCloriskosaUFora Locbtieh Jr.
1910; 2270.0 m. 10. TylotopallQ _"lock/a Doming, 1981; 2320.0 m. 11. Diualloplrosis sp.; 2320.0 m. 12, /J. Diuallophasis denticulo/Q (Stoekmans and Willicrc) l.ocblich Jr., 1970; 2320.0 m. 14. Elipoikifo/usQ stn"Qll/ua (en.ma) Cramer, 1970; 2795.S m. 1-6, 14 - Gdansk 10 I borebolc; 7-11 - lA;bork 10 I boreholo
. .
•-
• .;Y, ~ . ... " j
.,-
\f ,
I
12
,
til..
~
• ,
/ 7
~
6
1. - . .... . ~~. .
I I
\
/ ,,'-
"
i '
"
PLATE IV
,
t •
14
17
Ludlow (upper Ludfotdian) acriweh assemblaae, x 800; I. Neollf!ryhachium cannimle(Cramcr) Cramer, 1970; 1730.1 m. 2. Pterospermopsis 'p.; 1730.1 m. J, J, /0,12. Multiplicuphaeridjum bolli/um Cramer, 1970: j - 1730.0 m. 9, /0, 12 - 16;7 . .5-16.59.7 m."'. Yisbysphaerojardillae (Cramct, 1970) Le' H~. 1983; 1730.0 m. S. YlJbl'phaua micrwpino.ra (Eiscnack) Li$tcr, 1970; 1618.3 m. 6. ?~plabrochjon sp.; 1618.3 m. 7, U. Yeryhachium
IrispjllOlllm (Eiscn.ck) Stockman, c:t Willicre, 1962: 7- 1657.5--1659 m, U - 1576.1-15&3.8 m. I. L6io/usIJ bollduilllJe Cramer. 1964; 1612.3 m. 11. StrlalOllleclJ sp .. Ordovician taxon; 1657.5--1659.7 m. 13, 16. Leoniella cIJrwrillae Cramer, 1964: Jj - 1612.3 m, J6 - 16.52.5--16.59.7 m. IS. Geroll guer/llenu Cramer; IS76.1-IS83.8 m. 17. TUllisphaeridillm lenlacllii/enlm (Merlin) Cramer, ] 970; 1612.3 m. Lqbork IG I borehole
- . 15
,
1
... _ = )
13
I
\.1
,.
. .
PLATE V
".
20
Ludlow (upper Ludrordian) acritarch IlSsombJagc, :.: 800; I, 2, J Veryhachium sp.: I - 1531.3 m, 2 - 1472.6 m, J - 1338.3 m. 4. Neuvtryhochiu", ctlrtfll'lClfl (Cramer) Cramer, 1970; 1338.5 m. 5. Veryhachium reduclllnI (Biscnack) Stockmans ct Willicre, 1962: 1338.5 m. 6. NeoVl!ry/JQchium corminufl:
varianl with .5 processes (Cramer) Cnllncr, 1970; 1338.S m. 7, 8. Visbysplroertl microspim}Sa (Eiscnack) Lisler, 1970: 1- 1419.9 m, 8 - 13]8.S m. Y. LAlruphotridia sp.; 1531.9 m. 10, I J. Multiplicisphaeridium boninml CralllCT, 1910; 10 - 1 )385
m,
1 J -1
419.9 m. /1. OnondQgella asymlNfllrlca;1472.6 m. IJ. Veryhachium Irup/nosu", (Eiscnac:k) Stoekmans eI wmicrc. ]962: 1531.3 m. U. Bo/lisphof!ridiufH sp.; 1338.5 m. 15, /6.
lIemiboltisphouosum dedosmuertosl (CrartK:r) Cramer, 1910: 1472.6 m. 11, II. Visbpphaero pirifmJ (Eiscnack) Lc H~risst. 1989; 1338.5 m. 19.
lAlofiun 'p.; 1531.3 m. 20. EupoikiloJusa call/obricn (Cramer) Cnmtr, 1970; 133&.5 m. Lc;:bork 10 I borehole
Acritarch assemblages from Ihe Silurian l'()IJI(I'1Inian Caledonides and their fOfl:land 327
Ko~cicrzyna
IG I (depth in mctre: 2432.8, 2358.0, 2301.7, 2373.3)
-?spinells + ?protospineus + ?Iebanensis +
?balticus.
~bork
IG 1 (depth in metre: 1812.0, 1810.1, 1768.3, 1730.1, 1679.8, 1653.0, 1612.3, 1584.3, 1578.0, 1531.3,
1472.6,1419.9, 1338.3, 1283.6,
1257.1,1242.3, 1207.7, 11 83.3, 1166.8, 1135.0, 11 25.5,
1121.0,
1102.9) -balticus, acer, ?protospineus, regllans
=hemsiensis
=?spineus.
Very rich and wcll preserved acritarch associations occur (over 1000 specimcns per slide). Apart from numerous long·lived genera and species such as Leiosphaeridia, Veryltacllilwllairdii, V. trispilloslllll,
V.reductum and Leio/lIsa, many associations contain also taxa which occur for the first time in the profiles. These include Leaniella carminae, Visbysphaera jaroinae, Geron guerillerus, G. gracilis, Dejlalldrostl1lm mi/fepiedii, Tllnisphaeridium telllaculiferum and Leio/llsa bollderillae. Associations dominated by Neoveryhachillm carminae (over 200 specimens per s lide) are chardcteristic. This is the fll'St occurrence of this species in Po-- land. So far, assemblages containing it were considered charnc·
teristic of Silurian strata on Gondwana and in peri·Gondwana regions (western Wld central Africa, northern France and lbe-- rian Peninsula; Cramer and Diez, 1972). Acritarch preserva·
tion and morphology is shown in Plates IV- V.
ASSEMBLAGE VII; pjUooLi
Gdansk
IGI (depth in mctre: 1800.5, 1 654.0) - prima- incerta, 1poraliltimlls + 111ltil/llls.
Koscierzyna IG
I(depth in mctre: 2 103.0) -Iochkovel/sis + ultimliS + ?paraultimus.
Ll(bork
IGJ (depth in metre: 1046.3)
-prima- il/certa,
?parau/limlls + ?ultiIllIlS.
Abundant and very well preserved organic·walled microfossils occur in
Pridolian strata (morc than1000 speci- mens per slide). Tasmallites lind Cymatiosphaera lire domi·
nant, locally reuching 80% of the assemblages . These are associated with conunon Leiosphaeridia .md also:
Veryhachium (rispil1osum, Leolliella carminae, Ollondagella sp., Leio/usa, Visbysphaera microspil1osa, Dejlandrastnml, Micrhystridium sp., Geron gracilis, TWlIsphaeridillm parvWII, Moyeria cabatti and Pterospermella sp. Most ac ritarchs deter·
mined
here occur also in Ludfordian sediments. The associa- tions found in the Pfidoli differ from these in thc greater abundance of Tasmollires and Cymatiosphaera and also in fewer Visbysphaero and Hemibaltisphaen· dium. As in the Ludfordian rocks, preservation is very good. The specimens do not show any damage, even on delicate clements of the sculp- ture. They show little thennal alteration, being light ycllow or orange in colour.
PALYNOLOGICAL RESULTS FROM THE BO REHOLES OF THE TESZ
The Silurian rocks in the Bydgoszcz fG
I, KJosnowo IG1 and Stobno I boreholes did not have
IIwell-defined stratigra- phy. Acritarchs wcre anulysed to try to provide one.
22 samples were investigated, from the following bore·
holes:
-
Bydgoszcz IG I (depth in metre: 5603.0, 5602.6, 5602.0,5601.5,5600.9,5600.5, 5600.0);
-
Klosnowo
IG
I (depth in metre: 2460.4, 2460.0, 2454.2,2453.3
,2452.6,2452.6);
-
Stobno
I(depth in metre: 2525.9, 2525.0, 2524.0, 2522.3,252
1.3,2560.8,25 19.7,2490.5).
Dctenninable acritarchs werc found in the samples from the Klosnowo I G
I and Stobno I boreholes. Despite derailed inves·tigation, no stratigraphically useful acritarchs were recovered from the BydgoS1.cz 1
0 Iborehole.
STOBNO I
The most abundant organic-walled microf ossils were deter·
mined from the Stobno
Iborehole, with over 300 specimens per slide. The association chiefly comprised: Leoniella carminae. Visbysphaera microspinosa, Hemibaltisphaeridium dedosnlllertosi, Veryhachium lairdii, Tllnisphaeridilllnparvum and Geron gracilis.
Thesamples also contained nwnerous specimens of Leiosphaeridia, Veryhachium , Onandagella, Diexallophasis and Lelo/usa. The specimens are well pre·
served Wld show little damage. Their orange and ligbt brown colour indicates that the temperature did not exceed lOO-J20"C. The similar associations were found in the upper Ludford ian sediments of the Gdansk IG I,
Ko~ierzyna fG1 and lA<bork IG
Iboreholes. These associations show comperable prcscrvation and also a similar intensity of thermal metamorphism.
KLOSNOWO IG I
l'lere,
there were wcll preserved acritarchs with over 100 specimens per s
lide.The associations are dominated by Leiosphaeridia, which is accompanied by more diagnostic taxa suc
h asTylotapalla , LeioJilsa and Micrhystridium. Similar as·
sociations arc known from Wenlock strata in other areas (Doming, 1 981b;
Le Herisse, 1989).Acritarch associations of similar specific composition have not yet been determined in Si lurian rocks from the Gdansk IG I,
Ko~ierzynaIG I and
~bork
IG I boreholes.
The acritarchs are well preserved, showing little damage or change in co lour: light ycllow and yellow colours indicate tem·
peratures be l ow 80"C. The
lowestthennal maturity was en·
countered in the K1osnowo IG 1 borehole.
PALAEOECOLOGY
Acritarchs occur mostly in marine sediments, having been
detennined in shale, siltstone, claystone and in
limestone. Theirwide geographical expansion and size suggests a planktonic
mode oflife. Their morphology, chemical composition, and the
occurrence of a di stinctive opening
inmany taxa suggest that
many forms belonging to this group represent cysts analogous
to those of the dinoflagellates. Compurison with modem eco--
systems suggests that they were phytoplankton in the photic
328
Moniks. Jachowicz
zone ofa basin, producing large amounts of organic matter and oxygen (Tappan, 1980). Acritarch morphology
is commonlyinterpreted as an adaptation to open sea conditions and to maximise exploitation of the photic zone. Their processes helped the organisms to maintain their position in the water eol- umn.
The growth of phytoplankton in the basin depends on many factors, such as temperature, salinity, inten sity oflight penetra- tion and turbu lence.
Quantitative and qualitative studies h ave shown a relation- ship to sedimentary facies. Acritarchs, similarly to dinocysts, are most diverse in offshore shelfdeposits, diversity decreasing in deep water (Wall et 01., 1977). Staplin (196 1 ) was the first to associate acritarch associations with depth, while Doming (1981a) considered that it
is possible to determine distance tothe s
hore anddepth using acritarchs.
He distinguishedthree acritarch associations in the Silurian of southern Wales related to increasing depth and distance from shorc. The offshore asso- ciation is oflow diversity (
IS-SO species) and is dominated by small spherical fonns with a smooth sw"face and short pre- cesses. The second acritarch association, associated with a deeper, open shelf, shows high diversity (10-90 species in a sample), without any dominant taxon. The third, deep water, association is of low diversity (2- S species in a sample), and
representatives of the Sphaeromorphitae subgroup arc domi- nant.They have thick walls which, according to some authors, may suggest high energy conditions (Martin,
1993).The Silurian profiles studied here show a distinctive tempo- ral differentiation of tile acritarch associations. The lowest Silu- rian (Rhuddanian and Aeronian) associations are poorly diversified with a predominance of si
mple sphericalLeiosphaeridia with thick walls, accompanied by scarce spinose acritarc
hs.11lis composition suggests a deep-water setti
ng.The rich and diverse associations of the Telychian, ludfordian and Pi'idoli rocks are typical for an offshore shelf setting.
PALAEOGEOGRAPHY
The Proterozoic to Devonian interval is optimal for acritarchs. Acritarch associations show a mostly cosmopolitan nature, facilitating long-range correlation. But, the limited spa- tial range of some
taxahas led to them being used in Lower Palaeozoic palaeogeographic reconstructions (Vavrdova,
1974; Cramer and Diez,
1972).M. Vavrdova was the first to observe in 1974 distinctive geographical differentiation of acritarch associations in the Lower Ordovician strata of Europe. She suggested, llSing dif- ferences at a generic
level,the existence of two provinces:
Mediterranean and Baltic.
Cramer (1970) and Cramer and Die-I; (1972) revealed fur- ther distinctive geographical differentiation of acritarch associ- ations in Silurian sediments. They assumed that each organism had its own maximal, optimal and minimal "living
tempera-lure". They
used acritarch distribution data to identifY subequatorial zones, asswning control mainly by the climate.
The palaeogeographic implications of Lower Palaeozoic acritarchs has becn further discussed (Nautiyal,
1976,
1977;Hill
and Molyneux,
1988; Colbath,
1990) and earlier models havebeen revised (Le
Herisse, 1989;Le Herisse and Gourvennec, 1995). Lateral variations in acritarch associations of the same age are increasingly being interpreted as facies preferences of individual taxa.
These studies of
Pomeranian acritarchs have revealed newdistributional data. Most of the fonns detennined here have a cosmopolitan nature, ranging from the Baltic area to northern Africa and South America. These are accompanied by taxa so far considered to have a more limited occurrence. For cxample,
the species asOOlnasia amphora, Tylotopalla pyramidalis and Dilalisphaera williereae. identified in this study, were earlier known only from low palaeolatitudes. Numerous specimens of Geron graCilis, Deflandrastnun millepiedii, Neoveryhachillm canninae, Hemibaltisphaeridillm, some Vishysphaera species have also been documented, and these were previously known only from high palaeolatitudes. Surprisingly, no specimens of typical Baltic genera such as Hoegklintia or Pulvino- sphaeridillm
have been detennined in the samples studied Thismay be due to gaps in sampling of thesc thick Silurian successions.
The Silurian deposits of Pomerania also contain typical Lower Ordovician taxa such as AcanthodiacrodiwlI, Frankea, Striato/heea, Baitisphaeroslllll and Coryphidillm on secondary deposit. These are characteristic ofthe Mediterranean Province as defined by Vavrdova (1974). They are well preserved, sug- gesting short transport.
PATTERNS OF THERMAL ALTERATION
The Pomeranian acritarch assemblages show clear
differ~ences in preservation and thennal alteration.
It is well established that organic substances change their colour with progressive thennal transfonnation from light yellow to or- ange, brown and black.
Acritarchs recovered from
the CrisPl1SBiozone of the Llandovery show the greatest thennal alteration. Their dark brown to black colour suggests the temperatures of about 200"C. Acritarchs from Llandovery, Wenlock and lower
Ludfordian deposits show brownto dark brown colours sug- gesting temperatures of about
ISO-I80"C.A distinctive change in microfossil preservation occurs in upper Ludfordian strata, appearing at the level of the baltiells Biozone. Acritarchs here arc light brown and orange in colour, suggesting tempcrahlres of about I 00-IS0"C
. l1lis intensity ofthennal alteration continues to the top of the Silurian profiles srudied.
These changes ofthennal alteration intensity, observed in
the Gdansk JGI, Kokicrzyna 10 1 and
L~bork1G I boreholes,
arc probably associated with changes of subsidence rate during
sedimentation, or with the multi-stage heating.
Aeritan:h assemblages from the Silurian Pomeranian CIIlcdonidcs and their ron:land 329
OTHER MICROFOSSILS
Most of the samples studied contained numerous or·
gllnic-walled microfossils other than acritarchs. These include Chitillozoa, scolecodonts and terrestrial plant·spores.
Prasinophytes are common, especially in Upper Silurian de-- posits. Occasional samples from the Te1ychian contain also large muellerisphaerid fragments.
Among these, chitinozoans are the mOSI numerous and have been found in mostofthe graptolite horizons investigaled.
The associations show considerable generic diversity, and specimens occur separately or joined in chains. Chitinozoans occurred also in those samples which otherwise contained only scattercd organic matter and graptolite fragments, indicating a lower sens itivity
10facies control than the acritarchs.
Terrestrial miospores are represented mainly by Ambitisporites, found in llandovery, Wenlock and Ludfordian deposits. This genus represents simple foons of the Triletes·Azonales group, stratigrap hically the earliesl miospore group. Single specimens of Zollotriletes have been detennincd in the Ludfordian. The miospores com prise only about 5% of most samples studied. The terrestrial plant mio:."POres, trans.
potted into the basin by aeolian or fluvial action, represent an allochthonous element in these marine rocks. The miospore ex.ines are usually well preserved and do not show the kind of mechanica l damage caused by long transport. Thus, the shore·
line was probab ly not far away.
In occasional sampl es ofTelychian rock, distinctive spiny fo nns with dimensions from 100to 600}.Ull diamelerhave been detennined. These represent muellerisphaerid fragments.
These microfossils were first described from Silurian strata in Ocnnany by Sannemann (1955), included them in the acri tarch genus Hysfn'chosphaen'dium, despite their large size. The group Muellerisphaeridia was defined by Kozur in 1984. Simi·
lar microfossils are also referred to the mazuelloids, a tenn pro-- posed by Aldridge and Armstrong in 1 981. These latter marine fossils usually occur as isolated spines which represent sculp·
tural elements of much larger specimens; complete spheres are fOWld only very rare ly. Muellerisphaericls (- mazuelloids) have been recorded from Ordovician to Devonian pelagic deposits in Europe, Asia, North America and Australia (priewaldcr, 1987;
Hlisken and Eiserhardt, 19%).
CONCLUSIONS
PIIlynological investigations of Silurian deposits from Pomerania indicate the following:
I. In most of the samples studied from the Odansk 10 1, KoScienyna 10 I, Klosnowo 10 I, Ll;.bork 10 I and Stobno I boreholes, there are determinable associations of or·
ganic--walled microfossils which represent
botha microflora (acritarchs, prasinophites and microspores) and a microfauna (ChitinOU)(1 and Scofecodonta).
2. Lower Silurian (Llandovery and Wenlock) associations are typical of deep wllter palaeoenvironments showing low
tax·onomic diversity. Telychian and Upper Silurian (Ludfordian, Pfidoli) assemblages are rich and d iverse at both generic and specific levels, and so typical of offshore shelf palaeo-- environments.
3. Assemblages from Llandovery, Wenlock and Lower Ludlow strata show
poorpreservation and high levels of ther·
mal alteration. Assemblages from upper Ludfordian deposits are very well preserved and show much lower levels of thermal alteration.
4.7 stratigraphically controlled acritarch assemblages have been recogn ised and these have been correlated with the graptolite biostratigraphy.
5. Associations characterised by Domasia, Ammonidium and Tyfotopaffa have been recognised in Llandovery strata; and by Tylotopalfa, Leptobrachion and Cymbosphaen"dium in Wenlock deposits is Upper Ludlow rocks contain ricb and very well preserved associations characterised by Visbysphaera, Veryhachillm , Onondagefla and LeonieJ/a; these are accompa·
nied by Neoveryhachium canninae, Geron gracilis and Deflandrastntm, previously only described from the Baltic area.
6. Occasional specimens of typical Lower Ordovician gen·
ern such as Acanthodiacrodjl/nI, Frallkea, Striatatheea and Caryphidillm occur throughout, as reworked foss ils. These are of MeditemlOean Province affinity (Vavrdova, 1 974).
7. Acritarch associations from the Silurian deposits of west·
em Pomerania show genera and species known both from Baltica and Gondwana. The infonnation to date is not sufficient to give an unambiguous determination of palaeogeographical position.
Palynological material obtained from Silurian strata of the East European Craton and TESZ is cosmopolitan in nature.
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