STIG M . BERG STRO M N G U -B U L L 4 3 2,1 9 9 7 - PAGE 5 9

Conodonts of Laurentian faunal affinities from theMiddle Ordovician Svartscetra limestone in theTrondheim Region, Central Norwegian Caledonides

STIG M. BERGSTROM

Bergstr6m, S. M. 1997: Con od onts of Laurent ian affin it ies from th e Middle Ordovician Svartseetra limeston e in th eTrond heim region, Cent ral Norwegian Caledoni des.Norg es geo logiske un dersekelse Bulletin 432, S9-69.

Samples from a 122-me te r t hick lim esto ne succession at Svartszetra, about 13 km east of Meldal in the TrondheimRegi on, west- centra l Norway,yielded more than 100 conodo nt elements representi ng about a dozen multielementspecies. All are con specific wi th, or close ly similar to, taxa present in th e upper Middl e Ordovician of th e North

American Midco nti nent,a nd a biostrat ig raphic assessment indicates th at the Svartseet ra lim eston e is coeva l w ith t heShermanian Substage of the Chatfi eld ian Stage in th e uppermo st Middle Ordovician of North America. In term s ofNorth American and At lant ic conodo nt zones, th is interval is in th e Belod ina confluens and lowermost par t of th eAmorphog na thus superbus zones,respect ively. The faun a differs str ikingly from most ot her coeval Baltoscand ian eo­nodont faunas, th e only known exceptions being those of th e Mjesa Limestone in the Oslo Region and th eVasalemma Formati on in Estonia w hich exhibi t t he same Laurent ian faunal aff init ies. These un it s, as well as theKalstad Limestone of th e Meldal area, are interpr eted to represent the same brief period of shallow-wate r,subt ropi­cal-t ropical. bahamitic limesto ne deposit ion wi th faunas of Laurentian aspect. Because many conodonts apparent lycould cross oceanic areas,conodonts alon e cannot be used to prove th e hypothesis t hat th e Svartseetra lim eston e,a swe ll as th e Kalstad Limeston e, were origi nally deposited offshor e from Laurentia rather than Baltic a.

Stig M.Berqstrom, Depa rtme nt ofGeological Sciences, The Ohio Sta te University, Columb us, Ohio 43210, USA.

IntroductionAlthough diverse and stratigraphically significant conodont

faun as have been described from Ordovician sequences in

Norway since th e early 1960's (see, for instance, Hamar

(1964, 1966),Kohut (1972),Bergst rtim (1979), Nickelsen et al.

(1985),Bruton et al. (1988),Rasmussen & Stouge (1988, 1989,

1995),Bruton et al. (1989),Rasmussen (1991) and Rasmussen

& Bruton (1994)), t hese fossils remain very poorly know n, or

unkno w n, in many Ordovician deposits both in the Oslo

Region and in other par ts of th e cou ntry. This is ill ustrated

by th e fact th at con odonts have previously been described

from only a single formation, th e Holond a Limestone, in th e

classical Trondheim Region (Bergst rti m 1979). Alt hough the

know n Ordovici an conodont faunas of th e Oslo Region are,

wi th one imp or tan t except ion (that of th e Mjosa Limestone),

closely simila r to, if not identical wi t h, t he coeva l ones in

Sweden (Lindstrti m 1955, Bergstrti m 1971, Ltifgren 1978),

the conodont fauna of th e Holonda Limeston e (Bergst rti m

1979) is quite different from equivalent Baltoscand ic faunas

but much more similar to corresponding faunas from th e

marginal areas of Laurent ia. The Laurent ian faunal aff inity of

t hese conodonts, as well as of many macrofossils in this and

ot her un it s in the Trond heim area, has led some invest iga­

to rs (see, fo r instance, Bruto n & Bockelie (1980)) to suggest

th at th is region may represent a fragm ent of Laurentia that

became attached to Balt ica in post-O rdov ician time. In view

of th is, it is obviously of considerable interest to investi gate

th e conodon ts from other carb onate uni ts in th e Trondheim

area succession s. Equally important, such stud ies have the

potential to produce reliable biostratigraphic information

that may help clarify the very poorly know n age of several

important units in th is geologically complex region where

both strat igraphical and st ructu ral relat ion ships have long

been highly cont roversial.

The mo st promine nt, and proba bly most stu died, lim e­

stone uni t in the Holon da-Me ldal succession s is the Kalstad

Limestone, wh ich is st ill well exposed at its classical locality

at Bergsbakk en along th e highway about 1 km no rth of

Meldal (Kicer 1932). Limestone s of substantial th ickness and

probably comparable age outcrop at several oth er localiti es

in th e Meldal area, particularly on th e slopes of th e valley of

t he Orkl a river 6-8 km sout h of Meldal. Several sets of sam­

ples collected from the Kalstad Limestone at its type locality

were either barren,or contained only sparse conodont spec­

imens of stratigraphically undiagnost ic forms of Panderodus.

In an attem pt to discover mo re signi ficant conodont occur­

rences, 11 samples were collected in 1982 from a relati vely

th ick limestone succession at Svart seetra, about 13 km east

of Meldal. The purpose of the present cont ribution is to

describe the conodont fauna from these samples, which is

current ly un iqu e for the Central Scandinavian Caledonides

in term s of species association and age, and assess its blo ­

st ratig raphic and paleobiogeogr aphic significance.

The Svartseetra limestone outcropAs noted by Bruton & Bockelie (1982,p.88), th e relation ships

between th e limestone succession at Svart seetra and the

Kalstad and Holonda limestones in the north and west, res-

NG U -B UL L 432 ,199 7 - PA GE 60 STlG M . BERGSTROM

o Volcanic sands tone and shal e

~ Rhyo li te tuff @ Kalsta d Limestone

SVARTSAETRA

SVORKARIVER

100I

m

o!

~ HORG FAULT

0.5

km

SVARTSAETRA

oI

A 8

1I

.~

I .:."

o I,km

8

Fig. 1. Sketch maps showing the location of the Svart seetra limestone locality 13 km east of Meldal in the Trondheim Region . A, map showing the ge­neral geology south of the Horg Fault; B, map showing the geographic locat ion of the Svart seetra section; C, map of the Svartseetra limestone outcropand collect ing levels of conodont samples. The beds in the outcrop are essentially vertical. Collect ing levels were measured from the top of the basaltuff bed at the nort hwestern end of the section. D,map of south ern and central Norway showing location of study area (star).

pectively, remain unknown, and there are rather conspi­

cuou s lithological differences between th ese units. Unti l the

regional relation ships of th e former unit have been clarified,

the informal term Svattseetra limestone is used herein for the

unit under discussion. A total thicknessof about 122 m of li­

mestone was measured along the forest track just southeast

of Svart seetra in 1982 when there was an almost cont inuous

exposure becauseof recent logg ing and bulldozing of a sev­eral meters wide area along both sides of the t rack (Fig. 1).

The lithologically rathe r monotonous carbonate succession

consists of grey to dark-grey, fine -grained, somewhat nod u­

lar, irregul arly bedded, in places shaly, limestone form ing es­

sent ially verti cal, in some cases rather massive, beds wi th nu­

merous calcite veins. Near the bottom of the Svartszetra

limestone, just above the under lying poo rly exposed darkshale is a pale-weathering reddi sh tuff bed. Oth er tuff beds

occur near the middle of the limestone succession and ju stabove the highest exposed limeston e beds at the road inter­secti on (Fig. 1). Because there is a few meters thick unexpo­

sed interva l between the latt er tuff bed and the overlyingdark-grey silty shales, the nature of the limestone/shale con-

tact is unknown. No indication of any significant fault or of a

possible strat ig raphic gap has been seen in the limestone

outcrop.

Material and methodsMost of the 11 sampl es from the Svartseetra out crop were

collected from the northeastern side of the track where the

soil cover had been largely removed exposing many lime­

stone ledges. The posit ion of each sample in relation to the

basal tuff bed is given in Fig. 1. About 2 kg of each samp le

were dissolved in 15% acetic acid fol low ing standard cono­

dont ext racti on procedures. The frequ ency of conodont ele­

ments proved to be low in all samples and one was barren(see Appendix). As is the case at most other localities in the

Holonda-Meldal region (Berqstrorn 1980), the conodont eo­

lor alterat ion index (CAI) is 5, indicati ng a heating of at least

300°C. The state of preservation of most specim ens is med i­

ocre, many elements being both broken and tecton ically de­

formed. This,along wi th the fact that the ent ire collect ion at

hand, also including indeterminable fragments, conta ins

on ly sligh tly more than 100 specimens. makes safe ident ifi -

STlG M. BERGSTROM

cation of the species difficult. Access to large collections of

much better preserved specimens of similar, and apparently

coeval, faunas fro m the Oslo Region and eastern North

America hasgreatly facili tated the taxonomic work . Because

of th e limited number of specimens available, and th eir rat­

her poor preservat ion, no formal taxon om ic description s are

included in this paper but brief comments on most of th e

species ident if ied are given below. Specimens illus tra ted in

Fig. 2 are hou sed in the type col lection of t he Orto n

Geological Museum (OSU) at the Ohio State University, and

other specimens are deposited in th e Microfossil Collect ions

at t he Department of Geological Sciences at the same uni ­

versity.

The Svartseetra conodont faunaThe general aspect of the conodont fauna of the Svartseetra

lim estone is quite different from th at of most broadly coeval

Balto scandic Middle Ordovician faunas in that it lacks repre­

sentatives of Amorphognathus, Baltoniodus, Dapsilodus,

Hamarodus, Periodon, Protopanderodus, and Scabbardella,

which are the common genera in those faunas (Sweet &

Berqstrorn 1984). Howeve r, someone famil iar w ith the

Middle and Upper Ordovician conodont faunas of eastern

North America will immediately recognize the Svartseet ra

conodo nt species association as being of a type present in

th e Ohio Valley Province (Sweet & Berqstrorn 1984) of th e

Midcont inent Faunal Realm (Berqst rorn 1990b) as indica ted

by the presence of, among others, Aphelogna thus, Belodina,

Phragmodus, and Pleetodina. Asshown by large und escribed

collections, t he fauna of th e Middle Ordovician Mjosa

Limestone in the Mjosa district in th e nor thern Oslo Region,

altho ugh more div erse th an that from Svartseetra, is of the

same type and in all like lihood of th e same age. Likew ise, as

noted by Jaanusson & Berqst rorn (1980) and Sweet &

Berqstrorn (1 984),upper Middle Ordovician low-divers ity eo­

nodont faunas of North American aspect also occu r in theSaku Member of th e Vasalemma Format ion (Oandu Stage) inEstonia (see also Viira 1974, Mannik 1992). Rare specim ens

of Belodina (Berqst rorn & Berqstrorn 1996) and Phragmodus

are known to be present in the Upp er Ordovician of Sweden

but represent at ives of th ese genera are un known in older

strata of that coun try. As is well kno wn, th e Mjosa

Limestone, the Kalstad Limeston e, and the Saku Member of

the Vasalemm a Format ion contain shelly fossils with Nor th

Am erican affi nities (see, for instan ce, Kizer 1932, Spjeldnces

1978, 1985,Jaanusson 1979). Several auth ors have interpre­

ted th ese as represent ing a shor t-lived immigrat ion of North

American forms du ring a brief period of depo sition of shal­

low-water, tro pical-subtrop ical, bahamitic limeston es in the

Oslo Region and Estonia . The Svartscet ra limestone may be

of th e same type although it appears to lack the carbonate

mound s ('reefs') present in the Mjosa (Opalinski & Harland

1981; Spjeldnces 1982) and Kalstad Limestones (Kizer 1932,

Opalinski 1980) and in the Vasalemma Format ion (Hints

1990).

NG U -BULL 43 2,1 9 9 7 - PA G E 61

Stratigraphic ageAlthough a total of less than a dozen conodont species have

been identi fied in the Svartseet ra samples (see Appendix),

several of th ese are biostrat igraphically high ly significant,

and, in combi nat ion, t hese species permit a rather precise

dati ng of the unit in term s of standard chronost rat igraphic

un it s in th e Midd le Ordo vician of th e North American

Midcontinent. The up per and lower 20-30 mete rs of th e ap­

proximately 120 m thick Svart seetra limestone are less we ll

biost rat igraphically contro lled than its main part, but t here

is no evidence of any important faunal change at any level in

th e succession, and no sign ifi cant new taxa appear in the

upper portion of the unit. Hence, in the absence of eviden ce

to the contrary, it is suggested that the Svartscetra limestone

represents a period of carbonate deposit ion wi t ho ut major

breaks.

Four conodont species are part icu larly important for the

biostrati graphically dating of th e Svart szetra limestone (Fig.

3). The hig hly characteristic species Phragmodus undatus

Branson & Mehl appears in the North American succession

in the upper Turin ian (upper Midd le Ordovician; upper

Mohawkian; Leslie & Berqstrorn 1995) and ranges through

most, if not all, of the Upper Ordovician (Barnes & Berqst rorn

1988, Fig. 4). This species is exceedingly com mon in many

faunas of the Ohio Valley Province (Berqstrorn & Sweet

1966), and its presence in the Svart seetra col lections indica­

tes th at t his un it is no old er th an the upper Turinian.

Anoth er significant Svartscetra species is Belodina confluens

Sweet, w hich ranges from th e bottom to th e top of th e unit.

Because this species evolved from B. compressa (Branson &

Mehl) in the upper portion of the Amorphognathus tvaeren ­

sis Zone (Sweet 1984), which corresponds to an interval in

the middle Shermanian Substage of the Chatfie ldian Stage,

the base of the Svartseetra limestone is no older than that in­

terval. The appearance of Belodina confluens has been used

as the base of the Belodina confluens Zone in Sweet's (1984)Midcontinent zone scheme. Of stratigraphic impor tance isalso Pleetodina cf. aculeata (Stauffer). The nominal species

appears in th e Chazyan Substage and ranges into th e mid­

dle Chatfield ian Stage (Kirkfie ldian-Shermanian substages)

(Sweet 1981). Finally,Aphelognathus cf.gigas Sweet is known

from the upper Kirkfieldian and Shermanian substages of

th e Chatfieldian Stage. Specimens that are indistinguish­

able from the Norwegian form occur in th e up per

Kirkfie ldian-Shermanian part of the Trenton Group of New

York and Ontario (for excellent illustrations of elements of

t his fo rm (identified as Pleetodina aculeata) from th e

Kirkfi eldi an Hull Format ion of Ontario, see Uyeno (1974, PI.

2)). Based on the presence of t hese for ms, it is concluded

that the Svartseetra lim estone in all likelih ood is coeval wi t h

th e Chatfie ldian Stag e, and th at it appears to represent t he

Shermanian Substage and the Belodina confluens Zon e in

th e Nor th American Midcontinent succession. The latter

zone is equi valent to th e lower portion of the

Amorphognathus superbus Zone in th e Atlantic conodont

NGU - BULL 4 32 , 199 7 - PAG E 62 S TlG M. BE RGSTROM

STI G M . BE RGSTROM NGU -BULL 432 , 1997 - PAGE 6 3 I

zone succession (Sweet 1984). There is no evidence in th e

collect ions at hand that the Svartseetra limestone rangesinto th e Cincinnatian (Upper Ordovician). That the Mj0saLimestone is of closely similar age is also supported by theoccurrence in that unit of Yaoxianognathus abruptus

(Branson & Mehl). This species has its principa l occurrencesin Chatfieldian strata although a few specimens have beenfou nd in the lowermost Cincinna tian in eastern NorthAmerica (Sweet & Bergstrbm 1971).

The occurrence of several components of this fauna in

the Saku Member of the Vasalemma Formation in Estoniafits well with th is age assignment. That is, in eastern Nort hAmerica these species occur in a relatively narrow inter valsomewhat above the Mil lbrig K-bentonite that marks thebase of the Chatfieldia n (Leslie & Bergstrbm 1995). This K­bentonite was correlated with the equal ly prominent

Kinnekul le K-bentonite in Baltoscandia (Huff et al. 1992,

Bergstrbm et al. 1995) which marks the base of the KeilaStage (DII) in Estonia. The Saku Memb er of the VasalemmaFormation is placed in the lower part of the overlying OanduStage (Dill), hence in a similar stratigraphic position in rela­t ion to the Kinnekulle K-benton ite asthat of th e ShermanianSubstage to the Millbrig K-ben tonite in North America (Fig.4). A link support ing this correlation is also the relativelyshort-ranging and dist inctive graptol ite zone indexClimacograptus spiniferus Ruedemann. This species, recor­ded in older literature as Climacograptus dip/acanthus

Bulman, wh ich is a junior synonym of C. spiniferus (cf. Riva1976), has long been known from the Oandu (Dill), Rakvere(E), and lowermost Nabala (Ea) stages in Estonia (Kaljo &

Manni l 1990; Manni l 1990) whereas in the Cincinnati regionin east-centra l North America this species occurs in the up­per Chatfieldian (Shermanian Substage) and lowermostCincinnatian (lower Edenian Stage) (Mitchell & Bergstrbm1991). This Estonian-North American correlatio n is also inagreement with the fact that the Saku Member of the

Vasalemma Formation has been placed in the lowermost

Fig. 2. sDiztacodus» cf. trigo nius Scho pf, Phragm odu s unda tus Branson &Meh l, Drepanoistodu s sp., Panderodu s cf. feu/neri (Gleniste r),Staufferella sp., Belodina confluens Sweet, Aphelogna thus cf. gigas

Sweet, Plectodina cf. tenuis Branson & Mehl,and Pleetodin a cf.acu/e­

ata (Stauffer).

A, «Distacodus» cf. trigonius Schop f (OSU 48630 ), symmetrical ele­

ment , lateral view,x l 00.Sample 82B15-l.

Phragmodus undatus Branson & MehlB, geniculate eleme nt (OSU 48631), lateral view,x150.Samp le 82B15­

3.G, Seleme nt (OSU 48632), lateral view,x 120.Sample 82B15-9.

C, Drepanoistodu s sp, broken specimen (OSU 48633), lateral view,x120.Sam ple 82B15-7.

D, Panderod us feulneri (Glenister) (OSU 48634), late ral view, x100.Sample 82Bl s-1.

E, Staufferella sp. (OSU 48635), po sterior view,x l 00.Sample 82B15-1.

F, Belodina confluens Sweet (OSU 48636), rost rate element, lateral

view,x140, Sample 82815-9.Aphelognathus cf.gig as Sweet

NORTH AMERICA CONODONTS

en s Ranges of species 5i<I>

.~ ~ .~ ~.Q! 0> ~Jj '"{jj .0 ~N:>(f)

~

~0

z w'"Z c: '"Zz -c u:: <I> "~ « Z w " £

w 0 "" .. '"()- s ~ ~~z 0 f-w .. o(3 a !!? .. ~§.z " ~

<:>(; '"z ..~-c ..

'"z~

!Xl< -~a:

~I----

.!!1Z w '" ":I: ~ ~-c~ ~z Ci Z en 8 it-c ...J < ~ c -- w 15 ill .. ? .!!1u:: ...J

~Z w c '"u: " Ul~- f- Ul .2 ..

< >.:

~ '" .g: '" ..-c :I:

a: !Xl ~~

-' o ~

~ 13 ill---z-- '"§ !!Ja. -c l.'1 " Ul £

:::;; 15 it , s -5 ..z .. §.:'S §. 0

-c E 0

:I: I<: Q 0) "§.8 '" s.c if 0o ~ Ea: «:0

~wz

:::!: u:: --wif 0~ f-az

Fig.3. Chart show ing the know n vertical range s of some conodont spe­

cies in terms of standard upper Middle and lower Upper Ord ovicianchro nost rati g raphic and biostratigraphic units in North America.

part of the Amorphognathu s superbus Conodont Zone(Mannik 1992) , the base of which is near the midd le of theShermanian Substage in North America (Goldman et al.1995, Fig. 14). Hence,several lines of independent evidenceare in agreement with the t rans-Atlantic correlations propo­sed herein (Fig.4).

Alt hough it cannot yet be proved by biostratigraphic orothe r evidence, it seems quite probable that the Kalstad

H, Paelement (OSU 48637), lateral view,x l 00.Sample 82B15-9.

I, Sc element (OSU 48638), lateral view, x90.Sample 82B15-2.J, Pb element (OSU 48639), latera l view,x90. Sample 82B15-7.M, Pb element (OSU 48640),anterior view,x l 00.Sample 82B15-3.

0, Saelement (OSU 4864l), po sterior view,x l 00. Sample 82B15-8.

P/ectodin a cf. tenuis Branson & MehlK, M eleme nt (OSU 48642), lateral view,x75.Sample 82B15-2.

L, Sc element (OSU 48643), late ral view, x l 00.Sample 82B15-2.

Q, Sb element (OSU 48644), posterior view,x l 00.Sample 82B15-7.

R, Pb eleme nt (OSU 48645), inner posterior view,x85.Samp le 82B15­7.

5, Pa eleme nt (OSU 48646), lateral view of fragment th at probablybelongs to thi s species,x60.Sample 82B15-2.

T, Sa element (OSU 48647), po sterior view of incomplete specimenth at tentatively is referred to thi s species.x8s.Sample 82815-1.

Plectodina cf.aculeata (Stauffer)

N, Sb element (OSU 48648), posterior view,x l 00.Sample 82B15-2.P, Pb eleme nt (OSU 48649), lateral view,x1 40.Sample 82B15-1.

NGU - BU LL 4 32 ,1 9 9 7 - PAG E 6 4 S TlG M. BERGSTROM

NORTH AMERICA NORWAY C. SWEDEN ESTO NIA S. SCOTLAND BALTOSCANDIA

(/)

N. Oslo(/) ID ci (/) Tron dheim (/) (/) ci (/)(/) Cl Fms. &IDID

'" 'O C) region Format ions Un its CD . Q) 'OC)Cl en o c region (Melda l· .~ Cl

.~ '" c 0 (Mj0sa) Mbrs. '"o c

Ci5 .0 C 0(f) :J 8 N H010nda) Fms. (f) Ci5 8 N

(f) Fms.

Z SLAN DROM HAR-

« z 0 (/) .AJMI

'i= <l: f- UJ c:~Z Q) RAK-

~« O~ ::> RAGAVEREoz UJ zLL. ;;::: ? VERE -e

0 UJ c: Cl>Z UJ 0 0 ARDWELL I- --- g-O

0MOLDAC\l GRP .

(/)

z s SVART- pANDUE

-c .2 SAETAA & MJ0SA SAKU CRAIGHEADoq:

Z Q)

<l: en ?KALSTAD MBR.::2: ? .... - - -a: .!(! ZUJ ::>

z I c: «Z (f) s« <l: Z -: VASALEMMA

- <l: 0... :::)

- 0 CS er:...JZ ...J(/) -UJ UJ .!(!- - u::: ::> (/)

« LL. ~ {g > c:

....J f- a: c: FURU BERGET SKAGEN KE ILA ~

-c 52 ::> Cl>

? ~o, I(/) BALLANTAAE::>

~ o 'b VOLC ANIC(/)

z 0 ::>

« ~ -c EO: COM PLEX -So CS Ol C\le: c:

I 0 z Ola: :5 et 0

0 -cKAHALAGRP. e-

o

MILLBRIG K·BENT. K!NNEKULLE K-B EO:oq:

z 0 ---- Z-cZ

f-UJDALB Y

<l:JOHVIoz =:l

er Z[[ HOVINS- a:=:l UJ 5f- 0 HO LM

Fig. 4. Correlation diagram showi ng prop osed strat igraph ic positions of the Svartseetra, Kalstad, Mj0sa, and Craighead limestones and the SakuMember of the Vasalemma Formation, as well as some other important st rat igraphical units, in terms of the standard chronostratigraphic schemesused for the upper Middle and lower Upper Ordovician in North America and Baltoscandia, respectively. Note the posit ion of the unit swith Laurentianfaunal aff init ies in relat ion to the North American Millbr ig and the Baltoscandic Kinnekulle K-bentonites,which have been interpre ted to represent thesame gigantic ash fall (Huff et al. 1992).

Limestone represents the same period of unusual carbon ate

deposition as the Sva rtseetra and Mjosa limestones. Severalaut hors (see, for in st an ce, Kicer 1932 ) hav e co m pa red th e fo s­

sils of the Kalstad Limestone with those of th e Craigh ead

Limeston e in South Scotland . A recent study of the

Craighead conodont fauna (Bergst rbm 1990a) showed it to

be of mixed provincial character but it seems to be of the

same age (Iowermost Amorphognathus superbus Zone; cf.Bergstrdm 1990a) as th e Baltoscandian units under discus­

sion. The Craighead is also a unique local carbonate deposit

surrounded by clast ics and it rests on the Ballantrae Volcaniccomple x, an ophio lite. Hence, it depositional setting is remi­

niscent of th at of the Kalstad Limestone, which Spjeldn ees

(1985) interpreted to have been on the flanks of a volcanic

island. It is uncertain if the Svartseetra limestone was laid

dow n und er similar environmental conditions but the volca­

nic island sett ing certainly does not apply to the Mjo saLimestone and Saku Member of the Vasalemma Formation

that represent shallow-water continental platform, or in the

case of th e Mjosa Limestone possibly shelf, carbonates

which are underlain by a stratigraphically rath er comp lete

succession of Lower and Middle Ordovician marine sedi­m ents.

Paleoecologic and paleogeographic significanceAs not ed above, the Svartseetra conodont species, like those

of the Mjosa Limestone and the Saku Member of the

Vasalemma Formation, are forms that in North America are

typ ically found in shallow-water deposits in the Ohio ValleyProvince. In the biofac ies mod el of Sweet (1988, Fig. 7.3),

species assemblages having common representat ives of

Pleetodina and Aphelognath us and somewhat less com monPhragmodus, as that of th e Svartseetra limesto ne,are placed

in an intermediate shallow-water depth zone between that

of the very shallow -water Rhipidogna th us biofacies and that

of the deeper-water Amo rph ogna thu s-Phragmodus biofa ci­

es (Fig. 5). For the biofacies present in the Mjosa Limesto ne

and the Saku Member of the Vasalemma Formation,Sweet &

Bergstrdm (1984) int roduced the designation the

'Phragmodus-Icriodella-Plectodina biofacies' and this term

S TlG M. BERGSTROM

f---- - --- - - --- INCREASEDWATER DEPTH

Fig.5. Project ed position of the Svartseetra limestone conodont fauna intermsof Sweet's (1988,Fig.7.3) Midd le-Upper Ordovician conodont blo­fad es mode l for th e North American Midcontinent. As described in th etext, the non-coniform port ion of the Svartseetra conodont fauna is do­minated by Plectodino and Apheloqnathu: with more sparse occurren­cesof Phraqmodus.

may be applicable also to the Svartseet ra species associati ondespite th e fact that no specimen of Icriodella has yet been

found in th at unit. This biofacies is unknown in coeval strata

in Sweden although rare specimens of Icriodella have been

collected from the Mold a Formation (Bergst r6m, unpublis­

hed),which is a likely equiva lent of the Svartseetra limestone(Fig.4). It is prob able th at the water depth in the depositi on­

al environment of the Mold a Formation and coeval strata in

Sweden was too great for the development of thePhragmo dus-Icriodella-Plectodino biofacies whi ch is here re­

placed by the Hamarodus europoeu s-Oopsilodus tnu tatus­

Scobbordello oltipes biofacies of Sweet & Bergstr6m (1984).

The recognition of water depth asa significant control of

the distribution of som e conodont species is important inpaleogeographic int erpretations using these fossils. For

example, the occurrence of conodont faunas of North

American aspect in the Mjesa Limestone and the Saku

Member of the Vasa lemm a Formation proves the existenceof faunal interchange but it does not prove geographic pro ­

ximity between Baltica and Laurent ia because many

Ordovician cono donts clearly were able to migrat e across

the lapetu s and other Early Paleozoic oceans (Bergstr6m

1990b). The conodont faunasof the Svartseetra and H010nda

limestones in the Trondheim region show profound

Laurentian faunal affinities but it is uncertain whether this isdue to part icular environmenta l condit ions that led to the

development of a special biofa cies in two rather widely se­

parated regions,or to geographic proximity of the H010nda­

Meldal area to Laurentia that led to faunal exchange.

Accordingly, it is pertinent to be very cautious when usingconodonts like tho se discussed herein as tools for recon­

structions of the paleogeog raphic relations of the

Trondheim distr ict and oth er areas in th e lapetus region.

Concluding remarks

The present study is th e fi rst repor t of conodonts of

Laurent ian faunal affi nities in th e upp er Middl e Ordovician

of the Trondh eim region. These conodonts, alth ough scarce

NGU -BULL 432,199 7 - PAGE 65

and not wel l preserved, provide a rather precise age of thepreviously undated Svartseetra limestone. Furthermore, ba­

sed on th e reasonable assumption that th e well-known

Kalstad Limestone at its classical occurrence 13 km west ofSvartseetra represents the same phase of unique carbona tedeposition in theTrondheim region as that of the Svartszet ra

limestone, th e age of the former unit,which has been highl y

controversial, may also be final ly sett led.Attempts to obtai n conodonts from other, more or less

metamorphosed, limestone units elsewhere in the

Trondh eim Region, such as those at Grut south of Meldal

and Asen 40 km northeast of Trondheim (Spjeldnees 1985)

have been unsuccessful. However,some conodont elemen tsthat appear to have North American Whiterockia n faunal af­finity have been isolated from the Snasa Limestone in out­

crops along the E6 Highway southwest of F011ing (GR 235

202) near the western end of Lake Snasaabout 95 km north­

east of Trondh eim. A few conodonts that appear to be ofMiddle Ordovician age have also been foun d in the Skelberq

Form ation of Bruton & Bockelie (1979) on the Island of

Sm01a off the west coast of Central Norway about 120 kmwest-southwest ofTrondheim, but fur ther sampling is nee­

ded to clarify the age and aff ini ty of th at fauna. Clearly, eo­nod ont research in the Ordovi cian of the Trondhe im Region

is both challengin g and ti me-consuming, but as shown bythe present study, low- metamorphic Caledonian rocks that

look unprom ising for this kind of investigations may produ ­

ce faunas of considerable strat igraphic and paleonto logic

interest.

Remarks on selected speciesAphelognothus cf.gigos Sweet, 1983Figu res 2; H, I,J, M,0 , S

This disti nct species is characterized by well-developed, in

most casespeg-like, process denticles; a slightly angulate Paelement with flaring basal cavity and, in some but not all

specimens,a gap in the dent icle row just in front of the cusp;

angulate (not pastinate) Pb element; bipennate M element;

and a bipennate Sc element w ith several distinct denti cles

laterally on the anter ior process.

The present species appears to be unn amed but it

should be noted that some aspects of the taxonomy of

Aphelognothus are still not well understood. It differs from

Aphelognothus gigas Sweet from the lower Chatfieldian Fite

Formation of Oklahom a (Sweet 1983) in the appearance of

the Pa eleme nt (=Pb element in Sweet 1983) and in having a

Pb element (Pa element in Sweet 1983) that is not clearlypastinate (dichognathiform). However, th ese differences are

relat ively small and the present species may wel l be a direct

descendant of A. qiqas. A form described by Leslie (1995) as

Apheloqn athus cf.A. gigos from the upper Turinian and low­es t Chat fie ld ia n o f th e North American Midcontin ent is

closely similar to the Norwegian species and differs only inthat the Pb element tend sto be pastinate rather than bip en­

nate. The present species differs from Aph elognothuspolitus

NGU-BU LL 432 ,1997 - PA GE 66

Hinde in, among oth ers, t he denticulated margin of t he Sc

eleme nt. The species is well repres ented in coll ections from

midd le-u pper Chatf ield ian strata in th e Trenton Group of

New York and Ontario assem bled by Scho pf (1966) and from

the Lexington Limestone of Ken tucky and Ohio (Berqst ro rn

& Sweet 1966). It is qu ite abundant in undescribed co llec­

tions from t he Mjosa Limesto ne and also occu rs in the Saku

Me mber of th e Vasalem ma Format ion in Estonia. It appears

to have a short range and be an excellent index of the up­

permost M iddle Ord ovici an in Nort h America.

Belodina confluens Sw eet, 1979

Figures 2; F

Representatives of thi s chara cter ist ic species occur th rough

v irt ua lly th e entire Svartseetra limestone sequ ence and both

rastr ate and gen iculate elements are pre sent. These are clo­

sely sim ilar to specimens fro m th e upper Lexing ton

Limestone in Kentucky (Berqstr o rn & Swe et 1966, PI.31, fig s.

14-17, 19) and other upper Middle and Upper Ord ovic ian

units in th e North American Midcontinent (fo r d ist rib ution

data, see Sweet 1981). The species is rare in north western

Europ e but is kno wn from t he Craig head Limestone in the

Girvan area, South Scot land (Bergst rbm 1990a, PI. 3, fi gs. 8­

12), the Jon storp Form at ion and coeval st rata in Sweden

(Berqst ro rn & Berq st rorn 1996, Fig. 9.P), t he Saku Member of

t he Vasalem ma Fo rmat ion in Eston ia (Viira 1974, PI. 13, f ig .

11), and errat ic boulders in Po land (Dzik 1976, Fig. 14.g -h).

The species is also present in undescr ib ed co llection s from

the Mjosa Lim estone.

«Oistacodus»cf. trig onius Schopf, 1966

Figure 2; A

A sing le specime n appears so sim ilar to t he symmet rical ele­

ment of t he ap par at us of Schopf's (1966) Chatfield ian speci­

es from the Trenton Gro up of New York t hat it is likely to be

th e same fo rm bu t addi tiona l specime ns are needed to con­

fi rm th is. It is certainl y not congeneric w it h DistacodusPa n der, 18 5 6 a n d probabl y repre sents a n e w gen us. T h is is

an unusual fo rm in th e North Am erican Middle Ordov ician

Mi dcont ine nt faunas. Specim en s from th e Upp er

Ordovician, such as those of the Dubuque Format ion of

Iowa, are simi lar morpho logically and may repr esent th e

same species.

Drepanoistodu s spp.

Fig ure 2;C

Specimen s of the w idesp read ge nus Drepa no istodu s

l.indstrom, 1971 are pre sent in moderate numbers in the

Svart seetra samples. Some are conspecif ic wi th D. superbus

(Branson & Me hl, 1933) w hereas t he affini ti es of ot hers, such

as th e il lustrated eleme nt, rem ain in doubt. The taxonomy of

t he genus is cur rent ly un satisfacto ry,and large collecti ons of

spec ime ns are need ed fo r safe ide nt ifi cati on of severa l spe­

cies. At the present t im e, Middle Ordovician spec imens of

Drepanoistodus have litt le, if any, biostratig raph ic signifi cance.

STlG M. BERGSTROM

Panderodus cf.feulneri (Glenister, 1957)

Figu re 2; D

Some of the Svartseetra samples contain robust elements of

a spec ies of Panderodus chara cterized by a very large base

and a relat ively short cusp . Although rem in iscent of P. feul­

neri (Glenister) in genera l shape, they lack the well- defin ed

lateral costae present in representat ives of that spec ies. The

p resent species also resembles Panderodus breviusculus

Barn es, 1977, but di ffers in the outline of the base. The

Svartseetra species is also present in undescribed co llections

from t he Mjosa Limestone. Panderodu s feulner i was or ig ina l­

ly describ ed from the Upper Ordovician Maquoket a Shale of

Iowa (Gleniser 1957) and similar form s are w idely distributed

in t he Mi ddle and Upper Ordovician of the North American

Mi dcontinent. These faunas, as w ell as th at of Svartseet ra,

also cont ain a much more slender form, w hich is commonly

ide nt if ied as Panderodus gracilis (Branson & Mehl). These

species have lit t le, if any, biostra tigraph ic significance.

Phragmodus undatus Branson & Mehl, 1933

Figure 2;G

Th is highly characteristic species, w hich has recently bee n

d iscussed in some de tail by Leslie & Berqstrom (1995), rang­

es through the entire Svartszetra succession but is represen­

ted by only a small number of spec imens that in all respects

are ide nt ic w ith North American specimens. It is one of the

most common conodonts in the upper Midd le and Upper

Ord ov ician of North America (fo r occurrence data, see Sweet

1981) bu t it is rare in Europe, be ing recorded, in most cases

just as sing le spec imens, from t he upper Middle Ordovician

of Wales (Savage & Basset t 1985), the Upper Ordovic ian of

t he Girvan area, South Scotland (Bergst rbm 1990a, PI. 4, fig .

10), th e Saku Member of the Vasalemma Form at ion (Viira

1974, PI. 12, fig. 19), and the Upper Ordovician of Sweden

(Berqst ro rn unpublished). The species is quite abundant in

t he Mjosa Limestone.

Plectodinu cf . a culeata (St a u f fe r, 19 3 0 )

Figures 2; N, P

A few, rather poorly pr eserved, spec ime ns in th e Svartszetra

colle ction are ten tatively referred to th is spec ies but add it ion­

al specimens are clearly needed fo r safe identification . The

ten tati ve iden ti fication of the Svartseetra specime ns is ma in ly

based on the pasti nate Pb elem ent. In Nor th America,

Plectodina aculea ta is wi dely d istr ibuted in,and highly charac­

terist ic of, strata of Chazyan to early Chatfield ian age (Sweet

1981). The lowest par t of its stratigraphical range wa s d istin ­

guished as the Pleetodina aculeata Zone by Sweet (1984).

Plectodina cf. tenuis (Branson & Meh l, 1933)

Figures 2; K, L, Q, R, T

A few specimens in the Svartszetra collections are closely si­

milar to Pleetodina tenuis (Branson and Mehl) and four suc h

ele ments are ill ust rated in Fig. 2. Because of th e small num­

be r of specim ens at hand, t he identification is tentative but

STlG M . BERGSTRO M

no signi ficant morphological differences were noted at a dir­ect comparison with the North American form (cf. Sweet1981 , PI. 12, figs. 11-12, 14,18). In North America, representa­tives of P. tenuis are known from many localities in strata

ranging in age from the Chatfield ian Stage to the Upper

Ordovician Richmondian Stage.

Staufferella sp .

Figure 2; EA sing le specimen in the Svartscetra samples is simi lar torepresentatives of Staufferella, especially S. falcata (Stauffer,1935), but add it ional specimens are needed for specificidentification. This specimen has the conspicuous lateralcostae with weakly developed nod-like basal structures cha­

racteristic of the genus but the posterior face of the cuspdoes not exhibit the carinae seen in most specimens fromthe Middle and Upper Ordovician of North America. Moretyp ical Staufferella specimens occur in unpublished collecti ­ons from the Mj0sa Limestone.

AcknowledgementsI am indebted to D. Bruton, R.B. Neuman and the reviewers J.A.

Rasmussen, and N. Spjeldnees for reading the manuscr ipt and offeringusefu l comments. Thanks are also due to D. Goldman, H. Hayes, l CMitchell, and K. Tyler for valuable technical assistance, and to my w ife.Birg itta Bergst rbm , for help in collecting the conodont samples.

ReferencesBarnes,CR.& Bergstrbm,S.M. 1988:Conodont biostratigra phy of the up ­

perm ost Ordovician and lowermost Silurian, Bulletin of the British

Museum, Natural History (Geology) 43. 325-343.Bergstrbm, s.M. 1971: Conodont biostratigraphy of the Middle and

Upper Ordov ician of Europe and eastern North America.Geolog ical

Society of America Memoir 127,83-157.Bergstr bm, s.M. 1979: Whiterockian (Ordovician) cono do nts from the

Holonda Limestone of the Trondheim region, NorwegianCaledon ides. Norsk Geologisk Tidsskrift 59, 295-307.

Bergstrb m, s.M. 1980: Conodonts as paleot emperature too ls inOrdo vician rocks of the Caledon ides and adjacent areas inScandinavia and th e Brit ish Isles. Geolog iska Foteninqens i

Stockholm Forhan dlinqar 102,377-392 .

Bergstrbm, s.M. 1990a: Biostratigraphic and biogeographic sign ificanc eof Middle and Upper Ordovician conodonts in th e Girvan successi­on, south-west Scotland .Courier Forschunq-lnstitut Senckenberg 118,

1-43.Bergstrb m, s.M. 1990b: Relat ions between conodont prov incial ism and

the chang ing palaeog eography during the early Palaeozoic. In:

McKerrow, W.s. & Scotese, C R. (eds.). Paloeozoic Palaeogeography

and Biog eography.Geological Society Memoir 12. 105-121.Bergst rbm, s.M.and Berqstr om.J, 1996:The Ordovician-Silur ian bou nda­

ry successions in Osterqot lan d and Vaste rqo tland, s. Swed en.Geologiska Foreninqens i Stockholm Forhandlinqa r lIB. 25-42.

Bergstrbm, s.M., Huff,W.D.•Kolata, D.R., & Bauert , H. 1995:Nomenclature,stratigraphy. chemical fingerprin tin g,and areal d ist ributi on of someMiddle Ordovic ian K-benton ites in Balto scand ia. Geolog iska

Foreninqens i Stockho lm Forbandlinqar 117, 1-13.Berg strbm. s.M. & Sweet, W.C 1966: Conod ont s from th e Lexington

Limestone (Middle Ordovician) of Kentuck y and its lateral equiva­lent s in Ohio and Indi ana. Bullet in of American Paleontology 50,27 1­441.

Brut on, D.L.&Bockelie, J.F. 1979:The Ordovician sedimentary sequence

N GU-BULL 432 ,1997 - PAGE 67

on Srnola, west central Norway. Norges geologiske undersekelse 34B,

21-32.Bruton , D.L. & Bockelie, J.F. 1980: Geology and paleontology of the

Holonda area,western Norway - A fragment of North America? In:

Wones, D.R. (ed.). The Caledonides in the U.s.A. Department of

Geological Sciences, Virgin ia Polytechnic Institu te and State University,

Memoir 2,41 -47 .Bruto n, D.L. & Bockelie, J.F. 1982: The t.ekken- Helonda-S teren areas. In:

Bruton , D.L. & Willi ams, s.H. (eds.). IV. International Symposium onth e Ordovician System. Field Excursion Guide. Palaeo nt ologica l

Cont ribut ions, Universi ty ofOslo 279.77-91.Bruton , D.L., Koch, L. & Repetski, J.E. 1988: The Naersnes secti on, Oslo

Region , Norway : tr ilobite, graptolite and conodont fossils reviewed .

Geolog ical Magazine 125,451-455.Bruton , D.L., Harper, DAT. & Repetski, J.E. 1989: Stratiqraphy and faunas

of the Parautoc hthon and lower Allochthon of southern Norway. In:Gayer, RA (ed.). The Caledonide geology of Scandinavia, 231-24 1.

Graham & Trotma n, Lond on.Dzik, J. 1976: Remarks on the evolution of Ordovician conodonts. Acta

Palaeontologica Polonica 21, 395-455.Glenister, A.T. 1957: The conodonts of the Ordovician Maquo keta

Format ion in Iowa.Journal ofPaleontology 31. 715-736.Goldman,D.•Mitchell,CE.,Bergst rbm,s.M.,Delano.J.w.,& Tice,5.1994:K­

bentonites and qraptolite biostrat igraphy in the Middle Ordovicianof New York State and Quebec: A new chronostratigraphic mo del.

Palaios 9, 124-143.Hamar, G. 1964:The Middle Ordo vician of th e Oslo Region, Norway. 17.

Conodonts fro m the lower Middle Ordovician of Ringerike. NorskGeolog isk Tidsskrift 44, 243-292 .

Hamar, G. 1966:The Middle Ordovic ian of the Oslo Region , Norway. 22.Preliminary repo rt on conodont s from the Oslo-Asker andRingerike district s.Norsk Geologisk Tidsskrift 46, 27-83.

Hint s, L. 1990: Locality 2:2. Vasalemma Quarry. In: Kaljo, D. & Nestor, H.(eds.). Field Meeting Estonia 1990. An excursion guidebook, 131-133.Instit ut e of Geology, Estonian Academ y of Sciences,Tallinn .

Huff,W.D., Berqst rom, s.M.& Kolata ,D.R. 1992:Gigant ic Ordovician volca ­nic ash fall in North America and Europ e: Biological, tec to nomag­matic,and event-s t ratigraphic significan ce. Geology 20,875-8 78.

Jaanusson, V. 1979: Ordovician. In: Robison , R.R. & Teichert, C (eds.).Treatise on Inver tebrate Paleontology. Part A. Introduction, A136­A166 .Geolog ical Society of Amer ica and University of Kansas.

Jaanusson, V.& Bergstrbm, s.M. 1980: Middle Ordovician faunal spat ialdifferent iat ion in Balto scandia and th e Appal achian s.A/cheringa 4,

89-110.Kiljo, D.& Mann il, R.1990:Graptolites. ln: Kaljo, D. & Nestor, H. (eds.). Field

meeting Estonia 1990. An excursion gu idebook, 90-92. Inst itu te ofGeology, Estonian Academy of Sciences,Tallinn.

Kiaer, J. 1932: The Hovin Group in th e Trondheim area. Norske

Videnskaps-Akademi Skrifter 1. Mat. Naturvidenskap Klasse 1932(4),

175 pp.Kohut, JJ . 1972: Conodont biostrat igraphy of the Lower Ordo vician

Orthoceras and Stein Limestone s (3c), Norway. Norsk Geologisk

Tidsskrift 52,427-455 .

Leslie, SA 1995: Upper Middle Ordovician conodont biofacies and litboia­cies distr ibution patterns in eastern North America and north western

Europ e: Evaluations using the Dek ke, Millbrig and Kinnekulle K-bento­

nite beds as time planes. Unpublished PhD. dissertat ion,The OhioState Univ ersity, 449 pp .

Leslie, SA & Berqstrorn, s.M. 1995: Revision of th e North American lateMiddle Ordovician standard stage classification and timing of th eTrenton transgression based on K-bent on ite bed corre latio n. In:

Coop er,J., Droser,M.L.& Finney, S.C (eds.).Ordovician Odyssey: Short

papers for the Seventh International Symposium on the Ordovician

System. Pacific Section Society for Sedimentary Geology (SEPM), Book77,49 ·54 .

l.indstro rn, M. 1955:Conodonts from the lowermost Ordovician strata ofsouth -central Sweden. Geologiska Foreninqens i Stockholm For­handlingar 76, 517-604.

Lbfgren, A. 1978: Arenigian and Uanvirn ian conodonts from Jarntland,

N GU - B U L L 4 3 2 , 1997 - PAGE 68

northern Sweden.Fossils an d Stra ta 13, 1-129.

Man nik, P. 1992: Uppe r Ordo vician and Lower Silu rian con od onts in

Estonia.Disserta tiones Geolog icae Uni versi ta tis Tattuensis,49 pp.

Mann il, R. 1990:The Ordo vician of Eston ia. In: Kaljo, D.&Nester, H. (eds.),Field Meeting Eston ia 1990. An excursion guideboo k, 11-20. Institute

of Geolog y, Eston ian Academy of Sciences,Tallin n.Mitchell, e.E.& Bergstr6m , 5.M. 1991: New grapt ol ite and li tho st ratigrap ­

hie evidence from the Cincin nati region , U.S.A., fo r the defin it ion

and correlation of the base of the Cincinnat ian Series (UpperOrdovician). In: Barnes, e.R. & Will iams, S.H. (ed s.). Advances in

Ordovician geology.Geological Survey ofCanada Paper 90-9, 59-77.

Nickelsen, RP., Hossack, J.R., Gart on, M. & Repet ski, J. 19B5: Late

Precam br ian to Ordovician st rati graphy and correlation in th e

Valdres and Synnfje ll th rust sheets of the Valdres area, southernNorw egian Caledo nide s; w ith some comment s on sedimentat ion .

In: Gee, D.G.& Sturt , BA (eds.),The Caled on ide orogen-Scandinavia

an d related areas. John Wiley and Sons, Chiche ster, 370-378.

Opalinski, P. 1980: Dep osit ional histor y of the Kalstad Limes tone,Trond heim regi on , Nor way. In: Wones, D.R. (ed.),The Caledo nide s inthe U.s.A. Depa rtm ent of Geological Sciences, Virgina Polytechnic

Insti tu te and State Universi ty, Mem oi r 2, A7.

Opa lin ski, P.R. & Harland , T.L. 1981: The M idd le Ordovician of the Oslo

Region , Nor way. 30. Strat ig raphy of the Mj osa Lim eston e in theTot en and Nes-Harnar areas.Norsk Geologisk Tidsskrift 61, 59-78.

Rasmu ssen, J.A. 1991: Conodont st rat ig raphy of th e Lowe r Ordovician

Huk Format ion at Slemmestad, sout hern Norway. Norsk Geolog isk

Tidsskrift 71, 265-288 .Rasmu ssen, J.A. & Brut on , D.L. 1994 : St rat igraphy of Ord ovician limesto­

nes, Lower Allochthon, Scandinavian Caledon ides. No rsk Geologisk

Tidsskrift 74, 199-212.Rasm ussen, J.A. & Stoug e, 5.5. 1988: Con od ont s from the Lower

Ordovician Stein Limeston e, Nor way, and a correlatio n acrosslapetu s. In: Will iams, S.H. & Barnes, e.R. (eds.). Fifth International

Symposium on the Ordovician System .Program and Abstrac ts, 78.Rasmu ssen, J.A. & Stouge, S.s. 1989: Middle Ordovici an conodonts fro m

allochthonous limesto nes at Hoyb erg et, southeas tern NorwegianCaledonide s. Norsk Geolog isk Tidsskr ift 69, 103-110.

Rasmussen,J.A.& Stouge, S.s. 1995: Late Arenig -Ear ly L1 anv irn con od ontbiofac ies across th e lapetus Ocean. In: Coope r, J., Dro ser, M.L. &Finn ey, S.e. (eds.). Ord ovician Odyssey: Short papers for th e Sevent h

In ternatio nal Sympos ium on the Ordovicia n System . Pacific Section

Society fo r Sedim entary Geolagy (SEPM), Book 77, 443 -447.

Riva,J. 1976:C1imacograp tus bicorn is bico rnis (Hall), it s ancesto r and like­ly descen dant s. In: Bassett, M.G. (ed.). The Ordovician System :

Proceed ing s of a Palaeo n tological Associa tio n symposium, Birm ing­

ha m, Sep tem ber 1974, 589-6 19. Univers ity of Wales Press and

Natio nal Museum of Wales,Card iff.Sava ge, N.M. & Basse t!. M.G. 1985: Ca radoc-Ashg ill co nod o nt fauna s

from Wales and the Welsh Bord erland .Palaeontology 28,711 -745 .

S TlG M . BE RGS TRO M

Schopf, T.J .M. 1966: Conod onts of the Trent on Group (Ordovician) in

New Yor k, southern Ontario, and Quebec. New York State Muse um

and Science Service Bull etin 405, 1-1OS.Spjeldnees, N. 1978: Faunal provinces and the Prot o-At lant ic. In: Bowes,

D.R. & l.eake, B.E. (eds.). Crusta!evolution in northwestern Brita in and

adj acent reg ion s.Geolog ical Journa l Special Issue 10, 139-1SO.Spjeldnees, N. 1982: The Ord ovician of the district s around Mj osa. In:

Bruton, D.L.& Will iam s, S.H. (ed s.). IV. ln ternat ional Symposium on the

Ordovician System. Field Excursion Guide. Palaeontological Contri­

butions, University ofOslo 179, 148-163.

Spjeldn ees, N. 1985: Biostrat igraphy of the Scandinavian Caledonides.ln:Gee, D.G. & Sturt, BA (eds.), The Caledonide orogen-Scandinavia

and related areas.John Wiley & Sons,Chichester, 317-329.

Sweet, We. 1981 : Genu s Aph elognathus BRA SON, MEHL, & BRANSON,1951; Genu s Belodin a ETHINGTON, 1959; Genus Phragmodus BRAN­

SON & MEHL, 1933; Genus Plect od ina STAUFFER,1935.ln: Zieg ler,W.(ed.), Catalogue of Conodonts, IV, 27-56, 57-84, 245-270, 271-290. E.

Schweizerbart' sche Verlag sbuchh and lung, Stuttgart.Swee t,W.e. 1983:Part 11. Conod ont biostrat ig raph y of Fit e Format ion and

Viola Grou p. In: Am sden, TW . & Sweet, We., Upper Bromide

Form ation an d Viol a Group (M iddle and Upper Ordovician) in eastern

Oklahom a. Oklahoma Geological Survey Bulletin 132,23-36.

Sweet, We. 1984 : Graph ic correlat ion of uppe r Middle and UpperOrdovician rocks, North Ame rican Midcon t inen t Province. In:

Bruton, D.L. (ed .), Aspec ts of the Ordovician System. Palaeontological

Cont ribut ions, University of Oslo 295, 23-35.Sweet,W e. 1988:The Conodonta: Mor phology, taxonomy, paleoeco logy

and evo lut ion ary history of a long-ext inct anima l phylum . Oxford

m onographs on Geology and Geophysics 10, 212 pp .C1arendon Press,Oxford.

Swee t, W.e. & Bergstrbm, S.M. 1971: The American Upper OrdovicianStandard. XIII. A revised time-strat igraphic classifi catio n of North

American up per M iddle and Up per Ordovician rocks. Geological

Society ofAm erica Bulletin 82, 613-628.

Sweet,W e. & Bergst rbm,S.M. 1984:Conod ont prov inces and biofacies of

the Late Ord ovician.Geological Society ofAmerica Specia l Paper 196,

69-87.

Uyeno,T. 1974:Conodonts of th e Hull Formation, Ottawa Group (MiddleOrd ovicianl. of the Ottawa-Hull area, Ontario and Queb ec.Geological Survey ofCan ada Bulletin 248, 1-31.

Viira, V. 1974: Ordovician conod onts in the east Balt ic. Inst itute ofGeology, Estonian Acade my of Sciences, Tallinn , 142 pp . (in Russian

w ith Eng lish sum mary).Vogt, T. 1945: The geo log y of part o f the Holonda-Horg d istr ict , a typ e

area in the Trondheim region.Norsk Geolog isk Tidsskrift 25,449-528.

Walsh, J.J. 1986:The geo log y and stru ctu re of the Horg Syncline, south­

east of Meldal , Sor-Trc ndelaq, Nor way. Norges geo logiske undetso­ke lse Bulle tin 406, 57-66 .

Manuscript received February 7997; revisedmanuscript acceptedJune 7997.

AppendixList of con od onts in each of th e Svartseetra samp les.Sam ple m-levels given wi thin brackets repr esent measurem ent s fromth e top of th e tuff bed near the northwestern end of the sect ion.Num ber of specimens is gi ven in bracket s after each ent ry.Sample 82Bl 5-1 (25 m). Be/odina confluens Swee t (l ); Belod ina ? sp. (l );

Panderodus cf. feulneri (Glenister) (2); " Distacodus» cf. trigonius Schopf

(1); Panderodus gracilis (Branson & Me hl) (3); Phragmodus undatus

Branson & Mehl (2); Plectodin a cf. tenu is Branson & Meh l (3); Stau ffere lla

sp. (1); Walliserodus? sp. (1); coni fo rm elements indet. (2); bl ade frag men t

of Plectodina or Aphelognath us (1).

Sam ple 82Bl 5-2 (34 m ).Aphelognathus cf.gigas Sweet (2); Belodina con­

fluens Sweet (2); Drepanoistodus suberectus (Branson & Mehl) (2);Panderodus gracilis (Branson & Mehl) (4); Plectodina cf. tenuis Branson &Meh l (5); Pb eleme nt indet. (2); blade frag ment (1).

Sam ple 82Bl 5-3 (43 m).Aphelognathus cf.g igas Sweet (1);Panderodus cf.feulneri (Glenister) (3); Phragmodus undatus Branson & Meh l (1);

Plectodina cf. acu leata (Stauffer) (1); Plectodina cf.tenuis Branson & Meh l

(2); coni fo rm elem ent indet. (1); blade fragment ind et. (2).

Sample 82B15-4 (45 m).Belod ina confluens Sweet (2);Panderodus gracilis

STI G M . BERG ST RO M

(Branson & Mehl) (1);Phragmodus? sp. (1);Pleetodi na cf. tenuis Branso n &

Mehl (1);conifo rm element indet. (1); fragment indet . (1).

Samp le 82B15-5 (54 m). Barren.

Sample 82B 15-6 (62 m). Belodina confluens Sw eet (2); Plectodina? sp. (2);

co niform eleme nts indet. (2); blade fragments in det. (5).

Samp le 82B 15-7 (70 m). Aph elognathus cf.gigas Sweet (1); Belod ina con­

f1uens Sw eet (1); Drepanoistodus suberectus (Branson & Mehl) (1);

Phragmodus undotus Branson & Mehl (l); Pand eradu s cf. feu/neri

(Glenister) (1);Panderodus gracilis (Branso n &Mehl) (6); P/ectodina cf. te­

nuis Branson & Mehl (1);P/eetodina sp. (4); con iform elements indet . (4).

Sample 82B15-8 (76 m). Aphe/ognathus cf. gigas Sweet (1); Panderodus

graci lis (Branson & Me hl) (3); bla de frag ment (3).

Samp le 82B15-9 (81 m).Aph e/ognathu s cf.gigas Sweet (1);Be/odina con­

f1uens Sweet (1); Phragmodus undatus Branson & Mehl (3); P/ectodina cf.tenuis (Branson & Mehl) (1); Panderadusgracilis (Branson & Meh l) (4);b la­

de fragm ents indet . (2); conifo rm element indet . (1).

Sample 82 B15-10 (85 m). Fragm ent of b lade (1).

Sam ple 82B15-11 (97 m). Be/odina conflu ens Sweet (1); Pan derodus cf.feu/neri (Gleniste r) (3); Phragm odus undatus Branson & Mehl (2);

P/ectodina?sp. (1); coni for m elements indet. (4).

NGU -BU L L 4 3 2 .1 9 9 7 - PAG E 69