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Vol. 34, No. 1-2

acta geologlca polonica

Warszawa 1984

Zechstein reefs of the Main Dolomite in Poland and their seismic recognition

ABSTRACT: Seismic techniques provide facilities for tracing reflections from high- -velocity anhydritic-carbonate sets sandwiched by low-velocity salts within· the Zech&teiJn deposilts ~Pol8J[lid. EslpeJciJa11y dmpol'ltanit for Zoohllte1n de~ts and· mast of all for the Mailn Dolomite (Ca2) :is the slope Off rthe Werra ,p/llllt:fomm extend!i!ng a.}ong the basin !Ill.aa.'gim IDur1i.DJg ~the M'llIi.!Il Doilomitte (Ca2) sedimentat.ion, the &1<>tPe of plaitform had separated

the

lagoon from If:he !ilniteriQI- i,>eiInIg 'lihen :the 'Sbarved basdln.

The bamier ,reef was oaiJncident wilth the S'lope, and Wlilth rCllPiJd trudkening oif the' overlyilng staIssIfiu.r.t Sal~. The ca:r1bolnate buiJIdups reIle!l'lreId to as "the ipd!nnacle reeils" arui "the aJtoll reedis" were deipoBtiJted in thiil·, vary starved basin. The best bydl'oc'arb<m pr'OS)peclts are believed to be tbe piJrlalru:le and aItoll ZO'IleS extandiln;g

ail"OUOO the entire basin.

INTRO[)UCTION

The Central European Zechstein Basin ranks amongst the world's major evaporite basins. The easternmost part of the Basin is situated in the area of the Polish Lowland (Text-fig.

'1).

The Upper Carboniferous coal ... bearing rocks, mor,e than 4.000 m thiclr 'Were deposited in parallic Variscan Foredoeep and covered by the terrigenic Rotliegendes- (Lower Permian) sediments constistinlg 'locaUy od: excelleint !l'eservoir

Tociks.

For many years these sediments were the most prospective sequence for

. hydrocarfbon ex:proration dn Europe . .ouring · the inundation by the lZech-

stein (Uppe'r Permian) sea the foredeep evolved. in to an epioontinental area. The sedimentation was developed in terms of fO'ur evaporite cycles, everyone of which was oomposed. of a sequence of shale, carbonate, an- hydrite and halite (Text-fig. 2). Three of ihe four cycl<>lthemes oontain carbonate members. The second cycle

c~bonates,

the Main Dolomite

(Ca2)

is of the highest imparta ' nce for oH and gas investigations.

DUring the last twenty years the Rmliegendes deposits proved to · be the most promising fO'r gas investifgations, While the oil was found in

6

(2)

82 L. ANTONOWICZ & L. KNIESZNER

Ca2 only. There are 28 oil and gas fields in Ca2, generally small in size.

The distribution of these fields is coincident with the lagoonal falCies.

The present authors' study concentrated on .the inteI1pTetation of reefs

in Ca2

from Jhe geologic and seismic (lata. In a, ccordanoe with a definition given by Heckel (1974), the term "reef" is used for a biHdup that displays evidence of (i) potencial wave resistance, (ii) growth in tur- bulent water

whi~h

implies wave resistance, and

(iii)

evidence of control

o

500 MILES

1-1 ---~I _--,I

o

500 KILOMETERS

PARIS o

PRAHA o

Fig. 1. Index-map sho!w:i,n,g' rela'lliOOl cxf hlle srtudy area to the CenJtral European Zlechstelilni BasiJn

Over the surrounding environmenlt .' The authors drawn their conclusions from the analysis and interpretation , of seismic data. The results compare well with lithofacies investigations (Bojarska & Rost 1974, Glowacki 1975, Czajor & Wagner 1973). The 'principles of this procedure were giV!en ealier

(see

An'tonowicz & Kniesrzm.er 19811), and ,Presently this way is applied to the investigation of the Polish part of ;the ZechStein Basin.

ThiS paper includes also the results of research conducted by the oil industry in Poland

(see

Antonowicz & Knieszner 1977).

RESULTS OF THICKNESS ANALYSIS

The thickness analysis is based on show 10.000 data derived from over a thousand , bo!l'eholes. Twelve thickness maps were designed for car'- bonate and for evaporiteuIl!its

Qf

,the ,Z· echJstein sequence as well : ' as for the clastic deposits of 'the Rotliegendes

(see

Antonowicz & KniesZner 1977). During these investigations; , there were recorded thick, : up .

to;

100 m and more;

acc~u1ations

of the carbonates of , the Zechstein Lime-

stone (Cal) alOlIlg the margin of the Zechstein basin, and there appeared

(3)

. ZECHSTEIN REEFS 83

the interdependence between the increase of the Zech.stein Limestone of

. (Cal)

thiCikness, and the zones of lack or consideralble reduction of the

sedimentary rooks of Rotliegendes.

Along the margin of the W errabasin, the sediments of this wry cycle formed a wide and nearly flat platform, ;up to 400 m thick, basinwarti limited by a steep slope.BesMes the reclal carbonates of the Z· echstein Limestone

(Ca1),

the platform comprises the sweUs of

A1d

and

A1g

(Text-fig. 3). Because the fillIng of the basin by salts interrupted, :the

1-_ _ _ _ _ _ _ _

T4g - TRANSITIONAL CLAYS

» >

> > >;> » > >

H H H H H

~ »»>.:»»»>

H

H

H H 1-1 H H H

A4g - lOP ANHVORITE

Na4- ALLER SALT 15

~

A4d - PEGMATITE ANHVDR.TE ;;J,

- - - -

- - - - - T4d - RED , PEtiTE

> . » » » »

» »

A3g - TOP ANHYDRITE

H 1-1 H H 1-1

~

H 1-1 H H H H H H H H H H H

Na3 - LEINE SALT

UJ

z

»)»»»>s»>

'>

'»»»» »> A3d -MAIN ANHVDRITE ~

Ca3 - PLATV DOLOMITE

- - - - - T3 - GRAY PELlTE

» » » » » » ; > A2g - TOP ANHYORITE

H 1-1

l-I

H H I-t \-j H

H H H H

H H H H

H H H H

H H H

~ » » » » » » >

H

HH

H 1-1 HH\-IH H H

Na2 - STASSFURT SALT

~

a:

::)

~

A2d - BASAL ANHYDRITE ~

rl~ ~--~

~ I»> ;»»;» »»» ~;,

» » » »

Ca2 - MAIN DOLOMITE STINt<SCHIEFER A1g - UPPER ANHYDRITE

H H: H H

H H H

~.

H H H H 1-1 H H H H H 1-1

> ?»»»»»>,>

~

~~:oo~·

» » » » ,

'~

"'" ..

',~

__

Na1 - WERRA SALT

-Cl

a:

A1d - LOWER ANHYDRITE ~

Ca1 ... ZECHSTEIN LIMESTONE ZECHSTEIN CONGlDME- T1 - RATE, WHITE SANDSTO-

NE, COPPER SHALE

(4)

L. ANTONOWICZ & L. KNIESZNER

Werra salts had not only compensated a deficiete of sediments in the centre of the basin but 'also the salts had reached theh- thickest develop-

·ment around the margin.

The existence of the platfonn determined the p'a'leogeomorphology and influenced conditions of the

Ca2

sedimenJtation (Text-fig. 4). The most prolific sedimentation 9f carbonates was concentrated in the shallow, warm, and aerated waters on the platform. In the marginal zone

of

the Werra platform, tb,eoonditioIl8 fOor barrier

,reef

development

of

the second cycle have existed. The thickness of

Ca2

carbonates in the zones of the barrier reef varies from 40 m up to 190 m. The barrier reefs are compo- sed mainly oifalga' l carlboo.ates.

On

their steejply dIpping iflaJrilks there

OCC'tlr

brecciated dolomites which aTe regarded as a reef talus. Between the barrier and the margin of . the basin, the lagoollla!l massive dolomites (in larg,e measure algal) created wide, flat bank reefs which reached a thickness of a,bove 60 m. The .sediments of

Ca2

thin out ba,sinawardly, off the platform edge, at a rather rapid rate. The c'al'fbonates that enend circumferentially around the basin are changing into marly carbonates and marly stinking sh~les deposited in a·

star:ved

basin.

The reef facies developed also oUltside

of

the Werra platform in the area .of the starved bBsin. Such roofs had grown on elevations of the sea bottom, igneous or . erodible in

~rigin.

According to the size of elevations and of the facies pattern, two types of reefs are recognizable: the pinnacle reeis, and the atol1Js with lagoonal fades

:in

their centre

(see

Text-fig. 3).

On the basinward slopes of

;the

barrier as wen

as

IoIf pinnacles and atolls, ItheI'le occurs an abrupt thidkmring od

~ Uip to

100 rn, which fOT'InS thick lenses elongated along the slopes.

In theoompensational phase pi the · Stass£urt cycle, the sa, lts filled the basin. The

pl'!imary

salt

thic~

albove the lagoonalfacies

of

Ca2 was as a rule

le~

than 100 m. The !rapid basinward thicke:ni:ng of theSe halite is coincident with the position

of

barrier :reefs. A very high rate of sed 1- mentation

is

supposed for the

Zechst€lin

salts, and according to

Ri~hter~

Bernbul"g (1972) it was up to 10 cm annually.

In contradiction ' to the Werra cyclotheme, the Stassfurtsedilmentation levelled the bottom of he Zecbstein basin. This was the reason why during the carbonate deposition of the next cyc10theme (Leine) a platform did not exist and the paleogeography

WaJS

simpler than during

pa~

in spite of relatively broad extension

of

the

~ of

the Leine cycle. The majority of reef :qanks of the Platy Dolomite

(Ca3)

located on the neu

arsho~

shallows were then occasionaUyeroded. The facies pattern of sulphate and salt member of this cycle was however similar to that of the older

0iIl€S.

In the Aller

c~le'

there is no evidence of carbonate sedimenta,tiOon.

The dominated clastic material marked the change of previous conditions

and finishing the Zech'stein sedimentation.

(5)

ACJ:A OlllOLOGICA POLONICA, VOL. If L. AN'l'ONOWICZ Br L. KNlESZNEB, 1'10. S

Block-<iiagram, to show the facies and thickness relationships in marginal parts of the Central European Zechstein Basin in Poland

> > > >

~4

::> ')

>

»:»

:> :>

> 1 7

~

H H 1-1

2 ~ - - - 5 ,:,. .... '1.,'1

.... \ - '/.

---- ---- ----

'F-;~~

8

~3 .: .-.::,:

• • I

.. :

: • • '

,,-:.,,:

~:

:,,:. ::

• •

6 ~ 9

o 5 MILES ,

o 5 KlLOMETERS VERTICAL EXAGGERATION x 2S

1 -

anhydrites,

Z - 811Jit8, 3 - carbonates 8IDd c:Jaye,y oQall'IboinaItlert. , -

reedls.

5 - clays, 6 - &aI1ldSt.oillles, 1 - ~era.1Ies, 8 --

etrus:iIves,

9 - reflectmll

(6)

ZECHSTEIN REEFS 85

SEISMIC INTERPRETATION

The Zechstein sediments may be divided, for purposes of seismic ana- lysis, into two grOlU!PS:

(i) rocks· 'With hiigh aoous.tiic iJn!pedeniCe (high-vellotClity

sets

of a!nihydritiJc--caroo.

nate sequences),

(ii) rocks WjJth lower llICbustdc i.mpederrwe (haMJbels, pO/tash salts an/d .pelites).

The present€d data of density and layer velocity relations (Table 1) were obtained fromborehole velocity surveys. Within the Zechstein de-

Table l'

Type of rock Layer velocity Density m/sec. G/cm3

anhydl'iteS 5800-6400 2.9

chlomites and doIomitic limestones 6200-6800 2.7

pl'lites 3300-3400 25

hotites 4100-4700 2.2

posits, the four sets with high layer velocity may be distinguished, as follows: 1 .-:..

Cal

and

Ald;

2 -

Alg, Ca2,

and

A2d;

3 -

A2g, Ca3,

and

A3d;

4 -

A3g

and

A4d.

In each cyclotheme, there appeal's a low-velocity pelitic memiber but its thickness (except the Red Pelite of the Aller) is up to few meters and therefore these horizons may be neglected. The cyclic sedimentation 01:

the Z€Chstein caused intercalation

of

high-velocity sets and the salts cha- racterized by low layer velocity. The seismic reflections are displayed on the boundaries between these groups of strata (Text-fig. 2; for the reflection coefficients

see

Table 2).

TalbIle 2

Boundary Reflection coefficient·

Anhydrite /pelite 0.36

Dolomite fhalite 0.28

Anhydrite/h<llite 0.27

Halite/petite 0.06

Anhydrite I dolomite 0.03

The most intense l1eflectiOllls appear on contacts of salts and/oc pelites

with anhydrites and/or carbonates, while reflections on contacts of salts

With pelites and anhydrites with ca1'Ibonates are of insignificant intensi-

vity (Table 2). Therffiore, the reflections at the tops and boIttoms of high-

-velocity sets are · dominant. The · model studies (Krnieszner. Poleszak &

(7)

86 iL. ANTONOWICZ & L. KNIESZNER

Skalny 1975) demonstrate how the seismic reflections are fOJl'lIIled and reciprocally interfered in the ZechStein

sequenc~.

This method helps also to define the limits of the thickness intervals of salt

~nd

anlhydrytic- -<Oarbonate sets to

0CCtlT

the dividing of .interferd reflections. For the salts, the dividing of refle!Ctions from the top and bot'tom of a layer

,is

noticable when thickness is above 60 m, while fOor anhydritic-carbonate is above!

80 m. On the seismic sections

~see

Text-figs 5-10), the following five' reflectors are oorrelated:

Z, -- bottom of A4d or bottom of Na4/ top of A4d

Za - bottom of N a3 / top of A3d Za - bottom od Na2 / top of A2d

Z'2 - bottom of AIg I top of NaI

Z'l- bdttom of AId or bottom

of

Call top Oof TI

OT

of the

:p!reI-

-Zechstein substrate.

Comparing the position of the strongest Zechstein reflectors (Za. Za and Z'l), their different recilprocal setting in different areas attract

t~

attention. In ne,arshore areas, dominated by lagoonal facies

of

Ca2, the reflections fram anhydritic-ca1"oonate sequernce between NaI and Na2 (reflector Z2) and between Na2and Na3 (reflector Za) we coextensive ' Text-fig. 9). In that way the inte)l"fered reflector Za-2 is obtained. The division becomes recognizable when the thickness

of

Na2 reaches 60 m.

Mter

crossing

the outer slopoe ~f the Werra platfmID', tOlg,ether' with the albrupt thhickening

of

Na2, the Z2 reDlector is rapidly moving away from Za (Text-figs 6, 8, 10).

The reflector Z2 (or Z,-a) :is separated from Z'i and Zi (Text-fig. 9) in the lagoona! area where the thic!kiness olf NaI d.s

UIp

to

300 !In.

'Whereas the NaI unit

:is

thin or a1bsent (in a ibarrier zone) it is COImpensated bY' thickening olf tihe w'erra ,anhydcltes. Along 'Wlith redtrettion af NaI, :the re- flecto,rs Zt and Z'2 are vanishing.

Outside the platfonn, the reflector Z2 draws near Zi, as a result

of

basinward thinning of the Werrasecllinents; so thait in the deeper parts

of

the basin only the interfered

~-i

is oibser:ved. The transitional zone cha-

racteristic by the reflector Z2 passing from' Za to Z'i marks the position

of the barrier reefs located along the edge of the Ca2 platform. This so-

..,called "position change zone" appearing

!()II1

:many seismic sections had

been plotted to form the map making interpolation and extrapolation

of

botrehole data possible. As mentioned above, in. th' e basin interior two

types of reefs were present: the atolls and the !pinnacle reefs. Their ver'-

tical . reliefs of the

~

reflector are up to 200-300 m. The pattern of atoll

reefs on the seismic sections (Text-fig. 8) is similar to that of the barriers

in contradistinction to the pinnacle reefs in which the Z2 reflector does

not reach the Za reflectOtr (Text-fig. 7). These twIO reflectOors above the

pinnacle-reefs are separated by several hundreds meters of Na2.

(8)

ACTA GEOLOGICA POLONICA, VOL. 84 L. AN'I'ONOWICZ

a.

L. KNIESZNER, FIG. 4

Paleogeographic model for the Main Dolomite (Ca 2) combined with the depth and range data

I

!'j'

! " . ,

l \

\...

...

\ c

... -.-... ... ,,_._._._._._.-

. -

. ...-. __ ,re,

"

"' J '- ... '.

~ \

,Y

I

/ / \

,Y

~.

1 \

----~ ~,.Y

2 \ .

, 3 "'

_"" 4 \

0;()

5 \ \ .

~

6 ' •

.pP~ ~B 1

1

i

,/

/ "

l._ i , ...

j

i I I

\ .1 \

".

¥?

100 MILES

~----~i~--~~i~----.i~i

\ I

"-.

\

50 100 150 I<llDHETERS

1 - prEIIJeIit.

raoee

of Ca2, 2 -

present

1'8IDge of Na2, • - t'biekDeaJ of Ca2 more

than

40 meters fIagorma!1 beIniks), , - barrier reef, 5 - piIIDaCle BIdd IUloll ~

8 - prEilerlt

defPth.

of buda1 at 'flop of Ca2 (COIlIbou:rs dn meterB below sea level), 'I - lines of seismic sec'bims A-F px'EBWted In Temt.-fiSs IhlO

(9)

ZECHSTEIN REEFS 87

Lowering of the basin bottom hacL taken place along the Variscan fracture lines approximately parallel to the basin longitudinal axis. The blocks enclosed between fracture lines had formed i basLnward steps sinking at a different rate (Text-figs 5-t6). The W'fJITa . platform deposits oonnected with uplifted blocks and "pOlSition change zone' s" are roughly fitted to tectonic displacements limiting the hltocks. PrOlbaibly all' the Werra aooydrites thickenings in the basin interi()[" (beside the Werra platform) have their counterparts in uplifted blocks of the Variscansub- strate.

The "position-.change zone" is mainly manifested as an abrupt thicke- ning of Na2 and hence it outlined a boundary of halokines:i.s effects in the thickness changes of two upper cycles and changes of Mesozoic re- flectors from continous to diScontinous. Sometimes, there is a possibility to note the conection between the "position change

~one'"

and the present-day morphology (especially

COUJl'Se'S

of the rivers). None the less these deperndences are often elusive and that active zone is only cleancut in two oldest cyclothemes.

SEISMlC DETECTION OF CA2 REEFS

There is a numiber of elevatiO'llS in the Z2 reflectors along the "posi- tion change zone", the inclinations

(}f

which are gentle on the lagoon- side (up to 3-4°) and steep (up to 11-14°) on the ba:sinward slope. The elevations are interpreted as culmination parits of the reem which have formed a barrier.

Under elevations interpreted as reefs, there are UlSUally . ohs1erved elevations in the Z'i reflectoc (Text-figs 7 and 10) . . The:i.r vertical reliefs are always smaller than that of ithe Z2 reflector. Up to now it was ndt proved by boreholes, whether they are real elevations or velocity ana- mali-es caused by th,e thickening of high velocity anbydrites of the Werra cyclotherne. In the lagOOlllaI area, the majority of elevations of the

Z~J.

!reflector correspond to the thickJening of Ca2 and to the depressions of the Z'1 reflector. This effect is caused by a lens-type accumulation of the Nal salit (Text-fi.g. 9).

On the basinward steep flanks of the reef elevations there is commonly ooserveci a weakening or complete disrwpbion of the Z2 reflector (Text- -figs 7-6 and 10). It may be caused by the facies interfingering of A2d with Na2 above the reef slopes which brings about the disperse of the eneI1gy. In 'Other cases high inclination an the front of the 'reef is respon- sible for the lack of reflections.

As a rule, the Z'1 reflector manifests a weaker zone beneath the Ca2

reeDs (Text-figs 7-8 and 10). The preSUIIlPtion is taken that the reason

was a

screeningeff>ect

of the Z'i reflector by the rough surface of the

(10)

88 L. ANTONOWICZ & L. KNIESZNER

Fig. 5. Seil3mic SelC!'t.iion. A (f.or IbCi11tion

see

Text-f'iIg, 4); expIanatiOlIl8 !in the

tex.t

Ftiig. 6. Seismic section B (for 10tCaildon

see

'l1ex.t-ftLg. 4); exp18lIl9.tiOIlJS In the text'

(11)

90 L. ANTONOWICZ & L. KNIESZNER

ssw

NNE

'

..

~=-~

...

~ : .. :1" :~::;;iii

::

,

,

,T

Fig. 9. Seismic sootrliotn E (for locatiOl[l see Text-:ftiIg. 4); explanatiioom liin· the texlt

Q ,MILES

6~---1~jK-'W--ME-T-JERS

Fdg. 10. Seismic :sec1OOn F (for locatdJorn see Text-fig. 4); explanoa.ti>olIlS in the text

(12)

ZECHSTEIN REEFS 91

top of the reef. The other reason may be the presence of tectonic faults or insignificant contrast

of

the acoustic im'pedence between the base of the Zechstein sequence and effusive rocks . of the Rotlieg.endes forming the substrate of the thiCk Werra anhydrites and Ca2 reefs. On some seismic liines the drape erffed occurs over the Ca2 reeifs (TeXJt-fig. 7). The other superincumbent reflectors in the Zechstein and Mesozoic deposits are displayed often by wide elevatiO'IlS occurring few miles basinward from the "position change zone". The origin of these elevations is pro- bably connected with movements of Na2 salts which crept down thereef '

slope (Text-fig. 10). , .

AlmJost all the elevalOOns recognized by sei:smia; in the Cd2 and in- terpreted as .reefs 'are associated 'W!i.th the positive,

resid'Wl~

' gravlity

ano:-

malies (calculate.d by Griffin's method) ranging from 1to 3.5 mg. Tha efieat

is

prestUl1ibly c8jUiSed not by a, body of the reef but by massi.fJS of heavy Wenra anhydrlte:s which formed' the base for development of the reefs.

HYDROCARBON PROSPECTS

The commercial production of hydrocarbons from the lagoon zone of Ca2 is practicaUy llimited to one field of oil of the average siZe. Almost all the bo,rehol'es which tested lagoonal carbonates commonly yielded traces of hydrocaribons but in less tham. commercial quantities.

Hydrocaa;boo ~ of the bam:er reef is far from IbIeIing clear. The bamer reef zone has been pierced by dm'llingsiin a few points. Traces of hyldl'1QcarboIliS were foru:nd IiJn all bareholes, bUJt '8!n clill prod'UlCfliJdn was obtali!ned iin t1Iwo bomholes.

The pirunao1e aIDd aJtoll-reef :heM extenldls. a.round :the ~e

Polilsh

part Off the

~tei.n Ba:sd!n ,(see TexJt-~. 4) • .AsI .the eXiPlOJ.'3Jti<llll dls. shiilf'tli:ng basilD:WMd more 8Ind more pi.n:nacles alntd aItol1s are reoognJized by seiIsmic method, aJnd recet1It[y some 25 such reefs were disoov~ed. ~ the g!l.'ea.rt dii/miens:iJ<xn of these ree:l's 8illid peI1feot hYich1oc8!l1bon seal pl'IOIVided by N a2 salts whlch SielCured the priorlity lof reedlsl iin lCatchiiJng the hyidrocadxllns: m.igrIaitiing f:rQm 'the oentrte of the 'basin, they have met all requiremerJl1;s of a trap, seal and source fo!l' the oil. J

The seilsmiJc a8i well as geOIWi~ dalta 'led lfiothediriD.ldlng an. the sitx Bii~capJt reef ibudldlliPS frQIllt:he basIIin: IDtei'tiJor and . the ex;k;tence of a~l reefBl 'Wats. confir- med. Commereiall prOld'll.CtiJQn of IOU was ~. (iJn care froan 11he ,reef tall$) ;in

the

Ubr1ee ofthean. Iln the tIh.ree remaJi!nIiJng reafis,· an 'eX'OeSS of the reseI'lVlaiir p~e

was

Ul1Jexpected1y ~tmlt.ered aJnd the boIrehooES' were alba!ndOnied. Here, the gas had III high con!tXmt <Xf indlt.rogen wdlth aidlmix1lure Off HaS, burt; 1lhe healvy !hydrolcaI1banB OioouTrence :indicates: the ~lIity od: the oil prelsieince ulllldern:eath .

. Concern.ing the l"eSeTVoir· CIOIniCIitiOOlS, fjgShldlty is of gIl"eat Iim(poirtalnce. Feme<!

d'o'lmiJtes exte,nid alolIJg zaruels of ilnitenls:L've /tJectDwc mOivemEm!ts, of Eairly and Late Oimmerian phases. These ZOI!leS are readily :ilnJterpreited frolm ~ic dialta. The areas Where they cross the reef . .trends are of the greatest pptential

.

for, oil and gas prospection.

(13)

iL. ANTONOWICZ & L. KNI1!liSZNER

CONCLUSIONS

The reflection seismic metthod together with facies and thickness analysis provide an effective explaratiO'Il tool for the rect>gn!itiO'n of reefs

OCCUlirEmce.

The reefs of the' Main Dolomite

(Ca2)

were devololPed in the marginal part of the Werra platform; (harrier reef) as well as in the starved-basin inte'rior (atoll and pinnacle reefs). Difielrentiated morphho:- logy produced by pre-Zechstein tectonic and volcaDlic processes

was

responsible for developmenrt; of the pinnacle and atoll reefs belt hi the Zechstein Basin.

Except foc paleogeomarphologlic analysis, direct reflections frQIll the tops of the reefs, changes f.rom continous to discontinous within the Zechstein and Merow.ic strata, and presumed velocity anQIllaHes should be used to guide drilling. The seismic detections performed for the Polish part

of

the Zechstein Basin dlisplay immediate applircatiom. to' oil and gas explor:ation and may be used also in other parts of this Central European Basin.

Ack.nwwledgermervts. The IaJUtthexrs offer their thanks to JPirdfessor S. WidiawJarz for helpful <liJSlcUSiSlilolOO, to Z. Korab, DWectbolI" of the "GeOIIl.a:flta" En/teTprise, anld E. Pol.

1~, Director of the-"Geaf.i.7.ylKa" Elnte~e, for pEII'IXl.issIion to pub1!Lsh the oontent of thrlis (palpe!r.

The authors are a'lSo indelbted to their coUe:guelsl :too IlII.llIIlerO'US to man.t:iJoIn who COIIl!I;,rlibu.ted to thils ipa!per by S'UiP'Plyiltlg ,the geological and geqphY'sLcal k:nOw-ho.w, palI'tly at least lisltetdiln the 'IlalLorwting It''e.fere.rroe.

"Polskie G6rnictwo N aftowe i Gazownictwo"

Geological Enterprise GEONAFTA, ut. Krucza 36.

00-522 Warsaw, Poland

(L. Antonowicz)

'REFERENCES

"Polskie G6rnictwo Naftowe Gazownictwo" GEOFIZYKA,

ul. Chrobrego 50, 87-100 Toru:ti, Poland

(L. Knieszner)

ANTONOWroz L. 11977. RJOila wa!mmlk6w ~eogJeomO!I'fullogicZil1Y,ch w sedyunenta;cji

<:eehsztyils!kdej (in Polish). Materlilaly z Kontferencji geoilogiJC:mej pIOSw!i~otne:j

pas7:uki:W3,nJi:om w utwo.rach peamu. Zielona G6ra..

& KNJ;ElSZNERL. 1975. 0 raJfuk:h dolomd,'Ilu glbwtne:go w PoIsce (in Polish).

Nafta, 3/4, 11a-;1~1. Krakaw.

- & - 1977. Ra:fy oedhls7JtyDsik.ie w ~e i wylblr~ m.etody iJch poszukiwamia (in Polish). Pram dak1larska - maszy:nqpis AGH - K:rak6w.

- & - 1981. Ree:f2lO1llJes 0If 'the Ma!iJn Dolomite, set 0'UIt OIIl; ,the bash; of paleogeo- morphologic analysis and the results of modern seismic techniques. Pro,:.

Intern, Symp. on Central European Permian, April 1978, 35&-.36111. WalI'SZawa.

ANTONOWICZ L., KNIESZNER L. & NOWOTARSKJ: C. 1974. KompleksolWe me- tody geO!fi~Y;C7J[lych badan w celu wy;kxywama Sltrukttur W UItwoll"ach permu (in Polish). Mart.erialy z SemilIlari'UlIIl 1POISwti.~o po\Szukiwaniom w Ultwo- rach permu. Zd.elona G6ra.

BIRECKI T. 1973. Geologiczne warunki wyst~powania zl6z gazu ziemnego i ropy naftowej w ·0ISaidacll permu lInono~ pr~!UdeclciJej. Materialy archiwalne ZOO Genanafta. Warszawa.

(14)

ZECHSTEIN REEFS 9-3

BOJARSKA J. & ROST U. 1974. Mapa mi~ZszoSci i lltofaeji dolomitu gl6wnego (S'tlalSsfurt) w oIbiszaJrIaJch przygranicznydh PRL i NRD. Ma:teriary arclxi.wa1ne ZOG GenoOOifta. Warls'ZQIWa.

CZAiJOR E., & WAGNER R., '197'3. Typy ge!neltycz.ne skal oraz mikrafacje i paJeo- . grafia wapi.eniia ceehsi7JtyDs:k:iego. (Cal)

w

SIIn'efie Koszal:itn.a'---Choj.ri!i.e. Kwart.

Geol., 17 (3), ~1-486. Warsmwa.'

DEPOWSKI S., PERYT T. M., PIl\TKOWSKI T. S. & W AGNER R. 1978. S~­

mentaeja i pialeagJeografia oeohsz.tyilSkJiego dolJQmitu gloWll1ego a jego ropo- i g~oSn.osc. Przegl. Geol., 3, 141-;146. Wars,;z.awa. _

DYJACZYNSXI K. & PIELA J. 1974. Uwaga; 0 wllIUiIlkach akumulacjli. TOfPy naJito- wej lOa zioiu Sul~ na ,tIe paJeQgeografii dbsz.a!ru. Materdaly z SemilnJa:nium poL!!iwJE:COIllemu poozU!k.iwaIl.'i.ron w '1.l'twomch permu. Zie10na G6ra.

GLOWACK'I E. 1975. Mapa liltoLogiiJczno-facjalloo dolooni.tu g16wnego w Polsce na poldls'talWlie Ibatdan petro~ych. Ma;terialy 8IVohiwalne ZOG GeoiIlaflta. WaT- szawa.

GlRlACEVISKlLJ M. !M., KfU12lNI1IElCOV Jl. J. & U\IJ.MlISElK iD. 1009. aarierny~ rid' cech- sitejna - 2 'wySiotk~yj OIbjekJ1; P~OIV oofti. i gaza

w

PIoIl.se i GDR N eftigaz., Geol. i Geojiz., 5. ' '

HECKEL P. H. 1974. CarlloanaJre bWldu:ps ID the ~oklgix: :record Reefs ID. tIiJme and space. Soc.

of

Econ. Pa!eont. and Miner., Spec. Pub!., 18.

HOEPT M. & HERRMANN :EL 1'977. Zed.tilclJ.rirllt fUr An!1leWla'Illdte GeoOOgie, 23 (8), Berl:in.

KARNKOWSKI P. 19'7'3. Pr7.egIl~d pempektyw poozukliwafl I"<l(py nai'towej i gazu :z:i.emnego

w

PJOlis,ce. Biu!. Inst. Geo!., 264, 3111...;329. WllIsza.wa.

KNIESZNAR L. 1977. WybralIle zagadindernd.a rozpo;z:nawaJIlda metodami ,geo.fJi.zycz.n.y- md form rarf'owych w ceclhSztyIDe polui<:linIDwo..,zaICIbodJnjej PolSiki Ma'terialy z K.oinferenJcji geologji.cmej poSw:i~j pooZUiki!wallllilOlm w utworacl1 permu.

Zilel<ma G6m.

& ANTONIEWICZL. 19n Rafa bal"i.erowa dollQlIIlliltu g16wn€go W Polsoe 2la-

chodniej.. Nafta, 4, 145~150. Krak6w.

, POLESZAK E. & SKALNY A. 1975. Wply!W miqZs~oSci ewapora,tOw ce.oh- s:z:tynu tna fOlI"IXlO'Wan.ie sii~ odIbi.c sej5miC'2;IlYlClh. Nafta, 7, 278--.285. Kra:k:6w.

KORAB Z. 1966. Cechs7Jtyfls'ki poziom bitumiczny na man.oklitnJie przed8udeclciej., Z Igeologtlli Ziem Zaohodm.ich, 381~398. Wroclaw.

LENK L. 1973. Mapa prognoz ;rOfPo-~OI!lIosI!lOSci da.loroitu g16wnego Ca2 IlIa Qbsza-

rze

PoIski. MaterJaly arc.hdwalne Imstytutu NIafOOweg)o. Krak6w.

MROZEK K. 1979. &pecyfika wEglatnowej bariery Werry 'w obszar7Je zlmowym 0sItrze!Sz6W\--fWielufl. Sprawozdatn.i.e z pOiSded:zen ~omisji NaukOlWej PAN, ze- SiZyt 2. Wars.zawa.

POLTOWICZ S. '1.971, Bartiera onkoliiawa w dolmiiaie gloWll1Yffi wschodn;iej cz~Sci

monoklilIly przecl!SUldeckliej. Geofizyka i Geo!ogia Naftowa, 4-5, 15-19, Krakow.

PROTAS A. 1974. Oharaiktery':styka l!iJtOlf.acjalna dblotmitu gl6wneg;o w l"ejlOlIlie Woli-

ne.

n.a po.clStawie badafl petrogratilczn.ych. Ma'ter1ialy z SemiJnaxiUllll poswi~

~go poozukli:wantiKlm w utworaK!h pennu. Zielonla Gm-a.

RICH'11ER ... BERJN.BIUlRG G. SeddmeiIlto1ogical problems, of saline deposits. 'Prroceeditngs

of

the Hannover Symposium, May 196B, UNESCO. 33-40. Paris.

SIKORSKI B. &

at

H175. Balcfutnia sIIn'ef razfO(pOlddblnyoh rw utworach cechszty!Illu. Ma- terialy archiwaline PGMliIL GN - ToI"llil.

SOKOLOWSKJ: J. 1967. ChariakterySltykageologicmlIa i s:trukturalna obiszaru przed- slIideck.iego. GeoZ. Sudetica, 3. Wroelalw.

STEMULAK J. lQ63. W,plyw facj:ii g16wnego do1amitu cec~yil:skietgo na jego TO-

pogazo:noSnioSC. Przegz' Geo!., 4, 196-200. WaI'!S:zawa.

SURMTAK

w.. ,

SZELOCH W., ZOLNlERCZUK T. & & ZURAWLK J. 1974. K.Qm- pl~a anaLi'Za wy.ndk6w lbadan st1'U!k!liu;ralnych, litologi.cmyc.h i geocheanitcz- nych dla okreslenia optymalnych stref dla akumulacji bitumin6w w dolomi- de glbwtnyu:Il w zaclJ.odni~cz~ci motnakliny pmedis,ooecltilej. lMa,terialy z Se- mmarium tpOSwif:canego pOISzuJk!iiwamom w \lltw!o!ra.ch pennu. Ziekxna G6ra.

WDOWIARZ S. 1956. P1'IO>bletmatyka ropy narfitowej w Balscie ipMnocnej i srodkowe'J.

Przeglqd Geo!., 1~, 541-544. WatI'szarwa. '

(15)

94 L. ANTONOWICZ & L. KNIESZNER

L. ANTONOWICZ i L. KNIESZNER

CECHSZTYN'SKIE RAFY DOLOMITU GI.OWNEGO W POLSCE I MOZLIWOSCI ICH ROZPOZNAWANIA METOD1\ SEJSMICZN1\

(StresZICZenie)

W pralcy przedls!laiWu.Oll1y zo.stall plrQlbl.em sej.simlicrmego rozpo.z.nrunia osa.d6w ,do- lomi.tu g16W!Il.ego pol:sikiej c~CIi. baIlenIu cec~lk:ieIgP (fdIg. 1). W wyrnlw alnaili- zy nUqZszoSci o~ !na da:nYlCih z ~olo ItYlSli.!I;ca ot'Wloir6w Wlier;t.ni.czyeih sltwierdzo-

IliO, i2; warunki sedym.entacjd do1olmiltu gl6W1negozdeterm1ll:lidwane byly dis,tni€ll'liem platformy Werry okalajqcej caly basen. Na kraw~dzi tej platformy istnialy wa- ruinki dio tworz.enlia sd.E: mfy barileroW'ej (jlig. 3). W wy;nddru badatt prowadzanych metQdq sejs!IDiki re.flek!Syjnej okreS1oloo ulod;elnie

gramc

ceClhsztynsikikh zwdqzaIlyeh z paikieitami iW~glaJIllOfWO·anihydrytowymd (:talb. r-~, fig. 2, '5--110). AlniailJiza rocldadu miqZszooc:i w IPOwtiqzanliu z wYJ(liilkalma 1Jniterpreltacji malterlia16w sejlsrnIDcznych POZW1O-

lila odtwclrz,yc przebieg rafy barieroM1lej dolomi>tu gl6wnego (fJiIgi. 4). W celIJ.ltraJnej

cz~sd basaruu, ([la lokailnyeh POIdlnJie.sdelndaiCh dI1ia oSlaid!2liay sIi~ anhydryty We:rrr:y o znatcznej miqZls(ZloSiai, na ldi6rych rozW'iui~ly s~ rafy alflowoN're i rafy typu wdeZycz- kowego (ang. pinnacle reefs). Zldap.ie1ID autqr6w mjbardlzli.ej o/biecUljqCe, z punlktu widzenia pos'zukiw:aii. bliltUiIllliJn6w, sqpiCljeidylnicze oIbi;ekty Tlatfowe w ce:o(trtLlnej cZE:sC'i ba!sEItlu.

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