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Rakvere Stage

ID: 34

General info

Unit nameRakvere lade
Unit nameRakvere Stage
Belongs toVinni Subseries
Overlain byNabala Stage
OverliesOandu Stage
Typechronostratigraphy
RankStage
Scoperegional
Statusformal standard
AuthorSchmidt
Year1858
EtymonRakvere, town (E)
Age top (Ma)452.00
Age base (Ma)453.20
AgeKatian
Age referenceCooper & Sadler, 2004
IndexE
IndexO3RK

Lithostratigraphy

Stratigraphy
Piilse Member
Tudu Member
Kiideva Member

Stratotypes

TypeLocalityDepth (m)ReferenceRemarks
holostratotypeRägavere quarryRõõmusoks, 1967
hypostratotypeTõrma 5 borehole11.90..26.93Põlma et al., 1988

Typical rocks

Number: 311-70
Number: 311-75

Chemical composition and other properties

Variableminavgmaxstdcount
Al2O3 [%]0.040001.198657.280001.3918844
As [ppm]-1.80000-1.80000-1.800000.000001
Ba [ppm]0.004154.0519044.5000012.7908113
Br [ppm]1.800001.800001.800000.000001
Calcite [%, calculated]2.0600079.4100896.9600022.88733114
CaO [%]1.7000046.5393956.8800010.58817183
Ce [ppm]-23.10000-23.10000-23.100000.000001
Cl [%]0.000000.034020.150000.0336534
Co [ppm]1
CO2 [%]2.8000039.0937849.940008.15464132
Cr [ppm]-1.300006.4714210.000003.3788017
Cu [ppm]4.700004.700004.700000.000001
delta13C [‰]-0.660000.983242.250000.78770120
delta18O [‰]-6.66000-4.67068-2.940000.77010117
Dolomite [%, calculated]1.020008.7622192.1100015.12296113
Dry density [kg/m3]2408.000002632.541662902.00000101.1139948
F [%]0.050000.050000.050000.000001
Fe2O3 [%]0.100001.063156.720001.4988438
Fe2O3T [%]0.860001.190001.520000.330002
Fe2O3total [%]0.180001.527479.480002.3087974
FeO [%]0.010000.306452.770000.5951948
Ga [ppm]2.300002.299992.300000.000001
Ge [ppm]1
Grain density [kg/m3]2587.000002723.729162940.0000076.1748948
illiit [%]83.0000085.3333388.000002.054803
Insoluble residue [%, calculated]1.1200010.5195959.5100010.8818250
Insoluble residue [%, calculated]0.0000014.3261594.0100023.2103765
Insoluble residue [%]1.900005.8554429.800004.7167168
K2O [%]0.040000.569902.690000.5841844
kloriit [%]12.0000014.6666617.000002.054803
La [ppm]9.200009.199999.200000.000001
LOI [%]36.4800040.9807644.000001.7881313
LOI920 [%]41.5600041.5600041.560000.000001
MgO [%]0.050002.5646420.030004.46024181
MnO [%]0.000000.119980.790000.1900344
Mo [ppm]1
Na2O [%]0.000000.060570.260000.0548236
Nb [ppm]2.600002.600002.600000.000001
Nd [ppm]-19.70000-19.70000-19.700000.000001
Ni [ppm]0.000000.000000.000000.000001
P-wave velocity [m/sec in dry sample]3522.000004972.757576389.00000691.8544233
P-wave velocity [m/sec in wet sample]3319.000005223.056826478.87000643.2223541
P2O5 [%]0.000000.019240.130000.0248044
Pb [ppm]6.500006.500006.500000.000001
Porosity [%]0.200003.3560412.900002.3295148
Rb [ppm]3.700003.700003.700000.000001
S [%]0.000000.083580.360000.0746334
Se [ppm]1
SiO2 [%]0.160004.8320427.190005.4437344
Size fraction 0.01-0.002 mm [%]24.0900035.6452352.650006.8122821
Size fraction 0.05-0.01 mm [%]2.7600023.4987435.810009.2356824
Size fraction 0.1-0.05 mm [%]0.200007.1161923.820005.5645921
Size fraction 0.25-0.1 mm [%]0.100000.700001.700000.711803
Size fraction 0.5-0.25 mm [%]1.000001.000001.000000.000002
Size fraction <0.002 mm [%]2.9400031.9161959.4100010.6099321
Size fraction <0.01 mm [%]81.6000088.2333392.600004.768183
Sr [ppm]351.60000351.60000351.600000.000001
SUM [%]98.1607299.69673100.000000.6569412
Th [ppm]1.200001.200001.200000.000001
TiO2 [%]0.000000.051860.370000.0721944
U [ppm]1.600001.600001.600000.000001
V [ppm]-0.300002.100002.500000.9797917
W [ppm]3.000007.5000012.000004.500002
Wet density [kg/m3]2517.000002666.020832905.0000086.9917348
Y [ppm]2.500002.500002.500000.000001
Zn [ppm]5.2000010.4000017.000004.917993
Zr [ppm]11.0000011.0000011.000000.000001

Specimens in collections (approximately): 4487

Samples in collections (approximately): 1073

Thickness map (partial data only)

Localitybase, mtop, mthicknessreferencepreferred
Palamuse borehole 200.60 162.75 37.85 Kõrvel 1963 1
Soovälja K-1 borehole 133.60 105.10 28.50 Põldvere, Anne (koost), 2002 2002 1
Alatskivi 422 borehole 190.10 164.00 26.10 Kajak 1974 1
Kõrgessaare borehole 44.95 20.82 24.13 0
Virtsu 360 borehole 222.60 198.60 24.00 Meidla, 1996a 1
Orjaku borehole 129.30 105.90 23.40 Meidla, 1996a Meidla 1
Orjaku borehole 129.30 105.90 23.40 Meidla, 1996a 1
Männamaa F-367 borehole 138.20 115.30 22.90 Põldvere, Anne (koost), 2008a 1
Tareste F-352 borehole 48.80 26.00 22.80 Suuroja, Kalle 1991 1
Kassari F-371 borehole 123.60 101.20 22.40 Suuroja, Kalle 1988 1
Kaleste F-356 borehole 69.70 50.80 18.90 Suuroja, Kalle 1991 1
Sõru 400 borehole 168.70 150.40 18.30 Kala, E., Kajak, K. & Kajak, H. (kompleksne geoloogiline kaardistamine 1:200 000) 1971 1
Rapla borehole 125.50 108.25 17.25 Põlma, 1972b Põlma 1972 1
Kerguta 565 borehole 121.80 106.80 15.00 Põldvere, Anne (koost), 2006 Põldvere, Anne Estonian Geological Sections Bulletin 7 2006 1
Taga-Roostoja 25 borehole 37.20 23.70 13.50 Põldvere 1997 0
Äiamaa borehole 174.20 162.70 11.50 Põlma 0
Valga 10 borehole 383.00 373.50 9.50 Põldvere, Anne (koost), 2001 1
Velise V-97 borehole 157.80 149.80 8.00 Suuroja, Kalle 1991 1
Võhma borehole, Viljandi County 221.75 214.50 7.25 Põlma 0
Põltsamaa H-163 borehole 209.10 201.90 7.20 Põlma 1984 1
Laeva 18 borehole 234.20 227.60 6.60 Nestor, H., päevik 23 0
Eikla 508 borehole 296.40 290.30 6.10 Kala et al., 1967 1
Apraksin Bor 17 borehole, Leningrad Oblast 90.00 84.40 5.60 Põlma 1984 1
Pärnu 6 borehole 325.00 320.10 4.90 1
Kingissepa GI borehole 366.80 362.80 4.00 Põlma 0
Viki borehole 327.50 323.60 3.90 Põldvere, Anne (koost), 2010 1
Otepää 2 borehole 434.30 431.00 3.30 Sarv 1
Laeva 13 borehole 215.40 212.20 3.20 1
Kaagvere 1 borehole 257.40 254.45 2.95 Meidla, 1996a 1
Karula 320 borehole 396.20 394.00 2.20 0
Tartu 453 borehole 288.40 286.50 1.90 Põldvere, Anne et al., 1998 1
Ohesaare borehole 464.45 462.65 1.80 Põlma 1
Mehikoorma 421 borehole 284.80 283.40 1.40 Põldvere, Anne 1
Abja 92 borehole 398.10 396.90 1.20 Kajak 1969 1

Description

Rakvere Stage

L. Hints & T. Meidla

Original text from: Raukas, A., Teedumäe, A. (eds). 1997. Geology and Mineral Resources of Estonia. Estonian Academy Publishers, Tallinn. 436 pp. ISBN 9985-50-185-3. Available online at: sarv.gi.ee/geology.

The “Wesenbergsche Schicht” by Schmidt (1881) corresponds roughly to the Rakvere Stage in nowadays understanding (Männil 1958b, 1963a, Kõrvel 1962, Põlma et al. 1988). In northern Estonia, the Rakvere Stage forms the lowermost, relatively thick part of Late Viru and Harju pure micritic (aphanitic) limestones which intercalate with more or less argillaceous varieties. The cycles of different lithotypes generally constitute distinct lithostratigraphical units (Põlma 1982, Hints et al. 1989), whereas the clayey parts of the cycles are characterized by the appearance of abundant new taxa .

The Rakvere Stage consists of the Piilse and Tudu members (Kõrvel 1962) which form the main part of the Rägavere Formation. The stage is at its thickest (28 m) in western Estonia (Fig. 52) and it thins notably in the southeastern direction. The lower, Piilse Member with a thickness of up to 27 m (Rõõmusoks 1983) consists of pure, in places dolomitized micritic limestones with a low content of terrigenous material (3 - 9%) and skeletal sand (less than 5%, Kõrvel 1962, Põlma et al. 1988). The member is characterised by a distinct pyritic pattern, following abundant burrows in the former sediments. The upper, Tudu Member is up to 10 m thick and differs from the Piilse Member in the higher content of skeletal sand (commonly 15 %, Põlma et al. 1988), in the occurrence of thin, up to 3 cm thick kukersite layers and rare and weakly developed pyritic patterns.

Southwards the limestones of the Rägavere Formation become more argillaceous and in southern Estonia they are supposedly replaced by the carbonate marls of the Priekule Member in the upper part of the Mossen Formation (Männil & Meidla 1994, Meidla 1996). On the basis of chitinozoan distribution (Nõlvak & Grahn 1993) it is supposed that in some places (Ruhnu and Ohesaare cores) the Rakvere Stage is missing.

The data on the distribution and composition of macrofossils in the Rakvere Stage, particularly in the Tudu Member is scanty due to relatively few outcrops. The Rakvere Stage with the relatively sparse macrofauna of bryozoans, brachiopods and trilobites is characterized by frequent and diverse association of calcareous algae (Cyclocrinites, Rhabdoporella etc., Kõrts et al. 1990). From the Rakvere Stage up to the end of Ordovician, calcareous algae and their fragments dominate in the composition of skeletal particles (Põlma 1972, 1982) where they may account even for 97.6%.

Unlike macrofossils, the ostracode record of the Rakvere Stage is rich, comprising more than 80 species (Meidla 1996). Several distinct associations have been recorded in the lower part of the stage corresponding approximately to the Piilse Member of the Rägavere Formation (Meidla 1996, fig. 47). Valuable is the ostracode record of the upper part of the stage which contains only sparse macrofauna. This interval, nearly equal to the Tudu Member, corresponds to the Daleiella admiranda Subzone (subzone of Daleiella sp. n. in Meidla & Sarv 1990, Table 10), a range zone prominent in the sections of northern and central Estonia. The appearance of several long-ranging taxa, such as Steusloffina cuneata (Steusloff), Medianella blidenensis (Gailite), Pullvillites laevis (Abushik & Sarv ), etc., has been recorded within this interval (Fig. 50).

The lower boundary of the Rakvere Stage is lithologically more or less distinct in northern Estonia where it coincides with the pyritized discontinuity surface on the top of the Tõrremägi Member in the lower part of the Rägavere Formation. The appearance of several new brachiopods, including Microtrypa estonica Rõõmusoks, Platystrophia lutkevichi satura Oraspõld, P. quadriplicata Alichova, Sowerbyella (Sowerbyella) raegaverensis Rõõmusoks, Vellamo wesenbergensis (Pahlen) and trilobites Chasmops wesenbergensis (Schmidt), Encrinuroides seebachi (Schmidt), Pharostoma pediloba (Roemer) and others, above this boundary shows the renovation of faunal associations. However, macrofossils are very scarce, particularly in core sections, and cannot be used for the purposes of detailed biostratigraphy. The same applies to ostracodes, because most of the species characteristic of the Late Ordovician ostracode fauna appear below this boundary, in the Tõrremägi Member of the Oandu Stage which represents a facies similar to the Rakvere Stage. Also the zonal chitinozoa Fungochitina fungiformis, characteristic of the Rakvere and Nabala stages, appears in the Tõrremägi Member. The suggestion to include the Tõrremägi Member to the Rakvere Stage (Meidla 1996) follows partly the earlier wider interpretation of that stage, according to which the Oandu beds by Öpik were included to the Rakvere Stage (Jaanusson 1945, Alichova 1960).

The Rakvere Stage corresponds roughly to the lower part of the graptolite Pleurogratus linearis Zone and the chitinozoan Cyathochitina angusta Subzone of the Fungochitina fungiformis Zone (Nõlvak & Grahn 1993, Table 7).