LITHOLOGY OF THE KALLAVERE FORMATION ON THE NORTH ESTONIAN KLINT (Part I - Paldiski-Kunda area) HELJO HEINSALU AND REIN RAUDSEP Heinsalu, H. and Raudsep, R. Lithology of the Kallavere Formation on the North Estonian Klint (Part I- Paldiski-Kunda area). - Bull. of the Geological Survey of Estonia, 8/1, 20-31. In North Estonia the Kallavere Formation corresponds to the Cambrian-Ordovician boundary beds, the major part of which belongs to the lower Tremadoc. The stratigraphical range of the Kallavere Formation is variable: in the western part of the klint (North-Estonian cliff) it represents the lower half of the Pakerort Stage, in the east the whole stage. The Kallavere Formation is subdivided into five members: Maardu, Suurj5gi, Katela, Rannu and Orasoja. Three members - Maardu, Suurj5gi and Katela - occur in the western klint area, the eastern boundary of which coincides with the surroundings of Kunda. Part II of the article (eastern part of the klint) will be continued. Key words: lithology, Obolus sandstone, Kallavere Formation, Cambrian-Ordovician boundary beds, Estonia. Heljo Heinsalu: Institute of Geology, Estonia Avenue 7, 10143 Tallinn, Estonia. Rein Raudsep: Geological Survey of Estonia, Kadaka tee 80/82, 12 618 Tallinn, Estonia INTRODUCTION brachiopod material in the rock, however, is revealed by the content of Pp determined by chemical analysis. Usu­ In the western klint (local name for cliff of the bedrock) 5 ally Pp 5 makes one-third of the composition ofbrachio­ area the Kallavere Formation forms the lower part of the pod fragments (Figs. 2-5). Pakerort Stage, the Tiirisalu Formation corresponds to the In the composition of the Kallavere Formation upper part. Owing to the variable lithology of the we may distinguish three major lithological components: Kallavere Formation, as a result of the studies by differ­ 1. brachiopod coquina ("Obolus conglomerate"), 2. quartz ent researchers five members - Maardu, Suurjogi, Katela, sand(stone) with interbeds of dark graptolitic argillite and Rannu and Orasoja- have been distinguished in it in the 3. quartz sandstone enriched with phosphatic brachiopod entire klint area (Miiiirisepp, 1958a; 1960; Loog, 1964; detritus of small size. The first two components occur in Heinsalu, 1981; 1987). The Maardu((\-0 k/M), Suurjogi 1 different proportions in the Maardu Member, the third (O,kl S) and Katela (0// K) members are distributed in component, however, is known as a "detrital layer", dis­ the western region of the North Estonian Klint, consid­ tinguished as the Suurjogi Member in the section of the ered in the present paper. The eastern boundary of the Kallavere Formation. region coincides approximately with the Toolse-Kunda district. The Rannu((\-0//R) and Orasoja (O,kl 0) mem­ LITHOLOGICAL TYPES OF SECTIONS bers occur in the eastern part of the klint, between Kunda and Narva. (G -O klM) Maardu Member 3 1 The present article bases on the data of detailed lithological investigations of 15 differently exposed sec­ In the North Estonian Klint sections the Maardu Member tions, located on the North Estonian Klint (Fig. 1). The is generally characterized by quartz sand- or siltstone investigations were conducted already years ago, but the containing detritus or whole valves of inarticulate phos­ results have not been properly published yet. Field stud­ phatic brachiopods. There occur always also interbeds of ies have been conducted by the same researchers during dark kerogenous argillite (Dictyonema shale) in different a short time interval and the analysis performed by the numbers. In the sections east of Tallinn a layer of bra­ same analysts in the laboratory of the Geological Survey chiopod coquina has been recorded on the base of the of Estonia, using the same methodology. All this allows Maardu Member. of good comparability of the results. The granulometric The thickness of the member ranges from 0.5 m to composition of rocks was determined by the so-called 5.4 m, most often from 2 to 3 m. quartz method, which lies in the treatment of rocks with Detailed investigations have revealed high lateral aqua regia prior to analysis (Kazakov, 1957). In the present variability of the lithology of the Maardu Member. In the context this means the dissolution ofphosphatic brachio­ western part of the North Estonian Klint, four rather dis­ pod valves and their detritus. The content of phosphatic tinct types of sections (I-III and III/IV) can be distin- 20 I LITHOLOGY OF THE KALLAVERE FORMATION ON THE NORTH ESTONIAN KLINT (Part I - Paldiski-Kunda area) GULF OF FINLAND KEHRA QRAKVERE 0 TAPA 0 S2 en in a;w w '.2: en_, '.2: 0 ,0z Q Om 2 4 6 8 10 Fig. 1. Location and schematic cross-section of outcrops with lithostrathigraphical units of the Kallavere Formation. 21 ---.--- - TREMADOC TREMADOC TREMADOC TREMADOC TREMADOC Series : LOWER LOWER LOWER LOWER LOWER Subse~s~ Ulgose I Kollovere TOrlsolu TOrlsolu TOrisolu TOrisolu TOrisolu Formationi £Jul fl Kollovere !"I Kollovere !"I Kollovere Kollovere " " I Moardu Suur- 0 Suur- To~o- Suurj6gi 0 Moordu Suur- To~o- Moardu Suurj6gl 0 Member, 1%?u · Moordu sou Moordu 1%?u · sou 1%?u · j6gi j6gi j6gi 8,-0,klM €30,k/M €,-0,k/M G,-0,k/M O,ktS O,trT Index O,k/S O,trT O,k/S O,trT O,k/S 0,trT 83 0 1k/M O,k/S O,trT :':. ~ ~ .. .. g: "' g; "' 21 tel Thickness ~ 0 0 0 ~ "''" ~ 21 r I :::v (/) -; 5= C C c:...., ~ 0 0 0 :J :J C cii" 0 co 0. :J c 0 L < 0 "Q_ C 0 :::, -< ~ CD ~ ...., 0 ~ 0 (fl 3 Sl'I ? D ~ 0• 3 3 cii" "Q_ ~ 0 - z rn 9 G) ::r:: a rtT1 5· '-< ~ 0 'Tl N. (iq" (1) ::r:: 0. tT1 N ~ z ,_, CY [/) C ~ >­ (l) g r ;:> C: "'(l) N cf- N &. ~ 0 ::i u en ::,:1 0 I t71 >-+-, z ~ ::,:1 (l) >­ >-< c::: "1J u [/) :0 tT1 0 "cl 0 ~:::, '"'"cf- I I [1 ,I I ll • I I I I 9••• b ~ LITHOLOGY OF THE KALLAVERE FORMATION ON THE NORTH ESTONIAN KLINT (Part I - Paldiski-Kunda area) C ~ (D 0 © (D Samples .0 _Q2 X C Grain size distribution, % P,0 content,% ·m '5 a, -"' Lithology 5 E 0 Thick- No. <f)© .0 E a, D I :::J C <f) ~ 2 ~ ness. m lru ::, 6:, I- 5l -ca~ +2.00 ~ !2-V) 0 .!... __ (/) 0.70 u ~'.~~ 0 c,: 0 w ~ @ a, w~ c,: 9 > ..... .Q ::, :,a l1 12 0 0 0 " 2.35 :e 0)·- C,01 Maardu quarry :, 0 6::J I- -~ 3.45 ~ ~3 u 0.80 0 c,: l;~~ 0 w <( 2 @ w § ~ c,: .Q ..... ::, l1 12 ::e 0 2.20. 0 " :e ~ C,01 Ulgase ::, 6::J I- 5l -°cjl::_ +0.60 ;§ .Qu, 0 ·o, •O <n "§' u "0 1.30 0 c,: ~ 0 w <( 2 § @ w ~ _., H"> c,: .Q ..... :, :,a l1 12 0 3.50 0 "9.: :e 0) 22.Q~ C,01 Jdgala ::, 5l 0::, ] .2~-=o ~ :g,~ 0.80 u <n-O 0 c,: 0 w <( @ 2 a, w § c,: > ..... .Q ::, :,a l1 -g ~ 0 C/ :e o," .. ,., ~,ul Fig. 3. The western sections of Type II. 23 HEUO HETNSALU AND REIN RAUDSEP C al 0 Qj ill Samples '5 .Cl >< C Grain size distribution, % P,O, content, % E Q) -"" Lithology f-Th-ic_k_-~1-N-□-. 1~I Q) ) 0 E Q) u I <n ::, ::;:c :c I </) ~ I- ness, m Valkla ,::, ;:50 0 -w 0 ..!.. __ (./) 0 ""UJ I!! <( Q) ~~~ ~ ~ > UJ ~ Q ::, :,;; I- ~ 11 "" a "'- 1.45 a 0 ::;: .;, :~ """' 3.25 tt.88~ Q) Qi3 2.00 :5°'"' Turjekelder Q ..!.. __ en tv2ll717doVJ21272d ]'.~~ 0.55 0 0 @ ~WWI 0 UJ ::, <( "" g? :,;; Q 11 ~ a c5 2.90 UJ a " ~ ~ ::;: tG I-"" ~e}mfj ,.;. ;,.'.· ,,-./,;•,//,'.·,VZ1>•:",i:""'· ~ 1.60 Muuksi ::, 6:, I- Si l.70 ;:5 ~~ ·5, '.@. "' 0 ::, c5 0 ::, " 0 UJ <( "" "' :s: @ ~ Q) UJ 9 Q ""I- ::, :,;; ~ 11 a " ::;: ~ Fig. 4. The eastern sections of type II. 24 C ID Q) ~ Samples ID ·a3 .0 Q) ~ EX~ C lithology Grain size distribution, % P,O, content,% .0 Q)~ I~g I Thick- INo. ~ a ~ ~ C ~ ness, m N6mmeveski ,::, 80 6~ I- 2.75 ~~ ~c3 O> '.@ (/'J ::, 1.25 al 6" !!! Q) > £ u :!i ::, 0 '2 "' 0 UJ 0 5.00 "" 0 " ~ ::,; ~ UJ ~ B: Vihula u 0"" 0 UJ <{ ?; ::;; 0 Toolse Q u 0 0 !!' UJ"" ~ ~~ 4.30 ~ Q 0 UJ ~ B: ~ ~ "' 0,o.., s 0.50 £,ts Fig. 5. The sections of Type III and of Type III/IV (Toolse section). 25 HELJO HEINSALU AND REIN RAUDSEP guished in the sections of the Maardu Member. Differ­ sections with a higher frequency of argillite interbeds al­ ences between these types are caused by changes in ver­ ways show an increase in the amount of very fine (0.05- tical distribution of the above-mentioned lithological com­ 0.1 mm) quartz grains in sandstone (Fig. 2). ponents and their thicknesses. The thickness of the Maardu Member in Type I sec­ tions ranges from 1.4 to 3.25 m. Suurjogi Member (Oil S) The lower boundary of the Maardu Member is dis­ tinctly marked in Type I sections, but its upper boundary, The member is traditionally known as a "detrital layer" the contact with the Suurjogi Member (O/lS) is gradual. forming the upper part of the Kallavere Formation. In the The thickness of the transitional beds is 0.1-0.35 m. area studied the Suurjogi Member always lies on the The Suurjogi Member is represented by fine- to Maardu Member. Yet, as established by the data on mi­ medium-grained cross-bedded, generally weakly but on crofauna (conodonts), the Suurjogi Member is locally the outcrop surface often very strongly cemented quartz coeval with the Maardu Member (Fig.