Zakuv lom - Zak's quary EarthCache

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Zakuv lom

Keska Vas zavede do opusteneho Zakova lomu na kraji Velke Chuchle. Muzete si zde vsimnout deskovitych vapencovych vrstev svrchni casti pridolskeho souvrstvi (svrchni silur) s typickym stridanim cernosedych pevnych jemnozrnych vapencu s vlozkami tmavych vapnitych bridlic (stejne jako v pripade Barrandovy skaly). Vrstvy pevnejsiho vapence jsou az nekolik desitek cm silne.
Krome vapence zde muzete casto narazit na kalcitove krystaly a misty i na pyrit, ktery (stejne jako pritomnost uhliku v organickych slouceninach) svedci o sedimentaci pri nedostatku kysliku.

Vrasa v lomu

Historie

V Zakove lomu se drive lamal vapenec na vyrobu cerne mozaikove dlazby v Praze. Nyni se z nej bohuzel stava smetiste. Nicmene alespon horni cast lomu zustava cista.

Paleontologie

Lom je vyznamnou paleontologickou lokalitou s hojnym vyskytem nautiloidnich hlavonozcu radu Orthocerida (vyznacnym je napriklad Orthocycloceras fluminese). Dale zde muzete narazit na zastupce radu Eurypterida, napr. jedince druhu Acutiramus bohemicus, kteri dosahovali delky az 2 m (ale nikdy nebyl nalezen kompletni exemplar). Mimochodem, kvuli vyskytu techto velkych clenovcu muzete mezi paleontology narazit i na nazev Eurypteridovy lom.

 



Hlavonozci rodu Orthoceras

Muzete tu take narazit i na segmenty velkych fylokaridnich korysu Ceratiocaris (Bohemicaris) bohemica a C. (B.) grata - jde zejmena o ostny z konce trupu a masivni kusadla.
Bezny je take vyskyt mlzu (rody Dualina, Cardiolinka, Praecardium, Snoopya, Actinopteria aj.), plzu (typicky je Orthonychia elegans) a drobnych ostrakodu a ostnokozcu rodu Scyphocrinites (zname spis pod nazvem "lilijice").
Dalsimi typickymi zkamenelymi zivocichy, na ktere muzete narazit, jsou graptoliti (vypadaji trochu jako zkrouceny list lupenkove pilky), zde zejmena Monograptus lochkovensis, M. bouceki, M. perneri a M. transgrediens.

 

Graptoliti

Co zde naopak nenajdete - lokalni podminky nebyly prilis priznive pro rozvoj nekterych skupin bentoznich (dno obyvajicich) zivocichu - napr. ramenonozci (Brachiopoda) jsou zde velice vzacni a trilobiti zde nebyli vubec nalezeni.

Eurypterida

Hledani zkamenelin

Pokud si chcete zahledat, vyhlidnete si nejakou hromadu suti a smele se na ni vrhnete. Lokalita je pomerne bohata, takze si nebudete muset hrat na krtky dlouho a urcite neco objevite. Rozhodne se ale nevrtejte v lomove stene! Je to nebezpecnejsi, mene efektivni a navic zakazane.

Podminky logovani

Za co dostanete bodik:

1. najdete v suti nejakou zkamenelinu, pokuste se ji zaradit (aspon na uroven radu) a vyfotte ji - fotku se zarazenim prilozte k logu; pokud bude sut v lomu moc prebrana, muzete zkusit stesti i jinde, napr. u cyklostezky pod Barrandovou skalou je sutovisek az az - jen pozor na padajici kameni!
2. k logu prilozte fotku Vas nebo Vasi GPS s vrasou v lomove stene v pozadi

Co se tu da najit - zleva: koruna morske lilijice Scyphocrinites elegans, schranka silurskeho mlze r. Cardiola a schranka hlavonozce s castecne obnazenym prurezem (plynove komurky)

Zdroje

1. Ivo Chlupac: Vychazky za geologickou minulosti Prahy a okoli
2. cedule naucne stezky (podle obsahu maji bohuzel jediny zdroj a to je vyse uvedena publikace )
3. obrazky z wikipedie, od uzivatelu seznam.cz, obecne nalezeno pomoci google.com

Zak's quarry

This cache will lead you to the abandoned quarry next to village Velka Chuchle. You can see there tabular limestone layers of upper part of Pridol formation (upper silur) with typicaly changing dark gray solid limestones and shims of dark calcareous slates (similar to the Barrande's rock). The layers of limestones are more than 10 cm thick.
You can also find calcite crystals very often there and sometimes pyrite - that's prove of sedimentation without oxygen.

Fold in the quarry

History

The limestone from Zak's quarry was used to build pavements in Prague (dark cubes in mozaic). Nowadays it's unfortunately used as a junkyard (lower part, upper is still clean and I hope it will stay clean).

Paleontology

The quarry is notable paleontologic locality. You can find there lot of cephalopods of order Orthocerida (significant is for example Orthocycloceras fluminese). You can also see there representatives of order Eurypterida, f.e. specie Acutiramus bohemicus, which were almost 2 m long (but nobody ever found complete body). By the way, these big arthropodes gave another name to this quarry - Eurypteride quarry - known especialy among paleontologists.

 



Order Orthoceras

You can also find segments of huge crustaceans Ceratiocaris (Bohemicaris) bohemica and C. (B.) grata - usually spines from "tail" or massive mandibles.
Very ordinary fossils are also clams (genies Dualina, Cardiolinka, Praecardium, Snoopya, Actinopteria, ...), snails (typical is Orthonychia elegans) and small ostracodes and echinoderms of genus Scyphocrinites (known as "sea lilly" or "crinoid").
Another typical fossil animals you can find there, are graptolites, especially Monograptus lochkovensis, M. bouceki, M. perneri a M. transgrediens.

 

Graptolites

On the other hand you can find there only very few Brachiopoda and no trilobites.

Eurypterida

Fossils searching

If you want to find some fossils, you should search some heap of broken stones Never dig to the quarry wall! It's dangerous, less effective and forbidden. Location is quite rich in fossils so you have big chance to find something.

Logs

To get the point you have to:

1. find any fossil, try to classify it (at least the order), take a picture of it and add the photo with classification to your log
2. add a picture of you or your GPS and the fold on background (see 1st image) to your log

What you can find - from the left: sea lilly Scyphocrinites elegans, clam g. Cardiola and cephalopod o. Orthoceras

Source

1. Ivo Chlupac: Vychazky za geologickou minulosti Prahy a okoli
2. information tables
3. pictures from wikipedia, users of seznam.cz, found by google.com