Heviews— Geology of Prussian- Silesia. 



325 



limited in the east by the Jurassic ridge of hills, which extends from Krakau north- 

 wards, and to the south and west by the above-mentioned Muschelkalk. 



7. Lettenkohle, grey and red clay and shales, with brown Dolomite and green 

 sandstone, with few organic remains (page 153). It rests conformably on the Upper 

 Muschelkalk, and is again conformably overlain by 



8. The Middle Keuper, which consists of reddish brown clay, with embedded white 

 limestone, which contains hornstone. A conglomerate, with fishes and remains of 

 saurians. A greyish-green sandstone with thin beds of coal. Total thickness, 200 

 to 300 feet. Very poor in fossils (page 162). 



9. Upper Keuper, or RhcBtic Group. 



a. Wilmsdorfer Beds, consisting of reddish and greyish-green clay and marl, with 

 argillaceous Sphaeroslderite, which contains land-plants (page 178). 60 to 

 80 feet in thickness. 

 I. Estheria Beds of Hellewald, resting conformably on the former and consisting 

 of thinly-stratified white sandstone, with mica and shales, sphserosiderite. 

 Estheria minuta numerous. Thickness about 60 to 80 feet. 

 Both the geological structure, as well as most of the species, resemble the typical 

 Keuper of Middle Germany, although not in lithological character, as the marls of 

 Germany are mostly represented in Silesia by limestones. 



B. Jurassic Formation. — This forms a long ridge of hills between Krakau and 

 Czenstochau ; with a few interruptions it extends to Wielun in a north-westerly 

 direction. Beyond this place Jurassic rocks are found isolated in the surrounding 

 Diluvium, as for instance near Kalisch, and even so far north-west as Thorn. Also 

 in the East, on the banks of the Pilica, in Poland, we find a low ridge of hills, which 

 extends South-west, between Kielce and Korytnica. In all, the Jurassic formation 

 covers an area of about 6600 square miles, although it is at some places concealed by 

 Drift. 



The strata are very rarely highly elevated, in most cases they slope gently towards 

 the east and north-east. The Jura rest unconformably on Keuper. The average 

 thickness is about 500 feet. 



Eoemer distinguishes two great groups in the Jura of Silesia : a Lower group, con- 

 sisting of dark-coloured sandy and argillaceous beds, forming a flat country, or only 

 low hills; and an Upper group of white Limestones and Dolomites, forming moun- 

 tainous and rugged country. The Lower group represents the brown Jura of Swabia 

 (Dogger), whilst the Upper group resembles Quenstedt's White Jura (Malm). The 

 Lias formation is nowhere developed in Silesia, which is in accordance with all the 

 Jurassic deposits in Eastern Europe. 





The subjoinec 



Table gives the sub-divisions of the Jurassic series :— 



P4 

 p 



§ 



STRATUM. 



BEDS. 



GENERAL CHARACTER, STRUCTURE. 



EaUIVALENTS. 





9. Stratum of 

 Exogyra virgula. 





On the banks of the Pilica, 

 etc., etc. Compact limestone, 

 like the lithographic stone of 

 Solenhofen. E. virgula in 

 great numbers. 



Kimmeridge 

 beds. 



< 

 Pi 

 P 

 1-5 



m 



Eh 



3 



8. Nerinea 



limestone of 



Inwald. 





Inwald and Roczyny, Ga- 

 licia. Compact white lime- 

 stone. Brachiopoda, Lamelli- 

 branchiata and Gasteropoda 

 (Nerinsea). Cephalopoda dis- 

 appear nearly. 



Limestone of 



Plassen, near 



Hallstadt ? 



H 

 P 



cs 



p 



7. Bed of 



Bhynchonella 



Astieriana, 





Forms the North-eastern 

 extremity of the Jurassic hills, 

 between Pilica and Mstow. 

 White compact limestones 

 with hornstone. Great num- 

 ber of well preserved fossils. 



WhiteJura,E. 

 of Quenstedt. 



Zone of the 



Cidaris flori- 



qemma,0\)]}G\, 



Upper Oxford. 



