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Středomoří: Geologie Malty

19.07.2008
Geologie
Středomoří: Geologie Malty

The geology of the Maltese Islands is relatively young when considered within a geological time frame

 

 

 

   

 

   

The geology of the Maltese Islands is relatively young when considered within a geological time frame, with the oldest rock dating back only to the Tertiary period. The Islands are for the most part composed of marine sedimentary rocks. Although the sedimentary platform on which the Maltese Islands are situated was formed during the Triassic, there are no surface outcrops of this age. All exposed rocks were deposited during the Oligocene and Miocene periods of geological time dating back to some 30 to 35 million years ago. The most recent deposits are the quaternary deposits which are found in minor quantities and are of terrestrial origin. The resultant rock formations are relatively simple consisting of five basic layers laid on top of the other in a layer-cake sequence:

Podrobná mapa je na adrese:http://www.emwis-mt.org/documentation/geological map.jpg  

 

 Lower Coralline Limestone is the oldest exposed rock in the Maltese Islands, outcropping to a height of 140m in the vertical cliffs near Xlendi, Gozo. It is mainly composed of the tests of coralline algae indicating deposition in a shallow gulf environment.  Younger beds show evidence of deposition in more open marine conditions.
 

 

 

 

 

 

Globigerina Limestone is the second oldest rock and outcrops over approximately 70% of the area of the islands, eroding to give a broad, gently rolling landscape.  Variations in the thickness of this formation are considerable, ranging from 23m near Fort Chambray, Gozo to 207m around Marsaxlokk, Malta.   This rock consists of yellow to pale-grey limestones comprising tests of planktonic globigerinid foraminifera.  The formation is divided into Lower, Middle and Upper Globigerina Limestone by two beds of phosphorite pebbles.

Blue Clay overlies the Globigerina Limestone formation.  It erodes easily when wet and forms taluses which flow out over the underlying rock. Variations in thickness are considerable ranging from 75m at Xaghra, Gozo to nil in eastern Malta, where Upper Coralline Limestone rests directly on Globigerina Limestone.  Deposition of the Blue Clay may have occurred in an open muddy water environment with water depths up to 150m for the lower part of the formation.

The above plate shows the 4 top rock layers of the geological sequence of the Maltese Islands. The top most reddish layer is the UCL. Beneath the Blue Clay forms  rolling hill. The platform is composed of eth Lower Globigerina Limestone. the boulders found lying on this platform have fallen from the UCL plateau above.

 

Lower Coralline Limestone at Wied Babu, Zurrieq, S. Coast of Malta

 

ZDROJ: www.emwis-mt.org

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