Index Geophysics

eng INFLUENCE OF SEDIMENTARY ENVIRONMENT ON THE TECHNICAL PROPERTIES OF THE LOWER CRETACEOUS LIMESTONES FROM THE LAKOVIĆI QUARRY IN ISTRIA (CROATIA)

hrv UTJECAJ SEDIMENTNOG OKRUŽJA NA TEHNIČKA SVOJSTVA DONJOKREDNIH VAPNENACA KAMENOLOMA LAKOVIĆI U ISTRI (HRVATSKA)

eng The Lower Cretaceous limestones from the Lakovići quarry belong to the basal part of the Aptian limestones. These limestones are the beginning of the second transgressive-regrcssive megasequence in Istria which followed a general Upper Aptian emersion event. Within the approximately 50 m thick limestone sequence that is quarried, four facies units were defined according to their petrographic and sedimen-tological features. The following facies units were devided: A- Micritic limestones, which were deposited as shallowing-upward cycles and which begin with breccias containing clay matrix or terminate with dark-gray clays sporadically accompanied by deposition and redeposi-lion of black terrestrial and swamp clays, as well as sediments from bogs and pools that were developed in isolated bays and/or laggons; B -Grain supported limestone deposited as fine-grained to coarse-grained carbonate sands in a predominantly high-energy shallows, bars and sandy beaches; C - Micritic limestones deposited in restricted low-energy shallow subtidal environments; D - Drain supported limestones deposited as fine grained carbonate sands in high-energy shallows and bars. The results of petrological, sedimentological and technological investigations show that the limestones from each individual facies unit have different technical properties, notably porosity, bulk density and water absorption, i.e. the wide range of technical quality of the limestones quarried is a direct consequence of their facies characteristics. The outlined facies units enable separation of rock mass in the quarry not only by their petrological characteristics but also according to the technical quality of the rock.

hrv Donjokredni vapnenci kamenoloma Lakovići pripadaju bazalnom dijelu aplskih vapnenaca kojima, nakon opće gornjoaptske emerzije, počinje druga transgresivno-regresivna megasekvencija u Istri. Unutar 50-ak metara debljine vapnenaca koji se eksploatiraju u kamenolomu Lakovići izdvojene su na osnovu petrografsko-sedimentoloških karakteristika četiri facijesne jedinice. To su: A- Mikritom bogati vapnenci taloženi kao ciklusi oplićavanja naviše koji počinju brečama s glinovitim matriksom ili završavaju tamnosivim glinama; B - Zrnasti vapnenci taloženi kao sitnozrnati do krupnozrnati vapnenački pijesci u plićacima s pretežito visokom energijom vode i na pješčanim plažama; C -Mikritom bogati vapnenci taloženi u zaštićenim potplimnim plićacima s niskom energijom vode i D-Zrnasti vapnenci taloženi kao sitnozrnati vapnenački pijesci u plićacima i plažama s pretežito visokom energijom vode. Rezultati petroloških, sedimentoloških i tehničko-tehnoloških istraživanja pokazuju da vapnenci svake pojedine facijesne jedinice imaju različita tehnička svojstva, posebice ona vezana uz poniznost, prostornu masu i upijanje vode, tj. da je velika varijabilnost tehničke kvalitete kamena u kamenolomu izravna posljedica njihovih facijesnih karakteristika. Izdvojenim facijesnim jedinicama određena je i selektivnost stijenske mase u kamenolomu u odnosu na, kako petrološka svojstva, tako i tehničko-tehnološku kvalitetu kamena.

Tišljar, Josip

Đokić, Zlatko

Ženko, Tomislav

eng carbonate facies;peritidal limestones;shallowing-upward cycles;tidal-bar environment;Lower Cretaceous;limestone aggregates;technical properties of limestones

hrv karbonatni facijesi;periplimni vapnenci;ciklusi oplićavanja naviše;okoliši plimnih prudova;Donja kreda;vapnenački agregati;tehnička svojstva vapnenaca

Faculty of Mining, Geology and Petroleum Engineering University of Zagreb

1997

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Rudarsko-geološko-naftni zbornik

ISSN 1849-0409 (Online)

Volume 9

Issue 1

eng

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