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Limestone of St. Jacob

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Hidden : 04/01/2016
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Katedrala sv. Jakova

Jedinstveni spomenik europskog sakralnog graditeljstva

Katedrala Sv. Jakova najznačajnije je graditeljsko ostvarenje 15. i 16. stoljeća na tlu Hrvatske, a po svojoj ljepoti, konstrukcijskim posebnostima i stilskim značajkama nije samo najveći i najvrjedniji objekt graditeljskog naslijeđa grada Šibenika, već ona predstavlja jedinstveni spomenik europskog sakralnog graditeljstva.

Po svojoj umjetničkoj vrijednosti pripada najznačajnijim europskim monumentalnim katedralama, a po nekim svojim osobinama je jedinstvena ne samo među katedralama, već i među kršćanskim crkvama općenito.

Jedina građevina u cijeloj Europi isključivo od kamena

Jedina je katedrala u cijeloj Europi izgrađena isključivo od kamena, bez uporabe vezivne žbuke i drvenih konstruktivnih elemenata.

Također je prva montažna građevina u Europi sagrađena na principu utorenih ploča (ostale na tom principu se počinju graditi tek u 19. stoljeću), kao i jedina građevina čiji volumen izvana u potpunosti odgovara obliku unutrašnjih prostora.

Poznata je po ikonografskim inovacijama, među kojima posebno mjesto zauzimaju friz od 74 skulpture glava (individualni portreti suvremenika Jurja Dalmatinca), koji slovi za najbrojniju i najkvalitetniju galeriju portreta izloženu kao javni spomenik na jednom sakralnom spomeniku u Europi, kao i uvođenje reljefa Boga Oca s golubicom Duha i anđelima na svodu krstionice šibenske katedrale.

Podignuta je na južnoj strani središnjeg starog gradskog trga, na mjestu gdje je nekoć stajala romanička crkva Sv. Jakova. Ideja o gradnji velikog katedralnog hrama datira iz 13. stoljeća kada je Šibenik dobio vlastitu biskupiju i naslov Grada. Gradnja katedrale Sv. Jakova trajala je 105 godina s prekidima, odnosno od 1431. do 1536. godine. Konstrukcija je započeta u venecijanskom gotičkom stilu, a dovršena je u stilu toskanske renesanse.

Majstori: Juraj Dalmatinac i Nikola Firentinac

Prvo desetljeće na njezinu podizanju rade mletački gotički graditelji (Francesco Giacomo, Antonio Busato i Lorenzo Pincino, te šibenski klesarski majstori Andrija Budčić i Grubiša Statčić), a 1441. godine je za glavnog graditelja katedrale postavljen Juraj Matejev Dalmatinac, koji je gradnju katedrale vodio sve do kraja života 1475. godine.

Kao majstor kasne / cvjetne gotike i začetnik prijelaznog gotičko-renesansnog stila u Dalmaciji, svojim je zamislima promijenio prvobitnu koncepciju crkve, dajući joj monumentalni značaj. Nakon Jurjeve smrti, gradnju šibenske katedrale nastavlja Nikola Firentinac, koji gradi u stilu čiste renesanse. Nakon Firentinca, katedrala još nije završena, stoga na njenoj gradnji dalje rade mletački graditelji Bartol i Jakov iz Mestre, te zadarski majstor Mestičević.

Šibenska katedrala je trobrodna bazilika dimenzija 38 x 14 m i s najvišom visinskom točkom na vrhu kupole od 38 m. Posvećena je 1555. godine, a posvetio ju je biskup Ivan Štafilić.

Krstionica kao izvor života

U unutrašnjosti katedrale posebnu pozornost zaslužuje krstionica, koja je u stilskom pogledu originalna i kreativna sinteza dvaju likovnih govora prve polovice 15. stoljeća – kasne gotike i rane renesanse.

Prva je dovršena renesansna arhitektura kao cjelina, a nastala je samo 20 godina nakon pravog početka renesanse u Toscani. Obilje skulptorskog ukrasa najdojmljivija je oznaka krstionice, a u dekorativnim motivima ljudski je lik najzastupljeniji.

Osim četiriju statua proroka (od kojih danas samo dvije sačuvane), čitav je svod ukrašen cjelovitim likovima anđela, glavama kerubina i markantnom glavom Boga Oca. Trio punačkih i u pokretu modeliranih golišavih dječaka majstor je Juraj smjestio uz nosač krsnog zdenca postavljena u sredini prostora.

Njegovo veličanstvo brački kamen (mramor)

Katedrala je izgrađena od bračkog vapnenca iz kamenoloma Veselje, u koji je dolazio i sam Juraj Dalmatinac nadgledajući radove na kamenu koji će se koristiti za izgradnju katedrale.

Taj bijeli brački kamen – mramor (u petrološkom smislu to nije mramor) komercijalno se pojavljuje pod nazivom Veselje Unito i Veselje Fiorito.

U nazivu kamena riječ Veselje se odnosi na istoimenu uvalu iznad koje se nalazi stari kamenolom Veselje, dok su drugi dijelovi naziva Unito odnosno Fiorito obilježja građe kamena. Inačica Unito podrazumijeva da su u građi kamena skeletni ulomci relativno ujednačeni, dok u inačici Fiorito u istoj, manje više bijeloj, osnovi 'plivaju' krupni rudistni ulomci ili cijeli rudisti, koji se ističu smećkastom bojom.



Što je vapnenac?

Vapnenac je sedimentna stijena sastavljena uglavnom od kalcijevog karbonata (CaCO3) u obliku mineralnog kalcita. Vapnenačke forme najbolje su vidljive i prepoznatljive u toplim, plitkim morskim vodama. Vapnenac je obično biološka (organska) sedimentna stijena nastala taloženjem školjaka, koralja, algi i fekalnih ostataka.

Također, može biti i kemijski (anorganski) formirana sedimentna stijena nastala taloženjem kalcijevog karbonata iz jezera, mora ili oceana.

Nastajanje vapnenca - marinski

Većina vapnenaca nastaje u plitkim, mirnim i toplim morskim vodama. U morskom okruženju lako dolazi do izvlačenja kalcijevog karbonata iz školjaka i kostura potrebnih za formiranje vapnenca. Nakon što morski organizmi izumru njihove oklopne i skeletne krhotine talože se kao sediment koji se pretvara u vapnenac. Njihovi otpadni proizvodi (kakica) također mogu doprinijeti taloženju. Vapnenci nastali na ovakav način nazivaju se biološkim sedimentnim stijenama. Njihovo biološko podrijetlo otkrivamo prisutnošću fosila u stijeni.

Neki vapnenci mogu nastati izravnim taloženjem kalcijeva karbonata iz morske ili slatke vode. Vapnence nastale na ovaj način nazivamo kemijskim sedimentnim stijenama. Po svojoj strukturi manje su obilni od biološkim vapnenaca.

Danas je na Zemlji puno vapnenačko oblikovanih okruženja. Većina ih se nalazi u pličinama između 30 stupnjeva sjeverne geografske širine i 30 stupnjeva južne geografske širine.

Nastajanje vapnenca - isparavanjem

Vapnenac može nastati i isparavanjem. Stalaktiti, stalagmiti i ostali spiljski oblici takvi su primjeri vapnenca. U pećini, kapljice vode cure odozgo kroz pukotine ili pore i dolaze do spiljskih stropova. Prije pada na pod spilje može doći do isparavanja. Kako voda isparava tako se kalcijev karbonat taloži na stropu spilje. Tijekom vremena proces isparavanja može rezultirati nastankom vrhova kalcijeva karbonata na stropu spilje. Takve naslage počinju tvoriti stalaktite. Moguć je i obrnuti proces kada se isparavanje događa na tlu spilje što omogućava nastanak stalagmita.

Vapnenac koji tako tvori spiljske oblike poznat je i kao „sedra“ te pripada kemijskim sedimentnim stijenama. Stijena poznata kao „tuf“ vapnenac je nastao isparavanjem vrućih izvora, obala jezera ili sličnih područja.

Sastav vapnenca

Vapnenac je po definiciji kamen koji sadrži najmanje 50% kalcijevog karbonata u obliku kalcitne mase. Svi vapnenci sadržavaju barem nekoliko postotaka drugih materijala. To mogu biti maleni udjeli kvarca, feldspata, gline, pirita, siderita i ostalih materijala. Također mogu sadržavati veće komade rožnjaka, pirita ili siderita.

Prisustvo kalcijevog karbonata u vapnencu daje mogućnost lake identifikacije stijene, koja se izložena hladnoj otopini 5%-tne solne kiseline – zapjeni.

Fosili

Na svim spomenutim lokacijama, pronaći ćete ne samo lijep primjer sedimentne stijene vapnenca, već i veliki broj fosila. Što su uopće fosili? Oni su sve ono što dokazuje život u prošlim vremenima. Taj se dokaz prošlog života javlja u dva oblika. On može biti izravan ili neizravan.

Izravan dokaz života su fosili koje čine čvrsti dijelovi organizama. U slučaju životinja, to mogu biti fosilizirane kosti ili školjke. Ili, kada su u pitanju biljke, to može biti fosilizirano drvo ili lišće. U nekim slučajevima, fosiliziran može biti i cijeli organizam, i njegovi meki i njegovi čvrsti dijelovi. Primjeri takvih fosila su insekti zarobljeni u jantaru ili mamuti smrznuti u ledu.

Neizravan dokaz života su fosilni tragovi. To su različiti otisci stopala, repova, tragova, koje su organizmi ostavljali, a zatim su fosilizirani. Koproliti (fosilizirana kakica) su također jedan primjer fosilnih tragova.

Klasifikacija

Dva su velika klasifikacijska sustava kojima se služimo prilikom identifikacije i klasifikacije vapnenačkih i karbonatnih stijena: Folkov i Dunhamov.

Folkova klasifikacija

Robert L. Folk razvio je klasifikacijski sustav koji u prvi plan stavlja detaljnu strukturu zrna i naglašava primarnu detaljnost sastava zrna i ostalih materijala u karbonatnim stijenama. Razlikuje tri vrste sastojaka: alokeme (zrna), matriks (uglavnom mikrit) i cement (sparit). Folkov sustav koristi dvodijelne nazive: prvi dio se odnosi na dominantnost zrna, a drugi na prevladavajuće vezivo (mikrit ili sparit). Prilikom korištenja Folkovog sustava preporuča se koristiti petrografov mikroskop jer je lakše odrediti prisutne komponente u svakom uzorku.


Dunhamova klasifikacija

Dunhamova klasifikacija temelji se na strukturnim značajkama. Svako ime temelji se na teksturi zrna koje čini vapnenac. Dunham je 1962. godine objavio svoj sustav klasifikacije koji dijeli stijene u četiri glavne skupine temeljem relativnih proporcija grubljih klastičnih čestica. Dunhanovi nazivi osnova su za određivanje stijena.

Bavio se pitanjem jesu li ili nisu izvorna zrna u međusobnom kontaktu, podržavaju li se međusobno ili su karakteristična vidljiva razgraničenja. Za razliku od Folka, Dunham se bavio poroznošću stijena. Dunhamova klasifikacija je korisnija i kvalitetnija jer se temelji na teksturi, a ne na ispitivanju zrna u uzorku.



Da biste prijavili pronalazak potrebno je odgovoriti na sljedeća pitanja:

1. Prošećite oko Katedrale i opišite teksturu i boju vapnenca na vanjskim zidovima!

2. Jesu li ovi vapnenci biološki ili kemijski vapnenci? Objasnite?

3. Pretražite lokaciju i pronađite barem jedan fosil. Je li taj fosil direktan ili indirektan dokaz o prošlom životu? (objasnite)

4. Kolika je visina i širina ulaznih vrata u Katedralu?

5. Zašto je Dunhamova metoda klasifikacije bolja od Folkove?

6. Priložite sliku s GPS-om (nije obvezno)

Pošaljite odgovore e-poštom (putem GC profila). Slobodno upišite pronalazak, a ako nešto nije u redu, obavijestit ću vas!




The Cathedral of St. Jacob - The UNESCO monument



The unique monument of European sacral architecture

The cathedral of St. Jacob is the most valuable architectural monument built during the 15th and the 16th century in Croatia, and according to its beauty, construction techniques and style characteristics it is not only the biggest and the most valuable object of the architectural heritage of the Town of Šibenik, but it represents also a unique monument of the European sacral architecture.

According to its artistic value, it belongs to the most valuable European monumental cathedrals, and thanks to some of its features it is unique not only among the cathedrals, but among the Christian churches in general.

The only construction built entirely of stone in the whole of Europe

It is the only cathedral in the whole of Europe constructed entirely of stone. No wooden architectural elements were used for its building.

It is also the first construction in the whole of Europe, the assemblage of which was based on a unique system of intergrooved stone plates (other constructions based on this system originate from the 19th century), as well as the only construction whose outside volume completely corresponds to the shape of the interior.

The cathedral of St. Jacob is well known for the iconographic innovations, among which the frieze of 74 head sculptures (individual portraits of the contemporaries of Juraj Dalmatinac) takes special place. It is considered to be the most numerous portrait gallery of the highest quality exhibited as the public monument on a sacral object in Europe. Also, introduced was the relief representing Father God with the dove of the Holy Spirit and angels on the vault of the baptistery of the Cathedral.

The Cathedral was constructed on the south side of the central square of the oldest town core, on the site of the former Romanesque church of St. Jacob. The idea of the construction of a big Cathedral temple derives from the 13th century, when Šibenik was given the status of a town and its own diocese. The construction lasted for 105 years with interruptions, from 1431 until 1536. It began in the Venetian Gothic style, and was finished in the Tuscan Renaissance style.

Masters: Juraj Dalmatinac and Nikola Firentinac

During the first decade of the 15th c., the construction of the Cathedral was led by the Venetian architects Francesco Giacomo, Antonio Busato and Lorenzo Pincino, as well as Šibenik’s stonemasons Andrija Budčić and Grubiša Statčić, but in 1441 Juraj Dalmatinac was appointed protomaster and worked on the construction until his death in 1475.

As the master of the late / flower Gothic style and initiator of the Gothic-Renaissance style in Dalmatia, Juraj Dalmatinac changed the initial plan of the church, giving it monumental importance. After his death, the construction of the Cathedral was continued by Nikola Firentinac in the pure Renaissance style. Since the Cathedral hadn’t been finished, after Firentinac the construction was taken over by Venetian architects Bartol and Jakov from Mestre, and Zadar’s master Mestičević. The Šibenik Cathedral is a three-naved basilica 38 meters long and 14 meters wide, and its highest point is on the top of the cupola (38 meters). It was consecrated in 1555 by Bishop Ivan Štafilić.

Baptistery as well of life

In the Cathedral’s interior the baptistery draws particular attention because of its original and creative synthesis of two different art styles of the first half of the 15th century – late Gothic and early Renaissance.

The Cathedral represents the first finished architecture in Renaissance style constructed only 20 years after the real beginning of the Renaissance in Tuscany. The most impressive feature of the baptistery is the abundance of sculptural decoration among which the human figure is the most represented one.

Besides the sculptures of the four prophets (of which only two are preserved until today), the whole vault is decorated with reliefs of angels, cherubs’ heads and impressive head of Father God. The baptismal font is located in the centre of the baptistery, carried by three plump naked boys in movement made by Juraj Dalmatinac.

His Majesty Brač stone (marble)

The cathedral was built from Brač limestone from the quarry Veselje. The builder of the cathedral Juraj Dalmatinac came to the quarry and oversaw the stonework on the stone used to build the Cathedral.

The white Brač stone - marble (in the petrological sense, it is not marble) commercially became known as the Veselje Unito and Veselje Fiorito.

The name of the stone “Veselje” refers to the cove located beneath the old quarry Veselje, while other parts called Unito and Fiorito features material stone.

Form Unito implies that the structures of stone skeletal fragments are relatively uniform, while the version Fiorito in the same, more or less white, base 'swim' big rudist fragments or whole rudists, which stand out with brownish color.




What is Limestone?

Limestone is a sedimentary rock composed primarily of calcium carbonate (CaCO3) in the form of the mineral calcite. It most commonly forms in clear, warm, shallow marine waters. It is usually an organic sedimentary rock that forms from the accumulation of shell, coral, algal and fecal debris. It can also be a chemical sedimentary rock formed by the precipitation of calcium carbonate from lake or ocean water.

Limestone-Forming Environment - Marine

Most limestones form in shallow, calm, warm marine waters. That type of environment is where organisms capable of forming calcium carbonate shells and skeletons can easily extract the needed ingredients from ocean water. When these animals die their shell and skeletal debris accumulate as sediment that might be lithified into limestone. Their waste products can also contribute to the sediment mass. Limestones formed from this type of sediment are biological sedimentary rocks. Their biological origin is often revealed in the rock by the presence of fossils.

Some limestones can form by direct precipitation of calcium carbonate from marine or fresh water. Limestones formed this way are chemical sedimentary rocks. They are thought to be less abundant than biological limestones.

Today Earth has many limestone-forming environments. Most of them are found in shallow water areas between 30 degrees north latitude and 30 degrees south latitude.

Limestone-Forming Environment - Evaporative

Limestone can also form through evaporation. Stalactites, stalagmites and other cave formations (often called "speleothems") are examples of limestone that formed through evaporation. In a cave, droplets of water seeping down from above enter the cave through fractures or other pore spaces in the cave ceiling. There they might evaporate before falling to the cave floor. When the water evaporates, any calcium carbonate that was dissolved in the water will be deposited on the cave ceiling. Over time this evaporative process can result in an accumulation of icicle-shaped calcium carbonate on the cave ceiling. These deposits are known as stalactites. If the droplet falls to the floor and evaporates there a stalagmite could grow upwards from the cave floor.

The limestone that makes up these cave formations is known as "travertine" and is a chemical sedimentary rock. A rock known as "tufa" is a limestone formed by evaporation at a hot spring, lake shore, or other area.

Composition of Limestone

Limestone is by definition a rock that contains at least 50% calcium carbonate in the form of calcite by weight. All limestones contain at least a few percent other materials. These can be small particles of quartz, feldspar, clay minerals, pyrite, siderite and other minerals. It can also contain large nodules of chert, pyrite or siderite.

The calcium carbonate content of limestone gives it a property that is often used in rock identification - it effervesces in contact with a cold solution of 5% hydrochloric acid.

On EarthCache location, you can find not only nice example of sedimentary rock limestone, but also nice examples of fossils. What are fossils, anyway? Well, they are anything that provides evidence of life in past ages. That evidence of life in past ages can come in two types. It can be either direct evidence or indirect evidence of past life.

Direct evidence of life are fossils of hard body parts of organisms. They can be fossilized bones or shells in case of animals. Or it can be fossilized wood or leaves in case of plants. In some cases, the entire organism can be fossilized, together with both soft and hard parts. Example of such fossils are insects trapped in amber or mammoths frozen in ice.

Indirect evidence of life are trace fossils. They are various footprints, trails, marks that were left by organisms and then fossilized. Coprolites (fossilized poo) is also one example of trace fossils.

Classification

Two major classification schemes, the Folk and the Dunham, are used for identifying limestone and carbonate rocks.

Folk classification

Robert L. Folk developed a classification system that places primary emphasis on the detailed composition of grains and interstitial material in carbonate rocks. Based on composition, there are three main components: allochems (grains), matrix (mostly micrite), and cement (sparite). The Folk system uses two-part names; the first refers to the grains and the second is the root. It is helpful to have a petrographic microscope when using the Folk scheme, because it is easier to determine the components present in each sample.

Dunham classification

The Dunham scheme focuses on depositional textures. Each name is based upon the texture of the grains that make up the limestone. Robert J. Dunham published his system for limestone in 1962; it focuses on the depositional fabric of carbonate rocks. Dunham divides the rocks into four main groups based on relative proportions of coarser clastic particles. Dunham names are essentially for rock families. His efforts deal with the question of whether or not the grains were originally in mutual contact, and therefore self-supporting, or whether the rock is characterized by the presence of frame builders and algal mats. Unlike the Folk scheme, Dunham deals with the original porosity of the rock. The Dunham scheme is more useful for hand samples because it is based on texture, not the grains in the sample.



To get the log permission, please answer the following questions:

1. Walk around Cathedral and try to describe the texture AND color of the limestone at walls?

2. Is this limestone biological or chemical limestone? Why?

3. Search the EC location and find at least one fossil. Is this fossil direct evidence or indirect evidence of past life? (explain)

4. What is the high and width of Cathedral's entrance?

5. Why Dunham’s classification is better than Folk’s classification?

6. Take a photo with GPS (optional)


Please email me your answers in english (via GC-Profile). You don't have to wait for a permission to log. If your answers are incorrect, I will inform you



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