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103-568: It is not known when the first giren were constructed in Malta. Their typology bears some similarities with the Megalithic Temples of Malta , although there is no conclusive proof that the building traditions are directly linked, and it has been suggested that the resemblance is superficial. The huts also share characteristics with other vernacular constructions in the Mediterranean region, such as

206-455: A Mohs hardness of 2 to 4, dense limestone can have a crushing strength of up to 180 MPa . For comparison, concrete typically has a crushing strength of about 40 MPa. Although limestones show little variability in mineral composition, they show great diversity in texture. However, most limestone consists of sand-sized grains in a carbonate mud matrix. Because limestones are often of biological origin and are usually composed of sediment that

309-457: A bloom of cyanobacteria or microalgae . However, stable isotope ratios in modern carbonate mud appear to be inconsistent with either of these mechanisms, and abrasion of carbonate grains in high-energy environments has been put forward as a third possibility. Formation of limestone has likely been dominated by biological processes throughout the Phanerozoic , the last 540 million years of

412-594: A book in Maltese by historian Mikiel Fsadni in 1990 which was also translated to English in 1992. Many giren have been lost through neglect, but many others still exist and some remain in use, mainly for storage. A few giren are still being built as of the early 21st century; for example, one was constructed at the Ta' Blankas olive grove in Xewkija in 2014 as part of a refurbishment project. Most giren are found in rural areas in

515-434: A carbonate rock outcrop can be estimated in the field by etching the surface with dilute hydrochloric acid. This etches away the calcite and aragonite, leaving behind any silica or dolomite grains. The latter can be identified by their rhombohedral shape. Crystals of calcite, quartz , dolomite or barite may line small cavities ( vugs ) in the rock. Vugs are a form of secondary porosity, formed in existing limestone by

618-612: A central quartz grain or carbonate mineral fragment. These likely form by direct precipitation of calcium carbonate onto the ooid. Pisoliths are similar to ooids, but they are larger than 2 mm in diameter and tend to be more irregular in shape. Limestone composed mostly of ooids is called an oolite or sometimes an oolitic limestone . Ooids form in high-energy environments, such as the Bahama platform, and oolites typically show crossbedding and other features associated with deposition in strong currents. Oncoliths resemble ooids but show

721-449: A change in environment that increases the solubility of calcite. Dense, massive limestone is sometimes described as "marble". For example, the famous Portoro "marble" of Italy is actually a dense black limestone. True marble is produced by recrystallization of limestone during regional metamorphism that accompanies the mountain building process ( orogeny ). It is distinguished from dense limestone by its coarse crystalline texture and

824-949: A composition reflecting the organisms that produced them and the environment in which they were produced. Low-magnesium calcite skeletal grains are typical of articulate brachiopods , planktonic (free-floating) foraminifera, and coccoliths . High-magnesium calcite skeletal grains are typical of benthic (bottom-dwelling) foraminifera, echinoderms , and coralline algae . Aragonite skeletal grains are typical of molluscs , calcareous green algae , stromatoporoids , corals , and tube worms . The skeletal grains also reflect specific geological periods and environments. For example, coral grains are more common in high-energy environments (characterized by strong currents and turbulence) while bryozoan grains are more common in low-energy environments (characterized by quiet water). Ooids (sometimes called ooliths) are sand-sized grains (less than 2mm in diameter) consisting of one or more layers of calcite or aragonite around

927-412: A considerable fraction of the limestone bed. At depths greater than 1 km (0.62 miles), burial cementation completes the lithification process. Burial cementation does not produce stylolites. When overlying beds are eroded, bringing limestone closer to the surface, the final stage of diagenesis takes place. This produces secondary porosity as some of the cement is dissolved by rainwater infiltrating

1030-483: A drop of dilute hydrochloric acid is dropped on it. Dolomite is also soft but reacts only feebly with dilute hydrochloric acid, and it usually weathers to a characteristic dull yellow-brown color due to the presence of ferrous iron. This is released and oxidized as the dolomite weathers. Impurities (such as clay , sand, organic remains, iron oxide , and other materials) will cause limestones to exhibit different colors, especially with weathered surfaces. The makeup of

1133-621: A few million years, as this is the most stable form of calcium carbonate. Ancient carbonate formations of the Precambrian and Paleozoic contain abundant dolomite, but limestone dominates the carbonate beds of the Mesozoic and Cenozoic . Modern dolomite is quite rare. There is evidence that, while the modern ocean favors precipitation of aragonite, the oceans of the Paleozoic and middle to late Cenozoic favored precipitation of calcite. This may indicate

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1236-455: A few thousand years. As rainwater mixes with groundwater, aragonite and high-magnesium calcite are converted to low-calcium calcite. Cementing of thick carbonate deposits by rainwater may commence even before the retreat of the sea, as rainwater can infiltrate over 100 km (60 miles) into sediments beneath the continental shelf. As carbonate sediments are increasingly deeply buried under younger sediments, chemical and mechanical compaction of

1339-490: A high percentage of the mineral dolomite , CaMg(CO 3 ) 2 . Magnesian limestone is an obsolete and poorly-defined term used variously for dolomite, for limestone containing significant dolomite ( dolomitic limestone ), or for any other limestone containing a significant percentage of magnesium . Most limestone was formed in shallow marine environments, such as continental shelves or platforms , though smaller amounts were formed in many other environments. Much dolomite

1442-405: A large passage; the third one has two parallel sets of apses with a passage in a direction parallel to that of the first temple. The first temple is solidly built with large stones, of which some are roughly dressed. The walls are laid with great accuracy, and are very imposing in their simplicity. The second temple is more elaborately constructed, the walls being finished with greater care, some of

1545-435: A limestone sample except in thin section and are less common in ancient limestones, possibly because compaction of carbonate sediments disrupts them. Limeclasts are fragments of existing limestone or partially lithified carbonate sediments. Intraclasts are limeclasts that originate close to where they are deposited in limestone, while extraclasts come from outside the depositional area. Intraclasts include grapestone , which

1648-466: A lower Mg/Ca ratio in the ocean water of those times. This magnesium depletion may be a consequence of more rapid sea floor spreading , which removes magnesium from ocean water. The modern ocean and the ocean of the Mesozoic have been described as "aragonite seas". Most limestone was formed in shallow marine environments, such as continental shelves or platforms . Such environments form only about 5% of

1751-525: A lower diversity of organisms and a greater fraction of silica and clay minerals characteristic of marls . The Green River Formation is an example of a prominent freshwater sedimentary formation containing numerous limestone beds. Freshwater limestone is typically micritic. Fossils of charophyte (stonewort), a form of freshwater green algae, are characteristic of these environments, where the charophytes produce and trap carbonates. Limestones may also form in evaporite depositional environments . Calcite

1854-523: A mechanism for dolomitization, with one 2004 review paper describing it bluntly as "a myth". Ordinary seawater is capable of converting calcite to dolomite, if the seawater is regularly flushed through the rock, as by the ebb and flow of tides (tidal pumping). Once dolomitization begins, it proceeds rapidly, so that there is very little carbonate rock containing mixed calcite and dolomite. Carbonate rock tends to be either almost all calcite/aragonite or almost all dolomite. About 20% to 25% of sedimentary rock

1957-411: A passage runs through the middle of the building. This entrance passage and first court follow the common, though considerably modified, Maltese megalithic design. A separate entrance gives access to four enclosures, which are independent of each other and replace the north-westerly apse. L-Imnajdra temples lies in a hollow 500 metres from Ħaġar Qim. It is another complex site in its own right, and it

2060-448: A plausible source of mud. Another possibility is direct precipitation from the water. A phenomenon known as whitings occurs in shallow waters, in which white streaks containing dispersed micrite appear on the surface of the water. It is uncertain whether this is freshly precipitated aragonite or simply material stirred up from the bottom, but there is some evidence that whitings are caused by biological precipitation of aragonite as part of

2163-449: A radial rather than layered internal structure, indicating that they were formed by algae in a normal marine environment. Peloids are structureless grains of microcrystalline carbonate likely produced by a variety of processes. Many are thought to be fecal pellets produced by marine organisms. Others may be produced by endolithic (boring) algae or other microorganisms or through breakdown of mollusc shells. They are difficult to see in

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2266-459: A rich variety of pottery forms and decorative techniques. Most shapes tend to be angular, with almost no handles or lugs. The clay tends to be well prepared and fired very hard, while the surface of the scratched ware is also highly polished. This scratched decoration remains standard, but it becomes more elaborate and elegant, the most popular motif being a kind of volute . The Maltese temple complexes were built in different locations, and over

2369-404: A rubble infill known as mazkan in between. The roof of the girna is constructed using corbelling , with each row of stones jutting out slightly from the row below it, gradually reducing the size of the opening until flat stone slabs can be used to span it. This results in a dome-shaped concave ceiling, bearing similarities to ancient beehive tombs . Gravel and torba were usually used to cover

2472-527: A second monument was added in the Tarxien phase, with four apses and a central niche. Before the temples were built, the area had supported a village over a period of roughly twelve centuries. The oldest structure is the eleven-metre-long straight wall to the west of the temples' first entrance. The deposit against it contained material from the first known human occupation of the island, the Għar Dalam phase. Among

2575-453: A wide span of years; while each individual site has its unique characteristics, they all share a common architecture. The approach to the temples lies on an oval forecourt , levelled by terracing if the terrain is sloping. The forecourt is bounded on one side by the temples' own façades , which faces south or south-east. The monuments' façades and internal walls are made up of orthostats , a row of large stone slabs laid on end. The centre of

2678-416: Is a type of carbonate sedimentary rock which is the main source of the material lime . It is composed mostly of the minerals calcite and aragonite , which are different crystal forms of CaCO 3 . Limestone forms when these minerals precipitate out of water containing dissolved calcium. This can take place through both biological and nonbiological processes, though biological processes, such as

2781-560: Is also favored on the seaward margin of shelves and platforms, where there is upwelling deep ocean water rich in nutrients that increase organic productivity. Reefs are common here, but when lacking, ooid shoals are found instead. Finer sediments are deposited close to shore. The lack of deep sea limestones is due in part to rapid subduction of oceanic crust, but is more a result of dissolution of calcium carbonate at depth. The solubility of calcium carbonate increases with pressure and even more with higher concentrations of carbon dioxide, which

2884-482: Is an uncommon mineral in limestone, and siderite or other carbonate minerals are rare. However, the calcite in limestone often contains a few percent of magnesium . Calcite in limestone is divided into low-magnesium and high-magnesium calcite, with the dividing line placed at a composition of 4% magnesium. High-magnesium calcite retains the calcite mineral structure, which is distinct from dolomite. Aragonite does not usually contain significant magnesium. Most limestone

2987-409: Is built, using the same trilithon construction, leading from the first set of apses into another later pair, and either a fifth central or a niche giving the four or five apsial form. In one case, at the Tarxien central temple, the fifth apse or niche is replaced by a further passage, leading to a final pair of apses, making six in all. With the standard temple plan, found in some thirty temples across

3090-402: Is carbonate rock, and most of this is limestone. Limestone is found in sedimentary sequences as old as 2.7 billion years. However, the compositions of carbonate rocks show an uneven distribution in time in the geologic record. About 95% of modern carbonates are composed of high-magnesium calcite and aragonite. The aragonite needles in carbonate mud are converted to low-magnesium calcite within

3193-408: Is centred on a near circular forecourt. Three adjacent temples overlook it from one side, while a terrace from the other separates it from a steep slope that runs down to the sea. The first buildings on the right are small irregular chambers, similar to the enclosures in Ħaġar Qim. Then there is a small trefoil temple, dating from the Ġgantija phase, with pitted decorations. Its unusual triple entrance

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3296-474: Is clusters of peloids cemented together by organic material or mineral cement. Extraclasts are uncommon, are usually accompanied by other clastic sediments, and indicate deposition in a tectonically active area or as part of a turbidity current . The grains of most limestones are embedded in a matrix of carbonate mud. This is typically the largest fraction of an ancient carbonate rock. Mud consisting of individual crystals less than 5 μm (0.20 mils) in length

3399-416: Is commonly white to gray in color. Limestone that is unusually rich in organic matter can be almost black in color, while traces of iron or manganese can give limestone an off-white to yellow to red color. The density of limestone depends on its porosity, which varies from 0.1% for the densest limestone to 40% for chalk. The density correspondingly ranges from 1.5 to 2.7 g/cm . Although relatively soft, with

3502-420: Is controlled largely by the amount of dissolved carbon dioxide ( CO 2 ) in the water. This is summarized in the reaction: Increases in temperature or decreases in pressure tend to reduce the amount of dissolved CO 2 and precipitate CaCO 3 . Reduction in salinity also reduces the solubility of CaCO 3 , by several orders of magnitude for fresh water versus seawater. Near-surface water of

3605-545: Is converted to low-magnesium calcite. Diagenesis is the likely origin of pisoliths , concentrically layered particles ranging from 1 to 10 mm (0.039 to 0.394 inches) in diameter found in some limestones. Pisoliths superficially resemble ooids but have no nucleus of foreign matter, fit together tightly, and show other signs that they formed after the original deposition of the sediments. Silicification occurs early in diagenesis, at low pH and temperature, and contributes to fossil preservation. Silicification takes place through

3708-503: Is deposited close to where it formed, classification of limestone is usually based on its grain type and mud content. Most grains in limestone are skeletal fragments of marine organisms such as coral or foraminifera . These organisms secrete structures made of aragonite or calcite, and leave these structures behind when they die. Other carbonate grains composing limestones are ooids , peloids , and limeclasts ( intraclasts and extraclasts  [ ca ] ). Skeletal grains have

3811-460: Is described as coquinite . Chalk is a soft, earthy, fine-textured limestone composed of the tests of planktonic microorganisms such as foraminifera, while marl is an earthy mixture of carbonates and silicate sediments. Limestone forms when calcite or aragonite precipitate out of water containing dissolved calcium, which can take place through both biological and nonbiological processes. The solubility of calcium carbonate ( CaCO 3 )

3914-617: Is described as micrite . In fresh carbonate mud, micrite is mostly small aragonite needles, which may precipitate directly from seawater, be secreted by algae, or be produced by abrasion of carbonate grains in a high-energy environment. This is converted to calcite within a few million years of deposition. Further recrystallization of micrite produces microspar , with grains from 5 to 15 μm (0.20 to 0.59 mils) in diameter. Limestone often contains larger crystals of calcite, ranging in size from 0.02 to 0.1 mm (0.79 to 3.94 mils), that are described as sparry calcite or sparite . Sparite

4017-462: Is distinguished from micrite by a grain size of over 20 μm (0.79 mils) and because sparite stands out under a hand lens or in thin section as white or transparent crystals. Sparite is distinguished from carbonate grains by its lack of internal structure and its characteristic crystal shapes. Geologists are careful to distinguish between sparite deposited as cement and sparite formed by recrystallization of micrite or carbonate grains. Sparite cement

4120-560: Is one of the first minerals to precipitate in marine evaporites. Most limestone is formed by the activities of living organisms near reefs, but the organisms responsible for reef formation have changed over geologic time. For example, stromatolites are mound-shaped structures in ancient limestones, interpreted as colonies of cyanobacteria that accumulated carbonate sediments, but stromatolites are rare in younger limestones. Organisms precipitate limestone both directly as part of their skeletons, and indirectly by removing carbon dioxide from

4223-406: Is oriented astronomically aligned with the rising sun during solstices and equinoxes ; during the summer solstice the first rays of sunlight light up the edge of a decorated megalith between the first apses, while during the winter solstice the same effect occurs on a megalith in the opposite apse. During the equinox, the rays of the rising sun pass straight through the principal doorway to reach

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4326-473: Is otherwise chemically fairly pure, with clastic sediments (mainly fine-grained quartz and clay minerals ) making up less than 5% to 10% of the composition. Organic matter typically makes up around 0.2% of a limestone and rarely exceeds 1%. Limestone often contains variable amounts of silica in the form of chert or siliceous skeletal fragments (such as sponge spicules, diatoms , or radiolarians ). Fossils are also common in limestone. Limestone

4429-472: Is produced by decaying organic matter settling into the deep ocean that is not removed by photosynthesis in the dark depths. As a result, there is a fairly sharp transition from water saturated with calcium carbonate to water unsaturated with calcium carbonate, the lysocline , which occurs at the calcite compensation depth of 4,000 to 7,000 m (13,000 to 23,000 feet). Below this depth, foraminifera tests and other skeletal particles rapidly dissolve, and

4532-514: Is secondary dolomite, formed by chemical alteration of limestone. Limestone is exposed over large regions of the Earth's surface, and because limestone is slightly soluble in rainwater, these exposures often are eroded to become karst landscapes. Most cave systems are found in limestone bedrock. Limestone has numerous uses: as a chemical feedstock for the production of lime used for cement (an essential component of concrete ), as aggregate for

4635-456: Is split into five phases; however, the first two of these left mostly pottery shards. The next three phases, starting from the Ġgantija phase, begins in c. 3600 BC, and the last, the Tarxien phase, ends in c. 2500 BC. The Ġgantija phase is named after the Ġgantija site in Gozo . It represents an important development in the cultural evolution of neolithic humans on the islands. To this date belong

4738-464: Is that the sites themselves are evolutionary in nature, in that each successive temple brought with it further refinement to architectural development. Furthermore, in some cases, later Bronze Age peoples built their own sites over the Neolithic temples, thus adding an element of confusion to early researchers who did not have modern dating technology. Sir Temi Żammit , an eminent Maltese archaeologist of

4841-510: The nuraghe of Sardinia , the trulli of Apulia , the bunje of the former Yugoslavia , the borie  [ fr ] of France and other types of huts found in Sicily and Libya . In his 1536 publication Insulae Melitae Descriptio , Jean Quintin mentioned that the Maltese countryside contained many vernacular structures which he called "African huts", and this might have referred to

4944-550: The girna . Larger giren were probably used for human habitation, and it is likely that many were abandoned as isolated rural communities gave way to larger villages and towns in the 17th and 18th centuries. Smaller giren were mostly used to store tools or hay, as temporary shelters for farmers or herders, or to house goats, sheep or other livestock. The frequency of giren near certain quarries , such as in Qala on Gozo , suggests that some were also used as shelters for workmen. Due to

5047-619: The northern part of the main island of Malta . They are especially frequent in the limits of Mellieħa , including the land around Manikata , l-Aħrax tal-Mellieħa , the area around Selmun Palace and the area between Saint Agatha's Tower and Paradise Bay. Over 30 giren can be found in the Majjistral Park . Other areas in the northwestern part of Malta which contain some giren include Żebbiegħ , Bidnija , Dingli , Baħrija and Mtaħleb . The areas where giren are located usually contain rocky outcrops of hard coralline limestone, which

5150-458: The Debdieba site. Others, such as Kordin I and II, were destroyed. The other temples usually consist of only a few scattered megaliths or remains, but some such as Buġibba Temple (which is now in the grounds of a hotel) are in better condition. A few sites, such as Ta' Marżiena, have never been excavated. Tas-Silġ contains few megalithic remains, but many more Bronze Age and later remains since the site

5253-496: The Earth's history. Limestone may have been deposited by microorganisms in the Precambrian , prior to 540 million years ago, but inorganic processes were probably more important and likely took place in an ocean more highly oversaturated in calcium carbonate than the modern ocean. Diagenesis is the process in which sediments are compacted and turned into solid rock . During diagenesis of carbonate sediments, significant chemical and textural changes take place. For example, aragonite

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5356-430: The accumulation of corals and shells in the sea, have likely been more important for the last 540 million years. Limestone often contains fossils which provide scientists with information on ancient environments and on the evolution of life. About 20% to 25% of sedimentary rock is carbonate rock, and most of this is limestone. The remaining carbonate rock is mostly dolomite , a closely related rock, which contains

5459-408: The apses' walls and the external boundary wall is usually filled with loose stones and earth, sometimes containing cultural debris including pottery shards. The main variation in the temples lies in the number of apses found; this may vary to three, four, five or six. If three, they open directly from the central court in a trefoil fashion. In cases of more complex temples, a second axial passage

5562-434: The base of roads, as white pigment or filler in products such as toothpaste or paint, as a soil conditioner , and as a popular decorative addition to rock gardens . Limestone formations contain about 30% of the world's petroleum reservoirs . Limestone is composed mostly of the minerals calcite and aragonite , which are different crystal forms of calcium carbonate ( CaCO 3 ). Dolomite , CaMg(CO 3 ) 2 ,

5665-657: The beds. This may include the formation of vugs , which are crystal-lined cavities within the limestone. Diagenesis may include conversion of limestone to dolomite by magnesium-rich fluids. There is considerable evidence of replacement of limestone by dolomite, including sharp replacement boundaries that cut across bedding. The process of dolomitization remains an area of active research, but possible mechanisms include exposure to concentrated brines in hot environments ( evaporative reflux ) or exposure to diluted seawater in delta or estuary environments ( Dorag dolomitization ). However, Dorag dolomitization has fallen into disfavor as

5768-516: The blocks. The Ta' Ħaġrat temple in Mġarr is on the eastern outskirts of the village, roughly one kilometer from the Ta' Skorba temples . The remains consist of a double temple, made up of two adjacent complexes, both in the shape of a trefoil. The two parts are both less regularly planned and smaller in size than many of the other neolithic temples in Malta, and no blocks are decorated. Sir Temi Żammit excavated

5871-416: The craftsmanship of pottery, as well as in sculptural decoration, both free-standing and in relief. Spiral reliefs resembling those at Tarxien once adorned the Ġgantija temples, but have faded to a level where they are only clearly recognisable in a series of drawings made by the artist Charles Frederick de Brocktorff in 1829, immediately after the temples' excavation. The Tarxien phase is characterised by

5974-690: The curved walls of the Manikata parish church , which is regarded as one of the most iconic 20th century churches in Malta. England also designed a residential building called Villa Girna which used the vernacular huts as a source of inspiration, but it was never actually constructed. [REDACTED] Media related to Giren at Wikimedia Commons Megalithic Temples of Malta The Megalithic Temples of Malta ( Maltese : It-Tempji Megalitiċi ta' Malta ) are several prehistoric temples, some of which are UNESCO World Heritage Sites , built during three distinct periods approximately between 3600 BC and 2500 BC on

6077-462: The depositional fabric of carbonate rocks. Dunham divides the rocks into four main groups based on relative proportions of coarser clastic particles, based on criteria such as whether 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

6180-469: The deposits are highly porous, so that they have a spongelike texture, they are typically described as tufa . Secondary calcite deposited by supersaturated meteoric waters ( groundwater ) in caves is also sometimes described as travertine. This produces speleothems , such as stalagmites and stalactites . Coquina is a poorly consolidated limestone composed of abraded pieces of coral , shells , or other fossil debris. When better consolidated, it

6283-409: The domestic deposits found in this material, which included charcoal and carbonised grain, there were several fragments of daub, accidentally baked. The charcoal fragments were then radiocarbon dated, and their age analysis stood at 4850 BC. Ħaġar Qim stands on a ridge some two kilometers away from the villages of Qrendi and Siġġiewi . Its builders used the soft globigerina limestone that caps

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6386-460: The earliest datable temples and the first two, if not three, of the stages of development in their ground plan: the lobed or kidney-shaped plan found in Mġarr east, the trefoil plan evident in Skorba, Kordin and various minor sites, and the five-apsed plan Ġgantija South, Tarxien East. The Saflieni phase constitutes a transitional phase between two major periods of development. Its name derives from

6489-406: The earth's oceans are oversaturated with CaCO 3 by a factor of more than six. The failure of CaCO 3 to rapidly precipitate out of these waters is likely due to interference by dissolved magnesium ions with nucleation of calcite crystals, the necessary first step in precipitation. Precipitation of aragonite may be suppressed by the presence of naturally occurring organic phosphates in

6592-450: The end of the Xagħra plateau , facing towards the south-east. Its presence was known for a very long time, and even before any excavations were carried out a largely correct plan of its layout was drawn by Jean-Pierre Houël in the late eighteenth century. In 1827, the site was cleared of debris—the soil and remains being lost without proper examination. The loss resulting from this clearance

6695-413: The façade have been destroyed to ground level. What remains are the stone paving of the entrance passage, with its perforations, the torba floors, and a large upright slab of coralline limestone. The north wall is in better shape; originally the entrance opened on a court, but the doorway was later closed off in the Tarxien phase, with altars set in the corners formed by the closure. East of this temple,

6798-411: The façades is usually interrupted by an entrance doorway forming a trilithon , a pair of orthostats surmounted by a massive lintel slab. Further trilithons form a passage, which is always paved in stone. This in turn opens onto an open space, which then gives way to the next element, a pair of D-shaped chambers, usually referred to as ' apses ', opening on both sides of the passage. The space between

6901-399: The first refers to the grains and the second to the cement. For example, a limestone consisting mainly of ooids, with a crystalline matrix, would be termed an oosparite. 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. Robert J. Dunham published his system for limestone in 1962. It focuses on

7004-572: The formation of distinctive minerals from the silica and clay present in the original limestone. Two major classification schemes, the Folk and Dunham, are used for identifying the types of carbonate rocks collectively known as limestone. 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;

7107-425: The former uses the word in conjunction with the marker of possession, the latter adds the word 'Qim' , which is either a form of the Maltese word for 'worship', or an archaic form of the word meaning 'standing'. Maltese folklore describes giants as having built the temples, which led to the name Ġgantija, meaning 'Giants' tower'. The Maltese linguist Joseph Aquilina believed that Mnajdra ( Arabic : منيدرة)

7210-429: The geologic record are called bioherms . Many are rich in fossils, but most lack any connected organic framework like that seen in modern reefs. The fossil remains are present as separate fragments embedded in ample mud matrix. Much of the sedimentation shows indications of occurring in the intertidal or supratidal zones, suggesting sediments rapidly fill available accommodation space in the shelf or platform. Deposition

7313-464: The innermost central niche. The Tarxien temple complex is found some 400 metres to the east of the Hypogeum of Ħal-Saflieni . The three temples found here were seriously excavated in the early twentieth century by Temi Żammit. Unlike the other sites, this temple is bounded on all sides by modern urban development; however, this does not detract from its value. One enters into the first great forecourt of

7416-520: The island country of Malta . They had been claimed as the oldest free-standing structures on Earth until the discovery of Göbekli Tepe in Turkey. Archaeologists believe that these megalithic complexes are the result of local innovations in a process of cultural evolution. This led to the building of several temples of the Ġgantija phase (3600–3000 BC), culminating in the large Tarxien temple complex , which remained in use until 2500 BC. After this date,

7519-475: The island which consist of Upper Coralline Limestone, such as Xagħra , Nadur and Qala . Giren are huts constructed out of undressed dry stone , and they were usually built out of loose pieces of coralline limestone , which were either obtained through quarrying or through clearing loose stones from a piece of land in order to allow for it to be cultivated. The walls are usually around 90 cm (35 in) thick, and they consist of two skins of stone with

7622-473: The islands, there is a certain amount of variation both in the number of apses, and in the overall length—ranging from 6.5m in the Mnajdra east temple to 23m in the six-apsed Tarxien central temple. The external walls were usually built of coralline limestone , which is harder than the globigerina limestone used in the internal sections of the temples. The softer globigerina was used for decorative elements within

7725-465: The late nineteenth century, had dated the Neolithic temples to 2800 BC and the Tarxien Bronze Age culture to 2000 BC. These dates were considered "considerably too high" by scholars, who proposed a reduction of half a millennium each. However, radiocarbon testing favoured Żammit's dating. A theory that the temple art was connected with an Aegean -derived culture collapsed with this proof of

7828-410: The ocean basins, but limestone is rarely preserved in continental slope and deep sea environments. The best environments for deposition are warm waters, which have both a high organic productivity and increased saturation of calcium carbonate due to lower concentrations of dissolved carbon dioxide. Modern limestone deposits are almost always in areas with very little silica-rich sedimentation, reflected in

7931-500: The primitive nature of their construction, giren were not particularly influenced by changes which occurred in other aspects of Maltese architecture over the centuries. Assigning a date of construction to a particular girna is difficult unless it is documented in other evidence, but it is believed that many of the existing structures are relatively recent. The first study of the girna was made by Paul Cassar in 1961, and several other studies have been published since then, most notably

8034-426: The reaction: Fossils are often preserved in exquisite detail as chert. Cementing takes place rapidly in carbonate sediments, typically within less than a million years of deposition. Some cementing occurs while the sediments are still under water, forming hardgrounds . Cementing accelerates after the retreat of the sea from the depositional environment, as rainwater infiltrates the sediment beds, often within just

8137-482: The relative purity of most limestones. Reef organisms are destroyed by muddy, brackish river water, and carbonate grains are ground down by much harder silicate grains. Unlike clastic sedimentary rock, limestone is produced almost entirely from sediments originating at or near the place of deposition. Limestone formations tend to show abrupt changes in thickness. Large moundlike features in a limestone formation are interpreted as ancient reefs , which when they appear in

8240-472: The remains excavated at Skorba. The temples were the result of several phases of construction from 5000 to 2200 BC . There is evidence of human activity in the islands since the Early Neolithic Period ( c.  5000 BC ), attested by pottery shards, evidence of fires, and bones. The dating and understanding of the various phases of activity in the temples is not easy. The main problem found

8343-406: The ridge to construct the temple. One can clearly see the effects of this choice in the outer southern wall, where the great orthostats are exposed to the sea-winds. Here the temple has suffered from severe weathering and surface flaking over the centuries. The temple's façade is typical, with a trilithon entrance, a bench and orthostats. It has a wide forecourt with a retaining wall, through which

8446-460: The rock. The Dunham scheme is more useful for hand samples because it is based on texture, not the grains in the sample. A revised classification was proposed by Wright (1992). It adds some diagenetic patterns to the classification scheme. Travertine is a term applied to calcium carbonate deposits formed in freshwater environments, particularly waterfalls , cascades and hot springs . Such deposits are typically massive, dense, and banded. When

8549-400: The roof through an external staircase or ramp. There are also examples of giren with two floors, consisting of one hut built on top of another. Mangers were sometimes found inside giren used to raise livestock. The huts are prone to collapse if they are left without proper maintenance. In the 1960s, the Maltese architect Richard England drew inspiration from the girna when designing

8652-408: The roof, while sometimes a pebble-like material called ċagħqija was used for this purpose. Most giren have a circular plan, but there are some which are square, rectangular or oval-shaped. They usually have a single door facing east or south, and this opening is spanned by lintels , while some also have windows. Some giren were additionally buttressed by rubble walls, and a few allow access to

8755-479: The sediments increases. Chemical compaction takes place by pressure solution of the sediments. This process dissolves minerals from points of contact between grains and redeposits it in pore space, reducing the porosity of the limestone from an initial high value of 40% to 80% to less than 10%. Pressure solution produces distinctive stylolites , irregular surfaces within the limestone at which silica-rich sediments accumulate. These may reflect dissolution and loss of

8858-662: The sediments of the ocean floor abruptly transition from carbonate ooze rich in foraminifera and coccolith remains ( Globigerina ooze) to silicic mud lacking carbonates. In rare cases, turbidites or other silica-rich sediments bury and preserve benthic (deep ocean) carbonate deposits. Ancient benthic limestones are microcrystalline and are identified by their tectonic setting. Fossils typically are foraminifera and coccoliths. No pre-Jurassic benthic limestones are known, probably because carbonate-shelled plankton had not yet evolved. Limestones also form in freshwater environments. These limestones are not unlike marine limestone, but have

8961-410: The site in 1925–27. A village on the site that pre-dates the temples by centuries has provided plentiful examples of what is now known as Mġarr phase pottery. The importance of this site lies less in the remains than in the information garnered from their excavations. This monument has a typical three-apsed shape of the Ġgantija phase, of which the greater part of the first two apses and the whole of

9064-461: The site of the Hypogeum of Ħal-Saflieni . This period carried forward the same characteristics of the Ġgantija pottery shapes, but it also introduces new biconical bowls. The Tarxien phase marks the peak of the temple civilisation. This phase is named after the temple-complex at Tarxien, a couple of kilometres inland from the Grand Harbour . To it belong the last two stages in the development of

9167-499: The sites are managed by Heritage Malta , while ownership of the surrounding lands varies from site to site. Apart from these, there are other megalithic temples in Malta which are not included in the UNESCO World Heritage list. Many of the names used to refer to the different sites carry a link with the stones used for their building. The Maltese word for boulders, 'ħaġar', is common to Ta' Ħaġrat and Ħaġar Qim . While

9270-419: The southern temple, marked by its rounded façade and a cistern, which is attributed to the temple. The earliest temple to the north-east was built between 3600 and 3200 BC; it consisted of two parallel sets of semi-circular apses, with a passage in the middle. The south and east temples were built in the Tarxien phase, between 3150 and 2500 BC. The second one has three parallel semi-circular apses, connected by

9373-485: The standing slabs being decorated with flat raised spirals. In one of the chambers, two bulls and a sow are cut in low relief across one of the walls. The third temple has a carelessly-built frame, but most of its standing stones are richly decorated with carved patterns. Malta has various other megalithic temples and related sites apart from those included in the UNESCO World Heritage list. These include: Some of these sites were excavated but afterwards reburied, such as

9476-445: The temple plan. The western temple at Ġgantija represents, along with other units in Tarxien, Ħaġar Qim and L-Imnajdra, the penultimate stage in development, that is, the introduction of a shallow niche instead of an apse at the far end of the temple. The final stage is testified in only one temple, the central unit at Tarxien, with its three symmetrical pairs of apses. The Temple culture reached its climax in this period, both in terms of

9579-614: The temple-building culture disappeared. The Ġgantija temples were listed as a UNESCO World Heritage Site in 1980. In 1992, the UNESCO Committee further extended the existing listing to include five other megalithic temple sites. These are Ħaġar Qim (in Qrendi ), Mnajdra (in Qrendi), Ta' Ħaġrat Temples (in Mġarr ), Skorba Temples (in Żebbiegħ ) and Tarxien Temples (in Tarxien ). Nowadays,

9682-467: The temples' elder origins. The development of the chronological phases, based on recalibrated radiocarbon dating , has split the period up to the Bronze Age in Malta into a number of phases. The first evidence of human habitation in the Neolithic occurred in the Għar Dalam phase, in c. 5000 BC. The Temple period, from c. 4100 BC to roughly 2500 BC, produced the most notable monumental remains. This period

9785-462: The temples, usually carvings. These features are usually sculpted in relief, and they show a variety of designs linked to vegetative or animal symbolism . These usually depict running spiral motifs , trees and plants as well as a selection of animals. Although in their present form the temples are unroofed, a series of unproven theories regarding possible ceiling and roof structures have been debated for several years. The Ġgantija temples stand at

9888-533: The water by photosynthesis and thereby decreasing the solubility of calcium carbonate. Limestone shows the same range of sedimentary structures found in other sedimentary rocks. However, finer structures, such as lamination , are often destroyed by the burrowing activities of organisms ( bioturbation ). Fine lamination is characteristic of limestone formed in playa lakes , which lack the burrowing organisms. Limestones also show distinctive features such as geopetal structures , which form when curved shells settle to

9991-553: The water. Although ooids likely form through purely inorganic processes, the bulk of CaCO 3 precipitation in the oceans is the result of biological activity. Much of this takes place on carbonate platforms . The origin of carbonate mud, and the processes by which it is converted to micrite, continue to be a subject of research. Modern carbonate mud is composed mostly of aragonite needles around 5 μm (0.20 mils) in length. Needles of this shape and composition are produced by calcareous algae such as Penicillus , making this

10094-418: Was copied on a larger scale in the second temple. The middle temple was actually the last to be built, inserted between the others in the Tarxien phase, after 3100 BC. It has four apses and a niche. The third temple, built early in the Tarxien phase and so second in date, opens on the court at a lower level. It has a markedly concave façade, with a bench, orthostats and trilithon entrance. The southern temple

10197-416: Was likely deposited in pore space between grains, suggesting a high-energy depositional environment that removed carbonate mud. Recrystallized sparite is not diagnostic of depositional environment. Limestone outcrops are recognized in the field by their softness (calcite and aragonite both have a Mohs hardness of less than 4, well below common silicate minerals) and because limestone bubbles vigorously when

10300-473: Was partially compensated by the German artist Brochtorff, who painted the site within a year or two from the removal of the debris. This is the only practical record of the clearance. A boundary wall encloses the temples. The southerly one is the elder, and is better preserved. The plan of the temple incorporates five large apses, with traces of the plaster that once covered the irregular wall still clinging between

10403-509: Was the diminutive of 'mandra' ( Arabic : مندرة), meaning a plot of ground planted with cultivated trees (the same usage is colloquial in Egyptian Arabic today); a less likely derivation is from the Arabic root 'manzara ( Arabic : منظرة), meaning 'a place with commanding views.' The Tarxien temples owe their name to the locality where they were found (from Tirix , meaning a large stone), as were

10506-452: Was the main material used in the huts' construction. These areas tended to lack more workable materials such as globigerina limestone . This might explain why giren are less common in the southern part of Malta and on the island of Gozo , where globigerina limestone is abundant and where it was often used to construct ashlar masonry buildings. Most giren in Gozo are clustered in the parts of

10609-482: Was used until at least the ninth century AD. Apart from these, cart ruts were found at Misraħ Għar il-Kbir , but these may or may not date from the temple period. A submerged site known as Ġebel ġol-Baħar possibly exists off the coast of Malta, but it is not proven to be a megalithic temple. 36°02′50″N 14°16′09″E  /  36.04722°N 14.26917°E  / 36.04722; 14.26917 Limestone Limestone ( calcium carbonate CaCO 3 )

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