Naleziste zkamenelin / Fossil Site - Houbuv Lom EarthCache

Protoze tentokrat je listing velice obsahly, podminky k logovani jsou tady hned na zacatku.

K zalogovani splnte nasledujici - najdete na souradnicich 49°54.847 014°03.902 informacni tabuli a vyhledejte odpovedi na otazky: 1) Jak stary je Koneprusky utes? 2) Kolik druhu zivocichu zde bylo popsano? 3) Jaka byla skutecna velikost Lioharpes venulosus? (na tabuli je obrazek, pokud tam neni, jste u spatne cedule a zaskocte si na souradnice o par radku vyse :)) a samozrejme prilozte vase foto / nebo vasi GPSky s tabuli v lomu pripadne vasich nalezu.

zdroj www.paleontologie.cz

Zkameneliny / Fosilie
(z latinského fossus, doslova "byt vykopan")

V sirsim slova smyslu jsou slovem fosilie oznacovany zkamenele i nezkamenele zbytky a otisky jinych nez recentnich organismu. Casto se za fosilie povazuji take stopy po cinnosti techto organismu, ktere se odborne nazyvaji bioglyfy, jsou to otisky koncetin, nebo jen drobne dirky po vrtani ci cesticky po lezeni.

Zkameneni je mimoradne vzacny vyskyt, protoze vetsina casti tel odumrelych zivocichu a rostlin ma tendenci se rozkladat pomerne rychle po smrti. K tomu, aby organismus „zkamenel“ zustava zpravidla nutne, aby byl pokryt usazeninami co nejdrive po smrti. (Existuji i drobne vyjimky, napriklad pokud organismus zmrzne, vysusi se, nebo se ocitne v prostredi bez pristupu kysliku.)

Proces fosilizace muze mit ruzny prubeh, ktery je vsak zasadni a odrazi se v mire zachovalosti fosilie.

Fosilizacni proces jako soubor slozitych dilcich procesu vede k ruznemu, kvalitativne odlisnemu, uchovani fosilnich organizmu. Podle zpusobu zachovani rozdelujeme fosilie na dve skupiny:

1. fosilie prave - v jejich slozeni nedoslo k podstatnym zmenam v dusledku fosilizacnich a diagenetickych procesu. Uchovavaji se bud' nezmenene schranky (napr. schranky mekkysu), zuby obratlovcu (diky velice odolnemu dentinu) nebo se dochovava i mekka tkan zivocichu vysusenim v aridnim prostredi nebo v dynamickem prostredi jeskyni (takto dochovane zbytky se oznacuji jako mumie). Jako pseudomumie se oznacuji zivocichove zachovani i s mekkou tkani pusobenim extremne nizkych teplot. Pseudomumie mohou vznikat i v prostredi bazin, ozokeritovych akumulaci, zivicnych latek, evaporitu.

2. fosilie v sirsim slova smyslu - u takto zachovanych fosilii doslo k nahrazeni jejich puvodnich schranek nebo tkani jinou mineralni latkou, a to dokonce i opakovane (puvodne pyriticke fosilie mohou v oxidacnich podminkach prejit na limonitizovane atd.).

a) jadro - sediment vyplnuje vnitrni prostor schranky. Na vnejsim povrchu jadra (take se oznacuje jako kamenne jadro) se otiskuji vnitrni struktury schranky (svalove vtisky, otisky plaste, vaskularni system ap.). Sediment muze vyplnit cely vnitrni prostor schranky, jadro se pak oznacuje jako jadro uplne, v opacnem pripade nedojde k vyplneni cele schranky (sedimentu stoji v ceste napr. prepazky ve fragmokonu u hlavonozcu) a vznika jadro neuplne. Rozpoustela-li se schranka v nezpevnenem sedimentu a na povrchu jadra se otiskne skulptura povrchu schranky (sediment je v hydroplastickem stavu), pak tento zpusob zachovani se nazyva jadro skulpturni. Nekdy (u plochych krunyru trilobitu) se na povrchu jejich jader prolinaji struktury jadra vnitrniho i struktury povrchu krunyre a vznika jadro slozene.

b) otisk - znazornuje charakter vnejsiho povrchu organizmu, napr. zachovaneho jako jadro. Jedna se tedy o protiotisk (utvar konkavni). Z ciste deskriptivniho hlediska se otisk oznacuje jako negativ a jadro (ci zachovana schranka) jako pozitiv (ma konvexni relief).

c) vylitek - jedna se o jadro v sirsim slova smyslu. Po vytvoreni jadra (vnitrniho) a po rozpusteni schranky vznikne mezi jadrem a protiotiskem dutina. Jestlize se vyplni sedimentem nebo fosilizacnim mineralem vznikne vylitek.

d) odlitek - vznikne vyplnenim dutiny po schrance i jejiho vnitrniho prostoru.
(www.wikipedia.org, geologie.vsb.cz)

Lokalita Houbuv lom

Houbuv lom je stary zruseny romanticky lom na jizni strane navrsi Zlateho kone, ktere je jednou z nejbohatsich svetovych paleontologickych lokalit ve spodnim devonu. Bylo zde popsano pres 500 druhu zivocichu. Devonske vrstvy tvori v jiznim okoli Koneprus rozsahlou plochou synklinalu, jejiz jadro s nejmladsimi vrstvami lezi prave v oblasti Zlateho kone. Severni ohraniceni synklinaly je tektonicke, podel tzv. ockovskeho presmyku byly na pevny masiv konepruskych a nadloznich vapencu nasunuty od severu starsi spodnodevonske a silurske vrstvy.

V Houbove lomu jsou odkryty polohy konepruskych vapencu a nadlozni suchomastske vapence. Konepruske vapence vznikaly v tropickem mori asi pred 400 miliony let. Vyznacuji se belavym zbarvenim a masivnim charakterem bez patrne vrstevnatosti. Na Zlatem koni tvori typicky utes, v nemz lze rozeznat dva hlavni geneticke typy vapencu – biogenni a biodetriticke. Biogenni vapence vznikly aktivni utesotvornou cinnosti prisedlych organismu, hlavne vapnitych ras, stromatopor, lilijic, koralu aj. Tyto vapence predstavuji vlastni jadro utesu. Do Houbova lomu zasahuji biogenni vapence jen prstovite, vlastni centrum utesu lezelo severneji a je vyborne odkryto ve vychodni stene tzv. Cisarskeho lomu na Zlatem koni. Biodetriticke vapence predstavuji jednak drt, ktera vznikla rozrusovanim utesu cinnosti vln i organismu, jednak nahromadene zbytky tech organismu, ktere v tesne blizkosti utesu a na jeho svazich nalezaly nejvhodnejsi zivotni podminky. Byli to zejmena ramenonozci, mechovky, korali, plzi aj. Tyto vapence vyplnovaly nerovnosti utesu a tvorily kolem pevneho jadra mohutne osypy, jejichz celkovy objem podstatne prevysuje podil vapencu biolitickych. Odkryvy techto vapencu s hojnymi fosiliemi se nachazeji na Zlatem koni v Houbove lomu. Konepruske vapence obsahuji velmi hojnou faunu, reprezentujici vetsinu zastupcu v te dobe zijicich zivocisnych skupin. K nejhojnejsim zkamenelinam patri lilijice, ramenonozci (popsano kolem 100 druhu), mechovky, korali, stromatopory, plzi (popsano pres 100 druhu), mlzi, mekkysi, trilobiti (popsano pres 50 druhu) aj. Fauna konepruskych vapencu mimo konepruskou oblast je pomerne chuda.
(www.otevrena-veda.cz)

zajimavost: Pokud se uprostred lomu - souradnice kese - zadivate na severni stenu lomu, uvidite nahore otvor, kterym byly roku 1950 (znovu)objeveny Konepruske jeskyne - nejvetsi jekynni komplex v Cechach. Ale to uz je tema jine Earthcache.

pristup: Do Houbova lomu se pohodlne dostanete z parkoviste Konepruskych jeskyni - polni cesta z jihozapadniho rohu parkovaci plochy - cca 600m. A mene pohodlne - od vychodu z Konepruskych jeskyni na zapad a pak cesticce dolu podel dreveneho zabradli nad severozapdni a zapadni stenou lomu.

EN: Fossils

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Fossils (from Latin fossus, literally "having been dug up") are the preserved remains or traces of animals, plants, and other organisms from the remote past. The totality of fossils, both discovered and undiscovered, and their placement in fossiliferous (fossil-containing) rock formations and sedimentary layers (strata) is known as the fossil record. The study of fossils across geological time, how they were formed, and the evolutionary relationships between taxa (phylogeny) are some of the most important functions of the science of paleontology. Such a preserved specimen is called a "fossil" if it is older than some minimum age, most often the arbitrary date of 10,000 years ago. Hence, fossils range in age from the youngest at the start of the Holocene Epoch to the oldest from the Archaean Eon several billion years old. The observations that certain fossils were associated with certain rock strata led early geologists to recognize a geological timescale in the 19th century. The development of radiometric dating techniques in the early 20th century allowed geologists to determine the numerical or "absolute" age of the various strata and thereby the included fossils.

Like extant organisms, fossils vary in size from microscopic, such as single bacterial cells only one micrometer in diameter, to gigantic, such as dinosaurs and trees many meters long and weighing many tons. A fossil normally preserves only a portion of the deceased organism, usually that portion that was partially mineralized during life, such as the bones and teeth of vertebrates, or the chitinous exoskeletons of invertebrates. Preservation of soft tissues is rare in the fossil record. Fossils may also consist of the marks left behind by the organism while it was alive, such as the footprint or feces (coprolites) of a reptile. These types of fossil are called trace fossils (or ichnofossils), as opposed to body fossils. Finally, past life leaves some markers that cannot be seen but can be detected in the form of biochemical signals; these are known as chemofossils or biomarkers.

Fossilization is an exceptionally rare occurrence, because most components of formerly-living things tend to decompose relatively quickly following death. In order for an organism to be fossilized, the remains normally need to be covered by sediment as soon as possible. However there are exceptions to this, such as if an organism becomes frozen, desiccated, or comes to rest in an anoxic (oxygen-free) environment. There are several different types of fossils and fossilization processes.

Due to the combined effect of taphonomic processes and simple mathematical chance, fossilization tends to favor organisms with hard body parts, those that were widespread, and those that existed for a long time before going extinct. On the other hand, it is very unusual to find fossils of small, soft bodied, geographically restricted and geologically ephemeral organisms, because of their relative rarity and low likelihood of preservation.

Larger specimens (macrofossils) are more often observed, dug up and displayed, although microscopic remains (microfossils) are actually far more common in the fossil record.

Some casual observers have been perplexed by the rarity of transitional species within the fossil record. The conventional explanation for this rarity was given by Darwin, who stated that "the extreme imperfection of the geological record," combined with the short duration and narrow geographical range of transitional species, made it unlikely that many such fossils would be found. Simply put, the conditions under which fossilization takes place are quite rare; and it is highly unlikely that any given organism will leave behind a fossil. Eldredge and Gould developed their theory of punctuated equilibrium in part to explain the pattern of stasis and sudden appearance in the fossil record. Furthermore, in the strictest sense, nearly all fossils are "transitional," due to the improbability that any given fossil represents the absolute termination of an evolutionary path.

Types of preservation:
1) Permineralization

Permineralization occurs after burial, as the empty spaces within an organism (spaces filled with liquid or gas during life) become filled with mineral-rich groundwater and the minerals precipitate from the groundwater, thus occupying the empty spaces. This process can occur in very small spaces, such as within the cell wall of a plant cell. Small scale permineralization can produce very detailed fossils. For permineralization to occur, the organism must become covered by sediment soon after death or soon after the initial decaying process. The degree to which the remains are decayed when covered determines the later details of the fossil. Some fossils consist only of skeletal remains or teeth; other fossils contain traces of skin, feathers or even soft tissues. This is a form of diagenesis.

2) Casts and molds

In some cases the original remains of the organism have been completely dissolved or otherwise destroyed. When all that is left is an organism-shaped hole in the rock, it is called an external mold. If this hole is later filled with other minerals, it is a cast. An internal mold is formed when sediments or minerals fill the internal cavity of an organism, such as the inside of a bivalve or snail.

3) Replacement and recrystallization

Replacement occurs when the shell, bone or other tissue is replaced with another mineral. In some cases mineral replacement of the original shell occurs so gradually and at such fine scales that microstructural features are preserved despite the total loss of original material. A shell is said to be recrystallized when the original skeletal compounds are still present but in a different crystal form, as from aragonite to calcite.

4) Compression fossils

Compression fossils, such as those of fossil ferns, are the result of chemical reduction of the complex organic molecules composing the organism's tissues. In this case the fossil consists of original material, albeit in a geochemically altered state. Often what remains is a carbonaceous film. This chemical change is an expression of diagenesis.

5) Bioimmuration

Bioimmuration is a type of preservation in which a skeletal organism overgrows or otherwise subsumes another organism, preserving the latter, or an impression of it, within the skeleton. Usually it is a sessile skeletal organism, such as a bryozoan or an oyster, which grows along a substrate, covering other sessile encrusters. Sometimes the bioimmured organism is soft-bodied and is then preserved in negative relief as a kind of external mold. There are also cases where an organism settles on top of a living skeletal organism which grows upwards, preserving the settler in its skeleton. Bioimmuration is known in the fossil record from the Ordovician to the Recent.

To sum up, fossilization processes proceed differently for different kinds of tissues and under different kinds of conditions.
(www.wikipedia.org)

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Fossil Site Houbuv Lom

Houbuv Lom (Houba Quarry) is old romantic abandoned quarry at the side of Zlaty kun (Golden Horse hill). It is one of the richest palaeontological sites from the Lower Devonian period in the world and more than 500 animal species have been recorded here. To the south of Koneprusy the Devonian layers form an extensive flat syncline, the core of which contain the youngest layers lie in the Zlatý kun area. The northern edge of this syncline is of tectonic origin and runs along the Ockov reverse slip-fault, where older Lower Devonian and Silurian limestones were thrust from the north to lay on top of the firm Koneprusy Massif and the overlaying limestones.

Positions of Koneprusy limestones and the overlying Suchomasty limestone are exposed in the Houba Quarry. Koneprusy limestone was formed in a tropical sea around 400 million years ago, and is characterized by its bleached white appearance and massive structure without apparent layering. At Zlaty kun this limestone forms a typical reef, in which we can recognize the two main genetic types of limestone – biogenic and biodetritic. Biogenic limestone was formed by active reef-building activity of static organisms especially calcareous algae seaweeds, stromatopores, sea-lilies, corals etc. These limestones represent the core of the reef. Biogenic limestones only reach into the Houbuv lom Quarry in a finger-like manner as the centre of the reef lay further to the north, where it is very clearly exposed in the eastern wall of the Cisarsky lom Quarry at Zlaty kun Hill. Biodetritic limestone is built of grit (detritus) which was broken away from the reef by wave action, and also of collections of the remains of animals which found their most suitable conditions on the slopes around the reef and died there. These were predominantly brachiopods, false corals, corals, gastropods etc. These limestones filled in the gaps in the reef and formed massive banks around the firm core of the reef. The total volume of this type is far greater than, the volume of “core” limestone. These limestone types with an abundance of fossils can be seen at the Houba Quarry on Zlaty kun Hill. The Koneprusy limestone is extremely rich in fossils with representatives of most of the animal groups which lived at that time. The most abundant fossils are the sea-lilies, brachiopods (around 100 species recorded), clams, molluscs, trilobites (more than 50 species recorded), false corals, corals, stromatopores etc. The fauna content of the Koneprusy limestone outside of the Koneprusy area is relatively poor.
(www.otevrena-veda.cz)

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Further interesting information: at the northen quarry's rock wall upword you can see original big hole, through which were in 1950 discovered Koneprusy caves - the largest cave system in Bohemia.

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To the quarry you can easy walk the path 600 meters from Koneprusy cave parking - southwest direction.

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To log the earthcache, find information board of the site (49°54.847 014°03.902) and answer the questions: 1) How old is Koneprusy reef? 2) How many species were found at the site? 3) What was a real size of Lioharpes venulosus? and upload photo with you (or your gps, if you are too shy ;)) and the board.

zdroj www.paleontologie.cz