Dalbyover Kalkgrav
OBS: Hunde har ikke adgang i kalkgraven!
I Dalbyover Nord for Randers findes et åbent kalkbrud, hvor der brydes kalk til brug i landbruget. Man har brudt kalk her siden 1928 og det er et af de sidste kalkbrud i Danmark. Den kalk der findes her er af typen slamkalk.
English:
Dalbyover chalk quarry.
Please note: No dogs in the quarry!
Fossils collected in the quarry
In Dalbyover North of Randers you will find an open chalk quarry. The chalk is used in agriculture for improvement of the soil and has been mined since 1928. The type of chalk in Dalbyover is sludge chalk.
Sådan dannes kalken:
Kalk er i virkeligheden skeletrester fra forhistoriske dyr, der levede i havet. Kalken her er dannet af såkaldte coccolither, som er små kalkplader der omgav mikroskopiske alger. Derfor kaldes denne type kalk også cocolithkalk. Cocolitherne levede i de øverste 50 meter af det forhistoriske hav. Når algerne døde sank kalkpladerne langsomt ned mod bunden og blev undervejs spist af nogle af de vandlevende organismer, der fandtes . På den måde blev cocolithresterne kittet sammen. Når de nåede bunden blev de atter føde for de dyr, som levede dér. F.eks. søspindsvin som udnyttede de rester af organisk materiale der sad i skallerne. Faktisk menes cocolithresterne at have været igennem op mod 100 forskellige dyrs tarmsystem inden de endte deres cyklus. Der kan ikke have været meget næringsværdi i til sidst! Efterhånden blev cocolithresterne til en slamlignende masse, som sidenhen pressedes sammen til den hårde kalk vi kender i dag.
English:How the chalk is formed:
Actually chalk is formed of skeletons from prehistoric organisms that lived in the sea. The chalk is formed of so called coccoliths which are tiny plates of chalk surrounding microscopic algae. Therefore this kind of chalk is also called coccolith chalk. The coccoliths lived in the upper 50 meters of the prehistoric sea. When the algae died the chalk plates sank down towards the seabed. On their way down they were eaten by other organisms that lived in the sea. Through this process the chalk plates were cemented together. As they reached the bottom they became food for the animals who lived there. Sea urchins, for example, who utilized the residues of food in the plates. Actually it is estimated that the algae plates passed up till 100 different species and their gastric intestinals before they ended their life cyclus! Ther nutritional value must have been very limited at this point! After many the residues from the coccoliths were compacted into what we know today as chalk.
coccolith
Den kalk du kan se i Dalbyover Kalkbrud er dannet for ca. 65 millioner år siden i den tid, der kaldes Danien. Danien kom umiddelbart efter kridttiden. Da kalken blev dannet på havbunden foregik det dér hvor det Nordlige Italien i dag befinder sig. Men på grund af kontinentalpladernes bevægelser er den tidligere havbund nu altså her! Efterfølgende aflejredes mange lag ovenpå kalken, men enkelte steder ligger kalken så tæt på jordoverfladen som her i Dalbyover.
English:The chalk seen in Dalbyover quarry was made 65 million years ago in during the period called Danian. Danian came immediately after Cretaceous period. When the chalk was formed on the sea bed it took place where the Northern part of Italy is today. But as a result of the the movements of the continental plates the former sea bed is now here. Subsequently many layers were deposited on the chalk but a few places the chalk is close to the surface as here in Dalbyover.
oversigt over Danmarks undergrund og hvornår den blev dannet. View of Denmarks underground and when it was made
Søpindsvin
Der findes i dag omkring 800 arter af søpindsvin hvoraf kun 8-9 forskellige lever i Danmark. Søpindsvinet er et lille kugleformet dyr med en ydre skal af mindre kalkplader der går fra top til bund. Uden på pladerne findes et tyndt hudlag der er beklædt med pigge af varierende størrelse.
Der er to hovedgrupper af søpindsvin: de regulære og de irregulære. De regulære består af 5 helt ens stykker. Gattet sidder midt på ryggen og munden midt på undersiden. Irregulære søpindsvin har derimod gat og mund placeret lidt forskudt på hhv. ryg og underside. De regulære søpindsvin lever på hård havbund som f.eks. koralrev. De irregulære, som er den type man kan se forsteninger af i Dalbyover, lever på og under blød havbund. Alle de forhistoriske søpindsvind var af typen irregulær og kunne have op til 20 pladerækker. De ældste søpindsvin man har kendskab til levede for 480 millioner år siden i Sen Ordovicium.
English:Sea urchins:
There is about 800 different species of sea urchins from which only about 8-9 live in Denmark. The sea urchin is a little round animal covered with an outer shell of minor chalk plates reaching from top to bottom. On the outer side it is covered with a thin layer of skin with spikes of different sizes. Sea urchins are divided into two main groups: regular and irregular. The regular consist of five totally identically pieces. The cloaca is placed right in the middle of the back and the mouth in the middle of the downside. The irregular sea urchins have their cloaca and miuth placed a little staggered. The regular sea urchins live on hard seabed like coral reefs. The irregular sea urchins, like the one you will find fossils of in Dalbyover, lives on and under soft seabed. All the prehistoric sea urchins were of the irregular type and could have up till 20 rows of plates. The oldest known example of a sea urchin lived 480 million years ago in Late Ordovician.
Fossiler
Forsteninger eller fossiler, som det også kaldes, er aftryk af levende organismer, som levede i det forhistoriske hav. De findes ofte i gammel havbund, der i dag ses i skrænter og klinter efter at være blevet presset op af jordens forskydning. Da forsteningen sker langsomt, vil dyrets bløddele være rådnet væk, og det er kun skeletrester og tænder, der bliver tilbage som en forstening.
I Dalbyover kalkgrav findes flest forsteninger af søpindsvin af arten Echinochurus Sulcatus, men der kan også findes forstenede muslingeskaller, fossile gravegange og søliljestilke
English:Fossils:
Fossils are imprints of organisms that lived in the prehistoric sea. They are often found in old seabed today seen on slopes and cliffs where it had been pressed up due to soil shear. As the petrification happens very slowly the soft tissues of the animal has rotted away. Therefore it is only the skeleton and teeth which will petrify. In Dalbyover most fossils are from sea urchin from the species Echinochurus Sulcatus, but you will also find petrified shells, stalk of sea lilies and petrified burrows.
Bonusinfo: Man troede i gamle dage at forsteninger var mislykkede forsøg fra Gud under skabelsesprocessen og at han i vrede havde kastet det ubrugelige produkt fra sig!
Man havde også en teori om at forstenede søpindsvin var opstået under tordenvejr hvorfor fossilerne også kaldtes ”tordensten”
Søpindsvin har et meget kompliceret tand- og kæbeapparat der kaldes noget så besynderligt som ”Aristoteles lygte”! Aristoteles var en Græsk filosof der levede 384 til 322 Før Kr. fødsel.
Englsih:Bonus info:
In ancient times people believed that fossils were mistakes made by God when he created the world and that he had thrown the useless products away in anger.
There was another theory about petrified sea urchins. People believed they were created during thunder storms and therefore they were called: thunder stones.
Sea urchins have a very complicated teeth- and jaw apparatura with the highly peculiar name: Aristoteles lantern named after the Greek philosopher who lived 384 to 322 BC.