Ġeoloġija ta' Malta:
Malta hija arċipelagu li tinkludi l-gżejjer ta' Għawdex, Malta, u Kemmuna. Dawn l-gżejjer huma b'kumplament ikkompożi minn limestone. Miljuni ta' snin ilu, din il-lokazzjoni fil-Baħar Mediterran kienet wasla ta' bażin għall-akkumulazzjoni ta' resti tal-ħajja marina bħal ħamri, mudell, u organiżmi tal-karbonat tal-kalċju. Dawn l-organiżmi jinkludu koralli, qoxra, u ċkejken. Fil-GZ, tkun taħsb li qrib il-bieb ta' Belt Valletta, il-belt tuża l-limestone biex tibni strade u trawwim. Dan il-limestone twaqqaf minħabba l-isforzi ta' ċmentazzjoni u kumpakazzjoni li seħħew miljuni ta' snin ilu. Għoli fil-karbonat tal-kalċju, dan il-ġebla hi post komuni għall-fossilitajiet. It-tip ta' limestone preżenti hawn qrib il-bieb ta' Valletta huwa meqjus Bieżel Limestone Inferjuri. Bieżel Limestone Inferjuri tikkonsisti minn xi mill-ġebla l-aktar antika fuq l-arċipelagu, twaqqfet madwar 30 miljun sena ilu mill-akkumulazzjoni tar-resti tal-koralli u l-ħajja marina. Dan it-tip ta' ġebla huwa għoli sew u poruż. Jiġbed gradazzjoni ta' kolor bejn iswed u beż minħabba l-kalkit u d-dolomit.
Sikkuletti tal-ħmir: Fossilitati fil-Limestone
Il-fossil aktar komuni tal-Bieżel Limestone Inferjuri huwa s-Skutella subrotunda, organiżmu estint estremament simili lill-sikkulett tal-ħmir tal-lum. Dan il-fossil jidher piż fuq forma ta' diskett fl-istrateġija. Il-Bieżel Limestone Inferjuri probabbilment twaqqaf minħabba l-proċess oċeaniku ta' shoaling jew l-akkumulazzjoni ta' sediment fi ħdan il-baħar żgħir minħabba l-azzjoni tal-valur. Is-Skutella subrotunda, organiżmu bientiku li ħafna drabi twaqqaf fuq ir-riħ tal-ħmir u ż-żona tal-valur, ħareġ bħala fossilita meta twaqqaf il-limestone.
L-immaginarju sopra huwa diagramma ta' Scutella subrotunda. Viżw tal-qiegħ u viżw ta' naħa, msemmija bl-ittri A u B, ta' dan l-organiżmu huma ppreżentati.
Dan huwa ritratt ta' eżempju ta' fossilitajiet ta' Scutella subrotunda (sikkuletti tal-ħmir) li ġew misjuba f'saħħa ta' limestone.
Biex tirreġistra s-sejba tiegħek ta’ dan l-EarthCache, jekk jogħġbok lesti l-kompiti ta’ reġistrazzjoni li ġejjin u ibgħatli t-tweġibiet tiegħek permezz tal-Message Center. L-għan huwa li tosserva u titgħallem mill-ġeoloġija ta’ madwarek, għalhekk ħu gost tesplora u wieġeb kull mistoqsija bl-aħjar mod li tista’! Tista’ tirreġistra l-EarthCache immedjatament wara li tibgħat it-tweġibiet tiegħek; m’hemmx għalfejn tistenna tweġiba mingħandi. Jekk ikolli xi tħassib jew mistoqsijiet dwar it-tweġibiet tiegħek, nikkuntattjak.
Mistoqsijiet:
- X'inhu l-aħjar għoli u wisa medja ta' l-fossilitajiet tal-iskudu tal-ħmir (Scutella subrotunda)?
- Tista' tara l-fossilitajiet mill-viżw tal-qiegħ jew mill-viżw ta' naħa? Jidher li l-iskudu tal-ħmir huma kollha intatti jew spezzati?
- Tifhem xi tnaqqis fil-kulur/ħolqien meta tikkonfronta l-fossilitajiet ma' l-ġebla ġenitur tal-limestone? Għaliex tħoss li dan isir?
- Dan huwa taħdit meħtieġ. Jekk jogħġbok għażżel ritratt tiegħek, tal-GPS tiegħek, jew oġġett personali li jidher li żżurta din il-post. Jekk jogħġbok poġġih f'post n-nota tiegħek.
Sorċijiet:
https://earthobservatory.nasa.gov/images/150742/maltas-landscape-of-limestone
https://www.ucl.ac.uk/~ucfbrxs/Homepage/walks/MaltaMemorial.pdf
Geology of Malta:
Malta is an archipelago comprising the islands of Gozo, Malta, and Comino. These islands are predominantly formed of limestone. Millions of years ago, this location in the Mediterranean Sea was a basin for accumulating marine debris such as sand, silt, and calcium carbonate organisms. These organisms include corals, shells, and echinoderms. At the GZ, you will notice that near the entrance to Valletta, the city uses limestone to construct roads and pathways. This limestone was created due to the same forces of cementation and compaction that occurred millions of years ago. High in calcium carbonate, this rock is a common site for fossils. The type of limestone present here near the gates of Valletta is considered Lower Coralline Limestone. Lower Coralline Limestone consists of some of the oldest rocks on the archipelago, formed around 30 million years ago from the build-up of coral remains and marine debris. This type of rock is extremely coarse-grained and porous. It ranges from gray to beige due to calcite and dolomite.
Sand Dollars: Fossilized in Limestone
The most common fossil of Lower Coralline Limestone is Scutella subrotunda, an extinct organism extremely similar to the modern-day sand dollar. This fossil appears rather flat and disk-shaped. Lower Coralline Limestone was likely formed due to the oceanic process of shoaling or the accumulation of sediment in shallow water due to wave action. Scutella subrotunda, a benthic creature that commonly inhabited sand bars and shoals, became fossilized when limestone formed.
The above image is a diagram of Scutella subrotunda. A top view and a side view, denoted by the letters A and B, of this organism are provided.
This is a photo of an example of Scutella subrotunda (sand dollar) fossils found in a specimen of limestone.
To claim your find for this EarthCache, please complete the following logging tasks and send your answers to me through Message Center. The goal is to observe and learn from the geology around you, so have fun exploring and answer each question to the best of your ability! You may log the EarthCache immediately after sending your answers; there’s no need to wait for a response from me. If I have any concerns or questions about your answers, I’ll reach out to you.
Logging Tasks:
- What is the average length and width of the sand dollar (Scutella subrotunda) fossils?
- Are you observing the fossils from the top or side views? Do the sand dollars appear fully intact or broken?
- Is there a difference in color/appearance when you compare the fossils to the limestone parent rock? Why do you think this occurs?
- This is a required photo task. Please provide a photo of yourself, your GPS, or a personal item that proves that you have visited this site. Please post this in your note.
Sources:
https://earthobservatory.nasa.gov/images/150742/maltas-landscape-of-limestone
https://www.ucl.ac.uk/~ucfbrxs/Homepage/walks/MaltaMemorial.pdf
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