Lumachella is the common name of an organogenic sedimentary rock characterized by an abundant and clearly visible presence of fossil shells. The same term is also used in the descriptive geological field to indicate a rock composed almost exclusively of shells of fossil shells, even if unsuitable for use for ornamental purposes.
These rocks demarcate a mass extinction event in the geological record.
Lumachela originate from bioclastic sedimentation that are formed through the accumulation of organic remains of animals characterized by the presence of a shell or a rigid mineralized skeletal structure of the type: lamellibranches, gastropods, brachiopods, ammonites, echinids and nummulites, but also of corals and plant organisms such as some calcareous algae. Then comes the diagenesis, a transformation process that hardens the original sediments, which often includes, in these lithologies, an abundant deposition of crystalline calcitic cement, called sparite, in the original porosities of the sediment and the internal cavities of the organic remains not filled by the sediments during deposition and burial.
Normally the formation environment is found in sea depths of modest depth, within the photic zone where remarkable colonies of molluscs can be found.
Frequent mollusc accumulations in Europe have occurred in the lower Mesozoic and Cenozoic.
At the location of the coordinates, you will be able to identify this rock by its dark colour and composed of thousands of black, shiny, flattened shells - see spoiler (note: photo taken elsewhere – you cannot answer question 2 with it).
To validate the EC, answer the following questions on the spot, send the answers through my profile, and log. If anything is wrong, I will get in touch. Photos are welcome but do not place spoiler photos.
Note: Steep footpath! Irregular! Do not go there when it is wet! Wear proper shoes. Take water with you. Take the camera!
- What is the thickness of the lumachela layer?
- What is the average length of the shells?
Lumachela, do italiano lumachella, é o nome de uma rocha sedimentar organogénica, composta pela aglomeração de grande número de conchas ou carapaças fósseis de organismos marinhos.
Estas rochas retratam uma mortandade em massa!
No local das coordenadas, vais poder identificar esta rocha pela sua cor escura e composta por milhares de conchas pretas, brilhantes, achatadas – ver spoiler (nota: foto tirada noutro local. Não serve para responder à pergunta nº 2).
Para validar a EC, responde às seguintes perguntas no local, envia as respostas pelo meu perfil, e faz o registo. Caso tenhas algo errado, entro em contacto. As fotos são bem vindas mas não coloques fotos spoiler.
Nota: Trilho íngreme! Irregular! Não fazer com o substrato molhado! Usem sapatos adequados. Levem água. Levem máquina fotográfica!
- Qual a espessura da camada de lumachela?
- Qual o comprimento médio das conchas?
Obrigado pela visita. Aprecia as vistas, o mar mas sobretudo a geologia.
The most exciting way to learn about the Earth and its processes is to get into the outdoors and experience it first-hand. Visiting an Earthcache is a great outdoor activity the whole family can enjoy. An Earthcache is a special place that people can visit to learn about a unique geoscience feature or aspect of our Earth. Earthcaches include a set of educational notes and the details about where to find the location (latitude and longitude). Visitors to Earthcaches can see how our planet has been shaped by geological processes, how we manage the resources and how scientists gather evidence to learn about the Earth. To find out more click HERE.