Despite the fact that there are about 5000 living species, with several times that number of fossil species, the Bryozoa (from the Greek Bryon, meaning moss and Zoon, meaning animal) remain largely unknown to most people. The Bryozoans are aquatic organisms that generally build stony skeletons made up o calcium carbonate (CaCO3) and live for the most part in colonies of interconnected individuals that may number in the few millions. They are frequently referred to as “moss animals” and “sea mats” as they appear as bushy, mossy-looking or mat-like, sometimes crusty, colonies of filter-feeding individuals animals. Some bryozoans encrust rocky surfaces, shells, or algae. Others, like the fossil bryozoans, form lacy or fan-like colonies that in some regions may form an abundant component of limestones. Bryozoan colonies range in size from millimeters to meters, but the individuals that make up the colonies are rarely larger than a millimeter.
They are well preserved in the fossil record because of their zooecia and we know they have been around since the Ordovician period (488-443 Ma). There were about 15000 species during the Cretaceous (145-65.5 Ma) period, though they were not all living at the same time. Today there are in the region of 5000 known species most of which live in marine environments, though there are about 50 species which inhabit freshwater.
The Miocene epoch lasted from 23 to 5.3 million years, making it the longest epoch of the Cenozoic era. This was a time of huge transition, the end of the old prehistoric world and the birth of the more recent world. It was also the high point of the age of mammals. It was a time of warmer global climates than those in the preceding Oligocene (33.9-23 Ma), or the following Pliocene (5.3-1.8 Ma). During this time modern patterns of atmospheric and ocean circulation formed. The isolation of Antarctica from Australia and South America meant the establishment of the circum-polar ocean circulation, which significantly reduced the mixing or warmer tropical water and cold polar water, and further led to the buildup of the Antarctic ice cap. Many new mountain ranges were formed during the Miocene. When the African plate pushed against Europe and Asia, the Alps formed. The Rocky Mountains and the Appalachians formed, along with the Himalayas, which where just beginning to form as the subcontinent of India collided into Asia. Australia and South America remained separated from the rest of the world.
This cache is located in one of the eleven geomonuments in the city of Lisbon, and is the only one that has undergone museulogical treatment. Twenty million years ago this area was a shallow see full of reefs and the cache is an outcrop that has remained from that time. The outcrop of limestone is partly made of the compressed skeletons of millions of bryozoans.
Your tasks, in order to claim this earthcache are to:
1- measure the length of the outcrop and,
2- tell me how many species of bryozoans are found in this outcrop.
E-mail the results of thse two questions to me and I will reply with permission or not to log your “found”.
A jazida corresponde a uma bancada lenticular de calcário argiloso muito fossilífero, rica em briozoários, sobreposta a uma camada argilosa explorada, no passado, como barreiro da antiga Cerâmica Lisbonense. Descrita inicialmente por Berkeley-Cotter (1956, publicação póstuma) como "Molasso e argilas de Venus ribeiroi dos Prazeres", e atribuída aos níveis mais baixos do Burdigaliano, foi, mais tarde, atribuída ao Aquitaniano superior, isto é, a um nível estratigráfico ligeiramente mais antigo (24 a 22 milhões de anos).
As concreções calcárias que nela se destacam são restos de briozoários dispostos em capas muito finas e concêntricas que, em vida, representavam colónias que se iam desenvolvendo, sobrepondo-se umas às outras. Tais concreções, uma vez sujeitas à agitação marinha, movimentavam-se por rolamento no fundo, num vaivém de remobilização e redeposição, à semelhança dos calhaus e areias litorais, e daí o carácter de estratificação entrecruzada patente no afloramento.
Esta earthcache encontra-se no único geomonumento com tratamento museológico na cidade de Lisboa. Existem 11 destes geomonumentos na lista oficial do estudo do Museu de História Natural aceite pela CML), embora um deles esteja destruído (Travessa das Águas Livres - Terraço flurio-marinho do Cenozóico Inferior. 30 milhões de anos).
A vossa missão é medirem o comprimento deste afloramento e descobrirem quantas especíes aqui se encontram (indicado nos paineis informativos). Respondam às seguintes perguntas:
1- Qual é o comprimento do afloramento (em metros)?
2- Quantas espécies de briozoários se encontram na jazida?
Enviem-me as vossas respostas por mail que depois valido, ou não, o vosso found.