From the guidelines, as from January 2013: "People do not need to wait for permission to log your EarthCache. Requiring someone to wait is not supported by the EarthCache guidelines. People should send their logging task answers to you, then log your EarthCache. When you review their logging task answers, if there is a problem, you should contact them to resolve it. If there is no problem, then their log simply stands."
In geology a bed is the smallest division of a geologic formation or stratigraphic rock series marked by well-defined divisional planes (bedding planes) separating it from layers above and below. A bed is the smallest lithostratigraphic unit, usually ranging in thickness from a centimeter to several meters and distinguishable from beds above and below it. Beds can be differentiated in various ways, including rock or mineral type and particle size. The term is generally applied to sedimentary strata, but may also be used for volcanic flows or ash layers.
Beds are made up of a single rock unit and may be subhorizontal or at a greater angle or even folded.
“Beds” are the base members upon which stratigraphy is based:
· Supergroup - two or more groups and lone formations - The term "supergroup" may be used for several associated groups or for associated groups and formations with significant lithologic properties in common.
· Group - two or more formations - A succession of two or more contiguous or associated formations with significant and diagnostic lithologic properties in common. Formations need not be aggregated into groups unless doing so provides a useful means of simplifying stratigraphic classification in certain regions or certain intervals. Thickness of a stratigraphic succession is not a valid reason for defining a unit as a group rather than a formation. The component formations of a group need not be everywhere the same.
· Subgroup - Exceptionally, a group may be divided into subgroups.
· Formation - primary unit of lithostratigraphy - Formations are the primary formal unit of lithostratigraphic classification. Formations are the only formal lithostratigraphic units into which the stratigraphic column everywhere should be divided completely on the basis of lithology. The contrast in lithology between formations required to justify their establishment varies with the complexity of the geology of a region and the detail needed for geologic mapping and to work out its geologic history. No formation is considered justifiable and useful that cannot be delineated at the scale of geologic mapping practiced in the region. There is no formal limit to how thick or thin a formation may be.
· Member - named lithologic subdivision of a formation - It possesses lithologic properties distinguishing it from adjacent parts of the formation; No fixed standard is required for the extent and thickness of a member; A formation need not be divided into members unless a useful purpose is thus served; Formations may have only certain parts designated as members; A member may extend from one formation to another.
· Bed - named distinctive layer in a member or formation - The smallest formal unit in the hierarchy of sedimentary lithostratigraphic units, e.g. a single stratum lithologically distinguishable from other layers above and below. Customarily only distinctive beds particularly useful for stratigraphic purposes are given proper names and considered formal lithostratigraphic units.
Note that stratigraphy can also be defined using chemostratigraphic (stratigraphy with the same or similar geochemical composition) or biostratigraphic (biostratigraphic units are defined by the presence of biological markers, usually fossils) criteria.
Geologic setting
The coastline west of Lisbon is made up of limestones of Cretaceous age (145 to 65 M.a.) that outcrop freely and abundantly throughout the area and are punctuated with occasional remnants of the Lisbon Volcanic Complex (CVL in the geological maps).
They are typically mostly marly limestones with a fair amount of carbonaceous material and are clearly seen on the beaches lining the western Lisbon coastline.
The cache
This cache takes you to a small beach (Praia da Torre) in Oeiras, a satellite city of Lisbon, approximately 12 km west of central Lisbon, where a marly limestone bed, orange in colour can be easily observed. This bed is “sandwiched” between lighter coloured limestones and can be easily identified. In order to log your find, your task is to measure the thickness of this bed at the location indicated by the coordinates above and send me that measurement by mail to validate the find. Note that viewing is best from the beach (there is a narrow path down) and if you cannot see the bed in question once on the beach look east and slightly upwards!
A cache leva-te à Praia da Torre (S. Julião, Oeiras) onde afloram nas pequenas arribas calcários margosos de cor creme e ainda uma camada de calcário mais alaranjado. Para poderes contabilizar mais este "found" tens de descer à Praia da Torre e nas coordenadas, virado para este, medir a espessura dessa camada mais laranja. Envia-me a resposta via mail. Se estiveres correcto tens mais um found.
Sources: adapted from Here and here
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.
