You find yourself at the entrance to the Dubh Linn Gardens, part of the Dublin Castle complex.
In the center of the garden, now a green space (helicopter pad actually) - is the area where the Rivers Poddle and Liffey met (now underground) - forming a black pool or as Gaeilge: Dubh Linn - and it's after this black pool that lovely Dublin is named.
Before going for a lovely walk & spending time enjoying the gardens, please examine the frame of the entrance into the gardens, and indeed the same rock is found inside too, and find the answers to enable you to log this EarchCache,
Sedimentary Rock
Sedimentary rocks are types of rock that are formed by the deposition and subsequent cementation of that material at the Earth's surface and within bodies of water. Sedimentation is the collective name for processes that cause mineral and/or organic particles (detritus) to settle in place.
Limestone
Limestone is a sedimentary rock composed primarily of calcium carbonate in the form of the mineral calcite. It most commonly forms in clear, warm, shallow marine waters. It is usually an organic sedimentary rock that forms from the accumulation of shell, coral, algal and fecal debris. Pure limestones are white or almost white. Because of impurities, such as clay, sand, organic remains, iron oxide and other materials, many limestones exhibit different colors, especially on weathered surfaces. Limestone may be crystalline, clastic, granular, or dense, depending on the method of formation. Crystals of calcite, quartz, dolomite or barite may line small cavities in the rock.
Carboniferous Limestone
Carboniferous Limestone is a collective term for the succession of limestones occurring widely throughout Great Britain and Ireland that were deposited during the Dinantian Epoch of the Carboniferous Period.
The rock is made up of the shells and hard parts of millions of sea creatures, some up to 30 cm in length, encased in carbonate mud. Fossil corals, brachiopods and Crinoidea are very much in evidence as components of Carboniferous Limestone; indeed the rock is full of fossils.
To log This Earthcache
Please contact me through my profile with the answers to the following questions.
Please send the answers before logging your find, you don't have to wait for a reply to log it, if there is a problem I will contact you.
1. Take a look at the frame of the entrance to the gardens, and describe the type of fossil that is the most prevalent here. Colour, shape, size.
2. Do you think these fossils are mostly coral or brachiopods?
3. How old do you think the rocks from which these slabs were formed are?
4. Can you see any other types of fossils here apart from the one you have described?
5. Post a photo with your online "Found it" log, of yourself in the gateway/entrance - If you're shy there's no need to show your face - an original pic of the gateway with a thumbs up, caching name or gps etc is acceptable too.
6. This is a very popular cache - I'm afraid I do not have time to keep messaging people for the correct phot - so if you don't have the photo as per above your log will be deleted, with no warning - please feel free to re-log with the correct one.
Answers without the requisite photo - IN THE GATEWAY - and /or answers sent are liable to be deleted without comment.
Please note there is a set of 5 Adventure caches and Dublin Castle & City Hall Adventure (Lab) Bonus cache in the area too - all within a very short stroll of where you stand, two Adventures are in the Gardens.
To play the lab caches download the Adventure Lab app to your phone then Use your phone's native QR code scanner to open this adventure in the Adventure Lab mobile app, or share the following URL:
https://labs.geocaching.com/goto/DublinCastleCityHall
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