This EarthCache will take you to Seymour Island, where there are very interesting Tertiary sediments, which are abundant in fossils.
I had the honor to visit this place in February 2021 during geological research.
Geology
Seymour Island is located on the Antarctic Peninsula. This and other islands around it were influenced by the Mesozoic, and to a lesser extent the Tertiary. Most fossils come from the Mesozoic, they are mostly ammonites. The whole island is made of sediments (most often sandstones).
In December 1892 when Norwegian Captain, Carl Anton Larsen landed his ship, the Jason, on Seymour Island, he returned with more than maps of the territory, he found fossils of long-extinct species. Larsen's trip aboard the Jason was significantly more successful than his Swedish Antarctic Expedition journey between 1901 and 1904. During that trip, his ship, the Antarctic, was crushed and sunk by icebergs, and he and his crew were forced to weather fourteen months on the neighboring Snow Hill Island, surviving on penguins and seals. Ever since his voyage on the Jason, the island has been the subject of paleontological study.
Sandstone
Sandstone is a solid, clastic sedimentary rock. In simple terms, a rock can be described as sandstone if a substantial part consists of grains with a size of 0.06 to 2 mm. Quartz sandstones are very common, where a substantial part of the grains consists of quartz. Sandstone is formed by cementing grains (technically speaking, so-called clasts - usually quartz, feldspars and rock fragments such as silicites) with putty. This sealant is very often carbonate or ferrous. The interstitial mass (eg clayey) is called a matrix. The composition of sandstone varies according to the place of occurrence. Sandstone has very different colors: from gray through yellow to red (indicates the presence of iron oxides), sometimes it can be multicolored.
According to the size of the grains, sandstone is divided into several grain sizes:
Below are some elements and the colors they often produce in minerals:
Cobalt: Violet-Red
Chromium: Orange-Red
Copper: Blue
Iron: Red-Brown
Manganese: Pink-Purple
Nickel: Green
Uranium: Yellow
Fossils
Fossils are the remains of prehistoric organisms that have survived to this day. The fossil can be either stone (fossil fossil) or bones of dinosaurs, or fossilized tribes of ancient trees. Any fossil, whether whole or incomplete, of animal or plant origin older than 10,000 years (Pleistocene and earlier) is considered to be fossil. However, the remnant must give us at least a basic idea of the shape and construction of the prehistoric organism. Fossils are material evidence of the existence of life that was in the geological past on our planet.
Fossils are the remains of organisms from the geological past that have survived to the present. In order for such a thing to happen at all, certain conditions and processes must exist that will allow and cause the formation of fossils and thus the retention of the remains of dead organisms.
Fossils are created in different places where there are conditions for their preservation. The very process of fossil origin can also have different forms, but the goal is to save the rest or residue of the organism before it is disintegrated or destroyed.
Although it may seem that fossil is a huge amount (especially in some localities), the fossil origin is rather exceptional. Most remains of living organisms have only a very small chance of being falsified - rather, they will be irretrievably destroyed.
The conditions for the creation of fossils are really very demanding, and so the fossils show us only part of the life in prehistory. Where there were no suitable conditions for the creation of fossils, the information is simply missing us. When working with fossils, we must always keep in mind that we only work with a selection and not a complete source of information. However, even with this consciousness, paleontology can be seriously exploited and exploited in practice.
Amonite
There are many symbols in geology and one of them is ammonite. Ammonite occurred in the Mesozoic in the sea. It is a collective term for a large group of cephalopods with a characteristically twisted shell made of calcium-containing minerals. This already extinct group of organisms is a direct ancestor of today's octopuses, for example. The Ammonites actually looked like that, if you took the box off. Ammonite shells could reach up to meters in size, and in connection with their great ferocity, they were perfect water killers. The largest specimen found so far is 2.3 meters.
The scheme of ammonite formation is well shown in the following figure:
Thanks to Gredrre for help me with listing.
Edit: Given that it is "the most representative site of the K-Pg boundary at high latitudes and one of the most important and best exposed globally", the International Union of Geological Sciences (IUGS) has included the "Cretaceous-Paleogene transition on Seymour Island (Marambio)" in its list of 100 "geological heritage sites" worldwide in a list to be published in October 2022 (for the record, other sites on this list include Mount Everest, the Grand Canyon and the Yellowstone Caldera). The site is therefore one of the most important geological sites in the world
Tasks:
1. Describe how fossils are formed.
2. From the color of the sandstone, determine what elements it abundantly contains.
3. What is the structure of sandstone? Estimate its grain size.
4. Observe the ammonites on this island, did they form rather silicifation or pyritization? Why?
5. Take picture with you or with your GPS near GZ or anywhere on the Seymour Island.
(You don't have to go to GZ to log into this Earthcache, you can answer questions from other parts of Seymour Island. Remember, you must visit this place - all fake logs will be deleted!)
Send me answers via profile. I will contact you if I need.
Resources:
1. Wikipedia Seymour Island
2. Wikipedia Ammonoidea
3. Wikipedia Sandstone
4. https://dxnews.com/lu4zs_marambio-station_seymour-island_antarctica/
5. https://www.compoundchem.com/2017/11/29/ammonites/