The coordinates you see here bring you to the Masjid Jamek Pedestrian Bridge that goes over the river of life. Looking at the bridge you will see a very interesting feature within the stones.

Sedimentary Rocks

The rock you see here is a sedimentary rock. Sedimentary rock is formed as layers of sediment pile up and are eventually cemented together.

Formation of sedimentary rocks (eschooltoday.com)

The bridge here is made from travertine, which is a type of sedimentary rock. Travertine is a type of limestone as well, if you take a look at the bridge you will see a brown patch of calcite, which is a form of calcium carbonate.

Fossils

One very interesting feature found in sedimentary rocks are the presence of fossils. A fossil is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved in amber, hair, petrified wood, oil, coal, and DNA remnants.

Image depicting the formation of a fossil. Notice how it is formed within a sedimentary rock. (Source: Goldies Room)

There are 6 ways that fossils can be formed:

• Unaltered preservation (like insects or plant parts trapped in amber, a hardened form of tree sap)
• Permineralization (in which rock-like minerals seep in slowly and replace the original organic tissues with silica, calcite or pyrite, forming a rock-like fossil - can preserve hard and soft parts - most bone and wood fossils are permineralized)
• Replacement (An organism's hard parts dissolve and are replaced by other minerals, like calcite, silica, pyrite, or iron)
• Carbonization (in which only the carbon remains in the specimen - other elements, like hydrogen, oxygen, and nitrogen are removed)
• Recrystalization (hard parts either revert to more stable minerals or small crystals turn into larger crystals)
• Authigenic preservation (a process which leaves a negative impression, or indent, of an organism in rock after the organism itself has deteriorated).

There are 4 types of fossils:

• Mold fossils (a fossilized impression made in the substrate - a negative image of the organism)
• Cast fossils (formed when a mold is filled in)
• Trace fossils/Ichnofossils (fossilized nests, gastroliths, burrows, footprints, etc.)
• True form fossils (fossils of the actual animal or animal part).

Logging Tasks

Send the answers to the following questions via my profile and log immediately. I will get back to you if there are any unsatisfactory answers.

1. The little holes you see here are the fossils in question. Describe the shape of the fossils you see here and give an estimate of the average size.
2. What is the method of fossilisation here?
3. What is the type of fossil?