Florida Keys Field Trip Day 2

On Saturday, September 21st, we begun our trip early in the morning around 8:30am heading to Windley Key Coral Reef State Park. This park was formed out of Key Largo Limestone, fossilized coral and was used to built Henry Flagler's Overseas Railroad in the early 1900s. (for more information click here)

Picture 2.1:Windley Key Coral Reef State Park

Picture 2.2: Windley Key Coral Reef State Park

The purpose of our visit to this park was to examine the exposed sections of fossilized coral. We got to see what an ancient coral reef looks like from the inside (Picture 2.5-2.6). It is important to mention that 125,000 years ago, the exposed dry land of the Florida Keys was underwater. Due to the formation of advanced continental glaciers 18,000 years ago, the sea reached its lowest point and has been rising since then to the present levels.

Picture 2.3: Key Largo Limestone 40x

In pictures 2.3 & 2.4, you can see the thin section of the Key Largo Limestone. Unfortunately, I had to use thin sections from other classmates, because the samples i used to make thin sections broke due to extensive polishing and pressure. In the 1st and 2nd picture there is a 40x zoom with the microscope.

Picture 2.4: Key Largo Limestone plain light 40x

In the Key Largo Limestone you can find fossilized shells, coral and other marine calcium carbonated material. It is also highly porous and permeable and is exposed at the surface in the Florida Keys from Soldier Key on the northeast to Newfound Harbor Keys near Big Pine Keon in the southwest. ( for more information click here)

Picture 2.5: Exposed Sections

Picture 2.6: Taking Notes

The most common fossils i found on the exposed section were brain coral (Picture 2.7). The name comes from the spheroid shape and grooved surface which looks like a brain. Each of those brain looking corals are made from the same organisms that polyps are made from, which produce a hard skeleton of calcium carbonate. Moreover, this type of coral is responsible for building major reefs throughout the world’s tropical oceans. ( for more information click here)

This Becomes This
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Picture 2.8: Fossilized Brain Coral

Picture 2.7: Brain Coral

Picture 2.9: Fossilized Coral

The name "coral" comes from a group of cnidarians with calcareous skeletons that are usually attached to a hard surface on the sea floor. Coral skeletons are calcareous, but may be either calcite or aragonite (two of the mineral forms of CaCO3). Most of the Paleozoic corals produce calcite skeletons but the Mesozoic- Cenozoic skeletons are mainly aragonite.

Picture 2.10: Closer Look

Corals are major components of many living and fossil reefs ranging in age from Ordovician to the present. Two body forms, polyp and medusa, occur as alternating stages in the life cycles of many cnidarians. In the Picture 2.8, we see a polyp, which, before fossilizing, it used to live on the bottom of the sea, temporarily or permanently attached with the mouth and tentacles on their upper side. ( for more information click here)

After a nice lunch at a local restaurant on the Big Pine Key island, we continued our trip to a main attraction of that island called Blue Hole which is a large sinkhole in the limestone but also an abandoned rock quarry . It is important to mention that Blue Hole is the only freshwater lake in the Florida Keys. This lake houses a variety of wildlife such as alligators, birds, snakes, iguanas, Key deer etc. I have to say that even though the place is called Blue Hole, in reality it was a greenish to black color lake with different plants, branches and leaves all over the area and in the water (Picture 2.11). The limestone in that area is called Miami Limestone and it is a Pleistocene marine limestone.This limestone is composed of two facies; Oolitic and Bryozoan. The Oolitic facies consist of well-sorted oolites/ooids and skeletal material such as corals, echinoids, mollusks, algae and some quartz sand. The bryozoan facies is composed mainly of white to orangish gray, sandy, fossiliferous limestone while beds of quartz sand and limey sandstones may also be present. The rainfall that causes dissolution of the calcium carbonate in the rock forms a Karst surface ( for more information click here)

Picture 2.11: "Blue" Hole

Picture 2.12: Thin Section- Miami Limestone

The Miami limestone in this thin section comes from the samples we collected. As you can see, the grains are sorted and rounded which are composed of two facies as mentioned above; the Oolitic and Bryozoan. Also, you can see some skeletal material as well as white to orangish grey grains that come from the Bryozoan facies.

Because we were ahead of schedule, we decided to stop at a limestone area, which was on our way to the Veterans Beach. At the place there, i noticed that it had a lot of garbages which were mostly plastic bags. Also, after peeling off the edge of the limestone, i managed to find a coral that was attached in the rock and probably in the fossilization process.

Picture 2.13: Lime Mud Stop

Picture 2.14: Calcium Carbonate

The time we have all been waiting for, where we could actually be a part of, swim and check out from a closer distance all of these exciting corals, algae and other carbonated organisms was next in our trip; Snorkeling time!

Picture 2.16: Me at Veteran's Beach

Picture 2.15: Veteran's Beach

Picture 2.17: Veteran's Beach

Picture 2.18: Veteran's Beach

My experience at Veteran's beach wasn't that exciting due to the fact that i got stung by many "upside down jellyfishes" (picture 2.19). Fortunately, i managed to find what i was looking for, a "Penicillus algae"(Picture 2.20) and "Halimeda algae"(Picture 2.21), these two particular algae were everywhere in the sea, but unfortunately i couldn't find any Udotea algae. Because of these algae, we can enjoy the sand and the beaches of the Keys, since they play an important role in the marine ecosystem. I have to mention that i was really impressed by the clear path that was situated between the marine plants in the beach, you can see that path in the picture 2.18. I am not really sure why that area was clear of marine plants, that extended along the ocean, but based on opinions of my classmates and my own, we came up with two possible explanations; one that it might be a human made path so that people can walk through the water and two that marine life such as crabs, fishes, jellyfishes etc., had somehow cleared that area for easiest pass through the plants.

Picture 2.19: Upside-Down Jellyfish

Picture 2.21: Halimeda Algae

Picture 2.20: Penicillus Algae

The sand samples that I collected from Veterans beach contained some shells and other marine calcium carbonated material that is hard to see with a naked eye. Picture 2.22, which is under the microscope, allows us to clearly see some shells etc., the red circles point out a few of them. Also, the grains are angular and moderately sorted.

Picture 2.22: Veterans Beach Sand Sample

Anne's beach is located at the lower Matecumbe Key and it was named "Anne" because of the local environmentalist Anne Eaton. At Anne's Beach, people can enjoy the shallow warm waters and the placid sea, since there is no wave action. Also, the sandbar there is composed entirely of calcium carbonate (Picture 2.25). Because of the wave absence, the right erosional and depositional conditions, Anne's beach is a perfect place for lime mud accumulation.