– Why does Fan Forrest Pinnacle look completely white?
– And Black Rock, well ..black?
– What is the role Of North- & South Twin Islands with their granite boulder setup in the hole picture?
– Why does the “Limestone” in Mergui look so completely different than the one on Phang-Nga Bay and Koh Bon?
I’ve been told, that this is all limestone, but i have no proof of it – and i was repeating this myself to many people now without questioning. Beginning of April i was on an extended Trip to the Mergui Archipelago and used the opportunity to tackle this question a bit. My answer towards it is at the moment: There’s Limestone, but the complete reality is much more complex. And i ask myself how the answer to this geological question could supply answers to questions about marine life like coral growth. If you look at Western Rocky with its kind of “complete” setup of corals (soft corals, sponges, hardcorals, staghorn corals, etc) – and compare it to Fan Forrest Pinnacle with its weird looking almost white surface and nearly nothing else but Gorgonian Seafans growing on it – and then taking into account that both divesites are only about 6 nautical miles away from each other – I state that there are very interesting question neither asked nor answered yet.
I gathered evidence that Burma’s Mergui Archipelago is made of several complex rock compositions, which i will present here. I am not a geologist, i rather need a couple of them now to help me out! I do not ask the question “how did it develop?” – this is some full on geology stuff, what i am asking is
– What composition is the Mergui Archipelago made of?
– How does the composition change within short distances?
– How do different stone compositions affect coral growth?
Indications for Different Rock Compositions
Beginning of April i started to have a closer look on things above water and here’s what i found:
Normally we only get to see the rocks from not closer than 50m as we’re on a diveboat getting dropped near to the islands and rocks. Life underwater changes the surface of rocks dramatically, so i would have to bring heavy tools to examine the original rock structure from there. So I went on Ba Wei Island next to Stewarts Rock to take a very close look on the rocks and stones there. The first time i was standing in front of the most common rock formation untouched by seawater unveiled several interesting things.
IThere are veins of another material running in a kind of a grid pattern throughout the entire main rocks. These veins are dark red, which indicates high abundance of iron (just guessing) and they seem to be easily solved by rain water that washes them of and leaves those impressive block-grid looking rocks we can see throughout the entire Mergui Archipelago. The leftover pattern on the rock surface leave an image that from only few meters away look like limestone formations – but the rock itself has more characteristics of granite and quartz. It looks like rain washed enough of the grid veins out of a bigger body of rock, it then falls to pieces of smaller boulders:
Clearly to see on this picture is that there are numerous materials involved! As i went further to the beach to another pile of boulders in the tidal area it became even more obvious:
So either somebody’s doing a labour intensive job in kidding me, or we’re briefing wrong geological information to our customers. On a short walk around the island, i saw quartz, sandstone, granite and porphyry. I took some overview shots of a wall where it is easy to see, what i am talking about:
Here we see a black area (obviously turned black from rain, what is it?) and then a part underneath where the dark red veins appear again – parts of this main rock already “left” because the “vein”-material already disintegrated there – obviously..
I decided to take some samles of the most common stones i could find in order to let them have analyzed, and found that there isn’t even such a thing as “most common” to find amongst them, clearly to see here – these are the three samples who look most alike each other:
Ok, all i’m doing here is observing and guessing – now science has to take over, first i’d need these three samples analyzed. After that another gathering of samples campaign in a bigger area of the Mergui Archipelago should take place – and to answer the question how these compositions affect underwater life, we would need some Geology-Biologists here – anybody fancy a bit working in the field?
Fotos and samples were taken around Ba Wei Island: