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ビー
チからボートに乗り,一路カルストキャッスルという地点へ.途中オルドビス紀の分厚い層状石灰岩がきれいに見える.ある場所ではゆっくりと背斜は向斜を
作ったり,別の場所では層理が見えない塊状であったりと興味が尽きない.日本のオリストリスのブロック状の分布が狭い石灰岩とは,様子が異なると久田先生
と議論した.持参したGoProの迫力ある動画はクリックしてください.
From the beach, we took a boat to a point called Karst Castle. On the way to the karst castle, thick stratified limestone of Ordovician age is beautifully visible. In
some places, the formations are slowly forming anticlines, and in other
places, the limestone is massive with no visible layers, which is very
interesting. I discussed with Prof. Hisada that this is different from the blocky, narrowly distributed limestone of the Japanese Oristolith.
Click the image for a spectacular video by GoPro I brought.
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さて各観察地点へは,ごらんのカヌーで渡してくれます.水深は浅いのですがこのときも落ちないように注意.
The canoe will take you to each observation point. The water is shallow, but be careful not to fall in.
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さて上陸地点は海が凪いでいて,かつ干潮のときしか降りれない様子.我々はいずれも条件もクリアして降りれた.ここで足元の石灰岩をチェック.
The landing site can only be reached when the sea is calm and the tide is low. We were able to go down after meeting all of these conditions. Here, we checked the limestone rock under our feet.
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そうするとF氏が早速三葉虫を発見.今回唯一の明らかにわかる三葉虫でした.オルドビス紀の三葉虫となります.しかし腹側の印象のためか,複眼は見つけれませんでした.
Mr. F immediately found a trilobite. It was the only clearly recognizable trilobite this time. It is a trilobite of Ordovician age. However, we could not find the compound eye, probably because of an impression of the ventral side.
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こちらは巻貝.
Here is a snail. |
し
かしここで久田先生が注目したのは,この妙な風化模様です.彼はこれをBioTurviationと考えるとの考え.すなわち海底の未固結の石灰泥に,何
か生物が穴を掘り,それが同質の物資で埋められて残ったものだろうという解釈.実際ODPのボーリングコアで,原生に近い部分では凄まじいこの生物かく乱
が生じているとか.言われてみると一部は巣穴や食べ物を探したあとに見えなくもない.
However, what caught Prof. Hisada's attention here was the strange
weathering pattern. He thinks this is BioTurviation. In other words,
some organism must have dug a hole in the unconsolidated lime mud on the
seafloor, which was then filled with the same material and left behind.
In fact, the ODP borehole cores show tremendous bio-disturbance in the
near-pristine areas. It seems that some of the bio-disturbance may be
burrows or after searching for food. |
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これはスランピングが見えたような気がしたところ.This is where I thought I saw slumping ... |
さて化石島に到着.ここにはトイレとベンチがあって,ここで弁当を食べました.
Now we arrived at Fossil Island. There is a toilet and a bench here, where we ate our lunch.
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しかし案内板は残念ながらタイ語だけだったような.しかし実際船の船頭やスタッフがガイド役を務めて,観光で訪れた客に,タイ語に混じって,きちんとオルドビシアンとか専門用語で説明をしていたのは聞こえた.
Unfortunately, the information board was only in Thai. However,
I could hear staffs of the boat acting as guides, explaining to the
tourists in technical terms such as "Ordovician" mixed with Thai.
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これがこの化石島の化石の観察ポイント.全部で13の化石がこの壁で見られるとかで,説明板があります.
This is the fossil observation point on Fossil Island. There are 13 fossils in total on this wall, according to an explanation board.
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鎖の囲いより中には入れないので,そのうちの近いものについて,水をかけて内部構造が見やすくしたもの.これは直角貝の内部.きれいに隔壁が見える.
Since
we can not enter beyond the chain enclosure, the nearest of these
shells was sprayed with water to see easier the internal structure. This is the interior of a Nortiloid. The septum is clearly visible.
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これも同じく足元の別のもの.
This is another one near the foot. |
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露頭の全体の様子.沖にいくつか石灰岩の島が見える.
Overall view of the outcrop. Several limestone islands can be seen offshore.
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こちらがこの島のビーチの様子.ボートからカヌーを台にしてビーチに降りるのですが,テクニックが必要.
This is a view of a beach on this island. We need to take care getting down from the boat to the beach using a canoe as a platform.
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これが最後の観察地点の自然の猿がいたビーチ.しかし我々の姿が見えたとたん,森に姿を消した.これは猿を撮ろうとスマホを構えたが逃げられてしまったところ.
This was the last beach where we saw the natural monkeys. But as soon as they saw us, they disappeared into the forest. At that moment, I held up my iPhone to take a picture of the monkeys, but they ran away.
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さてこちらのビーチ際にもあやしい石灰岩ごろごろ.これは何か腕足貝のような気もするが.
There are some strange limestone rocks on this beach. This one looks like Brachiopods.
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こちらは明らかに腕足貝の断面だろうと,Wさんと意見が一致.
Ms. W and I agreed that this is clearly a section of a Brachiopod. |
こちらが最後に,私が見つけた古生代型アンモナイト?Goniatiteというものではないかと思っている.
Finally, this is a Paleozoic type ammonite I found, which I believe to be Goniatite. |
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わかりにくいが,中央部が水平で進行方向に斜めに落ちていくので,背斜構造の一部を見ていると思っている.この帰りの船で,久田先生と再度バイオかく乱の議論.K-T境界で下に当たる白亜紀側に,Irが染み出しているのはきっとそうだろうという,説明.なるほどと納得.
It
is difficult to see, but the central part is horizontal and falls off
obliquely in the direction of travel, so I think I am looking at a part
of the anticlinal structure. On
the return trip, Prof. Hisada and me had another discussion about
bio-disturbance, and he explained that the Ir seepage on the Cretaceous
side of the K-T boundary must be the same. I was convinced.
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層状でもありマッシブでもある部分.本当に石灰岩だらけの海岸や島々.やはり世界GeoParkはスケールが違うなと実感.
The area is both stratified and massive. Limestone coasts and islands. I realized that the world GeoPark is on a different scale rather than Japanese limestones.
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