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The London Clay Formation is a marine geological formation of Ypresian (Lower Eocene Epoch, c. 56-49 Ma) age which crops out in the southeast of England. The London Clay is well known for the fossils it contains. The fossils from the Lower Eocene indicate a moderately warm climate, the flora being tropical or subtropical. Though sea levels changed during the deposition of the Clay, the habitat was generally a lush forest - perhaps like in Indonesia or East Africa today - bordering a warm, shallow ocean. The London Clay is a stiff bluish clay which becomes brown when weathered. There are nodular lumps of pyrite and crystals of selenite (sometimes called "waterstones") frequently in the clay, and large septarian concretions are also common. These have been used in the past for making cement. They were once dug for this purpose at Sheppey, near Sittingbourne, and at Harwich, and also dredged off the Hampshire coast. The clay is still used commercially for making bricks, tiles, and coarse pottery in places such as Michelmersh in Hampshire.〔(【引用サイトリンク】title=Michelmersh Brick and Tile Company )〕 It is infertile for gardens and crops. ==Distribution and geology== The London Clay is well developed in the London Basin, where it thins westwards from around in Essex and north Kent to around in Wiltshire. though it is not frequently exposed as it is to a great extent covered by more recent Neogene sediments and Pleistocene gravel deposits. One location of particular interest is Oxshott Heath, where the overlying sand and the London Clay layers are exposed as a sand escarpment, rising approximately . This supported a thriving brick industry in the area until the 1960s. The London Clay is also well developed in the Hampshire Basin, where an exposure thick occurs at Whitecliff Bay on the Isle of Wight and around is spread along of foreshore at Bognor Regis, West Sussex. The clay was deposited in a sea up to deep at the eastern end. Up to five cycles of deposition (representing transgression followed by shallowing of the sea) have been found, most markedly at the shallower, western end. Each cycle begins with coarser material (sometimes including rounded flint pebbles), followed by clay which becomes increasingly sandy. The final cycle ends with the Claygate Beds.〔 ===Claygate Beds=== The youngest part of the London Clay, known as the ''Claygate Beds'' or ''Claygate Member'' forms a transition between the clay and the sandier Bagshot Beds above. This is shown separately on many geological maps, and often caps hills. It is up to thick at Claygate, Surrey.〔 It is now believed to be diachronous, with the formation at Claygate for example being the same age as the end of the fourth cycle of deposition further east. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「The London Clay Formation is a marine geological formation of Ypresian (Lower Eocene Epoch, c. 56-49 Ma) age which crops out in the southeast of England. The London Clay is well known for the fossils it contains. The fossils from the Lower Eocene indicate a moderately warm climate, the flora being tropical or subtropical. Though sea levels changed during the deposition of the Clay, the habitat was generally a lush forest - perhaps like in Indonesia or East Africa today - bordering a warm, shallow ocean.The London Clay is a stiff bluish clay which becomes brown when weathered. There are nodular lumps of pyrite and crystals of selenite (sometimes called "waterstones") frequently in the clay, and large septarian concretions are also common. These have been used in the past for making cement. They were once dug for this purpose at Sheppey, near Sittingbourne, and at Harwich, and also dredged off the Hampshire coast. The clay is still used commercially for making bricks, tiles, and coarse pottery in places such as Michelmersh in Hampshire.(【引用サイトリンク】title=Michelmersh Brick and Tile Company ) It is infertile for gardens and crops.==Distribution and geology==The London Clay is well developed in the London Basin, where it thins westwards from around in Essex and north Kent to around in Wiltshire. though it is not frequently exposed as it is to a great extent covered by more recent Neogene sediments and Pleistocene gravel deposits. One location of particular interest is Oxshott Heath, where the overlying sand and the London Clay layers are exposed as a sand escarpment, rising approximately . This supported a thriving brick industry in the area until the 1960s. The London Clay is also well developed in the Hampshire Basin, where an exposure thick occurs at Whitecliff Bay on the Isle of Wight and around is spread along of foreshore at Bognor Regis, West Sussex.The clay was deposited in a sea up to deep at the eastern end. Up to five cycles of deposition (representing transgression followed by shallowing of the sea) have been found, most markedly at the shallower, western end. Each cycle begins with coarser material (sometimes including rounded flint pebbles), followed by clay which becomes increasingly sandy. The final cycle ends with the Claygate Beds.===Claygate Beds=== The youngest part of the London Clay, known as the ''Claygate Beds'' or ''Claygate Member'' forms a transition between the clay and the sandier Bagshot Beds above. This is shown separately on many geological maps, and often caps hills. It is up to thick at Claygate, Surrey. It is now believed to be diachronous, with the formation at Claygate for example being the same age as the end of the fourth cycle of deposition further east.」の詳細全文を読む スポンサード リンク
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