Crossword-Solution: OSTRE 5 letters, 1 clue 🏆 scrabble score: 5

The lowest bed is an obliquely laminated, blackish, indurated mud, with distinct traces of vegetable remains.[13] Above this there is a thick bed of yellowish sandy clay, with much crystallised gypsum and many shells of Ostreæ, Pectens, and Arcæ: above this there generally comes an arenaceous crystalline limestone, but there is sometimes interposed a bed, about twelve feet thick, of dark green, soapy clay, weathering into small angular fragments.