The fauna of the Chazy limestone / by Percy E. Raymond.

  • Raymond, Percy Edward, 1879-1952.
Date:
[1905]
Catalogue details

Licence: In copyright

Credit: The fauna of the Chazy limestone / by Percy E. Raymond. Source: Wellcome Collection.

Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.

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    sandstone hronglit with it a part of tlie C<^o^utrot(^mJl.i(^ plena fauna. The date of this invasion to the west can he rather closely approximated. Gamarotceclda pdena.^ Raphisioma staminemm., and Malocystites inurcldsoni are found in the middle of the section at L’Oriirnal. At Valcour Island these V ^ species occur together in zone 775 feet above tlie base, thus showing that the formation in the Ottawa VAlley repre- sents the very latest [)art of Chazy time. Lllrich ami Schuchert, in their paper on Paleozoic Seas and Bankers,“ bring out this idea of a (3hazy sea invading westward and southward. They state : “With the earlier,part of this subsidence [tlie Chazy invasion], the Atlantic invaded the continent westward. . . . The typical Chazy formation . . . bears evidence in its members of having encroached south- ward and westward in the arms, the latest beds . . . extend- ing farthest south and west.” Tur: Closing Period of Chazy Time. Ill the preceding pages an effort has been made to show that in northeastern New A^ork and in the Ottawa A^alley, the Chazy sea invaded over a land surface of Beekmantown rocks, and that the base of the Chazy is a tangential sandstone; also that the invasion was first southward, covering tlie region of the Champlain Yalley, and later westward along the locality of the present Ottawa Valley.4 Of the former extent of the formation throughout the St. Lawrence Valley or elsewdiere, there is at present little evi- dence. Since the sea did not attain the region of Avhner until very late Chazy time, it is probable that the formation never extended much furtlier west than the known outcrops in that region (Allumette Island, etc.). From a study of the stratigraphy and faunas it becomes evident that the upper portion of the Chazy is not represented in the region soutli of Valcour Island. Either these beds were never deposited there or they were eroded before the Lowville was laid down. Tlie evidence is not of such a character as to prove detinitely which did occur, but for reasons given below it seems more probable that the upper beds were deposited south of Valcour and later eroded. These reasons are as follows:— * Rept. N. Y. State Pal., 1902, p. 639. [f By these terms, Champlain Valley and Ottawa Valley, the writer does not intend to convey the iinjiression that the Chazy deposits were laid down in narrow arms of the sea, or that the topography was then anything like that of the present time. It should be remembered that strata of post-Chazy age are involved in the Green Mountain uplift, and that there are indications that the Adirondacks did not exist in Ordovician time.]