Clay Petrology Of Cambro-Ordovician Continental Margin, Cow Head Klippe, Western Newfoundland

• Published in: Clays and Clay Minerals
• Main Authors: Suchecki, Robert K., Perry, Edward A., Hubert, John F.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Cambridge University Press (CUP) 1977
• Subjects: Newfoundland
• Online Access: http://dx.doi.org/10.1346/ccmn.1977.0250301; https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0009860400003220

Abstract The sedimentary rocks of the Taconic Cow Head klippe contain three clay-mineral suites of progressively younger stratigraphic occurrence. An illite—14A chlorite suite is the oldest, occurring in the Middle Cambrian to early Lower Ordovician part of the 310-m Cow Head Breccia. These earliest clays were transported from the stable craton and shelf, slowly accumulating during 70 x 10 6 yr on the continental slope in limestone breccia, green and gray shale, and argillaceous limestone. The illite and 14A chlorite are judged to be largely detrital. An illite-expandable chlorite suite is in early to late Lower Ordovician limestone breccia, green and gray shale, and argillaceous limestone of the Cow Head Breccia. A corrensite-illite-smectite suite of late Lower to Middle Ordovician age occurs in the Cow Head Breccia and throughout the overlying 200-m ‘Red Shale’ and the more than 400-m ‘Green Sandstone’ flysch sequence of volcanogenic sandstone and gray shale. Beginning in the early Lower Ordovician, increasing amounts of Mg 2+ -rich volcanic detritus were rapidly transported westward from a developing volcanic island arc in central Newfoundland. During burial metamorphism, volcanic materials and their alteration products reacted to form the illite-smectite with 5–10% expandable layers plus corrensite or expandable chlorite found in the younger two clay-mineral suites.