Peryt tm hoppe a bechstaedt t koester j pierre c and

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Peryt, T.M., Hoppe, A., Bechstaedt, T., Koester, J., Pierre, C., and Richter, D.K., 1990, Late Proterozoic aragonitic cement crusts, Bambui Group, Minas Gerais, Brazil: Sedimentology, v. 37, p. 279–286. Sandberg, P., 1985, Aragonite cements and their occurrence in ancient limestone, in Schneidermann, N., and Harris, P.M., eds., Carbonate cements: SEPM (Society for Sedimentary Geology) Special Publication 36, p. 33–57. Simonson, B.M., Schubel, K.A., and Hassler, S.W., 1993, Carbonate sedimentology of the early Precambrian Hamersley Group of Western Australia: Precambrian Research, v. 60, p. 287–335. doi:10.1016/0301- 9268(93)90052-4 Sumner, D.Y., 2001, Decimeter-thick encrustations of calcite and aragonite on the sea floor and implications for Neoarchean and Neoproterozoic ocean chemistry, in Altermann, W., and Corcoran, P.L., eds., Precambrian sedimentary environments: A modern approach to ancient depositional systems: International Association of Sedimentologists Special Publication 33, p. 107–120. Sumner, D.Y., and Grotzinger, J.P., 2000, Late Archean aragonite precipitation: Petrography, facies associations, and environmental significance, in Grotzinger, J.P., and James, N.P., eds., Carbonate sedimentation and diagenesis in the evolving Precambrian world: SEPM (Society for Sedimentary Geology) Special Publication 67, p. 123–144. REPLY Lawrence A. Hardie Department of Earth and Planetary Sciences, Johns Hopkins University, Baltimore, Maryland 21218, USA Secular variations in Precambrian seawater chemistry and the timing of Precambrian aragonite seas and calcite seas: Comment and Reply
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e2 In her comment on my paper on secular variations in Precambrian seawater chemistry, Dr. Sumner has argued that aragonite pseudomorphs are abundant in the 2.5–2.6 Ga Campbellrand-Malmani carbonates of the Transvaal Basin, South Africa, occurring mainly as fibrous cements replaced by calcite crystals. My focus was not on the intragranular cements but on the very large crystal fans described by Sumner and Grotzinger (2000) in the Precam- brian Campbellrand-Malmani carbonates of the Transvaal Basin, South Africa, and the “aragonite domes” described by Simonson et al. (1993) in the equivalent age carbonates of the Carawine Dolomite of the Hamersley Basin, Australia, once joined with the Transvaal Basin. I drew particular attention to the astonishingly similar morphologies and sizes of the large domes and the large radiating crystals that make up the internal fabric of these domes to those in the primary gypsum of the Miocene Solfifera Series of Sicily (Hardie, 2003, p. 787). The Solfifera Series contains beds of radiating prismatic gypsum crystals that form domes 0.5–4 m in diameter and 0.5–1 m in height. In shape and scale they closely match the domes described and illustrated by Simonson et al. (1993). These Precambrian domal features in the Carawine Dolomite are 4.4 m wide and 1.2 m high with cores made up of concentric layers of prismatic crystals 3–20 cm long, now composed of quartz, chert, or dolomite. Simonson et al. (1993) interpreted the crystals as originally having been aragonite but found it “worrisome” that the crystal morphologies lacked the “distinctive square-tipped terminations” of radiating aragonite crystals. Simonson is
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