Distinctive peritidal tepee antiform structures, buckled margins of saucer‐like megapolygons are common in marine vadose fenestral and pisolitic limestones and/or dolomites of carbonate platform sequences and occur in intertidal and supratidal carbonates ranging in age from Silurian to Holocene. These megapolygons commonly form and are sometimes truncated before the deposition of the next sedimentary layer. The megapolygons result from the expansion of surface sediments by as much as 15%. The expansion is caused by the following continuously repeated sequence of processes: (1) Desiccation and thermal contraction causing small fractures; (2) phases of wetting causing enlargement of fractures; (3) phases of crystallization of calcium carbonate and other minerals causing the enlargement, fill and cementation of the fractures. Precipitation is from brines and meteoric waters; (4) hydration of minerals, thermal expansion, breaking waves and faulting may add to this disruption. The development of the tepee fabric can be traced from an initially cemented subaerial fenestral crust, exhibiting expansion and compressional structures, to a completely disrupted and brecciated sediment riddled by a labyrinth of fractures and solution cavities. These spaces are filled by numerous phases of internal marine and fresh‐water cement and sediment, the latter containing penecontemporaneous or younger marine faunas. Peritidal tepees are useful tools for geologic reconstruction and provide evidence of subaerial exposure; a tropical to subtropical climate; and back‐beach or back‐barrier deposition. Proper identification of tepees is of economic importance, because they provide good early porosity and permeability for petroleum entrapment and a site for mineralization. Aesthetically, tepee rocks are a fine kaleidoscopic decorative stone.

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The s7Sr/R6Sr ratios and strontium concentrations for thirty-three samples of marine carbonate rocks of Middle Triassic to Early Jurassic age have been determined. The samples were collected from four measured sections in the areas of Val Camonica in northern Italy. The strontium concentrations vary from 40 to 7000 ppm. Most of the samples are calcitic limestones containing less than 10% of non-carbonate residues. Dolomitic samples and those containing appreciable non-carbonate residues have significantly diminished strontium concentrations.The n7Sr/R6Sr ratios of the carbonate phases of these rocks appear to be unaffected by dolomitization and by the presence of non-carbonate minerals. The average a'Sr/a6Sr ratios of the formations vary systematically in a stratigraphic sense. The ratio increased from Early Anisian to Early-Middle Ladinian, declined during Late Ladinian and Carnian, rose again during the Norian and then declined throughout the Late Norian (Rhaetian), Hettangian, Sinemurian and Pliensbachian ages. The average B'Sr/s6Sr ratios, relative to 0.7080 for the Eimer and Amendstandard,are: Anisian:0.70805f 0.00019;Early Ladinian:0,7085+0.00038;Late Ladinian: 0.70791 +0.00013; Carnian: 0~70776+0~00015; Norian and Rhaetian: 0,70791 .+ 040014; Hettangian: 0~70762+0~00021 : Sinemurian: 0.7070&0-00038; Pliensbachian: 0.7070+ 0.00015. These variations reflect changes in the isotopic composition of Sr entering the oceans in early Mesozoic time due to varying rates of weathering and erosion of young volcanic rocks (low 87Sr/e6Sr) and old granitic rocks (high s7Sr/asSr). The data presented in this report contribute to a growing body of information regarding the changes that have occurred in the g7Sr/68Sr ratio of the oceans in Phanerozoic time.

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