A catalog is presented of 1217 post-1890 published amphibole analyses which contain 6.00 per cent or more of CaO. Of these, 1106 are accompanied by at least one refractive index, an optic angle, or a density determination. With each analysis is given these physical constants; as well as the half-unit cell contents calculated on the basis of 24 (O, OH, F, Cl); the reference source; the locality; the mineral assemblage in which the amphibole occurs; whether any coexisting minerals have been analyzed; an indication of the quality of the analysis; and, to each amphibole, a name which conveys the composition rather precisely. A rational nomenclature is proposed for these amphiboles, the naming of which is, at present, highly confused. The calciferous amphiboles are defined as those with Ca 1.50 and above in the half-unit cell, while the subcalciferous amphiboles contain between 1.00 and 1.50 Ca in the half-unit cell. The system proposed is based on the well-known end members tremolite, richterite, tschermakite, edenite, pargasite, and hastingsite. Three important variables define the main name to be given to an amphibole, namely the amounts of Si, Ca+Na+K, and Mg/Mg+Mn+Fe 3 +Fe 2 in the half-unit cell. Prefixes then indicate the ranges of Na, Ca, Ti, Al VI , Mn, Cr, K, Cl, OH, and Fe 3 /Fe 2 . This avoids making new names other than those obtained by prefixing adjectives, retains the traditional meanings of the well-known end members and such terms as actinolite and kaersutite, dispenses with the need for the more obscure names, and enables the composition, with respect to no less than 15 variables, to be conveyed by the name. Criteria to distinguish between good and poor amphibole analyses are suggested, discussed, and applied to the collection of amphibole analyses. Using these criteria, one third of the analyses appear to be of superior quality, one third of moderate quality, and the remaining third of inferior quality. Of recent analyses, roughly half are of superior quality. Therefore, even on a purely empirical basis, these criteria appear to be useful. Frequency-distribution polygons show the ranges of composition and the most frequent compositions found in these amphiboles with respect to Fe 3 , Mn, Na, K, Ti, Ca, Si, OH, F, and Mg/Mg+Fe 2 +Fe 3 +Mn. A series of plots of analyzed amphiboles coexisting with analyzed clinopyroxenes, orthopyroxenes, biotites, garnets, and Ca-poor amphiboles summarizes the available information on these coexisting pairs and thus enables a number of interesting deductions to be made.

Abstract The Aptian Barbalha Formation records the beginning of the post-rift stage of the Araripe Basin. It consists predominantly of sandstones and mudstones interbedded with thin layers of bituminous black shales and conglomerates. The depositional and architectural features of the alluvial succession of the Barbalha Formation were characterized by detailed study and descriptions of the selected outcrops and analysis of well core data. In this study, two main depositional sequences were identified. The lower depositional sequence is more than 100 m thick and comprises a vertical facies succession composed of amalgamated, multistorey, braided fluvial channel sandstone bodies overlain by a widespread lacustrine black shale up to 10 m thick. The lacustrine black shales–carbonate mixed interval is known as the Batateira Beds and constitutes a regionally important stratigraphic correlation marker in the basin. This interval records the establishment of a large lake that experienced severe water-level fluctuations and anoxic events. The upper depositional sequence is 60–95 m thick, and mainly consists of thin, yellowish, medium- to fine-grained sandstones and variegated shales. The upper sequence rests unconformably on the lacustrine black shales of the Batateira Beds. Thin and discontinuous conglomerate beds at the base of the upper sequence laterally grade into coarse-grained sandstones. These coarse-grained sandstones are overlain by interbedded sandstones and mudstones organized in fluvial cycles. The upper and lower sequences of the Barbalha Formation are separated by an erosive unconformity, traceable throughout the study area, formed during a period of stratigraphic base-level lowering. This surface marks a change in the lower sequence from a dominantly fluvial depositional style, with amalgamated multistorey braided fluvial channel sand bodies, to a lacustrine system in the top to an eminently fluvial sedimentation, which in the basal section comprises amalgamated, multistorey, braided fluvial channel sand bodies, and in the superior section the amalgamated fluvial channels are overlain by floodplain and overbank sandstone bodies with fixed fluvial channel deposits, interpreted as a suspended-load-dominated fluvial system in the upper sequence. This change in the depositional style is accompanied by a reduction in grain size and a change in the fluvial regime, suggesting that the drainage system was restructured due to tectonic movements in the basin and climatic variations. In addition to the restructuring of the drainage basin, the characteristics of the discharge of the river system have changed, probably because of the more humid climatic conditions that dominated during the deposition of the upper sequence. The fluvial deposition in the lower sequence is associated with more ephemeral river systems, while the facies architecture of the upper sequence is associated with perennial systems and is suggestive of a suspended-load-dominated fluvial system. This fluvial system is capped by lacustrine deposits of the Crato Formation. The upper sequence grades upwards into the Crato Formation. The boundary between these two units is delineated by the presence of greenish calciferous shales that are covered by lacustrine laminated limestones and shales of Neoaptian age. Palaeocurrent readings from the fluvial deposits of both sequences display a consistent palaeoflow to the SE. Sedimentological and palaeontological evidence indicates a tectonic control on sedimentation and humid to subhumid climate conditions.