Petrography of gypsum-bearing facies of the Codó Formation (Late Aptian), Northern Brazil.

An original and detailed study focusing the petrography of evaporites from the Late Aptian deposits exposed in the eastern and southern São Luís-Grajaú Basin is presented herein, with the attempt of distinguishing between primary and secondary evaporites, and reconstructing their post-depositional evolution. Seven evaporites phases were recognized: 1. chevron gypsum; 2. nodular to lensoidal gypsum or anhydrite; 3. fibrous to acicular gypsum; 4. mosaic gypsum; 5. brecciated gypsum or gypsarenite; 6. pseudo-nodular anhydrite or gypsum; and 7. rosettes of gypsum. The three first phases of gypsum display petrographic characteristics that conform to a primary nature. The fibrous to acicular and mosaic gypsum were formed by replacement of primary gypsum, but their origin took place during the eodiagenesis, still under influence of the depositional setting. These gypsum morphologies are closely related to the laminated evaporites, serving to demonstrate that their formation was related to replacements that did not affect the primary sedimentary structures. The pseudo-nodular anhydrite or gypsum seems to have originated by mobilization of sulfate-rich fluids during burial, probably related to halokinesis. The rosettes of gypsum, which intercept all the other gypsum varieties, represent the latest phase of evaporite formation in the study area, resulting from either intrastratal waters or surface waters during weathering.

Growth of adolescents who were born at extremely low birth weight without major disability.

OBJECTIVE: To compare growth between adolescents who were born at extremely low birth weight (ELBW, /=2500 g). DESIGN/METHODS: Cross-sectional design. Fifty-three ELBW and 53 NBW adolescents without a major neurodevelopmental disability were matched by sex, race, age, and socioeconomic status. Anthropometrics (z scores), bone age, body composition (Lunar DPX-L densitometry), and sexual maturity were assessed. ELBW adolescents were classified as being born small for gestational age (SGA) or not (NSGA). RESULTS: Subjects were 58.5% female, 43.4% black, and 56.6% white. The mean birth weight for ELBW subjects was 849 g and 3355 g for NBW subjects. The mean age was 14.85 years. On average, ELBW adolescents were 4.8 cm shorter and 9.1 kg lighter than NBW adolescents. ELBW adolescents had lower mean z scores for height (P <.0001), weight (P <.0001), and head circumference (P <.0001) than NBW adolescents. ELBW/SGA subjects had lower mean z scores for height (P <.0001) and weight (P =.001) than NBW subjects. Head circumference z scores were lower for the ELBW/SGA group than the ELBW/NSGA group or the NBW group (P =. 003). Sexual maturity and relative body composition were similar between groups. Bone age, measured in SD units, was more advanced in the ELBW group (0.86 vs. 0.42, P =.039). CONCLUSIONS: ELBW adolescents who survive without a major neurodevelopmental disability attain lower growth measurements compared with NBW adolescents but have similar sexual maturation and relative body composition.