Beta ray induced optically stimulated luminescence properties of calcium oxide phosphor

635-638This work presents the results on optically stimulated luminescence of calcium oxide (CaO). Polycrystalline CaO phosphors are irradiated with beta rays in the dose range 10 – 100 Gy. The optically stimulated luminescence (OSL) from CaO sample is strong, the decay is fast and entire signal decays within 50 s. OSL intensity increases linearly with beta dose. The life time and photo ionization cross section (PICS) of decay are in the range ~0.045, 1.5 and 41.391 s and 1.32x10-16, 3.32x10-18 and 1.42x10-19 cm2 for fast, medium and slow components, respectively. Further, the life time and PICS of fast, medium and slow LM-OSL components have been found to be 2.29, 6.0, 17.0 s and 2.56x10-18, 9.77x10-19, 3.45x10-19 cm2, respectively. Both the OSL curves exhibits general order kinetics

Late Quaternary sedimentation in the Paraiba Basin, Northeastern Brazil: Landform, sea level and tectonics in Eastern South America passive margin

Late Quaternary deposits in the northeastern Brazil have been scarcely investigated, despite their relevance to the discussion of the post-rift evolution of the South American passive margin within the context of landform, sea level and tectonic deformation. Sedimentological, stratigraphic and morphological characterization of these deposits, referred as Post-Barreiras Sediments, led to their distinction from underlying Early/Middle Miocene strata. Based on optically stimulated luminescence (OSL) dating, two sedimentary units (PB1 and PB2) were recognized and related to the time intervals between 74.8 +/- 9.3 and 30.8 +/- 6.9 ka, and 8.8 +/- 0.9 and 1.8 +/- 0.2 ka, respectively. Unit PB1 consists of indurated sandstones and breccias either with massive bedding or complex types of soft sediment deformation structures generated by contemporaneous seismic activity. Unit PB2 is composed of massive sands or sands related to structures developed by dissipation of dunes. The present work, focusing on the Post-Barreiras Sediments, discusses landform, sea level and tectonics of the eastern South American passive margin during the latest Quaternary. Non-deposition and sub-aerial exposure related to the Tortonian worldwide low sea level combined with tectonic quiescence followed the Miocene transgression. Tectonic deformation in the latest Pleistocene created space to accommodate unit PB1 in downthrown faulted blocks and, perhaps, also synclines produced by strike-slip deformation. Although deposition of this unit was simultaneous with the progressive fall in sea level that followed the Last Interglacial Maximum, punctuated rises combined with land subsidence led to marine deposition close to the modern coastline. Renewed subsidence in the Holocene gave rise to accommodation of the Post-Barreiras Sediments. Most of unit PB2 was deposited during the Holocene Transgression, but it is not composed of marine sediments, which suggests either an insignificant rise in relative sea level or aeolian reworking of thin transgressive sands. The data presented here lead to a review of the evolution of the South American passive margin based on assumptions of uniform sedimentation and undeformed planation surfaces over a wide coastal area of the northeastern Brazil. (C) 2011 Elsevier B.V. All rights reserved.FAPESP[006/04687-7]Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP