Carbonate clumped-isotope thermometry is a promising technique that has the potential to help decode the significance of the variability of both physical and geochemical compositions of ancient carbonate rocks. This study utilizes a 600-million-year record of marine carbonate rocks from the subsurface and surface of the Sultanate of Oman to explore how burial and exhumation affected the carbonate clumped-isotope thermometer. Samples span 6 km of burial depth, and include calcite and dolomite mineralogies and a range of carbonate rock textures. We find evidence for two broad patterns in the physical and geochemical behavior of carbonate rocks during burial. The first group of carbonates yield water d 18 O VSMOW compositions slightly enriched or equal to an expected ''ice-free'' seawater composition of-1.2% and display good to fair textural preservation suggesting that cementation and lithification occurred within tens of meters of the sediment-water interface. Temperatures from the second group sit on the present-day geotherm, yield highly enriched water d 18 O VSMOW compositions, and display fair to poor textural preservation. We find no evidence for solid-state reordering in paired analyses of calcites and dolomites. Our results contribute to a growing body of work that indicates that the seawater d 18 O VSMOW composition has not changed significantly over 600 Myr and was not-6% in the Ediacaran. INTRODUCTION Marine carbonate fossils and rocks provide one of the best integrated records of ocean chemistry through time. However, the geochemistry of carbonate rocks records a series of overprinting events. During burial, shells, mud, and grains that precipitated from seawater experience dissolution to varying degrees, cements precipitate from pore fluids replacing or lithifying original components, and vein-filling and voidfilling carbonate cements precipitate from deeper-burial fluids. All of these processes leave textural evidence as well as chemical signatures and provide insight into the history of ancient rocks. The chemical metric that has arguably come closest to resolving questions concerning the postdepositional diagenetic path of a given carbonate component is the d 18 O of the mineral (Urey 1947). The d 18 O of a given carbonate component is dependent on both temperature, which changes with burial depth, and the composition of the precipitating fluid, which can change as pore fluids evolve when carbonate minerals are dissolved and reprecipitated. The d 18 O of a bulk sample of carbonate rock then reflects all the primary and secondary events, and their respective temperature and fluid histories, that are recorded by the d 18 O of various carbonate components (Brand 2004). This often-applied geochemical tool is imperfect in practice because it is impossible to deconvolve whether temperature and/or fluid composition is responsible for the observed d 18 O of a lithified carbonate rock or a single carbonate component (Urey 1947). Carbonate clumped-isotope thermometry (D 47) can deconvolve the contribution of ...

The 10 m-scale shallowing-up Neoproterozoic carbonate cycles at Qarn Alam (Oman) provide a record of microbial textures and the communities responsible for them. This is documented for four major microbialite facies. Despite their age, these microbialites show extremely fine preservation of microbial fossils and mineral associations (primary calcite and dolomite with minor phosphate, glauconite, palygorskite, hematite and goethite) and they are the record of a suite of microbial communities, from pellicular biofilms (planar laminites) to mats and gels (crinkly laminites, and stromatolitic layered and massive thrombolites) and a more complex microbial community in bushy thrombolites possibly involving a sponge-like form. Mineralized extra-cellular polymeric substances (EPS) resembles that of modern microbial mats. The mineral associations, as well as cathodoluminescence attributes, indicate oxic to suboxic conditions during deposition and early diagenesis for planar laminites and crinkly laminites, but more evaporitic to saline conditions during development of thrombolites of the upper part of a cycle. Early cementation under variable redox conditions sealed the organomineralized phases.

No abstract

Cystic fibrosis (CF) is a genetic disease caused by a mutation in the cystic fibrosis transmembrane conductance regulator (CFTR) gene that affects multisystems in the body, particularly the lungs and digestive system. We report a case of an Omani newborn who presented with meconium ileus and high suspicion of CF. Thus, full CFTR gene sequencing was performed, which revealed a homozygous unreported C.4242+1G>C novel gene mutation. Both parents were found to be heterozygous for this mutation. This case sheds light on the importance of the extensive genetic testing of typical CF cases in the absence of family history or during neonatal presentations, especially when the sweat test cannot be performed and the diagnosis can be challenging.