Processing of cometary grains at the nucleus surface

Cometary material inevitably undergoes chemical changes before and on leaving the nucleus. In seeking to explain comets as the origin of many IDPs (interplanetary dust particles), an understanding of potential surface chemistry is vital. Grains are formed and transformed at the nucleus surface; much of the cometary volatiles may arise from the organic material. In cometary near-surface permafrost, one expects cryogenic chemistry with crystal growth and isotope. This could be the hydrous environment where IDPs form. Seasonal and geographic variations imply a range of environmental conditions and surface evolution. Interplanetary dust impacts and electrostatic forces also have roles in generating cometary dust. The absence of predicted cometary dust envelopes is compatible with the wide range of particle structures and compositions. Study of IDPs would distinguish between this model and alternatives that see comets as aggregates of core-mantle grains built in interstellar clouds.     

Nitrous oxide production and denitrification rates in estuarine intertidal saltmarsh and managed realignment zones

Increasing concerns over habitat loss and rising costs of sea defence maintenance due to rising sea levels, has seen increases in the practice of managed realignment and reflooding of former reclaimed areas of intertidal saltmarsh and mudflat around the world. These practices are taking place with little knowledge of their impact on soil biogeochemical processes. Rates of denitrification (using the acetylene inhibition technique) and nitrous oxide (N₂O) production were measured from a long-established saltmarsh (SM) and an adjacent, recently re-flooded managed realignment (MR) site comprising former arable land in the estuary of the River Torridge, Devon, UK. Incubations were carried out in closed chambers in which patterns of tidal flooding were simulated automatically. Measurements were made during periods of flood and non-flood over a total of four tidal inundations with estuarine water. During the latter two flooding episodes floodwater was amended with nitrate (NO₃⁻). Nitrous oxide production in the SM soil generally was lower than in the MR soil, with mean values and standard errors over the whole incubation of 0.27 ± 0.16 mg N₂O-N m⁻² h⁻¹ and 0.65 ± 0.15 mg N₂O-N m⁻² h⁻¹ respectively. Denitrification rates demonstrated a similar trend although generally were an order of magnitude higher than N₂O production, with mean rates and standard errors of 2.88 ± 1.12 mg N₂O-N m⁻² h⁻¹ in the SM soil and 3.39 ± 1.16 mg N₂O-N m⁻² h⁻¹ in the MR soil. The data suggest that both soils are net sinks for NO₃⁻ and net sources for N₂O. Both patterns of tidal inundation and floodwater chemistry affect the process rates in each soil differently. The impact of flooding with NO₃⁻ – amended water was greater on the SM soil than the MR soil, and it is likely that decomposing vegetation buried in the accreting sediments following reflooding at the MR site were supplying a source of N in the soil, and so process rates were less dependent upon external supplies. The act of managed realignment in intertidal zones could therefore result in an increase in mean production of N₂O in intertidal zones, at least in the short term.     

Processing of cometary grains at the nucleus surface

Cometary material inevitably undergoes chemical changes before and on leaving the nucleus. In seeking to explain comets as the origin of many IDPs (interplanetary dust particles), an understanding of potential surface chemistry is vital. Grains are formed and transformed at the nucleus surface; much of the cometary volatiles may arise from the organic material. In cometary near-surface permafrost, one expects cryogenic chemistry with crystal growth and isotope. This could be the hydrous environment where IDPs form. Seasonal and geographic variations imply a range of environmental conditions and surface evolution. Interplanetary dust impacts and electrostatic forces also have roles in generating cometary dust. The absence of predicted cometary dust ‘envelopes’ is compatible with the wide range of particle structures and compositions. Study of IDPs would distinguish between this model and alternatives that see comets as aggregates of core-mantle grains built in interstellar clouds.     

Basin evolution model during cretaceous in the northeastern of Arabian plate in Kurdistan region

The research area concentrates in a part of the main Zagros fold and thrust belt in the Kurdistan region (Northern Iraq). From study tectono-stratigraphy we constrain the story of the basin evolution of Kurdistan during Cretaceous. However we mainly investigated the evolution of the pre-Subduction and Pre-collision periods, focusing on the relationship between tectonics and sedimentation. For this purposes we developed (1) a biostratigraphic approach using nannofossil analysis, (2) a fault tectonic analysis, and (3) a stratigraphic study. The Zagros fold belt in Kurdistan exhibits many lateral and vertical environmental and facies changes, especially during the Cretaceous times. During the Jurassic period the Kurdistan is occupied by the restricted Gotnia Basin. This basin disappeared and the Kurdistan area changed to open marine of a southwest Kermanshah Basin during the Cretaceous. During the Berriasian to Barremian the Kurdistan was covered by the carbonates of the Balambo and Sarmord formations. In the east and southeast the neritic Sarmord Formation gradationally and laterally passes to the basinal facies of the Balambo Formation. In the Aptian to Cenomanian period shallow massive reefal limestone of the Qamchuqa Formation deposited. The normal faulting that initiates during the Aptian is associated with an abrupt lateral change of the reefal Qamchuqa Formation to the Aptian-Cenomanian part of the Balambo Formation. During the Cenomanian-Early Turonian periods the graben formed in the Dokan Lake in eastern Kurdistan, where developed a deeper restricted environment (Dokan and Gulneri formations) surrounded by a shallow marine platform. During the Turonian the marine pelagic micritic cherty limestones of Kometan Formation covered northeast of Kurdistan, whereas in the Safeen, Shakrok and Harir anticlines the formation was totally, or partially, weathered during the Coniacian-Early Campanian period. The deposition during the Late Cretaceous is very heterogeneous with a gap in the Coniacian-Santonian times probably related to a non-deposition. Associated with extensive tectonics a basin developed during the Campanian with the deposition of shales, marls and marly limestones of the Shiranish Formation. The first appearance is the Kurdistan of the flysch facies of the Tanjero Formation was precisely dated of the Upper Campanian in northeastern Kurdistan. The Tanjero Formation conformably overlaying the Shiranish Formation and was deposited in the foredeep basin associated with the obduction of Tethyan ophiolites onto the Arabian Platform. The Early to Late Campanian period is a time of non-deposition in Central Kurdistan (Safeen, Shakrok and Harir anticlines). During the Late Campanian the Bekhme carbonate platform in the north disappeared when the marly limestones of the Shiranish Formation transgressed over the Bekmeh Platform. In the Aqra area the Maastrichtian Tanjero Formation laterally changed to the thick reefal sequence of the Aqra Formation that unconformably overlies by the Late Paleocene-Early Eocene lagoonal carbonate of the Khurmala Formation. The Campanian sedimentation is mainly controlled by NE- oriented normal faults forming Grabens in Dokan, Spilk and Soran areas. During the Maastrichtian in the extreme northeastern Kurdistan the NE-SW and NNW-SSE normal faults developed in the foredeep basin and originated horsts and grabens.