The role of early lithification in development of chalky porosity in calcitic micrites: Upper Cretaceous chalks, Egypt

Petrological and geochemical examination of Upper Cretaceous chalks from the Abu Roash area and Bahariya Oasis (Egypt) provide insights into factors which control porosity development in fine-grained calcitic carbonates.Petrological studies indicate that primary skeletal fabrics of coccoliths and foraminifera in micrites of Abu Roash are well preserved. In contrast, primary skeletal fabrics of the Bahariya Oasis chalks are pervasively altered. Geochemical analysis of these chalks reveals a striking contrast in composition. The high porosity chalks at Bahariya Oasis have depleted isotopic values ([delta]13C = -5.0[per mille sign], [delta]18O = -8.9[per mille sign] PDB) and low concentrations of trace elements (Sr and Na). In contrast, the low porosity chalks at Abu Roash are less depleted in terms of their isotopic values ([delta]13C = 1.0[per mille sign], [delta]18O = -4.0[per mille sign]) and possess elevated concentrations of Sr, Na, Fe and Zn. Importantly, fracture and collapse veins, present only at Abu Roash, are filled with calcite whose [delta]18O value is coincident with that of altered micrites at Bahariya Oasis. The lithic fragments cemented by this calcite, however, retain compositions identical to other lithified limestones at Abu Roash.Differences in fabric and chemistry of the pelagic marine micrites observed between Abu Roash and Bahariya Oasis reflect the degree of early lithification and compaction prior to exposure and meteoric diagenetic alteration associated with regional Late Cretaceous/pre-Eocene subaerial unconformity.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/31901/1/0000854.pd

DAM-Net: Global Flood Detection from SAR Imagery Using Differential Attention Metric-Based Vision Transformers

The detection of flooded areas using high-resolution synthetic aperture radar (SAR) imagery is a critical task with applications in crisis and disaster management, as well as environmental resource planning. However, the complex nature of SAR images presents a challenge that often leads to an overestimation of the flood extent. To address this issue, we propose a novel differential attention metric-based network (DAM-Net) in this study. The DAM-Net comprises two key components: a weight-sharing Siamese backbone to obtain multi-scale change features of multi-temporal images and tokens containing high-level semantic information of water-body changes, and a temporal differential fusion (TDF) module that integrates semantic tokens and change features to generate flood maps with reduced speckle noise. Specifically, the backbone is split into multiple stages. In each stage, we design three modules, namely, temporal-wise feature extraction (TWFE), cross-temporal change attention (CTCA), and temporal-aware change enhancement (TACE), to effectively extract the change features. In TACE of the last stage, we introduce a class token to record high-level semantic information of water-body changes via the attention mechanism. Another challenge faced by data-driven deep learning algorithms is the limited availability of flood detection datasets. To overcome this, we have created the S1GFloods open-source dataset, a global-scale high-resolution Sentinel-1 SAR image pairs dataset covering 46 global flood events between 2015 and 2022. The experiments on the S1GFloods dataset using the proposed DAM-Net showed top results compared to state-of-the-art methods in terms of overall accuracy, F1-score, and IoU, which reached 97.8%, 96.5%, and 93.2%, respectively. Our dataset and code will be available online at https://github.com/Tamer-Saleh/S1GFlood-Detection.Comment: 16 pages, 11 figure

Twelve-month observational study of children with cancer in 41 countries during the COVID-19 pandemic

Introduction Childhood cancer is a leading cause of death. It is unclear whether the COVID-19 pandemic has impacted childhood cancer mortality. In this study, we aimed to establish all-cause mortality rates for childhood cancers during the COVID-19 pandemic and determine the factors associated with mortality. Methods Prospective cohort study in 109 institutions in 41 countries. Inclusion criteria: children <18 years who were newly diagnosed with or undergoing active treatment for acute lymphoblastic leukaemia, non-Hodgkin's lymphoma, Hodgkin lymphoma, retinoblastoma, Wilms tumour, glioma, osteosarcoma, Ewing sarcoma, rhabdomyosarcoma, medulloblastoma and neuroblastoma. Of 2327 cases, 2118 patients were included in the study. The primary outcome measure was all-cause mortality at 30 days, 90 days and 12 months. Results All-cause mortality was 3.4% (n=71/2084) at 30-day follow-up, 5.7% (n=113/1969) at 90-day follow-up and 13.0% (n=206/1581) at 12-month follow-up. The median time from diagnosis to multidisciplinary team (MDT) plan was longest in low-income countries (7 days, IQR 3-11). Multivariable analysis revealed several factors associated with 12-month mortality, including low-income (OR 6.99 (95% CI 2.49 to 19.68); p<0.001), lower middle income (OR 3.32 (95% CI 1.96 to 5.61); p<0.001) and upper middle income (OR 3.49 (95% CI 2.02 to 6.03); p<0.001) country status and chemotherapy (OR 0.55 (95% CI 0.36 to 0.86); p=0.008) and immunotherapy (OR 0.27 (95% CI 0.08 to 0.91); p=0.035) within 30 days from MDT plan. Multivariable analysis revealed laboratory-confirmed SARS-CoV-2 infection (OR 5.33 (95% CI 1.19 to 23.84); p=0.029) was associated with 30-day mortality. Conclusions Children with cancer are more likely to die within 30 days if infected with SARS-CoV-2. However, timely treatment reduced odds of death. This report provides crucial information to balance the benefits of providing anticancer therapy against the risks of SARS-CoV-2 infection in children with cancer

Stable isotopic composition and its relation to origin and diagenesis of some Upper Cretaceous dolomites and dolomitic limestones from Egypt

The Upper Cretaceous sedimentary sequence in northern Egypt consists of a variety of platform carbonate units in which originally calcitic components have been totally or partially replaced by dolomite. Replacement is partial in the Abu Roash sequence whereas it is complete in the Bahariya Oasis and Gebel Ataqa sequences. Detailed examination of sedimentary structures, lithologies, fossil contents, and fabric relationships demonstrates that these shallow marine facies comprise a shoaling-upward sequence bounded above by a major pre-Middle Eocene unconformity overlain by a Middle Eocene carbonate sequence. Petrographic, cathodoluminescence, trace element, and isotope techniques were used to investigate the genesis and textural relationships among two generations of dolomite and late void-filling calcite in this sequence. Early diagenetic dolomite records limestone replacement in the presence of marine-derived fluids, whereas the later stage records dolomitization and cementation in the presence of mixed meteoric-marine water. However, microcrystalline dolomite of the Red Bed Series shows trace elemental and isotopic signatures of hypersaline dolomitization. Cathodoluminescence reveals that replacive matrix dolomite rhombs exhibit dully luminescent cores with dull to bright rims, whereas dolomite cement exhibits finely-zoned bright luminescence. However, dolomite cement and stabilization of previously formed dolomite in the Bahariya Oasis sequence are represented by dolomite that shows a unique bright creamy CL color. The excess radiogenic Sr of this dolomite reflects an increased supply of meteoric-water which intensified weathering of overlying more radiogenic clastic sources. Finally, the late void-filling calcite spar, a distinctive CL-zoned phase, occurs throughout the stratigraphic sequence. Examination of this cement within the Maastrichtian chalks which regionally overlie the dolomite sequence has demonstrated that this calcite is related to infiltration of meteoric water during the regional erosional exposure. Petrological and geochemical examination of the Maastrichtian chalks from Bahariya Oasis and Abu Roash provides insight into factors that control porosity development in fine-grained calcitic carbonates. High porosity chalks at Bahariya Oasis have depleted isotopic values and low concentrations of minor elements. In contrast, the low porosity chalks at Abu Roash have more enriched isotopic values and elevated concentration of Sr, Na, Mg, Fe, and Zn. (Abstract shortened with permission of author.

اتجاهات عمليات ما بعد الترسيب في تلال البلايستوسين الجيرية بمنطقة مرسى مطروح - مصر

Ooids are a major constituent of the Pleistocene carbonates along the northwestern coastal ridges of Egypt. For a detailed diagenetic study of the rocks, the Mersa Matruh area was selected. Petrographic examination shows that the rocks are partly consolidated ooid grainstones with low-Mg calcite cement in granular voids. 818O, 813C, and Sr values were determined on whole rock samples, on the manually separated ooids and calcite cements. Oxygen isotopic and Sr values for the whole rock (+0.5%o PDB; 9,300 ppm) are consistent with data on limestones of the same age. In contrast, oxygen isotopic values for ooids (average +0.5%o PDB) are heavier relative to values for low-Mg calcite cement (average -\A%o PDB) and Sr contents are higher for ooids (10.000 ppm). In addition, 813C values are identical for the whole rock and ooids (average + 4.5%o PDB) and heavier relative to 813C values of the calcite cements (ranging from +4.1 to +3.8%O PDB). These data may suggest that calcite cements are formed in non-diluted pore-water under relatively high rock/water ratios.تتواجد صخور الكربونات التابعة للبلايستوسين على هيئة تلال بامتداد الساحل الشمالي الغربي لمصر ، وهي تتكون غالبا من حبيبات بطروخية . ولإجراء دراسة تفصيلية عن عمليات ما بعد الترسيب لهذه الصخور فقد تم اختيار منطقة مرسى مطروح حيث أوضح الفحص البتروجرافي لهذه العينات أن هذه الصخور تتكون من حبيبات متماسكة جزئيا مع وجود مادة لاحمة من الكالسيت المنخفض في نسبة المغنسيوم تملأ الفراغات البينية . وقد تم تحديد قيم كل من نظير الاكسجين - 18 والكربون - 13 والإسترونشيوم في عينات الصخور الكلي وعلى الحبيبات البطروخية التي تم فصلها يدويا وكذلك على الكالسيت اللاحم حيث وجد أن نسبة نظير الاكسجين ( +0.5 جزء في الألف ) والاسترونشيوم (9.300 جزء في المليون ) في عينات الصخر الكلي مطابقة للبيانات المنشورة للاحجار االجيرية التي لها نفس العمر الجيولوجي ، وعلى النقيض من هذا فقد وجد أن نسبة نظير الاكسجين في الحبيبات البطروخية ( متوسطها +0.5جزء في الألف ) تعتبر عالية عند مقارنتها بقيم لحام الكالسيت المنخفض في نسبة المغنسيوم ( متوسطها - 1.4 جزء في الألف ) ، كما أن الحبيبات البطروخية تحتوي عل نسبة عالية من الاسترونشيوم تصل إلى10.000جزء في المليون . بالإضافة إلي هذا فإن نسبة نظير الكربون – 13 متشابهة في كل من عينات الصخر الكلي والحبيبات البطروخية حيث تبلغ في المتوسط + 4.5 جزء في الألف والتي تعتبر مرتفعة عند مقارنتها بنسبة نظير الكربون - 13 في الكالسيت اللاحم والتي تتراوح بين +1.4 ، +3.8 جزء في الألف . ومن هذه البيانات يمكن اقتراح أصل - الكالسيت اللاحم حيث يتكون من المياه الغير مخففة في الفراغات البينية في ظروف تميزت بنسبة عالية للصخر إلى المياه

تغيرات ما بعد الترسيب " ضفة النيميوليت " لعصر الأيوسين الأوسط في هضبة أهرامات الجيزة بمصر : أدلة بتروجغرافية ونظائرية

The Middle Eocene "nummulite bank" of the Giza Pyramids Plateau has been extensively altered diagenetically. The result of a study involving petrography, cathodoluminescence, and 18O/160 and 13C/12C data, provide information about origin and nature of the diagenetic fluids, as well as magnitude and timing of the diagenetic stages. A sequence of petrologic features coupled with the.geochemical characters suggests a progression of diagenetic fluids from marine to meteoric. The micrite rock matrix isotopic compositions depart from an initial marine composition (-2.9%o 8I8O and +0.5%o 813C PDB) along covariant trends that reflect slight alteration by diagenetic pore waters. The nummulite grains show isotopic composition close to the isotopic composition of marine carbonates (-1.8%o 818O and + 1.9%o 813C PDB). The early diagenetic alteration of the rock matrix was followed by partial to complete dolomitization of the limestone matrix and nummulite grains. The oxygen isotopic ratios of the matrix-replacive dolomites range from -0.6 to +1.2%o PDB, whereas the carbon isotopic ratios range from +0.8 to +3.0%o PDB. These isotopic ratios suggest that dolomitization occurred in marine-dominated mixed waters at low temperatures. The final diagenetic phase involve the precipitation of a blocky calcite spar cements (ave. -9.6%o 818O and -4.2%o 813C PDB).تعرضت " ضفة النيميوليت " التابعة لعصر الأيوسين الأوسط في هضبة أهرامات الجيزة بمصر إلى تغيرات كبيرة بعد ترسبها . وتتضمن الدراسة الحالية عدة جوانب عن البتروجرافيا ، الوميض الكاثودي ، تحليل نظائري للأكسجين والكربون حيث وفرت نتائجها معلومات عن مصدر وطبيعة سوائل ما بعد الترسيب وكذلك مدى وفترة مراحل التغيرات التي حدثت بعد الترسيب . وقد أوضحت المظاهر البتروجوافية والخواص الجيوكيميائية أن سوائل ما بعد الترسيب قد تدرجت من بحرية إلى جوية ، فقد تغير التركيب النظائري لأرضية الصخور دقيقة الحبيبات من تركيب بحسي أولي (-9،2 أكسجين -18 ، +5 ، . كربون -13) عبر اتجاهات معينة تعكس تغيرات بسيطة بعد الترسيب بفعل المياه بين الحبيبات . أما حبيبات النيميوليت فقد أوضحت تركيباً نظائريا يتراوح بين التركيب االبحري في هضبة أهرامات الجيزة ( - 1,8 أكسجين -18 ، +9,1 كربون -13) إلى تركيب مياه عذبة (-6، 10 أكسجين 18 ، -7,2 كربون -13) في منطقة الفيوم والواحات البحرية ، وقد تلى هذا التغير الأولي في أرضية الصخر إحلال دولوميتي لأرضية الحجر الجيري وحبيبات افيميوليت ، كما ترسبت بلورات كاملة الأوجه من الدولوميت فيما بين فراغات الحبيبات ومساميتها وذلك بعد الإحلال الدولوميتي ، وتتراوح نسب نظير الاكسجين في الدولوميت الإحلالي بين -6، . إلى +2، 1 جزء في الألف بينما نسب نظير الكربون تتراوح بين +8، . ر+. ،3 جزء في الألف . وتشير هذه النسب إلى أن عملية الدلمته قد تمت في مياه مختلطة سادت فيها المياه البحرية وتحت درجة حرارة منخفضة . وفي المرحلة الختامية ترسب كالسيت كتلي لاحم وأوضحت النسب النظائرية للاكسجين والكربون (-6، 9 أكسجين -18 ، -2 ، 4 كربون -13) به أنه قد ترسب في نطاق للمياه العذب

التركيب المعدني والجيوكيميائي لأصداف ذات المصرعين الحديثة من شاطئ البحر المتوسط لمصر

The stable isotopic (8 ^C and 8^O) and elemental (Sr and Mg) compositions are presented for marine mollusc Carditacea and Solenacea shells collected off the Mediterranean coast of Egypt. Based on shell microstructures and mineralogy, the bivalve shells are preserved in their original mineralogy and chemistry. The Sr and Mg concentrations of the bivalve shells have mean values of 1960 ppm and 226 ppm; respectively. The stable isotopic composition generally show high values of 818O and 8'3C. The 818O values range from +0.1 to -1.8%o PDB and most shells are highly enriched in 13C; averaging +2.5%c PDB. These elemental and isotopic signatures are similar to those of modern marine bivalves from other localities. The oxygen and carbon isotopic compositions, together with the calculated temperatures, suggest that the aragonitic bivalve shells were precipitated in isotopic equilibrium from warm marine waters.توضح هذه الدراسة تركيب النظائر الثابتة ( الكربون - 13، الأكسجين -18) وكذلك التركيب الكيميائي ( الاسترنشيوم والمغنسيوم ) لأصداف نوعين من الرخويات البحرية التي تم جمعها من شاطئ البحر المتوسط لمصر ، وقد أثبتت النتائج المبنية على دراسة التركيب النسيجي الدقيق وكذلك التركيب المعدني أن أصداف هذه المحاريات ظلت تحتفظ بتركيبها المعدني والكيميائي الأصلي دون تغير . وقد تبين أن القيم المتوسطة لتركيزات عنصري الاسترنشيوم والمغنسيوم في أصداف هذه المحاريات كانت 1960، 226 جزء في المليون . وعلى وجه العموم فإن التركيب النظائري لهذه الأصداف أظهر قيم مرتفعة لكل من الاكسجين - 18 والكربون - 13 . وقد وجد أن نسبة نظير الاكسجين - 18 في هذه الأصداف تتراوح من + 1 ، إلى - 1.8 في الألف في حين أن معظم الأصداف أظهرت تركيزاً عالياً في نسبة نظير الكربون - 13 بمتوسط +2.5 في الالف . وأن هذه النتائج التي تم التوصل اليها تتشابه مع النتائج المتاحة لنفس الأصداف الحديثة من مناطق أخرى . وتتضح من هذه الدراسة أن قيم نظائر الاكسجين والكربون وكذلك درجات الحرارة المحسوبة تدل على أن أصداف المحاريات ذات التركيب الأراجونيتي قد تم ترسيبها في اتزان نظائري من مياه بحرية دافئة

Mercury pollution in doha (Qatar) coastal environment

Surface water and sediment samples were collected from the Doha coastal area and analyzed for content of physico-chemical forms of mercury. Dissolved reactive Hg (2.9 ng L?1) represented 81.0% of the total dissolved Hg (3.5 ng L?1). Organic Hg (0.6 ng L?1) contributed only 5.0% of total Hg. Mercury showed a strong tendency to be associated with suspended matter in Doha coastal waters, as it represented about 73.0% of the total. Total Hg in bulk Doha surface sediments fluctuated between 0.14 and 1.75 ?g g?1 dry weight, with an average of 0.54 � 0.46 ?g g?1 dry weight. The sediment fraction past 63 ?m contained 0.73 ?0.60?g g?1 dry weight total Hg. Leachable and methyl Hg averaged 0.10 � 0.11 and 0.02 �0.03 ?g g?1 dry weight, respectively, in the <63-?m sediment fraction. There is a general trend for all Hg species determined in water and sediments to decrease seaward. The significantly elevated Hg levels at certain locations indicated that the main Hg sources to Doha coastal environment are leachate from the solid waste disposal site, the two harbors, and surface-water discharge.Scientific and Applied Research CenterWiley Online Librar