Geology, Geochemical and Petrographic Studies of Lokoja Sandstone Facies: Implications on Source Area Weathering, Provenance and Tectonic Settings

Authors: Mu’awiya Baba Aminu*, Andrew C. Nanfa, Godwin Okumagbe Aigbadon, Simon Dalom Christopher, Idoko Eleojo Friday, Andarawus Yohanna, Abdulbariu Ibrahim, Sadiq Mohammed Salisu, Pam Dajack Dung and Francisco Soki Paca, Simon Tobias Received: 02 May 2023/Accepted 25 August 2023 The examination of the geology, petrographic and geochemical profiles of the Lokoja sandstone facies is the primary goal of this research. The objectives include carrying out geochemical analysis on the Lokoja sandstone facies, carrying out X-ray fluorescence (XRF) analysis within the Lokoja sandstone facies, carrying out X-ray diffraction (XRD) analysis within the Lokoja sandstone facies and the determination of the petrographic of the Lokoja sandstone facies. A few thin oolitic iron stones and coarse-grained cross-bedded sandstone make up the geology of the study area, along with pebbly clayey grit and sandstone. Rarely exposed has been identified as a basal conglomerate composed of well-rounded quartz pebbles embedded in a white clay matrix. ranging from 100 and 300 meters in thickness, depending on the relief of the Basement Complex floor beneath. The methods used in carrying out this project research include granulometric, geochemical, and petrographic analysis. The result from the granulometric analysis was used to construct the lithology log. The log helps to determine the paleo-environmental and depositional sequence of the study area. The XRD/XRF analysis shows Quartz and Orthoclase Feldspar, as the predominant mineral assemblage recommending a low weathering contour for the Lokoja sandstones. The mineralogical composition of sandstones was detected using XRD and XRF analyses. The XRD profile of the Lokoja Sandstone A which is situated around the Nataco area consists of the following mineral obtained during the XRD: quartz, orthoclase, muscovite, kaolinite, osumilite, illite, chlorite and garnet respectively with varying percentages. The major minerals obtained from the results were quartz (67%) and orthoclase feldspar (11%). Geochemical signatures of clastic sediments can be employed to interpret the provenance nature of the deposits. The Al2O3 /TiO2 for Lokoja sandstone, claystone and shale facies of Patti Formation are 52.43 wt %, 14.21 wt %, 10.02 wt % and 10.25 wt % equally. This proportionality suggests felsic source rock for the Lokoja Sandstone and intermediate source rock for the Patti sediments. The Geology (distribution), Provenance, Weathering, Tectonic context and redox proxy of the Lokoja Sandstone, Middle-Niger basin have been determined using integrated petrographic, granulometric and geochemical advent. Major elements geochemistry and their ratios affirmed that the Lokoja sandstone is predominantly mature lithic arenites including sub-greywacke and protoquartzites impact of felsic igneous provenances on the static basin

WHO Global Situational Alert System: a mixed methods multistage approach to identify country-level COVID-19 alerts

Background Globally, since 1 January 2020 and as of 24 January 2023, there have been over 664 million cases of COVID-19 and over 6.7 million deaths reported to WHO. WHO developed an evidence-based alert system, assessing public health risk on a weekly basis in 237 countries, territories and areas from May 2021 to June 2022. This aimed to facilitate the early identification of situations where healthcare capacity may become overstretched.Methods The process involved a three-stage mixed methods approach. In the first stage, future deaths were predicted from the time series of reported cases and deaths to produce an initial alert level. In the second stage, this alert level was adjusted by incorporating a range of contextual indicators and accounting for the quality of information available using a Bayes classifier. In the third stage, countries with an alert level of ‘High’ or above were added to an operational watchlist and assistance was deployed as needed.Results Since June 2021, the system has supported the release of more than US$27 million from WHO emergency funding, over 450 000 rapid antigen diagnostic testing kits and over 6000 oxygen concentrators. Retrospective evaluation indicated that the first two stages were needed to maximise sensitivity, where 44% (IQR 29%–67%) of weekly watchlist alerts would not have been identified using only reported cases and deaths. The alerts were timely and valid in most cases; however, this could only be assessed on a non-representative sample of countries with hospitalisation data available.Conclusions The system provided a standardised approach to monitor the pandemic at the country level by incorporating all available data on epidemiological analytics and contextual assessments. While this system was developed for COVID-19, a similar system could be used for future outbreaks and emergencies, with necessary adjustments to parameters and indicators