Geochemical Provenance of Clastic Sedimentary Rocks Case Study: Wadi Al-Ghar
DOHA MAHMOUD MOHAMMAD AWWAD
ضحى محمود محمد عواد
Sedimentary rocks are considered as a historical record of the different conditions that pass through the region and its composition may be inferred from the development of origin and tectonic setting. Sedimentary rocks are influenced by many factors that create sediments such as chemical weather, climate, and transport. To understand and define the sedimentation environment and its sources, it is important to study geochemical properties. The purpose of this study is to monitor the transport of sediments from one area to another due to surface runoff operations in wadi Al-Ghar area, amount of rain that falls on the area. This study was conducted by estimating the rainfall amounts, then studying the chemical and physical properties of the moving sediments. Where wadi Al-Ghar region is exposed to deep floods from the surrounding areas, the study area was varied in elevation in the range of (400–1000) meters, the slope for the running water was 0.02. These floods affect the geological formation and the arrangement of sand dunes, which are basically sediments are moving from upstream to downstream area. For the methodology we have 48 sediment and runoff samples were collected during two years (2017-2018). The process of collecting samples was in two stages according to Palestine climate wet season (April-May) and dry season (Oct-Nov). Samples point were specified (X,Y,Z) at different altitudes in depth, as it took sediment samples along the stream of the channel more than once to compare the results with each other. The study was divided into several sections: quantities (rainfall) of precipitation, chemical and physical properties of sediments that moved, Rare earth element, isotopes (δ18O, δ13 C), organic carbon and total Nitrogen of both sediments and runoff. Results revealed that the wadi divided into five zones based on the names used in that region: Ma’aza, Am-Gresh, Arab rashayda, wadi al-masyada, Confluence of all wadie’s and Downstream. Based on the geological layers exposed in the study area and depending on the ages in which they were formed, the sedimentary rocks in the study area are similar to a part of the sedimentary rocks that formed in the late Cretaceous period, especially the Cenomanian and Toronian periods. Which covers the Hebron Mountains, and this refers to the erosion factors that were exposed to it, which led to its transmission through surface runoff and then deposition in the form of sedimentary dunes in wadi Al-Ghar. Furthermore it ; the results showed that the sediments are presently moving in the same area, and only a small part is transport to the central regions due to the surrounding influences. It is transmitted through various erosion factors such as slope, soil composition, rocks, geological shape and the difficult environmental conditions that the area is exposed to. Also, the results of the trace elements and the main elements confirm that the type of sediments present is dolomite which contains a high percentage of the following elements (Ca, Mg, K, Na), while the REE results were very few> 0.01. This was attributed to the inability to transport the elements by runoff. Surface and lack of a source for high sedimentary masses. Each of the isotopes O18 ((-2.97_ -4.17), δC13 (-6.24_ -2.97) confirmed the presence of limestone in the sediments. However, the values of TOC and TIC and TNb differ between the samples that were taken due to the different sources and their diversity. On the other hand, it was important to study weathering factors on sediments to understand their effect. It was observed that the ratio of CIW and PIW had a positive and disallowed index of Al motion, as opposed to the proportion of WIP >100 which had a negative index and allowed Al to move. Based on the results, the recommendations are summarized to install a meteorological station to monitor climate change and to take samples of surface runoff during the period of flash flood, while maintaining flow data for continuous periods to monitor erosion and sediment transport in the valley and to collect rainwater to measure rainfall quantities and analyze its chemical and physical properties. In addition to taking samples of sediments for a longer period along the valley to determine its characteristics and modes of movement.