Isolation of ureolytic bacteria and geochemical analysis of beachrock from Krakal-Sadranan Beach (Yogyakarta, Indonesia) were conducted to determine natural sedimentary characteristics of the beachrock. The beachrock was also examined to determine the depositional conditions and distribution of rare earth elements. An increased concentration of total rare earth elements, both heavy rare earth elements (terbium, dysprosium, yttrium, holmium, erbium, thulium, ytterbium, and lutetium) and light rare earth elements (lanthanum, cesium, praseodymium, neodymium, samarium, europium, and gadolinium) signals that the beachrock deposition process happened under oxidative environmental conditions. This study proposes the novel use of ureolytic bacteria in a depositional environment for carbonate control of a sedimentary process for the development of artificial rock to mitigate coastal erosion. The resulting bacterial strains are highly homologous to the 16S rDNA nucleotide sequence of the species Oceanobacillus profundus, Vibrio maritimus, and Pseudoalteromonas tetradonis.

Typically, the mitigation of coastal erosion is achieved by amending surface conditions using materials, such as concrete. The objective of this study is to evaluate the feasibility of constructing artificial beachrocks using natural materials (e.g., microbes, sand, shell, pieces of coral, and seaweed, etc.) within a short time, and to propose the method as a novel strategy for coastal protection. Initially, a survey on resistivity and a multichannel analysis of seismic waves (MASW) were conducted along the coastal lines to characterize and elucidate the subsurface structure of existing beachrocks in the Southeast Yogyakarta coastal area, Krakal-Sadranan beach, Indonesia. The field survey on natural beachrocks suggested that both resistivity and shear wave velocity were higher in the deeper deposits compared to the underlying unconsolidated sand layer within a depth of approximately 1.5 m and covering an area of 210.496 m 2 for the α-section and 76.936 m 2 for the β-section of beachrock deposit. The results of the sand solidification test in the laboratory showed that treated sand achieved unconfined compressive strength of up to around 6 MPa, determined after a treatment period of 14 days under optimum conditions.

Beachrock is among the important features of tropical coastlines. It appears to have an anchoring effect on dynamic islands that provides protection from erosion. However, the origin of cement micritic peloidal remains uncertain. Petrographic analysis is a method used by many geologists to accurately identify specific aggregated minerals present in an area. It also helps to understand historical petrogenesis interpretations of a sedimentary rock formation and cementation process inside rock particles. In this study, petrographic analysis was used to identify the structure, texture, composition, and presence of minerals from beachrock samples collected from Okinawa, Japan and Sadranan beach, Yogyakarta, Indonesia. Field investigations and laboratory analysis (petrographic and geochemical measurements) were aimed at understanding the formation mechanism of natural fresh beachrock. Subsequently, laboratory-scale experiments on artificial beachrock were based on solidification tests and were conducted to use microbial-induced calcium carbonate precipitation (MICP) with Pararodhobacter and Ocenisphaera bacterium species to draw comparisons between natural beachrock and artificial beachrock. The cementation process based on petrographic analysis of thin sections has an assumption that the cement type and other added materials determine the strength of the material, and that the cement mineral occurring represents the sedimentary environment. The cement mechanism behavior of natural beachrock has potential in manufacturing artificial beachrock using the MICP method, an eco-friendly development method for coastal areas.

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The aim of the study was to gain more information about the structural changes during the dewatering reactions of the above compounds. The paper is focus on the low-temperature absorption of hopeite clay mineral, afterward the phases are examined for the dependence of temperature at different pressures. Hopeite shows signs of a phase transformation. Their use for the dental cement industry as a lubricant for cold-rolling mills is to be emphasized, such as coating with phosphate mineral or carbonaceous crystal. This is shown by the appearance of the new reflexes. The observed changes take place below the dewatering known from the literature. The phase change was investigated using a neutron scattering experiment. A temperature-pressure phase diagram of the dewatering could be set up in the range of 275 K to 380 K and 10-3 mBar to 103 mBar with the temperature-dependent powder diffractometer at different pressures and the temperature-dependent neutron scattering experiment. In this work, it has been proved that the dewatering of the hopeite is dependent on pressure and that the dewatering process of the hopeite is a reversible process.