## 4 Discussion  
Beachrock is generally cemented in the tidal zone with a large amount of aragonite, high-magnesium calcite (HMC), and low-magnesium calcite (LMC). Carbonate cementation in the marine environment forms acicular-radial and spacious types of cement texture, whereas the tidal zone cement is indicated by aragonite or HMC. Meniscus bridge cement indicate LMC composition [1; 6; 46; 48]. Beachrock found in Indonesia consisted of calcium, magnesium, sodium, and phosphorus element. However, according to the ICP-AES data, the composition is not similar to those of limestones and/or other beachrock which typically consists of silica and carbonate [34; 35]. Hence, some previous studies have suggested that bacterial metabolism is related to the precipitation of rocks [42; 49] and that the end products lower the thermodynamic boundary for cement nucleation and increases the rates of the physicochemical processes involved [42]. A technique for bio-cementation using microbial induced carbonate precipitation (MICP) for calcium carbonate precipitation could be biologically controlled or induced. Bacteria serve as a catalyst in urea hydrolysis through the generation of urease enzyme to form calcium carbonate cement [46; 50]. Specific cement types are recognized as (i) acicular, fibrous, and bladed fabrics; (ii) radial fibrous and fascicular-optic fabrics; (iii) micro-and cryptocrystalline fabrics; (iv) equant spar, syntaxial overgrowth fabrics, scalenohedral calcites, and poloidal fabrics; and (v) non-carbonates. These types indicate incipient early marine cementation leading to a reduction in pore-space in near-seafloor sediments [51]. Krakal-Sadranan Beaches happen to follow the same pattern, in which the meniscus cement solution is characterized by domination by crystalline aragonite and magnesium-calcite, which are soluble in water. A summary of the mineralogy and geochemical characteristics of the various beachrock samples from the study area, along with interpretation of the beachrock depositional environment and the sources of trace elements, are depicted in Table 4. The multistage mineralization products of the biota are also known as microbialites from marine activity. For example, successive stages of bioccentation have been described for _Pararodholbacter_ sp. and _Oceanobacillus profundus_, whereas ureolytic bacteria precipitate aragonite nanograins outside their cell walls and, later, the cell content is replaced by aragonite. The aragonite crystals that formed outside and inside the cell wall are different in shape and size [44; 52]. In the case of mineralized varieties, superficial crusts preserve, as well as complicate, the morphology of the organisms, whereas biomineralized fabrics within skeletal, molluscan, and some thrombolites probably retain clearer details. In this environment, interference of the organic process by algae and microbial activities may accelerate the process [32; 53; 54]. The extent of vadose and freshwater diagenetic features indicates that more ancient beachrock had occupied inland positions for a relatively long time. Commonly, precipitation is induced by micro-organisms, mostly ureolytic bacteria, and cyanobacteria. Micrite is a major, often dominant component of these deposits [55; 56; 57]. For the deposits themselves, the term \"microbialite\" is widely used. The drawback is that the word has a strong genetic connotation. It stands for autochthonous micrite as opposed to allochthonous micrite that was transported and deposited as fine-grained sediment [58]. Beachrock in tropical areas mostly generate from microbial controlled of carbonate precipitation, which is controlled by the sunlight, temperature, latitudinal zonation of skeletal production, nutrient, and salinity [57]. This is proven from the interpretation of geochemical ICP data (Table 4) which is salinity in the oxidative condition is controlled the sedimentary process, and also microbial activity such as algae (for photosynthesis), cyanobacteria, and ureolytic bacteria were found inside the beachrock.