## 2 Study Area Description
### Geological and Hydrogeological Information  
The Marvdasht Plain forms part of a large intermontane basin within the Zagros Mountain chain, which extends in a northwest-southeast direction. This basin resulted from the collision of the Arabian and Eurasian plates [36; 37; 38]. The study area lies within the crush zone of the main Zagros thrust. Tectonic processes, including faulting and folding, have shaped the region, producing fractured limestone units that serve as natural groundwater reservoirs. These units are mostly concealed beneath Quaternary alluvial deposits [39]. The plain is surrounded by several mountain ranges: the Zagros Mountains to the west and northwest, Kuh-e Rahmat to the east, Kuh-e Hossein to the northeast, and Kuh-e Tasuj to the southeast. These ranges consist of diverse rock types, including limestone, marl, shale, metamorphic rocks, and igneous intrusions [40]. The geology of the Marvdasht Plain, as depicted in Figure 2, encompasses formations spanning the Cretaceous to the Tertiary. These formations significantly influence the region's structural and hydrogeological characteristics. The Sarvak, Asmari, Jahrom, and Daryan formations constitute the primary bedrock aquifers. Composed of thick-bedded, sometimes dolomitized limestones, these formations have developed into major karst aquifers due to extensive fracturing and jointing. In contrast, the Gachsaran formation, consisting of marl, gypsum, and salt, exhibits low permeability and acts as an aquitard, impeding vertical water movement. Quaternary sediments, derived from surrounding sedimentary rocks, cover most of the study area. These sediments include loess, loess-like deposits, and alluvial materials ranging in texture from fine to coarse--gravel, sand, silt, and clay [41; 42]. Deposited by fluvial and lacustrine systems, these materials have created fertile soils that sustain the region's rich agricultural and cultural heritage. Notably, Cretaceous limestone formations, particularly the Sarvak Formation, function as key aquifer units, represented by \(K_{sr}^{l,m}\) layer in A-A+ and B-B+ geology sections (Figure 2). A confined aquifer system underlies the Marvdasht Plain, with Quaternary alluvium and fractured limestone forming the primary aquifers, while marl and shale serve as aquitards [43].  
trendline in the hydrograph, with the equation \(y=-0.0948x+1577.1\) (where x is time in months), quantifies this decline at a rate of roughly 0.0948 m per month or 1.154 m per year. This significant decline in groundwater level has led to the compaction of clay-rich layers, resulting in land subsidence across the Marvdash Plain [44, 45]. Precipitation data, shown as blue bars along the x-axis, reflect the semi-arid climate of Fars Province. Peaks occur during the wet season (November to March), with maximum monthly values reaching approximately 300 mm. Nevertheless, most months exhibit minimal or no precipitation, mainly during the dry season (April to October). The limited recharge from these sporadic events fails to offset the continuous groundwater withdrawal, as evidenced by the lack of significant groundwater level recovery following precipitation peaks. This imbalance underscores the unsustainable water management practices in the region. The hydrograph provides a temporal dimension to the spatial data in Figure 1a,b, quantifying the rate and extent of aquifer decline. It serves as a critical metric for this study, supporting the use of remote sensing and modeling to monitor and predict groundwater level trends, which are essential to understanding the geological and hydrogeological framework. Consequently, a comprehensive understanding of the geological and hydrogeological framework of the Marvdasht Plain is vital for devising strategies to mitigate land subsidence and preserve the region's historic landmarks.