## 2 Geological Setting
### Lithology  
The geology of the area consists of Alpine (mainly Triassic to Late Jurassic limestones/dolomites, flysch, marbles, and ophiolites) and post-Alpine formations (silts, clays, conglomerates, and sandstones of Middle-Upper Miocene). In many places, they are covered by Quaternary alluvial sands and conglomerates of small consistency, as a result of the erosion of the aforementioned formations. More specifically:  
* The Alpine basement formations can be distinguished into two major groups, regarding their tectonic emplacement on the Cretan nappe pile [1]. They are members of the tectono-stratigraphic succession which builds the island of Crete as a stacked pile of 10 geetectonic units with a total thickness of about 10-12 km [33]. The upper part of the pile consists of five units (Pindos, Arvi, Miamou, Vatos, and Asteroussa) which are tectonically emplaced beneath the ophiolites, that is the uppermost nappe, whilst the lower four units (Mani, W. Crete, Arna, and Tripolis) comprise the basement of Crete [1; 33]. At the study area of easternmost MB, the Alpine basement outcrops are limited to the following rocks:
* Limestones and Dolomites (Mani Unit). Carbonate rocks consisting of thin-bedded crystalline marbles with layers of siltstones (L. Jurassic--L. Eocene). They appear heavily folded with isoclinal asymmetric folds.
* Limestones and Dolomites (Tripolis Unit). Intercalations of unbedded to thick-bedded neritic dark-colored and partially bituminous Limestones and Dolomites, with sparse appearances of evaporites.
* Flysch (Pindos Unit). It consists of heavily folded layers of Sandstones, Schists, and Conglomerates, with the characteristic appearance of large carbonate olistoliths that originated from inner units.
* Ophiolitic nappe. Limited appearance at the top of E. Asteroussa Mt, emplaced between the Flysch and the Viannos formation sediments as its basement rock.  
The entire nappe pile behaves homogenously till after the Middle Miocene, when the compressional, almost N-S-trending, orogenic stress field is converted into an extensional one due to the African plate slab roll-back [9; 34; 35; 36], which happened at the edge of the Aegean microplate [37]. Within this context, Crete is a large part of the Mid-Moocene Southern Aegean core complex exhundation that took place between 24 and 15 Ma [9] which hosts several supra-detachment depositional areas [3; 4], with MB being one of them.
* The Cretan nappe pile is segmented by many faults and covered by sedimentary formations representing different paleo-environments, as follows (from deeper to shallower):
* Viannos Formation (Mid. Miocene). Sandy/silty deposits of lacustrine origin, coexisting with alluvial conglomerates. The average thickness of the formation is about 400 m. Its outcrops may be found at most of the eastern MB margin,
either covering unconformably the basement rocks or in tectonic contact with them through ruptured fault zones.
* Skinias Formation. It is a transitional succession consisting of Middle Miocene salts, with a thickness of \(\sim\)200 m, yielding the sea intrusion within the MB area. At the area between Skinias and Martha villages, the Skinias salts were deposited in a deep (over 200 m) marine environment. The base of the deposits consists of Pelites, whereas layers of conglomerates and sand have been observed in the area close to Martha village.
* Ampelouzos Formation. It is deposited unconformably above both aforementioned formations. The lower part of the formation includes a variety of sedimentary, well-layered deposits, transitioning gradually from shallow to deeper (fan conglomerates to homogenous continental shelf sandstones). According to fossils found in the continental and shallow-marine deposits, the formation is dated as Middle to Upper Miocene [38].
* Alluvial deposits. Unconsolidated sands and conglomerates with pebbles originated from all the above formations, mainly along riverbeds.