Geochemical Characteristics of Deep Groundwater in the Northern Fossa Magna Region

Abstract

The deep ground water in the northern Fossa Magna region where thick formations in the Neogene and later periods are distributed is represented by Na·Cl type groundwater originating from fossil seawater.
The high-density Na-Cl type groundwater has risen to a shallow depth under the ground surface. Monitoring the electric conductivity of the groundwater could help identify the geological structures such as active faults.
The Cl concentration in strong salt springs that are mixed with little meteoric water decreases, and δ¹⁸O increases in formations of later geological periods. Measuring the Cl concentration and δ¹⁸O could therefore enable the estimation of the period of the fossil seawater from which the strong salt spring originates, and may be effective for determining the rock from which hot spring seepage occurs.