Jean-Yves Bigot

The effect of the Messinian Deep Stage on karst development around the Mediterranean Sea. Examples from Southern France

It is difficult to explain the position and behaviour of the main karst springs of southern France without calling on a drop in the water table below those encountered at the lowest levels of Pleistocene glacio-eustatic fluctuations. The principal karst features around the Mediterranean are probably inherited from the Messinian period (“Salinity crisis”) when sea level dropped dramatically due to the closing of the Straight of Gibraltar and desiccation of the Mediterranean Sea. Important deep karst systems were formed because the regional ground water dropped and the main valleys were entrenched as canyons. Sea level rise during the Pliocene caused sedimentation in the Messinian canyons and water, under a low hydraulic head, entered the upper cave levels. The powerful submarine spring of Port-Miou is located south of Marseille in a drowned canyon of the Calanques massif. The main water flow comes from a vertical shaft that extends to a depth of more than 147 m bsl. The close shelf margin comprises a submarine karst plateau cut by a deep canyon whose bottom reaches 1,000 m bsl. The canyon ends upstream in a pocket valley without relation to any important continental valley. This canyon was probably excavated by the underground paleoriver of Port-Miou during the Messinian Salinity Crisis. Currently, seawater mixes with karst water at depth. The crisis also affected inland karst aquifers. The famous spring of Fontaine de Vaucluse was explored by a ROV (remote observation vehicle) to a depth of 308 m, 224 m below current sea level. Flutes observed on the wall of the shaft indicate the spring was formerly an air-filled shaft connected to a deep underground river flowing towards a deep valley. Outcroppings and seismic data confirm the presence of deep paleo-valleys filled with Pliocene sediments in the current Rhône and Durance valleys. In the Ardèche, several vauclusian springs may also be related to the Messinian Rhône canyon, located at about 200 m below present sea level. A Pliocene base level rise resulted in horizontal dry cave levels. In the hinterland of Gulf of Lion, the Cévennes karst margin was drained toward the hydrologic window opened by the Messinian erosional surface on the continental shelf.

The association between bubble trails and folia: a morphological and sedimentary indicator of hypogenic speleogenesis by degassing, example from Adaouste Cave (Provence, France)

INTRODUCTION Bubble trails are small channels developed subaqueously in the walls of carbonate caves by corrosion by carbon dioxide bubbles. Folia are among the most curious and rarest calcite speleothems: these subaqueous calcite coatings cover overhanging walls and resemble inverted rimstone dams. Their origin is still debated and several hypotheses have been suggested, among which two main hypotheses are: deposits at the surface of water bodies (pools with oscillating water level) or subaqueous speleothems in thermal caves. In the Adaouste Cave, bubble trails and folia are intimately associated, which is a paradox involving both corrosion and deposition, respectively. This paper presents a detailed analysis of their morphology and spatial distribution that provides a better understanding of their origin and significance. Our observations of bubble trails and folia from

Hypogenic origin of Provalata Cave, Republic of Macedonia: a distinct case of successive thermal carbonic and sulfuric acid speleogenesis

temperature, which leads to a progressive increase in CaCO3 solubility, and also a drastic drop of solubility near the water table due to the loss of CO2. As a result a geochemical zone of carbonate dissolution and zone of carbonate precipitation appear (Dublyansky, 2000a). Where H2S rich waters mix with shallower oxygen rich waters, sulfuric acid forms at or near water table, which rapidly dissolves the carbonate rocks (Egemeier, 1981). This process is known as sulfuric INTRODUCTION

An Overview of the Hypogene Caves of Sicily

Karst in Sicily develops in both Messinian gypsum and Mesozoic or Tertiary limestone rocks. Caves are also found in the basalts of Mount Etna. Except for some rare cases, until recently most caves developed in limestone were considered to be of epigenetic origin. The discovery of gypsum in some of these caves, and especially detailed morphological studies, have allowed defining a hypogenic origin for a dozen of caves up to now. In some of these, the hypogenic evidences are very clear, while others remain in doubt because of the widespread presence of well-developed condensation-corrosion morphologies not necessarily related to hydrothermal fluids. This paper reports the present knowledge of hypogenic caves in the Island of Sicily.