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Messinian evaporites from the Mediterranean and Red Seas
Marine Geology, 26 ( 1 9 7 8 ) 7 1 - - 7 2 ©Elsevier Scientific Publishing Company, A m s t e r d a m - - P r i n t e d in The Netherlands
MESSINIAN EVAPORITES FROM THE M E D I T E R R A N E A N A N D RED SEAS
K E N N E T H J. HSU ~, P E T E R S T O F F E R S : and DAVID A. R O S S 3
~Geological Institute, ETH, Zurich (Switzerland) ~Laboratorium fiir Sedimentforschung, HeMelberg (F.R.G.) *Woods Hole Oceanographic Institution, Woods Hole, Mass. (U.S.A.) (Received March 28, 1977)
ABSTRACT Hsii, K.J., Stoffers, P. and Ross, D.A., 1978. Messinian evaporites from the Mediterranean and Red Seas. Mar. Geol., 26: 71--72. A p r o m i n e n t s u b b o t t o m reflector (M- in the Mediterranean and S- in the Red Sea) has been identified by deep sea drilling as the top o f an Upper Miocene evaporite formation. The Mediterranean evaporite minerals are d o l o m i t e , gypsum, anhydrite, halite, polyhalite, kainite, sulphoborite, possibly bishofite and lunebergite, a borate and p h o s p h a t e mineral. The Red Sea evaporite minerals include d o l o m i t e , magnesite, gypsum, anhydrite, halite, polyhalite, and possibly t a c h y h y d r i t e . Analcite and length-slow c h a l c e d o n y are present locally in both regions, p r o b a b l y as diagenetic minerals. The sedimentary structures of the evaporites from both regions indicate a genesis in sabkha environments. The b r o m i n e profiles of the halites are also typical of deposition in shallow brine-pools. On the o t h e r hand, the sediments i m m e d i a t e l y below and above the evaporite in the Mediterranean, and those i m m e d i a t e l y above the evaporite in the Red Sea are typically hemipelagic marls, containing deep-water b e n t h o n i c fossils. We believe, therefore, that the evaporites were deposited in pre-existing deep hasins, and that the evaporites, at least those from the intervals penetrated by deep sea drilling, were deposited after the basins were partially or wholly desiccated. Isotopic analyses of the carbonates and of the interstitial waters from the evaporites suggest considerable freshwater influx into the desiccating basins. That the Messinian basins were host to fresh or brackish water lakes is further proven by the occurrence of a Paratethys ostracod-fauna and an epiphytic diatom-flora in the upper levels o f the Mediterranean evaporites. While the Red Sea might have received its freshwater supply from African rivers, the eastern Mediterranean lac mer with its Cyprideis pannonica, might have been a part of the Paratethys, which was a great brackish water b o d y e x t e n d i n g from Vienna Basin to Aral Sea. The stratigraphy of the evaporites under the Red Sea is remarkably similar to that under central Ionian abyssal plain (Site 374). A dark gray, d o l o m i t i c marl (or m u d ) unit is present b e t w e e n an anhydrite--halite unit o f Late Messinian and a normal marine hemipelagic marl of Pliocene age. The d o l o m i t i c s e d i m e n t is largely unfossiliferous e x c e p t for some nannofossils (latest Miocene or earliest Pliocene) and it may represent a more euxinic, or m o r e basinal equivalent of Upper Messinian Cyprideis-bearing beds elsewhere (e.g. F l o r e n c e Ridge, Sites 375--376). The simultaneous occurrence of an evaporite by desiccation during the latest Miocene and the simultaneous submergence under normal marine waters during the earliest Pliocene suggest that the Mediterranean and the Red Sea Basins were parts of one and
72 t h e same h y d r o g r a p h i c s y s t e m . As the M e d i t e r r a n e a n is d e m o n s t r a b l y an Atlantic province during the Mio-Pliocene, we s u s p e c t that the Red Sea was n o t c o n n e c t e d with the Indian Ocean w h e n its evaporites were being f o r m e d . The Strait of Bab el M a n d e b was o p e n e d during a m o r e recent episode o f seafloor spreading. This event, t o g e t h e r with an isolation f r o m the M e d i t e r r a n e a n by the I s t h m u s o f Suez, r e n d e r e d the ICed Sea an a p p e n d i x of the Indian Ocean.
MESSINIAN EVAPORITES FROM THE M E D I T E R R A N E A N A N D RED SEAS
K E N N E T H J. HSU ~, P E T E R S T O F F E R S : and DAVID A. R O S S 3
~Geological Institute, ETH, Zurich (Switzerland) ~Laboratorium fiir Sedimentforschung, HeMelberg (F.R.G.) *Woods Hole Oceanographic Institution, Woods Hole, Mass. (U.S.A.) (Received March 28, 1977)
ABSTRACT Hsii, K.J., Stoffers, P. and Ross, D.A., 1978. Messinian evaporites from the Mediterranean and Red Seas. Mar. Geol., 26: 71--72. A p r o m i n e n t s u b b o t t o m reflector (M- in the Mediterranean and S- in the Red Sea) has been identified by deep sea drilling as the top o f an Upper Miocene evaporite formation. The Mediterranean evaporite minerals are d o l o m i t e , gypsum, anhydrite, halite, polyhalite, kainite, sulphoborite, possibly bishofite and lunebergite, a borate and p h o s p h a t e mineral. The Red Sea evaporite minerals include d o l o m i t e , magnesite, gypsum, anhydrite, halite, polyhalite, and possibly t a c h y h y d r i t e . Analcite and length-slow c h a l c e d o n y are present locally in both regions, p r o b a b l y as diagenetic minerals. The sedimentary structures of the evaporites from both regions indicate a genesis in sabkha environments. The b r o m i n e profiles of the halites are also typical of deposition in shallow brine-pools. On the o t h e r hand, the sediments i m m e d i a t e l y below and above the evaporite in the Mediterranean, and those i m m e d i a t e l y above the evaporite in the Red Sea are typically hemipelagic marls, containing deep-water b e n t h o n i c fossils. We believe, therefore, that the evaporites were deposited in pre-existing deep hasins, and that the evaporites, at least those from the intervals penetrated by deep sea drilling, were deposited after the basins were partially or wholly desiccated. Isotopic analyses of the carbonates and of the interstitial waters from the evaporites suggest considerable freshwater influx into the desiccating basins. That the Messinian basins were host to fresh or brackish water lakes is further proven by the occurrence of a Paratethys ostracod-fauna and an epiphytic diatom-flora in the upper levels o f the Mediterranean evaporites. While the Red Sea might have received its freshwater supply from African rivers, the eastern Mediterranean lac mer with its Cyprideis pannonica, might have been a part of the Paratethys, which was a great brackish water b o d y e x t e n d i n g from Vienna Basin to Aral Sea. The stratigraphy of the evaporites under the Red Sea is remarkably similar to that under central Ionian abyssal plain (Site 374). A dark gray, d o l o m i t i c marl (or m u d ) unit is present b e t w e e n an anhydrite--halite unit o f Late Messinian and a normal marine hemipelagic marl of Pliocene age. The d o l o m i t i c s e d i m e n t is largely unfossiliferous e x c e p t for some nannofossils (latest Miocene or earliest Pliocene) and it may represent a more euxinic, or m o r e basinal equivalent of Upper Messinian Cyprideis-bearing beds elsewhere (e.g. F l o r e n c e Ridge, Sites 375--376). The simultaneous occurrence of an evaporite by desiccation during the latest Miocene and the simultaneous submergence under normal marine waters during the earliest Pliocene suggest that the Mediterranean and the Red Sea Basins were parts of one and
72 t h e same h y d r o g r a p h i c s y s t e m . As the M e d i t e r r a n e a n is d e m o n s t r a b l y an Atlantic province during the Mio-Pliocene, we s u s p e c t that the Red Sea was n o t c o n n e c t e d with the Indian Ocean w h e n its evaporites were being f o r m e d . The Strait of Bab el M a n d e b was o p e n e d during a m o r e recent episode o f seafloor spreading. This event, t o g e t h e r with an isolation f r o m the M e d i t e r r a n e a n by the I s t h m u s o f Suez, r e n d e r e d the ICed Sea an a p p e n d i x of the Indian Ocean.