Oje de Liebre, Mexico

The region located south of Guerrero Negro, around the head of the Laguna Ojo de Liebre, Mexico, lies approximately halfway between the southern tip of the Baja California Peninsula and the U.S.-Mexico border and opens onto the Pacific Ocean. Formerly, in its whale hunting heyday, Lago Oje de Liebre was known as Scammon's Lagoon. The current name translates into English as "hare eye lagoon."

Laguna Ojo de Liebre is a large, shallow salt watery habitat that is up to 20 kilometres wide and from 5–12 metres deep. Relatively deep subtidal channels cut through the lagoon between its broad intertidal and supratidal \ flats. The climate is dry and warm (BWh); the annual temperature ranges from 18 °C and 22 °C. Yearly rainfall is variable from none to more than 200 mm. Along the Pacific coast, the lagoon edge is defined by coastal dunes ranging up to 12-15 metres high.

The lagoon lies within the Vizcaíno Biosphere Reserve UNESCO World Heritage Site and is also a Ramsar wetlands site. As such, it is an important habitat for the reproduction and wintering of the grey whale and harbour seal, as well as other marine mammals including the California sea lion, northern elephant seal and blue whale. Four species of endangered marine turtles reproduce there. It is an important refuge for waterfowl in the winter.

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Ojo di Liebre, Mexico

The town of Guerrero Negro was founded in 1957 when Daniel Ludwig built a salt works there to supply the demand of salt in the western United States. The salt mine was established by Ludwig around the Ojo de Liebre coastal lagoon to take advantage of its strong salinity. This company, called Exportadora de Sal, S.A., of C.V. ("Salt Exporters, Inc."), eventually became the largest single salt operation in the world, with a production of seven million tons of salt per year, exported to the main centers of consumption in the Pacific basin, especially Japan, Korea, the United States, Canada, Taiwan and New Zealand.  

The onshore northern region of Ojo di Liebre ("eye of the jack-rabbit") was once the most extensive natural sabkha complex in the North Americas but is now transformed into a vast expanse of halite-producing saline pans. Several smaller sabkhas remain nearby on both coasts of Baja California. The transformation from sabkhat to saltworks began in 1957 when a significant part of the natural sabkha north of Laguna Ojo de Liebre was converted in saline ponds suitable for solar concentration and crystallisation.

The border between the upper lagoon and the sabkha to the north is marked by outcrops and subcrops of low Holocene beach ridges, composed mainly of quartz, plagioclase, and hornblende, with varying amounts of carbonate shell fragments and oolites. Sands elsewhere in the lagoon contain pelletal apatite, but none are found at this beach. The beach ridge is breached by several tidal creeks, which are bordered by a carpet of Salicornia and Spartina that makes them show as dark patches in satellite imagery. 

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Detail of the former Ojo de Liebre sabkha, located south of Guerrero Negro, now converted to a series of halite-producing salt pans

Many daily tides and especially semi-monthly spring tides flood an area behind the northern beach ridges, dominated by black, rubbery mats of cyanobacteria and dunes. The cyanobacterial mats initially covered an area of about 100 km2 on the former sabkha. The mats entrain interstitial aragonite, high-magnesian calcite, dolomite, and gypsum. Beyond the algal mat area, the salt flats were once covered with a hard crust of gypsum and halite. These salt flats originally had an area of some 500 km2.

The lagoo ward portions of the sabkha area was flooded by most tides, with evaporation sufficient to produce a visible floating film of gypsum and halite crystals. The shoreward parts of the salt flats were beyond the reach of normal tides, but occasional storm surges with persistent onshore winds were able to drive a layer of lagoonal water to the farthest reaches of the flats. This intermittent flood, probably occurred one or more times a year, was documented by swash marks composed of shells, seaweed and other flotsam that wound across the flats. The resulting supratidal deposits of salt and gypsum varied from a few millimetres thick at its lagoonward edge to a maximum of 2.5 m. A wide-ranging survey in 1916 showed salt/gypsum bed thicknesses generally in the range of 10 to 20 cm. The mineralogy of the evaporite deposit in the former sabkha included; gypsum of various morphologies, halite, polyhalite, celestite, magnesite and bassanite. The salts were deposited as a succession of irregular stacked layers 0.2-2 cm thick, made up of light-coloured evaporite minerals alternating with darker layers of organic debris and windblown sand.

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Pan harvesting at Ojo di Liebr

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