Rafael Riosmena Rodríguez

Rochas de praia (beachrocks) da Ilha do Cabo Frio, Arraial do Cabo: registro geológico ímpar da transição pleistoceno - holoceno no Estado do Rio de Janeiro

The Cabo Frio Island, Rio de Janeiro State, southeast Brazil shows four bodies of beachrocks, emerged up to +1.5 m and submerged down to - 4.5 m. These bodies are constituted of discontinuous strips, parallel to the coastline. Beachrock is beach sediment that has been cemented within the intertidal zone. Like the beach itself, it represents a transition between the marine and meteoric environments, where it is commonly elected by processes from each. Because beachrock is lithified within the intertidal zone and because it commonly forms in a few years, its potential as an indicator of past sea level is important. Four beachrocks samples were analyzed by polarizing microscope. This study indicated that carbonate elements that constitute most of the samples were at least partly incorporated within the intertidal zone. The adequate method for radiocarbon dating (total sample or cement) was decided according to these observations. The dates obtained from Cabo Frio island beachrocks indicate 4 separate sea level stands: the first one at about + 1.5 m around 13.000 BC, the second one at about 0.0 around 12.500 BC, the third at about - 3.0 m around 11.000 BC and finally the fourth sea level at about - 4.5 m around 10.000 BC. The results suggests that between 13.000 to 11.000 yr BP, a sea level fluctuation was around 6,0 m, corresponding probably to negative fluctuation of - 4.5 m and positive fluctuation of + 1.5 m. On the coast of Rio de Janeiro State, Brazil several relative sea level positions are recognized. The more important was the Malhada mash to the north area, a great marine transgression around 5.000 years B.C.

Approaches and Perspectives About Biodiesel and Oil Production Using Algae in Mexico

Oil extraction in Mexico started during the Aztec kingdom with the exploitation of the ground deposits better known as “chapopoteras.” It has several uses such as for religious ceremonies, cleaning teeth, and sealing for construction. In 1783, the Spaniard crown declared the mineral rights to use just with a formal notice, but as part of the adjustments occurred after the independence war, several perforations happened in the late nineteenth century, and the transformations of the laws in the country led to the development of private companies to exploit the underground resources found around the Gulf of Mexico, and the first foreign companies were developed (http://petroleo.colmex.mx/index.php/component/content/article/54). However, with the increment of oil production and the taxation of this activity by several Mexicans, a conflictive situation arose which was resolved with the nationalization of all foreign companies in 1938. After that period, the oil production increased in their volume and in the value hitting top values in the late 1970s and at the beginning of the twenty-first century. Oil and gas production represents the venue wherein the Mexican economy has developed over the last century (Gil-Valdivia and Chacon-Dominguez, 2008) in industrial, economic, monetary balance, and in many other political factors.