Petromagnetic and paleomagnetic characterization deposits at Mesozoic/Cenozoic boundary: The Tetritskaro section (Georgia)

Petromagnetic and magnetostratigraphic characteristics are obtained for the Tetritskaro section. The boundary layer at the Mesozoic/Cenozoic (K/T) boundary is fixed primarily by an abrupt rise in the paramagnetic magnetization (total Fe concentration) and, to a lesser degree, by an increase in the concentration of such magnetic minerals as goethite, hemoilmenite, and magnetite. The along-section distribution of titanomagnetite of volcanic origin and metallic iron of cosmic origin does not correlate with the K/T boundary and lithologic properties of the sediments. The boundary of the Mesozoic and Cenozoic geological eras lies within the reversed polarity chron C29r and is marked by an abrupt rise in the geomagnetic field paleointensity and an instability of paleomagnetic directions, rather than by a polarity change. The accumulation time of the boundary clay layer is about 1.5-2 kyr, while abrupt changes in the paleointensity and direction of the geomagnetic field encompass 30-40 kyr. Such long occurrence intervals of the events in question cannot be related to a short-term impact phenomenon. © Pleiades Publishing, Ltd. 2009

Petromagnetic and paleomagnetic characterization deposits at Mesozoic/Cenozoic boundary: The Tetritskaro section (Georgia)

Petromagnetic and magnetostratigraphic characteristics are obtained for the Tetritskaro section. The boundary layer at the Mesozoic/Cenozoic (K/T) boundary is fixed primarily by an abrupt rise in the paramagnetic magnetization (total Fe concentration) and, to a lesser degree, by an increase in the concentration of such magnetic minerals as goethite, hemoilmenite, and magnetite. The along-section distribution of titanomagnetite of volcanic origin and metallic iron of cosmic origin does not correlate with the K/T boundary and lithologic properties of the sediments. The boundary of the Mesozoic and Cenozoic geological eras lies within the reversed polarity chron C29r and is marked by an abrupt rise in the geomagnetic field paleointensity and an instability of paleomagnetic directions, rather than by a polarity change. The accumulation time of the boundary clay layer is about 1.5-2 kyr, while abrupt changes in the paleointensity and direction of the geomagnetic field encompass 30-40 kyr. Such long occurrence intervals of the events in question cannot be related to a short-term impact phenomenon. © Pleiades Publishing, Ltd. 2009

Petromagnetic and paleomagnetic characterization deposits at Mesozoic/Cenozoic boundary: The Tetritskaro section (Georgia)

Petromagnetic and magnetostratigraphic characteristics are obtained for the Tetritskaro section. The boundary layer at the Mesozoic/Cenozoic (K/T) boundary is fixed primarily by an abrupt rise in the paramagnetic magnetization (total Fe concentration) and, to a lesser degree, by an increase in the concentration of such magnetic minerals as goethite, hemoilmenite, and magnetite. The along-section distribution of titanomagnetite of volcanic origin and metallic iron of cosmic origin does not correlate with the K/T boundary and lithologic properties of the sediments. The boundary of the Mesozoic and Cenozoic geological eras lies within the reversed polarity chron C29r and is marked by an abrupt rise in the geomagnetic field paleointensity and an instability of paleomagnetic directions, rather than by a polarity change. The accumulation time of the boundary clay layer is about 1.5-2 kyr, while abrupt changes in the paleointensity and direction of the geomagnetic field encompass 30-40 kyr. Such long occurrence intervals of the events in question cannot be related to a short-term impact phenomenon. © Pleiades Publishing, Ltd. 2009

Petromagnetic and paleomagnetic characterization deposits at Mesozoic/Cenozoic boundary: The Tetritskaro section (Georgia)

Petromagnetic and magnetostratigraphic characteristics are obtained for the Tetritskaro section. The boundary layer at the Mesozoic/Cenozoic (K/T) boundary is fixed primarily by an abrupt rise in the paramagnetic magnetization (total Fe concentration) and, to a lesser degree, by an increase in the concentration of such magnetic minerals as goethite, hemoilmenite, and magnetite. The along-section distribution of titanomagnetite of volcanic origin and metallic iron of cosmic origin does not correlate with the K/T boundary and lithologic properties of the sediments. The boundary of the Mesozoic and Cenozoic geological eras lies within the reversed polarity chron C29r and is marked by an abrupt rise in the geomagnetic field paleointensity and an instability of paleomagnetic directions, rather than by a polarity change. The accumulation time of the boundary clay layer is about 1.5-2 kyr, while abrupt changes in the paleointensity and direction of the geomagnetic field encompass 30-40 kyr. Such long occurrence intervals of the events in question cannot be related to a short-term impact phenomenon. © Pleiades Publishing, Ltd. 2009

Karst map of Georgia (Caucasus region) scale: 1:1,500,000

Karst landscapes develop in soluble rocks, such as carbonates and evaporates, but also in various types of rocks that develop pseudokarst features. The main aim of this work is to introduce a new karst map of Georgia (scale: 1:1,500,000) presenting karst and pseudokarst features, which occupy about 17.9% (12,454 km2) of the entire territory of the country and include over 1500 known caves. We distinguish two types of karst features—karst (developed in carbonate rocks) and pseudokarst, and also five subtypes, mainly based on their lithology. About 10.2% (7120 km2) of the country is occupied by karst (carbonate rocks), and about 7.7% (5334 km2) of the country is occupied by pseudokarst features. This karst map of Georgia will provide important assistance to local and foreign researchers interested in studying Georgian karst features

Genetic Diversity and Domestication History in Pyrus

International audienc

Botany and taxonomy of pear

Pear belongs to the Rosaceae family as most of the cultivated fruit trees. It is the second fruit tree crop in terms of production after apple. Its production has increased these last decades to reach a world production of more than 27 megatons for almost 1,600,000 ha. Pears have been cultivated in Europe and in Asia for more than 5,000 years. Of all known and reported pear species and interspecific hybrids, five are mainly cultivated. These include the European pear, Pyrus communis, and the Asian pears P. pyrifolia, P. ×bretschneideri, P. ussuriensis, and P. sinkiangensis. Fruits of European pears are elongated and have a full-bodied texture, while those of Asian pears are round and have a sandy texture. The Pyrus genus belongs to the Amygdaloideae subfamily and the Malinae tribe, and consists of about 75 to 80 species and interspecific hybrid species. As several hybridizations are observed among Pyrus species, this renders the distinction among some pear species rather difficult. The origin of the Pyrus genus dates back to the Oligocene Epoch, about 33.35 to 25.23 Mya. It is a genus of mainly deciduous trees and shrubs spread throughout temperate Eurasia, reaching the Atlas Mountains in North Africa, and extending to Japan and South China. Pyrus species produce generally simple leaves alternately arranged. Leaves are glossy green on some species, densely silvery-hairy in some others. Pyrus flowers are white, borne in corymbs on short spurs or lateral branchlets, and are composed of five sepals, five petals, numerous stamens, and usually a five-locular ovary with free styles. The Pyrus fruit is a pseudo-fruit composed of the receptacle or the calyx tube, greatly dilated, enclosing the true fruit, and consisting of five cartilaginous carpels, known as the core. Morphological characters of the leaf, fruit, and calyx are commonly used to differentiate among Pyrus species. There are thousands of pear cultivars over the world with wide diversity for fruit shape, taste, and texture. In this chapter, we have focused on the description of cultivated Pyrus species and on some of the main cultivated cultivars