Explosive volcanism of the Atlantic and adjoin continental varios geodinamic zones

Eroshenko D.V., Kharin G.S.

Atlantic Branch of P.P.Shirshov Institute of Oceanology RAS, Kaliningrad, Russian

kharin@atlas.baltnet.ru

 

According to initial reports DSDP, ODP, IODP  data pattern composed of layers of volcanic ash in the sediments of the Cenozoic for different regions of the Atlantic Ocean, including the Norwegian-Greenland, the Caribbean and the Mediterranean Sea (Fig. 1).All over the Atlantic Ocean were analyzed about 220 deep drilling wells, 86 of them met pyroclastics varying degree of change. Note that the choice of regions is defined as the presence of representative wells deep ocean drilling,and the presence of a fixed core of these wells layers of volcanic ash, which are the results of land explosions. Such layers reliably distinguished in core documentation. They usually are confirmed and while watching smears (smear-slides) under a microscope, that is a compulsory element in the study of cores on board. More in-depth study of volkanoclastik included the analysis of mineral and chemical compositions, presence of rare and rare earth elements. Less studied the isotopic composition. In this report we present data on the distribution of layers of volcanic ash that: 1 - identify the period of explosive volcanism, 2 - to compare these periods in different regions of the Atlantic Ocean, 3 - to analyze the manifestations of explosive volcanism in different geodynamic zones of the Atlantic and adjacent continental margins.

It should be noted that there is some incompleteness of the data, because: 1 - boring sometimes conducted without coring, 2 - presence of hiatuses in sedimentogenesis and erosion of individual horizons creates a "white band" in the distribution of volcanic ash; 3 - different parts of Atlantic have different degree of scrutiny for the presence of explosive products of volcanism in sedimentary cover. Elimination of the incompleteness of the data we have tried the method of generalized section through the data is not one (usually the most complete on the contents of layers of ash), and the most representative wells in regions with the highest number drilled the stratigraphic horizons. The greatest number of wells marked the layers of ash, there is in the Norwegian-Greenland and the Caribbean Basins, the regions Canary Islands, Cape Verde Islands and the Mediterranean Sea. In these regions the pyroclastics have been studied (Kharin, 1993, 2000, Kharin, Eroshenko, 2001, Kharin, Eroshenko, 2010, Eroshenko, 1999, Eroshenko, 2009). According to other volcanic regions of the Atlantic is much less data, but they can also be used in comparison with the aforementioned.

The distribution of layers of pyroclastic material in the Norwegian-Greenland and the Caribbean regions characterized by the most complete set of the entire section Cenozoic (Fig. 2). In the Mediterranean region and Central-East Atlantic (CEA) is found only in the upper part of the section. Pyroclastics in the Norwegian-Greenland region and CVA it relates to activities plume volcanoes, and in the Caribbean and the Mediterranean - with the volcanoes of island arcs and subduction zones. For all these four sections are uneven distribution of intercalations pyroclastics. Distinguished the period reach by these layers. For the Norwegian-Greenland and the Caribbean Basins, they are: 1 - in the late Paleocene and early Eocene, 2 - Early and Middle Miocene, 2 - in the Pliocene and Pleistocene.  The same provision is the highest number of layers of pyroclastics have sections of the Pleistocene in the Mediterranean Sea. In regions of the Sierra Grande and Rio Grande, Cape Verde Islands and the Canary Islands and Walwis Ridge available data confirm the presence of late-and Early Eocene epoch of explosive volcanism.

The selected regions of the Atlantic, including Mediterranean, Caribbean, Norwegian and Greenland Sea by the intensity and composition of products explosions Cenozoic volcanism the geodynamic environments are divided into the following main types:

 1 - Iceland plume type (Norwegian-Greenland Basin and western North Atlantic); 2 - Canary plume type (Central-East Atlantic, Serra Leone, Cape Verde Rises), 3 - plume type of Tristan da Cunha (Rise Rio Grande, Walvis Ridge), 4 - Central American subduction and the Lesser Antilles island arc type (Caribbean Basin, Western Central Atlantic), 5 - subduction (clash the Mediterranean (Alpine), type (Mediterranean Sea).

For pyroclastic of the volcanic of the island arcs and subduction zones with close (almost synchronous) aged planned a small "advance" in time periods of maximum sediment compared with pyroclastic volcanic plume. This may indicate that the latter depends on the subduction slabs descend into the depths of the mantle.

Reference

Kharin G.S. Magmatism and formation of the lithosphere of the Atlantic Ocean. M.: Nauka. 1993. 256 p. (in Russian).

Kharings G.S. Magmatic Pulses of the Iceland Plume. Petrology. 2000, V. 8, N 2. P. 115-130.

Kharin G.S., Eroshenko D.V. History eruptive magmatism Caribbean region // Petrology. 2001, v. 9, N 6.  P. 623-638.

Kharin G.S., Eroshenko D.V. The evolution of explosive volcanism Norwegian-Greenland basin // Volcanology and Seismology. 2010 (in press).

Eroshenko D.V. The distribution of pyroclastic deposits in the Mediterranean Sea // Oceanology, 1999, Volume 39, N 6, P. 938-945.

Eroshenko D.V. Distribution and composition vulkanoklastiki in sedimentary cover of the Central Atlantic and the Mediterranean Sea. Abstract. , 2009 (PhD thesis) (in Russian).

 

Fig.1. Distribution of sites with pyroclastic material on the regions of the Atlantic. I - Norwegian-Greenland Basin (s.s. 916-919, 407-409, 336, 352, 403, 404, 552-556), II - Caribbean Basin (s.s. 998-1000, 537, 671-674), III - The Mediterranean region (s.s. 974 , 963-974, 650-656), Central-Eastern Atlantic Ocean: IV - Serra Leone (s.s. 13, 367, 661), V - on the Cape Verde Islands (s.s. 368, 659, 12), VI - Canary Islands (s.s. 953, 369);

 

Fig. 2. Distribution of the pyroclastic material in the stratigraphic sections in different regions of the Atlantic. 1 - layers of ash, 2 - change of ash, 3 – no drilling intervals. I-VIII - the studied regions of the Atlantic (see Fig. 1).