Complex morphostructural passages in the East part of Balkan Peninsula

The Complex Morphostructural Passages are the first rare negative morphostructural units in the Late Quaternary (Late PleistoceneHolocene) Relief of the Balkan Peninsula East Part. They are composed by morphostructural passages, kettle morphostructures, morhostructural thresholds, river valley morphostructures and morphostructural gorges. The mentioned negative compound morphounits present the contemporary relicts from the post Early Pleistocene Orthoplain Denudation or Denudation-accumulative Plane. The Complex Morphostructural Passages participle together with the younger positive dome-like and mountain arched morphostructures in the contemporary relief building. ABSTRACT


Object and purpose of the investigation
The building of contemporary morphotectonic model of the east part of Balkan Peninsula need the sufficient detailed knowledge of the morphostructural pattern of the area. The article object is the generalized mobility characteristic elaboration of the first rare regional negative compound morphounits -the Complex Morphostructural Passages. They participle together with the younger positive dome-like and mountain arched morphostructures in the contemporary relief building.

Methodological basement of the study
The proposed regional mfrphostructural study is based on generally accepted contemporary and already well-grounded scientific mobility Plate tectonics presents for the construction of the upper parts of the Earth's crust from different by size and number oceanic and continental plates (Tzankov, 2013). They are found in complex temporal and spatial relationships by the action of endogenous geodynamic processes.
The investigation is conformity with the represented on a Table I methodological model:

Terminological notisis
The complex morphostructural passages are the most negative regional morphounits in the relief. They are the morphostructural antipodes of the synkinematic positive morphounits hills or mountain terrenes.
The complex morphostructural passages are composed by alternate consecutive orderly morphostructural passages or kettle morphostructures with morhostructural thresholds.
Those composite (complex) arranged morphounit form linear prolong relative cramped depression areas with block segmented (mosaic) internal pattern. It can be complicated with sinkinematic river valley morphostructures or morphostructural gorges. The complex moprphostructural passages end normally with kettle morphostructures.
The investigated negative morphostructural coincide very often with the first rare river valleys with longitudinal variabile morphology.
The principal role for the complex morphostructural passages internal pattern have the contemporary relicts from the post Early Pleistocene Orthoplain denudation or denudation-accumulative plane. It is marking the bottoms of the morphostructural passages, kettle morphostructures, river valley morphostructures and the morphostructural thresholds primary superficies (Fig. 1). The mentioned negative compound morphounits participle together with the younger positive dome-like and mountain arched morphostructures in the contemporary relief building.

Orohydrographic overview
The eastern part of the Balkan Peninsula includes the area to the east from the Timok, Southern Morava, Pchinya and Vardar Rivers (Fig 2). This area includes (from the north to the south) the following west-east in general oriented orographic units: southern part of the Lower Danube Plain (to the south from Lower Danube River), low mountain-hills Fore Balkan Zone, high and middle mountain Stara Planina (Balkan) Zone, Sub Balkan Kettle Range Zone, middle mountain Sredna Gora Zone, hills-low mountain Kraishte Zone, lowland and hills Upper Thracian Zone. middle mountain Bregalnitsa Zone, high mountain Rila-Pirin Mountain Range Zone, high and middle mountain Rhodope Zone, low and middle mountain Sakar-Strandzha Zone, high and middle mountain Belasitsa Zone, low land Western Thracian Zone and lower Thracian Zone (Fig. 2).
The varied, quickly and often space changed relief is one of the most important characteristics of the Balkan Peninsula observed part. It is on effect of the very active Quaternary endogenous processes.

Morphotectonic overview
The processes of the East Balkan Peninsula Relief forming are direct connected with the transcontinental collision between the Gondwana and New Europe Iontinental massifs (Fig. 3).       (Tzankov, Stoyanov, Spassov, 2004).

End of Early Oligocene -finish of Alpine Orogenesis
Late Oligocene-Middle Miocene -superficially tectonic "calm" and sicinematic deep crustal block destruction. Denudation of the Late Alpine Relief and orthoplan building. Late Miocene -deposition of potent continental (alluvial and alluvialproluvial) deposits of the braded rivers on the fragments of the older orthoplan superficias.

Building time
The modern morphotectonic investigations of the Balkan Peninsula East Part are constituted the relics from four Quaternary morphostructural generations (Table 5). The Complex Morphostructral Passages building is connected with the third and fourth morphogeneration -the time of the contemporary relief forming. The last one represents a mosaic combination between the new build positive dome like morphounits and the conserved between them negative morphostructures -the relics from the primary post Early Pleistocene Orthoplain. Its morphoforms form the Complex Morphostructral Passages Complex Morphostructral Passages. In this sense participle the mentioned compound negative morphostructures in the Balkan Peninsula East Part modern relief forming.

Regional morphostructure
The mosaic pattern of the eastern part of Balkan Peninsula (Tab. III and IV) was predetermined during the Neo Europe Continental Massif building (Fig. 3). The mosaic internal character of the Bulgarian Continental Microplate was formed in connection with the pre Early Pleistocene Orthoplain destruction during the regional processes of the transcontinental collision between Gondwana and Neo Europe (Fig. 4.2). The deep block destruction of the Earth Crust (in the deep block lithostructural layer -Fig 4.1) has limited the borders of the morphostructural zones, areas and some of the regions. Its internal patterns was and is formed from the composed by hay angular and listric faults regional fault net. The last one has limited the most little Earth superficial blocks in which are closed the single positive domelike morphostructures.
The mosaic pattern of the Balkan Peninsula eastern part supplement to the relics from the pre Late Pleistocene Orthoplain (Fig. 5) -planes, low planes complex morphostructural passages, isolated morphostructural kettles and others. The mentioned specifics of the mosaic pattern determine the highly varied and regional rapid changing character of the relief in the eastern part of the Balkan Peninsula. The Complex Morphostructral Passages are the first rare regional negative compound morphounits in the area. They unit the negative morphostructures -relics of the pre Late PLeistocne Orthoplain in different regions.
The regional disposition of the Complex Morphostructural Passages in the Balkan Peninsula East Part is presents on the Table  4. and Fig. 6. The investigated negative compaund morphounits are include in the separated morphostructural zones or they build the all zones -Sub Hemus Morphostructural zone, Upper Thracian Morphostructural zone. The sizes, spatial parameters, form, hypsometric position and internal pattern of the Complex Morphostructural Passages are very different. This circumstance confirms the fact, thath the mentioned compaund morphounits presnt relics from the destructed post Early Pleistocene Orthoplain.

Seismic overview
The seismic overview of the Balkan Peninsula East Part show, that the effects of the not so high (in comparison with the Balkan Peninsula West Part) seismic activity manifests only on the enclosure faults of some negative morphostructures from the Complex Morphostructural Passages (Fig. 7). The central part of this ngative morphoelements are seismic passiv. This circumstance confirms the fact that the bottoms of the negative morphostructures are fragments from the seismic passive post Early Pleistocene Orthoplain.

Conclusion
The Complex Morphostructural Passages are the first rare negative morphostructural units in the Balkan Peninsula East Part. They are compound constructed morphoelements from the relics of the post Early Pleistocene Orthoplain in the area. It destruction, respectively the positive dome-like morphostructures is controlled by the deep crustal processes of the transcontinental collision between Gonwana and Neo Europe in the Balkan Peninsuls Area. This endogen geodynamics predetermines the future reduction of the Complex Morphostructural Passages spatial dimensions on account of the enlargement of the areas of the positive morphostructures.