Wyniki wyszukiwania - BazTech

Ograniczanie wyników

Znaleziono wyników: 2

Liczba wyników na stronie

Wyniki wyszukiwania

Wyszukiwano:
w słowach kluczowych: Mesoproterozoic

Sortuj według:

Ogranicz wyniki do:

The Mesoproterozoic ‘seismite’ at Laiyuan (Hebei Province, E China) re-interpreted

Van Loon A. J.

Geologos

2014

Vol. 20, No. 2

139--146

A 1-million m3 breccia near Laiyuan (Hebei Province, E China) occurs as a block-like lithological unit between dolostones of the 1.55–1.45 Ga (Early Mesoproterozoic) Wumishan Formation. It has previously been interpreted as a seismite, but it appears not to fulfil any of the commonly accepted criteria that jointly are considered diagnostic for seismites. Its presence in a graben-like structure with almost vertical bounding fault planes rather indicates an origin as a (submarine) valley fill. As the valley originated by tectonic activity in the form of faulting, the breccia can be considered as a secondary effect of seismic activity, but it does not represent a seismite.

Czy istnieje mazurska, prawoskrętna strefa podatnego ścinania?

Cymerman Z.

Przegląd Geologiczny

2007

Vol. 55, nr 2

157-157, 167

Throughout SW Fennoscandia, numerous approximately W-E trending faults and ductile shear zones have recently been recognized. The regiona--scale zone of strike-slip displacements [Mazury lineament] with a dextral component was referred by many authors as apparently influenced by the distribution of ca. 1.6-1.4 Ga old "anorogenic" intrusions of the Mazury Complex [NE Poland]. However, new detailed structural and kinematics studies of drill-cores from 255 boreholes located throughout NE Poland and SW Lithuania [Lazdijai region] indicate that the Mazury Complex, the Suwałki Anorthosite Massif and surrounding lithotectonic domains share a common ductile thrusting deformation, calling into question the concept of a large-scale dextral shear zone and also the "anorogenic" origin hypothesis of the Mazury Complex. One important advance has been the accumulation of structural and kinematics information that allows assessment of the main orogenic transport direction commonly towards the SW, locally to the NE [e.g., in the eastern part of the Suwałki Anorthosite Massif]. This assessment has been coupled with the recognition of the role of major and numerous ductile shear zones within the western part of the East European Platform. In general, compressional deformation with ductile thrusting predominated in the western part of the East European Platform. Very probable strike of regional mylonitic foliation [S1] from almost 100 boreholes has been established, based on geophysical measurements of the curvature of borehole axis and a few tens oriented core samples [SW Lithuania]. It is assumed that the crystalline rocks of NE Poland and SW Lithuania [Lazdijai region] were subjected to similar ductile thrusting to transpressional deformation during the late Gothian [or newly defined Dano-Polonian] orogeny [ca. 1.5 Ga].