Seismic basement in Poland

Authors: Marek Grad Marcin Polkowski

Publish Date: 2015/09/10

Volume: 105, Issue: 4, Pages: 1199-1214

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Abstract

The area of contact between Precambrian and Phanerozoic Europe in Poland has complicated structure of sedimentary cover and basement The thinnest sedimentary cover in the MazuryBelarus anteclize is only 03–1 km thick increases to 7–8 km along the East European Craton margin and 9–12 km in the TransEuropean Suture Zone TESZ The Variscan domain is characterized by a 1 to 2kmthick sedimentary cover while the Carpathians are characterized by very thick sediments up to c 20 km The map of the basement depth is created by combining data from geological boreholes with a set of regional seismic refraction profiles These maps do not provide data about the basement depth in the central part of the TESZ and in the Carpathians Therefore the data set is supplemented by 32 models from deep seismic sounding profiles and a map of a highresistivity lowconductivity layer from magnetotelluric soundings identified as a basement All of these data provide knowledge about the basement depth and of Pwave seismic velocities of the crystalline and consolidated type of basement for the whole area of Poland Finally the differentiation of the basement depth and velocity is discussed with respect to geophysical fields and the tectonic division of the areaTectonic sketch of prePermian Central Europe in contact with the East European Platform Variscides and Alpine orogen The blue frame shows the location of the study area in Poland Compiled mainly from Pożaryski and Dembowski 1983 Ziegler 1990 Winchester et al 2002 Narkiewicz et al 2011 Cymerman 2007 and Skridlaitė et al 2006 ArdRhen M ArdennoRhenish Massif BT Baltic Terrane FSS Fennoscandia–Sarmatia Suture HCM Holy Cross Mountains MB Małopolska Block MLSZ MidLithuanian Suture Zone MSFTB MoravianSilesian FoldandThrust Belt PLT PolishLatvian Terrane PM Pomerania Massif RFH RingkobingFyn High STZ SorgenfreiTornquist Zone Thor S Thor Suture TTZ TeisseyreTornquist Zone USB Upper Silesian Block VA Voronezh Anteclise VDF Variscan Deformation FrontThe sedimentary cover of the EEC in northern Poland is rather thin being only 03–1 km thick in the region of the MazuryBelarus anteclize but increases southwestwards to 7–8 km along the EEC margin In the TESZ the sedimentary layer attains a thickness of up to 9–12 km The Variscan domain is characterized by a 1 to 2kmthick sedimentary cover while the Carpathians are characterized by very thick sediments of up to c 20 km eg Guterch and Grad 2006 For this reason the basement in the TESZ and in the Carpathians is not reached by boreholes so its depth is available only from geophysical investigations mostly from seismic profiling In particular seismic velocities in the basement could be used for discrimination between the crystalline and consolidated types of the crust According to Dadlez 2006 and Dadlez et al 2005 the crystalline crust is considered to consist of highly deformed metamorphic and igneous rocks characteristic of Precambrian platforms By contrast the consolidated crust is composed of highly deformed but not necessarily metamorphosed sedimentary and subordinate igneous rocks characteristic of the Paleozoic platform The aim of this paper is to find the geometry of the seismic basement its velocity as well as the relationship between the crystalline basement the consolidated basement and the sedimentary cover in PolandGeological and seismic cross sections trough of the TransEuropean Suture Zone TESZ in Poland between the East European Platform EEP and West European Platform WEP a Location map of seismic profiles b Geological cross section along line AA′ with two tectonic subdivisions by Karnkowski 2008 and Żelaźniewicz et al 2011 c d Seismic sections beneath profiles 1VI66 M7 and P4 Note basement velocity differentiation about 61 km/s for the EEP and about 58 km/s for the WEP Basement in the TESZ area is not reached by boreholes see dashed pink lines at depth of 5 km so its depth and velocity is available only from seismic profiles FSB ForeSudetic Block KP Synclinorium KościerzynaPuławy Synclinorium MPA MidPolish Anticlinorium NSS NorthSudetic Synclinorium SzM Synclinorium SzczecinMiechów Synclinorium WEP West European Platform WS Western Sudetes Compilation from Karnkowski 2008 Żelaźniewicz et al 2011 and Grad et al 1991 2003a bSeismic cross sections for profiles M7 1VI66 and P4 all close to line AA′ are shown in Fig 2c d The sedimentary cover along the geological cross section Fig 2b and seismic cross section along the P4 profile Fig 2d show similar sequences of layers including complicated Permian Zechstein salt diapirs and salt pillows in the TESZ Krzywiec 2006a b Mazur et al 2005 However the major structural features of the seismic profiles are the basement depth and its velocity differentiation c 61 km/s for the EEP and c 58 km/s for the WEP Grad et al 1991 2003a b Differentiation of the basement is also observed in the complicated pattern of the Bouguer anomalies the irregular pattern of the magnetic anomalies electromagnetic properties and the heat flow All of these observations will be discussed at the end of the paper together with the tectonic subdivisions of the area of PolandThe database for the basement depth and velocity in the area of Poland a Basement depth from boreholes limited to 45 km depth Małolepszy 2005 see text for more explanation white color shows area with no data b Depth of the seismic basement in northeastern Poland Skorupa 1974 and depth of the basement highconductivity layer from magnetotelluric investigations in Carpathians in southern Poland Stefaniuk and Klityński 2007 c Basement depth beneath seismic refraction profiles for each point along the profiles a mask of 20 km radius was used to plot the basement depth the white color shows an area with no refraction data d Data coverage from all sources colors correspond to a number of data sources available at a given location and the white color shows places with no data e Averaged and interpolated basement depth from all available sources f Interpolated Pwave velocity of the uppermost basement from seismic refraction profiles the dotted line ellipse shows the area of anomalous velocity anisotropy discussed in the text The data in the map c are from modern seismic refraction experiments/profiles POLONAISE’97 Guterch et al 1999 profile P1—Jansen et al 1999 profile P2—Janik et al 2002 profile P3—Środa and POLONAISE Working Group 1999 1999 profile P4—Grad et al 2003a b profile P5—Czuba et al 2001 CELEBRATION 2000 Guterch et al 2003 profiles CEL01 and CEL04—Środa et al 2006 profile CEL02—Malinowski et al 2005 profile CEL03—Janik et al 2005 profile CEL05—Grad et al 2006 profile CEL10—Grad et al 2009 profiles CEL06 CEL11 CEL12 CEL13 CEL14 CEL21 CEL22 CEL23—Janik et al 2009 SUDETES 2003 Grad et al 2003a b profile S01—Grad et al 2008 profiles S02 S03 S06—Majdański et al 2006 OTHRER profiles LT2 LT4 LT5—Grad et al 2005 profile LT7—Guterch et al 1994 profiles M7 M9—Grad et al 1991 profile TTZ—Grad et al 1999 profile PANCAKE—Starostenko et al 2013 profile 1VI66—Grad et al 1990The complete basement depth map of the East European Craton in northeastern Poland was created by Skorupa 1974 This study covered an area of the EEC where the thickness of sediments is only 03–1 km thick in the region of the MazuryBelarus anteclize mostly less than 4 km and reaches c 10 km on the edge of the East European Craton see Fig 3b NE Poland The study was based on data from geological boreholes and the set of regional seismic refraction profiles available at that time In our elaboration a corresponding mask for this map is calculated as having value 1 where data are available and value 0 elsewhere This map covers 421  of the area of PolandA second basement depth map was compiled based on geological boreholes data using maps from the geological atlas of horizontal cuttings Kotański 1997 Piotrowska et al 2005 Małolepszy 2005 Nita et al 2007 http//model3dpgigovpl/pages/miazszosc podlozehtm The compiled map was prepared down to 6 km depths but knowing that borehole surveying has a limited range due to the small amount of deep wells only depths down to 45 km are considered in this paper A proper mask for this map is calculated as having value 1 where data are available and the basement depth is shallower than 45 km and value 0 elsewhere This map Fig 3a covers 583  of the area of Poland

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