deformation bands frequently accompany major faults in porous sedimentary rocks ( e.g. aydin , 1978 ; antonellini et  al . several characteristic features of deformation bands allow a distinction from brittle fractures ( e.g. slip surfaces or joints ; aydin et  al . , 2006 ) . generally , they are tabular zones of distributed strain . accordingly they are wider but show a smaller offset than striated slip surfaces . compared to brittle fractures , deformation bands exhibit no displacement discontinuity across them but these attributes may influence fluid flow in groundwater and hydrocarbon reservoirs ( chuhan et  al . , 2002 ; sternlof et  al . , 2006 ; kolyukhin et  al . , commonly , deformation bands occur as single bands with a width up to a few millimeters or as strands of several bands up to a few centimeters or decimeters in total width ( fossen et  al . , 2007 ) . deformation bands can be classified according to their kinematic properties ( aydin et  al . , 2006 ) , as ( i ) shear , ( ii ) compaction , or ( iii ) dilation bands ; hybrids exist between these end members . shear bands are frequently accompanied by compaction ( i.e. pore space reduction ) , caused by grain rotation , grain sliding and/or grain fracturing ( e.g. aydin , 1978 ; antonellini et  al . early stages of shear bands can include a component of dilation , which has been identified in both theory ( bsulle , 2001 ; borja and aydin , 2004 ) and in the field ( du bernard et  al . , 2002 ) . additionally , deformation bands are classified according to the dominant deformation mechanism ( fossen et  al . , 2007 ) , which depends on grain size , shape , sorting , cementation , mineralogy and porosity of the host sediment , and on the stress conditions during the formation of the bands . if cementation or dissolution occurs preferentially along deformation bands , they are classified as cementation and solution bands . only few examples of cementation bands are reported in the literature ( e.g. antonellini et  al . , 1994b ; antonellini and aydin , 1994 ; parnell et al . , 2004 ; this study examines deformation bands in neogene sandstones of the vienna basin ( fig .  1 ) , a miocene pull - apart basin in the north - east of austria ( royden , 1985 ) . recent studies analyzed deformation bands in outcrops at the margin of this basin , revealing a great variety both in deformation mechanisms and kinematic properties in uncemented or cemented rocks of different lithological composition ( exner and grasemann , 2010 ; rath et  al . , 2011 ; exner and tschegg , 2012 ) . here , we present the first observation of deformation bands in the subsurface of the vienna basin . core samples were analyzed from the matzen field , one of the largest onshore hydrocarbon reservoirs in central europe . this area is thus one of the best studied parts of the vienna basin concerning its stratigraphical , lithological and structural content . the dominant fault system with conjugated normal faults indicates ( late ) miocene nw  se extension , and is well documented in numerous 2d and 3d seismic datasets ( hinsch et  al . , 2005 ) . however , deformation bands related to the larger faults have not been investigated so far . the collected microstructural and chemical data provide insight into the kinematic evolution and timing of the deformation bands relative to cementation of the sandstone , as well as changes in the mineralogy and porosity with respect to the surrounding rock . in addition , the findings characterize the influence of the deformation bands on the migration of hydrocarbons and on the reservoir quality . 1 ) is part of the neogene paratethys basin system and is located between the eastern alps and the western carpathians . the miocene , 200  km long and 60  km wide , rhombohedral pull - apart basin was formed along nne ssw trending strike - slip faults during the lateral extrusion of the eastern alps ( royden , 1985 ; ratschbacher et  al . , 1991 ; wagreich and schmid , 2002 ) . the evolution of the vienna basin can be divided into two major stages ( see also royden , 1985 ; decker et  al . , 2316.4  ma ) , the basin was formed as an e  w trending piggy - back basin developing on top of the active nw - directed alpine thrust belt ( hamilton et  al . , 2000 ) . during the middle and late miocene ( ca . 16.47.1  ma ) , thrusting was followed by lateral extrusion of crustal blocks east of the tauern window , and the basin evolved into a pull - apart basin bordered by sinistral strike - slip faults ( royden , 1985 ) . this change can be recognized in the depositional sequence of the vienna basin as a major regressive event at the boundary between early and middle miocene ( wagreich and schmid , 2002 ) ( fig . rapid subsidence is responsible for the accumulation of approximately 5500  m of sediments in the central part of the vienna basin ( hlzel et  al . , 2008 ) . the samples investigated in this study are from the central part of the vienna basin , within the matzen oil and gas field ( fig .  1 ) . in this part of the basin , the earliest deposits unconformably overlie the pre - neogene basement ( fig .  2 ) . the sedimentation can be characterized as lacustrine to brackish - littoral in the basal units ( bockfliess formation ) , followed by a lacustrine - terrestrial sequence ( gnserndorf formation ) to limnic - fluvial on top ( aderklaa formation ) . during the lower badenian , a fluvial succession ( aderklaa conglomerates ) these sediments were transported to the north by a braided river system and contain reworked triassic dolomite ( sauer et  al . , 1992 ) . this was followed by a marine transgression through a seaway connecting the basin with the mediterranean area to the south . during the end of the badenian ( ca . it is characterized by meandering channels and delta deposits and correlates with the final isolation of the paratethys from the mediterranean sea . 11.57.1  ma ) is characterized by a decrease in salinity , leading to lacustrine and fluvial deposits ( sauer et  al . , 1992 ) . the analyzed samples belong to the marine upper lagenidae zone which overlies the aderklaa conglomerate and directly underlies the main oil and gas bearing horizons of badenian age in the matzen field , with the 16th horizon ( 16th tortonian horizon or matzen sand ) being the main producing horizon ( fig . 2 ; fuchs and hamilton , 2006 ) . the matzen oil and gas field , located 30  km north - east of vienna ( fig .  1 ) , is one of the largest onshore hydrocarbon reservoirs of central and western europe and the main hydrocarbon accumulation of the vienna basin ( fuchs and hamilton , 2006 ) . since the discovery of the field in 1949 , the majority of the oil and gas reservoirs is located in the shallow - marine to fluvial clastic sedimentary series of middle and late miocene age . to date , about 1500 wells have been drilled , which produced about 90% of the established initial reserves of the entire matzen field ( fuchs and hamilton , 2006 ) . the acquisition of high - resolution 3d seismic data in the 1990 's promoted a series of new sedimentological and structural studies ( e.g. , hinsch et  al . , 2005 ; fuchs and hamilton , 2006 ; strauss et  al . , 2006 ; hlzel et  al . , detailed mapping of horizon and fault surfaces revealed a complex system of fault - bounded horsts and grabens . structurally , the matzen field can be divided into four different zones , ( i ) the matzen anticline , an elongated , ne  sw trending anticline , which is located in the central part of the field , ( ii ) the matzen fault zone , a pull - apart graben in the north bounded by sinsitral strike - slip faults , ( iii ) the bockfliess fault system in the west and ( iv ) the markgrafneusiedl normal fault zone in the south ( schroeckenfuchs , 1975 ; fuchs and hamilton , 2006 ) . the samples investigated in this study derive from cores taken from a depth between 1647.5  m and 1656.5  m in the central part of the matzen field within the matzen fault zone , where a temperature of 65  c was measured . deformation bands can be macroscopically recognized in the sandstones in several sections of the core . the thickness of individual bands ranges from 2 to 4  mm ; in some cores anastomosing strands of deformation band reach a combined thickness of up to 5  cm ( fig .  3 ) . due to the fact that the cores are broken into cm - dm long , discontinuous sections , the length of single bands can not be determined . some of the samples show extensive oil staining , which is in some samples restricted to one side of the bands . to determine the mineralogical composition and microstructural features of the deformation bands and the host material , the following analytical instruments at the department of geodynamics and sedimentology , and the department of lithospheric research at the university of vienna were used . sandstone samples were investigated with an optical microscope leica dm 4500p equipped with a digital color camera , leica dfd295 with 3 megapixels . cathodoluminescence ( cl ) images were acquired with a lumic hc5-lm microscope with an acceleration voltage set at 14  kv and a beam current of 57  ma . x - ray diffraction ( xrd ) analyses were made with a panalytical xpert pro diffractometer between 2 and 70 2 angle ( cu k radiation , 40  kv , 40  ma , step size 0.0167 , 5  s per step ) . five sample pairs ( deformation band and host rock of each core sample ) were powdered and analyzed . a scanning electron microscope ( sem , fei inspect s50 ) was used to study the morphology and the surface of two split samples . the backscatter electron detector ( bse ) and energy dispersive x - ray analysis ( edx ) were used to obtain high - resolution images and to characterize the chemical composition of the samples in thin sections . element maps were taken with a focus on elements si , fe , mg , ca and k. the images were analyzed with the program imagej to determine mineralogical composition , porosity and grain size distribution . thin sections were coated with carbon to avoid charging and achieve conductivity of the electron beam . the sandstone split samples used in the sem had a size of 0.5  cm    1  cm    0.5  cm and were coated with a thin gold layer . quantitative chemical analysis of detrital dolomite grains and dolomite cement was performed with a cameca sx100 electron microprobe . the beam current was set to 20  na and the voltage to 15  kv . quantitative spot analyses for fe , ca and mg content were performed using the wavelength - dispersive ( wdx ) spectrometer . samples for carbon and oxygen stable isotope analyses were taken with a handheld micro - drill and analyzed at the institute for earth sciences , university of graz . all samples were analyzed in triplicates ; sample powders were reacted with 100% phosphoric acid at 70  c with a thermo - finnigan kiel ii automated reaction system . the evolved co2 gas was measured with a thermo - finnigan delta plus isotope ratio mass spectrometer . the c and o values are corrected according to the nbs19 standard and reported in per mill (  ) relative to the v - pdb ( vienna - peedee belemnite ) standard . measurements of nbs-19 and an internal laboratory standard indicate a standard deviation of 0.01 for c and o . micro - computed tomography ( ct ) was performed on one core sample , using a viscom x8060 ndt x - ray ct scanner at the department of anthropology , university of vienna . in order to remove edge effects and enhance the contrast between the deformation bands and the host rock , the stack of image files was processes by mean filtering and shading corrections using the software imagej . in order to determine the kinematic evolution and porosity of the deformation bands , we analyzed lithological , diagenetic and microstructural features of the sampled material . the deformation bands can already macroscopically be distinguished from the host rock as dark anastomosing bands of lower porosity ( fig . thin section analyses of the host rock and the deformation bands identify the cause for this porosity reduction as micritic dolomite cement ( fig .  4 ) . detrital grains of quartz , feldspar and dolomite are weakly cemented by carbonate in the host rock ( fig . 4a and b ) , and completely embedded in fine grained dolomite cement with a bright orange luminescence under the cl microscope inside the deformation band ( fig . the investigated sandstones can be classified as litharenites ( after folk , 1968 , fig . 4a ) and are well - sorted with a grain size between 0.05  mm and 0.4  mm . all the analyzed samples show identical mineralogy , containing detrital grains of quartz , dolomite , and feldspar , with a slight variability between the individual host rock samples . the pore space in the host rock is partly cemented by dolomite , kaolinite and pyrite . however , a significant change in porosity and dolomite cement is observed between the host rock and the corresponding deformation band . the amount of pore space lies between 18 and 31% in the host rock and decreases significantly to 19% in the deformation bands ( fig . 5b ) , as determined from point counting . additionally , the relative content of dolomite is by a factor of 23 higher in the deformation bands . qualitative information of the mineralogical composition from x - ray diffraction patterns indicates no significant difference between the deformation band and the host rock in bulk samples ( fig . the peak intensities of the diffraction pattern suggest that the percentages of some minerals of the deformation bands vary relative to the host rock , e.g. the peaks for chlorite , muscovite and kaolinite are smaller in the deformation band than in the host rock . under the scanning electron microscope , dolomite cement growth on detrital quartz grains can be identified in an untreated split sample ( fig . the dolomite cement grains have a characteristic euhedral rhombohedral shape and are between 2 and 10  m in size . this procedure revealed that the surface of quartz grains is corroded by idiomorphic dolomite grains , leaving rhombic dissolution pits ( fig . quantitative measurements of the chemical composition of both detrital dolomite grains as well as the dolomite cement were performed with the electron microprobe . the dolomite cement shows a significantly higher fe concentration ( 1012  wt% feo ) compared to the detrital dolomite grains ( 02  wt% feo ) . some detrital dolomite grains reveal chemically zoned overgrowths of dolomite cement , with an increasing fe - content indicated by higher z - contrast intensities in the bse images ( fig . the stable carbon and oxygen isotopes of the host rock and the deformation band were measured to determine the origin of the carbonate cement . a consistent trend can be observed for the measured host rock  deformation band pairs , shifting the corresponding deformation band toward slightly heavier oxygen and lighter carbon isotopic compositions compared to the host rock ( fig . the c and o values of the host rock range between 2 and 0.5 for o and  + 0.5 and  + 3.5 for c , which correspond to typical marine values . the deformation bands show a variation between 0.5 and  + 0.9 for o and 1.5 and  + 0.6 for c . pyrite aggregates are abundant in some samples , occurring as spheroidal aggregates of up to 1.5  cm diameter within the host rock with at least some straight faces and subgrain boundaries ( figs . occasionally , these pyrite aggregates are located at the margin of deformation bands , where they partially replace the dolomite cement within the bands . kaolinite shows vermiform face - to - face stacks of pseudo - hexagonal plates , of approximately 10  m diameter ( fig . 7a ) , and is found predominately as pore - filling mineral within the host rock . small amounts of finer grained kaolinite were also identified within the deformation bands . in some samples ( e.g. sample 1651  m ) , late joints crosscutting the deformation bands already in the optical and cl microscope images , it is evident that the deformation bands from the matzen field are different from the typical cataclastic deformation bands described in quartz - rich sandstones ( e.g. eichhubl et  al . the grain supported fabric in the host rock is modified to a matrix supported fabric ( i.e. the dolomite cement ) in the deformation bands , where grains are smaller ( fig . however , the detrital grains within the deformation bands , mostly quartz , feldspar and some dolomite , do not show any signs of internal fracturing ( fig . perpendicular to some deformation bands , fractures cutting across both detrital grains and dolomite cement are observed ( fig . some few fractured grains , primarily quartz grains , can be recognized at the border to the host rock in bse images ( e.g. fig . the most significant difference between the deformation band and the host rock is the presence of up to 40% of dolomite in the deformation bands ( figs . peculiar microstructures can be observed within the pyrite aggregates at the rim of some deformation bands , where pyrite cement is dissolving and replacing the fine grained dolomite cement . the pyrite fills the space between silicate grains as a fine grained cement with irregular boundaries to the dolomite cement ( lower right of fig . the remaining detrital silicate grains are intensely fractured , but without contemporaneous or subsequent shearing of the grain fragments ; instead , the fragments are slightly dilated and filled by pyrite cement ( central part of fig . the grain size distribution within deformation bands and the host rock was analyzed from bse images and element maps , in order to identify potential grain size reduction within the deformation bands prior to cementation . for a reliable statistical analysis , quartz as the dominating mineral phase ( 4245% in the host rock ) was used for the grain size analyses . one of the investigated areas , at the margin of a deformation band ( fig .  10a ) , shows quartz grains as the brightest phase in a si - element map ( fig . 10b ) . from a set of si - element maps from a deformation band and an adjacent area in the host rock , the quartz grains 11a and b ) and the area of each grain was computed . as already evident in the binary image , 11c ) , resulting both in a decrease in size of the quartz grains ( ca . 150250  m in diameter ) , as well as in an increase in the amount of small grains ( < 25  m diameter ) . similar grain size reduction is qualitatively observed for the other detrital minerals , i.e. feldspar ( pale yellow phase in fig . additionally , the distribution of dolomite cement , detrital dolomite grains and porosity was analyzed in the element maps . the dolomite cement essentially covers the entire intergranular space within the deformation band ; but only few pores and grains within the host rock are cemented by a chemically identical dolomite ( compare fig . detrital dolomite grains can be observed both in host rock and deformation band , as more compact grains with high intensities in the element maps . the density contrast between the dolomite - cemented deformation bands , the pyrite and the host rock , is imaged in 3d in the ct data ( fig . the bands form a dense anastomosing network in sample 1651  m , well cemented bands are crosscut by vertical joints of some few mm to cm length and 12  mm aperture , oriented perpendicular to the bands . from the ct data , the distribution of pyrite cement preferably at the margin of the deformation bands , aligned parallel to the sedimentary layering , is also evident ( fig . the vermicular habit of the pore - filling kaolinite in the sandstone is typical for formation under early diagenetic conditions ( ketzer et  al . , 2003 ) . the kaolinite is mainly formed by alteration of detrital feldspar ( brosse et  al . , 2003 ) . the alteration of feldspar to kaolinite in sandstones can occur under a wide range of conditions : during subaerial exposure of the sandstones in humid climate , at shallow ( < 1  km ) burial depth by influx of meteoric water or at greater depths ( 24  km ) by interaction with acidic water from thermal maturation of organic matter ( marfil et  al . , 2003 ) . in the studied samples from the matzen field , meteoric water infiltration along dilation bands is the most likely cause for replacement of feldspar framework grains by vermicular kaolinite , since the petrographic relationships suggest an early formation of kaolinite prior to the precipitation of dolomite cement . during repeated marine regressions in the upper badenian ( fig .  2 ; kreutzer , 1992 ) , previously submarine areas were subaerially exposed and meteoric waters were able to percolate the highly permeable sediments . meteoric waters are commonly very dilute , of oxidizing nature , saturated with co2 and thus slightly acidic ( worden and morad , 2003 ) . since the fe - dolomite cements do not show any signs of dissolution , it is unlikely that most of the kaolinite formed during mesogenesis by circulation of organic acids and co2 produced during thermal maturation of organic matter . however , as some kaolinite is also precipitated within joints cutting across the dolomite - cemented deformation band and the successive pyrite cement , a late formation by this process may have occurred . fe - dolomite forms euhedral rhomboids of a few micrometer size which are loosely distributed in the host rock and very tightly packed in the deformation bands . this cement seems to post - date the formation of kaolinite , as concluded from the identification of kaolinite both in the host rock and the deformation bands in xrd - patterns ( fig . stable isotope analyses comparing the host sandstone to the deformation bands show a consistent shift of the c/o ratios toward heavier oxygen and lighter carbon isotope ratios in all samples of the deformation bands ( fig . 8) . considering the origin of this fe - dolomite cement , either a local or an external source for the ca- , mg- and fe- ions is possible . on the one hand , 815% ) in the sandstones , and dissolution and re - precipitation of detrital dolomite could have been an internal source for the dolomite cement . however , the fe - content of the detrital dolomite grains is about 10% lower than of the cement , and the observed detrital dolomite grains do not show dissolution , but are overgrown by fe - rich dolomite . thus , this observation together with the oxygen isotope analyses suggests that the fe - dolomite is rather precipitated from a fluid derived from an external source . one possibility is that fluid from the underground of the vienna basin was transmitted along normal faults . as shown in experimental studies ( wong et  al . , 1997 ) , 100  mpa ) is initially associated with dilation and some cataclasis ; under natural conditions , these processes have been identified at even lower confining pressure around 5  mpa ( antonellini et  al . , 1994b ) . these zones of higher permeability may provide pathways for fluid flow and subsequently precipitation of dolomite cement . 500  m ) the studied well belongs to the alpine flysch nappes which comprise sandstones , marls and shales of upper cretaceous to eocene age . below the southern part of the matzen field , the pre - neogene basement is composed of units of the calcareous alps , containing significant amounts of dolomites ( e.g. hauptdolomit , sauer et  al . , 1992 ) . fluids derived from both pre - neogene basement units are considered as a potential source for fe - dolomite cement ( schroeckenfuchs , 1975 ) . alternatively , mass transfer from either the alpine flysch nappes or jurassic autochthonous mudrocks below the alpine thrust units , which are regarded as one of the main source rocks for hydrocarbons in the vienna basin ( kreutzer , 1992 ) , may have provided ions necessary for dolomite cement ( evans et  al . , 1998 ) . the diagenetic transformation from smectite to illite in mudrocks releases water and provides ca , mg , and fe - ions ( hower et  al . , 1976 ; boles and franks , 1979 ) , which may then form carbonates or fe - rich chlorites ( meunier , 2005 ) , depending on the co2 partial pressure . spheroidal pyrite aggregates ranging from a few mm to 1.5  cm in diameter are present in the host rock and along the bands , where pyrite partly dissolves the dolomite cement . this pyrite is clearly a pore - filling cement and thus formed during diagenesis after the precipitation of the dolomite cement . from its occurrence at the margin of the deformation bands ( fig . 12b ) and the horizontal alignment along the bands , we assume that the pyrite was precipitated from a sulfide - rich fluid which was retained by the deformation bands and reacted with available iron provided by fe - dolomite or clay minerals , or present in the pore fluid ( smith - enos and kyle , 2002 ) . either the underlying dolomite units ( hauptdolomit in the nappes of the northern calcareous alps ) or the autochthonous jurassic marls may have supplied the matzen sand with this sour gas ( h2s ; kreutzer , 1992 ) . from the petrographic relationships between the individual components of the sandstones , it is possible to deduce a diagenetic sequence for the host rock and the deformation bands . during an initial phase feldspar kaolinite can be found both within the host rock and the deformation bands , indicating an early formation of this clay mineral . subsequently , the corrosion of detrital quartz and most probably also other detrital minerals by diagenetic fluids and the precipitation of fe - dolomite cement occurs preferentially within the deformation bands and only subordinately in the host rock . notably , the solubility of quartz is high at high ph values , while carbonates dissolve at low ph . thus , at intermediate ph , both minerals are equally soluble , and already slight variations in ph might favor the precipitation of one of them ( blatt et  al . , 1980 ) . authigenic pyrite aggregates are later formed as idiomorphic grains in open pores in the host rock , or partially replacing dolomite cement at the margin of the deformation bands . in addition , a late formation of kaolinite , which is limited to vertical joints crosscutting the deformation bands or large pores within the host rock , can be observed . the deformation bands from the matzen field can already be characterized macroscopically by a reduction of porosity , which is due to a preferred precipitation of fe - dolomite cement within the bands . in addition we observe a significant reduction of the grain size of quartz relative to the host rock , as larger grains are fragmented into smaller , generally more angular grains ( fig . the corrosion of quartz by the dolomite cement may additionally reduce the grain size of quartz . however , the dolomite cement is not affected by the cataclastic grain size reduction , but coats and partly dissolves the fragmented quartz grains . it can thus be assumed that this cataclastic process occurred in the initial stages of the formation of the deformation bands prior to their cementation . moreover , the minus - cement porosity ( i.e. the sum of the present porosity and the initially open pore space now filled with dolomite cement ) within the deformation bands comprises a larger area fraction ( 4660% ; fig . ( 2002 ) in the first field observation of dilation bands , they report minus cement porosities of 38% in the host sediment and 45% in the dilation band , but do not observe significant cataclasis . 7b ) may have additionally contributed to the high values of minus cement porosity observed here , which documents that an excess of pore space and thus higher permeability within the deformation bands must have existed prior to the precipitation of the cement . , 1997 ) , we conclude that the deformation bands initiated as cataclastic dilation bands under low burial conditions , creating zones of high permeability , where fe- and mg - rich carbonate fluids could migrate and eventually precipitate preferentially at the fresh surfaces of cataclastic grain fragments . additionally , the precipitation of dolomite cement may have led to additional grain size reduction , similar to what is now observed in the pyrite cement adjacent to deformation bands ( fig . 7b ) , which was probably accompanied by ongoing shearing and fluid infiltration along the bands during dolomite precipitation . illustrating this process of deformation band formation in the matzen field , we assume that the original sedimentary fabric ( fig . 13a ) was deformed in an initial phase of shearing and dilation ( fig . 13c ) , and consequently provided space for precipitation of fe - bearing carbonate fluids . the dolomite cementation in the deformation bands makes them impermeable for migrating sulfide - rich fluids ( fig . 13d ) , forcing the precipitation of pyrite at the margin of the bands ( fig . in a final stage , vertical joints cut across the bands , which are now partly filled by late kaolinite ( fig . deformation bands , especially those characterized by compaction associated with cataclastic grain size reduction , may act as barriers for fluid flow across their width and conduits along their length ( antonellini and aydin , 1994 ; sternlof et  al . , in contrast , dilation within the deformation bands provides pathways for fluid migration ( du bernard et  al . , 2002 ; bense et  al . , 2003 ; sample et  al . , 2006 ) , which may in turn promote the precipitation of cements in these zones . these observations by earlier studies are in accordance with the deformation bands studied the matzen field , where an initial increase in porosity and permeability leads to the preferred cementation of the bands by fe - rich dolomite . the retention of pyrite cement at the margin of the deformation bands ( fig . 12b ) documents that , during a later stage , the cementation bands acted as barriers to fluid flow . since some of the studied core samples show a different degree of hydrocarbon staining at either side of the deformation bands , we suggest that also the hydrocarbon charging postdates the precipitation of the dolomite cement . alternatively , if hydrocarbon migration occurred prior to the formation of such cementation bands , these structures may create compartments in the reservoir and thereby deteriorate the production performance ( hesthammer and fossen , 2001 ; parnell et  al . , 2004 ) , which is in fact also the case in the compartmentalized area of the matzen fault zone ( personal communication p. strauss ) . from field examples , it has been suggested that joints cutting across deformation bands may decrease their barrier effect ( tindall , 2006 ) . however , the joints crosscutting the deformation bands described here may not have a significant effect on a permeability increase , since they are restricted to some few , well cemented bands and show a small aperture ( 12  mm ) and restricted length ( 12  cm ) . nevertheless , they might be more abundant and also of greater importance in other areas of the matzen field , where e.g. clusters of deformation bands occur . sandstone samples were taken from a well core in the matzen hydrocarbon field , central vienna basin , austria . the sandstones are litharenites and mainly composed of quartz , feldspar and detrital dolomite , with angular to subrounded , well - sorted grains , cemented by a fe - rich dolomite ( ca the samples contain numerous deformation bands , which can macroscopically be identified as 14  mm wide , mostly anastomosing zones of low porosity . the deformation bands are characterized by a decrease in porosity to 29% , in contrast to the surrounding rock with 2031.5% porosity . the reason for the decrease in porosity is the preferred precipitation of fe - rich dolomite cement within the deformation bands . additionally , the grain size of detrital grains is reduced relative to the host rock by grain fracturing and spalling . chemical composition and carbon and oxygen isotope ratios indicate that the dolomite cement does not originate from a meteoric source , like the detrital dolomite grains of the host rock , but presumably from hydrothermal , fe- and mg- rich fluids . pyrite cement is observed abundantly at the margin of the bands , partially dissolving the fe - dolomite cement . as a conceptual model for the development of these deformation bands , we assume that an initial phase of dilation and shear localization , associated with some minor cataclastic fracturing of grains , resulted first in an increase of porosity . subsequently , the high porosity band served as a high permeability pipeline during cementation of the rock by a fe - rich dolomite . preferred precipitation of this fe - dolomite within the band resulted in a reduction of porosity . these cementation bands then acted as barriers to fluid flow across them , as indicated by the presence of pyrite cement at the margin of the bands .
in this study we analyzed five core samples from a hydrocarbon reservoir , the matzen field in the vienna basin ( austria ) . 
 deformation bands occur as single bands or as strands of several bands . 
 in contrast to most published examples of deformation bands in terrigeneous sandstones , the reduction of porosity is predominantly caused by the precipitation of fe - rich dolomite cement within the bands , and only subordinately by cataclasis of detrital grains . 
 the chemical composition of this dolomite cement ( 1012  wt% feo ) differs from detrital dolomite grains in the host rock ( < 2  wt% feo ) . 
 this observation in combination with stable isotope data suggests that the cement is not derived from the detrital grains , but precipitated from a fluid from an external , non - meteoric source . after an initial increase of porosity by dilation , disaggregation and fragmentation of detrital grains , a fe - rich carbonate fluid crystallized within the bands , thereby reducing the porosity relative to the host sediment . 
 the retention of pyrite cement by these cementation bands as well as the different degree of oil staining on either side of the bands demonstrate that these cementation bands act as effective barriers to the migration of fluids and should be considered in reservoir models .