Ap Pli Ca Tion of Geoelectrical Pro Fil Ing in the De Lin Ea Tion of Shal Low Periglacial Struc Tures on the Drohiczyn Pla Teau

Studia Quaternaria, vol. 31, no. 2 (2014): 73–81.

DOI: 10.2478/squa-2014-0007

APPLI CA TION OF GEOELECTRICAL PROFIL ING IN THE DELIN EA TION OF SHAL LOW PERIGLACIAL STRUCTURES ON THE DROHICZYN PLA TEAU

Rados³aw Mieszkowski1, Jan Dzier¿ek1, Dominik Stañczuk2 1 Faculty of Geol ogy, Uni ver sity of War saw, ¯wirki i Wigury 93, 02-089 Warsaw, Po land; e-mails: [email protected]; [email protected] 2 Polish Geolog i cal Insti tute – Na tional Re search Insti tute; Rakowiecka 4, 00-975 Warsaw, Po land; e-mail: [email protected]

Ab stract The pa per de scribes the re sults of geoelectrical sounding ap pli ca tion for the delin ea tion of periglacial struc tures in Wierzchuca Nagórna within the Drohiczyn Pla teau (eastern Poland). The method re cords the vari a tion of ap par ent re - sistiv ity of depos its along a se lected hori zontal direc tion. The sur vey uti lizes a distinct geoelectrical contrast between gla cial till and struc tures com posed of sand that have been rec og nized ear lier in the gravel pit wall. The studies have been con ducted in direct hin ter land of the gravel pit. Rect an gular and con cen tric ar rays were ap plied in the survey. The re sults have been pre sented as graphs and re sistance distri bu tion maps. The ob tained geo log i cal im age is not com - plete, al though it shows an ori ented course of the larg est lin ea ments and traces of a net work with a small mesh size (1.5–2 m). The recog nized pattern of struc tures points to harsh cli matic con di tions dur ing their for mation. Gen eral ori - en ta tion of the struc tures cor re sponds to the ba sic el e ments of the con tem po rary land scape in the area (slope, val ley axes). Geoelectrical sounding using the rectan gu lar array gave better results than in the concen tric array, whereas intro duc tion of brine into the system did not en hance the res o lu tion of the read ings. The pre sented re sistance distri bu tion maps with a charac ter is tic rhythm of varia tions may serve as a benchmark for recog niz ing periglacial structures in areas with out ex po sures.

Key words: east ern Po land, Pleis to cene, periglacial struc tures, palaeo ge ogra phy, geoelectrical pro fil ing

Manuscript received 13 May 2014, accepted 5 November 2014

2p PRIN CI PLES OF GEOELECTRICAL K = æ 1 1 1 1 ö PRO FIL ING ç - - + ÷ ç r r r r ÷ Geoelectrical pro fil ing re fers to the re cord of ap par ent è AM BM AN BN ø re sis tiv ity vari a tions of dif fer ent lithologies along a se lected hor i zon tal di rec tion (pro file). The se lected elec trode spac ing where: A, B – cur rent elec trodes, allows to regis ter the magni tudes at certain depths, thus to M, N – poten tial elec trodes, conclude on the course of geolog i cal structures below the rAM; rBM; rAM; rAN; rBM – dis tances be tween the elec trodes; sur face. Di rect magni tudes that are measured are: the trans- DV – measured poten tial [mV]; mitted cur rent in the supply ing cir cuit, the po ten tial in the I – transmit ted current [mA]. measur ing circuit and the dimen sions of the entire measur ing The K co effi cient re mains un changed during the survey, sys tem (Fajklewicz, 1972; Stenzel and Szymanko, 1973). be cause AB and MN dis tances are con stant. The method is Tran si tion from these mag ni tudes to ap par ent re sis tiv ity r is par tic u larly ef fec tive for me dia with highly di verse geoelec- expressed by the follow ing equation: trical proper ties (Fig. 1). The main assets of such survey are: its non-inva sive charac ter, low cost, and rela tively high reso - DV lution of the measure ments. Geoelectrical profil ing has been r = K I first applied to recog nize the pattern of pseudomorphs after frost wedges for the SW part of the Drohiczyn Pla teau where K is the geomet ri cal fac tor ex pressed as: (Mieszkowski and Porze¿yñski, 2004, 2006). The geolog i cal 74 R. MIESZKOWSKI et al.

Fig. 1. Scheme of a non-symmet ric measure ment ar ray. struc ture of the sub-surface ho rizons in the area assured good nu merous fis sures and veins filled with sand and gravel, condi tions to test the method. occa sion ally with thin hori zons of sandy mud. The sand struc tures ter minate in the till or in the sand-gravel ho ri zon GEOMORPHOLOGICAL AND GEO LOG I CAL beneath. Their forma tion is connected with the ac tivity of CHAR AC TER IS TICS OF THE SW PART Pleisto cene frost pro cesses within the per ma frost (Dzier¿ek and Stañczuk, 2006). The contrac tion fissures were pri marily OF THE DROHICZYN PLA TEAU filled with ice. After per mafrost deg ra da tion the ice was re - The south-western part of the Drohiczyn Plateau is placed by sand and gravel, and the structures attained the bounded by the Bug River Valley (Podlasie Bug Gorge), form of pseudomorphs after ice wedges. Some fissures could which in this area rap idly changes di rection from WNW to be filled with sand al ready in periglacial con di tions, re sult ing NNW (Fig. 2). The levelled surface of this part of the plateau in the forma tion of a pri mary filling (Murton et al., 2000; lies at 135–150 m a.s.l. The bot tom of the Bug Val ley is lo- Dzier¿ek and Stañczuk, 2006). cated at 105–110 m a.s.l. The erosional slope of the plateau is high and steep and is best observed in the Drohiczyn escarp - GEO LOG I CAL RE CORD OF PERIGLACIAL ment. Straight valleys with gentle slopes, running almost per- STRUC TURES IN THE WIERZCHUCA pen dic u larly to the Bug Val ley, are a char ac ter is tic el e ment NAGÓRNA GRAVEL PIT WALL of the landscape. The dom inat ing ori enta tions of the valley axes are close to W–E and NNW–SSE; this fact has been The phenom e non of the Wierzchuca Nagórna site is the taken into account in the palaeogeographic recon struc tion of presence of at least 51 pseudomorphs after ice wedges in an the area (Dzier¿ek, 2009). over 150 m long gravel pit wall (Fig. 3). High den sity of the The main hori zon in the topmost part of the geolog i cal struc tures (every 1.7 m) may reflect harsh clima tic con di tions suc ces sion in the Drohiczyn Pla teau is gla cial till, one to sev - exist ing during their forma tion (Maizels, 1986; Mackay, eral meters thick, occa sion ally cov ered with a thin hori zon of 1993; Barry and Gan, 2011). The pseudomorphs are gener - sands with gravels. The till derives from the Wartanian Gla- ally about 1 m long, although shorter structures, 0.6-0.8 m ciation (Marks, 2005; Marks and Pavlovskaja, 2004; Nity- long, are also present. The width of the upper parts of the choruk, et al. 2008a, b), at present referred to the Wartanian pseudomorphs varies within 0.2–0.5 m, however, in some Stadial (Lindner and Marks, 2012). Below the till occur grav- cases it reaches even 1 m. Some struc tures at tain a typ ical els and sands that are over 4 m thick (Dzier¿ek and Stañczuk, wedge shape, although narrow veins and wide shafts with 2006). The geo logi cal set ting of the Drohiczyn Plateau is verti cal walls have also been noted (Washburn, 1973; Jahn, well vis ible in the walls of the gravel pit at Wierzchuca 1977; French, 2007). The record of periglacial frost pro- Nagórna (Fig. 3). Soil is under lain by silty sands with con- cesses is also evi denced by: the verti cal distri bu tion of peb- centra tions of gravel. Between 0.3 and 0.5 m lies the top of bles in the upper part of the glacial till, the convex top of the brown till with a thickness of up to 1.5 m. The till contains till between the pseudomorphs, a blurred sed imen tary struc- AP PLI CA TION OF GEOELECTRICAL PRO FIL ING 75

Fig. 2. Lo ca tion of the study area on a geo log i cal map (Nitychoruk, et al. 2008a).

Fig. 3. Pseudomorphs after ice wedges in the gravel pit wall at Wierzchuca Nagórna (modi fied from Dzier¿ek and Stañczuk, 2006). ture of the surface hori zons and the presence of pebble con- pla teau top. Re con struc tion of its char ac ter, in clud ing: sha- centra tions (frost segre ga tion) close to the pseudomorph top pes of the polygons, mesh size, network gener a tions and boundaries (Dzier¿ek and Stañczuk 2006). priv i leged fis sure ori en ta tions, is of palaeogeographic sig nif- Shapes of the pseudomorphs and their distri bu tion in the icance. It allows conclud ing not only on the proper ties of past gravel pit wall point to a polyg o nal network devel oped on the climate, but also, for exam ple, on the exis tence of natu ral 76 R. MIESZKOWSKI et al.

Fig. 4. Distri bu tion of lines of geoelectrical sound ing in a rect an gu lar ar ray and con cen tric ar ray.

morphological or geo log i cal es carp ments. Typ i cally, such lized at sev eral meters from the gravel pit escarp ment. Fifty- es carp ments are re corded by the priv i leged ori en ta tion of the seven shal low geo logi cal drillings were made along the line contrac tion fissures in the soil (the main gener a tion of the fis- of the first lon gi tu di nal pro file. Ad di tion ally, sev eral con trol- sures), to which the smaller fissures are adjusted (Jahn, 1970, ling drillings were made within the rect an gu lar ar ray. This al - 1977; French, 2007). Simi lar cases can be observed in contem - lowed cor re lat ing the geoelectrical in ter pre ta tion with the po rary periglacial ar eas. Anal y sis of the pi o neer ing ap pli ca - li thol ogy, and due to the close vi cinity of the wall – in ter pre- tion of geoelectrical sound ing is presented below with the use tation of the orien ta tion of structures visi ble in the expo sure. of earlier palaeogeographic anal ysis (Dzier¿ek, 2009). The cal cu lated re sis tiv ity val ues are pre sented in charts, where hor i zon tal co or di nates re fer to the lo cal iza tion of the RESULTS OF GEOELECTRICAL STUD IES mea sure ment points and ver ti cal co or di nates rep re sent the IN A RECT ANGU LAR ARRAY AND THEIR mea sured val ues of ap par ent re sis tiv ity cor re spond ing to the centre of sys tem 0. Inter sec tion of points in the coor di nate IN TER PRE TA TION sys tem forms the lines of the re sis tiv ity profiles (Fig. 5). In the survey area described above, the top of the till is in A series of control ling manual drillings have been made dis tinct geoelectrical con trast with re gard to the in fill ing sed - on the flat surface in the hinter land of the gravel pit escarp - i ments. The re sis tiv ity of till is at 30–80 Wm, whereas that of ment. Cor re la tion of the ap par ent re sis tiv ity mea sure ments sand and gravel exceeds 150 Wm. This complex is covered with the lithological sec tions ob tained from the drillings in di - by a thin (0.6–0.8 m) layer of silty sands with gravel admix - cate: 1) increased appar ent resis tiv ity when sands and gravels ture; it has an iden tical in flu ence on the measure ments and were drilled; and 2) de creased ap par ent re sis tiv ity in the case thus may be omitted in the inter pre ta tions. Such condi tions of till. This knowledge was applied in the inter pre ta tion of the o ret i cally al low for the rec og ni tion of the hor i zon tal oc- the remain ing profiles. Distinct posi tive peaks in the charts currence of tills and sands in the pseudomorphs directly be- (Fig. 5) can be com bined with the presence of increased low the sur face. thicknesses of sands (over 1 m) or thin ho rizons of grav els At first, a rectan gu lar array, non-symmet ric with infin - (about a dozen cm) in the site. The presence of an over 50 ity, was applied (Mieszkowski and Porze¿yñski 2004). The cm-thick hori zon of sands and a few cm-thick hori zon of spacing of the electrodes supply ing A0 was 1 m, with the sec- gravel should also not be excluded. However, for the as- ond supply ing electrode (B) located at a signif i cant distance sumed goal this fact does not cause signif i cant differ ences, from the survey profile (Fig. 1). The measur ing electrodes because in both cases it points to the occur rence of a sand- M0 and N0 were spaced at 0.3 m. The spacing was 1 m for gravel pseudomorph in the gla cial till. The pres ence of sec- both the lon gi tu di nal and trans verse pro files. Ad van tages of tions with lower appar ent resis tiv ity values in the survey pro- this array include the engage ment of a lower number of em - files can be inter preted as the shallowly lying top of glacial ployees (3 persons) and a short survey time. Measure ments till (i.e. area without pseudomorphs). However, the shape of were conducted along 7 longi tu di nal profiles and 17 trans- the charts does not depend only on the prop erties of the sur- verse profiles (Fig. 4). The first longi tu di nal pro file was loca- veyed me dium. Ap par ent re sis tiv ity val ues mea sured along AP PLI CA TION OF GEOELECTRICAL PRO FIL ING 77

Fig. 5. Dis tri bu tion of ap par ent re sis tiv ity along lon gi tu di nal (A) and trans verse (B) pro files (Mieszkowski and Porze¿yñski, 2004).

pro file I are dis tinctly lower in re la tion to the other mea sure - cen tre “0” by several tens of centi metres. Shallow manual ments (even by 50%). This proba bly results from the distur - drillings have al lowed to state that this translocation was bance in the measure ment sys tem caused by the nearby com monly at 30 cm towards elec trode A with regard to the gravel pit wall. “Thinning” of the elec tric cur rent lines takes sys tem cen tre “0”. place in the hin ter land of the gravel pit escarp ment, i.e. mea- Presen ta tion of the survey measure ments in the charts surement by compen sa tor gives decreased values of DV has allowed observ ing and explain ing anoma lies in the first (which is numer a tor in the equation presented above), and course of measure ments. However, due to the al leged goal of thus lower appar ent resis tiv ity val ues. It could also be noted the sur vey, such pre sen ta tion of ap par ent re sis tiv ity vari a tion that the ap pli ca tion of a non-symmet ric ar ray, i.e. elec trode B in the sub-surface part of the study area is not suffi cient. It is moving to infin ity, has caused the translocation of the system dif fi cult to cor re late with the sur face ar range ment of re sis tiv - 78 R. MIESZKOWSKI et al.

Fig. 6. Maps of ap par ent re sistiv ity distri bu tion in a rect an gu lar ar ray in 2D (left) and 3D (right) (modi fied from Mieszkowski and Porze¿yñski, 2004).

ity vari abil ity. There fore, the re sults are pre sented in a plan the study area may result from the geolog i cal setting or from within a mea sur ing grid as 2D maps of re sis tiv ity vari a tion errors in data inter po la tion in the termi nal part of the survey (Fig. 6). Accord ing to the argu ments pointed out above, the profile. In turn, the several meters-broad high resis tiv ity band influ ence of the gravel pit escarp ment has been included by with irreg u lar margins in the lower left on the map of the study mul ti ply ing the val ues of ap par ent re sis tiv ity in lon gi tu di nal area proba bly reflects the orien ta tion of the broad sand infill - profile I by coef fi cient 2, in longi tu di nal profile VII by 1, and ing. Such in ter pre ta tion is con firmed by ob ser va tions in the subse quently for all the pro files (from II to VI) by rel evant south-western part of the gravel pit wall, where an over 1-m co ef fi cients 1 or 2. The red fields in di cate the pres ence of wide “ditch” filled with sand is vis ible in the till (see Fig. 3). soils with higher appar ent resis tiv ity, i.e. sands and gravel. Results of the resis tiv ity survey have also been presented Fields marked yel low and green re fer to clays (till) with in a 3D map (Fig. 6). In the case of search for a system of shal- lower resistivities. The map shows that some red fields are low sand in fill ings within the till, this method of pre sent ing distinctly elon gated, which may be inter preted as the prob a- the results seems the most fa vourable. The vivid picture al- ble course of the sand struc tures. The im age is not com plete, most in stan taneously re veals not only the ori enta tion of the but shows the orien ta tion of the largest linea ments and traces main axes of resis tiv ity varia tion (and thus also lithol ogy), of a network with small mesh sizes. The pres ence of wide but also their depth. At cer tain light di rec tions, places with bands of high resis tiv ity val ues in the upper left on the map of higher resis tiv ity gather on the 3D map in longi tu di nal struc- AP PLI CA TION OF GEOELECTRICAL PRO FIL ING 79

Fig. 7. Maps of ap par ent re sistiv ity distri bution in a concen tric ar ray (A), and 24 h af ter brine appli ca tion (B) (modi fied from Mieszkowski and Porze¿yñski, 2004).

tures with a dis tinct “crest line”. These lines have been corre - area, followed by extrap o la tion of the obtained system on the lated with rele vant peaks on the working charts, which area in the hin ter land of the es carp ment. allowed deter mining the axes of the sand structures. The The obtained image distinctly points to the presence of structural axes on the plan have been corre lated with the narrow zones with high re sis tiv ity (>150 Wm), cor re spond - struc tures vis ible in the escarp ment of the gravel pit. As a re- ing to sands and gravel, within low resistivities corre spond - sult, the orien ta tion of the main axes was deter mined, al- ing to till (Fig. 7A). Lines connect ing the maxima are of though the fissure system seems incom plete. The main axes vari ous length, and in some places have been inter po lated be- of the recon structed ice wedges (NW-SE) are oblique to the tween the par tic u lar profiles. De spite that, a NW–SE orien ta - structural lines and corre spond to the domi nat ing slope dip in tion of the most distinct elongated fields can be seen. Out- the area. This may sug gest that during the frost processes, the lines of sections that are transverse and oblique to the main sur face of this part of the pla teau at tained a cer tain dip lines and in ter sec tions of ori en ta tion vari a tion of re sis tiv ity (Dzier¿ek and Stañczuk, 2006; Dzier¿ek, 2009). dis tri bu tion can be rec og nized. However, com pari son of the ob tained sketch of the The im age of sand structures obtained from resis tiv ity struc ture system with ex am ples of frost fissure sys tems in re - mea sure ments in the con cen tric ar ray was su per im posed on cent periglacial areas, shows that the polygons were not the struc tural lines de lin eated in the rect an gu lar ar ray (Fig. 8). closed and there was a lack of minor fis sures be tween the High corre la tion of the struc ture orien ta tion has been obtained. main fissures. In order to obtain a precise image, the same Some sections conform with one another, others rep resent ex- area was again subject to a geoelectrical sur vey, in this case tensions of the earlier ones, and some short sand structures in a pole-pole concen tric ar ray. have been regis tered in ei ther of the ar rays. Ad di tion ally, two se ries of geoelectrical mea sure ments RE SULTS OF GEOELECTRICAL SUR VEY have been conducted with brine intro duced into the system. IN A CONCEN TRIC AR RAY AND THEIR The idea was based on two main assump tions: 1) the brine will enhance the contrast (and reso lu tion of the readings) be- INTER PRE TA TION tween the resis tiv ity in sands within the pseudomorphs and The con cen tric ar ray com prised one elec trode sit u ated in their till surround ings; 2) the solu tion will dis perse within the the cir cle cen tre, with the second electrode repo sitioned ev - sands. Thus, it would be possi ble to detect the resis tiv ity ery 0.5 m along sixteen radi uses, each 8 m long. The at tained changes along the migra tion routes, i.e. ori enta tion of the density of the measure ment lines (angle value and radius sand pseudo morphs. In the cen tre of the concen tric array, length) seemed suf fi cient at the ex pected fis sure den sity. In within the sand infill ing of the pseudomorph, a hole was dug, this case, the survey was focused on check ing and eventu ally in which 80 l of 10% brine solu tion were intro duced. Resis - increas ing of the density of the obtained image within a small tiv ity mea sure ments in the con cen tric ar ray with ap pli ca tion 80 R. MIESZKOWSKI et al.

Fig. 8. Distri bution of periglacial struc tures in the hinter land of the gravel pit escarp ment at Wierzchuca Nagórna recog nized by geo log i - cal sound ing (modi fied from Mieszkowski and Porze¿yñski 2004)

of brine were con ducted one hour after the ap pli cation and re- AS SESS MENT OF THE USE FUL NESS peated after 24 hours. OF GEOELECTRICAL SOUNDING Maps show ing the re sults of sub se quent re sis tiv ity mea- FOR THE RECON STRUC TION OF SHALLOW sure ments in the con cen tric ar ray have shown cer tain vari - PERIGLACIAL STRUCTURES abil ity. The chart with re sis tiv ity measured 1 hour af ter brine intro duc tion shows a wide field of high resitivities close to The pre sented dis cussion of the results obtained from the centre and numer ous small dispersed fields, which rather geoelectrical measure ments in the study area at Wierzchuca dis tinctly in di cate lin ear vari abil ity of the re sis tiv ity val ues. Nagórna in the Drohiczyn Plateau provides several conclu - Clearer and lo cated closer to the cen tre are structures in the sions on assess ing the useful ness of the method in the recog - SW part of the system. The image for the situ a tion after 24 h nition of a frost fissure network. In general, geoelectrical of brine appli ca tion is more variable; fields with higher resis - profil ing does not deliver a de tailed im age of the surface sys- tiv ity values are larger and in some places con nected to form tem of periglacial struc tures. How ever, when its re sults are more dis tinct linear struc tures (Fig. 7B). cor re lated with a well-rec og nized geo log i cal set ting, the Images from the three se ries of measure ments, de spite margin for the inter pre ta tion of the results of geoelectrical some differ ences, conform the outlines of the main struc- sounding clearly narrows. The results have shown distinct tures. However, the results of the surveys did not fulfil the ex- and frequent re sis tiv ity varia tion in a small area as well as the pec ta tions. Re sis tiv ity changes are not com pletely unambi- presence of larger zones with higher resis tiv ity. Although the guous. Brine migra tion routes have turned out to be unclear recon structed network is not complete, it allowed to con- and peter out, and the im age after brine appli cation is not sig- clude on the palaeogeomorphology. In a few cases, narrow nifi cantly differ ent from the image without brine (see Fig. 7A high resis tiv ity zones distinctly record fragments of the net- and B). The techni cal reason for such im age could be the in- work mesh (polygons), provid ing infor ma tion on their size suf fi cient amount of so lu tion in the sys tem. In tro duc tion of and density. The network of pseudomorphs is irreg u lar and consid er able amounts of the solu tion would result in a signif - the smaller struc tures con tact at right an gles with the main i cant en vi ron men tal im pact. An other rea son could be the struc tures. geolog i cal set ting of the study area. The gravel pit wall shows It seems that geoelectrical pro filing using a rect an gu lar that some fissures with sand in fillings reach be low the base ar ray gives better re sults; their pre sen ta tion in re sis tiv ity of the im perme able till (Fig. 3). Thus, the brine solu tion vari a tion maps, par tic u larly in 3D, al lows for a geo log i cal in- could escape inwards, di rectly to the gravel hori zon under ly - ter pre ta tion. At tempts to en hance the sig nal by in tro duc tion ing the till. Even if the sys tem was sealed from the bot tom, the of brine and to obtain an im age of better res o lution have angle and dip orien ta tion of the entire system remain un- turned out to be inef fec tive. Moreover, larger labour input known, whereas these are the fac tors deter min ing the fa - and a signif i cantly high invasiveness of the method does not voured migra tion routes of the brine. permit its recom men da tion for such surveys. The obtained AP PLI CA TION OF GEOELECTRICAL PRO FIL ING 81 maps of re sis tiv ity dis tri bu tion with a char ac ter is tic rhythm Lindner, L., Marks, L., 2012. On the climatostratigraphic scheme of of nu mer ous vari ations may exem plify the geoelectrical re- the Mid dle Pol ish complex in the Pleis to cene of Po land. Prz. cord of periglacial structures and can be used to compare the Geol., 60, 36–45. (in pol ish with Eng lish summary) results of such studies in ar eas with out expo sures. It seems Mackay, J.R., 1993. Air tem per a ture, snow cover, creep of frozen ground, and the time of ice-wedge crack ing, west ern Arc tic that the hin ter land of the es carp ment of the Wierchuca Na- coast. Canad. J. Earth Sci., 30, 1720-1729. górna expo sure in the Drohiczyn Plateau is a perfect bench- Maizels, J. K., 1986. Fre quency of relic frost-fissure struc tures and mark for test ing other geophys i cal methods, e.g. georadar pre dic tion of poly gon pat tern. A quan ti ta tive ap proach. Biul. sur veys and elec tri cal re sis tiv ity to mog ra phy. Perygl., 30, 67-89. Marks, L., Pavlovskaya, I. 2004. Extens of Pleis to cene glaciations CON CLU SIONS in East ern Po land and West ern Belarus (Zasiêgi zlodowaceñ plejstoceñskich na obszarze Wschodniej Polski i Zachodniej Expe ri ence gained during geoelectrical surveys in the Bia³orusi). Mat. XI Konferencja Stratygrafia Plejstocenu Drohiczyn Pla teau near Wierzchuca Nagórna can be as sem- Polski, Supraœl, 8-10. (in Polish) bled in several conclu sions. Marks, L., 2005. Pleisto cene glacial limits in the terri tory of Poland. – High-res o lu tion geoelectrical pro fil ing has con firmed Prz. Geol., 53 (10/2), 988-993. the presence of numer ous periglacial struc tures, observed in Mieszkowski, R., Porze¿yñski, S., 2004. Report on the re sults of the nearby expo sure, and enabled a partial recon struc tion of geoelectrical survey in the re gion of Drohiczyn. (Opracowanie wyników badañ geoelektrycznych w rejonie Drohiczyna). their surface pat tern. Arch. Inst. Geol. Podst. Uniw. Warsz., ss. 6. (in Pol ish) – Periglacial struc tures are man ifested in the map of soil Mieszkowski, R., Porze¿yñski, S., 2006. Report on the re sults of re sis tiv ity dis tri bu tion as nar row elon gated fields with high geoelectrical survey in the re gion of Drohiczyn. Part II. (Opra- resistivities (sand with gravel) in a low resis tiv ity back- cowanie wyników badañ geoelektrycznych w rejonie Drohi- ground (till). czyna. Cz. II.), ss. 8. (in Pol ish) – Tthe struc tures are NW-SE-oriented and have a small Murton, J., Wors ley, B., GoŸdzik, J., 2000. Sand veins and wedges diam e ter of single fissure polygons; these data have been ap- in cold Ae olian en vi ron ments. Quatern. Sci. Rev., 19, 899-922. plied in palaeogeographic recon struc tions (Dzier¿ek, 2009). Nitychoruk, J., Dzier¿ek, J. Stañczuk, D., 2008a. Detailed Geo log i - – Measure ments in a rect an gu lar ar ray have given better cal Map of Po land in the scale 1: 50 000; Drohiczyn Sheet. results. They are less time-consum ing, non-in vasive, have (Szczegó³owa mapa geologiczna Polski w skali 1 : 50 000 ark. Drohiczyn - 494). Pañstw. Inst. Geol. (in Pol ish – electronical cov ered a larger area and the re sults are eas ier to in ter pret. doc u ment) – Rresults obtained for the marginal profiles of the rect- Nitychoruk, J., Dzier¿ek, J. Stañczuk, D., 2008b. Ex pla na tions to an gu lar ar ray are un re liable and may be con sid ered only af ter the De tailed Geo log i cal Map of Po land in the scale 1: 50 000; rel e vant cor rec tions. Drohiczyn Sheet. (Objaœnienia do Szczegó³owe mapy geolo- – Attempt to enhance the contrast of the readings by in- gicznej Polski w skali 1 : 50 000 ark. Drohiczyn - 494). Pañstw. troduc tion of brine in the system has been proved in effec tive, Inst. Geol., ss. 53 (in Pol ish – electronical doc u ment) al though it sup plied new pos si bil i ties of in ter pret ing the Stenzel, P., Szymanko, J., 1973. Geo physi cal meth ods in hydrogeo- sub-sur face geo log i cal struc ture of the area. log i cal and geo log i cal-en gi neer ing stud ies. (Metody geofi- – Corre la tion of the results of geoelectrical surveys to zyczne w badaniach hydrogeologicznych i geologiczno in¿y- nierskich). Wyd. Geol. Warszawa. the geo log i cal suc ces sion has fa cil i tated their in ter pre ta tion. Washburn, A., 1973. Periglacial pro cesses and en vi ron ments. Ed - The obtained resis tiv ity distri bu tion map may serve as com- ward Arnold. Lon don. par a tive ma te rial in the iden ti fi ca tion of periglacial struc tures with appli ca tion of geoelectrical sounding in areas without ex po sures. – Veri fi ca tion of the obtained results could be achieved by conduct ing other geophys i cal surveys in the area.

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