Description Of Sites in Hungary

Mogyorod Site

Large V-shaped features are to be found in a gravel pit (47°35'N, 19°13'E; 255 m a.s.l.) near Mogyorod (15 km north-east of Budapest) in the northern part of the Godollo Hills (Figure 8). The geological section at this site is composed of two very different deposits [12, 65]. The lower deposit is an Upper Pliocene alluvial fan of Palaeo-Danube origin overlain by aeolian sandy deposits. A thick, red paleosols developed on the lower deposit. The color is yellowish red (5YR 5/8) and the thickness of the paleosols indicates that it was most likely developed in a much warmer climate than currently exists.

The sand wedges found in the red paleosol have a polygonal system, consequently it is considered as a sand-wedge polygon. The wedges have an average vertical dimension of 1.52.0 m, but range up to 3 m (Figure 9). The wedge width was measured at right angle of the axial plane of the wedge [39]. Additionally these wedges are 25-30 cm and 50-60 cm or slightly more in width (Figures 9 and 10). The sand-filled wedge structures have simple V shapes with rectilinear or slightly curved sides (convex outward) and pointed toes (Figure 10). The fill of the wedges is sub-vertically laminated; the sand itself is fine- to medium-grained (1-3 9) and moderately well sorted. The color of the sand material is light grey (2.5Y 7/2). Some wedges contain pebbles at or near the top. The host strata adjacent to sand wedges are upturned. In plan view, it forms polygonal network with cracks spaced 2-5 meters apart. The cracks are irregular and several meters long [29].

Sand Wedge Geomorfology
Figure 9. Relict sand wedges in Mogyorod, Hungary. (Depth of profile 3.5 m)
Aeolian Sandy Soil

Figure 10. Detailed section through a relict sand wedge in Mogyorod, Hungary. 1 - recent soil, 2 -CaCO3 accumulation, 3 - aeolian sand, 4 - sandy gravel, 5 - sand wedge, 6 - palaeosol with lower gravel content, 7 - palaeosol with higher gravel content, 8 - desert pavement, 9, 10 and 11 - Pliocene alluvial fan of Palaeo-Danube.

Figure 10. Detailed section through a relict sand wedge in Mogyorod, Hungary. 1 - recent soil, 2 -CaCO3 accumulation, 3 - aeolian sand, 4 - sandy gravel, 5 - sand wedge, 6 - palaeosol with lower gravel content, 7 - palaeosol with higher gravel content, 8 - desert pavement, 9, 10 and 11 - Pliocene alluvial fan of Palaeo-Danube.

Visonta and Atkar Sites

According to Horvath et al. [20], the platy, lenticular, fitted breccia structure in the excavation in Visonta (47°45'N, 20°07'E; 135 m a.s.l.) is connected to involutions and drop soils (Figure 8 and cf. Plate II. Fig. 7 in [20]). The laminae of this structure follow the curve of involutions. Accepting that the platy, lenticular structure could be a good evidence for frost-action [20, 71], this observation suggests that frost played a role in the formation of the involutions.

The geology of Atkar (47°42'N, 19°52'E; 143 m a.s.l.) is similar to that of Visonta. The exposed extent of the deformation horizon is about 30 m in length and 1.5 m in height (Figure 11). Sagging load casts are very common, mainly in the upper and middle part of the deformed horizon as described by Horvath et al. [20]. These are 0.1 to 0.5 m sized bands in which former stratification and pedogenic horizons are discernible. These bands are more or less continuous and have a downward convex shape. Drops which are dm scaled, rounded, ellipsoidal occur in the upper and middle part of the deformed horizon but occasionally are traceable also at the lower levels (Figure 12).

Involution Geology
Figure 11. The view of Atkar site, load casts, waves and involution are visible in this profile. (Spoon for scale = 0.2 m)
Figure 12. Well-developed drop soils in Atkar profile. (Note the scale is 0.6 m)

Soroksar and Vanyarc Sites

According to Horvath et al. [21], 3-5 cm wide downwards narrowing fissures were observed in the stratified sandy sediment in Soroksar (47°23'N, 19°07'E), near Budapest (archaeological excavation, trench 12), which were filled in with coarse sand (Figures 8 and 13). The parallel fissure system extends down to a very hard grey sandy level. This may mark the former dryland surface. Such wedges can appear in a sandy deposit when the otherwise loose sand behaves like a rock. This can happen when the water content freezes in the soil which then cracks like a hard rock, and the empty fissure is filled in with sediment from above. Such a phenomenon can be interpreted as a frost fissure. It is evidence to perennially frozen ground; beside the frost crack, a turbulent layer disturbance also appears in the same sandy deposit (Figure 13) probably resulted from cryoturbation. Such extremely cold weather with long-lasting frost in the soil is encountered during Pleistocene glacial periods.

Polygons were identified on the hilltop located near the village of Vanyarc (47°49'N, 19°27'E), northeast from Budapest (Figures 8 and 14). Several adjoining low-relief polygons up to 0.5-1.0 m in diameter are defined by shallow cracks [cf. Fig. 7 in 23]. In cross-section these cracks are filled with coarse sand, forming V-shaped wedges that extend to 0.5 m below the surface.

Cryoturbation
Figure 13. Cryoturbation in plan view from the Soroksâr archaeological excavation site (courtesy of Z. Horvâth).
Ground Tempruture Imeges
Figure 14. Patterned ground in plan view from the Vanyarc archaeological excavation site (courtesy of Z. Horvath).

Babolna Site

Various wedge-shaped features and sand involutions were found in a Babolna gravel pit (47°40'N, 17°59'E; 150 m a.s.l.). The ice wedge casts in this gravel pit developed when former ice wedges melted and the wedge space filled with the surrounding gravelly materials (Figure 8). It should be pointed out that ice wedge casts are a very good indicator of a former permafrost environment since ice wedges develop only in permafrost. The vertical dimension of the wedges is 0.5-1.0 m and, in areas where the surface has been bladed by a bulldozer, the polygonal pattern is clearly visible [65].

Paks Site

Two brownish layers, most likely representing the B-horizons of two distinct paleosols, were identified in the exposed profile (46°35'N, 18°50'E 95 m a.s.l.) in the Paks sand deposits (Figure 8). A thick sand layer on which the contemporary soil has developed overlay these paleosols. This contemporary soil is associated with a thick, organic-rich, surface horizon and is quite different from those B-horizons associated with the underlying paleosols.

The B-horizons of both paleosols were contorted and disrupted, and a wedge-shaped sand body that was identified as a sand wedge also dissected the B-horizon of the lower paleosol. Closer examination of these paleosols revealed strong mottles, suggesting that a fluctuating water table affected this horizon. Thin organic layers associated with what seemed to be a former vertical crack were also observed.

Csipkerek Site

Many sand wedges were identified that display vertical foliation, form polygonal nets, and penetrate alluvial gravel deposit (Csipkerek gravel pit: 47°05'N, 16°56'E; 230 m a.s.l.). The age of the gravel is controversial. The gravel of Kemeneshat developed in Pleistocene [1], however the gravelstone of Csipkerek site in some places is overlain and cemented by red clay, therefore they are supposed to be older: Pliocene. More than ten wedges from one borrow pit wall are described here (Figure 15). Wedges are extensive with a mean width of 1 m and the mean height of 2-3 m. Wedge spacing is on average ~10 m, a similar spacing observed by Carter [7] for relict wedges in Alaska. The host strata adjacent to sand wedges are upturned. The wedge sand is fine to medium grained. The color (2.5Y 7/4) and grain size of the infilling sand is the same as the others we found nearby in Kemeneshat.

Ice Wedge Cast
Figure 15. Sand wedge with adjacent upturned gravel strings in Csipkerek site. (Hammer for scale = 0.4 m)
Ice Wedge Cast Images
Figure 17. Close up view of an ice wedge cast in Billege-erdo, Hungary.

Billege Site

Our latest research site is the Billege-erdo gravel pit (46°53'N, 17°21'E; 130 m a.s.l.) several km from the western basin of Lake Balaton [15, 47]. Large, mostly U-shaped features can be seen here which deepens into Late Neogene delta fan deposits (Figures 8 and 16). These fissures were identified that display horizontal foliation and penetrate gravelstone (Figure 17). Cracks are extensive with a mean width of 1.5 m and the mean height of 2-3 m. The fill of the fissures is horizontally laminated; the sand itself is medium-grained and moderately well sorted. The color of the sand material is light grey (2.5Y 7/2). Most ice-wedge pseudomorphs are found in gravel. This is because this coarse-grained sediment is usually ice-poor [13].

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