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Utilization of the analysis of ancient river beds for the detection of Holocene crustal movements
Tectonophysics, 29 (1975) 359-368 0 Elsevier Scientific Publishing Company,
359
Amsterdam
- Printed
in The Netherlands
UTILIZATION OF THE ANALYSIS OF ANCIENT RIVER BEDS FOR THE DETECTION OF HOLOCENE CRUSTAL MOVEMENTS KliROLY
MIKE
research
Institute
(Revised
version
for Water development, accepted
August
Budapest
~~u~ga~~
21, 1975)
ABSTRACT Mike, K., 1975. Utilization of the analysis of ancient river beds for the detection of Holocene crustal movements. In: N. Pavoni and R. Green (Editors), Recent Crustal Movements. Tectonophysics, 29 (l-4): 359-368. On the present-day surface of the continuously subsiding Great Hungarian Plain, bends of ancient rivers can be traced. The axes of the ancient beds are parallel to each other in some zones, which, on the other hand, cross each other. This provides a possibility of detecting the temporal succession of their formation. The study of the ancient river beds permits of drawing conclusions as to the tendencies and intensities of bed wandering. The age of the beds is (Early) Holocene, with differences within this range. The tendency of the movements changed at the end of the Pleistocene, subsidence starting along the NW marginal faults instead of the SE ones. This resulted in a tilting of the Great Plain to the NW.
INTRODUCTION
Geology, just like other sciences, approaches its objects of study, e.g. the dating of a given stratum, from various aspects. The usual methods, however, have been of little, if any, use for chronological subdivision within the Holocene, which is badly needed in studying the evolution of a river. Accordingly, a new approach was attempted, the analysis of detectable traces of ancient river beds. The investigations revealed some vertical changes resulting in Holocene faults. THE NEW METHOD
The Great Hungarian Plain has been traversed by rivers of various The rivers Danube, Tisza, Maros, Kiiros, etc. developed bends, their sions depending on the water yield and the fall gradient. Since the Early Pleistocene, the biggest river in the area of study the Tisza (Fig. 1). In Hungary, the main parameters of the bends of
sizes. dimenhas been the
Fig. 1. Ancient bed traces in the KG& and Maros area. 1 = present-day 2 = Tisza-size bends; 3 = Maros-size bends; 4 = K&iis-size bends.
Tisza are as follows: amplitude length of arch length of chord
600 m; 2000 m; 1000 m.
hydrography;
361
These data are characteristic also for the present-day river bed in as far as it has not been modified by regulation. The Hungarian courses of the rivers Maros and Koros have been regulated to run almost straight. Nevertheless, the dimensions of the short-cut bends provided information for the identification of the ancient beds. The bends of the ancient Maros are characterized in Hungary by the following data: amplitude length of arch length of chord
400 m; 1500 m; 900 m.
Another characteristic feature of the bed of the Maros was the great amount of non-embedded alluvium. The bend traces at many places have been overshadowed by floodmarks (Fig. 2). The main parameters of the bends of the river Koros in Hungary are the following (Fig. 3): amplitude length of arch length of chord
200 m; 800 m; 500 m.
They cannot be mistaken for bends of the Tisza or the Maros; the Koros river, which also carries the waters of the tributaries Fekete Koros, Sebes Koros and Berettyo, developed bends of much smaller size. Where these occur, the ancient beds of the Tisza are absent, their continuity being interrupted. Consequently, the micro-bends are younger than the zones of larger beds. In Fig. 4, the letters of the alphabet denote zones of similar-size bends, with the exception of the letter h. The present-day bed of the river Tisza is situated at the western margin of the zone h in the northern sector, while it occupies the centre of the bed zones in the southern sector. Accordingly, this is the youngest bed zone of the Tisza. The development of zone h was preceded by that of the zone g. The sediments of zone h covered the latter in some parts, over a length of 50 km. The dimensions of the beds are rather reduced, and their ramifications suggest the lower course character of the river which was unable to carry its alluvium (Borsy, 1953). The Boreal period, which was low in precipitation, is suggested as the possible age of its formation. This river-bed zone cannot be due to other rivers than the Tisza, flowing from the NE. The g sediments cover the sediments marked f and e, which are, consequently, more ancient. For similar reasons, zone d is still more ancient. The river beds marked a, b and c diverge in the Koros area, crossing each other further to the SW. The superposition indicates that a is the oldest and c is the youngest of these three. As for the age of the beds, one starting point is the present-day position
0 ISElI.
Fig. 2. Traces of the ancient Maros on the present 3 = probable strike of buried bed zones.
10 20
30 40
50 km
LZGEl3.
surface.
1 = bends; 2 = flood marks;
of the rivers. At present, the river Tisza flows along the NE margin of its ancient bed traces, in the lowest part of the topography (80-90 m above sea level). The most distant ancient bends are situated on the highest sector of the surface (110 m above sea level), along the Romanian frontier. These are cut into red clay derived from Wiirmian loess. Accordingly, even this bed
363
4
0
10 20 30
40 km
Fig. 3. Traces of the ancient Kijriis on the present surface.
is undoubtedly of postglacial age, namely Early Holocene. This ancient bed is situated at a distance of 100 km from the present-day one. The surface slopes gradually towards the latter and there are two types of ancient beds on it. One type has wider bends, suggesting a greater yield due to a humid climate, while the other is small-bended, testifying to a less humid climate
364
Fig. 4. Traces of the ancient Tisza on the present-day of buried bed zones; 2 = ancient Tisza bends.
surface.
1 = probable
prolongation
(Boreal phase). This is another basis for the approach. The individual ancient beds can be dated approximately by interpolation. The determination of their temporal succession is facilitated by the fact that they cross each other, reworking the more ancient sediments.
365 UTILIZATION
OF THE METHOD
Changes in the hydro~phy directly indicate vertical movement of the earth’s crust (relative uplift and subsidence, respectively) which were followed by the rivers just as by the level of a surveyor’s instrument. The study of the detailed geological cross-sections, based on the analysis
Fig. 5. Sketch map of the area of study. 1 f: area of detailed studies; 2 = Holocene fault; 3 = Holocene upthrust; 4 = Pleistocene fault.
366
of rhythms in the sedimentation, revealed the Pleistocene evolution of the hydrography (Mike, 1974), providing the historical background for the recent movement trends. The following events could be detected: (1) In the Late Pleistocene, the river Tisza flowed from NE to the region of the Kiirtis, turned to the N, and near the town of JBszbereny, flowed
J Fig. 6. Horizontal movements in recent time as detected by repeated high-precision levetiing (after L. Bendefy). 1 = dcplacement related to the basis level (mm/IO year); 2 = fix points.
367
further along the course of the present creek Zagyva to its present course between the towns Szolnok and Szeged. This advance of the river Tisza to the N indicates the vigorous subsidence of the southern foreland of the Biikk Mountains. (2) In the earliest Holocene, a renewed subsidence set in along the SE marginal faults. The river Tisza, still flowing along bed of the present-day brook called the Er to the Koros region, turned to the S and cutting its bed into the Late Wiirmian red clay, proceeded along the W foothills of the Transylvanian Central Mountains almost to the present river Maros. There it turned to the W and parallel to the present-day Maros, across the town Hodmezovasarhely and turned into the present Szeged Depression. The river has wandered about 150 km to the SE. This large-scale wandering also testifies to crustal movements, viz. to the sinking of the Ermellek area, as well as to the tilting of the Great Plain to the SE along the structural lines at the margin of the basin (Fig. 5). (3) During the Holocene, the subsidence of the N border of the Great Plain again became predominant, as it is indicated by the successive shifting of the Tisza bed line by about 100 km to the N (Mike, 1968). This tendency in the crustal movements harmonizes with the serial highprecision levelling data evaluated by Bendefy (1964). Fig. 6 illustrates the tendencies and range of movements. The recent vertical movements also make it understandable why the Tisza flowed in the Early Holocene towards the south, and why it turned to the W north of the Maros (b and c stages on Fig. 4). Figs. 4 and 6 are in harmony with each other in this respect, also, in that the ancient bed traces marked d, e and f were developed in zones of delayed uplift. The westward shifting of the Tisza can be explained by the fact that the Szolnok-Szeged section of the river Tisza is still subsiding intensively. CONCLUSIONS
The analysis of ancient bed traces, like all other detail studies, can be applied only in combination with other investigations. It is useful above all in determining the tendencies of crustal movements - an important point for river regulation. Moreover, it can be successfully applied in more accurate and detailed mapping of Late Pleistocene and Holocene formations . REFERENCES Bendefy, L., 1964. Magyarorszig geokinetikai es keregszerkezeti viszonyai a megisme’telt szabatos szintezesek eredme’nyei alapj&n (The geokinetical and tectonic features of Hungary as revealed by repeated high-precision levelling) Acta Geod., MTA. Borsy, Z., 1993. A Bodrogkijz kialakulasa (The formation of the Bodrog interfluvial). Foldrajzi Ert., 3: 409-418.
368
Mike, K., 1968. A Tisza magyarorszagi szakaszanak kialakulasa (The development of the Hungarian section of the river Tisza). VITUKI Vizrajzi Atlasz, 7 (1): 1-13. . Mike, K., 1974. A Korosok kialakulasa es fejlGd6se (The origin and development of the Kijras river). VITUKI Vizrajzi Atlasz, 18 (1): 28-44. Moldvay, L., 1961. A Berettyc v6lgy es a deli Nyirseg-perem felszini kepztidmdnyeinek kifej1b;des.e es kora (The facies and age of the Beretty6 Valley and of the southern margin of the Nyirsdg area). Fcldt. Kb;zl., 3: 292-299.
359
Amsterdam
- Printed
in The Netherlands
UTILIZATION OF THE ANALYSIS OF ANCIENT RIVER BEDS FOR THE DETECTION OF HOLOCENE CRUSTAL MOVEMENTS KliROLY
MIKE
research
Institute
(Revised
version
for Water development, accepted
August
Budapest
~~u~ga~~
21, 1975)
ABSTRACT Mike, K., 1975. Utilization of the analysis of ancient river beds for the detection of Holocene crustal movements. In: N. Pavoni and R. Green (Editors), Recent Crustal Movements. Tectonophysics, 29 (l-4): 359-368. On the present-day surface of the continuously subsiding Great Hungarian Plain, bends of ancient rivers can be traced. The axes of the ancient beds are parallel to each other in some zones, which, on the other hand, cross each other. This provides a possibility of detecting the temporal succession of their formation. The study of the ancient river beds permits of drawing conclusions as to the tendencies and intensities of bed wandering. The age of the beds is (Early) Holocene, with differences within this range. The tendency of the movements changed at the end of the Pleistocene, subsidence starting along the NW marginal faults instead of the SE ones. This resulted in a tilting of the Great Plain to the NW.
INTRODUCTION
Geology, just like other sciences, approaches its objects of study, e.g. the dating of a given stratum, from various aspects. The usual methods, however, have been of little, if any, use for chronological subdivision within the Holocene, which is badly needed in studying the evolution of a river. Accordingly, a new approach was attempted, the analysis of detectable traces of ancient river beds. The investigations revealed some vertical changes resulting in Holocene faults. THE NEW METHOD
The Great Hungarian Plain has been traversed by rivers of various The rivers Danube, Tisza, Maros, Kiiros, etc. developed bends, their sions depending on the water yield and the fall gradient. Since the Early Pleistocene, the biggest river in the area of study the Tisza (Fig. 1). In Hungary, the main parameters of the bends of
sizes. dimenhas been the
Fig. 1. Ancient bed traces in the KG& and Maros area. 1 = present-day 2 = Tisza-size bends; 3 = Maros-size bends; 4 = K&iis-size bends.
Tisza are as follows: amplitude length of arch length of chord
600 m; 2000 m; 1000 m.
hydrography;
361
These data are characteristic also for the present-day river bed in as far as it has not been modified by regulation. The Hungarian courses of the rivers Maros and Koros have been regulated to run almost straight. Nevertheless, the dimensions of the short-cut bends provided information for the identification of the ancient beds. The bends of the ancient Maros are characterized in Hungary by the following data: amplitude length of arch length of chord
400 m; 1500 m; 900 m.
Another characteristic feature of the bed of the Maros was the great amount of non-embedded alluvium. The bend traces at many places have been overshadowed by floodmarks (Fig. 2). The main parameters of the bends of the river Koros in Hungary are the following (Fig. 3): amplitude length of arch length of chord
200 m; 800 m; 500 m.
They cannot be mistaken for bends of the Tisza or the Maros; the Koros river, which also carries the waters of the tributaries Fekete Koros, Sebes Koros and Berettyo, developed bends of much smaller size. Where these occur, the ancient beds of the Tisza are absent, their continuity being interrupted. Consequently, the micro-bends are younger than the zones of larger beds. In Fig. 4, the letters of the alphabet denote zones of similar-size bends, with the exception of the letter h. The present-day bed of the river Tisza is situated at the western margin of the zone h in the northern sector, while it occupies the centre of the bed zones in the southern sector. Accordingly, this is the youngest bed zone of the Tisza. The development of zone h was preceded by that of the zone g. The sediments of zone h covered the latter in some parts, over a length of 50 km. The dimensions of the beds are rather reduced, and their ramifications suggest the lower course character of the river which was unable to carry its alluvium (Borsy, 1953). The Boreal period, which was low in precipitation, is suggested as the possible age of its formation. This river-bed zone cannot be due to other rivers than the Tisza, flowing from the NE. The g sediments cover the sediments marked f and e, which are, consequently, more ancient. For similar reasons, zone d is still more ancient. The river beds marked a, b and c diverge in the Koros area, crossing each other further to the SW. The superposition indicates that a is the oldest and c is the youngest of these three. As for the age of the beds, one starting point is the present-day position
0 ISElI.
Fig. 2. Traces of the ancient Maros on the present 3 = probable strike of buried bed zones.
10 20
30 40
50 km
LZGEl3.
surface.
1 = bends; 2 = flood marks;
of the rivers. At present, the river Tisza flows along the NE margin of its ancient bed traces, in the lowest part of the topography (80-90 m above sea level). The most distant ancient bends are situated on the highest sector of the surface (110 m above sea level), along the Romanian frontier. These are cut into red clay derived from Wiirmian loess. Accordingly, even this bed
363
4
0
10 20 30
40 km
Fig. 3. Traces of the ancient Kijriis on the present surface.
is undoubtedly of postglacial age, namely Early Holocene. This ancient bed is situated at a distance of 100 km from the present-day one. The surface slopes gradually towards the latter and there are two types of ancient beds on it. One type has wider bends, suggesting a greater yield due to a humid climate, while the other is small-bended, testifying to a less humid climate
364
Fig. 4. Traces of the ancient Tisza on the present-day of buried bed zones; 2 = ancient Tisza bends.
surface.
1 = probable
prolongation
(Boreal phase). This is another basis for the approach. The individual ancient beds can be dated approximately by interpolation. The determination of their temporal succession is facilitated by the fact that they cross each other, reworking the more ancient sediments.
365 UTILIZATION
OF THE METHOD
Changes in the hydro~phy directly indicate vertical movement of the earth’s crust (relative uplift and subsidence, respectively) which were followed by the rivers just as by the level of a surveyor’s instrument. The study of the detailed geological cross-sections, based on the analysis
Fig. 5. Sketch map of the area of study. 1 f: area of detailed studies; 2 = Holocene fault; 3 = Holocene upthrust; 4 = Pleistocene fault.
366
of rhythms in the sedimentation, revealed the Pleistocene evolution of the hydrography (Mike, 1974), providing the historical background for the recent movement trends. The following events could be detected: (1) In the Late Pleistocene, the river Tisza flowed from NE to the region of the Kiirtis, turned to the N, and near the town of JBszbereny, flowed
J Fig. 6. Horizontal movements in recent time as detected by repeated high-precision levetiing (after L. Bendefy). 1 = dcplacement related to the basis level (mm/IO year); 2 = fix points.
367
further along the course of the present creek Zagyva to its present course between the towns Szolnok and Szeged. This advance of the river Tisza to the N indicates the vigorous subsidence of the southern foreland of the Biikk Mountains. (2) In the earliest Holocene, a renewed subsidence set in along the SE marginal faults. The river Tisza, still flowing along bed of the present-day brook called the Er to the Koros region, turned to the S and cutting its bed into the Late Wiirmian red clay, proceeded along the W foothills of the Transylvanian Central Mountains almost to the present river Maros. There it turned to the W and parallel to the present-day Maros, across the town Hodmezovasarhely and turned into the present Szeged Depression. The river has wandered about 150 km to the SE. This large-scale wandering also testifies to crustal movements, viz. to the sinking of the Ermellek area, as well as to the tilting of the Great Plain to the SE along the structural lines at the margin of the basin (Fig. 5). (3) During the Holocene, the subsidence of the N border of the Great Plain again became predominant, as it is indicated by the successive shifting of the Tisza bed line by about 100 km to the N (Mike, 1968). This tendency in the crustal movements harmonizes with the serial highprecision levelling data evaluated by Bendefy (1964). Fig. 6 illustrates the tendencies and range of movements. The recent vertical movements also make it understandable why the Tisza flowed in the Early Holocene towards the south, and why it turned to the W north of the Maros (b and c stages on Fig. 4). Figs. 4 and 6 are in harmony with each other in this respect, also, in that the ancient bed traces marked d, e and f were developed in zones of delayed uplift. The westward shifting of the Tisza can be explained by the fact that the Szolnok-Szeged section of the river Tisza is still subsiding intensively. CONCLUSIONS
The analysis of ancient bed traces, like all other detail studies, can be applied only in combination with other investigations. It is useful above all in determining the tendencies of crustal movements - an important point for river regulation. Moreover, it can be successfully applied in more accurate and detailed mapping of Late Pleistocene and Holocene formations . REFERENCES Bendefy, L., 1964. Magyarorszig geokinetikai es keregszerkezeti viszonyai a megisme’telt szabatos szintezesek eredme’nyei alapj&n (The geokinetical and tectonic features of Hungary as revealed by repeated high-precision levelling) Acta Geod., MTA. Borsy, Z., 1993. A Bodrogkijz kialakulasa (The formation of the Bodrog interfluvial). Foldrajzi Ert., 3: 409-418.
368
Mike, K., 1968. A Tisza magyarorszagi szakaszanak kialakulasa (The development of the Hungarian section of the river Tisza). VITUKI Vizrajzi Atlasz, 7 (1): 1-13. . Mike, K., 1974. A Korosok kialakulasa es fejlGd6se (The origin and development of the Kijras river). VITUKI Vizrajzi Atlasz, 18 (1): 28-44. Moldvay, L., 1961. A Berettyc v6lgy es a deli Nyirseg-perem felszini kepztidmdnyeinek kifej1b;des.e es kora (The facies and age of the Beretty6 Valley and of the southern margin of the Nyirsdg area). Fcldt. Kb;zl., 3: 292-299.