DACIAN BASIN - GeoEcoMar

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102 Chapter 5. Littoral Sedimentary Environment in the Dacian Basin FIGURE 5.11. Conversion from symmetrical to asymmetrical ripple, through subsequent sediment accumulation (A). Late Pontian, Râmnicu Sărat River (Dumitreşti, Vrancea County) FIGURE 5.12. Symmetrical-shaped ripple with current lamination internal structure. Late Maeotian shoreface sediments from Râmnicu Sărat River (Jitia de Jos village, Vrancea County).
5.2. Shoreline sedimentation environment in the Dacian Basin Some of the clayey sedimentary sequences include thin fine grained sand interbeds, with wave ripples. In the Bădislava River Late Pontian succession (Fig. 5.13 C), many of the thin sandy intercalations show wave ripples. These sandy units with symmetrical ripples are several centimeters thick. No clear vertical grain size sorting can be distinguished within the thin sandy intercalations. Thicker sandy beds (10 – 20 cm) occur also, but they represent a minority. A hummocky cross stratification structure was observed in one of the thicker beds. In accordance with the limited sandy sediment accumulation rate the sequences with the characteristics presented above belong to the low energy shoreface category. High energy wave-controlled shoreline environment. The higher energy shoreline environment is marked by the presence of better developed, thicker sandy units (Fig. 5.13 B, C, D). The most representative of these sandy units are 1-2 m thick units with distinct coarsening upward trend (Fig. 5.14). Wave ripples are observed in the basal part of the coarsening upward units, but they are replaced with current structures at higher levels of the sequence (Fig. 5.15). In the shoreline sedimentary section from Chiojdeni (Râmnicu Sărat River) (Fig. 5.15), a hummocky type structure occurs. The size of the cross lamination structures is larger to the upper part of the coarsening up unit. The sediment succession is topped by symmetrical ripples. The sediment sequences attributed to the lower or higher energy shoreline might also represent sediment accumulation in the lower or middle shoreface area. The rate of sediment influx could also control the character of the two types of shoreface sequences. Parallel lamination shoreline environment. The high energy Dacian Basin shoreline sequences also include sandy units with parallel lamination (Fig. 5.13 B, C, and D). At the Chiojdeni geological section (Râmnicu Sărat River) (Fig. 5.16), the parallel laminated interval consists of three units, summing up a thickness of two meters. Two of the three units show trough cross-lamination at the upper part. Wave ripples occur at the top of the upper unit, as well as a deformation structure. The whole parallel laminated sequence appears to represent a very high energy shoreline environment, which was getting more tranquil at the end of the event. 5.2.2. Storm-controlled shoreline environment The littoral units in the Dacian Basin incorporate occurrences of storm generated sedimentary structures (Fig. 5.17). The frequency of this type of structure is low, indicating that storm currents did not influence significantly the Dacian Basin shoreline or near-shore sediment accumulation. The only storm-controlled shoreline sediments sknown in the Dacian Basin are Maeotian in age and crop out in the geological section of the Bizdidel River, east of Pucioasa town, in the Dâmboviţa County. 103
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Dan C. Jipa, Cornel Olariu DACIAN B
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Dedicated to the memory of Prof. Gh
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NATIONAL INSTITUTE OF MARINE GEOLOG
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CONTENTS Foreword and Acknowledgeme
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Contents Chapter 7. The Point Bar F
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FOREwORD AND ACkNOwLEDgEMENTS The s
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PLATE 1. Location of the Dacian Bas
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18 Chapter 1. Dacian Basin. General
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The analysis of the paleogeographic
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42 Chapter 2. Dacian Basin paleogeo
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Page 54 and 55: 52 Chapter 2. Dacian Basin paleogeo
Page 60 and 61: 58 FIGURE 2.14. Paleogeography and
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Page 84 and 85: Sedimentation in the brackish-water
Page 86 and 87: 84 Chapter 4. Dacian Basin Physiogr
Page 96 and 97: 94 Chapter 5. Littoral Sedimentary
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Page 138 and 139: 136 Chapter 6. Upper Neogene Fluvia
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152 Chapter 6. Upper Neogene Fluvia
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154 Chapter 6. Upper Neogene Fluvia
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The large and continuous rock expos
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158 Chapter 7. The Point Bar Facies
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190 Chapter 8. The Paleoenvironment
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The evolution and architecture of a
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200 Chapter 9. Source-Areas in the
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10.1. SEDIMENT ACCUMULATION AREAS I
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214 Chapter 10. History of the Daci
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230 Chapter 11. From Brackish-Marin
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Ai n s w o r t h r. B., Cr o w l e
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258 References hA m o r, g., et al.
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260 References mA C A r o V iC i, n
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262 References ră d A n, s.C., 200
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264 References VAsilieV, i., Kr iJ
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