DACIAN BASIN - GeoEcoMar

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54 Chapter 2. Dacian Basin paleogeography. Sedimentological interpretation the southern margin of the Dacian Basin migrated small distances during the Early and Middle Pontian, and larger distances during the Late Pontian. Both sets of paleogeographic maps indicate that only the central and centraleastern parts of the southern Dacian Basin limit are subject to migration. In contrast the southern shift is not apparent in the southwestern part of the Dacian Basin. Sediment thickness distribution. The sediment thickness (isopach maps) from the initial stage of existence of the Dacian Basin indicates that the accumulation of detrital material was more active in the eastern part of the basin, less active in the western part, while the area in between was sediment-starved (Fig. 2.12). Starting from the Maeotian at the southern periphery of the basin an area with low sedimentation rate and reduced sediment thickness appeared. During the Maeotian time this area was narrow and apparently insignificant, but its width became several times larger during the Early Pontian and Late Pontian-Dacian time. Taking into consideration the southern migration of the basin, as previously discussed, we believe that the thin-sediment area from the southern periphery of the basin (hatched in Fig. 2.12) represents the region of southward extension of the Dacian Basin. Following the southward widening trend of the basin, the area with thin sediment extended only in the central and central-eastern periphery of the basin. Paleoenvironment in the Late Pontian Dacian Basin. According to Saulea et al. (1969), during the Late Pontian-Dacian in the northern, sub-Carpathian area of the Dacian Basin the cardiid shells are characteristically thick and large. In contrast, in the southern part of the basin, the mollusks associations consist of numerous small size specimens, with thin shells. These features indicate a shallow water environment with low relief coast and lower energy for the southern area of the Dacian Basin. 2.2.3. Nature of the southward extension process Previous interpretations considered the southward enlargement of the Dacian Basin as common transgression (Saulea et al., 1969; Papaianopol et al., 1987; Marinescu and Papaianopol, 1989). Here we discuss possible alternative interpretations. Processes of transgression. Transgressive events affected the Dacian Basin during the Late Neogene time. The sub-Carpathian coast of the Dacian Basin exhibits clear evidences for these processes. Late Neogene sedimentary deposits overlie directly Early Miocene or Paleogene deposits. The transgressive episodes are restricted to short periods of time, like Late Maeotian and Late Pontian (see Chapter 1.5). Based on information offered by the paleogeographic maps (Saulea et al. 1969) (Fig. 2.10), the southward enlargement of the Dacian Basin may be viewed as a long-term process, which progressed through the whole time-span of existence of
2.2. Dacian Basin paleogeographic changes FIGURE 2.12. Sediment thickness distribution during the process of southward extension of the Dacian Basin area. A. Sediment thickness distribution. B. Depocenters vs. extension zone. Isopachs simplified from Saulea et al. (1969). Southeastern part of the areas with thinner than 100 m sediments is marked as extension zone. Areas with thicker than 200 m sediments are considered (for the present purpose) as depocenters 55
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Dan C. Jipa, Cornel Olariu DACIAN B
Page 5: Dedicated to the memory of Prof. Gh
Page 8 and 9: NATIONAL INSTITUTE OF MARINE GEOLOG
Page 11 and 12: CONTENTS Foreword and Acknowledgeme
Page 13 and 14: Contents Chapter 7. The Point Bar F
Page 15 and 16: FOREwORD AND ACkNOwLEDgEMENTS The s
Page 17: PLATE 1. Location of the Dacian Bas
Page 20 and 21: 18 Chapter 1. Dacian Basin. General
Page 42 and 43: The analysis of the paleogeographic
Page 44 and 45: 42 Chapter 2. Dacian Basin paleogeo
Page 60 and 61: 58 FIGURE 2.14. Paleogeography and
Page 70 and 71: 68 Chapter 3. Sediment Thickness Di
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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104 Chapter 5. Littoral Sedimentary
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Fluvial sedimentation played a majo
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136 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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DACIAN BASIN - GeoEcoMar

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