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160 Chapter 7. The Point Bar Facies in the Jilţ Quarry (Romanian Deposits) FIGURE 7.5. Jilţ South Quarry during the summer of 1991. A - The two mining fronts where the point bar deposits crop out. B - The mining front A13. C - Drainage ditch at the E13 level, exposing the lower part of the fine-grained sand facies
7.2. The sedimentological description of the Jilţ point bar deposits 7.2. THE SEDIMENTOLOgICAL DESCRIPTION OF THE JILţ POINT BAR DEPOSITS The dominantly sand deposits between the lignite beds VII and VIII are sub-divided by three thin gravel beds (Fig. 7.16). The inclined stratification deposits are delineated at their base by the third gravel bed. The upper limit of the point bar deposits is marked by a thin lignite layer (25-30 cm), which represents a minor coal episode preceding the main coal bed VIII. Three facies have been distinguished in the Jilţ point bar deposits: silty-clay, fine and very fine grained sand and medium and coarse grained sand facies. The three facies are partly superposed and partly transitional. Distinctive sedimentary structures are characteristic for each facies. 7.2.1. The upper, silty-clay facies The silty-clay facies (Fig. 7.6) makes up the upper part of the inclined stratification unit in the Jilţ Quarry. Immediately under the thin lignite/humic clay bed (Fig. 7.6 A), purely clay deposits occur (Fig. 7.6 B). This is a 0.5 to 1 m thick horizon, with lateral extent over the point bar deposits. Rootlets coming from the thin coal bed can be observed in the clay deposit. The dominant character of the clay is the lack of internal stratification. This unit will be called the upper homogenous clay subfacies. Under the upper homogenous clay, there is a silty-sand to clayey-silt interval. The sand content is higher in the lower part of the interval, which becomes clayeysilt towards the upper part. This is the silty-clay subfacies. The internal sedimentary structures of these deposits are represented by parallel laminations and bioturbation with low intensity. Large-scale inclined bedding is visible in the lower part of the silty-clay facies (Fig. 7.6). The large scale structure occurs as mud drapes which extend into the fine and medium-grained sand from the lower levels. There is also a set of silty inclined beds (or large scale current bedding) which develops at the upper part of the point bar, in the upper silty clay facies (Figs. 7.21; 7.23). Homogeneous fine sand lens-like small bodies are occasionally observed in the clayey sediments under the coal bed (Fig. 7.7 A). This sandy material was injected from the lower part of the point bar through clastic dikes (Figs. 7.7 B; 7.18 C). 7.2.2. The fine and very fine-grained sand facies The middle part of the point bar sequence consists of a sand accumulation of fine and very fine grain size, occurring under the silty-clay deposits. This is an important subdivision of the Jilţ point bar deposit, because it displays most of the inclined stratification features. A very fine-grained sand facies with small scale current lamination (Fig. 7.8) develops at the upper part of this accumulation. 161
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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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58 FIGURE 2.14. Paleogeography and
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68 Chapter 3. Sediment Thickness Di
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Sedimentation in the brackish-water
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84 Chapter 4. Dacian Basin Physiogr
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94 Chapter 5. Littoral Sedimentary
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Page 112 and 113: 110 Chapter 5. Littoral Sedimentary
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Page 192 and 193: 190 Chapter 8. The Paleoenvironment
Page 200 and 201: The evolution and architecture of a
Page 202 and 203: 200 Chapter 9. Source-Areas in the
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210 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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