DACIAN BASIN - GeoEcoMar

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180 Chapter 7. The Point Bar Facies in the Jilţ Quarry (Romanian Deposits) FIGURE 7.24. Paleocurrent directions measured in the point bar deposits from the Jilţ Quarry. Measurements based on cross-lamination orientation, mostly small and medium size
7.3. Mud drapes characters and distribution ■ the least frequently observed are the homogeneous clay beds, without sandy or silty lamination; ■ the most frequent is the clay drape type with relatively minor silt and sand laminae (Fig. 7.25 A); ■ the third type of mud drape includes a significant amount of silt and sand, which occurs as small lens-like bodies or as interfingering thin beds (Fig. 7.19 B, C and D) Usually, the mud drapes display parallel, sharp and smooth boundaries. The lower boundary is more rugged than the upper one. Irregular top surfaces of the thin clay beds have also been observed (Fig. 7.25 E and F). The internal lamination of the clayey beds is cut, indicating the erosional character of the upper surface. 7.3.2. The internal structure of the mud drapes Even though the clay intercalations studied are thin, their internal structure is variable and revealing. Characteristically, the internal structure elements show up in the lower half of the mud beds (Fig. 7.25 A). The upper (and middle) part of the strata represents the interval of parallel and rarely cross silty-clay lamination. Sometimes, sandy beds occur in the middle of the mud intercalation (Fig. 7.25 B), or (occasionally) they are distributed on the entire vertical column of the mud bed intercalations. Some mud beds have a lower interval with sand laminae and an upper interval with silty clay laminae (Fig. 7.25 A). The transition is gradual between the two lamination intervals, and the clay bed appears as fining upward. The mud drapes are closely connected with cross strata (current structures). Within the mud drapes unit, there are cross-bedded sand thin units, with clay material between the oblique sets of sand laminae (Fig. 7.25 D). Clayey material is sometime draping large troughs of cross strata (Fig. 7.10). It is common for the mud drapes to occur between current laminated structures (Fig. 7.25 E and F). 7.3.3. Mud drapes down-dip endings Types of clay drape ends. Beside the internal sedimentary structures, the nature of the mud drapes terminations represents an important feature. Some mud drapes end with a sharp, irregular outline. This is an erosional downdip termination of the mud drapes. The erosional characteristic is also revealed by the cut cross-laminae at the mud beds end (Fig. 7.26 A). Another type of mud drapes termination is the sharp, irregular, erosional end continued with a row of clay pebbles (Fig. 7.27 A). Other mud drapes terminate by pinching out of the clay bed. Some thinning mud drapes show features suggesting that the bed thickness reduction might be of erosional nature. 181
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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 132 and 133: 130 Chapter 5. Littoral Sedimentary
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Page 136 and 137: Fluvial sedimentation played a majo
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Page 158 and 159: The large and continuous rock expos
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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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Page 216 and 217: 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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