DACIAN BASIN - GeoEcoMar

More documents

Recommendations

Info

110 Chapter 5. Littoral Sedimentary Environment in the Dacian Basin FIGURE 5.19. Hummocky cross-lamination structures alternating with smaller-size sedimentary structures, suggesting alternating weather conditions. Drawing after a picture. Late Maeotian, Bizdidel River (Pucioasa, Dâmboviţa County)
5.2. Shoreline sedimentation environment in the Dacian Basin 5.2.3. Shell beds in the Dacian Basin shoreline environment In the northern Dacian Basin area, between Putna River and Prahova River, on the sub-Carpathian margin of the basin, the presence of a distinctive Late Sarmatian (s. l.) calcareous deposit was signaled by Pană (1966) and Saulea et al. (1969). It consists of accumulations of Mactra shells, making up layers of various thicknesses, associated with claystone and sandstone beds. Brustur et al. (2005) specify that the accumulated shells belong to the same taxonomic unit or even to the same species of bivalve mollusk. Shell accumulations from the Late Sarmatian (s. l.) deposits have been investigated at the Râmnicu Sărat River geological section (north of the Jitia de Jos village). The shell beds consist of mostly unbroken Mactra shells included in a sandy matrix. In some cases the bedding is evidenced by alternating bands of sand and shells. In the outcrop at the north of Jitia de Jos, the thickest shell layer displays an internal inclined bedding (Fig. 5.20). The single Mactra shells show a preferential orientation with the convex side of the shells pointing upward. This orientation and the inclined sedimentary structure indicate that the shell accumulation is of detrital origin, resulting articulated current transport. The presence of Mactra specimens with the two valves articulated, in the living position, indicates that the shells have not been carried for long distances. In the outcrop area located on Râmnicu Sărat River, the internal current structure of the shell layers consists of a single set of inclined beds. Therefore, the entire mass of shells was displaced during a single transport episode. Considering the shell bed thickness of several tens of centimeters, the shell accumulation required a high energy transport agent. Several sandstone beds with wave ripples (Fig. 5.3 B) have been observed in the sedimentary succession which includes the investigated shell layer. This is a clear indication of the shoreface or nearshore environment of the shell accumulation. It is likely that storm-generated currents have been the agent able to transport, concentrate and accumulate the shells. The inclined internal structure of the shell beds (Figs. 5.20 A and B) could also represent a storm generated feature. The sandy matrix of the Late Sarmatian (s. l.) shell beds from the Râmnicu Sărat River (Fig. 20 D and E) occurs in variable quantity. It has been observed that, practically, all shells from low matrix shell beds are orientated with their convex side up (Fig. 20 D). In contrast, in the layers with abundant sandy matrix, the shells display variable positions. Consequently, it appears that the amount of matrix could indicate the relative energy level of the currents which transported and concentrated the shells. 111
Page 1:
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 22 and 23:
Page 24 and 25:
Page 26 and 27:
Page 28 and 29:
Page 30 and 31:
Page 32 and 33:
Page 34 and 35:
Page 36 and 37:
Page 38 and 39:
Page 40 and 41:
Page 42 and 43:
The analysis of the paleogeographic
Page 44 and 45:
42 Chapter 2. Dacian Basin paleogeo
Page 46 and 47:
Page 48 and 49:
Page 50 and 51:
Page 52 and 53:
Page 54 and 55:
Page 56 and 57:
Page 58 and 59:
Page 60 and 61:
58 FIGURE 2.14. Paleogeography and
Page 62 and 63: 60 Chapter 2. Dacian Basin paleogeo
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
Page 136 and 137: Fluvial sedimentation played a majo
Page 138 and 139: 136 Chapter 6. Upper Neogene Fluvia
Page 158 and 159: The large and continuous rock expos
Page 160 and 161: 158 Chapter 7. The Point Bar Facies
Page 162 and 163:
160 Chapter 7. The Point Bar Facies
Page 164 and 165:
Page 166 and 167:
Page 168 and 169:
Page 170 and 171:
Page 172 and 173:
Page 174 and 175:
Page 176 and 177:
Page 178 and 179:
Page 180 and 181:
Page 182 and 183:
Page 184 and 185:
Page 186 and 187:
Page 188 and 189:
Page 190 and 191:
Page 192 and 193:
190 Chapter 8. The Paleoenvironment
Page 194 and 195:
Page 196 and 197:
Page 198 and 199:
Page 200 and 201:
The evolution and architecture of a
Page 202 and 203:
200 Chapter 9. Source-Areas in the
Page 204 and 205:
Page 206 and 207:
Page 208 and 209:
Page 210 and 211:
Page 212 and 213:
Page 214 and 215:
10.1. SEDIMENT ACCUMULATION AREAS I
Page 216 and 217:
214 Chapter 10. History of the Daci
Page 218 and 219:
Page 220 and 221:
Page 222 and 223:
Page 224 and 225:
Page 226 and 227:
Page 228 and 229:
Page 230 and 231:
Page 232 and 233:
230 Chapter 11. From Brackish-Marin
Page 234 and 235:
Page 236 and 237:
Page 238 and 239:
Page 240 and 241:
Page 242 and 243:
Page 244 and 245:
Page 246 and 247:
Page 248 and 249:
Page 250 and 251:
Page 252 and 253:
Page 254 and 255:
Page 256 and 257:
Page 258 and 259:
Ai n s w o r t h r. B., Cr o w l e
Page 260 and 261:
258 References hA m o r, g., et al.
Page 262 and 263:
260 References mA C A r o V iC i, n
Page 264 and 265:
262 References ră d A n, s.C., 200
Page 266:
264 References VAsilieV, i., Kr iJ
show all

DACIAN BASIN - GeoEcoMar

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?