Journal of Paleontology, 91(6), 2017, p. 1102–1122 Copyright © 2017, The Paleontological Society 0022-3360/17/0088-0906 doi: 10.1017/jpa.2017.66
Post-glacial Foraminifera of the incised Yangtze paleo-valley and paleoenvironmental implications
Xue Ke,1 Baohua Li,2* Zongyan Zhang,3 Yi Wei,4 Fei Hu,1 Dongwen Fan,1 Li Sun,1 Jianlei Xie,5 Junjie Yu,6 and Huazhou Yao3
1Institute of Geological Survey, China University of Geosciences, Wuhan, 430074, Peoples Republic of China ⟨
xue_ke@cug.edu.cn⟩,
⟨
1154809313@qq.com⟩, ⟨
458704798@qq.com⟩, ⟨
280766256@qq.com⟩ 2Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, Nanjing, 210008, Peoples Republic of China ⟨
bh-li@nigpas.ac.cn⟩ 3Wuhan Center, China Geological Survey, Wuhan 430223, Peoples Republic of China ⟨
conodonts@163.com⟩⟨
Ycxc2009@126.com⟩ 4Safety Engineering College,North China Institute of Science&Technology, Langfang 065210, Peoples Republic of China ⟨
weiy712@gmail.com⟩ 5Geological environment research, Shanghai Institute of Geological Survey, Shanghai 200072, Peoples Republic of China ⟨
45118880@qq.com⟩ 6Nanjing Center, China Geological Survey, Nanjing 210016, Peoples Republic of China ⟨
25320701@qq.com⟩
Abstract.—Three gravity cores (LZK1, ZKA4, and CSJA6) from the incised Yangtze paleo-valley comprise a thick sequence of the post-glacial deposit. Nineteen genera (26 species) of the benthic foraminifers are described from these cores, with detailed down-core foraminiferal variations to investigate their paleoenvironmental implications. Three foraminiferal assemblages are recognized for the lower, middle, and upper parts of the cores respectively. The lower part is dominated by Ammonia beccarii var. and Florilus decorus with lower abundance and diversity. In the middle part, the foraminifers are abundant and diverse, dominated by both Ammonia beccarii var. and Elphidium advenum. Cavarotalia annectens, Pararotalia nipponica, and porcellaneous benthic foraminiferal forms are always present, sometimes abundant. The upper part is characterized by the Ammonia beccarii-Elphidium magellanicum assemblage, except for the Core ZKA4, which is barren of foraminifers in this interval. AMS 14C dates and foraminiferal assemblages both confirm that the transgression-regression sequence in these cores belongs to the “Ammonia transgression” during the Holocene. In addition to documenting the post-glacial sea-level fluctuations, the benthic foraminifers also reflect a warmer climate during the early–middle Holocene. The foraminiferal differences among the three cores can be used to interpret the influence of seawater during the post-glacial sea-level fluctuations. The area in the vicinity of Core ZKA4 was affected by marine water only during the middle Holocene, which was much shorter than the areas of the other cores.
Introduction
Sediments of the coastal plains and the continental shelves record the dynamic history of the shoreline migration caused by the ~120m sea-level changes during the Quaternary (Fleming et al., 1998). Through regional micropaleontological and stratigraphic comparisons in the sedimentary cores from East China, four major marine transgressions have been recognized during the late Pleistocene. The last one, post-glacial “Ammonia transgression”,is the most notable and widespread along the coastline (Wang et al., 1981). Numerous boreholes have been drilled and studied in various parts of East China over the last several decades (Lin, 1979; Wang andMin, 1979; Li et al., 1988; Zhu and Lin, 1990; Chen and Stanley, 1995; Stanley and Chen, 1996; Wang et al., 2002; Shu et al., 2010; Xiong et al., 2010; Wang et al., 2012). However, introduction of old carbon and reworking resulted in less-reliable dates, which has hampered further study on the glacial-interglacial environmental changes in East China (Stanley and Chen, 2000).
* Corresponding author
Due to the lower last glacial sea level and excavation of
previous marine sediments, the deeply incised Yangtze paleo- valley received a significant amount of post-glacial deposits, up to 80mthick in this region (Li and Wang, 1998; Li et al., 2000), which provides an excellent opportunity for reconstructing the post-glacial environmental changes in East China. In this study, benthic foraminiferal assemblages are repor-
ted from three cores of the incised Yangtze paleo-valley. The foraminiferal fauna can be correlated with records of previous studies in the Yangtze Delta region. Based on reliable AMS 14C dates, the high-resolution foraminiferal data presented here provide new evidence for post-glacial variations in climate and depositional environments.
Geological setting
The Yangtze Delta has been developing in a sedimentary basin formed in association with the Quaternary neotectonic orogeny in East China (Guo et al., 1997; Wang et al., 2008). The Quaternary stratigraphic sequence of the Yangtze Delta is up to
1102
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68 |
Page 69 |
Page 70 |
Page 71 |
Page 72 |
Page 73 |
Page 74 |
Page 75 |
Page 76 |
Page 77 |
Page 78 |
Page 79 |
Page 80 |
Page 81 |
Page 82 |
Page 83 |
Page 84 |
Page 85 |
Page 86 |
Page 87 |
Page 88 |
Page 89 |
Page 90 |
Page 91 |
Page 92 |
Page 93 |
Page 94 |
Page 95 |
Page 96 |
Page 97 |
Page 98 |
Page 99 |
Page 100 |
Page 101 |
Page 102 |
Page 103 |
Page 104 |
Page 105 |
Page 106 |
Page 107 |
Page 108 |
Page 109 |
Page 110 |
Page 111 |
Page 112 |
Page 113 |
Page 114 |
Page 115 |
Page 116 |
Page 117 |
Page 118 |
Page 119 |
Page 120 |
Page 121 |
Page 122 |
Page 123 |
Page 124 |
Page 125 |
Page 126 |
Page 127 |
Page 128 |
Page 129 |
Page 130 |
Page 131 |
Page 132 |
Page 133 |
Page 134 |
Page 135 |
Page 136 |
Page 137 |
Page 138 |
Page 139 |
Page 140 |
Page 141 |
Page 142 |
Page 143 |
Page 144 |
Page 145 |
Page 146 |
Page 147 |
Page 148 |
Page 149 |
Page 150 |
Page 151 |
Page 152 |
Page 153 |
Page 154 |
Page 155 |
Page 156 |
Page 157 |
Page 158 |
Page 159 |
Page 160 |
Page 161 |
Page 162 |
Page 163 |
Page 164 |
Page 165 |
Page 166 |
Page 167 |
Page 168 |
Page 169 |
Page 170 |
Page 171 |
Page 172 |
Page 173 |
Page 174 |
Page 175 |
Page 176 |
Page 177 |
Page 178 |
Page 179 |
Page 180 |
Page 181 |
Page 182 |
Page 183 |
Page 184 |
Page 185 |
Page 186 |
Page 187 |
Page 188 |
Page 189 |
Page 190 |
Page 191 |
Page 192 |
Page 193 |
Page 194 |
Page 195 |
Page 196 |
Page 197 |
Page 198 |
Page 199 |
Page 200 |
Page 201 |
Page 202 |
Page 203 |
Page 204 |
Page 205 |
Page 206 |
Page 207 |
Page 208 |
Page 209 |
Page 210 |
Page 211 |
Page 212 |
Page 213 |
Page 214 |
Page 215 |
Page 216 |
Page 217 |
Page 218 |
Page 219 |
Page 220 |
Page 221 |
Page 222 |
Page 223 |
Page 224 |
Page 225 |
Page 226 |
Page 227 |
Page 228 |
Page 229 |
Page 230 |
Page 231 |
Page 232 |
Page 233 |
Page 234 |
Page 235 |
Page 236 |
Page 237 |
Page 238 |
Page 239 |
Page 240 |
Page 241 |
Page 242 |
Page 243 |
Page 244 |
Page 245 |
Page 246 |
Page 247 |
Page 248 |
Page 249 |
Page 250 |
Page 251 |
Page 252 |
Page 253 |
Page 254 |
Page 255 |
Page 256 |
Page 257 |
Page 258 |
Page 259 |
Page 260 |
Page 261 |
Page 262 |
Page 263 |
Page 264 |
Page 265 |
Page 266 |
Page 267 |
Page 268 |
Page 269 |
Page 270 |
Page 271 |
Page 272 |
Page 273 |
Page 274 |
Page 275 |
Page 276
