Sediment accumulation and Holocene - OzCoasts

More documents

Recommendations

Info

Sediment accumulation and Holocene evolution of the Fitzroy River lower floodplain layer. This lower clay probably represents mangrove deposits, given the location of the boreholes adjacent to the present tidal creeks. Unfortunately these previous studies did not involve any dating of the cores or cuttings. Therefore, it is not possible to establish the thickness of the Holocene sequence. However, we can assume that the upper clays are the primary Holocene deposit, based on the ages for the Geoprobe cores (FK402 and FK404). The depth of clays in all the floodplain cores is given in Table 7. We have used this data to determine the average thickness of floodplain sediments in order to calculate the mass of sediment that has accumulated during the Holocene. The thickness of the floodplain sediments varies considerably between the north of the river and the south, therefore the floodplain is split into two regions for the sediment accumulation calculations (Figure 10). The thickness of the floodplain clay near Rockhampton is 5.5 m, and in the other northern floodplain sites it ranges from 3–6 m, with the average thickness of 4 m in cores that penetrated the unit. However, some cores did not penetrate through this clay. Therefore, 4 m must be a minimum value and we assume an overall average thickness of 5 m for the northern area (Table 7). In the south, the thickness varies from 5–22 m, with an average thickness of 13.5 m (Table 7). The borehole data also provide details on the stratigraphic succession of facies within the floodplain. Two simplified cross sections that integrate all the bore and core data are shown in Figure 11 26
Sediment accumulation and Holocene evolution of the Fitzroy River lower floodplain Table 7: Thickness of upper clays in the northern and southern floodplain. Cores in northern floodplain Depth of muds Cores in southern floodplain Depth of muds FK400 >3.6 m FK400 >3.6 m FK401 3.0 m D1^ 15 m FK402 4.5 m D2^ 19 m FK403 2.3 m D3^ 10 m FK404 5.7 m D4^ 15 m FK405 >3.5 m D5^ 18 m YAS33* > 5 m D6^ 14.5 m YAS34* 3.5 m D7^ 12.5 m YAS35* > 5 m D8^ 12 m YAS36* 2.5 m D9^ 12 m YAS37* 3.5 m D11^ 18 m YAS38* 3.5 m D12^ 5 m YAS39* 6 m D13^ 11 m YAS40* 3 m D14^ 10 m Site 484* 5.5 m D17^ 18 m Site 485* 6 m D19^ 22 m Site 486* 3.5 m X1 + 12.5 m Site 487* 1 m X3 + 9 m Site 488* > 5.5 m X4 + 12.5 m Site 490* 6.5 m X8A + 15 m D15^ 7 m X9 + 14 m Average for north 4 m X11 + 13 m X14 + X15 + X16 + X17 + Site 1 + Site 2 + Site 3 + Site 4 + PB1 # 15.5 m 16 m 17 m 12 m 13 m 12 m 15 m 12.5 m 12 m 27
Page 3 and 4: Sediment accumulation and Holocene
Page 37: Sediment accumulation and Holocene

Sediment accumulation and Holocene - OzCoasts

Create successful ePaper yourself

Delete template?

Save as template?