Chapter 5: Discussion 5.1 Introduction 5.1 Introduction
5.2.2 Local Correlation of Sub-Horizontal Sedimentary Layers
5.2.2.2 Group 2 – Units C, D, E & F
Firstly Units D and E will be examined. Units D and E are among the two largest sub-horizontal outcrops found in the Kerpini Fault Block. Additionally, as has been presented in Chapter 4, they are only separated by ~100m of recent soil. This is shown again here in Figure 5-2 as green circle #3. The image has been expanded to also include Unit C.
When comparing Units D and E, based on the observation on clast size and composition, they appear similar. However comparing the clast size within these two units may not be adequate for correlation as they highly likely have been measured in different beds. Yet, in Unit D the clast size was measured to 171mm and 127mm (Table 4-4) and in Unit E to 130mm (Table 4-5), which places them within a pebble/cobble range. Conversely both contain the consolidated sandstone clasts, have thicker sandstone layers than found in the dipping alluvial conglomerate in the Kerpini Fault Block, and show a flow direction with an eastward trend. They are, however, separated by recent soil (#3, Figure 5-2). Even so, it is with high confidence that Units D and E
93 are the same sediment, albeit at a slightly different elevation. However this elevation difference may be the result of erosion.
Figure 5-2: An expanded image from Google Earth to show the possible connection between the three units C, D and E.
The green circles are areas that were difficult to obtain good measurements. However due to their location in regards to the sub-horizontal, it is feasible that these are part of the sub-horizontal units.
Unit C (Figure 5-2) sits 400m WSW from Unit D, and as described in Chapter 4, has a larger mound/ridge of 14° north dipping sediment (C1) to its immediate east. Based on the thick layer of sandstone that was found on either side of the gulley separating Unit C from the mound (Figure 4-25), it is then assumed that C1 is possibly a section of Unit C that has slumped down creating the 10° difference in dip angle between the two. The second area, shaded in green on Figure 5-2 (C2), reveals very similar dip angles and direction as Unit C and C1. However C2 is not very well exposed and the dip measurements differ, given that this area is also assumed to be part of Unit C and has been possibly slumped or faulted4.
4 No faulting was observed. However one cannot rule out a fault that is sediment/sediment contact, as it will be more difficult to identify in the field than a sediment/basement contact.
94 With regards to the green circles (Figure 5-2), #3 was discussed earlier in this section in the possible connection between Units D and E. None of the circles (#1, #2 and #4) show indications of south dipping sediment. However neither do they fall within the range that has been used to define sub-horizontal layers. Given their vicinity to the sub-horizontal, it is a fair assumption that these may be part of the three (C, D and E) units. The final green circle, #5, lays in-between Unit E and the blue shaded basement that is described in 4.2.1 (Figure 4-3, Figure 4-4). This thin section of sediment has few exposed outcrops to indicate whether it is dipping or sub-horizontal, but again given the proximity to Unit E and the basement to the immediate east, it is believed that this too is part of this larger sub-horizontal unit.
Figure 5-3: Profile from Unit E in the west to Unit F in the east. Note the basement “tongue” that is separating these two units, also the exposed strip of basement that is found west of Kerpini Village. This image shows dipping sediment on the eastern side of Unit E; however it is possible that this sediment is part of the unit. The sediment found beneath, is believed to be dipping.
The final unit in this section is Unit F. Unit F differs from the three others described here as it is separated, not by recent soil, but by basement (from Unit E east to Unit F). It is also located at a higher elevation than the Units C, D and E, and there are no indications of in-situ consolidated conglomerate, alluvial or fluvial, between the two units. Figure 5-3 is a profile from Unit E to Unit F; this image shows the aforementioned basement that separates the two units.
This basement found between the units is believed to be a slump from the uplifted Dhoumena
95 Fault (Figure 4-3) that has slid south and thus removed any traces of sediment that could possibly link Unit E and F. The reason for this argument is that the red basement (Figure 4-4) appears in-situ, i.e. the bedding/layering in the radiolarite is still intact. Furthermore, conglomerate is found both underlying and overlying this basement on the western side (Figure 4-3). This conglomerate, found on the western edge, exhibits very erratic dip angles. In addition, on top of this basement “tongue” there are very large (>4x4m) conglomerate boulders scattered around, which appear to have broken off a larger structure. However, if this were an erosional feature, one would expect the sides of the larger conglomerate outcrops to be more scoured than jagged edged, as found here. Further evidence that may support the theory of a slump, and that can link the two units (E & F) across the basement “tongue” is seen in Figure 4-34. This image shows the assumed contact point where the conglomerate has interacted with the underlying basement. The argument to support this is that the clasts are angular to sub-angular in this outcrop, compared to the rounded to sub-rounded found in the overlying Unit F. Assuming that this is the contact point, the conglomerate must have flowed towards this point across the basement “tongue”, from Unit E, and interacted with the basement causing the angular clasts. Then as the flow of sediment continued from the west, the more rounded clasts were deposited on top of these lower-lying angular clasts.
Unit F also shows the same flow direction as that seen in Units D and E. When comparing the texture and appearance of Unit F, it shares more traits with Units D and E than it does with the dipping alluvial conglomerate. Additionally, the presence of a possible slump or landslide that has divided Unit F from Unit E is highly likely. Therefore it is believed that Unit F is part of the same sub-horizontal unit that is Units C, D & E.