Perfil del cuerpo docente de la Facultad de Educación de la UFMG

The first Timeslice (Fig. 4.9A) correlates the oldest and deepest remnant channel complex of C2 age recorded on the CD Ridge (CC1, Figs. 4.4 and 4.7) to the deepest and oldest channel complex on the northern limb of the Baviaans syncline (CC1 in Fig. 4.8). The low degree of asymmetry of the remnant complex preserved on both limbs of the syncline suggests that this channel complex had a low degree of sinuosity. The 30+ m of incision on this channel complex suggests that it was mostly erosionally confined. Any genetically related levee deposits have been removed by later channel cuts.

The cross-sections for Timeslice One (Figs. 4.10A and 4.11A) show the channel complex erosion surface down-cutting into the B/C interfan on the southern limb

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with inferred small, symmetrical external levees adjacent to it (Fig. 4.10A). The complex shows similar features on the northern limb but with basal erosion reaching just above the B/C interfan (Fig. 4.11A).

4.7.1.2

Timeslice Two – CC2

CC2 (Fig. 4.9B) shows the second deepest and oldest complex preserved as two remnants on the CD Ridge, highlighted as CC2 in Figure 4.7, both of these directly overlie the CC1 complex correlated in Timeslice One. These channel complex remnants are correlated to the channel complex mapped out 8.5 km to the ENE near the West Dump on the northern limb of the syncline (CC2, Fig. 4.8). The asymmetry of the channel complex, with its eastward stepping constituent channel elements on the CD Ridge and the preservation of several channel margins preferentially on the western side of the complex on the northern limb, implies a degree of sinuosity.

The cross-section of Timeslice Two (Figs. 4.10B and 4.11B) on the south limb shows two remnant channel complexes, both of which incise to the base of Unit C, and the most western complex is relatively younger than the eastern. Although no longer preserved, we interpret asymmetric levees adjacent to these channel complexes, with the larger external levee to the west. However, the northern limb shows a single symmetrical channel complex that incises to below the base of Unit C; it is suggested that the two channel complexes identified on the southern limb are undifferentiated on the north limb. Thick external levees are inferred to have confined the CC2 complex, possibly aggrading with it. A crevasse splay is present in the middle of the western external levee as it is captured on the outcrop correlation panel (Fig. 4.8), its position in the middle of the external levee suggests that the channel complex and the external levees aggraded quasi-synchronously.

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4.7.1.3

Timeslice Three – CC3

The third Timeslice (Fig. 4.9C) shows the correlation of a C2 aged channel complex adjacent to the D-slope valley on the CD Ridge (CC3, Figs. 4.4, 4.5, 4.6 and 4.7) where constituent channel elements show an eastward stepping trajectory, with channel margin material being preferentially preserved to the west. This channel complex has been correlated to a channel complex preserved at the Old Rubbish Dump exposure (CC3, Fig. 4.8), where channel elements record a similar eastward stepping trajectory with extensive channel margin material also preserved towards the west. Both channel complexes step east and downcut to the stratigraphic level of Sub-unit C1.

The asymmetry and internal eastward migration of channel elements within the CC3 channel complexes suggests that external levee deposits associated with these channel complexes will be asymmetric, with a thicker levee to the east on both limbs of the syncline. At this time, it is most likely that the external levees on the southern limb of the syncline were deposited to their furthest extent.

The cross-section reconstruction for Timeslice Three on the southern limb of the Baviaans syncline shows how a channel complex partly truncates the older, eastern CC2 channel complex, again, incising to the base of Unit C. Individual channel elements in the CC3 channel complex are eastward stepping with higher rates of channel preservation towards the east. On the northern limb, this same deeply incised and eastward stepping channel element trend is present. It is inferred that high, asymmetric external levees bound the channel complex, with the higher external levee situated on the eastern margin (on both limbs of the syncline) due to flows preferentially overspilling to the east as a consequence of the eastward stepping trajectory of the individual channel elements.

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4.7.1.4

Timeslice Four – CC4

The fourth Timeslice through C2 (Fig. 4.9D) shows the correlation of the large, western CC4 channel complex on the CD Ridge (Fig. 4.7). This complex incises into the westernmost exposure of the CC3 channel complex, completely removing any related external levee deposits. The lack of exposed channel margin deposits and channel element scale surfaces means that the geometry of this channel complex has not been fully constrained. It has been correlated to the youngest, asymmetric channel complex cropping out at the Old Rubbish Dump (CC4, Fig. 4.8) on the northern limb. The asymmetry of constituent channel elements here suggests that the channel complex was sinuous in planform, as depicted in the palaeogeographic map.

Topography on the CC3 eastern external levee on the south limb of the syncline is likely to have acted to partially confine the eastern external levee of the CC4 channel complex, making it a ‘confined external levee’, therefore, the eastern levee has been shown in pale green, confined by the CC3 eastern external levee crest line. The western external levee was not confined so it has been shown to cover the entire study area. This pattern is extended towards the northern limb, with the eastern CC4 external levee inferred to have been confined by the existing topography created by the eastern external levee of CC3, whilst the CC4 western external levee is wholly unconfined.

The cross-sections of Timeslice Four show that CC4 is preserved as a series of remnant channel elements on the CD Ridge, with a westward stepping trajectory, however as channel margin material has not been preserved for this channel complex, its geometry here is difficult to constrain. CC4 has been interpreted to correlate to the youngest channel complex exposed at the Old Rubbish Dump (CC4, Fig. 4.8), an asymmetric channel complex, with the steeper cut towards the west. On both limbs of the syncline, CC4 incised through part of CC3 cutting down to the

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base of Unit C, removing older external levees genetically related to earlier channel complexes.

It is not known if the external levees of CC4 on the CD Ridge were asymmetric. The sketch indicates that a thick eastern external levee on the south limb constructed during Time Three acted to confine the Time Four eastern external levee. The asymmetry of the channel complex on the northern limb suggests that the external levees adjacent to that channel complex are likely to have been asymmetric, with a thicker western levee representing an outer bend. As with the southern limb, the reconstructed cross-section for the northern limb suggests that the eastern external levee of Time Three was high enough to act as a confinement surface to the Time Four external levee.

4.7.1.5

Timeslice Five – CC5

CC5 shows the palaeogeographic interpretation of the westernmost C2-aged channel complexes recorded on the CD Ridge and on the northern limb of the syncline opposite Baviaans Farm (Fig. 4.9E). These channel complexes are interpreted to correspond to each other as both sets of constituent channel elements record prolonged and preferred western stepping, with extensive channel margin deposits preserved on both limbs of the syncline (CC5, Figs. 4.7 and 4.8). At this time, it is likely that a ‘confined external levee’ was deposited towards the east, with a large external levee constructed on the western margin. The map shows this channel complex as part of a bend, with the outer bend to the west.

The palaeogeography map of Timeslice Five shows that the channel complexes are once again flowing from S-to-N, where CC5 is preserved as the most westerly cropping out channel complex on both the northern and southern limbs. CC5 is present as a westerly migrating complex of channel elements with increased channel preservation westwards. As with the older asymmetric migrating channel

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complexes, it is likely that the higher external levee was on the side that the channel elements were migrating towards, so in this case, on the western side. It is suggested that the thick eastern external levee constructed during Time Three on the southern limb of the syncline, confined the eastern external levee associated with CC5. On the northern limb, the overspilling flows depositing on the eastern external levee are unconfined resulting in the external levee of Timeslice Five onlapping the western external levee of Time Four, helping to create a cryptic levee history for the northern external levee.

4.7.1.6

Timeslice Six – CC6

CC6 is the youngest channel complex recorded on the CD Ridge (CC6, Figs. 4.4, 4.5, 4.6 and 4.7) and in Bav 1a (Fig. 4.9F). At outcrop this complex is characterised by vertically stacked aggradational channel elements confined by internal levee deposits (green on the palaeogeographic map). CC6 is correlated to the complex exposed at the Whaleback on the northern limb of the syncline (CC6, Fig. 4.8). The channel complex at the Whaleback is asymmetric and is positioned high within the external levee. The asymmetry of the channel margin deposits indicates that these channel elements had a degree of sinuosity, so the channel complex planform has been sketched as sinuous in the palaeogeographic map. Internal levees overlying a Timeslice Six erosion surface confining the late stage aggradational channel complex crop out on both limbs of the syncline. The channel complex on the northern limb has a steeper margin to the east, so the map has been constructed to show that the channel is erosional and external levee confined to the eastern margin compared to confinement by internal levee on the western margin.

The cross-sections constructed for CC6 (Timeslice Six) on the CD Ridge illustrate how it incised into the most eastern area of the CC4 channel complex and the most western part of the CC3 channel complex, before aggrading vertically, confined by internal levees (Hodgson et al., 2011), which were themselves confined by older

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external levees constructed during Timeslice Three and Timeslice Five, to the east and west respectively. No proximal external levees associated with this channel complex have been preserved due to erosion and incision by later channel complexes and the Unit D slope valley.

The cross-section of the northern limb shows CC6 as a highly erosive channel complex that incised through external levee deposits, constructed during Time Two to Time Five, to the stratigraphic base of Unit C. It is shown to be confined by external levees to the east that onlap onto external levees constructed during Time Four and by internal levees to the west. This internal levee was confined within the Time Six erosion surface and by the high external levee constructed to the west during Time Five.

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Figure 4.9: A series of palaeogeographic maps, reconstructed using correlations between channel complexes identified on the north and south limbs of the Baviaans syncline. Small inset correlation panels from Figures 4.7A and 4.8A are shown above and below the maps: A) The oldest channel complexes (CC1) observed in the study area; B) CC2; C) CC3; D) Reconstructed palaeogeographic interpretation correlating CC4 across the study area; E) CC5; F) The youngest channel complex (CC6) (See Enclosure 11 for enlarged version).

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Figure 4.10: A series of cross-sections constructed combining observations from the CD Ridge panel (Fig. 4.7) and the palaeogeography maps of Figures 4.9 correlations, flattened on the B/C Interfan as a datum: A) Reconstructed cross-section for Time One; B) Reconstructed cross-section for Time Two; C) Reconstructed cross-section for Time Three; D) Reconstructed cross- section for Time Four; E) Reconstructed cross-section for Time Five; and F) Reconstructed cross-section for Time Six (See Enclosure 12a for enlarged version).

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Figure 4.11: A series of cross-sections

constructed combining observations from the north limb of the

Baviaans syncline

(Figure 8) and the palaeogeography maps of Figure 4.9A-F, flattened on the B/C Interfan as a datum: A) Reconstructed cross- section for Time One; B) Reconstructed cross- section for Time Two; C) Reconstructed cross- section for Time Three; D) Reconstructed cross- section for Time Four; E) Reconstructed cross- section for Time Five; and F) Reconstructed cross-section for Time Six (See Enclosure 12b for enlarged version).

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4.8 Discussion