Environmental Geology of the Avon-Heathcote Estuary

PhD thesis, University of Canterbury, New Zealand
Malcolm Macpherson

under construction go to www.macpherson.co.nz in the interim



Here are the individual photographs from my Figure 62, surface expressions of the anthropogenic mud layer (my unit C) deposited between 1850 and about 1900

Photograph A


Photo B


Caption for A and B. Plastic mud exposed in the sides of a shallow intertidal gully near the end of line 16, eastern high tide slopes (line 16 runs from Beachville Road, across the principal subtidal channel, to the southern end of the Brighton Spit at about Petrel Lane, off Rockinghorse Road. Line 16 was the southern limit of my study area.

This view is to the east north east, looking up the spit shoreline.

The dark arrows (at multiple locations marked 1, for example) show the eroding scarp of unit C, spade for scale, ebb flow (outgoing tide) is to the right (shown by arrow number 2), note coarse active sand on the burrowed mud surface, with lineation parallel to the ebb flow (at location 3 in photo A).


Photos C (above) and E (below) show unit C fibrous organic-rich plastic mud exposed immediately east of Sandy Point, view is south west into the north Heathcote Basin. CDB surveyor Tom Cleary for scale (probably on line 11). Note scarp of eroding mud at location 5, and the post at location 6, also shown in photo E. Unit C mud is intensively bored, and dips offshore (to the right in E) at a slightly lower angle than the current sediment surface. This strip of eroding sediment is hundreds of metres long, and extends well towards the shoreline.
Photo E
Photo D. Unit C sandy mud (location number 7) at the eastern end of line 10 (line 10 ends between Penguin Lane and Kingfisher Street on the estuary side of the Brighton spit). Note active (rippled) sand in the foreground, and the terrace-like top surface of the unit C mud layer, at a lower angle than the contemporary active surface.




Photo F. Olive plastic mud of unit C dug from beneath clean friable sand on line 10, near the location of core 36.


Photo G. Shelly organic-rich unit (C) mud exposed as a scarp (arrowed location 9) at the high water (HW) mark (arrowed location 10) near the east end of line 3, at the northeastern end of the estuary.

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