This adventure involves a 2.5 to 3 km walk along the beach to get to the site, and although one can get to the gz at any time, most of the way points, and much of the content of this Earth Cache, are only accessible at low tide. You would be advised to plan on spending about 3 hours to complete the physical aspect of this placement.
Wherever there is relevance to the required tasks found at the bottom of this description, the following appears in the text {TASK}
There is parking available at the nearby Entertainment Resort, at a nominal charge. As of June 2018 the charge was R25 per vehicle per day. Various concessions might apply.
The listed Way Points will take you to various aspects of this site. Some of the examples may not be that obvious at the listed co-ordinates, and you might have to examine the surroundings carefully to identify the focus of that way point.
Please do not remove or deface any aspect of this Heritage Site.
The area is usually deserted, and there is a wonderful setting for a picnic upon the beach in the adjacent bay. If you do enter the water, remember that there are no Life guards nor safety nets.
Please practice responsible geocaching!
WP 1
Facing inland, notice the course of the river. Take notice of the topography, and of the outline at the horizon, paying attention to irregularities and uniformity. Note the vegetation on both sides of the River.
WP 2
The start of the exposed Deposit. This relief fossil was possibly a Coastal Red Milkwood tree or Silver Oak, based on the bark identification. Notice the growth rings.
WP 3
An example of a petrified tree. Observe how the edge of the petrified tree has weathered when compared to a similarly exposed rock edge. Take note of the tubular burrowing in the tree trunk. This was the result of the gastropod Teredo, now extinct.
WP 4
This trace fossil has been identified as the shoulder blade of a Misasaur, a large marine Lizard about 12 to 14 meters long and 1.7 meters high. It is one of the very few indications that remain of Reptilian life in this area at that time.
WP 5
An Amonite shell fragment. When extrapolating the spiral shell, it is believed to have a diameter of 2 to 3 meters. There is another example about 5 meters West, upon the dune, buried within a meter of the sand.
At the listed co-ords, an example obviously created by the replacement process of Fossil creation can be found encased in the sandstone cliff. This recognisable shape has had mention in many papers since the discovery of this deposit by Henry Fynn in the late 1800's, but there has been no scientific validation to date. Can you identify the organism? Can you spot the head socket? And supporting evidence?{TASK}
And now for some explaining! Turning first to Fossils;
Fossils are the remains of any evidence of life made permanent by the Lithification process (turned to stone.)
This Lithification process can occur in several ways.
Encapsulation (also called Preservation).
The living matter, usually insect or seed, is covered with a substance that seals it from outside influence. For example the resins from some trees engulf an organism. The resin becomes Amber under pressure and the complete intact body within is preserved. So too with temperature. When an organism is frozen over, and the temperatures remain at subzero levels, the organism is preserved.
In Los Angeles, in North America, there is examples of organisms being encased in the tar created by the carboniferous sediments. Under pressure the tar turns to asphalt while the organism remains intact. A perfect example of an an organic body turned to stone.
In the last few Millennia, this process could have been used to immortalise significant leaders in Human society, using Desiccation or removal of all water (Drying Out). This is witnessed by the creation of the ancient Egyptian Mummies.
Replacement or Trace Fossils
This aspect of fossils relies on the Lithification process taking place upon the evidence of organic existence. So where an animal has walked and left footprints, for example. The mold of the footprint is used to cast a rock that would match the exact parameters of that footprint. And so too where an organism is covered, and although the decay of that organism is inhibited by limited oxygen exposure, there is a gradual decay of the organic matter. This vacant space, surrounded by already formed rock, is filled with mineral rich water usually rich in silicates, Calcite, Pyrite, or similar agents of Lithification. Over time the result is a form matching the outer texture of the organism, but the internal structure replaced by rock – of a differing and later origin to the housing rock.
Carbonation.
This process of creating Fossils is when an organism is covered by a sediment and held under pressure. All the mineral elements of the organism except Carbon are diffused or released, leaving the Carbon to be bonded with the adjacent rock elements. The consequence of this is that, on exposure several million years later, the lower rock face has an image or outline of the flattened shape of the original organism. {TASK}
Recrystalisation.
This process is perhaps the most purest forms of Fossil creation, recrystalisation occurs when a tiny organism, usually single celled, is subject to anaerobic conditions under pressure. Simply summarized, the atomic crystals that sustain life for these organisms are forced under pressure to react and reform, usually into larger and more binding structures. Their role in understanding our existence is critical, even although they are not visible to the naked eye.
Permineralization (also known as Petrification)
These fossils are created when the organism is covered entirely, either with sediment or water, or ash or similar. The organism begins an anaerobic decomposition process, which is a lot slower than the normal oxygen assisted decay. During this decomposition, the surrounding sediment and rock allows for minerals to permeate into the cell structure of the organism. These minerals use the oxygen of water to decay the lignin and cellulose of the organism's structure, and to replace it with compounds of lithification. When the organism has had all of it's structure replaced by these 'rock cells' we have a newly created miniralized or petrified organism. It is worth noting that the resultant fossil, in this case, is literally a stone equivalent of the organism; any cellular strength found in the organic structure has been duplicated in the rock structure. {TASK}
Over millions of years, the stone fossil will bear the influencing colouring of the abundant mineral used in permineralizing the organism. Thus we have petrified tree trunks with a red hue – due to a large exposure to Iron in the area. Petrified tree trunks with a blue/green hue - due to a large Copper content in the sediments. And so too for black – Carbon; pink/orange/yellow – Manganese; and ash/white - Calcium .
It must be remembered that these are ROCKS. They are not stone covered organisms.
Now that the terms are understood, we can step back and consider the geologic actions that might have occurred to produce the examples we have seen, here at this spot.
To do this, we need to go back to a time when all the land of this earth was in a solid lump. This lump of land we shall call PANGEA. Now about 300 Million Years Ago (Mya) Pangea split into two portions. These were named LAURASIA (in the now North) and GONDWALALAND in the South.
It is around Gondwalaland that our story starts.
Picture a ring of Fire spewing mountains all the way around the edge of a plot of land; A geological image of a pet's water dish. Around the edges are the bold and mighty Andes Mountains, the protruding Atlas range, the high Himalayan peaks, the soaring reaches of the Australian highlands, and the mystical but mighty Highlands of Antarctica. And all of these Bold uprisings spitting out Lava and dust, particles that remained in the air for days, weeks, even years; and then fell to ground and settled into a covering blanket of dust and sediment.
To that picture add the sand and silt blown off the high reaching peaks, the soil carried down the slopes by rainfall and ice, by loose soil vibrated down the slopes with the global tremor of the shifting foundation; all this deritrites collecting at the base of the encircling mountains.
Now take that picture in your mind, and wrap it around a sphere in your mind, for the earth is and always has been, shaped like a ball.
The difficulty you have, and the cracking up of your minds eye picture, is exactly what happened to Gondwala.
The base of the super continent began to break up. Pieces broke off to fit with the sphere shape of the globe. Around about 225 Mya, the piece of land we now know as South America, had broken away. The Antarctic and Australian land masses, although still co-joined, had severed off from the the mass of land, and were beginning their Honeymoon known as The Continental Drift. And still the basaltic lava and erosion deposits were collecting in what was left of the center of the ring of fire. And these things continued for many a million years – 125 of them in fact.
Our story gets relevant some 100 Mya during a time that is known as the Lower Cretaceous Period. During the late Jurassic Period, a flaw in the basement rock holding the mountains in place, developed. This flaw, known as a fracture zone, thrust what we now know as Madagascar away from the mainland and resulted in a fissure stretching from the now-a-days area known as the South Atlantic Basin right up the Eastern edge of (currently) Africa to the area just off the Eastern 'horn' of Africa, outside Southern Somalia. Several million years thereafter, the tether that held lower South America to Africa broke at the seam, in what we call the Falklands Agulhus Fracture Zone. This action resulted in the Karoo sandstone and basalt collected within the pan of Gondwalaland flexing and thinning out with the added space. With the emerging chasm being filled with the stagnant waters of the collected run-off, and the sediment being formed upon sediment, and upon more sediment, without any anchoring form to retain the run off, the section of land whereupon you now stand, as with all the land of this area resting on the new plate edge, began to incline toward the fault line. This was assisted by the increasing weight of the newly formed and rapidly growing Indian Ocean. The evidence of this can still be seen today in the unique monocline of the KZN topography.
The tilting toward the sea resulted in blocks of sandstone sediment breaking off, and sliding into the sea, creating the first of several marine sediments. Of course, the water run off was a lot more direct because of the slope, which meant that the eroding force of the rivers and streams was far more pronounced. It did not help reduce this 'pouring into the Ocean' effect when the upliftment of the Drakensberg mountains rose.
And this period became known as the Age of Reptiles, but there is little evidence of that along the Eastern Seaboard. Most fossils and remains of that age are held in the sandstone and shale sedimentary beds. As we have just learned, in this neck of the woods these strata slipped into the sea to come to rest upon the continental shelf, courtesy of the Gondwala breakup.
And so we have this Earth Cache. A privileged scratch upon the fabric of time,
allowing us to catch a glimpse of all that came to pass
so many millions of years ago.
Please enjoy this rare opportunity.
REFERENCES:
South African Geology, E.H.L. Schwarz 1912
http://sciencing.com
www.fossils-fact-and-finds.com
http://z11.invisionfree.com/fossils/index.php
Sedimentary Geology vol 107 issue 1-2 Dec 1996 (pg 83-97)
KZN Tourism Factsheet: The Geography of Kwa-Zulu Natal
Palaeontological Technical Report for Kwa-Zulu Natal, by Dr Gideon Groenewald 2012
In order to claim (or at least retain) the find, the following Tasks should be carried out. Submit your response for every finding team to the Cache Owner via the message facility of the app. Failure to respond within 14 days may result in your Found It log being deleted without notification.
The evaluation of the responses is at the absolute discretion of the CO.
Mzamba Cretaceous Deposit
Activity Sheet
Tasks:
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Fossils and the various types of fossils play an important role in understanding our history. With that in mind, and given what you have just observed, how many different forms of fossils could you find? Not the number of fossils (phew!) but how many different types of fossils, and could you name them?
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At WP 3 there is a petrified tree trunk laying atop a basalic rock. Move around so that you can see the edge of the fossil and also the edge of the supporting rock. Is there a difference between the two edges? If so, why do you think it is so, and if there is no difference, why do you think that is so?
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Name the animal or plant that is depicted at the GZ set against the rock.
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In your own words, describe briefly how you think this deposit came into being.
Applied Knowledge
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(Optional) Looking around at the path you have followed, can you describe any evidence to support your response to 4.
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(Optional) You may wish to capture a picture of your team amid the fossils and post it with your log.
You may log the find before submitting the response, but please ensure the response is submitted within two weeks. Submit all responses to the CO via the message service within the App.
Invaluable guidance from Benny Mbotho on 063 03 00654