Searching for Ediacara: A Visit to South Australia to Find Ediacaran Fossils

Searching for Ediacara:

A Visit to South Australia to Find Ediacaran Fossils

Martyn Smith, 3/12/2016 Lawrence University

Abstract: The subject of this paper is the Ediacara biota that was widespread on the earth 600-542 millions years ago (Monastersky 1996). Having decided on this subject it was easy to find books such as The Rise of Animals: Evolution and Diversification of the Kingdom Animalia (2007) which treats the Ediacaran fauna, but as I began to read about these enigmatic organisms I was struck by the extent to which our knowledge is rooted in actual sites. The key site for the Ediacaran fossils, from which Martin Glaessner first drew parallels with finds from elsewhere, was the Ediacara Hills in South Australia (1959). I began to grow frustrated with my inability to see the site itself, and I plotted a way that I might experience this site, which is sacred for anyone with reverence for the story of Life. Though I didn’t have time or money to actually travel to South Australia, I decided to see how close I could get to an actual visit using the images and maps available on the Internet. This resulting graphic travel narrative is an example of imagined travel (that is: I didn’t actually go to the site). But it turned out to be true that the more I came to understand this landscape, the better I was able to understand the arguments I was encountering in scientific papers.

The flight to Adelaide, Australia from Ohare took a full 24 hours.

On our descent into Adelaide I took out my cell phone and took a few photos. To the north I saw low hills extending into the distance. I knew that before long I’d be driving way past Those hills the next day.

My goal was to reach the IkaraFlinders Ranges, the site for fossils that make up the Ediacaran Fauna. These soft-bodied fossils, preserved in sandstone, represent the earliest metazoans (or animals) in the fossil record of the earth. These fossils were the reason I’d come to Australia. (Yep, not the beaches, not the Sydney Opera House, not the Great Barrier Reef.) I stayed the first night in Adelaide, recovering from my flight. But I was up the next morning to drive four hours and arrive at quorn (pop. 1068), where I stayed at the Flinders Ranges Motel. This was my base of operations for three days as I explored the source of the strange and enigmatic Ediacaran Fossils.

Driving north From Quorn the landscapes became flat and scrubby, and the towns were dusty and empty, their streets lined with Eucalyptus trees. The lanscape gained some variation when I finally reached the Ikara-Flinders Ranges.

compared to the nearby IkaraFlinders Ranges, these Ediacara hills were hardly noteworthy. the dirt road led to some

Ediacara Conservation Reserve

abandoned mines, and from there I scrambled around the scrubby hillside. armed with maps (and lots of water).

Ediacara Conservation Reserve

Blinman The landscape differed much from the road map I used driving north. The area colored blue and labelled “Lake Torrens” on the Road Map turned out to be a dry salt basin that I could barely glimpse as a white line in the distance. it turns out that once or twice per century the basin fills with water. The lake is about 150 miles long, giving an idea of the scale for this image.

The area that produced the famous fossils is known as the Ediacara Range. This area has

Ikara-Flinders Ranges National Park

been protected as a reserve by the state of South Australia.

It was so hot when I arrived at the

In 2010 a comprehensive plan

Ediacara Conservation Reserve that I

for managing the reserve

started to doubt the wisdom of coming

was released. The site is not

all this way. It hurt to even pick up the

attractive for its scenery; its

rocks baking in the sun! It’s not like

importance lies only in its claim

there weren’t other sites out there:

as a source for the fossils that represent the earliest known

Hawker

examples of animal life.

Namibia in Africa, Mistaken Point in Newfoundland, sites in northern Russia and the Canadian Cordillera, Charnwood Forest in England. But it was here that the uniqueness of this Fauna was first recognized. These scrubby hills gave their name to the assemblage of the first metazoans, and then eventually to an entire era in the history of life.

Quorn

(the scrubby desert town where I stayed for three nights.) prominent Ediacaran sites

2

discovering where to look for Ediacaran fossils by reading geological maps The Ediacaran fossils are not found on top of from these hills the

the hill, which is Cambrian (and thus later) in age.

valley declines at a

the famous ediacaran fossils were located to the

low angle into the

north and south of the main hill. The fossil bearing

salt basin of Lake

layers formed a syncline, or concave layer, that

torrens.

rose to the surface in the south and then again in the north. On the map mashup to the left the red lines represent the outcrop of the quartzite layer that holds the Ediacaran fossils.

Ediacara Conservation Reserve This overlay makes more sense when compared to a vertical cross section that explains the reason for the twin appearances of the fossil bearing Glaessner 1961

layer. The same layer peaks up on the south and then after declining under the hill it appears to the north (a double outcrop thanks to a small fault).

These maps of the area come from a scientific

The stratigraphy of

american article written by

the rock layers that

Martin F. Glaessner (1906-

make up this region

89). This was the first

of South Australia.

popular account of the fossils found here in the Ediacara Hills. the earliest articles on these fossils (such as the one in the scientific american) focus exclusively on this limited area that produced the fossils. subsequent research demonstrated how the ediacara hills are connected to the broader geology of the area, including the spectacular outcrops in the Ikara-Flinders Ranges. a stratigraphy is a vertical map of the layers of rock that together make up the rock record of a region. outcrops on the surface can be correlated to the stratigraphy. on the far left is a bar that represents the geological ages that correlate with the layers of rock.

The ediacaran fossils are found in a layer known as the Rawnsley quartzite, which is itself one of several layers contained in the “Pound Subgroup.�

This is the site of the original fossil finds (which go back to 1947 and the descriptions of R.C. Sprigg).

As can be seen from the shaded section on this map, The Rawnsley quartzite layer is expressed at many places in the surrounding landscape.

Since the requirements for preservation of the soft-bodied Ediacara are so particular, it is only on occasion that actual fossil remains are found within even the same layer (gehling 2000).

The images to the right and left show the extent to which our understanding of the geological context for the ediacaran fossils has increased in resolution.

Gehling 2000

Gehling 2000

3

The name Ediacara can be traced back to the mid-nineteenth century, when early maps of the region had a label for “Lake Ydeyaker.” Mining publications made mention of a mining field known as “ediacara.” The word itself is from an aboriginal word that has been interpreted as meaning “a place where water is,” (jenkins 2007), as well as (probably more accurately) “zebra finch comes out” (draft management plan 2007).

How do we get from a marine environment to these dry hills? in this recreation of the original landscape the names of contemporary cities are noted. the road I drove north from quorn to the Ediacara Hills would once have been beside a deep bay fed by inlets. The sediments received by the bay have now been thrust up and become mountains.

Geologists and paleontologists must be imaginers. they look at a landscape that has one set of characteristics today, and think backwards to a radically different landscape.

In this case we find ourselves in a marine environment near the equator 580 million years ago. Within the steep ravines that fed into the bay sand flows accumulated. some of those sandflows, perhaps during a storm, swept over the communities of ediacaran metazoans and buried them in such a way that they were preserved. it’s difficult today to imagine softbodied fossils preserved in coarse sandstone.

Gehling 2007

as millions of years passed the sediments built up in this bay.

These sediments make up the “pound subgroup” within which the Rawnsley quartzite and the ediacaran fossils are found.

as successive paleontologists have considered this question, the importance of microbial mats in holding the coarse sediment together, and thus maintaining the impression of the fossil, has been emphasized (Gehling 1999).

disproving the intertidal hypothesis for fossils:

this image from the scientific american article by Glaessner (1961) portrays the older view of the origin of the Ediacaran fossils.

Note that the organisms are all thriving in an intertidal zone.

“The previous interpretation of the Ediacara Member as a lagoonal and barrier system, with preservation of the Ediacara biota on tidal flats, and also in estuarine channels... is at odds with both the stratigraphic relationships and sedimentary interpretation given here...”

“The significant absence of fossils in the demonstrably shallow water sediments... argues against intertidal environments being responsible for any facies within the Ediacara Member.”

4

“Most fossils are impressions on the soles of storm sandstone beds, deposited on delta slopes between fairweather- and stormwavebase.”

(Gehling 2000)

Field Museum exhibit

Smithsonian exhibit

the diversity of presentations of the ediacaran biota is indicative of the continuing debates concerning the environmental context and lifestyles of these metazoans. in the smithsonian exhibit there are lots of floating things in the water (jellyfish and flatworm-like swimmers). the field museum exhibit settles everything firmly on an undulating mat of off-color microbes.

As it happens, the field museum exhibit on the left is best supported by current evidence. A. Seilacher has written about “Biomat-related lifestyles in the precambrian� (1999). Seilacher is best known for dispensing with the effort to connect the ediacaran organisms to later forms of life. He writes instead of a completely different ecosystem, now gone. This ecosystem was based on the widespread background of microbial mats. Seilacher (argues that in this world there were four main niches: 1) Mat encrusters (permanently attached to the biomat)

2) Mat Scratchers (grazed on top of the mat, rare)

3) Mat Stickers (suspension feeders that grew upwards)

4) undermat miners (tunnelers under the biomat)

Some evidence for this is supplied from the observation that while the frond-like organisms are found broken and scattered according to a powerful flow, other Ediacaran organisms do not orient themselves to that flow, but were apparently clamped down immovably on the microbial mat (Seilacher 1992).

Is this the closest we will get to discovering alien life?

Imagine with me. if you will, that time long before the dinosaurs where there existed a world so unfamiliar to us that it was like a scene from a strange story, perhaps even one of my own... And when we finally reach Europa, with its ice-covered seas, we are more likely to meet the animals in this book than we are to encounter anything resembling a dinosaur. ~Arthur C. Clarke The pristine microbial mat is the key to understanding the ediacaran fauna. In the illustration to the left you can see the transformation that took place as the ediacaran gave way to the flood of cambrian organisms. the sea floor in the cambrian was churned up by a variety organisms. in the ediacaran organisms do not dig down into the sedimentary layers beneath them. They either stick to the mat, anchor themselves in the mat, or burrow within and under the mat. After the advent of the cambrian era The microbial mat will exist only under extreme environmental conditions that inhibit other organisms that will tear up the mat. artist peter trusler, in fedonkin, et al, 2007

5

There was more to see than just fossils!

I’VE GOTTEN so caught up in the reporting on research that I forgot this is a travel narrative! I spent a day walking in and around the ediacara hills. I spent two more days hiking in the stunning Ikara-flinders ranges national park. St. Mary Peak gets to 3,842 ft, and that takes some of the edge off the extreme heat.

It’s hard to take a selfie when you’re by yourself! but a shadow selfie is still possible.

I knew the trip was a success as soon as I saw this small dickinsonia fossil, preserved in a layer of quartzite exposed at the ediacara Hills. i crouched on my knees to that I could get a closer look at the palm-sized fossil preserved on the floor of a marine valley. seeing an ediacaran fossil for myself was thrilling, but it made me glad rules were put in place by the state of south australia to limit visitors. though these Ediacaran fossils are witnesses to a totally different landscape along the edge of the super continent rodinia, they were a part of the story of life, and so the place where they are found is a sacred place that should be protected for later pilgrims. !

2 54

Dickinsonia fossil on sandstone surface the cambrian explosion 542 million

The Cambrian explosion gets the best

years ago represents a revolution

museum exhibits, like this one from

in body forms and lifestyles.

the Field Museum in Chicago.

Much of what we recognize today as basic divisions in the biosphere have roots in the cambrian era. one marked element of the cambrian is the presence of predators. signs of predators come down to us in the form of fossils with tools for predation, fossils that have damage from interaction with predators, and finally defensive innovations in body plans that only make sense given active threats (McMenamin 1986). It is striking that the Ediacaran fauna did not last (with some possible and temporary exceptions) into the Cambrian era. It appears that the ediacaran fauna was not suited for this new world of

Why this bewildering variety of

predators. Attempts to imagine

trilobites? One reason is the need for

a predator-less Ediacaran

protection against predators, which

world have put some in mind of

drove variation in body type. Trilobites

6

thus mark the arrival of the Cambrian era.

the imaginative experiments of Jorge Borges (Sagan 1998).

...back in Adelaide

Following my days in the Ikara-Flinders Ranges I drove south to what felt like luxurious civilization after all the small dusty towns I’d been hanging out in at the bottom of the world.

Adelaide had one site I was particularly keen on seeing: the South Australian Museum. The LARGE REGIONAL museum is known for ITS EXHIBITS ON NATURAL HISTORY AND FOR ITS DISPLAYS OF CULTURAL ARTIFACTS FROM AUSTRALIAN ABORIGINAL CULTURE. BUT the room that held the most interest for me was the expansive showcase OF Ediacaran fossils. the central display in the room is a framed assemblage of sandstone slabs brought here from along the walls exquisite Ediacaran

the Ediacara Hills. The slabs preserve an ancient surface with obvious ripple marks in the sand (again,

specimens are displayed.

as with the fossils, the microbial mats were key to preserving such ephemeral patterns).

Ediacaran fossils have a peculiar relationship with surfaces. Every ediacaran fossil is, after all, a snapshot of a marine surface. The ediacaran fauna has been characterized by A. seilacher as “always foliate” and showing “regular quilting patterns” (1999). given this attention to pattern, i wasn’t surprised that seilacher had helped create an art exhibit that displayed fossil surfaces, each showing a beautiful pattern created by organisms or natural processes. Seilacher is quoted in a review of the exhibit: “The whole exhibit tries to bridge the cultural divide between arts and A. Seilacher at exhibit on Fossil art that he organized.

sciences because this is an ingrained division that is not necessary...” (monastersky 1998).

7

how the Ediacaran fossils got mixed up with religious visions

The wolf shall live with the lamb, the leopard shall lie down with the kid, the calf and the lion and the fatling together, and a little child shall lead them.

The cow and the bear shall graze, their young shall lie down together; and the lion shall eat straw like the ox.

The nursing child shall play over the hole of the asp, and the weaned child shall put its hand on the adder’s den.

They will not hurt or destroy on all my holy mountain; for the earth will be full of the knowledge of the Lord as the waters cover the sea.

Isaiah 11.6-9

attention to human

The ediacaran fauna

portrayals of paradise,

developed under the same

whether planted in

evolutionary pressures

the past (Garden of

that led to all forms of

Eden) or cast into

life. But the ediacaran

the future (millennial

organisms went through

kingdoms) reveals

this development without

that a key element to

making use of overtly

these visions is an

predatory strategies

absence of predators

aimed against each other.

in this imagined space.

It’s difficult to discover

something about the

aversions to each other

violence of predation

among the ediacaran

seems to symbolize for

The author who

organisms. They went

humans their ordinary

most developed

about their autotrophic,

place in a world filled

the quasi-religious

filter-feeding lives with

with violence and the

interpretation of the

what looks to us to be

chaos of natural

Ediacaran fauna was

a sublime peacefulness.

catastrophes. imagining

M.A.S. Mcmenamin,

It’s hard not to wonder

away predation is the path

whose 1998 book

if this is an alternative

toward paradise.

playfully invokes the

evolutionary path.

Garden of Eden.

image credits: SAMuseum image by Flickr user StormeTX (CCL), Ancient Ripples by Flickr user Theen Moy

McMenamin, M.A.S., 1986. The garden of Ediacara. Palaios 1: 178-182.

McMenamin, M.A.S., 1998. The Garden of Ediacara: Discovering the First Complex Life. New York: Columbia University Press.

Monastersky, R., Living large on the Precambrian planet. Science News 149 (20): 308.

Monastersky, R., 1998. A Billion Years of Beauty. Science News, 154 (25/26): 398-400.

Sagan, D., 1998. Foreword to The Garden of EdiacaraL Discovering the First Complex Life, by M. McMenamin. New York: Columbia University Press.

Seilacher, A., 1992. Vendobionta and Psammocorallia: Lost constructions of Precambrian evolution: Journal of the Geological Society London, 149: 609-613.

Seilacher, A., 1999. Biomat-Related Lifestyles in the Precambrian. Palaios 14: 86-93.

Sprigg, R.G., 1947. Early Cambrian (?) jellyfishes from the Flinders Ranges, South Australia. Transactions of the Royal Society of South Australia 73 (1): 72-99.

Vickers-Rich, P., Body plans, strange and familiar, and the enigma of 542, in The Rise of Animals: Evolution and Diversification of the Kingdom Animalia, ed. Mikhail Fedonkin, et al. Baltimore: Johns Hopkins University Press.

Waggoner, B., 1998. Interpreting the earliest Metazoan fossils: what can we learn? American Zoologist 38: 975-982.

(CCL), Ediacaran at Smithsonian by Flickr user Ryan Somma (CCL), Ediacaran at Field Museum by Flickr user

Lenny Flank (CCL), Dickinsonia fossil by Flickr user Theen Moy (CCL), A. Seilacher at Fossil Art Exhibit from

website for International Geological Congress 2008 (http://iugs.org/33igc/coco/EntryPage-o12491-c10357-p5001.

html), Ediacara Hills landscape on pg. 4 from Ediacara Conservation Park Draft Management Plan 2010, land-

scape images from Google Street View, satelite images from Google earth, Cambrian period at Field Museum by

8

Clarke, A., 2007. Foreword to The Rise of Animals: Evolution and Diversification of the Kingdom Animalia, ed. Mikhail Fedonkin, et al.

Baltimore: Johns Hopkins University Press.

Ediacara Conservation Park: Draft Management Plan, 2010. State of South Australia.

Gehling, J.G., 1999. Microbial mats in terminal Proterozoic siliciclastics: Ediacaran death masks. Palaios 14: 40-57.

Geling, J.G., 2000. Surface stratigraphic context of the Ediacara Member, Rawnsley Quartzite, South Australia: A taphonomic window into the Neoproterozoic biosphere. Precambrian Research, 100:65-95.

Gehling, J.G. and P. Vickers-Rich, 2007. The Ediacara Hills in The Rise of Animals: Evolution and Diversification of the Kingdom Animalia, ed.

Mikhail Fedonkin, et al. Baltimore: Johns Hopkins University Press.

Glaessner, M.F., 1959. Precambrian Coelenterata from Australia, Africa, and England. Nature 183: 1472-1473.

Glaessner, M.F., 1961. Precambrian Animals. Scientific American 204: 72-78.

Glaessner, M.F., 1984. The Dawn of Animal Life: A Biohistorical Study. Cambridge: Cambridge University Press.

Jenkins, R.J.F., 1985. The enigmatic Ediacaran (late Precambrian) genus Rangea and related forms. Paleobiology 11 (3): 336-355.

Lewin, R., 1984. Alien beings here on earth. Science, New Series 223: 39.

author, painting of Eden by Lucas Cranach the Elder (1530).

Bibliography