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Creation 39(3):14–15, July 2017

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Dead crocodiles down under

How croc decomposition helps confirm a crucial element of Bible history


Arco images GmbH / Alamy Stock PhotoCrocs-down-under
An adult Australian Saltwater Crocodile or Estuarine Crocodile in water

A recent Australian research study on how crocodile carcasses decompose in water has important implications for fossilization.1

The researchers were seeking to better understand the processes operating on a skeleton after the flesh decomposes, affecting such things as how much of the skeleton remains, and how much stays articulated (the bones aligned together as in life).

If e.g. the top of the long leg bone or femur is found well away from its hip socket, that part of the skeleton has become disarticulated. A fossil skeleton in which the bones were scattered around would be completely disarticulated.

Crocodiles were chosen as they are commonly found as fossils worldwide, and are often found to have excellent skeletal articulation and completeness.

For the experiment, eight dead Australian saltwater crocodiles, Crocodylus porosus, were placed in tanks of fresh water. These are the largest living reptiles, and can be huge; for this study, juveniles were used.

Three different treatments were then used to assess how the rate and timing of burial affected the decomposition process.

  1. Two carcasses were immediately buried under 20 cm (8 inches) of fine-grained sand, simulating rapid burial.
  2. Three were allowed to ‘bloat and float’ uncovered until they sank to the bottom weeks later. At this time they were covered with 20 cm of fine-grained sand, simulating delayed burial.
  3. Three were not buried at any stage.

Some interesting findings

Sabena Jane Blackbird / Alamy Stock Photocrocs-skeleton

All crocodiles in Treatments 2 and 3 bloated and rose within 3–5 days, and remained afloat on average for 32 days. This shows how quickly the carcass would have to be buried after death to be significantly preserved.

At the end of the experiment, for crocodiles in Treatments 2, and 3 “…most of the axial skeleton, forelimbs, and hindlimbs were either partially articulated or disarticulated”.2

The 20 cm of fine-grained sand used to initially bury the crocodiles in Treatment 1 was insufficient to keep one of them buried, and on day 12 it made a ‘bloat and float’ escape from the sediment (it was reburied the next day).

The crocodiles which were immediately buried, unlike the others, stayed in the same position with virtually full articulation.3

On the basis of these findings, the authors concluded that “… preservation of articulated skeletons … is more likely to result from rapid burial”,4 and articulation is “… less likely to result from decay in a low-energy aqueous environment.”. Also, “… if a carcass is inhibited from floating, the likelihood of articulated preservation increases.”.2

Given that one of the sand-covered crocodiles in Treatment 1 made a ‘bloat and float’ escape after burial, the authors further concluded, “Therefore, burial would not only have to be rapid enough to occur before the bloated stage commenced (approximately before 4 days …), it would also have to involve enough sediment to continue to negate the positive buoyancy created by internal gas production” (emphases added).5

So to have whole fossil skeletons nicely preserved, they need to firstly be rapidly buried to provide immediate protection from scavengers. And the sediment covering them needs to be deep enough to protect against burrowing scavengers, and heavy enough to prevent the gas buildup from decomposition allowing the carcass to ‘escape’.

However, in today’s conditions, where would the sediment needed to cover a crocodile come from? Extensive deposition of more than 20 cm of sediment is exceptionally rare and/or limited in extent; and even that depth was apparently insufficient in this experiment. Far more sediment would be needed to bury much larger animals than juvenile crocs.

Reprinted from J. Palaeography, Palaeoclimatology, Palaeoecology 412 (2014) p. 115 with permission from Elsevier.carcasses
Photographs over time of one of the carcasses from treatment 3 that were allowed to ‘bloat and float’ They were not buried and decayed subaqueously (underwater) in non-moving waters.

The researchers offer alternatives to rapid sediment coverage. They argue that the carcass might get stuck in a log (!). It might bloat on dry land, and then afterwards somehow fall into the water. Quite cold or deep waters might reduce bloating—though how this prevents disarticulation from the scavengers who inhabit such regions is not clear. In any case, experiments have shown that even in oxygen-poor conditions and with protection from scavengers, unburied fish carcasses are quite disarticulated within a week.6 Such alternatives cannot explain the vast fossil deposits of crocodiles and other creatures around the world, such as the Karoo Basin in Southern Africa (about half a million square kilometres).

After more than seven decades of monitoring sediment movement globally, scientists have long recognized that insufficient sediment is available for widespread fossilization. Sediment is being deposited in rivers, lakes, estuaries, lagoons, and marine environments worldwide. Sediment deposition also occurs during small storms and rare catastrophic events. However, insufficient sediment is produced in any of these environments to bury large numbers of animals over large areas.

There was, however, one catastrophic event that would have provided enough sediment. “And the waters prevailed so mightily on the earth that all the high mountains under the whole heaven were covered” (Genesis 7:19). A Flood such as described in Genesis would have initially eroded the landscape, creating huge quantities of sediment, and then deposited hundreds of metres of sediment in many parts of the earth, burying all life within it.

For vast numbers of creatures, though not all by any means, burial would have been fast and coverage complete, the conditions identified by the researchers as necessary for well-articulated fossilization. So one would predict that in addition to some disarticulated fossil skeletons, well articulated skeletons would be very abundant—which is what we find.

More considerations

Depending on the circumstances and the nature of the sediment, fossil remains of rapidly-buried animals would be expected to not infrequently retain features that would have disinte-grated if sediment coverage had been slow and gradual. For example, the impressions from soft tissues (skin, muscle, feathers, hairs and the like). And that, too, is what we find. Also, since the fossils were only entombed a few thousand years ago, it makes sense of the recent discoveries of unfossilized soft tissues. Things like blood cells, hemoglobin, and other proteins are still present within some fossils—including dinosaurs that supposedly died out more than 65 million alleged years ago.

Given that all this is indeed what we find, it is not difficult to ascribe the fossil record to the global Flood described in detail in the Genesis account of the Bible.

References and notes

  1. Syme, C.E. and Salisbury, S.W., Patterns of aquatic decay and disarticulation in juvenile Indo-Pacific crocodiles (Crocodylus porosus), and implications for the taphonomic interpretation of fossil crocodyliform material, Palaeogeography, Palaeoclimatology, Palaeoecology 412:108–123, 2014. Return to text.
  2. Syme and Salisbury, ref. 1, p 120. Return to text.
  3. Syme and Salisbury, ref. 1, p 116. Return to text.
  4. Syme and Salisbury, ref. 1, p 119. Return to text.
  5. Syme and Salisbury, ref. 1, p 121. Return to text.
  6. Garner, P., Green river blues; creation.com/green-river-blues, especially ref. 8. Return to text.

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