Evolution? How?

real life wrote:

Hi Ros,

What you find, for instance, in sedimentary strata is the smaller, less mobile creatures usually buried first --- on the bottom; and the larger, more mobile creatures usually buried last - on the top. Not surprising, is it?

Hi Rl,

Actually what we find is that dead things don't move very fast and get buried just like all the other "less mobil" creatures.

Sedimentary strata usually form in geologic timeframes, not biological timeframes. So your suggestion that "slow things" and "fast things" appear in different strata seems crazy.

Every now and then you get a snapshot of time due to a sudden geological event, like a landslide or something like that (Gobi Desert Raptors and Proto's for example, or Dinosaur National Park Duckbill dinosaurs).

real life wrote:

When an area is inundated by water which results in the formation of sedimentary strata, it is not unusual that the smaller creatures would be affected first, would you agree?

So all those itty bitty T-Rex's and Duckbills and Brontosaurs were just having a "slow day"?

Come on, we're talking about geological timeframes here, not day/night floods. At least suggest something which relates to reality.

What you find, for instance, in sedimentary strata is the smaller, less mobile creatures usually buried first --- on the bottom; and the larger, more mobile creatures usually buried last ? on the top. Not surprising, is it?

rl

Quote:

What you find, for instance, in sedimentary strata is the smaller, less mobile creatures usually buried first --- on the bottom; and the larger, more mobile creatures usually buried last ? on the top. Not surprising, is it?

Show me a sedimentary unit where you say this has occured. Lets dissect it. Your trying to make an argument for hydraulic sorting and not geological zonation. Still trying to conjour up this flood?

Hi Ros,

Most fossilization in sedimentary strata likely occurs as a result of fairly rapid deposition and burial over periods of time closer to hours or days, not centuries or millennia, wouldn't you agree?

If an animal dies and is not buried fairly quickly, then scavengers or decay will likely leave little or nothing to fossilize. It's very unlikely that a carcass left even a year would provide much of a fossil if buried in sediment after having been exposed for that period of time.

Hi Ros,

What you find, for instance, in sedimentary strata is the smaller, less mobile creatures usually buried first --- on the bottom; and the larger, more mobile creatures usually buried last - on the top.

Ros wants to be funny and insist that dead things all move at the same speed.

While true, it misses my point that some critters ( the more mobile variety) could more easily escape while they were yet alive and thus avoid becoming fossils (at least temporarily). So the lower levels of sediment are more likely to be filled with those that are smaller and less mobile.

Things die, they fall to the ground, and sometimes the areas they happen to land on are prone to fossilization processes.

ros wrote-

Quote:

Things die, they fall to the ground, and sometimes the areas they happen to land on are prone to fossilization processes.

Wouldn't that suggest that the fossil record is only a record of life in places prone to fossilisation?

ros-

Well what proportion of the earth's surface is prone to fossilisation.Just roughly will do.

He's gone to enjoy nosebleeds and headaches somewhere beyond civilisation's limits.

real life wrote:

Ros wants to be funny and insist that dead things all move at the same speed.

Well, you were trying to be funny by suggesting that the speed an animal moves at in life determines how likely it is to get fossilized in death, so I was just getting even

real life wrote:

While true, it misses my point that some critters ( the more mobile variety) could more easily escape while they were yet alive and thus avoid becoming fossils (at least temporarily). So the lower levels of sediment are more likely to be filled with those that are smaller and less mobile.

And that is simply incorrect. In general, sediments don't jump up out of the ground and trap living things.

Things die, they fall to the ground, and sometimes the areas they happen to land on are prone to fossilization processes.

Do you agree that in nearly all cases that burial in sediment must occur fairly rapidly (measured in hours or days, instead of centuries or millenia) for the carcass to escape decay/scavengers and have a relatively good chance at fossilization?

real life wrote:

Do you agree that in nearly all cases that burial in sediment must occur fairly rapidly (measured in hours or days, instead of centuries or millenia) for the carcass to escape decay/scavengers and have a relatively good chance at fossilization?

I would probably add "months" to that list as well. Deserts and lake bottoms and such could be slow burial regions. In the deep ocean where decay processes (and everything else) is much slower, it might take more like years or decades to bury something.

Why? What's your point?

I could go along with weeks or months in some cases, sure. I just don't think that fossil bearing sedimentary layers that are postulated to have taken many thousands or millions of years to form actually took that long. In most cases, the fossilized creatures would have long been decayed to dust, or scavenged to pieces if it took that long to cover with sediment.

I don't know how long it took the Solenhofen limestone formation to trap its animals, but I suppose we could look it up...

The Solnhofen Limestone of Germany

Towards the end of the Jurassic, about 155 milion years ago, a warm shallow sea studded with islands covered much of what is now Germany. Sponges and corals grew on rises in this sea, forming reefs that divided up parts of this sea into isolated lagoons. These lagoons were cut off from the ocean and also from terrestrial runoff. Within these warm, isolated lagoons, the salinity rose, and the water may have been anoxic (depleted of oxygen) or even toxic at various intervals. Aside from cyanobacteria and small protists such as foraminifera, nothing could survive in the bottom waters of the lagoons for very long. However, any organism that fell into the lagoons from the land, or that drifted or was washed into the lagoons from the ocean, was buried in soft carbonate muds. Thus, many delicate creatures were not consumed by scavengers or torn apart by currents.