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Got Bones?

Could someone help me with my Geologic Timescale IQ?

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Got Bones?

Dear TTF Members,

I was wondering if you experts on the forum could provide a more in depth explanation of time periods such as the Mesozoic Era and what kinds of creatures dwelled at these times. I would like to learn more about the evolutionary timeline to help me become a better fossil enthusiast and helper in this forums' community.

Sincerely,  

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Fossildude19

Troy, 

This is my favorite generalized geologic time scale to consult: 

 

geologic-time-drawing.jpg

 

Wikipedia has a good entry about it, with a good scale below.

Hopefully others with more geologic understanding may expound on this .   :)

Hope that helps some. 

Regards,

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ashcraft

The geologic time scale is a function of human understanding through discovery.  Precambrian time is the largest by far.  As our understanding has increased, it has been further divided into units that I am unfamiliar with.  The eras start with the Cambrian Explosion, where modern life "suddenly" appears in the fossil record (personally I think it smells of a mass extinction event of organisms that didn't preserve well).  This is the start of the Paleozoic, or "primitive life".  There are two early mass extinctions, one caused by glaciation, the other I am not familiar with.  The Paleozoic ends with the third extinction, the Permian event.  This is the big one that almost wiped life out.  By this time, life was far from primitive and if I was in charge, I would group the midcarboniferous, the Permian and the Triassic into a fourth era.  The Mesozoic starts with the Permian extinction, and was known as the age of reptiles.  It had another mass extinction at the end of the Triassic, then the dinos really dominate the land ecosystems until the cretaceous extinction.  That starts the Cenozoic, also known as the age of mammals.  66 million years later, here we are.

 

Hard to squeeze 4.6 billion years into a post when using a stylus.

Brent Ashcraft

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Kane

There were more significant extinction events than this. For example, the Devonian period alone had more than two major ones, about six minor ones.

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Troodon

Here is a quick links to a breakdown of the different ages.  Lots happening in each one of these time frames and suggest searching the ones you're interested in

 

http://www.geosociety.org/GSA/Education_Careers/Geologic_Time_Scale/GSA/timescale/home.aspx

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Ludwigia

Wrangellian went to a lot of trouble to create this timescale document for us and I'm sure you'll find it helpful.  

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ashcraft
10 hours ago, Kane said:

There were more significant extinction events than this. For example, the Devonian period alone had more than two major ones, about six minor ones.

 

I don't want to imply that there are only 5 extinction events.  I don't keep up with the literature, but there as i understand it, there are 5 accepted mass extinction events.  I consider the Ordovician mass extinction event to be iffy as a mass extinction event.  As I understand it, a very narrow ecosystem was destroyed.  These organisms show well in the fossil record, so their loss is easily seen.  There was no extinction event on land (nothing to go extinct).

 

The megafaunal extinction event was the last one, fairly minor as far as extinction events go.  With the discovery of a platinum layer 12,000ish years ago, the possibility for an impactor trigger becomes more likely.  For many years human expansion was deemed the cause for these extinction, but with this new information, it could be that the event allowed the expansion of human population because of the removal of the rest of the apex predators.

 

i like keyboards for typing

Brent Ashcraft

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Kane

@ashcraft No, my apologies for misreading you! It was read and replied to in haste. 

 

There are some of these mass extinction events that have multiple factors as opposed to pointing to the one smoking gun. The megafaunal extinction may be one of those where it becomes a confluence of factors lining up just right, for sure. Other ones like the bigger of the two Devonian extinctions are still up for debate in terms of causes, but the spread of trees on land did contribute to a conjunction of global cooling and the release of certain compounds into the seas due to root systems. Temperature swings and increasing anoxia did a lot of the rest!

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ashcraft

I never liked the tree scenario.  It seems to me, that the tree growth would be self limiting.  If it caused rapid massive temperature change, it should have not allowed the trees to adapt, and they would have died back. If it was slow enough for the trees to adapt, then the sea animals also should have had time to adapt.  I also never understood the part about roots releasing material.  In the Ordovician, there was little or no plant growth, so erosion would have been rampant.  I would think there would be far more release of chemicals in that scenario then from tree roots, and it didn't seem to bother the organisms of the Ordovician.  Maybe the suspected chemical were organic?  I just don't see how trees could release that much material in relation to the volume of the ocean.

 

But let me add again, I am not well read on the subject at all.  Please educate me further.

 

Already knowing twice of what I did before about the Devonian extinction,

Brent Ashcraft

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Kane

I see your point. It would be a challenge to say with much certainty that pedogenesis would be to such an extent that it would cause such an impact on the marine environment. It is still possible, however, to have significant global cooling where the plants do survive (however that would most likely be in the still warm middle band while the new icy regions would wipe out a lot of the resident plant life).

 

Here are some papers,  mostly by the originators of the tree hypothesis:

 

Algeo, T.J., R.A. Berner, J.P. Maynard, and S.E. Scheckler. 1995. "Late Devonian oceanic anoxic events and biotic crises: 'Rooted' in the evolution of vascular land plants?" GSA Today 5: 45, 64-66.

 

Algeo, T.J. and S.E. Scheckler. 1998. "Terrestrial-marine teleconnections in the Devonian: links between the evolution of land plants, weathering processes, and marine anoxic events." Phil. Trans. R. Soc. Lond. B 353: 113-130.

 

Algeo, T.J., S.E. Scheckler and J. B. Maynard. 2000. "Effects of the Middle to Late Devonian spread of vascular land plants on weathering regimes, marine biota, and global climate." pp. 213-236. In: P.G. Gensel and D. Edwards (eds.). 2001 Plants Invade the Land: Evolutionary and Environmental Approaches. Columbia Univ. Press: New York.

 

Scheckler, S.E., 1986. "Floras of the Devonian-Missipian transition." pp. 81-96. In: T.W. Broadhead (ed.). Land Plants. Univ. Tenn. Dept. Geology. Studies in Geology 15. Knoxville.

 

Streel, M., M.V. Caputo. S. Lovboziak, and J.H.G. Melo. 2000. "Late Frasnian-Famennian climate: based on palynomorph analyses and the question of the Late Devonian glaciation." Earth-Science Reviews 52: 121-173.

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ashcraft

Thanks!  I will take a look.

 

Brent Ashcraft

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erose

One suggestion is to get a copy of a fairly recent college-level intro to earth history textbook. Earth Through Time or one of the others. Brand new ones will be pricey but a used copy a few years old will still be good.  These texts are always well illustrated and written to teach the basics of geology and earth history. They also almost always include great glossaries so despite being "college-level" they are not hard to read and understand. They will not go into detail about the flora and fauna of each period but they will emphasize where life was at each point along the way.

 

 

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Wrangellian
On 2017-04-12 at 5:47 AM, Ludwigia said:

Wrangellian went to a lot of trouble to create this timescale document for us and I'm sure you'll find it helpful.  

 Thanks, Roger.

 

Mine is good for showing everything in proportion (as was my intent) but I like the colorful ones with pictures, too, though they aren't usually in proportion and I have yet to see anything but a simple overview, nothing really comprehensive. You could start by learning the largest units (on the left on most charts) - the eras, then the periods, and for teaching/learning they are sometimes referred to as "Age of Invertebrates", "Age of Fishes", Age of Reptiles" etc. so you get a general outline. Then as you go along you will pick up more details.

 

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Ossicle

I use this to remember the order of periods within eras:D

Camels ordinarily sit down carefully, perhaps their joints creak.

Cambrian Ordovician Silurian Devonian Carboniferous Permian Triassic Jurassic Cretaceous

I could always remember the Mesozoic, but after Cambrian would get muddled in the Paleozoic. Now i think of camels.

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Kane
1 hour ago, Ossicle said:

I use this to remember the order of periods within eras:D

Camels ordinarily sit down carefully, perhaps their joints creak.

Cambrian Ordovician Silurian Devonian Carboniferous Permian Triassic Jurassic Cretaceous

I could always remember the Mesozoic, but after Cambrian would get muddled in the Paleozoic. Now i think of camels.

Love it! It's interesting how sometimes mnemonics like this create these types of disparate associations - just like in music (every good boy deserves fudge - EGBDF) and the planets (my very educated master just served us nine proverbs - mercury, venus, earth, mars, jupiter, saturn, uranus, neptune, and pluto - when pluto was a planet) :D 

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Wrangellian

I never got any use out of mnemonics - it seemed just as easy to remember the sound of "Cambrian Ordovician Silurian.." and "Mercury Venus Earth Mars..." than to remember a nonsensical lyric! But whatever gets you there.

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-Andy-

I made this timescale chart years ago. Some of the info is outdated, but I hope it's still useful to you.

 

TimeScale.thumb.jpg.bd139442430ff77f57b3f95adefa0c24.jpg

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verydeadthings

If you really want to get into detail about the construction of the modern geologic time scale, the authoritative text is Gradstein et al.'s The Geologic Time Scale 2012 (https://www.amazon.com/Geologic-Time-Scale-2012-Set/dp/0444594256). Unfortunately it's a bit pricey. A lot of this information can be found for free in datapacks associated with a software program called TS-Creator (https://engineering.purdue.edu/Stratigraphy/tscreator/index/index.php), which also lets you build your own time scales.

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Wrangellian

Yes, if you really want to get into it, the TS-Creator has just about everything. That's the data I used to compile my timescales.

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Wrangellian
On 2017-04-21 at 10:15 AM, -Andy- said:

I made this timescale chart years ago. Some of the info is outdated, but I hope it's still useful to you.

 

TimeScale.thumb.jpg.bd139442430ff77f57b3f95adefa0c24.jpg

Just because I'm a little obsessive and had nothing better to do at the moment, I've been tinkering...

590523d22016b_TimeScale-Andys.thumb.jpg.27f45db1b8a04bef9f108271ac927701.jpg

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