Naked Science Forum
Non Life Sciences => Geology, Palaeontology & Archaeology => Topic started by: geo driver on 19/01/2010 16:35:14
-
it looks wonderful cant make head nor tail of it though
-
Geologic maps show the rocks exposed at the surface. Most maps use a standard set of colors, usually based on the geologic time period, and a standard set of symbols for things like faults, folds, attitudes of the rocks etc.
Do you have a question about a specific map? It would make it easier to explain if you had a particular map in mind.
-
sorry i buggered the question up bass its a chronogeologic chart, and as soon is i can find the chart on my computer il post it.
-
Like this one?
http://www.stratigraphy.org/upload/ISChart2009.pdf
GAWD! YOU DON'T WANT TO KNOW!
Stratigraphers are the most reprehensible of the geologic community. They argue about bugs. No two think alike. They have humps on their backs and they look in microscopes most of the time so they are bug-eyed.
http://www.stratigraphy.org/forum/viewtopic.php?f=6&t=22
This is a sample of the discussion - this is tame
"Remarks on the Triassic/Jurassic transitional boundary interval
This is essentially an attempt to integrate the results from the six candidate GSSP proposals into an idea on what happened at the end of the Triassic as now understood and where in this history the T-J boundary is defined. The primary causes of the environmental changes across the T-J boundary are not discussed here because they are not yet sufficiently known.
For a long time the late Rhaetian was known as a period of decreasing diversity in important fossil groups, such as ammonoids, bivalves, brachiopods, conodonts, ostracodes, and foraminifers. The immediate transition into the Jurassic, however, was generally obscure, for various reasons. The end-Triassic sea level changes caused regionally widespread gaps in sedimentation and breaks of facies sequence. Moreover, unfavourable facies caused poor records of fossils with regard to frequency, diversity and preservation. Additionally, subsequent influences such as diagenetic processes and thermal metamorphism changed or even deleted biotic and non-biotic signals.
The time of decline in the late Rhaetian ended in a major crisis for the fossil groups referred to above, with a final interval characterized by a minimum of frequency and diversity. It is remarkable that not only the groups mentioned above as being in decline were affected but so also were radiolarians, whose diversity (against the general negative trend) still increased up to the beginning of the final crisis.
Most probably the beginning of the final crisis is indicated by the strikingly rapid extinction of about 70 Triassic species of radiolarians (which were still present in bed 9 of Kunga Island; 57 of them are missing already in bed 10, while 13 short-lived holdovers are absent in bed 13; Longridge et al. 2007 ISJS Newsletter 34(1): 21-33, fig. 4). Only three Triassic species persisted above the extinction level. From bed 10 upwards 20 new species appeared. Thus there was minimal overlap of the earlier and later groups.
There can be little doubt that this turnover reflects a major environmental change. To find out the reason, it seems important that the radiolarians are a pelagic group. Important also is that genera with highly specialised morphology were most concerned. Such forms obviously were adapted to a specialised mode of life that could not be continued after the environmental change. Since calcareous nannoplankton were also concerned it may be that the symbiotic algae were the particularly sensitive element in the radiolarians.
According to Williford et al. (2007 PPP 244: 290-296. fig. 1) the radiolarian turnover is situated within the initial negative Carbon Isotope Excursion (CIE) at Kennecott Point which has a range of about 4 m (110-114 m). Therefore it seems rather probable that the extinction of Triassic radiolarians and the CIE reflect the same environmental change and that this change was the reason for at least the beginning of the final crisis.
Whereas the reaction of the radiolarians to the environmental change was immediate and strong, other latest Triassic fossil groups survived a short time after the CIE. Holdovers into the critical interval are known from the radiolarians (Kunga Island), conodonts (UK), ammonoids (Ferguson Hill: Choristoceras crickmayi), foraminifers, ostracodes, palynomorphs (all Kuhjoch). This means that minimum diversity was reached a short time after the beginning of the crisis.
Of the later part of the critical interval little is known from most of the candidate GSSPs. Since the radiolarian change is completely situated within the CIE according to Williford et al. (2007) it seems that the recovery of the radiolarians began earlier than recoveries of other fossil groups. The reappearance of other fossil groups was clearly later than the CIE.
Most information on the upper part of the critical interval is provided at Kuhjoch and other sections in the same basin (Eiberg Basin). The excellent preservation in these sections (aragonite preserved) indicates that the sections offer the original fossil content without later alteration. The sections show that low diversity persisted almost up to the first appearance of Psiloceras spelae. Near this level also in other fossil groups new forms appeared: ostracodes, aragonitic forams, and palynomorphs.
The increase of diversity around the level of Psiloceras spelae indicates the end of the final crisis. The appearance of Psiloceras spelae at this level is not random. It is at the beginning of a general recovery. The T-J boundary is now proposed at this level. With this definition the final crisis is Triassic. The Jurassic begins with the appearance of new forms that persisted into later Jurassic.
ETC.
-
harsh but fair.
"A Dynamic Stratigraphy of the British Isles" whilst tremendously informative and arguably a seminal text describing the geological evolution of what is now the UK was my least favourite text at college...
-
And here I thought hard-rockers were blowhards [:o)]
JimBob is much better suited to answer this than I am- but the geochronographic (stratigraphic) chart is based on the presence and/or absence of certain fossils.
-
that was the one in was looking at bass. but thats the thing i do want to know but remove the S***, it would be nice to be able to discern between jurassic Triassic devonian....ect and know the relative rough time zone, with out making a fool out of my self or starting world war 3.
-
is there a simple one around anywere the rough guide to über old rocks, just so every time someone give me a period/epoch ect i could just go oh thats around bla bla bla years ago, or this type of thing was around then
-
The time periods were originally broken into 4 periods called Primary (crystalline rocks), Secondary (folded sedimentary rocks), Tertiary (undeformed sedimetary rock) and Quaternary (loose sediments). The Tertiary and Quaternary names have been retained, but are now combined into the Cenozoic. Since then, rocks were divided according to the first appearance of fossils into the PreCambrian and Phanerozoic. The Phanerozoic was subdivided into Paleozoic, Mesozoic and Cenozoic.
The oldest period of the Paleozoic, the Cambrian, corresponds to the first appearance of multicellular fossils. Before the Cambrian, which was initially thought to be lifeless, is the PreCambrian.
The Paleozoic is broken into different periods (youngest to oldest):
========================240 m.y
Permian
--------------290 m.y.
Pennsylvanian (also known as Coal Measures)
--------------330 m.y.
Mississippian
--------------360 m.y.
Devonian
--------------410
Silurian
--------------435
Ordovician
--------------500
Cambrian
======================570
There was a massive worldwide extinction at the end of the Permian (Paleozoic).
The Mesozoic (age of dinosaurs) is divided into 3 periods
=======================66 m.y.
Cretaceous
--------------------138
Jurassic
--------------------205
Triassic
========================240
Another massive extinction at the end of the Cretaceous (Mesozoic)
The Cenozoic is divided into 2 periods:
========================today
Quaternary
------------------2.6 m.y
Tertiary
========================66 m.y.
All these periods are further broken down into shorter subunits. For example, the Tertiary can be broken into Paleocene, Eocene, Oligocene, Miocene and Pliocene- which all are further subdivided. As you can see, this quickly becomes complex, even to practitioners.
Clear as mud?
-
Thanks, Bass. I am out of town and wasn't able to check in last night. Bass did a good job covering the subject. And I need to wake up.
-
There are some pretty easy mnemonic devices to remember the order as well.
For the Paleozoic:
Campbells Onion Soup Does Make People Puke (Cambrian, Ordovician, Silurian, Devonian, Mississippian, Pennsylvanian, Permian)
For the Mesozoic:
Try Jerked Chicken (Triassic, Jurassic, Cretaceous)
For the Cenozoic (at least for the epochs):
Perhaps Early Oiling May Prevent Premature Harm (Paleocene, Eocene, Oligocene, Miocene, Pliocene, Pleistocene, Holocene)
Unfortunately, most schools are getting away from the Cenozoic being divided between the Tertiary and Quaternary and are now moving toward the Paleogene (Paleocene to Oligocene) and Neogene (either Miocene to Holocene or Miocene and Pliocene with the Quaternary encompassing the Pleistocene and Holocene...depending on who you ask...ugh.)
-
On a not so related note...if you want to remember the electromagnetic spectrum in order of decreasing strength, try this:
Grandmas X-rated Underwear Vibrates In My Room
(Gamma rays, X-rays, Ultraviolet, Visible light, Infrared, Microwave, Radio)
The bawdy ones are the easiest to remember!
-
My heros, you see you can put as many colours on a chart as you like but, if its incomprehensible, to a numpty like me it light as well be in black and white. bass i now understand give me a couple of days then you can test me. lol.
-
a rough guide to the ages. like it basics first, then the subnuts