10
votes
How accurate is the law of superposition?
The principle does not apply to all materials on earth as observed by us but is primarily concerned with sediments and rocks that form from sediments. Since sedimentation is a process driven by ...
- 5,014
9
votes
How old is Steptoe Butte (WA, USA)?
Without directly knowing anything about WA geology myself, you're dealing with two ages here: the age the rock deposited as a sandstone (protolith age, 1.4-1.5 Ga), and the age of metamorphism (400 Ma)...
- 415
6
votes
Accepted
What are 'articulate shells'?
If I remember correctly from my intro to paleo class, the terms articulate and inarticulate refer to a classification of brachiopods depending on the nature of their hinge. Articulate brachiopods have ...
- 947
6
votes
How accurate is the law of superposition?
Here is another example where the law of superposition breaks. Mind you this is a natural process: meteorite impacts.
A meteorite impact will excavate material from the bottom, and deposit it above ...
- 23.1k
6
votes
Accepted
Predicting rock type from seismic processing
This is a ginormous question; a complete answer is probably worth an MSc in exploration geophysics. But I can try to give some pointers for places to find out more.
Preface: in general, considering ...
- 11k
5
votes
How have global sedimentation rates changed over the last billion years?
Big question.
There is not enough data resolution at the moment, neither spatially nor temporally. There are geological periods thought to have undergone higher erosion rates based on the abundance ...
- 1,723
5
votes
How accurate is the law of superposition?
As Peter correctly responds, for sedimentary rocks the principle of superposition is pretty much watertight except where tectonic superposition takes place. The latter can either repeat the ...
- 14.2k
5
votes
What are these geological horizontal lines formed on this mountain called and why they are formed?
Just to add on this point from the comments:
But this mount is the only mouth with this kind of formation in local mountain range
First, the image on the mountain's Wikipedia page clearly shows that ...
- 23.1k
4
votes
Accepted
Relative dating of intrusion
It does seem like it's impossible to know unless you have additional information. However, I think there is a hint in there. See this white halo around the intrusion? My guess (and I could be wrong ...
- 23.1k
4
votes
How was the onset of the Cambrian period dated?
Fossils are only in very rare cases dated directly, because they do not contain sufficient radioactive isotopes for dating.
Most geological periods are first and foremost defined by biostratigraphy- ...
- 851
4
votes
Accepted
How are stratigraphic limits defined before the Phanerozoic?
The standard stratigraphic nomenclature is a chronostratigraphic system based on palaeontological intervals of time defined by recognised fossil assemblages.
That's wikipedia for you. This is ...
- 23.1k
3
votes
Accepted
Stratigraphy of limestone applied to the Great Pyramid of Giza
Theoretically? Maybe! Practically? No. Identifying the general quarry site by comparing lithology is often possible. It might be possible to identify a block as coming from a particular level in a ...
- 2,010
3
votes
Accepted
What are the key elements defining the separation between Jurassic and Cretaceous?
Short answer, there isn't one.
The J-K boundary does not have a well defined fingerprint or marker, because of this it is in flux with different studies constantly offering to tweek or redefine its ...
- 6,878
3
votes
What did tunnel digging teach us about the formation of chains of mountains?
Tunnels have provided nothing more than what was learned from conventional geological drilling and surface mapping. Tunnels provide supplemental information. Very rarely do they provide "make or break"...
- 24.6k
3
votes
Accepted
Can we call the Precambrian eons (i.e. Archaic and Proterozoic) eras?
It is and is not an an error depending on how it is used. They are Eons but in older literature they were also, sort of, eras as the Eons were not subdivided as they are now. Especially in literature ...
- 6,878
3
votes
Accepted
Boundary problems in stratigraphy
I believe what is being referred to here is the problem of determining where, in a continuous deposition sequence, a particular geologic time transition occurs. If you have uniform depositional ...
- 822
3
votes
How is geological time divided into units?
The divisions in the geologic time scale have evolved over time.
Its origins can be traced back to Nicolaus Steno in 1669 described two basic geologic principles.
The first stated that sedimentary ...
- 5,959
3
votes
Methods and Software for Interpolating/Modelling of Stratigraphic Well Data in 2D/3D
I believe that Leapfrog 3D will do this. They have academic licenses. I also seem to recall that Intrepid Geomodeller does what you are after. Both of these options are probably overkill though.
- 1,044
3
votes
Methods and Software for Interpolating/Modelling of Stratigraphic Well Data in 2D/3D
OpendTect may do this, however getting to that stage would be a painful experience.
Petrel can do this very easily, however, that is not anywhere near free...
If you're a student, your department ...
- 146
3
votes
There is soil in Archean?
I don't totally understand what you are asking but yes there was soil in the Archean. In some locations around the world, these soils were buried and preserved as paleosols. The Archean paleosols are ...
- 4,429
3
votes
What makes pollen varieties useful index fossils?
Depends upon the species. If the pollen spores are large enough, and of wide spatial distribution, and easily recognizable, and preserves well in sediments, and of distinctive age range (geologically),...
- 14.2k
3
votes
Accepted
If dinosaurs lived in cities, would we be able to find traces?
"Lack of evidence is not evidence of lack."
That said, there is no evidence of any intelligent civilization prior to humanity. If dinosaurs, or for that matter, some other species, had ...
- 23.1k
2
votes
What makes pollen varieties useful index fossils?
In addition to what @GordonStanger said, there are a few other points to consider.
Pollens and spores are made out of sporopollenin which preserves way better than what one would expect.
Although ...
- 5,338
2
votes
What is the time period of these chalk/clay layers?
The layers correspond to thousands of years, i.e. 23,000 years in the Danien timeline:
The page sais that there is a variation of 23,000 for precession of the equinoxes and 100,000 for variation of ...
- 1,339
2
votes
Accepted
Will a new glacial age take place on Earth or Holocene will become a new climatic epoch?
The reason the Holocene began about 12000 years ago was because that was when Northern Hemisphere summers were hot but short. Those hot summers started a melting process.
Right now, July is when the ...
- 23.1k
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