24 votes
Accepted

Are there secondary causes of sea level change?

Yes, there are lots of other factors. Factors affecting sea levels are no different from other natural processes: there is a large number of coupled, non-linear effects, operating on every time ...
  • 10.8k
15 votes
Accepted

Why is the concept of "mass extinction" a relatively recent development in geology?

The idea of mass extinction is not that recent actually: Cuvier (1798), Buckland (1823) and d'Orbigny (1851) for instance were already talking about global catastrophes in earth history, linked to ...
  • 5,278
14 votes
Accepted

Width of strata in stratigraphic column

The width of a unit in a stratigraphic column, or 'log', sometimes represents the average grainsize of the rock. I can imagine it being keyed to some other property, but grainsize is common. You'll ...
  • 10.8k
10 votes
Accepted

Incised valleys and hydrocarbon potential

Sandstone bodies in incised valleys can be good hydrocarbon reservoirs. Incised valleys form on the coastal plain and/or continental shelf during a fall in relative sea-level by a combination of ...
  • 10.8k
9 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 ...
8 votes

Are there any geological periods found on top of each other that have dinosaurs of that period with in them?

There are definitely many examples of overlying Mesozoic strata that contain characteristic dinosaur fossils (and ichnofossils – i.e. trace fossils). One of the best examples is the Mesozoic ...
  • 263
8 votes
Accepted

Is the Principle of Fossil Succession accurate?

Your analogy with burying a box is not as accurate as you think. It needs specific sedimentary conditions for the remains of an organism to fossilize: being buried in soil is far from enough. ...
  • 5,278
8 votes
Accepted

Is the Principle of Original Horizontality a good indicator?

No, Steno's principle of original horizontality (I'll call it the POOH) is not 'safe'. It is not a useful theory. Don't confuse it with the law of superposition (also due to Steno), which is useful. ...
  • 10.8k
7 votes

Are there secondary causes of sea level change?

This link is a scientific talk by geoscientist Jerry Mitrovica (Harvard University) called 'Sea Level Fingerprints of Ice Sheet Collapse'. It's about an hour long, fairly technical, and focused on ice ...
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

Nuclear testing and the Anthropocene, a chemostratigraphic link?

I will try to plainly answer your question about an artificial radionuclide production/diffusion resulting from human activities, without getting into the discussion of deciding if this is ...
  • 2,633
6 votes
Accepted

Nuclear testing and the Anthropocene, a chemostratigraphic link?

Certain anthropogenic radionuclides have pragmatic advantages as markers for the start of the anthropocene. The advantage of radionuclides over anthropogenic stable nuclides is that the primordial ...
  • 4,339
6 votes

where are the thickest limestone layers on earth ? (CaCO3)

Reading your comments I see that you're asking: so could we find for example 1km high limestone layers on earth ? The answer is definitely yes. Here's an example of a stratrigraphic geological ...
  • 22.3k
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 ...
  • 10.8k
5 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 ...
  • 22.3k
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 ...
5 votes
Accepted

The youngest and oldest source rock for hydrocarbons in economic quantities

According "The youngest natural oil on earth" Doklady Chemistry vol. 438, pages 144-147: Prior to this paper, it was known that oil of the Guaymas basin is from young sediments and is 5000 years old. ...
  • 5,912
5 votes

Nuclear testing and the Anthropocene, a chemostratigraphic link?

The chapter on the Anthropocene (Zalasiewicz et al., 2012) of "The Geological Timescale 2012" quote 3 papers that used artificial radionucleotides as stratigraphic markers: Schwikowski (2004), ...
  • 5,278
5 votes

Width of strata in stratigraphic column

At least in Germany, another approach is very common („Verwitterungsprofil“): the width of layers shows their competence (resistance to weathering/erosion). So competent rocks (which don’t weather ...
5 votes

Database of geological group or formation exposures?

You may also find localised geological guides, such as the Roadside Geology series. http://geology.com/store/roadside-geology.shtml has a listing. While I have not used them, I have seen them crop up ...
  • 441
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 ...
  • 1,673
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 ...
  • 22.3k
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 ...
  • 20.7k
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- ...
  • 771
3 votes

Database of geological group or formation exposures?

Macrostrat is (or in fact will be) what you are looking for I think. This database is still in development and is apparently only available through the website as a beta so far. It only seems to cover ...
  • 5,278
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 ...
  • 4,339
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 ...
  • 6,556
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 ...

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