Questions tagged [sedimentology]

Sedimentology encompasses the study of modern sediments such as sand, mud, and clay, and the processes that result in their deposition.

Filter by
Sorted by
Tagged with
26
votes
2answers
8k views

Is there sand in Antarctica?

There's a song "Blizzard's Never Seen the Desert's Sand". Given Antarctica is a desert, someone questioned the title's validity. BUT is there sand in Antarctica? I'd imagine yes as it's a pretty ...
25
votes
1answer
40k views

What is responsible for the underwater waterfall illusion of Mauritius Island?

From an aerial view just off the island of Mauritius, there is what appears be an underwater waterfall. The picture below illustrates this visual phenomenon: The image can also be seen from the ...
18
votes
3answers
14k views

What is the difference between eluvium and alluvium?

I was reading about kimberlite on Wikipedia and it mentioned eluvium. I've heard of alluvium, alluvial fans, alluvial deposits, etc. However, when I looked up eluvium, it sounded exactly like alluvium....
14
votes
3answers
271 views

How have global sedimentation rates changed over the last billion years?

Do we have a graph of how sedimentation rates changed over time?
14
votes
2answers
2k views

Software for sediment transport modeling

I am doing a paper about coastal processes and I was told that I should include a sediment transport modeling to further examine my geophysical findings. I was reading in the net and found that ...
13
votes
2answers
1k views

Have meteorites been found in the oldest sedimentary rocks?

Dropstones sometimes occur in sedimentary rocks. These are foreign rocks and boulders that happened to "drop" into a sediment and were fossilised when the sediment was lithified. (source: ...
13
votes
1answer
529 views

Formation of limestone without living organisms?

Limestones are formed mostly from skeletal fragments of marine organisms. However, calcium carbonate dissolves naturally in water, so the living organisms are not the only source of it in water. Is ...
13
votes
1answer
153 views

Does the Great Pacific Garbage Patch increase sedimentation rates over the patch?

As in, does the debris in the patch area eventually sink? And if so, could sedimentation measurements over these regions provide a more fine-scaled measure of environmental conditions than ...
12
votes
1answer
773 views

What are the non-anthropogenic causes of The Netherlands' low elevation?

A large area of The Netherlands is below sea level. There are two non-anthropogenic reasons that I can think of: Compaction of delta sediments that lie below the country, A side effect of the ...
12
votes
1answer
538 views

Can concretions form in non-sedimentary rocks?

Most modern works (e.g. Nichols 2009; Allaby & Allaby 1999) seem to restrict the definition of ‘concretion’ specifically to formations in sedimentary rocks. I have recently come across a taxonomy ...
12
votes
1answer
141 views

Barite and Acantharians

Acantharians are planktonic protists (abundant in today oceans), sister-group to polycystine Radiolarians, that have the particularity of biomineralizing complex skeletons in strontium sulfate SrSO4 (...
11
votes
3answers
1k views

Identifying sedimentary rocks in hand specimen

I'm currently learning how to identify rocks in hand specimen. The initial classification into igneous, metamorphic, and sedimentary is mostly ok, but I'm having a problem with further identifying ...
11
votes
2answers
4k views

What is the oldest sediment?

Sedimentary rocks in Akilia or at Hudson Bay have been proposed as the oldest in the world. My question is not related to rocks, but rather to sediment while still forming sedimentary deposits but ...
11
votes
1answer
1k views

How does the sand appear on Hawaiian beaches

It's quite surprising to me that there's only one beach with black sand on Hawaii (maybe not exactly one beach, but it's only a very small fraction). The concern is, if the whole Hawaii is volcanic, ...
11
votes
1answer
2k views

Determining a rock age using volcanic ash layer

I wanted to know if volcanic ash deposits found in the geologic record are most useful in correlating the age of rock layers if the volcanic ash was distributed over a large area during a short period ...
11
votes
2answers
199 views

Waves on sandy beach separating differently-sized rocks?

I recently went to a beach, and I noticed that the sand seemed to have a few distinct regions. I'm wondering what would cause this, and how it works. One region is the part of the beach which is ...
10
votes
1answer
2k views

How much does sea level rise due to sediment deposition?

There has been a lot of noise in the news in the last few days because Congressman Mo Brooks from Alabama claimed that erosion played a role in rising sea levels. Quoting from Science magazine: ...
10
votes
1answer
167 views

Sediment layer chronology

In the new Cosmos series, Neil DeGrass Tyson in explaining different ways the age of the world has been determined, shows how sedimentary layers at the Grand Canyon are a fossil record of a lot of the ...
10
votes
1answer
3k views

Formation of flint & chert in limestones/chalk

Chert and flint are commonly found in chalky deposits (and have obvious importance in human history as tools). What are the processes of diagenesis of these silica-rich nodules in otherwise silica-...
10
votes
1answer
104 views

Biogenic origin of authigenic zeolites

Bohrmann et al. 1989 advanced the idea that the silicate phase from some clinoptilolites come from the diagenetic degradation of biogenic opal (from radiolarians in that case but presumably also other ...
9
votes
3answers
703 views

What do you call boulders of non sedimentary rock that were lithified into sandstone?

I'm convinced there is a word for this. I was in the Hoodoos at Writing on Stone this weekend and kept noticing what looked like reddish quartzite boulders laying around in the sand, or sometimes ...
9
votes
1answer
286 views

Large scale structures in the Sahara – what are they?

In Google Earth we can see some very clear lines in the Sahara. In the screenshot below you can clearly see these lines starting at the top going southward, then gently curving westward towards the ...
9
votes
1answer
823 views

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

What is the maximum thickness of limestone layers on earth? (Limestone or any other biochemical sedimentary rocks, for example chalk or coral reefs.)
9
votes
1answer
3k views

How do we use oxygen isotopes as temperature proxy?

As far as I know scientists use oxygen isotope 16 to 18 ratio in air trapped in glaciers (or in old foraminiftera shells) as proxy for temperature in the past. I know that $\ce{^18O}$ is heavier, and ...
8
votes
1answer
139 views

How to model bed load transport in channels of non-rectangular cross sections

All the formulas presented in the relevant technical literature refer to channels of rectangular cross section — the formulas assume a constant depth of flow right across the channel section. I need ...
7
votes
1answer
270 views

Incised valleys and hydrocarbon potential

The Wikipedia page on sequence stratigraphy states: Sandstone bodies associated with incised valleys are good hydrocarbon reservoirs. Can anyone elaborate on this statement and the reason behind ...
7
votes
2answers
147 views

What caused this waterfall to have rounded formations?

This is at Bua Tong Waterfalls in Chiang Mai, Thailand. Tried to find scientific information about this waterfall, but google turns up only travellers' vague guesses, suggesting calcium carbonate ...
7
votes
3answers
446 views

In an Earth-like planet with no history of carbon-based life forms, would there be limestone?

The extent of my understanding of limestone is about what Wikipedia says at the very top of the page: Limestone is a sedimentary rock, composed mainly of skeletal fragments of marine organisms such ...
7
votes
1answer
74 views

How are sand blocks formed?

My son asked me at the beach how are "sand stones" formed. These are the solid (but fragile) sand conglomerates which you can hold in your hand and which crumble to sand once pressed. I tried some ...
7
votes
2answers
449 views

How are chenier ridges and strand plains formed at wave dominated coastlines?

In the attached image, we can see chenier ridges and strand plains. How are they formed and what is the involvement of rip and longshore currents in their formation?
6
votes
4answers
1k views

Are all natural diamonds made of organic carbon material?

I've read that diamonds are created at a depth of about 180 km. By volcanic activity it comes above. But did plants and trees of 300 million years ago sink so deep? Or is it possible that inorganic ...
6
votes
2answers
2k views

What factors bring sand into or out of the beach?

I like to walk my dog along a beach, but in medium to high tide, there is no beach at all, as the water reaches the bluffs. The thing is, the height of the sand seems to vary drastically as well. ...
6
votes
1answer
1k views

Sand on the beaches of Kanyakumari, India

I recently visited the southern tip of India (State of Tamil Nadu) - it is called Kanyakumari. The beach was beautiful and one thing that struck me was that the sand was multicolored. The local legend ...
6
votes
4answers
7k views

Why is coal classified as a sedimentary rock?

Something just clicked in my head today. Rocks, by the definition I was taught, are composed of minerals which in turn are by definition not organic, so they are or were not alive. However. Coal, ...
6
votes
1answer
97 views

How does the meridional overturning circulation affect sedimentation rates in the North Atlantic?

There's a lot of downwelling in the region. Does this increase sedimentation rates?
6
votes
1answer
322 views

Hydrocarbon potential in Ganges Brahmaputra delta

According to Curray (1991): Total sediment thickness beneath the [Ganges–Brahmaputra delta] southeast of the hingezone exceeds 16 km... Considering a normal geothermal gradient and data for oil ...
6
votes
2answers
2k views

How far upstream would severe sea level rise (1m) noticably affect a large river?

The projection for sea level rise due to global warming seem to hover about 1m by 2100, let's use this figure. How far upstream would this noticably affect a large river, e.g. the Rhine? I think it ...
6
votes
2answers
7k views

Does dirt compact itself over time? If so, how does this happen?

If I were to bury something 10 feet (~3 metres) underground, with loose soil on top, would the ground naturally compact itself over time, until whatever I had buried has dirt tightly pressing against ...
6
votes
1answer
317 views

A simple formulation to calculate the sequence and rate of salt precipitation in a brine?

Is there a simple formulation to estimate the rate of salt precipitation in a brine given its ion concentrations and the evaporation rate? For example: if we know the concentrations of Cl−, Na+, Mg2+...
5
votes
1answer
147 views

What is the earliest sedimentation we know of?

Did large-scale sedimentation occur in any great amount during or soon after the Hadean/Archean period? Or did it only start later, because of the intense geological activity?
5
votes
2answers
194 views

How much climate history can be reconstructed using marine sediment cores?

Today I learnt in college that marine sediments can be used to reconstruct the climate up to 500 million years back. I find that number very strange because in another class we learnt that the ocean ...
5
votes
1answer
349 views

What, exactly, is angle of repose, and where is it in this image?

I'm a little mystified by "angle of repose" and the relationship to deposition and transport. In the following image, I detect 2 different angles of repose for the same material. How can this be? ...
5
votes
1answer
180 views

Geological feature - what is it?

Hello, We were walking in Bundoran in Donegal County, Ireland today and we encountered the geological feature shown in the picture (from above from cliffs and from very close up at beach level). We ...
4
votes
2answers
770 views

No sedimentation without water?

I just found a video on sedimentary rock formation, and to my surprise, it stated that this only could occur in water! I always thought that any layer of matter, if buried deep underneath more matter, ...
4
votes
3answers
2k views

Geology: facies v. formations

Can someone please explain the difference between sedimentary facies and formations?
4
votes
1answer
179 views

Do you have any informations about fossil-rich cherts from Scandinavia?

Me and some of my friends have found many rocks similar to these in central Europe - we believe that it is fossil-rich chert that originally comes from Scandinavia. There are many interesting fossils ...
4
votes
1answer
262 views

A sedimentary rock with only minerals

In my text book I came across this multiple-choice question A sedimentary rock consists of only minerals and lacks fossils, it could be classified as: i) a clastic sedimentary rock ii) a chemical ...
4
votes
2answers
941 views

How this sedimentary rock is made?

Apologies in advance for a beginners question. Different rock types make me curious and recently went to an area where interesting sedimentary rock is all over. As the area is on the coast, sea has ...
4
votes
1answer
330 views

What is the maximum grain size of a sediment that can be point counted using a standard thin section?

Point counting is an extremely useful tool for determining the composition of a clastic sedimentary rock. It is also very useful in provenance studies to determine the sediment source of a sedimentary ...
4
votes
1answer
274 views

How are the Scala dei Turchi staircases formed?

The Scala dei Turchi i (Italian: "Stair of the Turks") is a rocky cliff on the coast of Realmonte in Italy: https://en.wikipedia.org/wiki/Scala_dei_Turchi#/media/File:Scala_dei_Turchi_panorama.jpg ...