Another great video from you that helped me understand what keeps sedimentary rocks together and why they are solid and not anymore "muddy" (soft). I often wondered what makes the banded layers (striata?) of limestone. In my area, the northern alpine "limestone" belt, so many exposed surfaces show these distinct layers with the layers being the hard rock and some softer, easier to weather, interface material to separate these banded structures, typically stemming from the jurassic and triassics. Why is that so? What kind of cycles can we see here? Is it annual/seasonal cycles of deposition? But then most of these layers are in the decimetre range wide - do we really get that much limestone sediment in one single year? Or is it climatic cycles? Then one layer might make up tens of thousands of years? And do we get these layers preferentially in deep water sedimentation or in shallow water. What do these striking macroscopic structures tell us? So many questions - but unfortunately no one has given me an answer so far... .

well. thats fulfils my old concepts too .Actually fives years ago from today , our class visited evaporite rock Known as Khewra Salt Mine, pakistan. thats called the "Museum of Geology”, where from Pre-Cambrian, Cambrian and Permian to Recent sedimentary rocks are exposed. Well, come to the point ,the Salt Range Formation consists of three members thats in ascending order is Sahwal Marl Member then Banderkas Gypsum Member and last one Billianwala Salt Member. Here the point you said in this video that EVAPORITES ROCKS ARE DEPOSITED DIRECTLY FROM SOLUTION AS A RESULT OF PRECIPITATION OF HIGHER MINERAL CONTENT .RIGHT? But here I can see that marl is deposited in initial stage ( in Pre-cambrian rocks of salt mine, Pakistan) as you said 1st gypsum deposited why is that so?

@GEOGIRL

2 жыл бұрын

Well I actually wasn't including carbonate rocks in my list/sequence, but if I did you are absolutely right! It would go in the order: calcium carbonates (like marl) > dolomite > gypsum > anhydrite > halite. Hope that makes sense :)

@ahsankachannel6430

2 жыл бұрын

@@GEOGIRL yes thanku so much u r brilliant

Sedimentary Rocks are always formed underwater? So the Grand Canyon was formed under water?

@GEOGIRL

2 жыл бұрын

If you are referring to the rocks that make up the sedimentary strata (layers) of the Grand Canyon, yes, they did! However, if you are referring to the the Grand Canyon as a structural feature, it formed by a river cutting the rocks that were already there. (AKA: the rocks that make up the beautiful layers in the Grand Canyon were deposited long before the canyon itself.) Hope that makes sense! :)

@MrGuzmanra

2 жыл бұрын

@@GEOGIRL so if u see sedimentary strata while hiking anywhere besides the grand canyon then that was formed underwater. Each layer tells u what was happening at the time. Like Torrey pine Beach

@MrGuzmanra

2 жыл бұрын

In San Diego

@MrGuzmanra

2 жыл бұрын

The top of the grand canyon is order than the dinosaurs 🦕.

@GEOGIRL

2 жыл бұрын

@@MrGuzmanra Well, not if you were walking over igneous or metamorphic rocks (these are not formed under water), we are referring only to sedimentary rocks here. But not ALL sedimentary rocks form underwater, just most. An example of one that does not is eolian (desert) sandstone. But the other environments where sedimentary rocks form, such as marine basins, shoreface environments, beaches, estuaries, deltas, lakes, rivers, and alluvial fans, all involve water (but in different amounts). Alluvial fans is probably the driest of those possible environments, but most likely involves at least small streams of water that lead to debris flows. Another type of sedimentary material that can become preserved is soil. Soil may become preserved in the rock record as what is called 'paleosols', but this process also must involve water (in this case, groundwater that flows through the soil and precipitates minerals in the pores of the soil to facilitate preservation). Btw, I have videos on my channel on how sedimentary rocks form in each one of those environments if you want to check those out ;) Hope that all makes sense :)