Stratigraphy understanding marine deposition Part 1 of 2

[@Dragrath1]

Hmm I hadn't thought about how the sea level variations effect where certain types of deposits are found in marine settings in hindsight its obvious but it hadn't crossed my mind! Anyways with regards to the introgression and regression and the siloclastic deposition shutting down precipitation I wonder if that had anything to do with how the banded iron formations formed back during the Precambrian? Obviously Earth was quite different back then but the same mechanical processes of erosion deposition and precipitation would have been in play even if they played out differently back then. As for the tectonic variations due to uplift and subsidence it probably warrants mention that erosion can also cause uplift in the case of crustal loading due to thick orogenic belts which create subsidence basins through the effects of their weight which means that as erosion removes that excess of rock it causes the land to gradually rebound. That is a pretty important piece of what is causing Everest and k2 to rise in the Himalayas as the peaks in that area are rising higher due to the deep erosional cutting of a nearby canyon/gorge system from the mountains. As for Basins they generally do fill in from sediment though the rate does vary based on the erosion and biological detritus feeding into a given depositional environment. It is one of the big reasons lakes ponds and inland seas which are no longer geologically active tend to disappear on relatively short timescales dependent on the size of the basin in question, unless actively restored to the landscape by processes like glaciers landslides volcanoes or structural subsidence basins in rift complexes etc. It is an important lesson which many reservoir lakes have to constantly deal with as without active dredging these dam reservoirs get shallower and shallower and either soon turn into wetlands or the weight builds up until the dams fail catastrophically. Thus it is natural that continental shelves should build up the same way. The only reason oceans don't experience the same thing is because the rate of deposition depends on the available mineral nutrients precipitates and sediment sources and as they age the crust gets denser due to settling and piling up sediment loading until it basically starts to subduct back into the mantle. I also was surpised to learn just how little time lithification of sediments can take given the right geological settings, for example the Cascadia subduction zone if entirely full of kilometers of sediment fed from the Cordilleran ice sheet and major outburst floods from the Columbia feeding an enormous thick turbidite debris fan which not only fills the trench but even crosses over the Juan de Fuca ridge onto the Pacific plate. Point is based on induced seismic measurement of the Cascadia subduction zone along its Washington and Oregon sections the sediment appears to have fully lithified into riding solid rock which means lithification has played out fairly fully during the Pleistocene feeding into the unique tectonic situation in the region. Lastly I have to glare at the whole paywall for knowledge I get you have to pay your bills but knowledge is inherently finite and scarce yet the fundamental resource for human innovation and progress/end rant.

[@stevenbaumann8692]

All great points. Thank you

[@stevenbaumann8692]

Yeah. Lithification can happen in a very short amount of time.

[@Presteroni]

Great video Steve!

[@DJDouglasWarden]

Very informative, thank you

[@RockManGary]

Most excellent Steve. You are really hitting your stride.

[@stevenbaumann8692]

Thanks! And thanks for being here

[@karenhunt7035]

An odd question: to join, I'm offered several choices: Basic, Middle, Advanced, and Other. For seeing the 2nd video, does it matter which one I join? I'm good with any of the levels, for what that's worth, I'm just not sure which is the most appropriate for me. I've not seen any of your lectures that are at too high of a level to follow (the classic example area where material is greatly higher than my level is anything that gets detailed in geochemistry, such as the "seds online" seminar)

[@stevenbaumann8692]

Basic is fine. I do put most things for all 3.