The behaviour of the depositional surface over time is described by the sediment conservation equation, and is a function of the downwind sediment transport rate amd the concentration of sediment in transport over time, the latter measured largely by average dune height. The depositional surface rises over time, where the sediment budget is positive or influx exceeds outflux, and the balance is stored as the accumulation. A change from a positive sediment budget, where an accumulation forms, to one that is neutral (influx = outflux) or negative (influx < outflux) results in a bypass or erosional super-bounding surface, respectively. The super surface, therefore, bounds the accumulation, and accumulations and their capping super surfaces are the basic building blocks of eolian sequence stratigraphy.
- G. Kocurek
- K.G. Havholm
Dear Haithem,
In sequence stratigraphic terms the link between sea level and the groundwater table is the key controlling parameter on the preservation of aeolian deposits. When sea level rises the ground water table in the adjoining coastal plain will rise in parallel. Dune deposits below the groundwater table will be protected against erosion and may be preserved whereas dry dune sands can be removed by wind. The same can of course be achieved by subsidence [= relative change in groundwater table / sea level].
Another process in carbonate-rich dune sands is the formation of calcrete [aka caliche ] soils which form a protective crust preventing erosion. This may be linked to climate change [e.g. Milankovitch cyclicity].
If you are interested I can send you some photos to illustrate the above statements
Regards,
Evert van de Graaff
Super bounding surfaces (super surfaces) facilitate delineation of internal genetic architecture, or sequence stratigraphy, of aeolian sandstones and help in distinguishing controls on aeolian accumulation, hiatuses in accumulation and preservation of such sandstones. Check this page:
http://www.sepmstrata.org/page.aspx?pageid=15
Dear W.J.E. Van de Graaff and Joel Hirales Rochin , thank you deeply from my heart for your scientific response actually i am very interest with
sequence stratigraphy of eolian deposits.
The essence of sequence stratigraphy is placing facies in a geometric stratigraphic context under the assumption (which may not be entirely correct) that sediments above a surface are everywhere younger than sediments below the same surface. While some sedimentary cyclicity relates to sea-level change, sequence stratigraphy is not explicitly about sea-level change, no matter how widely that claim has been made in the literature.
Good day.
The detailed documentation of the thin layering is the important addition to the structural criterion that allows to distinguish layers of aeolian origin. The most important diagnostic property of aeolian deposits is the layering of migratory ripple. ( Sedimentary environments and facies, edited by X. Rading. (1990). Publishin House “Mir”, Moscow. (in Russian).
As rightly pointed out by Prof. Christie-Blick, sequence stratigraphy is not "only" about sea-level changes. At the same time, compliments to you for introducing an relatively unexplored segment of sediments into the realm of sequence stratigraphy.
I am (frankly) not aware of much work on sequence stratigraphy of aeolian (eolian) sediments , although we did some attempts (rather unsuccessfully I admit) on suspected Proterozoic eolian sequences.
The key problem is that all water-driven sediments can be eventually correlated with the 'relative' (if not absolute eustatic) sea-levels in a terrain. For wind, this is an open question.
My submission / suggestion (assuming you can indeed show that the sediments are entirely wind-driven and have no aqueous contribution to their accumulation):
1. Follow the hierarchy of bounding surface ordering as suggested by Brookfield (1977) for eolian sediments and further refined by Miall (1985) for fluvial sediments.
2. If possible demonstrate the temporal equivalences of same orders of the bounding surfaces across the deposit in 2 / 3 dimensions to derive a working model.
3. Assuming that all your super-surfaces are synchronous, test the model in terms of flux rates and see if that works.
Whatever results emerge should be interesting to know about.
Dear W.J.E. Van de Graaff thank you so much for answering me, can plz send me the photos any thing else that illustrate the your explanation statements
Dear Haitham,
please provide me with your email address so I can send you a set of photos &/or PowerPoint slides illustrating my previous comments.
Do bear in mind that currently I’m travelling for work projects and that I will probably have no time (or even access to my PC) before early November. So please be a bit patient
Regards,
Evert
Dear W.J.E. Van de Graaff thanks for your kind response my institution email address : "[email protected]" thank you so much for your kind cooperation.
Regards,
Haithem A. Minas
Dear W.J.E. Van de Graaff,
I am also very much interested in understanding your comments.can you send relevant material to me as well? My email I'd [email protected].
Thank you very much.
Regards,
Prasad BVRSN
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