Climate or Tectonics; what determines mountain topography?

Hi all,

Many basins show some sort of continuous sediment supply over millions of years, with a orbital climate signal affecting sediment input. Baselevel will affect accomodation space in the basin itself... The source of this sediment is usually from nearby mountain belts. I understand isostacy will basically uplift mountains as more and more sediment is removed from them. This allows more sediment to be eroded and deposited over time than the volume of the mountain peaks above sea-level would suggest. Climate can cause more erosion and therefore higher isiostacic uplift rates and different topography. Now my question is, are there any records of climate doing this or is climate cyclicity only recorded in the transportation/depostion rate and not so much in mountain uplift? Or does tectonics generally overrule this signal?

hope this is clear!

thanks!

Thank you so much O_Stevens for that explanation and the resources!

This basically means that tectonics can actually cause climate to change in the mountain range and therefore can affect the type and volumes of sediment supplied to the basin. Am I right?

Just adding to this question, anybody have any idea on what data can be used to constrain the paleo-elevations of mountains?

Lyeo,

Good question and please allow me to give my opinion. I believe there are several techniques.

A) One could look at mineralogy of basement rock to assess burial history through Pressure-Temperature analysis. Different minerals forum under different P/T conditions and from this one could asses how deep certain mineral where buried prior to erosion removing the top layer, resulting in uplift due to isostacy.

B) A second option would be to look at sediment volumes and from that deduct the eroded volumes. This is tricky due to compaction and because it is usually very difficult to figure out which depocenter correspond to what areas of the hinterland. Through biostratigraphy one can, however, get a good idea of deposition speed and from that erosion speed.

C) Another option would be to look at the same biomarkers (primarilly pollen) and from that deduct vegetation of the hinterland. This can point towards the climate and elevation that was present at the time of deposition of the pollen. Often when pollen travel far they are oxidized making it more difficult to identify them. Furthermore, reworking can complicate things a lot.

I am probably missing a lot of other options, but this is what I could dream up at this moment. Additions and comments are very welcome!

A good example of this are the Himalaya and he Andes, as the results of this climate-tectonic system can bee seen, where the area’s experiencing more precipitation have been uplifted more than dryer regions. But what has triggered the uplift? Was it a tectonic influx causing higher mountain ranges, thereby altering the climate, causing more erosion and deeper valleys. Or was it a global climate shift, causing more erosion and thereby increasing isostatic uplift. Molnar & England, 1990, suggest a climate triggered system in which a system of positive feedback increases isostatic rebound?