Hello Russett
***OFF TOPIC***
That was "erosion and deposition or sedimentation" not simply erosion and the rate is very minor when you analyze it, that's only 0.000006336 inches per year. The storm sewer beside my house deposits sand at a much much faster rate than that in GSL.
To get an idea of what erosion and sedimentation rates can be like, read the following two Abstracts. The first documents a sedimentation rate in Hudson Bay that makes the number I quoted extremely modest.
Author : Biksham, G.; and d'Anglejan, B
Date : 1989
Title : Rate of sedimentation and geochemistry of Southeastern Hudson Bay, Canada
Publication : Sediment and the Environment. Proceedings of a Symposium held in Baltimore; Maryland. International Association of Hydrological Sciences, Washington, DC. Publication
Issue : 184:
Page(s) : 27-36
Abstract
Suspended particulate matter (SPM) of Hudson Bay was estimated by collecting 60 samples at three stations and four different depths. The mean SPM in the study area was 0.642 mg/L. The sediments collected in traps indicated that the rate of accumulation increased with depth. Seasonal variation provided a rate that was 2 to 4 times higher during the month of May. The rate of sedimentation estimated by Pb-210 data was 51 to 63 mm/100 yr, which is in general agreement with the trap data. Carbon and nitrogen together constituted more than 50% of SPM. In the trap sediments, carbon ranged from 17 to 38% and nitrogen from 1.6 to 6.3%. In underlying sediments, the carbon was very uniform at a mean 1.96% of total, of which more than 85% was in the organic fraction. Elemental analysis on core sediments showed uniform bulk chemistry. High Si/Al ratio indicated that the source of sediments to the Bay may include other than fluvial transport. The amorphous silica content in the sediments ranged from 0.77 to 2.36%, which is 2 to 8% of total silica; in trap sediments amorphous silica content was more than 6%. Size studies indicated the breakdown of SPM, resulting in collection of relatively more fine sediments in the deeper traps. A gradual increase of sand fraction in the last 1000 years indicates a change in supply of the sediments to the Hudson Bay
Author : Begin, C., Michaud, Y., and Filion, L.
Date : 1995
Title : Dynamics of a Holocene cliff-top dune along the Mountain River, Northwest Territories, Canada.
Publication : Quaternary Research
Issue : 44(3):
Page(s) : 392-404
The dynamics of a cliff-top dune system located at the foot of the Mackenzie Mountains was reconstructed by radiocarbon dating and tree ring analysis of forest paleosols in eolian sediments, The first evidence of eolian activity dates to ca, 3000 yr B.P. when the breaching of a bedrock sill initiated the erosion of glaciofluvial deposits that resulted in the exposure of a 75-m-high cliff of erodible sediment, Sandy sediment eroded from the cliff by katabatic winds from the Mackenzie Mountains buried a mature forest growing on alluvial sediments, Despite a minor eolian event between 750 and 860 cal yr A.D., dune development began ca, 1100 cal yr A.D. and has been marked by two major sedimentation periods between ca, 1100 cal yr A.D. and 1460 A.D. and from 1865 to present. Detailed analysis of tree morbidity and mortality indicates that the dune progressed at an average rate of 78 cm/yr for the last century. Dune dynamics are directly related to slope activity that controls the episodic nature of sediment availability and to the katabatic wind regime. Comparison of the dune dynamics and paleoclimatic data suggest a possible influence of warm climate on eolian activity. (C) 1995 University of Washington.
There are numerous other papers available over the Internet including quite a number on ice age glacial erosion rates and post glacial catastrophic flood erosion rates.
To get another sense of what is geologically possible in 10my take a look at the continental drift animation GIF’s at the following link and the self controlled animation on the link below that. India was just colliding with Asia 60my years ago and Labrador, Greenland and Europe were still connected 50my ago.
ucmp.berkeley.edu
uky.edu
As I am sure you noted, only 160my ago, you could not recognize any of today’s continents due to their amalgamation/consolidation as part of one super-continent.
The following glimpse of the Cenozoic period 65 my ago which is roughly when most NWT kimberlites are believed to have emplaced indicates that dinosaurs of the type you probably had in mind were extinct. When you get to the Eocene epoch you will not the reference to 30 degree temperatures and high precipitation rates which would of course been conducive to rain forests growth, hence some of the coal seems along the Mackenzie River.
Cenozoic 65 Million Years to the Present
The Cenozoic is the most recent of the three major subdivisions of animal history. The other two are the Paleozoic and Mesozoic. The Cenozoic spans only about 65 million years, from the end of the Cretaceous and the extinction of non-avian dinosaurs to the present. The Cenozoic is sometimes called the Age of Mammals, because the largest land animals have been mammals during that time. This is a misnomer for several reasons. First, the history of mammals began long before the Cenozoic began. Second, the diversity of life during the Cenozoic is far wider than mammals. The Cenozoic could have been called the "Age of Flowering Plants" or the "Age of Insects" or the "Age of Teleost Fish" or the "Age of Birds" just as accurately.
The Cenozoic is divided into two main sub-divisions: the Tertiary and the Quaternary. Most of the Cenozoic is the Tertiary, from 65 million years ago to 1.8 million years ago. The Quaternary includes only the last 1.8 million years.
The Eocene Epoch 54 to 38 mya
The Eocene epoch is part of the Tertiary Period in the Cenozoic Era, and lasted from about 54 to 38 million years ago (mya). The oldest known fossils of most of the modern orders of mammals appear in a brief period during the Early Eocene and all were small, under 10 kg. Both groups of modern ungulates (Artiodactyla and Perissodactyla) became prevalent mammals at this time, due to a major radiation between Europe and North America.
Eocene Epoch: Tectonics and Paleoclimate
The Early Eocene (Ypresian) is thought to have had the highest mean annual temperatures of the entire Cenozoic, with temperatures about 30° C; relatively low temperature gradients from pole to pole; and high precipitation in a world that was essentially ice free. Land connections existed between Antarctica and Australia, between North America and Europe through Greenland, and probably between North America and Asia through the Bering Strait. It was an important time of plate boundary rearrangement, in which the patterns of spreading centers and transform faults were changed, causing significant effects on oceanic and atmospheric circulation and temperature.
In the middle Eocene, the separation of Antarctica and Australia created a deep water passage between those two continents, creating the circum-Antarctic Current. This changed oceanic circulation patterns and global heat transport, resulting in a global cooling event observed at the end of the Eocene.
By the Late Eocene, the new ocean circulation resulted in a significantly lower mean annual temperature, with greater variability and seasonality worldwide. The lower temperatures and increased seasonality drove increased body size of mammals, and caused a shift towards increasingly open savanna-like vegetation, with a corresponding reduction in forests.
The era matrix at the following link helps to bring these periods into focus.
ucmp.berkeley.edu
Kimberlites did erupt into forests in what is now the NWT and in the case of Alberta and Saskatchewan, into shallow seas. There are numerous papers on the subject.
You ask why are the fossilized trees on the Arctic Islands still there if ice age glaciers scoured everything at the rate of a mile every 10,000,000,000? I am no expert, but probably for similar reasons to why dinosaurs are exposed in Montana and Alberta, they were buried by miles of sediments, which have since been eroded probably by a combination of ice age glaciers and postglacial weathering.
The second Abstract above provides ample evidence of significant wind and water erosion over even a short time span and there are numerous other examples at the following link, including glacial erosion rates like the one below of 630,000 meters over 10,000,000 years. However, obviously these rates vary between erosion and deposition.
cgrg.geog.uvic.ca
Author : Anderson, L.W.
Date : 1978
Title : Cirque glacier erosion rates and characteristics of Neoglacial tills, Pangnirtung Fiord area, Baffin Island, NWT Canada
Publication : Arctic and Alpine Research
Issue : 10(4):
Page(s) : 749-760.
Ten cirque glaciers and their Neoglacial deposits were studied in th Pangnirtung Fiord area of Baffin Island to determine the origin of glacial debris and the erossion rates of subpolar glaciers. The rate of debris production for glaciers was 24 to 155 mSUP-3 yrSUP--1 . Clast rounding indicates that 84 to 96% of the till may be subglacially derived, and was produced at a rate of 22 to 140 mSUP-3 yrSUP--1 . Rockfall rates were low in the Baffin Island cirques, averaging 1 to 22 mSUP-3 yrSUP--1 . Grain-size analyses of Baffin Island Neoglacial tillss indicate that they contain little silt (5%) and clay (1%). Abrasion is probably negligible at the base of the Baffin glacierss. The low amounts of silt and clay suggest the glaciers are either wholly or partly frozen to their beds. Computed rates of total erosion by the glaciers of this study range from 8 to 76 mm/1000 yr, and are one to two times lower than those for Arapaho Glacier in Colorado. Glaciers occupying cirques with the highest rockfall rates also have the highest rates of glacial erosion. The limited data also indicate that large south-facing glaciers have the highest erosion rates. The low erosion rates suggest that 2 million to 14 million years were required to erode the cirques, and/or the erosion rates have not been constant.
Regarding mechanical concentration of diamonds in alluvial deposits, you might find it interesting to note that diamond is by no means a particularly heavy mineral in comparison to Magnetite, Platinum, Gold or even Pyrope for example.
Chrome Diopside - Specific Gravity is approximately 3.3 (slightly above average)
Diamond - Specific Gravity is 3.5 (above average)
Pyrop - Specific Gravity is approximately 3.6 (above average for translucent minerals)
Olivine - Specific Gravity is approximately 3.3 for magnesium rich olivine - 4.2 for iron rich olivine (above average to heavy for non-metallic minerals)
I did a considerable amount of searching for geochemical papers on pyropes and could not find any discussing the application of G11’s and G12’s to diamond prospecting or geology.
I will try again later in the week, but the answer to your question is that I live in Yellowknife, NWT like another recently frequent poster on the thread, and yes, my long distance rates are almost certainly more punitive than yours, unless you live in Europe.
I hope the above provided you with some of the evidence you suggested was needed.
Regards |
