One of the other aspects of chemical weathering is that rocks form a crust over time, and the existence or absence of this crust can be used to determine if some stone artifacts have been worked or occur naturally.
Relative thicknesses of this crust can also be used to form relative dating of exposed rocks.
We can then ask ourselves: how else can such deposits form? To produce the extent and thickness of coal beds that we observe, we require a lot of plant matter to be deposited over a wide are in anoxic conditions, ...
[pendantmode] ... a wide area in anoxic conditions? [/pendantmode]
We can imagine peatification taking place in other environments besides swamps: for example, we can imagine a landslide transporting trees down a hillside into a so-called "dead" lake. The trees then might conceivably peatify and, if buried deeply enough under other sediments, coalify. But once again, we find that this would not account for the great depth and lateral extent of coal beds.
[creationistmode] or we can imagine great piles of organic debris deposited by the great flood of ~4kbc ... and compressed by the weight of the water during the flood ... [/creationistmode]
Coal deposits show evidence of a history. Most coals are found in sedimentary rocks deposited in flood plains. They often contain stream channels, roots, and soil horizons. Long time may not be necessary to form the coal itself, but it is necessary to account for the context where coal is found.
Rapid flood burial does not explain the great volume of coal world-wide that would have had to cover a pre-flood world, nor does it provide the heat necessary, nor does it provide a means to compress water out of the material (when the compression is accomplished by water), nor does it explain the gradations of coal deposits with depth (similar to the sorting of fossils problem).
Immediately underlying coal beds, we find paleosols, deposits which, as discussed in a previous argument, geologists identify as fossilized soils: most obviously, because they have fossilized roots in them. Indeed, the paleosols will sometimes have trees or tree-roots rooted in them, projecting up through the coal beds: furthermore, the trees are consistent with the fossil vegetation found in the coal. This fits well with the swamp theory of the origins of coal. The paleosols underlying coal beds (which are known as seat-earth, or underclay) also show the sort of soil characteristics we should expect to find in waterlogged soils.
[creationistmode] The existence of polystrate fossil trees is evidence of the great flood -- the tree should have decayed in one layer, not extend through many. [/creationistmode]
Sudden deposition is not a problem for uniformitarian geology. Single floods can deposit sediments up to several feet thick. Furthermore, trees buried in such sediments do not die and decay immediately; the trunks can remain there for years or even decades.
Swampy areas can be periodically buried by a number of events (see above on coal formation context), including flash floods upstream. Some trees species are more tolerant of their roots being buried than others, and can continue to grow in such situations.
The "polystrate" trees (that are known) consist of trunks and roots, not full trees.
NOTE: these comments should not be taken as a point to debate here - rather anyone interested in trying to rationalize creationist models should start a new thread.
So do the shell deposits of foraminifera and diatoms constitute reefs? (the cliffs of Dover?) or is this a different phenomenon (ooids?)?
You could also have a combination of sessile organisms in a reef environment (such as barnacles, muscles and brachiopods, yes?
Reefs: how do we know?
Another way would be that upper layers grow attached to lower layers, rather than in loose piles. Not just corals (where this is rather obvious), but in oysters (as you mention) and brachiopods grow attached to a substrate, and in a mature ecology this substrate consists of previous generations of these organisms. Some of the extinct brachiopods found on Mt Everest were fossilized attached to their substrates, including other brachiopods, iirc.
quote: ... In a typical brachiopod a stalk-like pedicle projects from an opening in one of the valves, known as the pedicle valve, attaching the animal to the seabed but clear of silt that would obstruct the opening. ... ... Brachiopods live only in the sea, and most species avoid locations with strong currents or waves. Articulate species have larvae that settle in quickly and form dense populations in well-defined areas, ...
These stalks are rather fragile, so fossil preservation of intact stalks indicates that the organisms were not disturbed after death, but buried gradually by natural silting processes and the growth of other generations of organisms.
When you get to that article, you can note that some species of corals have daily growth rings and that coral fossils (radio-metrically) dated to ~400,000 years ago show the earth rotated faster back then -- at ~400 days per year:
quote:The other approach, radically different, involves the astronomical record. Astronomers seem to be generally agreed that while the period of the Earth's revolution around the Sun has been constant, its period of rotation on its polar axis, at present 24 h, has not been constant throughout Earth's history, and that there has been a deceleration attributable to the dissipation of rotational energy by tidal forces on the surface and in the interior, a slow-down of about 2 sec per 100,000 years according to the most recent estimates. It thus appears that the length of the day has been increasing throughout geological time and that the number of days in the year has been decreasing. At, the beginning of the Cambrian the length of the day would have been 21 h ...
The best of the limited fossil material I have examined so far is from the MiddleDevonian ... Diurnal and annual growth-rates vary in the same individual, adding to the complexity, but in every instance there are more than 365 growth -lines per annum. usually about 400, ranging between extremes of 385 and 410. It is probably too much, considering the crudity of these data, to expect a narrower range of values for the number of days in a year in the Middle Devonian; many more measurements will be necessary to refine them.
A few more data may be mentioned: Lophophllidium from the Pennsylvanian (Conemaugh) of western Pennsylvania gave 390 lines per annum, and Caninia from the Pennsylvanian of Texas, 385. These results imply that the number of days a year has decreased with the passage of time since the Devonian, as postulated by astronomers.
I also found this graphic on this website although it was not used in the article:
This shows the smooth change in the length of days with time. The calculations based on just the astrophysics gives a 400 day/year figure for the Devonian and a 390 day/year figure for the Pennsylvanian, so there is very close accord between the predicted number of days, the measured number of days and the measured age of the fossil corals. These corals will be useful in anchoring the database of annual layers as it builds up a picture of climate change with age and extending, eventually, back into the Devonian period (360 to 408.5 million years ago).
Note that one of the causes for the slowing rotation rate is the tidal pull from the moon, and this decreases as the moon moves further and further from the earth (typical creationist mistake is to take today's rate and extrapolate it to the distant past).
There are as many hours in a year since the cambrian, but they are divide up into different length days -- ~21 hours and 424 days in the cambrian, ~22 hours and 400 days in the devonian, ~23 hours and 381 days in the triasic, and ~24 hours and 365 days today.
Astronomical planetary mechanics correlating with biological fossil records and radiometric dating information. Awesome.
start a new topic if you want to pursue this further
I see that you don't use the [qs]quotes are easy[/qs] or [quote]quotes are easy[/quote] formats, nor reply to specific posts (ie mine in this case), but use the general reply button instead. As has been pointed out in the past, these lower confusion and increase clarity: if you want to be obscure or hope to just be ignored then continue to do as you do.
Typical CREATIONIST mistake? Are you joking? Look up who tried to date the Earth's age from tidal friction: George Darwin, Charles' kid.
Logical fallacy: creationist still use the mistaken calculation, thus it still is a typical creationist mistake no matter who else committed the same calculation in the past and what the state of science was at that time.
quote:The 14C/12C and 13C/12C ratios of more than 250 terrestrial macrofossils (leaves, twigs, and insect wings) in the sediments were measured by accelerator mass spectrometry (AMS) at the Groningen AMS facility (13), after proper sample pretreatment (14). The floating varve chronology was connected to the old part of the absolute tree-ring chronology (2, 15) by 14C wiggle matching (16), resulting in an absolute calendar age covering the time span from 8830 to 37,930 cal yr B.P. (17). The age beyond 37,930 cal yr B.P. is obtained by assuming a constant sedimentation in the Glacial.
Marine carbon behaves quite differently from carbon in the terrestrial cycle. The residence time of carbon in the ocean can be measured in hundreds of thousands of years (where the residence time of carbon is defined as the average time an atom of carbon will stay in the ocean). ...
This is called the "reservoir effect" and it can be calibrated to obtain corrected results as well:
Radiocarbon samples which obtain their carbon from a different source (or reservoir) than atmospheric carbon may yield what is termed apparent ages. A shellfish alive today in a lake within a limestone catchment, for instance, will yield a radiocarbon date which is excessively old. The reason for this anomaly is that the limestone, which is weathered and dissolved into bicarbonate, has no radioactive carbon. Thus, it dilutes the activity of the lake meaning that the radioactivity is depleted in comparison to 14C activity elsewhere. The lake, in this case, has a different radiocarbon reservoir than that of the majority of the radiocarbon in the biosphere and therefore an accurate radiocarbon age requires that a correction be made to account for it.
One of the most commonly referenced reservoir effects concerns the ocean. The average difference between a radiocarbon date of a terrestrial sample such as a tree, and a shell from the marine environment is about 400 radiocarbon years (see Stuiver and Braziunas, 1993). This apparent age of oceanic water is caused both by the delay in exchange rates between atmospheric CO2 and ocean bicarbonate, and the dilution effect caused by the mixing of surface waters with upwelled deep waters which are very old (Mangerud 1972). A reservoir correction must therefore be made to any conventional shell dates to account for this difference. Reservoir corrections for the world oceans can be found at the Marine Reservoir Correction Database, a searchable database online at Queen's University, Belfast and the University of Washington. Human bone may be a problematic medium for dating in some instances due to human consumption of fish, whose C14 label will reflect the ocean reservoir. In such a case, it is very difficult to ascertain the precise reservoir difference and hence apply a correction to the measured radiocarbon age.
I have referred to this site before in answer to a creationist claim(1) about dating a modern seal at McMurdo Sound (Antarctica) with an apparent age in thousands of years. Looking up the area in question gave me a reservoir effect that brought the seal age back into modern times with proper calibration.
Although the radiocarbon dates agree closely with dendrochronology, they do not agree exactly.
The corrected dates are generally older than the uncorrected dates. A calibration curve from dendrochronology is (2):
14C is an unstable isotope of carbon, and so decays back to 14N via beta decay with a half-life of about 5730 years. Because the quantity of 14C being produced annually is more or less constant, whereas the quantity being destroyed is proportional to the quantity that exists, it can be shown that the quantity in the atmosphere at any given time will be more or less constant: the processes of production and decay of 14C produces an equilibrium.
I would say that it tends towards an equilibrium, but oscillates around a stable value due to the variation in production. These variations appear in the calibration curve as the jagged bumps in the dendro data.
... When we find approximately 400 days per year in the Devonian period and about 390 in the Carboniferous (see J. Wells, Coral Growth and Geochronometry, Nature, March 1963) then this is in line with the dates put on these periods by radiometric methods. ...
quote:A few more data may be mentioned: Lophophllidium from the Pennsylvanian (Conemaugh) of western Pennsylvania gave 390 lines per annum, and Caninia from the Pennsylvanian of Texas, 385. These results imply that the number of days a year has decreased with the passage of time since the Devonian, as postulated by astronomers.
I also found this graphic on this website although it was not used in the article:
This shows the smooth change in the length of days with time. The calculations based on just the astrophysics gives a 400 day/year figure for the Devonian and a 390 day/year figure for the Pennsylvanian, so there is very close accord between the predicted number of days, the measured number of days and the measured age of the fossil corals.
That curve would show a theoretical smoothed out running average days per year, without the spin up spin down effects of the magnetic core (and major earthquakes).
The photograph below shows the clam Arctica islandica, a popular species with sclerochronologists.
It is possible to use these growth patterns to date recent sediments in a manner analogous to dendrochronology. However, there is a more interesting way of using this data, which we shall discuss in the remainder of this article.
We also see similar layering in fossil brachiopods, such as are found on Mt Everest and other locations, showing the length of time that each organism lived. These would also show climate variations, and should be able to be aligned into a Sclerochronology (shell chronology) extending back millions of years ... if some grad student was looking for a research project ...