THE PERMIAN-TRIASSIC EXTINCTION - THE GRAVITY THEORY


by John Stojanowski 3/20/07





barbour saleceline bags ugg雪靴專賣店 I. INTRODUCTION

The author of this document has written several documents entitled “The Rise and Fall of The Dinosaurs- The Gravity Theory” in which the role of a gradually changing gravitational field is posited as the cause for dinosaur gigantism and the primary force behind the eventual extinction of the dinosauria. This happened during the end of the Mesozoic Era (of about 250-65mya). According to that theory, the breaking up and dispersal of the component continents of the super-continent Pangea resulted in a gradually increasing gravitational field, thereby eliminating what the author calls Reduced Gravity Growth (RGG) life forms, resulting in the disruption of dinosaur/mammal equilibrium and allowing the eventual displacement of remaining dinosaurs by mammals.

The End-Permian, also known as Permian-Triassic (P-T) extinction occurred during a period of approximately 251 million years ago (mya). It is considered to be the most devastating period of global extinction in the last 400 million years. An estimated 95% of marine biota and 75% of terrestrial biota disappeared during this period.

Could a changing gravitational field have played a part in this extinction also? The author believes it could have, but not in the same way as the end-Mesozoic extinctions. This document will attempt to explain how gravitational changes could be involved in the Permian-Triassic extinctions. Whether or not there is an underlying gravitational cause for many other extinction periods is a subject that should be investigated. It is very possible that the common causes thought to be responsible for many extinctions were initiated by gravitational change.

II. P/T EXTINCTION THEORIES

There have been over a half-dozen theories written to explain the P-T extinction. The most well known are summarized below.

1. BOLIDE IMPACT

Due to the widespread belief that an asteroid/comet caused the extinction near the time of the transition between the Cretaceous and Tertiary (K-T) Periods about 65mya, which the author of the theory described in this and prior mentioned documents disagrees with, extinction theorists have made an effort to explain the P-T and other extinction periods based on an extraterrestrial impact.

The evidence to support this P-T extinction theory is almost non-existent. No impact crater of appropriate age and size has been found. There have been no eustatic (i.e. global) indications of a massive impact such as an irridium spike, shocked quartz, etc. This puts this theory near the bottom of the list of believable P-T extinction theories.

2. SEA-LEVEL CHANGE

If one views a graph of the eustatic sea-level fluctuations during the Phanerozoic eon (consisting of the last 542my spanning the Paleozoic, Mesozoic and Cenozoic Eras) such as the Exxon Vail Curve, numerous marine transgressions and regressions (rises and falls in sea levels) occur. Some of them occurred about the time ascribed to extinctions but many did not.

There are several reasons for marine transgression/regression. The formation and subsequent melting of ice caps and glaciers causes a regression/transgression sequence. No known glaciation occurred during the P-T transition.

Another cause is the formation of submarine, volcanic ranges, which would cause transgression. The subsequent subsidence of the submerged volcanic ranges would result in regression. Since the ocean floor over 200 million years old has been removed through plate tectonic subduction, the remnants of those marine volcanoes, if they formed during the P-T transition , would not be observable today.

Periods of intense sea-floor spreading causes a rise in sea-level because the less dense lithosphere rising from the spreading centers displace a greater volume of sea water onto the continental margins. Intense sea-floor spreading occurs when there is a lot of movement of the continental and oceanic plates. During the P-T transition, there was reduced plate movement because Pangea was nearing its final stages of consolidation.

The sea-level theorists have posited that a drop of sea-levels would have removed the available habitats of the epicontinental seas, thereby causing the extinction of many marine species. There doesn’t seem to be an explanation for the high terrestrial extinctions. Others have countered that the extinctions occurred during transgression (i.e. rising sea-levels) and there was a flow of anoxic (lacking oxygen) water into the epicontinental seas. Recently, it has been confirmed that transgression occurred during the P-T transition. Based on the reasons given for regression/transgression above, it would be reasonable to assume that submarine volcanism was the cause of rising sea-levels at the P-T boundary. There was also massive mantle-plume volcanism occurring during that period at the Siberian Traps.

It has also been pointed out that during the recent Ice Age, when sea-level fell and rose substantially and quickly due to the formation of polar ice, there were insignificant marine and terrestrial extinctions. It would seem logical to infer that if changing sea-levels were the primary cause of the P-T extinctions, the ratio of marine/terrestrial extinction would not be 95%/75% but a much higher one, such as 95%/10% and that deep water organisms would be less affected than those in the epicontinental seas.

It is more likely that the coincidence of major fluctuations in sea-level and extinction periods is an indirect one. There is a relationship between sea-level changes and the formation of submarine volcanic ranges, and, there seems to be a closer relationship between mantle-plume volcanism and extinction periods. Therefore, there seems to be an indirect relationship between sea-level change and extinctions, not one of cause-and-effect.

3. VOLCANISM

P-T Extinction theorists have pondered the coincidence of major extinction periods and eruptions of deep mantle-plume volcanoes. These eruptions are believed to originate at the Earth’s outer-core/mantle boundary. They produce what are called Continental Flood Basalts (CFBs) or Large Igneous Provinces (LIPs) when they breach the surface of the Earth. The Deccan Traps in India erupted near the time of the K-T transition and the Siberian Traps in Russia erupted near the time of the P-T transition. These two are the most widely known although there are others. Some of these from the last 251 myrs are shown in Table 1 below.

LOCATION AGE VOLUME (Million Cubic KM) PALEO-LATITUDE DURATION (Myr)
Siberian 248-250 >2 45N ~ 1
Newark 200-202 >1 30N ~ 0.6
Karoo 182-184 >2 45S 0.5-1
Antarctica 175-177 >0.5 50S ~ 1
Serra Geral 131-133 >1 40S ??
Rajmahal 115-117 ?? 50S ~ 2
Madagascar 87-89 ?? 45S ~ 6
Deccan 65-67 >2 20S ~ 1
North Atlantic 56-58 >1 65N ~ 1
Ethiopia 30-32 ~ 1 10N ~ 1
Columbia River 15-17 .25 45N ~ 1

Table 1 Statistics on Flood Basalt Provinces

Note: these are approximations and different sources will provide somewhat different statistics.

Some theorists have attempted to attribute a causal relationship between mantle-plume volcanism and major extinctions which occurred around the time of those eruptions. While it is conceivable that volcanic activity could cause extinctions if enough material could be injected into the atmosphere in a short period of time, deep mantle volcanism appears to occur over a long period of time, often several million years and is intermittent. The result is a layer cake buildup of lava flows.

The pyroclastic (i.e. explosive type) volcanism such as Mount St. Helens in Washington, Mount Pinatubo in the Philippines, Mount Pelee, Martinique and Vesuvius in Italy have had an immediate and detrimental effect on the environment due to the rapid release of toxic material. Mantle-plume volcanism, which probably has brief periods of pyroclastic activity, appears to be a more benign, slow acting phenomenon with a less devastating effect on the environment.

The Hawaiian Islands have been, over the last five and a half million years, formed by a hot-spot volcano of the mantle-plume variety. As the underlying Pacific Plate moves northwest, the mantle-plume, being in a fixed position, has formed the Hawaiian Island chain and prior to that the Emporer Seamounts to the northwest of the Hawaiian Islands.

The Siberian Traps volcanism was on a much larger scale than that of the Hawaiian Island volcanism but there has to be a measure of doubt as to whether the former eruptions could directly cause an extinction of the magnitude of the one over the P-T transition. The slow and intermittent particle outgassing of mantle-plume volcanoes would be removed from the atmosphere by rainfall. The carbon dioxide released could contribute to global warming depending on the rate of outgassing. The Traps took place in a relatively high paleolatitude and some scientists claim the extinctions began before the eruptions. If the Traps were the primary contributor to the extinction, one would expect to see the most devastating effects of the extinction in the high northern paleolatitudes compared to other areas but that doesn’t seem to be true. Therefore, the question that has to be asked is:

Was the Siberian Traps volcanism near the P-T transition a coincidence or was the volcanism a result of a more dominant force at work?

4. CLIMATE CHANGE

The climate of Pangea did change from a moist one with moderate temperature to an arid, hotter one during the P-T transition. Permian flora that thrived in cooler conditions such as glossopteris, became extinct or near-extinct during this period. A worldwide fungal spike has been found indicating a major destruction of flora in a geologically short period of time. However, it is not known whether the spike is a direct result of the climate change, acid rain, exposure to excessive ultraviolet radiation resulting from the ozone depletion of the stratosphere, deprivation of carbon dioxide by a release of methane or some other reason.

Whether the climate change, by itself, could cause the 95%/75% devastation is a subject of debate. A temperature rise of 6 degrees centigrade has been estimated and it seems like this would not be sufficient to explain the magnitude of the extinction in both marine and terrestrial environments. The reason for the global warming starting near the P-T boundary will probably lead to the primary cause of the destruction.

The global warming across the P-T transition is attributed to two possible causes. They are, the thermal effects of the Siberian Traps volcanism and the release of massive amount of methane from the bottom of the sea. Climate change seems to be one of the several killing mechanisms rather than the primary cause of the extinctions.

5. THE RELEASE OF METHANE FROM THE DEPTHS OF THE SEA/OCEAN

This is the most likely cause of the extinctions at the P-T transition. Methane, contained in methane hydrates at the bottom of the sea/ocean is held in a solid crystalline state by the combination of low temperature and high pressure of the overlying water.

By studying what scientists call the “carbon isotope change”, which was massive during the P-T transition, it has been widely accepted that the only explanation for the magnitude of this change is the disassociation of methane from these hydrates.

Carbon isotope analysis is a complex subject but it can be summarized as follows.

There are three naturally occurring isotopes of Carbon: Carbon-12, Carbon-13 and Carbon-14. Carbon-14 is a radioactive isotope which is used to date material up to 100,000 years old but it is not relevant here. Only the non-radioactive Carbon-12 and Carbon-13 are involved.

Scientists study the change in the ratio of C13 to C12 in various environments, both terrestrial and marine. They use a measurement referred to as “delta 13C” to keep track of changes in the ratio. Delta 13C is defined mathematically as:



Delta 13C is therefore the percentage change of the ratio of C13 to C12 in a sample material to that in a standard (times 1000).

The “Delta” in Delta 13C is often written as the Greek letter . In mathematical notation, that letter denotes a change in some quantity.

It turns out that during periods when biotic activity substantially declines, as in extinction periods, the value of delta 13C in the atmosphere and oceans shows a large negative increase. This is called a negative delta 13C spike. The following is a representation of the delta 13C from the late Permian through the early Triassic Periods in a marine location.



Figure 1 Delta 13C at a marine location during the late Permian-early Triassic

What is interesting about this graph of the delta 13C change is that there is a small peak in the mid-Permian which corresponds to the end-Guadalupian stage (about 260mya). This is a period in which there were high rates of extinction prior to the P-T transition extinction. After this peak is a gradual rise that increases more rapidly to a maximum at the P-T boundary (about 251mya). One therefore has to question the significance of the Siberian Traps volcanism as an initiator of the release of the methane hydrates. The Traps volcanism could have exacerbated the negative spike of delta 13C near the P-T boundary though. Also, note the secondary spike , somewhat smaller peak in the early Triassic. Other representations of delta 13C during this period show multiple peaks well into the Triassic period. There doesn’t seem to be a generally accepted explanation for the multiple peaks that extend for several million years into the early Triassic period. An explanation for these peaks will be offered in the next section.

Finally, the release of the methane from the submarine methyl hydrates appears to have had a dual effect relative to the P-T transition extinctions. The more direct effect would have been the anoxia (i.e. lack of oxygen) in the marine environment and terrestrial areas near marine locations. This would cause the asphyxiation of marine and near-marine biota. Methane is a more potent agent of global warming than carbon dioxide and is oxidized in the atmosphere in within 10-50 years to form carbon dioxide. Others suggest that hydrogen sulfide could have been produced, by the release of the methane and its chemical reaction with sulphur compounds, which would also have been toxic to life forms. The indirect effect, after anoxia and/or toxicity, due to the release of methane would be the more gradual but long term extinction caused by severe global warming. Since the rise in the negative delta 13C appears to have started well before the P-T boundary and gradually increased until the rapid rise at the P-T boundary, there has to be doubt as to whether the Siberian Traps was the trigger for the release of the methane. Although, as mentioned before, it could have exacerbated the disassociation of the methane near the boundary. With this in mind, the question that has to be asked is:

What was the trigger for the methane release?

III. THE GRAVITATIONAL TRIGGER

The author of the current theory, as described in this and prior documents describing the Gravitational Theory of Dinosaur Gigantism and Extinction, offers a new and significantly different explanation for the release of the methane from the submarine methane hydrates.

The thermal effects of the Siberian Traps volcanism has been cited as the trigger for the release of the methane. However, it was noted in the prior section that the negative delta 13C excursion began well before the end of the Permian and extended well into the Triassic Period. Some theorists have suggested that a drop in sea-level, by reducing the pressure of the overlying water, was the trigger. Recent study has confirmed that there was a marine transgression at the P-T boundary, thereby eliminating regression as a trigger.

The author of the current theory posits a negative gravitational change on and near the Pangean super-continent as the trigger for the release of methane before, during and after the P-T boundary. As theorized in a prior document entitled “THE RISE AND FALL OF THE DINOSAURS- PART III, The Gravity Theory of Gigantism and Extinction”, a shift in the Earth’s solid inner core, within the liquid outer core, is a function of the movement of the continental plates. The movement of the inner core is linked to these plates by a scientific principle known as the Conservation of Angular Momentum. As the continents coalesced to form Pangea, there was a corresponding shift of the inner core away from its Earth-centric position to a position further away from the center of mass of the Pangean super-continent, thereby lessening the gravitational force on Pangea. Because the Pangean land masses were distributed extensively over a primarily north-south expanse, there was a major latitudinal gravitational gradient and a lesser longitudinal gradient.

Pangea was in the end-stage of its consolidation during the P-T transition. Baltica and the South China Blocks were the only large land masses still being consolidated. The collision of the North and South China Blocks occurred during the Permian-Triassic transition. In other words, the gravitational force on the surface of Pangea was approaching its lowest levels. And, comparable to a dramatic drop in sea-level, the reduction in gravitational force would result in a gradual but significant drop in pressure at the bottom of the sea/ocean within and near Pangea.

Any movement of a continental plate would cause a corresponding movement of the inner core. The magnitude and direction of the core movement would be dependent on the mass of the moving plate and its direction of movement. The movement of the solid inner core would generate pressure changes within the molten outer core not unlike a piston moving within a cylinder of water. These pressure changes would be responsible for the mantle-plume volcanic activity. Some have observed the coincidence of plate tectonic activity and major mantle-plume volcanism but have not been able to explain the linkage. The current theory is an attempt to explain that linkage.

The major instances of large eruptions of deep mantle-plume volcanism have occurred during the period when Pangea was almost fully consolidated in the late Permian until its breakup was in full swing in the end-Cretaceous. Such major eruptions are not known prior to the Permian and those that have occurred since the K-T boundary have gradually decreased in size (i.e. volume of lava produced) as can be seen in Table 1. This would be expected because as the continents dispersed, the gravitational component from each continent would be diminished toward the original consolidated Pangean location, thereby lessening its influence on the inner core’s movement.

Some have also observed that the major flows of lava from the Flood Basalts that are associated with extinction periods seem to lag the start of the extinction periods thereby implying a non-causal relationship. This would be consistent with the current theory as it applies to the P-T transition. A continental plate movement would invoke a synchronous inner core movement (due to the linkage previously described), which would invoke a synchronous gravitational change on Pangea, which would invoke a synchronous release of methane (when the inner-core was moving away from Pangea). However, the inner-core movement would generate a mushroom plume starting at the outer-core/mantle boundary and rising to the surface over a much longer period of time. A lag in extinction/volcanism would be the result.

V. CONCLUSION

1. The P-T extinctions were most likely the direct result (of oxygen removal from marine and terrestrial locations along with possible hydrogen sulfide toxicity), and an indirect result (of global warming) due to the release of methane from submarine methane hydrates. The release of the vast stores of methane seems to be the only explanation of the large negative swings in the delta 13C values near, during and after the P-T boundary. Disassociation of methane from submarine hydrates can occur with large temperature increases and/or large drops in pressure. The trigger for the release of the methane doesn’t appear to be from the Siberian Traps because the methane release, based on delta 13C history, predates the P-T boundary. Thermal effects of the Traps volcanism may have enhanced the release of methane near the boundary.

2. The disassociation of the methane hydrates would probably have occurred in pulses corresponding to the delta 13C graph shown in Figure 1 and would have continued well into the Triassic Period. This would help to explain the unusually long recovery period.

3. The theory embodied in this document does not posit a new direct “killing mechanism” to explain the extinctions. What it posits is a gravitational trigger for the release of methane from submarine methane hydrates before, during and after the P-T boundary. The lowest values of gravitational forces on Pangea occurred when the final land masses were coalescing in the late Permian/early Triassic Periods thereby lowering the pressure on the submarine hydrates.

4. A gravitational linkage between continental plate movement/ shifting of the Earth’s inner core within the molten outer core/ fluctuations of surface gravity on Pangea, have been described and the author believes that this was the primary reason for the release of the methane. The pulses in the delta 13C before during and after the P-T boundary, the author believes , corresponds to movements in the continental plates which are gravitationally linked to the Earth’s inner core as described

5. The massive mantle-plume volcanism, including the Siberian Traps, is also a result of the gravitational linkage described above. As described in this document, the mantle-plume volcanism is posited to be a result of pressure changes within the molten outer core due to the inner core oscillations. The surface effects of the volcanism would lag its cause (i.e. large tectonic plate movement).

6. Also, the possibility that other extinction periods were initiated by gravitational changes based on the theory described in this and previously mentioned documents must be considered.



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