Roraima pollen paradox
|The divine comedy|
The Roraima pollen paradox is the supposed contradiction posed by pollen found in rock samples collected from Mount Roraima. Radiometric dating of said rocks places them in the Pre-Cambrian (ca. 4600 - 540 Mya, specifically 1500 - 1800 Mya), hundreds of millions of years before polleniferous (pollen-bearing) plants arose (ca. 245 Mya). Thus, the pollen should not be there, unless the rocks were contaminated.
In this context "contamination" is the idea that the pollen entered the formation after polleniferous plants evolved and therefore after the rocks were formed. This may have occurred through two non-mutually-exclusive methods: (a) the pollen rode on rainwater into the rocks through "cracks", and/or (b) the pollen entered a less-impermeable rock nearby that in turn intruded into the formation.
Creationists Emil Silvestru and Carl Wieland argue that contamination of the rocks was impossible and so radiometric dating is incorrect; this position is a one single proof fallacy, because even if contamination is absolutely impossible, it does not outweigh the massive evidence for radiometric dating. Interestingly, creationists think that a global, mountain-covering, terrain-restructuring flood depositing a very small amount of pollen in one specific location in a rock but not anywhere else is more likely than mere contamination.
Almost all information comes from a 1966 study and a 1964 discussion by R. M. Stainforth and associated scientists, though microfossils were previously noted in 1964. No more recent analyses in reputable journals have been published.
 Present scientists' views
Though the scientists present did not come to any consensus, they did have opinions about the pollen.
 On contamination
Some of the scientists said contamination after the formation of the rocks was feasible:
Their major points were:
- Pollen can't withstand the intensely hot baking process that converts shale to hornfels
- Cleavage breaks may have allowed pollen to travel through the stone via water
- There were no macroscopic plant remains, even though the pollen supposedly came from a river
Some of the scientists said contamination after the formation of the rocks was impossible:
Their major points were:
- Evidence on the degradation of anaerobically baked pollen is scanty
- Pollen couldn't enter, because:
- The stone that was sampled was hundreds of feet within the formation
- Water penetration is unlikely in the quartzitic sandstone and extremely unlikely in the hornfels
- If contamination occurred, many many years of pollen should be recorded
Since the study itself made no conclusion on the matter, and since no more recent publications have looked at the issue, the issue remains technically unsettled in science. This hasn't stopped creationists from seizing on the issue as disproof of evolution, and therefore proof of creationism.
 On the type of pollen
Fournier originally argued that the pollen was comparable to Cretaceous (ca. 145-65 Mya) pollen, but decided instead that Tertiary (ca. 65-2.5 Mya) pollen was likely. Fournier further argued that the pollen was dissimilar to current pollen (arguing against very recent contamination):
|G. Fournier, by utilizing the herbarium of J. Steyermark, was able to compare the recent pollen of the area with the assemblage in the rocks, and has stated that they are not the same. The first opinion of Fournier was that the pollen showed Cretaceous affinities, but closer study has led to preference for a Tertiary age.|
Nijssen argued that the pollen was Eocene (ca. 55-35 Mya) or younger:
|L. Nijssen regards the best assemblage, from a Paruima sample, as not older than Eocene and quite possibly post‑Eocene.|
Funkhauser argued that the pollen was Miocene (ca. 25-5 Mya) or younger, given its similarities to other pollen and unflattened nature:
Van der Hammen argued that the pollen was a mixture of Mesozoic (ca. 250-65 Mya) and Cenozoic (ca. 65-0 Mya) pollen. Van der Hammen further argued that the pollen had gotten into the rocks by way of cleavage planes, because when he ultrasonically cleaned the samples, most of the pollen disappeared:
Unfortunately, the scientists did not reach any consensus on the age of the pollen, on the type of the pollen, or the source of contamination (or lack thereof).
 Arguments for aqueous contamination
 Survival of heated pollen
Perhaps the strongest argument for later contamination is the inability of pollen to survive the heat of the shale-to-hornfel conversion process intact. If the pollen could not have survived, then it necessarily must have been contamination.
Several of the scientists present suggested that the pollen could not possibly survive intact the intense baking that converts shale to hornfels, usually ca. 600 C. Stainforth et al 1964 wrote:
|This suite indicates baking of the original shales to temperatures of 400-800°C.|
Further, the rocks were highly metamorphosed -- meaning that rocks had been reformed under intense pressure or heat. Stainforth et al 1966 wrote:
|It needs to be stated that petrological investigation of the rocks which yielded pollen and spores showed them to be highly metamorphosed, even though in hand specimens they somewhat resembled indurated[note 1] shales (Fig. 1). J. M. Bowen (Cia. Shell do Venezuela) described the samples from both Cerro Venamo and Paruima as true hornfelses in the cordierite-andalusite range, based on thin-section investigations (Fig. 2). Prof. H. H. Hess (Princeton University) confirmed this on the basis of X-ray diffraction investigations, and described the rock as a fairly typical hornfels, largely muscovite plus a little quartz, clay minerals apparently absent, and no chlorite noted. The samples from Paruima were rather more highly metamorphosed, as shown by the presence of biotite.|
Several studies support this fact, in spite of creationist quotemining attempts:
- Schiffbauer et al 2006, who conducted research on the preservation of acritarchs[note 2] under heat and found that pollen graphitized[note 3] to a significant degree at 500°C (± 2.5°C) at 1 atm after 250 days.
- Schiffbauer et al 2007, who found the same as in 2006, with improved techniques.
- Schiffbauer et al 2012, who found the same as in 2006 and 2007, with improved techniques.
All of Schiffbauer et al's studies came to similar conclusions: that graphitization likely occurred. From Schiffbauer et al 2007:
And from Schiffbauer et al 2012:
|While geological time cannot be replicated in the laboratory, the trends observed in the anoxic replicates indeed indicate that the level of carbonization increases with time: opacity and color showed trends toward more opaque and darker acritarchs, reflectivity became a more prominent feature with increasing time, and graphitelike C–C carbon bonding increased with a corresponding decrease of aldehyde and ketone C=O carbon bonding with increasing heating durations across all anoxic experimental treatment groups. In addition, while the Raman index of D:O intensity may not demonstrate an increase of crystalline ordering during the heating experiment, indicating a lack of true graphitization, RIP did confirm an increase in thermal maturity of the anoxic samples with increasing time—suggesting that time does play an important role in the overall level of carbonization. Each of these separate lines of evidence should be viewed as positive support for observing the process of carbonization throughout the duration of this taphonomic and thermochemical study.|
Only more recently (late 2000's on) have graphitized fossils been recognized as such, and thus could not have been the fossils in Stainforth et al's study. This is especially true given their appearance; Schiffbauer et al 2007 specifically describe the (proposed) fossils they found as "graphite disks", not as normal pollen.
Similarly, all of Schiffbauer et al's studies had a few limitations:
- The studies only investigated up to 500°C (± 2.5°C), while the Roraima pollen may have experienced temperatures of up to 800°C (that said, a temperature near 500°C is not unlikely).
- The studies did not study the effect of metamorphism (which was highly present in the Roraima samples) on fossil survival. From Schiffbauer et al 2007:
|As alluded to above, metamorphic shearing and heating are generally perceived as destructive processes in fossil preservation and thus highly metamorphosed rocks have not been a target of paleontological exploration. [....] The effects of pressure and directional shearing on fossil preservation have not been investigated in our experiments.|
- The studies only examined samples after 250 days, while real timescales are far longer.
- The studies only examined samples at 1 atm, which is equivalent to atmospheric pressure at the surface; pollen embedded in rock undergoing intense metamorphism undoubtedly underwent higher pressure.
 Schiffbauer et al 2006
Silvestru et al, "citing" Schiffbauer et al 2006:
|The only way to confirm the graphitization assumption is to test it directly. To this author’s knowledge, there is only one such experiment performed according to modern standards, which reproduced the assumed conditions of thermal metamorphism. It consisted in heating microfossil-containing sediments (non-metamorphic shales of the Proterozoic Ruyang Group in China, rich in acritarchs like Dictyosphaera delicata and Shiuyousphaeridium macroreticulatum) to over 500°C for durations compatible with real cases of thermal metamorphism. The samples were than [sic] treated the same way pollen-containing sediments are (palynological maceration). The separated ‘baked’ acritarchs were studied via Raman spectroscopy and scanning electron microscopy. The experiment concluded that no graphitization occurred and that the acritarchs have preserved their original morphology.|
However, Silvestru et al misrepresent Schiffbauer et al 2006. From the Schiffbauer et al's abstract itself:
There are several inconsistencies, noted by Schiffbauer himself:
- While Silvestru states "heating [...] over 500°C", Schiffbauer merely states "heated to 500°C (± 2.5°C)", which is based on fluctuation in the heating equipment.
- While Silvestru states that the rocks were heated for "durations compatible with real cases of thermal metamorphism", Schiffbauer merely states "varying lengths of time"; in actuality, the rocks were heated for only 250 days, which is not compatible with thermal metamorphism in geologic time, which could extend to thousands of years.
- While Silvestru states "no graphitization occurred and [...] the acritarchs have preserved their original morphology", Schiffbauer notes that, although the "morphologies of the heated acritarchs are retained, and no features related to graphitization have been observed", that "Preliminary Raman analysis reported here illustrates a decrease in D:G ratios of heated acritarchs as compared to spectra of unheated acritarchs, suggesting that the heated samples are becoming more graphitized." In other words, no physical distortion, yes discoloration, yes graphitization.
In fact, Schiffbauer et al 2006 supports the non-survival idea, since graphitization would distort the pollen's appearance.
 Bernard et al 2006
Alternately, creationists will cite Bernard et al 2006, who conducted similar research. Bernard et al noted:
|It is commonly believed that high-grade metamorphism erases all traces of fossils and, more generally, of biogenicity in rocks. To address this issue, we report in this study X-ray spectromicroscopy, Raman microspectroscopy, and electron microscopy observations at the nm-scale of fossil lycophytes megaspores found in Triassic metasedimentary rocks from the French Alps. These rocks have undergone high-pressure metamorphic conditions (∼14 kbar, ∼360 °C) during the Alpine orogeny corresponding to a burial of ∼35 km during subduction. Despite such metamorphism, the fossil megaspores are remarkably well-preserved texturally. An unusual mineralogical zonation consisting of magnetite, ankerite and calcite is superposed on the structures of the spore walls. In parallel, chemical heterogeneities of the organic matter (OM) composing the spore walls were detected. We discuss different interpretations for our observations, in particular a scenario in which these features are remnants of the original structural heterogeneities in the spores, and provide insights on the fossilization processes under high-grade metamorphic conditions. Whatever the processes leading to such heterogeneities, our observations oppose the usual assumption that high-grade metamorphism erases all indications of biogenicity in rocks and open new avenues for investigation at the nm-scale of the evolution of organic matter during diagenesis and metamorphism.|
It should be noted, however, that the pollen itself did not survive; instead, the pollen was destroyed but its texture survived (in a sense) on the surrounding rock. In the Roraima, the pollen itself actually survived, and thus is irrelevant to this study.
 Widespread nature of pollen
|[N]o one familiar with pollen should be surprised that pollen is found in surface exposed rocks. There is a veritible rain of pollen on everything. It is caught in rain water and transported down into the crevices in the rocks. So regardless of finding modern pollen in surficial rocks, it may not have been there from time immemorial. It may be a recent addition to the rock a modern contaminant. You don't even have to have a pine tree anywhere near you to have pine pollen falling on you. Wind and water disperse the pollen quite effectively. A palynologist friend of mine has written that he finds modern pine pollen in his cretaceous preparations all the time.|
Pollen is everywhere. Because of this, it's likely that, somewhere, some level of contamination should have occurred.
That said, Stainforth wrote:
|Grains and tissue fragments up to 150 microns in size are present, and are considered too big to have been carried by meteoric waters percolating through cracks.|
(For comparison, pollen sizes range from about 15 microns to about 100 microns across.)
However, Stainforth wrote this in the discussion prior to actually examining the rocks. Stainforth did not write (and nobody else has written) about the actual size of the cracks of the rocks, making it difficult to back up this claim.
 Appearance of the pollen
- What color is the pollen? Pollen darkens as it ages. If it is yellow or clear, it is recent.
- Have the rocks been cooked? Vulcanism around the rocks would burn up the pollen.
- Are the pollen grains flattened? Fossil pollens would be flattened as they are buried and compressed.
On 1: Nobody has written on the subject, making it difficult to verify. However, it should be noted that the 4 scientists that studied the pollen came up with widely varying dates, which may suggest some level of decay of the pollen -- though this is by no means necessarily true.
On 2: See above.
|J. W. Funkhouser (Bogotá) considers the pollen indigenous to the samples he processed but claims an age no older than Miocene, and probably younger; he notes similarities to the flora of the Mesa Formation (Pliocene - ?Pleistocene) of Colombia, presence of pollen of the Compositae, and an uncompressed preservation highly unusual except in young sediments.|
 Presence of limonite on bedding planes
|The shale‑like beds, being less competent, had eroded away below the massive Roraima sandstone, leaving an undercut[note 5] extending 10‑12 ft. inwards at the base of the cliff. The original samples were loose, weathered fragments from the talus slope below. New samples of unweathered rock were collected from the face of the undercut. On their return to Caracas, the three palynologists made independent investigations of the new samples. Utmost care was taken to avoid any possibility of superficial contamination. The rock cleaves along finely laminated bedding planes which are coated with limonite. Every effort was made to avoid these planes and some of the pieces processed were the central nubs left after chipping away the external parts of large blocks of the rock, which was dense enough to sound when struck with a hammer. Nevertheless, microfossils of the same type as before were recovered.|
Limonite's presence on the bedding planes of the samples is evidence of water flow. It is not unreasonable to suggest that the same water that deposited the limonite also deposited pollen, transferred by groundwater from the extremely frequent rains from the top of Mount Roraima.
Although the scientists attempted to avoid getting contaminated samples, it's likely that they simply failed, for several reasons. First, the extreme metamorphosis of the rocks may have created cracks that allowed pollen to travel further into the rock, away from the bedding panes. Second, from the graded bedding in figure 2, it's apparent that the bedding planes are present at a sub-millimeter scale and thus ultimately unavoidable.
 Ultrasonic cleaning
Stainforth described van der Hammen's findings:
Van der Hammen ultrasonically cleaned[note 6] the rock. Ultrasonic cleaning removes surface contaminants, such as dirt, but not material within solid, nonporous rock. Afterward, almost all of the pollen had been washed away, suggesting almost all of the pollen was concentrated on the surface, rather than inside the rocks, in turn suggesting for light, surface-deep contamination and against a significant amount of pollen being present deep in the rocks. Thus, the pollen is either a surface contaminant or the rock is more porous than suggested. In either case, the pollen is contamination, not bound within or between minerals and part of the original rock.
 Absence of macroscopic fossils
|The absence of macroscopic plant remains in the Roraima Formation is also noted, despite its assumed continental (?fluviatile) origin.|
If the anti-contamination argument is correct, then the rock must have gotten its pollen during its formative period. If so, then some presence of larger fossils -- such as leaves -- would be expected. No such larger fossils were found.
Sandstone and shale commonly preserve plant fossils, yet we find none. If we have conditions where pollen can easily be preserved we would expect to find the host plants preserved as well. Not even a fragment or root cast was found.
Some creationists, in response, have quotemined two sources, seeking to argue that finding pollen without macrofossils is not reason for contamination. First, the "Spores and Pollen" webpage from the Micropalaeontology Unit of University College London:
Here, the article is pointing out that it's often difficult to class spores, and the fact that they often move far away from and are separate from the parent plant makes this harder -- not that macrofossils are rare.
Second, the "MICROFOSSILS" webpage by Jere Lipps:
It should be pretty clear that foraminifera are distinct from pollen.
 Arguments against aqueous contamination
 Thick rock
The Roraima formation can be quite thick. Silvestru wrote:
|Based on more recent references, this sill seems to be the Cotingo Sill, which can reach 420 m in thickness.|
 Nonporous, low-permeability rock
Stainforth wrote that the rocks were impermeable:
|The Roraima sandstones are quartzitic, of low permeability, hence carriage of extraneous pollen through them by percolating water seems highly improbable. Even if this process could occur, entry of such pollen and spores into the nonporous hornfels lacks an explanation.|
This argument works both ways. Impermeable, nonporous rock should not only prevent contamination, it should prevent simple removal of any pollen that was originally present. It should keep pollen in as effectively as it keeps it out. However, when van der Hammen ultrasonically cleaned the rock, the pollen almost completely disappeared.
 Many years of pollen
Stainforth, who opposed contamination, stated:
|[I]f plausibility of this process [contamination by water] be granted, it would have been operative for a long period, and a mixed suite of spores and pollen should be expected.|
It should be noted that, according to various views of the scientists present, the pollen may have been as old as ca. 250 Mya or as young as 0 Mya, and none of the scientists had a date range for the age of the pollen smaller than 20 million years.
However, no description of the pollen assemblage(s) is available, so we can't evaluate this statement.
 Age of the pollen
Some creationists selectively quote the report as to the difference between the pollen now and that in the rocks:
|G. Fournier [...] was able to compare the recent pollen of the area with the assemblage in the rocks, and has stated that they are not the same.|
In fuller context:
|The palynological assemblage has not yet been matched conclusively against any known suite, a fact which is not surprising in view of the distance from control sections of known age and the highly endemic character of the flora of today, and probably the geological past, on the isolated Roraima Plateau. G. Fournier, by utilizing the herbarium of J. Steyermark, was able to compare the recent pollen of the area with the assemblage in the rocks, and has stated that they are not the same. The first opinion of Fournier was that the pollen showed Cretaceous affinities, but closer study has led to preference for a Tertiary age.|
It should be obvious that the contamination may have occurred at any time or times in the past 135 Mya, which does not require that the pollen all be recent.
It's also not surprising that no matches were found, given the diverse and unusual nature of the flora in the area. Mt. Roraima is home to a wide variety of plants, many of which are endemic to the flat mountaintops of the area.
In fact, the temporal dislinkage between current pollen and pollen in the Roraima is an argument against creationism -- why should pollen in one area of the world be so different from pollen elsewhere, when only (at max) 6000 years separate them? Creationists need to explain how the pollen could possibly have evolved so quickly that it would become unrecognizable.
 Arguments for intrusion
It's possible that contamination (in the sense of pollen moving through cracks into the rock) was not possible. However, intrusion was very likely. Stanforth writes:
|Mr. Fournier did not challenge the Precambrian radiometric dating of certain sills which cut the Roraima Formation, but suggested that the formation has accumulated gradually through the whole geologic time, and that careful correlations would show that the polleniferous beds belonged to a higher level. He cited an intrusion of established Triassic age which cuts the basement rocks. Dr. Gordon Young spoke next on the regional setting of the Roraima Formation. By means of regional cross sections from the North Venezuelan coastline to the Amazon Basin, he showed that beds of Roraima type could plausibly be fitted into the paleogeography of several periods. Even age-equivalence, in part, to the Freites Formation would not be a preposterous suggestion. Records indicate that, in a general sense, the Roraima is more indurated and heavily intruded in its lower parts, less so in its higher beds. On this basis a multiple age for the Roraima was suggested. [....] Dr. Dallmus supported Dr. Young’s concept of multiple age for the Roraima, and cited known sequences of beds elsewhere in the Brazilian and Colombian Guayana regions, ranging in age from Paleozoic to Tertiary, and cut by flat-lying sills.|
Here, a higher level represents a younger level, and one which would have formed while polleniferous plants dispersed their pollen.
It should also be noted that it's possible for both contamination and multiple ages to be true simultaneously. In fact, if the rock is dated to multiple ages, then it simply shows that the formation had more instances of intrusion, which would have allowed pollen more opportunities to permeate the rock.
 Radiometric issues
|As regards the radiometric dating, there is a disquieting overlap between stated ages of the Roraima Formation and the underlying basement rocks. The latter suffered complex deformation and vulcanism, and were then deeply peneplaned before being covered by thousands of feet of Roraima sandstones, and only after these prolonged events were the dolerites intruded, on which age‑determination of the Roraima has been based. If the radiometric technique is valid there should be a long and clear‑cut time‑gap between ages assigned to the basement rocks and to the Roraima beds. Such a gap does not exist in the experimental results published, but this discrepancy is glossed over in the latest summary of radiometric dating in British Guiana.|
However, radiometric dating was an emerging field in the 50's and 60's, and improved techniques and equipment allows more recent radiometric dating (2003) to clear up many of these issues.
 Scientific conclusions
Silvestru et all quote Stainforth et al in their conclusion:
|Stainforth’s conclusion to his Nature article has become a staple to many creationists: "As stated, we offer no solution to the paradox. It is clear, however, that the botanist Dunsterville in his hunt for rare orchids stumbled on a highly intriguing geological problem."|
It's hard to accept a scientific "dunno what happened here" as strong evidence for YEC. It should be noted that the original report was published in the Letters section of Nature, and thus isn't a full-fledged scientific report.
Further, the age of the study (nearly half a century old) makes any conclusion even more suspect. At the time the paper was being written, even plate tectonics was new -- literally, at the time this paper was published, most geologists were still figuring out how mountains formed. Figure 3 even mentions that elevation was determined by aneroid barometer. (To use an aneroid as an altimeter, sea-level air pressure must be known, and appropriate compensation applied. Even then, it cannot measure altitude with the accuracy (centimeters or millimeters) needed for gauging tectonic activity.)
 Censorship and intentional ignorance
Emil Silvestru of Creation.com wrote:
|In the 1940s and 1950s the discovery of fossils outside the accepted evolutionary position in biostratigraphy was usually honestly reported and discussed. In the following years, examples that could not be explained were simply ignored, never being mentioned again. Although this paper will only deal with the South American fossils and sediments, I would like to also mention that it does not represent the only such case: the discovery of vascular wood and six-legged, composite-eyed insects in the Precambrian salt deposits of the Salt Range in Pakistan. After many unsuccessful and well-documented efforts to explain the discoveries away, a veil of silence covered them so that the most recent available to the Salt Range does not mention any fossil finds. [....] It is fair to say that nothing much was heard of or done about this discovery until creationists started referencing it in the 1990s. One would have expected Nature to encourage and publish new research aiming to eliminate the paradox, but nothing seems to have happened. [....] It is most unfortunate that one cannot accurately locate the microfossil-bearing layers in the recent stratigraphic synthesis (which elevates the RF to ‘Roraima Supergroup’) because there are no references at all to any microfossils. As in the case of Pakistan’s Salt Range fossils, silence is used to avoid uncomfortable facts.|
Silvestru dabbles in conspiracy and persecution. It's entirely possible that nobody's researched the issue because nobody knew about, cared about, or had resources to act on the pollen. Silvestru instead implies that evolutionists have somehow organizedly silenced their opposition (or at least prevented "opposing" publication), without any evidence to support this assertion.
In fact, the lack of scientific publishing on the issue may suggest that the "pollen paradox" is too scientifically weak to support claims that radiometric dating or the evolutionary timetable are incorrect, at least in actual peer-reviewed journals.
Yet neither Stainforth nor his colleagues nor any other scientist has ever deemed the matter worth enough attention to even publish a single follow-up. No description of the pollen, not even an indication of how many types. This is not the thunder of a paradigm-shifting discovery, it is the quiet sigh of the mundane.
 Creationist model
Arthur Chadwick, creationist, talking about supposed Precambrian pollen in the Grand Canyon:
|More difficulties are created than are solved by Burdick's report since it would require the explanation of the accumulation of all the Upper Precambrian sediments (10,000 ft.), their lithification and subsequent erosion before the first additional fossil forms were buried. Add to this the picture the many thousands of macerations of lower Paleozoic and Precambrian rocks which have been carried out in scores of laboratories around the world which have not supported Burdick's claims. There is a general absence of evidence for flowering plants below the middle Cretaceous. It is a responsibility and challenge to the creationists to develop a model of earth history which explains the absence. [....] In our hands, application of the cardinal principle of the scientific method - reproducibility - has failed to authenticate his record. thus the hypothesis that the grains are authentic examples of Precambrian pollen can only be treated with incredulity at present, even among creationists.|
If contamination was impossible, creationists are left with an even less tenable position. If it is accepted that contamination is impossible, then another explanation is necessary in which the pollen must have gotten into the formation as it was being formed. The only land-reforming event within the 6,000-year timescale that creationists can point to is the Biblical global flood. But if such an event occurred in the Roraima, we should find pollen worldwide, buried in innumerable locations. "Precambrian" pollen occurs, as a rule, only in isolated incidents.
Thus, even if the evolutonist model is flawed, the creationist model is vastly less probable.
 See also
- ↑ See here.
- ↑ Acritarchs are basically just a central cavity surrounded by one or more layers of organic material, which approximates pollen.
- ↑ Graphitization is basically the reformation carbon from unordered forms into flat planes; for (a little bit) more information, see here and here (esp. here).
- ↑ See here.
- ↑ See here and here.
- ↑ See here and here for explanations of ultrasonic cleaning.
- ↑ 1.00 1.01 1.02 1.03 1.04 1.05 1.06 1.07 1.08 1.09 1.10 1.11 1.12 1.13 1.14 1.15 1.16 1.17 1.18 1.19 1.20 "Occurrence of Pollen and Spores in the Roraima Formation of Venezuela and British Guiana", R. M. Stainforth (full-text republishing)
- ↑ http://gsabulletin.gsapubs.org/content/115/3/331.abstract
- ↑ http://bulletin.geoscienceworld.org/content/84/5/1677
- ↑ "COBERTURAS SEDIMENTARES DO MESOPROTEROZÓICO DO ESTADO DE RORAIMA - AVALIAÇÃO E DISCUSSÃO DE SEU MODO DE OCORRÊNCIA", NELSON JOAQUIM REIS & ALBERTINO DE SOUZA CARVALHO. Revista Brasileira de Geociências, 26(4):217-226, dezembro de 1996. "These proterozoic basins seems to be of multiple age, ranging from 1.7 to 1.4 Gya with gaps of m.y."
- ↑ "Pollen suggests flowers bloomed before dinosaurs walked the earth", Charles Choi, NBC News
- ↑ 6.0 6.1 6.2 6.3 6.4 6.5 6.6 "The evolutionary paradox of the Roraima pollen of South America is still not solved", Emil Silvestru
- ↑ "Pollen Paradox", Emil Silvestru and Carl Wieland
- ↑ Stainforth, RM (1966) Occurrence of Pollen and Spores in the Roraima Formation of Venezuela and British Guiana. Nature 210: 292 - 294.
- ↑ 9.0 9.1 9.2 9.3 "DISCUSSION OF THE AGE OF THE RORAIMA FORMATION", R. M. Stainforth
- ↑ Bailey, P.B.H., Possible microfossils found in the Roraima Formation in British Guiana, Nature 202:384, 25 April 1964.
- ↑ Rădulescu, D. (Ed.,), "Petrologie magmatică şi metamorfică", Didactică şi Pedagogică, Bucharest, p. 208, 1981.
- ↑ 12.0 12.1 12.2 12.3 12.4 12.5 https://gsa.confex.com/gsa/2006AM/finalprogram/abstract_111790.htm
- ↑ 13.0 13.1 13.2 13.3 13.4 13.5 "MICROFOSSILS PRESERVED IN HIGHLY METAMORPHOSED ROCKS: A NEW WINDOW INTO THE EARLY BIOSPHERE?" Schiffbauer, J.D., L. Yin, R.J. Bodnar, A.J. Kaufman, F. Meng, J. Hu, B. Shen, X. Yuan, H. Bao, and S. Xiao. 2007.
- ↑ 14.0 14.1 14.2 14.3 14.4 14.5 14.6 J. D. SCHIFFBAUER, A. F. WALLACE, J. L. HUNTER JR, M. KOWALEWSKI, R. J. BODNAR, AND S. XIAO. "Thermally-induced structural and chemical alteration of organic-walled microfossils: an experimental approach to understanding fossil preservation in metasediments". Geobiology (2012), 10, p. 402–423.
- ↑ Schiffbauer, JD et al. (2007) Ultrastructural and Geochemical Characterization of Archean–Paleoproterozoic Graphite Particles: Implications for Recognizing Traces of Life in Highly Metamorphosed Rocks. Astrobiology 7(4): 684-704.
- ↑ "Exceptional preservation of fossil plant spores in high-pressure metamorphic rocks". Sylvain Bernard, Karim Benzerara, Olivier Beyssac, Nicolas Menguy, Francois Guyot, Gordon E. Brown Jr., Bruno Goffé. Earth and Planetary Science Letters 262 (2007) 257–272.
- ↑ 17.0 17.1 "Precambrian Pollen", Glenn Morton
- ↑ 18.0 18.1 "Claim CC341", Mark Isaak
- ↑ 19.0 19.1 "Spores and Pollen", Micropalaeontology Unit, University College London
- ↑ Batten, DJ (1982) Palynofacies, palaeoenvironments and petroleum. Journal of Micropalaeontology 1: 107-114.
- ↑ Ercegovaca, M and Kostić, A (2006) Organic facies and palynofacies: Nomenclature, classification and applicability for petroleum source rock evaluation. International Journal of Coal Geology 68(1-2): 70-78.
- ↑ "Limonite"
- ↑ "MICROFOSSILS", Jere Lipps, University of California Museum of Paleontology
- ↑ Green, R (2009), The Lost World of Venezuela's Mt. Roraima, Los Angeles Times (July 24, 2009)
- ↑ Santos, JOS et al. (2003) Age, source, and regional stratigraphy of the Roraima Supergroup and Roraima-like outliers in northern South America based on U-Pb geochronology. GSA Bulletin 115 (3): 331-348.
- ↑ Arthur V. Chadwick, "Precambrian Pollen in the Grand Canyon - A Reexamination," Origins, 8:1, 1981