Dear Friends,
By way of introduction I would like to invite you to my website below to explore some scientific evidence I have identified that may have a bearing on the Ho-Chunk peoples of central Wisconsin. I have been interested in the parts of the Ho-Chunk mythology concerning Wojijega, the meteor spirit.
In 2010, I noted some geological evidence which indicated to me that a recent extra-terrestrial event occurred at the quarry known as Glover Bluff, near Coloma WI. I have put forth the evidence of this event with the Geological Society of America last year, in 2011, along with a new hypothesis for the events at Glover Bluff. Later that year I performed some carbon 14 dating which places the event around 1773 but it could have been as early as 1671, around the time when Marquette and Joliet visited the area. They noted a sharp decline in the Ho-Chunk population compared to Joliet, an early explorer.
I think that my work may interest you if you are interested in a factual basis for some of the Ho-Chunk's mythology. Please visit my website for additional details or feel free to call or email. I would very much enjoy discussing the timing of the Wojijega myth with you to determine if the myth coincides with my hypothesized contiental airburst hypothesis at Glover Bluff.
From:
Gene M. Renard
c/o: Wiscah Geologic, LLC
1602 N. Thompson Dr. Suite 407
Madison, WI 53704
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THE GLOVER BLUFF STRUCTURE by Gene M. Renard
INTRODUCTION
The Glover Bluff structure is located near Coloma, WI about 65 miles north of Madison and 48 miles west of Oshkosh. Current geological thinking about the structure is wide ranging. The Glover Bluff structure has remained a mystery, since 1877, when it was first identified. Since then a number of explanations have been written up. None has been proven by scientific evidence.
There are currently three geological views of the Glover Bluff structure; (1) unexplainable disturbance (the default position), (2) full impact crater, and (3) continental airburst.
CURRENT GEOLOGICAL THINKING
Unexplainable Disturbance View - From 1930-1984 geologists viewed the Glover Bluff structure as an unexplainable disturbance which took place in the Paleozoics of Wisconsin approximately 251-470 million years ago. This default position explains the disturbed rocks at Glover Bluff structure as probably resulting from a small graben or syncline in the pre-Cambrian basement. Movement at depth in the basement rocks caused the surface features to subside under this view. It is admitted that the default position can not be proven without extensive geophysical work, and that is unlikely to occur since the quarry is non-economical. One small geophysical study performed there in 1956 was inconclusive. Some very prominent geologists maintain this default position.
Full Impact Crater View - Glover Bluff structure is internationally classified as a full impact crater. This view is by far the most popular view among geologists, although a crater wall has never been observed. In 1983 shatter cones were discovered at the Glover Bluff structure's north hill, suggesting that this structure is part of an impact. Shatter cones are normally found in rocks around the exterior of the impact crater as shocked metamorphic rocks in the basin itself are removed by the impact. So in 1984, the structure was thought to have collapsed along the rim and slumped down the crater wall. Under this view the crater extended to the north and was thought to be as much as seven miles in diameter. This view suggests that a full impact occurred, caused by a meteor that had a diameter of ~281 meters (i.e., the size of Lambeau Field stadium), traveled at ~17 kms/sec., and produced an explosion of ~3,220 megatons. Later versions reduce the crater size downward or locate the structure on a central bulge.
Continental Airburst View - Both the unexplainable disturbance and the full impact crater views are under a challenge. In 2010 the upper layers at Glover Bluff's east hill were excavated, observed, and identified as ejecta, from a continental airburst. An airburst occurs when a hypervelocity object enters the earth's atmosphere and sufficient atmospheric pressures are produced to vaporize the object prior to striking the surface. When this occurs over a continent, this is called a continental airburst. If such an airburst is of sufficient magnitude, it results in a vapor plume and ejecta similar to a full impact, as was photographed on Jupiter in 1994 when the Shoemaker-Levy 9 objects were vaporized by the Jovian atmosphere. The exposed ejecta formation identified at the Glover Bluff structure consists of three rock layers, which are suggestive of a recent airburst.
IDENTIFICATION OF EJECTA AT THE GLOVER BLUFF STRUCTURE
From close inspection of the cross section of the identified ejecta formation, geological observations could be made. These ejecta layers are: (1) Unsorted - no signs of melt-water from the Laurentide ice sheet. (2) Unconsolidated - indicating recent deposition. (3) Stratified - two loosely assembled rock layers separated by a 3" black mat layer. (4) Angular - rock fragments are angular and native, absent of erratic rocks.
SUSPENDED ORGANIC DETRITUS AT GLOVER BLUFF STRUCTURE
There are in-situ tree trunks suspended in the upper layer above the black mat. Subsequent carbon 14 testing of the tree trunks has eliminated: (1) Deposition by the glaciers at ~15.0 thousand years before present. (2) Deposition by the Firestone bolide at ~12.9 thousand years before present. (3) Recent deposition by modern earth moving equipment.
TIMING OF THE CONTINENTAL AIRBURST AT GLOVER BLUFF STRUCTURE
A date of 170 ± 18 radiocarbon years before present, or AD 1666 - AD 1813, with a midpoint of AD 1773, was determined through carbon 14 testing of the suspened organic detritus. This means that the upper ejecta layer at the Glover Bluff structure was deposited around the time of the American Revolution, since that is approximately when the tree died.
PARTIAL RING STRUCTURE AT GLOVER BLUFF STRUCTURE
The continental airburst view proposes that the Glover Bluff structure is a partial ring structure centered at east hill. The identified ejecta layers record a substantial bolide's airburst, having an atmospheric shock wave powerful enough to down-warp a massive slab of dolomite, -200 feet in elevation, into the underlying Cambrian formations; producing ejecta in the atmosphere. This airburst then precipitated the downward flow of super-heated gases from a fast moving fireball; producing an embedded burn mat layer. The carbon 14 evidence suggests that the upper layer was deposited at the Glover Bluff structure when central Wisconsin was a desolate wilderness, possibly inhabited by sporadic native American tribes.
HISTORICAL ASSOCIATIONS
The Ho-Chunk settlements of central Wisconsin were lost by 1673 near the beginning of this time window. Historians estimate a Ho-Chunk population of between 8,000-20,000 in Wisconsin in 1634 when the french explorers passed through the area (Jean Nicolet reported 5,000 warriors). By 1673 the Ho-Chunk population is estimated to be only 500 in Wisconsin (In 1673 Marquette and Joliet observed, no humans, or settlements, from the portage area (Portage, WI), down the Wisconsin and Mississippi Rivers, to the 40th parallel). And it is interesting that the Ho-Chunk have an oral tradition of a meteor spirit. Historians offer various explanations for the decline in Ho-Chunk population.
GLACIAL DRIFT OR EJECTA AT GLOVER BLUFF STRUCTURE
Both the unexplainable disturbance and the full impact crater views have interpreted the upper layers at Glover Bluff structure as glacial drift. The continental airburst view suggests that glacial drift has been misinterpreted, which has happened frequently at other impact structures, and the layers are actually ejecta or fall-back material. For example, ejecta material from the Ries impact crater in southern Germany was once thought to be evidence for a "Ries glacier". The material flow forming the upper layer at the Glover Bluff structure occurred recently as demonstrated by carbon testing. The best mechanism of emplacement is ejecta, given the associated fracturing and down-warping of the underlying formations, particularly as glacial drift has now been disproven.
DOLOMITE OUTLIERS IN WISCONSIN
The Glover Bluff structure is an Ordovician dolomite, Prairie du Chien formation, outlier. The Prairie du Chien formation in Wisconsin produced an escarpment that trends from the southwestern part of the state to the northeastern part. The escarpment is noted for its salient dolomite outliers that were cut off and converted into isolated, flat-topped buttes or mesas. There are masses of these outliers across southern Wisconsin. In contrast the escarpment's northern 150 miles are almost entirely without such outliers. The Glover Bluff structure lies in the transition zone in central Wisconsin. In the transition zone the outliers are smaller and farther apart than in the southern part of the state. Glover and Bald Bluffs are so small that they did not appear on the 1982 Bedrock Geology Map of Wisconsin.
STRATIGRAPHY AT GLOVER BLUFF STRUCTURE
Exposed at the surface are 200 feet of capstone from the Ordovician period (440-490 million years ago), the Prairie du Chien Formation (Shakopee and Oneota Fms.), which is a gray, cherty, weather resistant, dolomite. Below this and still in place are the rocks of the Cambrian period (540-490 million years ago) listed from top to bottom; the Jordan sandstones (20 feet), the Trempealeau dolomites (30 feet), the Mazomainie sandstones (75 feet), the Franconian sandstones (25 feet), and the Dresbach sandstones (100 feet). The rocks beneath these formations remain completely concealed and consist of the following Cambrian period formations; the Eau Claire (200 feet), the Mt. Simon (300 feet) . The final layers underlying the Glover Bluff structure are the Pre-Cambrian basement rocks of the Canadian Shield.
ROCK DISTURBANCE AT GLOVER BLUFF STRUCTURE
Early workers noted that this outlier was, at some point in the past, highly disturbed, and broken into isolated and distinct fault blocks which formed west, north and east hills. Two minor fault blocks, abutting the main blocks, were so severely disturbed that they were steeply tilted from 65-80 and 45-100 degrees, respectively. Severe down-warping of dolomite slabs is apparent to the observer in the exposure at west hill. Severe tilting, fragmentation, and charring can be seen at north hill. And east hill forms a bowl or capture basin that plunges 10 degrees to the west. By 2004 it was noted that the disturbance extends in all directions from the quarry and has been traced to a circular area of one mile in diameter.
ELEVATION ANOMALY AT GLOVER BLUFF STRUCTURE
Elevation surveys of the base Ordovician dolomites, in 1930, show that there is an elevation discrepancy of -200 vertical feet at west hill, in comparison to Bald Bluff (an undisturbed outlier just 2 miles to the southwest of the area of interest). This is a very important point. The Bald Bluff outlier is higher in elevation, as are other outliers in the area. There is only one conclusion. The Glover Bluff structure has subsided into the underlying Cambrian formations by as much as 200 feet.
SHOCK AND THERMAL METAMORPHISM AT GLOVER BLUFF STRUCTURE
The Glover Bluff structure features a variety of metamorphic rocks including both thermal and shock varieties: (1) various metamorphic breccias, and (2) shocked dolomite.
Thermal Metamorphic Rocks - Red, yellow, and white metamorphic breccias were described in 1930 although little was known about impacts at the time. Dolomitic, to cherty, to glassy breccia inclusions show a range from angular to rounded to round. These inclusions are suspended in matrices which range from sandy to quartzitic.
Shock Metamorphic Rocks - In-situ shatter cones, which are diagnostic of impact events, were formally identified at north hill in 1983 and 2004. However shatter cones are not well developed and are not often found at the Glover Bluff structure.
Question - How can a small graben or syncline, in the pre-Cambrian basement rocks, produce shock metamorphism typical of impact structures near the surface? The obvious answer is that they can not. There is no explanation in the default position for the presence of metamorphic rocks. In 1930 geologists had no concept that impact structures existed.
Geologists in 2004 however, who have considerable knowledge of impact structures, and present vivid evidence in the form of shock metamorphism (i.e., shatter cones), hesitate to embrace the full impact crater view. They term the Glover Bluff structure a confusing structure and a mystery hill, and gravitate back to the default position. No microscopic evidence of impact related shock metamorphism, normally required for impact crater designation, has been presented to the scientific community, from the Glover Bluff structure. Until microscopic evidence of shock metamorphism is produced, the impasse between the unexplainable disturbance and full impact crater views will continue.
RECLASSIFICATION OF GLOVER BLUFF STRUCTURE
Glover Bluff is currently classified as a full impact crater and is included in the Earth Impact Database, as well as the 2005 DNAG Geologic Map of North America (GSA), although geologists remain skeptical. A reclassification of the structure as a continental airburst was put forward in 2011. This view explains the disturbances and metamorphic rocks, at or near the surface. This view explains the extended area of disturbance to the one mile diameter, which has been traced by geologists. Finally this view explains the surface deposition (i.e., ejecta), which has been identified.
AIRBURST PHYSICS GENERALLY
A notable airburst at Tunguska, which occurred in Russia in 1908, produced neither rock disturbance or metamorphism. This suggests that an airburst at the Glover Bluff structure, which exhibits both rock disturbance and metamorphism, would have been larger than Tunguska; a 5 megaton event, which did 10-15 megatons of surface damage.
Physicists indicate that airbursts may have produced metamorphic glasses at several other sites, which include the Muong-Nong tektites of Southeast Asia and the Libyan Desert glass of western Egypt. This suggests that airbursts are capable of surface metamorphism. Airbursts occurring on Jupiter, a gas giant with no solid surface, in 1994, have produced effects similar to full impacts with nothing more than the dense Jovian atmosphere to impact.
PRO-CONTINENTAL AIRBURST VIEW AT GLOVER BLUFF STRUCTURE
2011 GSA ANNUAL MEETING - MINNEAPOLIS, MN - Comments from leading impact experts, glacial geologists, regional geologists, and other professional members in attendance, was sought, and ranged from mildly supportive to reasonably skeptical. Supporting comments concerning the continental airburst view, and the identification of ejecta at Glover Bluff structure are summarized: (1) Impact experts agreed that the physics of airburst events are not well understood by physicists and studies are in their infancy. (2) Impact experts suggested that more thought should be given to hypervelocity atmospheric shock wave formation (i.e., both bow and aft waves) at speeds greater than MACH 1 for objects larger than aircraft. (3) Glacial geologists from Iceland agreed that these layers clearly did not demonstrate the characteristics of glacial deposition, which is normally comprised of clays, alluvial rocks (rounded), supra-glacial materials, and erratic rocks transported from distant locations. (4) Geologists agreed that the layers are unsorted, angular, Ordovician dolomites suspended in a fine powder. The lack of sorting indicates that they were not likely subjected to melt-waters from the glaciers. The angularity of the deposits shows that the rocks were not subjected to large quantities of melt-water over prolonged periods of time. (5) There was consensus that the layers are unconsolidated consisting of loose sediments. The lack of grain cementation, compaction, or re-crystallization favors a recent deposition, constrained by the known presence of glacial ice approximately 15.0 thousand years ago. (6) Since the tree trunks are suspended or embedded in the upper layer there was consensus that the wood is associated (i.e., in-situ) with the upper layer of the deposit. (7) There was agreement that a wood sample should be carbon 14 tested, but that radiocarbon testing alone would not establish the nature of this event, but provide a narrower time window. (8) There was agreement that metamorphic rocks normally associated with impacts are accepted, and that known shatter cone evidence needs to be better demonstrated and documented. (9) There was agreement that in-situ microscopic evidence of an impact needs to be obtained to convince experts that an atmospheric shock wave passed through these rocks. (10) There was agreement that analysis of the burn mat layer for impact and burn markers, such as iridium and charcoal, is important to establish that the black mat was produced by a fire event.
AGAINST-CONTINENTAL AIRBURST VIEW AT GLOVER BLUFF STRUCTURE
2011 GSA ANNUAL MEETING - MINNEAPOLIS, MN - The main objections raised by the GSA members to the continental airburst view, and the identification of ejecta at Glover Bluff structure are summarized: (1) Impact experts questioned whether shatter cones have been found at Glover Bluff. (2) Impact experts questioned whether the physics of an atmospheric shock wave from an airburst located above Glover Bluff could produce the force necessary to drop a 200' thick dolomite slab, as much as 200 vertical feet, into the underlying Cambrian sandstones, and fracture it into three separate fault blocks, producing the ejecta. (3) Impact experts were concerned that this interpretation could support a discredited Clovis Comet Theory occurring 12.9 thousand years ago. (4) Regional geologists argued that the black mat layer is possibly a soil layer. (5) One geologist suggested the trees appear to be in their growth positions. (6) Regional geologists thought the tree trunks could be the result of a re-advance of the glacial ice front approximately 15.0 thousand years ago, similar to the buried forest at Two Creeks, WI. (7) It is possible that these deposits could be the result of earth moving equipment from quarrying operations over the past 50 years.
CONCLUSION
There are currently three geological views of the Glover Bluff structure; (1) unexplainable disturbance (default position), (2) full impact crater, and (3) continental airburst.
None of the views have been proven by science. The unexplainable disturbance view is the default position, since 1930, but does not explain the metamorphic rocks which are known to exist near the surface at the Glover Bluff structure. The full impact crater view is the internationally accepted view, since 1984 (based on shatter cones at north hill and the identification of a circular structure), although clear evidence of a crater is absent. The continental airburst view, introduced in 2011, explains the disturbance, elevation anomaly, and metamorphism near the surface, however airburst physics are not well understood, and it is unknown whether an airburst can cause the extent of disturbance, subsidence, and metamorphism that are known at the Glover Bluff structure.
SOURCES: Bedrock Geology Map of Wisconsin, (1982), Wisconsin Geological Survey. Boslough, M., and Crawford, D., (2008). Low-altitude airbursts and the impact threat. International Journal of Impact Engineering, 35, p. 1441-1448. Decade of North American Geology, General Geology of North America, (2005), Geological Society of America. Dott, R.H., and Attig, J.W., (2004), Roadside Geology of Wisconsin. Mountain Press Publishing Company, pp. 256-257. Ekern, G.L. and Thwaites, F.T., (1930), The Glover Bluff Structure, A Disturbed Area in the Paleozoics of Wisconsin. Transactions of the Wisconsin Academy of Sciences Arts and Letters, 25, p. 89-97. Koeberl, C., and Anderson, R. R., (1996). Manson and company: impact structures in the United States. Geological Society of America Special Paper, 302, p. 1-29. Koenen, K.H., (1956), Geophysical Studies in South Central Wisconsin, Master of Science Thesis, University of Wisconsin. Firestone, R.B., et al., (2007). Evidence for an extraterrestrial impact 12,900 years ago that contributed to the megafaunal extinctions and the Younger Dryas cooling, Proceedings of the National Academy of Sciences of the United States of America, 104, p. 16016–16021. Melosh, H.J. and Beyer, R.A., Impact calculator at ASU website. Rampino, M.R., (1994). Tillites, Diamictites, and Ballistic Ejecta of Large Impacts, The Journal of Geology, Vol. 102, No 4 (July, 1994), pp. 439-456 Read, W.F., (1983). Shatter cones at Glover Bluff, Wisconsin, Meteoritics, v. 18, p. 241–243. Read, W.F., (1984). The circular structure at Glover Bluff: What and where it is, Meteoritics, 19, p. 295–296. Renard, G.M., (2011), Ejecta Strata of Recent Origin Have Been Identified in Central Wisconsin at Glover Bluff Impact Site, Geological Society of America, Abstracts with Programs, Vol. 43, No. 5, p. 306. See
http://gsa.confex.com/gsa/2011AM/finalprogram/abstract_191489.htm Renard, G.M., (2011), Results of Radiocarbon Testing of the Ejecta Strata at Glover Bluff Site Near Coloma, Wisconsin, WISCAH Geologic, LLC, Geological Research and Publishing Co, See
http://www.wiscah.com Stuiver, M., and Reimer, P.J., (2011), CALIB RADIOCARBON CALIBRATION PROGRAM. Irving, R.D., (1877), Geology of Central Wisconsin, Geology of Wisconsin, vol. 2, p. 577. Syverson, K.M., Colgan, P.M., (2004). The Quaternary of Wisconsin: a review of stratigraphy and glaciation history, in Elhers, J. and Gibbard, P .L. eds. Quaternary Glaciations--Extent and Chronology, Part II: North America. Amsterdam, Elsevier Publishing, p. 295-311. Wasson, J.T., (2003). Astrobiology, 3, p. 163–179.
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November 25, 2011
FOR IMMEDIATE RELEASE:
RESULTS OF RADIOCARBON TESTING OF THE EJECTA STRATA AT GLOVER BLUFF SITE NEAR COLOMA, WISCONSIN.
Madison, Wisconsin USA
RENARD, Gene M., Wiscah Geologic, LLC, 3224 Memorial Drive, Two Rivers, WI 54241,
gene.renard@wiscah.comWiscah Geologic, LLC (WISCAH), a Wisconsin limited liability company, has completed two carbon 14 isotope tests of a sample of organic detritus taken from the upper strata at Glover Bluff Site (Glover Bluff) in central Wisconsin, USA. The radiocarbon tests were performed to narrow the time window of the deposition of these strata. Both tests results were identical.
The sample tested at 170 ± 18 14C age yr BP [1s error]. A calibration of cal AD 1733 to cal AD 1813 [95.4 % (2s) cal age ranges; 0.666374 relative area under distribution] was performed. The lowered confidence level of the calibration is due to carbon 14 isotope variations in the atmosphere during the past 300 years. Complete calibration results are shown below.
"We view the test results favorably since we have narrowed the time window concerning the deposition of the upper rock layers at the Coloma Airburst Site to 170 ± 18 RADIOCARBON YEARS BEFORE PRESENT. Astonishingly, the evidence is mounting that these ejecta layers were deposited very recently, around the time of the American Revolutionary War, when central Wisconsin was a wilderness populated by native American groups, when French fur traders navigated the Fox and Wisconsin Rivers in canoes. The search for supporting evidence will now be vastly more targeted." Gene M. Renard, November 25, 2011
The raw radiocarbon date does not support a competing published interpretation by Ekern and Thwaites, 1930(1), which classified the upper strata at Glover Bluff East Hill as glacial drift that was deposited 20 - 15 thousand years ago. Additionally this evidence suggests that these strata are not associated with the Firestone, et.al., 2007(2) bolide theory which dates back 12,900 years. This evidence also suggests that these strata were not deposited by modern earth moving equipment in operation over the past 50 years.
ADDITIONAL TESTING
Research on the existing evidence for shatter cones at Glover Bluff will be performed and documented. Diagnostic analysis of rock samples obtained from Glover Bluff in the lab needs to be performed in 2012. The detritus will be tested for IR. Beyond that geochemical analysis near the black mat stratum for iridium, charcoal, and other markers is being considered. Coring from nearby Pleasant Lake, Wood Lake, School Section Lake, and Lake Burnita to identify any fire events during the past 500 years is under consideration.
(1) Ekern, G.L. and Thwaites, F.T. (1930), The Glover Bluff Structure, A Disturbed Area in the Paleozoics of Wisconsin. Transactions of the Wisconsin Academy of Sciences Arts and Letters, 25, p. 89-97.
(2) Firestone, R.B., et al., (2007). Evidence for an extraterrestrial impact 12,900 years ago that contributed to the megafaunal extinctions and the Younger Dryas cooling, Proceedings of the National Academy of Sciences of the United States of America, 104, p. 16016–16021. ___________________________________________________________
CALIB RADIOCARBON CALIBRATION PROGRAM* Copyright 1986-2011 M Stuiver and PJ Reimer
*To be used in conjunction with: Stuiver, M., and Reimer, P.J., 1993, Radiocarbon, 35, 215-230.
Labcode001 Glover Bluff - Sample #1 Radiocarbon Age 170±18 Calibration data set: intcal09.14c # Reimer et al. 2009 38 Year moving average
One Sigma Ranges: [start:end] relative area [cal AD 1671: cal AD 1681] 0.136247 [cal AD 1744: cal AD 1777] 0.473047 [cal AD 1788: cal AD 1805] 0.231837 [cal AD 1934: cal AD 1945] 0.153014 [*cal AD 1950: cal AD 1951*] 0.005855
Two Sigma Ranges: [start:end] relative area [cal AD 1666: cal AD 1688] 0.147247 [cal AD 1733: cal AD 1813] 0.666374 [cal AD 1926: cal AD 1952*] 0.186379
Ranges marked with a * are suspect due to impingement on the end of the calibration data set
# PJ Reimer, MGL Baillie, E Bard, A Bayliss, JW Beck, PG Blackwell, # C Bronk Ramsey, CE Buck, GS Burr, RL Edwards, M Friedrich, PM Grootes, # TP Guilderson, I Hajdas, TJ Heaton, AG Hogg, KA Hughen, KF Kaiser, B Kromer, # FG McCormac, SW Manning, RW Reimer, DA Richards, JR Southon, S Talamo, # CSM Turney, J van der Plicht, CE Weyhenmeyer (2009) Radiocarbon 51:1111-1150.
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October 11, 2011
FOR IMMEDIATE RELEASE:
EJECTA STRATA OF RECENT ORIGIN HAVE BEEN IDENTIFIED FOR TESTING IN CENTRAL WISCONSIN AT GLOVER BLUFF IMPACT SITE
Madison, Wisconsin USA
RENARD, Gene M., Wiscah Geologic, LLC, 3224 Memorial Drive, Two Rivers, WI 54241,
gene.renard@wiscah.comWiscah Geologic, LLC (WISCAH), a Wisconsin limited liability company, has completed a field evaluation of the natural history of the Glover Bluff Impact Site (Glover Bluff) near Coloma, Wisconsin. There have been four previous studies of the Glover Bluff structure: In 1930, 1956, 1983, and 1984. The 1984 study proposed that the structure is positioned on the rim of a crater having a seven mile diameter. The WISCAH evaluation was unable to confirm this.
The 1983 study produced shatter cones in support of an extraterrestrial origin to the disturbance of rock formations at Glover Bluff. The WISCAH evaluation observed: Numerous brecciated metamorphic rocks, curving fault surfaces, vertically tilted dolomite strata, down-warping (synclinization) and severe fracturing of the Lower Ordovician fault blocks (Prairie du Chien Formation - Shakopee and Oneota Members).
Based on the 1930 study, the WISCAH evaluation noted that three distinct Lower Ordovician fault blocks at Glover Bluff were once a single contiguous Prairie du Chien Escarpment outlier, similar to Bald Bluff just two miles to the southwest. The former outlier was fractured into three main fault blocks which were down-warped into the underlying Cambrian formations by as much as 200 feet. Two abutted minor fault blocks were tilted from 65-80 and 45-100 degrees, respectively. The WISCAH evaluation concluded that the fault blocks recorded a central ring structure and the outlier was fractured by a Tunguska-like airburst.
The 1930 study interpreted float (i.e., diamicton) at Glover Bluff as glacial drift. A recently exposed section of the East Hill at Glover Bluff reveals that float are unconsolidated, native, angular, Lower Ordovician dolomite. Clast sizes vary from 2 feet in length to pebble size, set in matrices of fine grains. Three distinguishable strata are: A lower stratum (5 feet); a black mat stratum (3 inches); and an upper stratum (4 feet). Stratification does not necessarily support a glacial genesis. And float are poorly sorted; not suggestive of a glaciofluvial process. No glacial erratics are observed. Organic detritus are noted in the upper stratum near the black mat. The WISCAH evaluation reinterpreted float at Glover Bluff as ejecta and proposed that the ejecta were deposited recently, less than ~15,000 years before present, after Late Wisconsinan ablation of the margin of the Green Bay Lobe.
Samples of the organic detritus have been obtained and carbon 14 isotope testing is currently being performed on Sample #1 of 8. WISCAH testing will focus initially on the carbon dating of the deposition at Glover Bluff's upper strata. Age of deposition will have immediate implications as to the veracity of the ejecta interpretation and will determine whether the deposition is naturally occurring or not.
FREE DOWNLOADS
"THE GLOVER BLUFF STRUCTURE" by Gene M. Renard (2012). This most recent write-up is now available as a free download. Simply proceed through the checkout, enter user information, and select the download switch.
COMMERCIAL PUBLICATIONS
"AIRBURST - Glover Bluff: Coloma Airburst Site" is available through WISCAH in electronic format. The unabridged version contains 5 figures, 5 interpretive geological cross sections, 6 diagrams, and 7 high resolution photographs from inside this incredible geological structure (58 MB pfd).
SCIENTIFIC PUBLICATIONS
"Ejecta Strata of Recent Origin Have Been Identified in Central Wisconsin at Glover Bluff Impact Site" - Author: RENARD, Gene M., October 10, 2011, Geological Society of America, Abstracts with Programs, Vol. 43, No. 5, p. 306.
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