NORTH ZANESVILLE METEOR CRATER
ALSO CALLED THE DILL0N FALLS METEOR CRATER/ASTROBLEME
Believe it or not, the North Zanesville Meteor Crater has been estimated to be similar in size to Meteor Crater in Arizona. The object creating the impact side is estimated to have been the size of a semi-truck. This information is contained in the original presentation/report included at the end of this blog. Other references within the same report list conflicting sizes of the crater.
An astrobleme is a scar on the Earth left by meteorite impact. Some of the astroblemes have been filled in by weathering and erosion. To give an example of how fast areas are filled in, take the normal farm pond. If the pond is not dredged to stay open and deep, it will fill in with sediment and disappear within 25-years. The life expectancy of the average farm pond is therefore 25-years. Larger holes in the surface of the Earth take longer to fill. It was not until humans studied Earth from space that numerous meteor craters on Earth were identified.
An astrobleme has been identified in north Zanesville, Ohio. It was first imaged in 1993, having been identified by Pete MacKenzie. Located north of the Dillon Falls area of the Licking River in the Falls Township of Muskingum County, the remnants can be found off state route 146 near Barkers Run Road. The actual crater is under ground, having been filled in with sedimentation since its creation. It was imaged through seismic instruments.
Since 1993 there have been several seismic projects completed over the impact crater. It was during these studies that the central uplift region of the crater was discovered. The twenty feet of uplift area was almost 2-miles across. Not all meteorite impact craters have the centered uplift section. Smaller impact sites have no central uplift. The Wikipedia cross section illustration below displays the uplift common to many impact craters. There has been speculation the uplifted region may have been caused by a fault.
The crater appears to rest above the Trenton Limestone.
When one of the seismic investigations met with a mishmash of material, it was originally thought to be a collapsed limestone feature due to karst type erosion. Geologist Greg Mason, NGO Development Corporation of Newark,Ohio, at the 21 April 2003 Ohio Geological Society meeting in Columbus, Ohio suggested the feature was not caused by limestone erosion, but was an “impact crater/astrobleme.”
Another seismic site showed a “ripple” in the earth, perhaps an “effect from the crater.” The meteorite impact was severe enough that it caused fracturing of the Precambrian basement rock in Ohio. The great meteorite impact created what is called a “ripple” of earth surrounding the crater. The surrounding ripple is about 1-mile beyond the crater edge. The Glenwood shale is thin over the rim of the crater and thicker in the center of the crater. Mr. Greg Mason of the NGO Development Corporation of Newark, Ohio reported that wells were drilled into the crater. There is Glenwood Shale (Middle Ordovician) rock which lies flat. The shale is thinner over the rim of the crater and thickens toward the center. When a test well was drilled in the center of the crater, there was 130-feet of “dirty” sand. Some drill sites found clean sand.
The impact has been dated to the time of the Knox Unconformity when the impact bored into the Knox Limestone. The Knox Unconformity is a section of dolomite, the surface of which has been eroded. The boundary between the Knox Limestone and the Wells Creek formation contains the unconformity. We have no fossil record of what may have been eroded from the Knox Limestone. The erosion of the original Knox Limestone occurred toward the beginning of the Ordovician period of time.
After the initial impact, the crater collected water and became a lake in the early Ordovician period of time. Sand gradually eroded from the surrounding land of sand and Rose Run Sandstone. It eventually partially filled the lake. There is 1700-feet thick region of a mishmash of various undifferentiated rock, sandstone, sand and fill in the center of the crater. The sand in the crater solidified into what is called the St. Peter Sandstone.
A team from Wright State University performed gravity and magnetic surveys over the feature with no concrete results.
In the 1990's when a team of students arrived in Zanesville from the University of Michigan to study the North Zanesville Meteor Crater surroundings, I was surprised. I had not heard of any meteor crater remnants in my home town. I asked, how is it that a team from out of state knew about the meteor crater but Ohioans did not? Consequently, the seismic wells drilled at the site for gas and oil exploration revealed more of the crater formation. The information presented has been exciting to learn. The large crater remained unknown because it had been filled in over the years due to erosion of surrounding rock. Although it may have originally been as large as the famous Meteor Crater of Arizona, it was basically hidden from view at the surface of the Earth. One day I would like to take metal detectors to see if any of the meteorite debris ever made it to the surface of the Earth. Most likely not, for the rock into which it crashed is deep underground.
Information about the north Zanesville meteorite crater was presented by Greg Mason at the 21 April 2003 meeting of the Ohio Geological Society in Columbus, Ohio (USA). Mr. Mason is associated with the NGO Development Corporation, Newark, Ohio. NGO Development Corporation is an energy cooperative organization. That paper, obtained from the Internet site http://www.newark.osu.edu/facultystaff/personal/jstjohn/Documents/Geology-talks/Mason-talk.htm is included below.
Dillon Falls Astrobleme (The North Zanesville Crater)
Greg Mason (NGO Development Corporation, Newark, Ohio, USA)
Ohio Geological Society meeting (Columbus, Ohio, USA)
21 April 2003
The Dillon Falls Astrobleme was first imaged in 1993. It has since been drilled by CGas (several wells), NGO Development Corporation, Oxford Oil Co., and Dick Poling. The feature has gone unnamed for a while. Some have suggested Pete’s Astrobleme [after Pete MacKenzie, who first identified it on a seismic line], but here it is being called the Dillon Falls Astrobleme. It is located in the subsurface of Falls Township of Muskingum County, just northwest of Zanesville, and just north of Dillon Falls on the Licking River.
Three seismic projects have been completed over the feature:
1) FM-1-92/93 extended - a total of 4.5 miles long from southwest to northeast.
2) FM-2-93 - two miles long from east to west, on the western end of the anomaly.
3) OH-DE 94 - four individual lines from north to south.
The Murray Unit # 2, the Murray Unit # 5, the Lett Unit # 1, the West Unit # 1, the Holbein Unit # 3, the Vandenbark # 3, another Murray # 2, and the Wilson Unit # 3 have all been drilled on the feature.
The main anomaly is 1.7 miles across on the FM-1-92/93 extended line. This line shows a central uplift. The anomaly appears to be developed on the top of the Trenton Limestone [upper Middle Ordovician, sensu traditio] as well, but this is due to differential compaction.
The original Murray Unit # 2 drilled by CGas, the 1st well drilled, was wet. The Murray Unit # 5 well, drilled by Poling, was identical (also wet). The West Unit # 1 well drilled by NGO was a dry hole, but it is producing from the Clinton Sandstone [Lower Silurian] & the # 3 sand of the Rose Run Sandstone [Upper Cambrian]. Another well drilled on the anomaly hit 90’ of sand and produces gas in the upper part. The Lett and the Holbein wells, drilled by NGO, are both production wells. These all have disruption at the Knox Unconformity [~ Cambrian-Ordovician boundary]. The West Unit # 1 was drilled on what appeared to be remnant on the outside of the feature. The Lett well was successful - it was drilled inside the feature, in the trough, and had 100 million cfg of cumulative production before it went wet.
A composite of the first two seismic lines (4.3 miles long, from west to east to southwest) has been put together. It shows the basement is a mishmash - it has been suggested that this is a karst collapse feature, but Greg Mason says no, and suggests it is an impact crater/astrobleme.
The Wilson Unit # 3 was not actually on a remnant, but appears to be on a ripple, a structural effect from the crater, ~1 mile from the anomaly. It appears to be an oblate feature, which doesn’t fit with what we know about astroblemes, but current knowledge about this crater is incomplete.
Eight wells have been drilled:
1) Murray Unit # 2-1875 - in October 1994 by CGas - wet.
2) Wilson Unit # 3 - in October 1994 - on the interior of the feature.
3) West Unit # 1 - in November 1999 by NGO - on the crater rim - the only well that strayed from vertical drilling.
4) Lett Unit # 1 - in November 1999 by NGO - produced 100 million cfg.
5) Vandenbark # 3 - in July 2000 - wet.
6) Murray # 2 - in July 2000 by Oxford - produced gas for 6-9 months (60-90 million cfg).
7) Holbein Unit # 3 - in February 2001 by NGO.
8) Murray Unit # 5 - in May 2002 by Poling - on the central uplift & proved there was no central uplift (stratigraphically flat to slightly lower (5’ lower) than the Murray # 2) - wet.
See a maximum of 90-135’ of Rose Run/crater center sand fill in the feature.
Greg Mason correlated e-logs hung on the top of the Gull River Limestone [Middle Ordovician].
The Holbein & the Lett & the Murray # 2 were drilled in the crater. The top-Glenwood Shale [Middle Ordovician] picks are all flat. The Glenwood thins over the crater rim and thickens in the crater. The Murray # 2 well was drilled in the center of crater development - got 130’ of sand, but a dirty sand. The West well was drilled to the lower Copper Ridge Dolomite [Upper Cambrian], below a developed B Zone. The B Zone picks are not present in the Holbein and are very low & ratty in the Murray # 2.
The sand in the crater center isn’t a real Rose Run Sandstone.
Holbein - 20’ of clean sand.
Lett - 90’ of clean sand, with 14’ thick gas cap, and the rest full of water.
The wells drilled so far are characteristic of a water driven reservoir.
Mattingly well - used as a regional well, to the north of the feature.
Top Trenton structure map - shows an anomaly, but it is subtle - the Trenton is high to regional over the anomaly.
Knox Unconformity structure map - again, a subtle pullup, but it is there.
Copper Ridge Dolomite structure map - picks are present, but they are forced by picks for mapping, and are probably not useful for correlation.
Glenwood isopach map - shows the anomaly very well - get 80+ to 90+ feet of Glenwood. Get a thicker Glenwood over the anomaly.
The Middle Ordovician Knox Unconformity erosional surface - have 1700’ of stratigraphy between the Knox and basement. The impact occurred during development of the Knox Unconformity. It fractured the Precambrian basement. Can see undifferentiated crater fill (1700’ of it) under the Knox in this feature. A lake formed during Knox Unconformity time. Sand fills the lake (eroded from the surrounding plain of old Rose Run Sandstone deposits) - have concurrently eroding Rose Run Sandstone filling the crater lake, technically producing St. Peter Sandstone in the crater. Get 20’ of crater rim uplift. Also get a ripple (ripples?) ~1 mile out around crater.
Finished talk with a short movie of a gas flare from the Holbein.
The Dillon Falls Astrobleme is ~same size as Meteor Crater in Arizona - its asteroid is estimated to be the size of a semi-truck.
Get 90 feet of 14-16% porosity sand in the Lett well.
No good stratigraphic markers below the Rose Run in the undifferentiated crater fill - have doubtful B Zone picks, and no Conasauga picks, etc.
What about encountering fractures during drilling? The Murray well went artesian, so pressures may be sufficient to keep wells together when drilling potentially fractured rock in the feature.
Another well close to the crater rim is planned on being drilled in fall 2003.
Wright State academic gravity & magnetic surveys over the feature were a wash - they showed no anomaly.
Smaller craters shouldn’t have a central uplift (those smaller than ~3 miles across - this one is ~1.7 miles across). The original image of a central uplift is probably a fault, if it is anything at all. The seismic data is all being reprocessed to get a better look.
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[Locality info. on the e-logs of six of the wells mentioned in this talk:
Murry Unit # 5 well (permit # 8077) - 644’ NL, 242’ EL, Lot 12, 1st Quarter Township, Falls Township, Muskingum County, Ohio, USA.
D. Murray # 2-1875 (permit # 7892) - 1130’ NL, 595’ EL, Lot 12, 1st Quarter Township, Falls Township, Muskingum County, Ohio, USA.
Holbein Unit # 3 (permit # 8306) - 4930’ SL, 123’ EL, 2nd Quarter Township, Falls Township, Muskingum County, Ohio, USA.
Lett Unit # 1 (permit # 8241) - 760’ SL, 100’ EL, NE Quarter, 2nd Quarter Township, Falls Township, Muskingum County, Ohio, USA.
C. Wilson Unit # 3 (permit # 7925) - 445’ SL, 1940’ EL, 2nd Quarter Township, Falls Township, Muskingum County, Ohio, USA.
West Unit # 1 (permit # 8235) - 5913’ NL, 1403’ EL, 2nd Quarter Township, Falls Township, Muskingum County, Ohio, USA.]