Stratigraphic and Geomorphologic Field Guide to Mill Creek Park

Stratigraphic and Geomorphologic Field Guide
to Mill Creek Park, Youngstown, Ohio
Dr. C. R. Mattheus, Assistant Professor
Department of Geological and Environmental Sciences
Youngstown State University
Youngstown, OH 44555
2013
ACKNOWLEDGEMENTS
Putting this field guide together would have been impossible without the help of friends
and colleagues who accompanied me on exploration trips to, provided me with research
materials on, and shared their knowledge and appreciation for Mill Creek Park. My gratitude
goes out to Lisa Stowe and Mike Norton for joining me on many hiking trips throughout the park
that provided the photographs you will see in this manuscript. With the many distractions our
modern society presents us with it is nice to see others take joy in simply being outdoors. I
would like to take this opportunity to especially thank Ann Harris, whose unparalleled
knowledge of the park’s geology provided the very foundation for this guide. Thank you for
sharing your materials, your time, and your infectious enthusiasm for Mill Creek Park.
TABLE OF CONTENTS
LIST OF FIGURES …………………………………………………………………………...… 4
PALEOZOIC HISTORY OF MILL CREEK PARK …………………………………….………6
Review of stratigraphic concepts ……………….……………………………….………. 7
Rock units ……………………………...………………………….…….…..……7
Contacts between rock units …………….……………………….…............…… 7
Stratigraphy ……………………………………………………………….…..…. 8
Time …………………........................................................................................... 9
Paleozoic Setting of Mill Creek Park ………………………………...…….…………... 11
Mississippian Period ………………….…..………..………...………………… 11
Pennsylvanian Period …...…………….…….…..……………………………… 12
Prominent lithologies in the park ……………………………….………..…….. 13
Field Trip ………………..……………………………………..………………………. 15
Stop 1 – The Narrows…………………………..………………….…………… 18
Stop 2 – Mississippian-Pennsylvanian contact ……………….………...……… 22
Stop 3 – Bear’s Den Quarry ………………………………………………….… 25
Stop 4 – Lanterman Gorge …………..……………………………………...….. 28
QUATERNARY HISTORY OF MILL CREEK PARK ……………………..…………...…… 31
Pleistocene glaciations …………………………..………….………………………….. 32
Field Trip ………………..……………………………………..………………………. 35
Stop 5 – Skunk Cabbage Patch …………………………………..……….……. 35
Stop 6 – The Hiawatha Flats …………………………….…………….……….. 36
Stop 7 - Amphitheater ………………………………………………………….. 37
Stop 8 – Bear’s Den Ravine ……………………………………………………. 42
2
Stop 9 – Lily Pond ………………………………..…….……………………… 46
Stop 10 – Lake Glacier ……..………………………………………………….. 48
REFERENCES …………………………………………………………………………....…… 49
3
LIST OF FIGURES
Photograph of Mississippian rock outcrop at the Narrows in Mill Creek Park ……...….Title Page
Photograph of Mississippian brachiopod fossils found at the Narrows …………………………. 6
1. Conformable contact types ………………………….……………………………………… 8
2. Chart of geologic time ………………………………………………....…………..……… 10
3. Formation of a disconformity ……………………………….………..…………..……….. 11
4. Early Mississippian map of Ohio ………………………………..…………….…….…….. 12
5. Middle Pennsylvanian map of Ohio …….….…………………..…………………………. 13
6. Stratigraphic column for NE Ohio ……………………..……………………....…………. 14
Photograph of the Umbrella Rocks ……………………..……………………………………… 15
7. Overview map of Mill Creek Park ………………………………..……..……....………… 16
8. Topographic map for Stops 1 and 2 ……………….………………………..…..…………. 17
9. Image of Mississippian rock outcrop at the Narrows …………………………..…………. 19
10. Mississippian fossils in rock from the Narrows ……………………………...…………… 20
11. Identified Mississippian fossils from the Narrows ……………………..…….…………… 21
12. Mississippian-Pennsylvanian contact …………………….………….……….…………… 22
13. Sharon conglomerate …………………………………………………………..……..…… 23
14. Mississippian hummocky cross-strata ……………………………..………….….……….. 23
15. Topographic map for Stop 3 ……………………….……………..……………….………. 24
16. Tabular cross-strata in Massillon Sandstone ……….……………..………………………. 25
17. Massillon Sandstone quarry ………………………..……………………………………… 26
18. Topographic map for Stop 4 ……………………………………………….……………… 27
19. Photograph of Lanterman Falls …………………………………………………………… 29
4
20. Umbrella rocks ………………………………………………….…………………..…….. 29
21. Iron oxide in spring water …………………………………………..………………..……. 30
22. Plant fossil in Massillon Sandstone ………….………………………………….………… 30
Photograph of Glacial Grooves ………………………………………………………………… 31
23. Map of glacial features in Mahoning County ……………………….…………………..… 32
24. Map of the preglacial Mill Creek and its tributaries ……………..………………………... 33
25. Topographic map for Stops 5, 6, and 7 …………………………..………….…………….. 34
26. Photo of bedrock outcrop along Mill Creek river bank …………………………………… 35
27. Photo of Mill Creek paleovalley fill ……………………………….…..….………………. 36
28. Photo of the Hiawatha Flats ………………………………….…………….……………… 37
29. Elevation transects across select valley locations ……………….………………..……….. 38
30. Shaded relief map of Pleistocene terraces …………………………..…………………….. 39
31. Photo of vertical scarp along Amphitheater …………………………………….….……… 40
32. Photo of Amphitheater ………………………………………………………….….……… 40
33. Topographic map of Stop 8 …………………………………….………………………….. 41
34. Photo of Bear’s Den Ravine ………………………………………………………………. 43
35. Photo of Sharon Sandstone ……………………...……………………….………………... 43
36. Photo of differential weathering ……………….…………..…………………..………….. 44
37. Photo of glacial grooves on an erratic ………………..…………………………………… 44
38. Topographic map of Stop 9 …………………………………………..……….…………... 45
39. Topographic map of Stop 10 ………………….…………………….…………………….. 47
40. Photo of Lake Glacier …………………………………….………………………………. 48
5
PALEOZOIC HISTORY OF MILL CREEK PARK
Brachiopod fossils (~1 cm in length) found in Mississippian sedimentary rocks of Mill Creek Park.
6
REVIEW OF STRATIGRAPHIC CONCEPTS
Rock Units
A hierarchy of rock units differentiated by rock character (color, texture, composition, fossil
content, etc.) is defined and named (in order of decreasing size thickness and extent) in
accordance to an established classification scheme and a distinct nomenclature (International
Stratigraphic Guide, 1994):
-
Group (consisting of two or more formations)
o Formation (primary unit of rock correlation)

Member (named lithologic entity within a formation)

Bed (named distinctive layer in a member or formation)
Contacts between Rock Units
Contacts between rock strata can be conformable or unconformable: Conformities are surfaces
that separate younger strata from older strata along which there is no evidence of non-deposition
or erosion while unconformities are surfaces of erosion or non-deposition separating younger
strata from older rocks, representing a significant hiatus or gap in the geologic record (Boggs,
2006). Several different types of unconformity exist that are differentiated largely on the type of
rock involved, the occurrence of erosion or non-deposition, and the structure of the rock units.
There are also three main types of conformable contacts between vertically stacked rock
units that reveal information about changing depositional conditions: 1) sharp, 2) gradational,
7
and 3) intercalated (Figure 1). Sharp contacts represent a very sudden change in the nature of
sediment deposition, recognized by one distinct lithology changing to another abruptly.
Gradational contacts represent a change in lithology that is gradual while intercalated contacts
indicate fluctuating conditions between two states, recognized by the change of one lithology to
another as a stacked alternating pattern.
Figure 1 – Conceptual depiction of the three types of conformable contact.
Stratigraphy
Most sedimentary rocks we encounter are basin deposits; sea level represents the base level of
erosion; materials deposited above sea level are subject to weathering and erosion while those
deposited below may remain untouched and lithify over time in response to deep burial (with
increasing temperature/pressure conditions) and cementation. If brought back to the surface by
uplift or other tectonic processes, these ancient marine and/or coastal deposits are available for
us to analyze.
8
The geologic sub-field of stratigraphy is most simply defined as the science of rock
strata; it deals with rock succession and age relationships, which relies on understanding rock
form, distribution, composition, fossil content, and physical and chemical properties (Neuendorf
et al., 2005). The most fundamental principles of stratigraphy were formulated by Nicholas
Steno in 1669; known as Steno’s Principles, they provide a blueprint for analyzing layered
sedimentary rocks, which document Earth evolution over time: 1) The principle of superposition,
2) the principle of original horizontality, and 3) the principle of lateral continuity (Prothero and
Dott, 2010). The principle of superposition states that in any succession of undeformed strata the
oldest stratum lies at the bottom with successively younger ones above, sequentially. The
principle of original horizontality suggests that stratification in basin deposits occurs essentially
horizontally since sediment particles settle from fluids under the influence of gravity; steeplyinclined strata are indicative of disturbance post-deposition. The principle of original lateral
continuity states that strata originally extend in all directions until they thin to zero or terminate
against the basin edge.
Time
Geologists divide time into broad segments and place events into an organized global time-table
called the Geologic Time Table (Figure 2). While exact boundaries between successive time
units are continuously debated and refined as additional data are presented, the geologic time
table serves as a reference for those seeking to place rocks into a general time-perspective;
broken up into eras, periods, and epochs in decreasing length, respectively, the framework of
these time units is determined by global stratigraphic correlation and radiometric age dating.
9
Figure 2 – Chart showing divisions of geologic time and their spatial representaiton in Ohio. Wavy lines are
indicative of unconformities (i.e. gaps in the record) in Ohio. Figure adapted from Coogan, 1996. Of particular
interest to those looking to experience the geology of Mill Creek Park is the unconformity separating the
Mississippian and Pennsylvanian as this is an easily recognized surface in several locations within the park.
10
PALEOZOIC SETTING OF MILL CREEK PARK
The Mississippian Period
The history of the rocks exposed in Mill Creek Park begins in the late Paleozoic, when a
mountain building episode known as the Acadian orogeny created what we would today consider
the ancestral Appalachian Mountains. The mountain range, produced by a tectonic collision
event between landmasses, extended from the Northwest Territories of Canada to South
Carolina. Sediment eroded from this landscape shed westward into the Absaroka Sea, a shallow
water body covering most of North America; the east coast of this sea covered Ohio during the
Mississippian period (Wicander and Monroe, 1993; Figure 4). Accumulation of vast amounts of
sediment over time would eventually form the sandstone and shale rocks we recognize as the
basement rock of NE Ohio and Mill Creek Park. With the progression of the Mississippian,
these basin materials were uplifted and partially eroded; renewed sediment deposition in NE
Ohio during the Pennsylvanian Period atop the surface of erosion produced a disconformity in
the rock record, which can be viewed in Mill Creek Park (Figure 3).
Figure 3 – Illustration showing the development of a disconformity, a surface separating conformable sections of
conformable sedimentary rocks by a surface representing erosion (i.e. unconformity), with respect to sea level,
which represents the base level of erosion; everything above sea level is subject to erosion and removal from the
rock record, everything below stands a chance for preservation by continuous deposition and subsidence.
11
Youngstown
Cincinnati
Peninsula
Figure 4 – Map of early Mississippian Ohio and surrounding areas showing inferred inundation by a shallow
seaway and resultant deposition (sand-mud pattern) and the terrestrial realm (gray). River systems indicate direction
of clastic sediment transport and are not meant to represent the true locations of channels. Figure adapted from
Coogan, 1996.
The Pennsylvanian Period
Whereas the late Mississippian Period was associated with subaerial exposure and erosion in NE
Ohio, the Pennsylvanian experienced renewed deposition in response to land subsidence and
lowland inundation by seawater (Figure 5). Minor sea-level fluctuations across a shallow
landscape dotted with irregularities produced conditions favorable for the formation of swamps
and wetlands (Wicander and Monroe). The abundant plant matter that was able to sequester in
these environments produced the abundant plant fossils we find incorporated into the
Pennsylvanian rocks of Mill Creek Park.
12
Youngstown
Figure 5 – Map of middle Pennsylvanian Ohio and surrounding areas showing inferred inundation by a shallow
seaway and resultant deposition (sand-mud pattern) and the terrestrial realm (gray). River systems indicate direction
of clastic sediment transport and are not meant to represent the true locations of channels. Figure adapted from
Coogan, 1996.
Prominent Lithologies in the Park
We are able to view rocks of the Mississippian Cuyahoga Formation in the park as well as rocks
belonging to the lower Pennsylvanian Sharon Formation; the latter belongs to the Pottsville
Group and contains several members, such as the Sharon Sandstone and the Sharon
Conglomerate, both of which are found within Mill Creek Park (Figure 6). The Sharon
sandstone, the most prominent lithology in Mill Creek Park and the one comprising the many
massive cliffs and ledges in the park, is easily recognized by its light brown color and prominent
cross beds. The sandstones in the park are rich in quartz and lithic fragments; however, the
Sharon Formation, which can be found outcropping along in many areas of Ohio’s glaciated
13
Appalachian plateau province, encompasses rock types ranging from shale to conglomerate.
Some of the park’s cross-bedded sandstone is interbedded shale, suggesting deposition within
shifting fluvial and deltaic environments. Tree fossils furthermore attest to the preservation of
Pottsville Group*
shallow terrestrial environments (Belfast, 1979).
Homewood Sandstone & Coal Members
Tionesta & 3b Coal Members
Upper Mercer Limestone Member
L. Mercer Limestone Member
L. Mercer #3 Coal Member
Lowellville Limestone Member
U. Massillon Sandstone Member
L. Massillon Sandstone Member
Sharon #1 Coal Member
Sharon Sandstone/Conglomerate Member
Fossil content is
demarked by ‘*’
Figure 6 – Stratigraphic column showing the common lithologies in NE Ohio. In Mill Creek Park, the lower
Pennsylvanian Pottsville units rest unconformably atop the Mississippian Cuyahoga Formation. The figure is modified
from Coogan (1996) to list formations and members of the Pottsville group specific to Youngstown area.
14
FIELD TRIP – PALEOZOIC HISTORY OF MILL CREEK PARK
Photograph of the ‘Umbrella Rocks’ north of Lanterman Falls in Mill Creek Park.
15
1
10
Lake
Glacier
Lily Pond
Bear’s Den Ravine
9
2
Fig. 8
3
8
Lake Cohasset
Fig. 15
7
5
6
Lanterman Gorge
Amphitheater
The Flats
4
Fig. 18
Figure 7 – Shaded relief map showing field trip stops (1-10); stops 1-4 deal with the local stratigraphy; stops 5-10
discuss the late Quaternary history of the area. Stops are indicated by yellow stars and labeled accordingly.
16
Mahoning River
Stop 1
Lake
Glacier
Stop 2
Lily Pond
Figure 8 – Topographic map of lower Mill Creek Park showing locations for field trip stops 1 and 2 (red stars).
17
STOP 1 – The Narrows
This stop gives us an opportunity to examine the oldest rocks exposed in the park, which belong
to the Mississippian Cuyahoga formation. The best exposure of the Cuyahoga formation in
Youngstown is just up-stream of Mill Creek’s juncture with the Mahoning River, below the Ice
Pond Dam at the lower end of Mill Creek Park (Figure 8). The Mississippian-Pennsylvanian
contact is easily recognized by the ledge formed by the massive, coarse-grained Pennsylvanian
Sharon sandstone atop thinner, interbedded sand-, silt-, and mudstones of the Mississippian
Cuyahoga formation (Figure 9). This contact is found at elevations around 270 m at this
location, approximately 17 m above the Mahoning River. The exposed section is described in
great detail by Stephenson (1933) and summarized by Belfast (1979), whose descriptions served
as a template for the description given below, which provides metric units rather than U.S. units:
-
-
Pennsylvanian strata
o Pottsville series
 Sharon formation
 ~3 m of gray, coarse-grained sandstone
Mississippian strata
 Cuyahoga formation
 ~12 m of interbedded sandstone and shale: the sandstone is drab
to yellowish-gray, fine grained, dense, and occurs in beds from one
to ~2 to ~15 cm in thickness; the mostly argilleceaous shale is
drab to greenish towards the top and bluish-gray in the lower
section.
 ~2 m of gray, fine-grained dense sandstone.
 ~7 cm of gray, fossiliferous ore nodules forming a discontinuous
band.
 ~2 m of blue-gray, slightly arenaceous shale containing few thin
beds of bluish-gray to drab sandstone and regular bands of
fossiliferous iron nodules.
18
2m
Figure 9 - Mississippian strata in outcrop just below the ice dam (Site 1). The Pennsylvanian rocks are
covered by soil and vegetation above the upper-most (sandstone) bed seen in this image.
19
The ore layer at the base of the dense Mississippian sandstone bed is an iron-hardened
layer cemented to the sandstone above. This iron-stained basal layer is the product of
groundwater deposition from the underlying shale units. Fossils are most abundant within this
basal layer and are easily obtained by splitting the iron-bearing layers away from the sandstone
(Figure 10). Fossil remains of small brachiopods can be found in the shale directly underlying
the ore band (Stephenson, 1933), including Camarotechia sageriana (Winchell, 1862; Figure
11A), Orbiculoidea herzeri (Hall and Clarke; Figure 11B), Chonetes pulchella (Winchell), and
Chonetes sp. (Figure 11C). Fossils are heavily enriched in localized poorly consolidated muddy
shell beds that break apart easily to expose well-preserved marine fossils, including the
aforementioned brachiopods in addition to crinoid and bryozoans (Figure 11D). Trace fossils are
also common to these lithologies (Figure 11E).
Figure 10 - Freshly-broken shell bed (composed mainly of brachiopods) held together by iron-rich mudstone.
20
1 cm
1 cm
1 cm
1 cm
1 cm
Figure 11: A) Camarotechia sageriana fossil (brachiopod); B) Orbiduloidea herzeri fossil (brachiopod); C)
Chonetes sp. Fossil (brachiopod); D) a fossilized crinoid stem; and E) trace fossils (i.e. burrows). All specimens
were found in spring of 2013 at the Narrows (Site 21). Fossils shown in parts B and C are from a fossil-rich bed
containing other gravel-sized clasts, indicative of heavy reworking.
21
STOP 2 – Mississippian-Pennsylvanian Contact
The contact between Mississippian and Pennsylvanian strata in NE Ohio represents an uneven
surface of erosion (i.e. disconformity; Figure 3). This surface is exposed in outcrop for less
than100 m along the road running parallel to the western shoreline of Lake Glacier (Figure 12).
The Sharon conglomerate (Figure 13) or sandstone marks the basal Pennsylvanian bed overlying
the Mississippian rocks, which are characteristically finer-grained and thinly bedded/laminated
(sandstones and mudstones; Stephenson, 1933). Hummocky cross-stratification (Figure 14) can
be identified in the Mississippian rocks, which is indicative of shallow water deposition.
Sharon formation (Pennsylvanian)
Cuyahoga formation
(Mississippian)
Figure 12 - Photograph taken in May of 2013 of the roadside outcrop of the Mississippian-Pennsylvanian
contact to the west of Lake Glacier. Close-ups of the rock strata showing sediment structures are shown in
Figures 13 and 14.
22
1 cm
Figure 13 (left): Image of the Sharon
conglomerate forming the base of the
Pennsylvanian at Stop 2 (Figures 8 and 12).
Pebbles up to 1 cm in size are embedded in a
sandy matrix. This lithology is characteristic
of fluvial deposition, which defines the
Sharon formation.
Figure 14 (below): Photograph taken in
May of 2013 of the Mississippian strata of
the Cuyahoga formation underlying the
Pennsylvanian Sharon conglomerate (Figure
13) at Site 2 (Figures 8 and 12). Shown are
undulating sets of cross-laminae that are
concave-up (swales) within three distinct
sand beds, which gently cut into each other
with curved erosional surfaces. This type of
sedimentary structure, known as hummocky
cross-stratification, is reflective of shallowwater deposition in storm-dominated
environments (Boggs, 2006).
23
Stop 3
Bear’s Den
Ravine
Lake
Cohasset
Figure 15 – Topographic map of lower Mill Creek Park showing locations for field trip stop 3.
24
STOP 3 – Bear’s Den Quarry
In the latter years of the 19th century several quarrying operations of the Pennsylvanian
Massillon sandstone were carried out. Many of these quarries can be found adjacent to roads.
One such quarry is located along Bear’s Den Rd., which runs parallel to the eponymous creek
(Figure 15). The company quarrying this specific site failed to achieve success given high
operational costs, poor sandstone quality, and the uneven thickness of the rock strata; however,
some of the sandstone obtained from the quarry was incorporated into bridges, dams, and other
structures within the park (Belfast, 1979). The quarry is recognized as the high sandstone cliffs
exposed to the north along the roadside (Galaida, 1941). This particular outcrop also showcases
phenomenal cross bedding in the Massillon sandstone (Figure 16). Drill marks/holes in the
sandstone attest to the quarrying activity (Figure 17).
Figure 16 Photograph taken in
May of 2013 of
Massillon sandstone
cross bedding seen in
the Bear’s Den Quarry
(Stop 3; Figure 15).
The yellow arrow
indicates inferred
paleo-flow direction to
produce the tabular
cross beds seen in this
image seen paralleling
the dashed black lines.
The dashed white lines
delineate the crossbedded sedimentary
package. Differential
weathering can be seen
to follow the
depositional
architecture.
25
Figure 17 - Photograph taken in May of 2013 of the Massillon sandstone exposed along the roadside to the north
of Bear’s Den creek (Stop 3; Figure 15). The yellow circle marks the location of a drill hole from quarrying. The
rock outcrop measures ~2 m in height on average from ground to soil cover along this section.
26
Amphitheater
Flats
Stop 4
Lanterman
Gorge
Lake
Newport
Figure 18 – Topographic map of lower Mill Creek Park showing locations for field trip stops 4 and 5.
27
STOP 4 – Lanterman Gorge
The Massillon sandstone is most prominently exposed in the park between Lake Cohasset and
Lake Newport, where it occurs in thicknesses exceeding 24 m and comprises high cliffs along
both sides of the narrow and gorge-like Mill Creek valley (Belfast, 1979; Figures 18 and 19). A
walk from Lanterman’s mill down-stream takes hikers by some extraordinary cross-bedding
within the sandstone. Another feature noticeable along this section of the valley includes the
‘Umbrella’ or ‘Cave’ rocks, formed by preferential weathering and the formation of overhangs
(Figure 20). Softer layers that are easily weathered and carved out of the valley sides tend to
form piles of rock debris that can be underneath the overhangs or at the bottom of the ravine.
The overhangs, comprised of harder, more erosion-resistant rocks are the ‘umbrellas’. An
additional factor in their formation is provided by the presence of ephemeral springs that can be
seen trickling down the rock faces in select spots after rain events. The iron content of the
Massillon sandstone is visible in the reddish staining of rocks by the spring water (Figure 21).
An important weathering agent is presented by these waters, which help loosen the cementing
agents of the rock by dissolution; freeze-thaw cycles during the cold months also act to help
induce frost wedging, which mechanically cleaves off weakened layers. The Umbrella rocks are
continuously undergoing change in response to weathering that is very noticeable on human
timespans. The dissolution of underlying rock translates to weakened support for the overlying
roof rock, eventually leading to collapse; the huge sandstone blocks at the base of the valley
floor below attests to these events.
The sandstone is also found to contain numerous plant fossils (mainly Sigillaria and
Lepidodendron, which were scale trees; Figure 22) and, occasionally, thin streaks of coal below
Lanterman’s Bridge on the east side of the valley. Some of these fossils are several meters in
28
length and can be seen underneath the overhanging ledges, where they appear to have been
massed together by currents and buried with by the drifting sand (Stephenson, 1933).
Figure 19 (above) - A view of
Lanterman falls and the massive
Massillon sandstone prominently
overhanging the plunge pool.
Figure 20 (left) – Image of the
Umbrella Rocks (a.k.a. Cave
Rocks) just north of Lanterman
Falls along the hiking trail.
29
Figure 21 – Groundwater seepage through the Massillon sandstone, precipitating iron oxide at the surface.
Figure 22 – Trunk portion of the scale tree Sigillaria fossil (~1 m in length) found incorporated into the ceiling of
an overhang.
30
QUATERNARY HISTORY OF MILL CREEK PARK
Photograph of glacial grooves on a weathered granite boulder found in Bear’s Den Ravine.
31
Pleistocene Glaciations
After sub-aerial exposure and the removal of Mesozoic and Tertiary rock strata the Quaternary
Period (1.6 million years ago to present) re-shaped the NE Ohio landscape into the terrain we
find today. Around two-thirds of Ohio was covered by mile-thick ice during Quaternary glacial
periods and the geomorphology of the NE Ohio is heavily shaped by glacial processes (Figure
23). Research within Mill Creek Park suggests that the preglacial Mill Creek entered the Park
area from the south, passing the Hiawatha flats and the Amphitheater before meandering to
course over the area now occupied by lower Lake Cohasset; from there it is inferred to have
occupied the area now affiliated with Lily Pond and flowed in a broad meander across the lower
end of the present-day Lake Glacier and onward towards the Mahoning (Galaida, 1941; Figure
24).
Figure 23 – Map of glacial features in Mahoning and surrounding counties. Figure adapted from ODNR (2005).
32
Fig. 39
Fig. 38
Fig. 33
Fig. 25
0
0.25
0.5
1
1.5
Kilometers
2
Figure 24 - Map of Mill Creek Park and surrounding area showing the approximate location of the pre-glacial
drainage system and highlighted map sections.
33
C
Amphitheater
Stop 7
C’
B
Stop 6
Flats
B’
Stop 5
A’
A
Figure 25 - Topographic map of lower Mill Creek Park showing locations for field trip stops 5, 6, and 7. A-A’, BB’, and C-C’ indicate the locations of elevation transects shown in Figure 29.
34
STOP 5 – Skunk Cabbage Patch
This stop is situated south of the Suspension Bridge, on the opposite side of the Hiawatha Flats
(Figure 25). Steep cliffs of Massillon sandstone tower above the trail for much of the short walk
from the bridge to Stop 5 (Figure 26); however, you will notice that as you turn the bend into a
broad, shallow floodplain the cliffs disappear. This is the area known as “Skunk Cabbage
Patch”. The floodplain here cuts into the hillside, forming a swampy are surrounded by
gradually-sloping hillsides which are depressed at the top (Figure 27). These hillsides, which are
devoid of sandstone beds, give way to steep sandstone cliffs less than 100 m upstream. The
hillside area between these rock outcrops, which coincides with the swampy floodplain along its
base, is comprised of soft, easily eroded material and represents a cross-section of the pre-glacial
Mill Creek valley, which is largely filled in with till. Galaida (1941) shows this valley extends to
the northeast from this location, crossing the flats, and meandering into the location today known
as the Amphitheater before continuing on a north-ward trajectory towards Lake Cohasset (Figure
24).
Figure 26 - Image of bedrock confinement.
35
Figure 27 - Image of loosely consolidated fill material of the Paleo-Mill Creek.
STOP 6 – The (Hiawatha) Flats
Borings in valleys and hilltops alike have mapped the course of the pre-glacial Mill Creek valley
(Galaida, 1941). A drill hole from around 100 m west of the Hiawatha Flats (Figure 28) sampled
glacial till (mainly sand and gravel) for ~45 m before hitting bedrock; geologists estimate that
the bed of the pre-glacial Mill Creek to sit ~30 m below the present level of the flats.
It is suggested that the pre-glacial Mill Creek valley was twice as deep and three times as
wide as the present valley in some locations (Belfast, 1979). The width of pre-glacial valley is
seen in the Hiawatha flats region, where steep sandstone cliffs represent the bounding surface;
the gorge that stretches from the flats upstream to Lanterman’s mill is a product of the recent,
post-glacial incision of Mill Creek. The difference in morphology between the two is showcased
36
in Figure 29; Lanterman Gorge is a deeply incised, narrow valley while the pre-glacial Mill
Creek valley is much broader. It must be noted that the elevation transects show the modern
surface topography, not the base of the valley, which is much deeper based on boring evidence.
Figure 28 - Image of the ‘flats’.
STOP 7 – The Amphitheater
The erosional powers of the present Mill Creek have partially excavated portions of the glacial
till that had filled in the old valley. Unconsolidated materials filling in the pre-glacial valley are
more easily transported away and so the post-glacial Mill Creek was able to remove and expose
some of its old valley; in other places the present-day creek is bedrock-bound. The excavation of
glacial till from the old valley eventually formed the Hiawatha flats (Figure 28) and the
Amphitheater, which is another fluvial terrace occupying a slightly higher elevation (Figure 30),
suggesting that the morphologic feature is older than the Hiawatha flats. Both features were
37
created by the present stream directing its flow against the hillsides, creating a channel that
looped about the area; the channel was later abandoned when the stream took its present course,
leaving the Amphitheater and the Hiawatha flats behind (Galaida, 1941).
Lanterman
Gorge
Mill Creek
Flats
Amphitheater
Figure 29 – Elevation transects based on 1/9 NED USGS elevation data across: A) Lanterman Gorge, B) Hiawatha
flats, and C) the Amphitheater; transect locations are shown in Figure 25.
38
Scarp
Scarp
Amphitheater
Flats
Figure 30 – Shaded relief map of the Hiawatha flats and Amphitheater and surrounding terrain; notice the scarp
separating the Amphitheater from the Flats; the difference in elevation between the two terraces is ~2 m (Figure 29).
A vertical scarp of ~ 2m in elevation separates the terrace which includes the Hiawatha
Flats from the Amphitheater (Figures 31 and 32). The implication is that the Amphitheater
terrace is an older feature produced prior to Mill Creek incising to produce a terrace at a lower
elevation, the Hiawatha flats (Figures 28 and 30). A smaller vertical scarp separates the
Hiawatha flat from the modern floodplain (Figure 30).
39
Figure 31 – Image of a vertical scarp (~2 m) separating fluvial terraces (i.e. the Amphitheater from the Hiawatha
flats). Figure 30 shows this morphology in a shaded relief map.
Figure 32 – Image of the upper fluvial terrace (i.e. the Amphitheater). Figure 31 shows a frontal view of the scarp.
40
Quarry
Stop 8
Quarry
Bear’s Den
Ravine
Figure 33 – Topographic map of lower Mill Creek Park showing locations for field trip stop 8.
41
STOP 8 – Bear’s Den Ravine
The upper portion of Bear’s Den ravine, situated between Old Furnace Rd. and Bear’s Den Rd.
(Figure 33), contains some of the more rugged park terrain. Massive Massillon sandstone blocks
formed from the weathering along jointing planes were left unsupported following the removal
of a more erosive, shale-rich layer underneath (Figure 34). This undercutting and the scattering
of huge sandstone blocks (Figure 35) along the steep ravine slope are largely attributed to the
meandering of Bear Creek (Belfast, 1979).
The cross-bedded blocks of Massillon sandstone contain iron-ore nodules, which can be
seen protruding from the rock as the surrounding sandstone has been removed by weathering
processes (Galaida, 1941). Differential weathering has produced interesting weathering patterns
at the surface of many of the sandstone blocks at this particular location (Figure 36).
Other geologic features of interest include the occurrence of glacial boulders of granitic
composition, which were presumably carried here during the late Pleistocene glacial advance.
Such boulders are known as glacial erratics given that they are ‘out of place’ in terms of rock
composition. Figure 37 shows one such glacial boulder containing groove marks.
42
1 cm
Figure 34: Photo taken in May of 2013 at Stop 4 showing the Bear’s Den Ravine as seen from the western
valley flank looking up-stream.
Figure 35: Photo of fresh Sharon sandstone rock surface showing fairly well-sorted, subrounded to subangular
quartz clasts loosely cemented by silt and mud.
43
Figure 36 Photograph of
sandstoneweathering pattern
typical of many
undersides of rock
overhangs and
influenced by
internal bedding
structures in
addition to the
occurrence of iron
nodules and other
substances of
varying
compositions.
Figure 37- Image
of a heavilyweathered glacial
boulder (i.e.
erratic) composed
of pink (i.e.
feldspar-rich)
granite. Sunglasses
are shown to give a
sense of scale.
Some of the
Massillon
sandstone blocks
are also grooved.
44
Stop 9
Lily Pond
White
Birch Hill
Figure 38 – Topographic map of lower Mill Creek Park showing locations for field trip stop 9.
45
STOP 9 – Lily Pond
Lily Pond is an interesting geomorphologic feature that resulted from the abandonment of a river
meander. Lily Pond is an oxbow lake that formed when Bear Creek and Mill Creek eroded a
pathway through a hill comprised of glacial till, connecting between what are now known as
White Birch Hill and Hemlock Hill (Figure 38).
During preglaical times, the area around Lily Pond was a junction of the preglacial Bear
Creek and the preglacial Mill Creek systems (Figure 38). During the late Quaternary glacial
advance, the old drainage system was re-sculpted and filled in with till (Belfast, 1979). When
the ice sheet receded the present Bear Creek began flowing in a new location. The area between
the present White Birch Hill and Hemlock Hill was filled with debris which turned the course of
the stream around the area occupied by Lily Pond, occupying the area which was once the bed of
the preglacial Mill Creek (Figure 38). As the streams excavated materials from the earth/rock
fragment dam that separated Bear Creek and Mill Creek, the barrier was finally broken through,
joining the two creeks and abandoning the former channel that circumvented White Birch Hill
and forming Lily Pond.
46
Stop 10
Dam
Lake Glacier
Figure 39 – Topographic map of lower Mill Creek Park showing locations for field trip stop 10.
47
STOP 10 – Lake Glacier
This final stop allows us to take a look at Lake Glacier (Figures 39 and 40), a great example of a
glacially carved, U-shaped valley, which is a widening and deepening of the pre-glacial Mill
Creek valley, which extended northward through the adjacent hillside at Stop 10, which is
comprised of till.
Figure 40 – Map of the Mill Creek glacial valley, now occupied by the appropriately-named Lake Glacier.
48
REFERENCES
Belfast, M.A., 1979. A Geologic Field Guide of Mill Creek Park: Youngstown State University,
62 p.
Boggs, S., 2006. Principles of Sedimentology and Stratigraphy, 4th Edition. Upper Saddle River,
New Jersey: Pearson Prentice Hall, 342 p.
Coogan, A.H., 1996. Ohio’s Surface Rocks and Sediments, in: Feldmann, R.M., and Hackathorn,
M. eds. Fossils of Ohio: Ohio Division of Geological Survey Bulletin, V. 70, p. 31-50.
Galaida, E., 1941. Mill Creek Park. Cleveland, Ohio, 104 p.
Neuendorf, K.K.E., Mehl, J.P.Jr., and Jackson, J.A., 2005. Glossary of Geology, 5th Edition,
American Geological Institute. Alexandria, Virginia. 779 p.
Ohio Division of Geological Survey, 2005. Glacial Map of Ohio: Ohio Department of Natural
Resources, Division of Geological Survey, page-size map with text, 2 p., scale 1:2,000,000.
Prothero, D.R. and Dott, R.H.Jr., 2010. Evolution of the Earth, 8th Edition. McGraw Hill, New
York, 518 p.
Stewart, R.L. Sr., and Van Doren, L., 2004. Generalized Column of Bedrock Units in Ohio. Ohio
Department of Natural Resources Geological Survey.
49