GEOLOGICAL SURVEY CIRCULAR 133

September 1951

DETROIT RIVER GROUP IN THE 

MICHIGAN BASIN

By 

Kenneth K. Landes
UNITED STATES DEPARTMENT OF THE INTERIOR

Oscar L. Chapman, Secretary

GEOLOGICAL SURVEY

W. E. Wrather, Director

Washington, D. C.

Free on application to the Geological Survey, Washington 25, D. C.
CONTENTS

Page Page

Introduction............................ ^ Amherstburg formation................. 7

Nomenclature of the Detroit River Structural geology...................... 14

group................................ i Geologic history ....................... ^4

Detroit River group..................... 3 Economic geology...................... 19

Lucas formation....................... 3 Reference cited........................ 21

ILLUSTRATIONS

Figure 1. Location of wells and cross sections used in the study .......................... ii

2. Correlation chart . . . . . . . . . . . . ..................................... 2

3. Cross sections A-«k f to 3-G1 inclusive . ......................;.............. 4

4. Facies map of basal part of Dundee formation. ................................. 5

5. Aggregate thickness of salt beds in the Lucas formation. ........................ 8

6. Thickness map of Lucas formation. ........................................... 10

7. Thickness map of Amherstburg formation (including Sylvania sandstone member. . . 11

8. Lime stone/dolomite facies map of Amherstburg formation ...................... 13

9. Thickness of Sylvania sandstone member of Amherstburg formation.............. 15

10. Boundary of the Bois Blanc formation in southwestern Michigan. ................. 17

11. Structure contour map of Southern Peninsula of Michigan. ....................... 18

12. Oil producing fields ......................................................... 20

Table 1. Wells used in cross sections ................................................. 2?
OTSE60 MONTMORENOY ALPEN

Figure 1. Index map showing location of cross sections and location of wells used in the study.

ii
DETROIT RIVER GROUP IN THE MICHIGAN BASIN

By

Kenneth K. Landes

INTRODUCTION

This report attempts to correlate the outcropping rocks in the type locality of the Detroit River group with the thick sequence of rocks that 

has been explored by many drilled wells in the 

Michigan Basin during the last twenty years. The 

surface nomenclature as recently revised (Ehlers, 

1950) is suggested for the subsurface section in 

place of the heterogeneous collection of names 

now used. The present work revises earlier reports by the writer (1945, a, b, c).

During the preparation of this report the samples have been examined from more than 300 

wells and cores from 9 wells. The writer has 

also drawn upon the work of Enyert (1949) who 

wrote a Doctoral thesis on the sandstones of the 

Detroit River group, and upon Master's theses 

on various phases of Detroit River stratigraphy 

written by Cooley (1947), Saunders .(1948), and 

Tharp (1944). Finally the writer has had the advantage of many consultations in office and field 

with George V. Cohee of the U. S. Geological 

Survey, Professors G. M. Ehlers and E. C. 

Stumm of the University of Michigan, and with 

other geologists of Michigan and Ontario, especially George D. Lindberg (Sun Oil Company, 

Toledo), E. J. Baltrusaitis and K. A. Gravelle 

(Gulf Refining Company, Saginaw), Willard A. 

Sanger (Pure Oil Company, Clare), Joseph 

Lindsay and George WinSton (Carter Oil Co. , 

Grand Rapids), and Charles S. Evans (Union 

Gas Co. , Chatham, Ontario). It is a pleasure to 

acknowledge the help received from these geologists and to thank them for it.

The surface and subsurface sections through 

the Detroit River group in Canada are not included in this report.

NOMENCLATURE OF THE 

DETROIT RIVER GROUP

The lengthy and somewhat complicated history 

of Detroit River group (fig.2) will not be repeated 

here. The Detroit River group which formerly 

was considered as Lower Devonian is now placed 

in the Middle Devonian on the basis of recent paleontologic studies. The principal outcrop area 

of Detroit River is in and near the type locality 

between Detroit and Monroe, Michigan, and in 

the vicinity of Sylvania, Ohio. The most quoted

classification of the Detroit River group is that 

proposed by Lane, Prosser, Sherzer, and 

Grabau (1909). They divided the Detroit River 

("Upper Monroe") group into the Lucas, 

Amherstburg, Anderdon, and Flat Rock formations in descending order. Subsequent experience and observation have verified the 

validity of the Lucas and Amherstburg 

formations. The Flat Rock, however, does not 

merit formation status. At its type locality in 

the town of Flat Rock a bed of carbonate rock 

two or three feet in thickness is poorly exposed 

in the channel of the Huron River. This section 

has not been identified with certainty anywhere 

else; furthermore it is the opinion of G. M. 

Ehlers and the writer, based on geographic 

and structural position of the outcropping strata 

at Flat Rock that these strata actually belong 

within the Lucas formation. The Anderdon 

limestone as described by Lane and others was 

likewise misplaced in the stratigraphic section 

in the opinion of Ehlers (1950). This formation, 

which has a distinctive fauna, actually lies 

above the Lucas at the top of the Detroit River 

group in the type area.

The writer places the Sylvania sandstone 

within the Detroit River group, and considers 

it to be a member of the Amherstburg formation because of the general transition between 

the sandstone an'd the overlying limestone or 

dolomite of the Amherstburg formation in the 

outcrop and in well samples. Carman (1936) 

believes that the Sylvania was deposited in a 

transgressing sea so that the sandstone extends 

across age boundaries within the Detroit River 

group and is therefore of variable age.

Although many geologists have studied the 

Detroit River group in the subsurface, few 

have published the results of their work. Local 

descriptions are included in various oil field 

reports. Newcombe (1933) appears to have been 

the first to publish a description of the Detroit 

River of the Michigan Basin on a regional scale. 

He had recognized earlier the existence of salt 

beds in the Detroit River group as well as in 

the Salina (1929). The Detroit River of northern 

Michigan was described by Landes (1945, pp. 

168-174). A committee of the Michigan Geological Society (George V. Cohee and Helen M.
DEVONIAN

1 SILURIAN

-t1

V

=3

i

j

0.

I

8 

&

|- 

1

j

|

Id

1

2

1 

<

Name of unit

Traverse group

Rogers City 

formntion

Dundee 

formation

Richfield 

member

Filer sandstone 

lentil

Sylvnnia 

sandstone 

member

Bois blanc 

formation

Garden 

Island 

formation

Bass Island 

dolomite and 

Salina formntion

Thickness 

in feet

100475

0-125

0400

68-1124

0-80

0-150

0-100

0200

0-300

0-1000

0-30

84-5000

Description

Limestone 

and shale

Brown 

limestone

Mostly 

limestone

Mostly light - 

colored dolomite 

nnd anhydrite, 

some nalt

Dolomite with 

snndstone locally

Mostly dark-brown 

to black limestone 

or dolomite

Sandstone

Mostly dark to black 

limestone or dolomite

Sandstone with Minor 

dolomite and chert

Entirely cherty limestone or dolomitn

Dolomite

Dolomite, shale 

anhydrite, and 

salt

| Remarks

Bell shale nt base

-EROSIONAL UNCONFORMITY 

Absent in southern and southwestern Michigan. Usually included in the Dundee 

formation in oil field nomenclature

Absent in southwestern corner of Michigan

.coneuvuAt titUft/vucWM//y

Anderon limestone, which overlies Luces formation in noutheastern Michigan, 

not recognizable in subsurface. Lower part of the Lncas of subsurface is 

equivalent to the Lucas of type locality. Upper part of the Lucas may be 

time equivalent of the Columbus limestone across Findlny arch in Ohio. 

Evaporite sequence of rocks of Lucns in subsurface is ordinarily referred 

to in oil field nomenclature as "Detroit River*. The Detroit River group in 

also referred to as the upper Monroe by some geologists

Subsurface only, and mainly in central and western Michigan. Dolomite of the 

Richfield member is principal Detroit River oil resevoir. "Freer sand* is a 

sandstone in the Richfield

-EROSIONAL UNCONFORMITY ____ - - 

Absent in southwestern Michigan. Usually referred to in oil field as "Sylvania 

formntion* or "Black Lime*

Erratic distribution; greatest thickness in Western Michigan

Absent in southwestern, western, northern, and northenstern Michigan

-EROSIONAL UNCONFORMITY - 

'Absent in southwestern and southeastern comers of Michigan

Otiskany sandstone equivalent. Very patcby distribution

-EROSIONAL UNCONFORMITY 

Bass Island dolomite is referred to as the "Lower Monroe" by some geologists

Figure 2. Proposed nomenclature for a part of the subsurface section of the Michigan basin.

2
Martin, editors) issued a multigraphed report in 

1948 on a "A Summary of the Stratigraphy of the 

Southern Peninsula of Michigan" in which the subsurface Detroit River rocks are discussed.

The general practice of geologists in describing 

the subsurface stratigraphic section in the Michigan 

Basin between the Dundee formation and the Bass 

Island and Salina formations is to refer to the evaporite sequence of rocks within the Detroit River 

group as the "Detroit River" and the underlying 

carbonate rocks as the "Sylvania formation" which 

overlies the "Sylvania sandstone" where present.

DETROIT RIVER GROUP

The Detroit River group, which extends throughout the Southern Peninsula of Michigan in the subsurface, is principally a sequence of dolomite, 

anhydrite, (and salt in the northern half of the 

Southern Peninsula), dark brown to black limestone 

and sandstone. In the subsurface the Detroit River 

group is overlain by the Dundee formation of 

Middle Devonian age except in southwestern 

Michigan where the Dundee is absent (fig. 4). The 

Detroit River group overlies the Bois Blanc formation also of Middle Devonian age except in western 

and southern Michigan where it overlies rocks of 

Silurian age (fig. 10).

The subdivisions of the Detroit River group in 

the Michigan Basin are given in the accompanying 

stratigraphic chart. Overlying and underlying units 

are also shown. The Anderdon limestone is omitted 

from the subsurface stratigraphic section because 

it has not been identified anywhere in the subsurface 

except at the Detroit salt mine which is less than 

eight miles from the outcrop.

LUCAS FORMATION

The Lucas dolomite has been redefined by Ehlers 

(1950) as a formation in the upper part of the Detroit 

River group of Middle Devonian age. It is underlain 

by the Amherstburg dolomite of the Detroit River 

group and in the outcrop area is overlain by the 

Anderdon limestone. The dolomite of the Lucas contains fossils diagnostic of Middle Devonian age. In 

order to apply the outcrop terminology so far as 

possible to the sediments of the central part of the 

Michigan Basin, the Lucas is defined as a formation 

in this report that includes the thick evaporite sequence which overlies the dolomite sequence, 

(Richfield member) down dip from the outcrop area.

The Lucas formation in the central part of the 

Michigan Basin consists of beds of Dolomite, 

anhydrite, salt, limestone, and sandstone, in order 

of decreasing abundance. Some of the carbonate 

rock layers are argillaceous, but otherwise shale 

is conspicuously absent. The formation thickens 

from a minimum of 18 ft in a well in Berrien 

County (well 1, cross section A-A1 , fig. 3) in the 

southwestern corner of the State to about 1, 000 ft 

in Clare County (well 33, cross section G-G1 , 

fig. 3). In all cross sections the datum plane is the

Dundee-Detroit River contact. In Michigan the 

Lucas formation crops out only in the southeastern part of the State, along the Detroit 

River a short distance south and southwest of 

the city of Detroit. It crops out across the 

river in southwestern Ontario, and is also 

exposed in Lucas County and other parts of 

northern Ohio. The lower part of the Lucas 

in the central basin area appears to correlate 

with the Anderdon and Lucas sequence of rocks 

in the outcrop. This relationship is shown in 

the accompanying cross sections, especially 

B-B1 (fig* 5). The light color of the dolomite 

and the presence of nodules of anhydrite in the 

outcropping Lucas tend to support this correlation, but the best evidence to date has been 

the discovery of the fossil Prosserellas of the 

type characteristic of the Lucas in cores from 

the State-Maneelona A-l well in the southeastern corner of Antrim County (well 14, 

cross section B-B1 , fig. 5) E. C. Stuxnm, 

verbal communication, July 27, 1950. The 

upper part of the Lucas in the central part of 

the basin, which includes the beds of salt, was 

deposited in a sea of concentrated brine which 

had shrunk to such an extent that it no longer 

covered the present outcrop area. Ehlers 

(oral communication) has proposed the plausible theory that during this time of salt and 

evaporite deposition in the central part of the 

basin, and of no deposition higher on the basin 

flanks, the Columbus limestone was being deposited in normal marine waters farther 

southeast across the axis of the Findlay arch. 

The Columbus limestone, which is widespread 

in central and northern Ohio, but has never 

been recognized on the Michigan Basin side of 

the Findlay arch, Stumm, (oral communication) 

directly underlies the Delaware limestone. The 

Delaware has been correlated (Cooper and 

others, 1942) with the Dundee formation of 

Michigan which overlies the Lucas.

Because the basal part of Dundee formation 

is limestone or dolomite and the upper part of 

the Lucas formation is also limestone or 

dolomite in most places it is not always possible to ascertain the exact position of the contact of the two formations. Furthermore, the 

task is complicated by an erosional unconformity at the top of the Detroit River group that 

cuts out certain beds within relatively short 

distances due to differences in the level of 

erosion. As fossils are not available in most 

cuttings the determination of the contact in wells 

must be based on lithologic differences. The 

following criteria are useful in various parts 

of the Michigan Basin: sand in the basal part Q£ 

the Dundee; chert in the lower part of the 

Dundee; limestone in the Dundee; darker color 

of carbonate rock in the basal part of the 

Dundee; dolomite in the Lucas; and anhydrite 

in the Lucas. Unfortunately, none of these 

criteria is unfailing. In many of the.cuttings 

of the Dundee formation in wells drilled in
c**

O o

A o

ST. §s£
Michigan both sand grains and chert are absent, 

and every one of the other criteria is subject to 

exception.

The Dundee formation is absent in Berrien and 

western Van Buren Counties in the southwestern 

part of the State, where rocks of the Traverse 

group directly overlie the Lucas formation, but it 

is present elsewhere in the Michigan Basin. The 

Dundee formation contains a basal sandstone on 

the southeast flank of the basin in parts of the 

southwestern Ontario peninsula. Sand grains are 

abundant in the basal part of the Dundee in wells 

drilled in southeastern Michigan in western Wayne 

and northeastern Washtenaw Counties. Sand grains 

were also observed in cuttings of basal part of the 

Dundee in individual wells drilled in ten other 

counties in an area extending from Antrim to 

Lena wee and from Oceana to Huron Counties. 

Chert was found in the basal part of the Dundee 

in samples from 13 wells scattered over 6 

counties, all in the southeastern quadrant of the 

Southern Peninsula. Beyond the area in southwestern Michigan where the Traverse group overlies the Detroit River group, the identification of 

the top of the Lucas is most positive where sand 

grains or chert are present in the basal part of 

the Dundee.

Generally, the carbonate rocks in the Dundee 

formation is limestone and that in the Lucas formation is dolomite, but there are numerous exceptions. In many localities the lowermost beds 

of the Dundee are dolomitic, perhaps due to replacement activity by circulating ground waters 

which picked up magnesium salts in the underlying 

dolomite of the Lucas. A facies map of the basal 

part of the Dundee (fig. 4) shows three major and 

at least five minor areas of dolomite in the 

Southern Peninsula. The major areas are: (1) 

southeast of Leelanau and Benzie Counties into 

Clare and Isabella Counties; (2) Livingston County 

and northeast into Tuscola and Sanilac Counties; 

and (3) Cass County and east-northeast into 

Jackson County. The minor areas are scattered 

over other parts of the State except in the northeast part of the Southern Peninsula. The basal 

part of the Dundee is dolomite over about 40 percent of the area of the Michigan Basin and limestone over about 60 percent of the area.

The uppermost part of the Lucas formation is 

limestone in an area immediately south of the head 

of Saginaw Bay, and in a few other restricted areas. 

These areas are apparently patches of rock which, 

like the Anderdon limestone of the outcrop area 

have never been dolomitized. Where the top of the 

Lucas is limestone the overlying Dundee is also 

limestone.

Calcium sulfate, occuring mostly as anhydrite, 

is present within a few feet of the top of the Lucas 

formation almost everywhere in the Michigan 

Basin. The outstanding exception is near the outcrop area in southeastern Michigan, especially in

Lenawee and Monroe Counties, where anhydrite 

is either absent or occurs in disseminated 

nodules instead of in sedimentary layers. In 

such areas the contact of the Dundee formation 

and Detroit River group is usually identifiable 

by the presence of sand, chert, or limestone 

in the basal part of the Dundee. Scattered 

grains of anhydrite were found among samples 

of the Dundee in a few sets of cuttings. These 

grains may be cavings from beds of anhydrite 

in younger formations, but also may be indigenous, the result of local saturation of the sea 

with calcium sulfate during Dundee time.

In most sections the contact of the Dundee 

formation and Detroit River group is marked 

by a change in color of the rocks. As a general 

rule the lowermost carbonate rocks of the 

Dundee are darker than the uppermost part of 

the Lucas strata, owing in part, but no entirely, 

to the lightening effect of the scattered anhydrite grains usually present in the drill cuttings 

of the Lucas. In few places the Dundee above 

the contact is lighter than underlying Detroit 

River. In southeastern Michigan this is due to 

the presence of scattered light-colored grains 

of chert or sand in the Dundee.

Insouluble residues have been used to determine the' contact of the Dundee formation and 

Detroit River group by Cooley (1947) and 

Saunders (1948) in and near the outcrop area, 

and by Wellman (1937) on well samples from 

the basin area. Wellman found that chert is the 

most abundant insoluble residue in the basal 

part of the Dundee formation and anhydrite the 

principal insoluble residue in the Detroit 

River group. Cooley and Saunders found relatively abundant sand grains in the basal part of 

the Dundee at the outcrop and in drill cuttings 

and one core from nearby wells. Clay and silt 

were the principal residues below the contact.

The carbonate rock in the Lucas formation is 

practically all dolomite except in the following 

three districts where an appreciable amount of 

limestone is also present; (l) southeastern * 

Michigan including most of Monroe County.and 

contiguous parts of Lenawee, Washtenaw, and 

Wayne Counties; (2) the "Thumb" and Saginaw 

Bay coastal area from St. Clair to losco 

County, with the northern end extending westward as far as southeastern Crawford County; 

and (3) the 9 tiers of townships at the northern 

end of the Southern Peninsula.

In most areas the carbonate rock interbedded 

with the evaporites in the Lucas formation is - 

light colored, but at places in the central part 

of the basin a dark-brown dolomite may occur 

in the lower part of the unit. In some wells 

this brown dolomite has been mistaken for the 

"Black Lime" in the underlying Amherstburg 

formation, leading to the abandonment of wells 

some distance above the top of the Richfield
Figure 4. Facies map of basal part of Dundee formation. In ruled areas, beds are dolomite; elsewhere they are limestone.

6
member which was supposed to have been tested.

The evaporites in the Lucas formation consist 

mainly of anhydrite and salt. Anhydrite is much 

more widely distributed, both vertically within the 

formation and laterally across the basin. The salt 

is confined to the upper half of the evaporite sequence and to the central part of the basin. Figure 

5, modified from Tharp (1944) shows the estimated 

aggregate thickness of salt beds of the Detroit 

River group. A comparison of this map with the 

thickness map for the entire Lucas formation (fig. 

6) shows that all of the salt lies within the 500 ft 

thickness line of the Lucas, the 200 ft thickness 

line of the salt is within the 750 ft thickness line 

of the Lucas, and most of the salt having an aggregate thickness exceeding 400 ft is confined to the 

deepest part of the basin in Missaukee and Roscommon Counties where the Lucas is more than 

1, 000 ft thick. There may be as many as 8 distinct salt beds, and the thickest bed may exceed 

100 ft in thickness. The writer has presented elsewhere the theory that these salt beds resulted from 

the leaching and reprecipitation of salt from Salina 

formation of late Silurian age salt. (1945, pp. 147- 

149).

Generally the anhydrite increases in abundance 

basinward. Not only is the anhydrite-bearing sequence of rocks thicker toward the center of the 

evaporite basin, but also the precentage of anhydrite in any one zone increases basinward. Anhydrite occurs (1) above the salt in the center of the 

basin, (2) inter stratified with the salt and (3) in 

greatest volume in the lower half of the evaporite 

sequence below the salt beds. The anhydrite occurs 

in many distinct layers, some of which attain considerable thickness. Outside the salt area anhydrite continues to be fairly abundant in the Lucas 

to points near the rim of the basin. The decrease 

in percentage of anhydrite is greatest on the north 

flank of the basin and toward the outcrop area on 

the southeast flank where beds of anhydrite are 

absent, but the mineral may still be present in 

scattered nodules.

The Richfield member is a new term applied to 

the porous dolomite at the base of the Lucas formation. The Richfield member is named after Richfield (now AuSable) Township in northern Roscommon County where oil was first found at this strati - 

graphic level. At the "type locality", the Richfield 

member is a porous dolomite and almost everywhere it is productive of oil. However, in the 

center of the Michigan Basin and on the west flank, 

the Richfield contains beds of sandstone. This sandstone has also been called the "Freer sandstone" 

after the Freer Well (well 53, cross section G-G 1 , 

fig. 3) in southwestern Clare County. The Richfield 

is a distinct lithologic unit beneath the anhydrite of 

the Lucas formation and is here given member 

status. A discussion of the "Richfield zone" oil 

and gas reservoir is included in the section on 

Economic Geology.

Cross sections D-D1 , E-E1 and G-G1 fig.3) 

show the sandstone of the Richfield member on 

the western flank of the Michigan Basin. According to the thickness map compiled by Enyert 

(1949) this sandstone extends from beneath Lake 

Michigan eastward across a belt.about three 

counties wide slightly beyond Roscommon 

County on the north and across Midland County 

on the south. It is more than 50 ft thick in a 

much narrower belt including parts of Mason, 

Lake, and Osceola Counties and extending into 

western Clare County. Beyond the limits of the 

sandstone itself, however, scattered sand 

grains commonly occur in the basal strata of 

the Lucas formation. Within the area of the 

sandstone its thickness is very erratic and it 

may be entirely absent locally. The Freer well, 

for example, penetrated more than 50 ft of 

sandstone in which gas and distillate were obt ained, but two of the four offset wells found 

no sand at equivalent depths. Enyert describes 

a similar sandless area in south central Clare 

County.

Amherstburg formation

The Amherstburg dolomite as defined by 

Ehlers (1950) includes the beds lying between 

the Sylvania sandstone and the Lucas dolomite. 

The Amherstburg is here redefined to include 

the Sylvania where present, as the basal sandstone member of the formation. The Filer 

sandstone lentil of the Amherstburg, as defined 

and described in this paper, occurs within the 

carbonate rock sequence of the formation and 

is confined for the most part to the western 

flank of the basin. Except for the Sylvania 

and Filer sandstone members the Amherstburg is a limestone or a dolomite. The only 

evaporites within the formation are occasional 

nodules of anhydrite observed in cores from 

wells drilled in the basin.

The beds assigned to Amherstburg formation in the central part of the basin agree with 

the fauna, stratigrapbic position, and lithologic character of the Amherstburg at its type 

locality. Cores have been obtained from wells 

in the basin that contain Amherstburg fossils. 

Most of the Fossils are in limestone layers, 

but some are in the Sylvania sandstone member. 

The noncherty limestone or dolomite beneath 

the evaporites and above the cherty Bois Blanc 

formation on the north flank of the Michigan 

Basin, and heretofore described by the writer 

(1945a) as upper part of the Bois Blanc, is now 

-considered to be Amherstburg.

The Amherstburg formation is a gray to 

brown dolomite at the outcrop in southeast 

Michigan and northwest Ohio. It has been 

studied in the rock cuts of the Living stone 

channel of the Detroit River west of the. town 

of Amherstburg on the Canadian shore, in the
M'£ijl5* i i ---N__i -___ ^ iFigure 5. Aggregate thickness of salt beds in the Lucas formation.

8
abandoned Cummins' quarry in southwestern Wayne 

County, Michigan, and in several of the quarries 

west and southwest of Sylvania, Ohio. The Sylvania 

sandstone member is exploited in a large quarry 

near Rockwood in southwestern Wayne County and ' 

is exposed in the floor of the Cummins' quarry and 

in several other abandoned quarries in southeastern Michigan and in the Sylvania district of Ohio. 

The Filer sandstone lentil is not exposed at the surface, but it might possibly crop out in places where 

it is covered by the water of Lake Michigan. Smaller 

exposures of lower part of the Detroit River group, 

probably belonging in the Amherstburg, occur near 

the northern tip of the Southern Peninsula and in 

some of the islands offshore in Lake Michigan 

(Ehlers, 1945).

The Amherstburg formation is present everywhere beneath the surface in the Southern Peninsula except in the southeastern and southwestern 

corners. Its absence in the southeastern corner is 

due to removal by erosion. It has been stripped off 

and the underlying Bass Island dolomite exposed in 

eastern and southern Monr'oe County. In southwestern Michigan its absence is due to erosion prior to 

the deposition of the Lucas formation which overlaps the Amherstburg. AH or parts of ten counties 

in the southwestern corner of the State are beyond 

the zero line on the thickness map of the Amherstburg. (fig. 7).

The greatest accumulation of Amherstburg formation is between southern Bay and southern Roscommon Counties where its thickness exceeds 600 ft in 

places. About half of this thickness is the Sylvania 

sandstone member at the base of the formation, 

which attains its maximum thickness in this area.

The top of the Amherstburg formation can be 

identified in the subsurface by its lithology. The 

light-colored, anhydrite-rich, mostly nonfossiliferous dolomites of the Lucas formation are succeeded downward by brown to black fossiliferous 

carbonate rocks which are limestone more often 

than dolomite. Furthermore the basal rocks of the 

Lucas tend to be sandy and the uppermost part of 

the Amherstburg is not. The studies of insoluble 

residues by Cooley (1947) and Saunders (1948) 

showed unsuspected amounts of sand at the strati - 

graphic position of the Richfield member of the 

Lucas in the outcrop and well samples in southeastern Michigan some distance from the area 

where the sandstone of the Richfield is present.

Except for local sandstones the Amherstburg 

formation is composed of limestone with local subordinate amounts of dolomite in the northern and 

eastern parts of the Southern Peninsula of Michigan. 

In the western and southern parts of the Southern 

Peninsula the Amherstburg is dolomite except in 

the southwestern corner where it is absent. The 

line separating the predominantly limestone facies 

from the dolomitic facie s of the Amherstburg (fig. 

8) starts at the south end of West Grand Traverse

Bay and extends southward to the Lake-Newaygo County line, thence eastward to the southeast corner of Osceola County, southeastward 

across Isabella County into northern Gratiot, 

eastward along the north edge of Township 

1 2 North to the northeast corner of Saginaw 

County, and southeastward to the International 

Boundary opposite downtown Detroit.

The outstanding characteristic of the carbonate rock in the Amherstburg formation is its 

relatively dark color. The Amherstburg at the 

outcrop is generally darker than the overlying 

Lucas formation. In wells north and northwest 

of the outcrop area much of the Amherstburg 

is dark-brown and even black a color change 

emphasized by the difference from the over1 ying light-colored evaporites of the Lucas. 

The Amherstburg has therefore been referred 

to by many geologists as the "Black Lime". 

The upper boundary of the "Black Lime" is 

readily recognized in cores and most drill 

cuttings, but in many sections the rock becomes 

lighter downward and a lower boundary cannot 

be fixed with certainty.

Because of gradually diminishing sand deposition the Sylvania sandstone member, where 

present-, grades upward into the carbonate 

rocks without a sharp break in most places, 

both below the surface and at the outcrop. It is 

therefore impossible to map accurately the 

thickness of the carbonate sequence above the 

Sylvania. A map based on approximate thicknesses shows that these rocks are thickest between Tuscola and Roscommon Counties where 

the carbonate rocks alone exceed 300 ft in 

thickness. A part of this area of maximum 

carbonate rock thickness lies northeast of the 

northeastern edge of Sylvania sand deposition. 

In.one area only, Hillsdale County in southern 

Michigan, the Sylvania sandstone member is 

not overlain by carbonate rocks of the Amherstburg. This relationship is shown in cross 

section C-C1 (fig. Ji well 25) where Lucas 

formation rests directly on the Sylvania sandstone member of the Amherstburg.

The Filer sandstone lentil of the Amherstburg formation has been described in some detail by Enyert (1949). The type section for this 

member, which does not crop out, is the 

Ruggles and Rademacher well 24, sec. 12, T. 

21 N. , R. 17 W. , Filer Township, Manistee 

County. The Filer sandstone lentil lies within 

the carbonate rock sequence below the Lucas 

formation and above the Sylvania sandstone 

member of Amherstburg. It is largely confined 

to a belt crossing the basin from Saginaw Bay 

to Lake Michigan. According to the thickness 

map compiled by Enyert, the area of the Filer 

sandstone lentil includes most or all of Bay, 

Ogemaw, Midland, Gladwin, Isabella, Clare, 

Mecosta, Osceola, Lake, Mason, Manistee,
i ---K t

CASS ST.JSSEPH ! BRANCH ! HILLSDALE LEMA*EE

! i ! i

/ MICHI6AN j o I |

mfl I - " » i * I "«^< I

| INDIANA j ; MICHIGAN '_________ ...

! ! IOHIO

Figure 6. Thickness map of Lucas formation. 

10
-_... \__.J, ;

I \0 ! »"5HI ?*.N_J___ 

Figure 7. Thickness map of Amherstburg formation (including Sylvania sandstone member).

11
and Benzie Counties. It exceeds 50 ft in thickness 

in Bay and western Manistee Counties. According 

to R. A. Newcombe (verbal communication, July 

27, 1950) recent wells in western Michigan have 

penetrated as much as 100 ft of Filer sandstone. 

The position of this sandstone within the Amherstburg is shown in cross sections A-A1 , D-D', and 

E-E1 (See fir. 3). The stray sandstone above 

the Sylvania in the Amherstburg penetrated by a 

well near the northeast corner of Washtenaw 

County (well 19, cross section B-B 1 ) may also be 

of Filer age.

The Sylvania sandstone member of the Amherstburg formation has been described by Grabau and 

Sherzer (1910), Carman (1936), and Enyert (1949). 

Enyert studied both outcrop and subsurface sections; the others confined their investigations to 

the outcrop. The Sylvania sandstone is redefined 

in this paper as a member of the Amherstburg 

formation because of the upward gradation of the 

sandstone into the overlying carbonate rock. This 

absence of a sharp contact can be observed in 

both quarry exposures and in well samples. 

Carman (1936) called attention to the upward gradation of the Sylvania in 1936.

The accompanying thickness map (fig. 9) shows 

that the Sylvania sandstone member is limited 

in its distribution in the subsurface rocks in 

Michigan to a belt extending from Macomb-WayneMonroe-Lenawee-Hillsdale Counties in southeastern Michigan north and northwest to a probable 

terminus in Crawford-Kalkaska-Wexford-Lake 

Counties. An earlier map published by the writer 

(1945a) showed the Sylvania continuing westward 

beneath Lake Michigan, but this was based in part 

upon not recognizing the Filer sandstone lentil as 

a separate member and in part upon the interpretation of "Sylvania" in the driller's log of a well 

in western Manistee County (Rogers well 1, sec. 

34, T. 23 N. , R. 16 W) as indicating the presence 

of sand about 140 ft below the Filer. The presence 

of sand at that stratigraphic position has been 

questioned by Lindsay (oral communication), and 

until positive evidence of the presence of Sylvania 

sandstone member in western Michigan is obtained, 

the western boundary of the Sylvania is terminated 

as shown in figure 9. The Sylvania sandstone 

member thins westward from a maximum thickness 

of more than 300 ft in eastern Clare County. South 

of Saginaw Bay and in eastern Livingston and 

southeastern Washtenaw County the Sylvania exceeds 300 ft in thickness in three other areas. 

The variations in sandstone thickness, and the relationship between the Sylvania and the overlying 

rocks of the Amherstburg and the underlying Bois 

Blanc or Bass Island formations are shown in the 

accompanying cross sections (See fig. 3). The 

Sylvania member appears in all cross sections 

except E-E' which extends along the western side 

of the Southern Peninsula. In some areas the 

Sylvania is entirely sandstone, but in other places, 

including the Rockwood quarry, the sandstone sequence is broken by one or more beds of carbonate 

rock which may or may not be cherty.

The Detroit River group is underlain by 

either Bois Blanc or Bass Island formations. 

The pre-Detroit River areal geologic map is 

shown in figure 10. Wells in all parts of the 

Southern Peninsula except those on the southwest flank of the basin, where the strata rise 

toward the axis of the Kankakee arch, penetrated Bois Blanc beds below the Detroit 

River group. In southwestern Michigan the 

Bois Blanc was eroded from the arch and 

Detroit River group directly overlie the Bass 

Island dolomite which underlie the Bois Blanc 

farther north. This relationship is shown in 

cross sections A-A', C-C', D-D', and E-E' 

(See fig. 3).

To date Garden Island formation, which is 

at the base of the Devonian sequence of rocks 

underlying Bois Blanc dolomite and overlying 

the Bass Island and Salina formations of Silurian age, has been identified definitely in 

in the samples only from one well, the Sun 

Oil Company's State -Mane elona A-l in sec. 

36, T. 29 N. , R. 5 W. , in the southeastern 

corner of Antrim County. The core from 

this well contained, at depths of 4,409 to 

4,411 ft unmistakable specimens of the brachiopods Rensselaria e Ion gat a (Conrad), and 

Costispirifer arenosus (Conrad), typical guide 

foss,ils of the Oriskany sandstone. These fossils are also abundant at the type locality on 

Garden Island in the Beaver Island group, 

Charlevoix County, Lake Michigan (Ehlers, 

1945, pp. 73-80). The Garden Island formation is characteristically a dolomite which may 

be very sandy in places. Its patchy distribution 

in Michigan is similar to the occurrence of 

the Oriskany sandstone in southwestern Ontario. 

Over wide areas in Ontario post-Oriskany 

erosion has removed all of the Oriskany sandstone except for the grains of sand that had 

spilled into joint cracks in the underlying 

rock. It is suggested that the erratic distribution of the Garden Island formation is 

likewise due to erosion rather than nondeposition.

The Amherstburg formation was likewise 

eroded on the northeast flank of the Kankakee arch, but this truncation took place 

during the erosion interval following the 

deposition of the Amherstburg rocks. As 

a result Lucas formation directly overlies 

Bass Island dolomite in* southwestern 

Michigan, beyond the zero thickness line 

of the Amherstburg (fig. 7).

Because of the erosional unconformity-beneath the Detroit River group the underlying 

strata may differ both in age and lithology 

from one area-to another, and even from well 

to well. This is especially noticeable where 

the Bass Island dolomite is beneath the Detroit River strata because of marked lithological differences in the Bass Island at dif12
A

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Figure 8. Lime stone/dolomite facies map of Amherstburg formation.

13
ferent stratigraphic levels. Wells in western and 

southwestern Michigan may penetrate pale yellowish dolomite, gray dolomite, bluish, highly argillaceous dolomite, or light green shale immediately 

below Detroit River rocks. The green shale was 

formerly considered by the writer to be "Sylvania 

equivalent" (1945a), but the Sherk well 1, sec. 21, 

T. 5 N. , R. 10 W. , Kent County, drilled through 

a shale that is apparently the same shale beneath 

Bois Blanc formation. This green shale is probably Bass Island in age, but it may have been deposited during Garden Island (Oriskany) time.

STRUCTURAL GEOLOGY

The regional structure of the Michigan Basin 

has been discussed by Newcombe (1933), Pirtle 

(1932), Smith (1937), and Lockett (1947). Figure 

11 shows the structure of the Southern Peninsula 

of Michigan contoured with an interval of 500 ft 

on the base of the Lucas formation. The most 

obvious structural feature is, of course, the 

Michigan Basin, but at this stratigraphic level 

the structural relief is only about 1 mile in 150 

miles. Lockett (1947) points out that a baseball 

diamond, with a pitcher's mound eight inches 

high, has approximately the relative relief of the 

Michigan Basin.

Within the basin the major structural feature 

is the Howell anticline, a northwestward plunging fold on the southeast flank of the basin that 

is shown by well 17, cross section B-B1 . The 

West Branch anticline in Ogemaw County, another 

large structure, is unusually well indicated by 

the contours on the base of the Lucas formation.

The presence of thick and relatively unyielding 

bodies of Sylvania sandstone member at the base 

of the Amherstburg formation resulted in some 

arching of the overlying strata due to differential 

compaction. Examples can be seen in cross sections A-A 1 , D-D1 , and G-G1 .

Local structures in Michigan ordinarily are not 

discernible on a structure map of the basin contoured with an interval of 500 ft, but on figure 11 

the -4, 000 ft contour does disclose a domed area 

in northwestern Clare County. The wide spacing 

between the -3, 000 and the -3, 500 ft contours in 

southwestern Crawford County also denotes a 

local area of uplift.

In and near the belt of outcrop of the Detroit 

River group the rocks have subsided into collapse 

structures after leaching of the deeper salt of the 

Salina formation, especially during the erosion 

interval prior to the deposition of the Dundee formation. These features are described in detail in 

a former report (1945c, pp. 121-154).

GEOLOGIC HISTORY

The area that is now the Southern Peninsula of 

Michigan had at least two distinct inundations and

one downwarping of considerable magnitude during Detroit River time. However, the pertinent 

history of the Detroit River group begins with 

Bass Island time. When the Bass Island sea withdrew, the area was covered with the youngest 

sedimentary rocks of the Bass Island dolomite. 

These late Silurian deposits were wide-spread. 

The.Michigan Basin was not a topographic feature at this stage and the late Silurian sediments 

were deposited in a large area beyond the limits 

of the present structural basin. During the period 

of emergence prior to the encroachment of the 

earliest Devonian sea there was some erosion 

that removed the uppermost sediments of the 

Bass Island either completely or in part. By 

the time the earliest Devonian sea spread over 

the area that is now the Southern Peninsula of 

Michigan the topography was moderately rolling 

and rocks of different ages were exposed from 

place to place. The earliest Devonian sea was 

in Oriskany time, and in it the Garden Island 

formation was deposited. Emergence uplift 

followed and erosion removed the Garden Island 

formation everywhere in Michigan except for 

patches on Garden Island and elsewhere on the 

northern flank of the basin. In other areas, 

especially farther east in eastern Ohio and in 

Pennsylvania and New York, considerably more 

Oriskany sandstone was preserved. The postOriskany emergence and erosion interval was 

followed by widespread inundation by the Onondaga sea. In Michigan the Bois Blanc formation 

was deposited on the floor of this sea, covering 

both the remnants of the Garden Island formation 

and the twice-eroded Bass Island formation. 

Minor downwarping of the Michigan Basin took 

place at this time, resulting in preservation of 

a thicker Bois Blanc sequence north of Saginaw 

Bay. The withdrawal of the Onondaga sea from 

this area was followed by erosion of such magnitude that the Bois Blanc formation was completely removed from the flanks of the Kankakee 

and Findlay arches.

The areal geology at the time of the inundation 

by the earliest of the Detroit River sea (Amherstburg time) is shown in the pre-Detroit River 

geologic map (fig. 10). The feather edge of Bois 

Blanc formation varied widely in position from 

place to place owing to local differences in the 

depth of erosion. A downwarp along a northwestsoutheast axis from central Michigan across 

southeastern Michigan into northern Ohio permitted the entrance of marine waters which marked 

the beginning of Amherstburg time. The Sylvania 

sandstone member of the Amherstburg formation 

was deposited in this shallow trough in central 

and southeastern Michigan. It is postulated that 

wind-transported sand, probably from the area 

of outcrop of Cambrian sandstones and preCambrian quartzose rocks in Wisconsin, after 

drifting across the intervening emergent area, 

was blown into the early Amherstburg sea and 

thus preserved. No doubt surface weathering in 

the nearby emergent area contributed clastic

14
CHARLEVOiX I 

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Figure 9. Thickness of Sylvania sandstone member of Atnherstburg formation.

13
grains of carbonate rock and chert to the eastward 

drifting quartz sands. Carbonate rock and chert 

were also deposited in the Sylvania sea (l) during 

intervals of nonsupply of quartz sand, and (2) on 

the leeward (eastern) side of the seaway beyond 

the area of sand deposition. Therefore the rocks 

of the Sylvania sandstone member of the Amherstburg contain some carbonate rock and chert as 

well as sand, and along the eastern edge of the 

Sylvania are some calcareous sediments of Sylvania 

age. The latter tends to be more siliceous than 

the younger Amherstburg strata, but are otherwise 

indistinguishable. The thickness map of the Sylvania (fig. 9) is confined to the sandstone phase.

An eolian origin of the Sylvania sandstone member of the Amherstburg formation was postulated 

by Sherzer and Grabau (1909), and Carman (1936) 

suggested a reworking of eolian sands by marine 

waters. But with these exceptions the tendency 

heretofore has been to consider the sand of the 

Sylvania as having accumulated by current action 

like modern beach and barrier sands, or like the 

famous oil-bearing "shoestring" sands of Kansas 

and Oklahoma. But there are several strong arguments against this type of origin for the sand of 

the Sylvania. One is the size of the deposit of 

Sylvania. It exceeds 300 ft in thickness and is 

from 50 to 75 miles wide, whereas beach or barrier sands, such as the Bartlesville or Burbank 

sands that were deposited in the Cherokee (Pennsylvanian) sea of the mid-continent, rarely reach 

two miles in width. Another argument is the isolation of the sand of the Sylvania from possible 

sources of supply. Perhaps the strongest evidence 

opposing ocean current deposition is the lack of 

any finer elastics (mud or clay) which invariably 

are associated with current-transported sands.

The evidence against the transportation of the 

sand of the Sylvania sandstone member of the 

Amherstburg formation by waters also to a considerable extent supports the theory of wind transportation. Comparable volumes of sand are winnowed clean and transported hundreds of miles 

by prevailing winds in areas of scant vegetation 

today. The Great Sand Dunes National Monument 

eastern San Luis Valley in Colorado contains 

enormous accumulations of clean sand carried 

from many miles to the west and dropped where 

the winds are slowed by the Sangre de Cristo 

Mountains which form the valley wall to the east. 

If there were a lake or sea covering eastern San 

Luis Valley the marching sands would have been 

trapped somewhat in the manner suggested for 

the Sylvania.

Detroit River time precede that of the earliest 

known forests and the land was probably almost 

completely bare of vegetation, so the prevailing 

westerlies could pick up the abundant quartz sand 

released from the weathering of the Cambrian 

and Lower Ordovician sandstones that cropped 

out in eastern Wisconsin and from decomposing 

and disintegrating pre-Cambrian granites still

farther west, and transport the grains eastward until they sank into the waters of the 

early Amherstburg (Sylvania) sea.

Later in Amherstburg time the sea spread 

more widely and eventually covered all the 

area of the Southern Peninsula as well as adjacent areas. Carbonate rocks were the main 

deposits in the expanded seaway, but during 

the earliest phases sand present on the submerging surface was mixed with the carbonate 

deposits so that a sandy limestone or dolomite 

was formed. The water was probably not very 

deep at any place, and brief emergences may 

have taken place which permitted the eastward 

movement of wind driven sands (Filer) from 

the outcrop area of the older sandstones in 

Wisconsin. A relatively moderate amount of 

sagging took place in the Michigan Basin during the later part of Amherstburg time and 

more than 300 ft of carbonate rock accumulated 

after deposition of the Sylvania sandstone member. The deepest part of the basin during this 

interval was in the area that is between southeastern Roscommon and east central Tuscola 

Counties, which is parallel to, but northeast of, 

the axis of the Sylvania down warp in central 

Michigan. Throughout most of Amherstburg 

time after deposition of the Sylvania the concentration of calcium sulfate in the sea water 

was close to the saturation point and small 

amounts of anhydrite were precipitated from 

time to time.

Amherstburg deposition closed with complete 

emergence of the area. Not only did the sea 

withdraw, but the area was elevated sufficiently 

for active erosion to take place. The Amherstburg sediments were removed from the Kankakee 

arch by erosion, but the erosion was of less 

magnitude than that which had previously re - 

moved the Bois Blanc formation from the same 

area. The zero thickness line of the Amherstburg in figure 7 shows the extent of erosion 

basinward. In south-central Michigan (Hillsdale 

County) the carbonate rocks were entirely 

removed and the underlying Sylvania sandstone 

member exposed.

During this period of emergence sand dunes 

again progressed eastward across the land surface into what is now western and central 

Michigan. With the submergence of the land 

beneath the Lucas sea these bodies of sand, 

some of them completely isolated, were trapped 

and became sandstone lenses in the Richfield 

member of the Lucas. One of these isolated 

dunes is in southwestern Clare County, where 

the "Freer sand" lens is more than 50 ft thick 

in one well and absent in two offset wells. The 

earliest Lucas sea was widespread, extending 

beyond the present limits of the Michigan Basin, 

especially across the axis of the Findlay arch 

into northern and northeastern Ohio. During this 

time the Lucas and Anderdon formations of the

16
 Boundary of Bolt 

A Blanc formation

~T

OTSE60 MOMTMOHENCrJ ALfelw

 f j - - ( -j 

m®--.

j MICHIGAN )_______ _.

I "OHIO !

Figure 10. Boundary of the Bois Blanc formation in southwestern Michigan. South of this line the 

Detroit River group is directly on rocks of Bass Island age.

17
V~._,tl. s-U- !

!MICHIGAN I O - >- L * » i -A I ^

\ 1 I MICHI6AN ! ^ 

, i i ,« n^

Figure 11. Structure contour map of Southern Peninsula of Michigan contoured on base of Lucas

formation.

18
present Ohio-Michigan outcrop area were deposited. 

Far out from shore, and away from the freshening 

effect of entering streams, the waters were saturated with calcium sulfate and layers of anhydrite 

were periodically precipitated. The first major 

downwarp of the Michigan basin since the evaporite 

deposition of the Salina formation followed the deposition of the earliest Lucas sediments and the 

connection with open water across the Findlay 

arch was destroyed by emergence. Within the 

land-locked Lucas sea which covered the Michigan 

Basin the continued evaporation resulted in the 

precipitation of large quantities of anhydrite. When 

the sea had shrunk until it covered only a part of 

the northern half of the Southern Peninsula, salt 

precipitation began and continued intermittently 

until more than 400 ft of salt was deposited. The 

source of this salt was probably the salt measures 

of the Salina formation which were being leached 

at this time by waters percolating through the outcropping layers higher on the flanks of the basin. 

Studies made by the writer (1945c) in the Mackinac 

Straits area have shown that an enormous quantity 

of salt was leached from the Salina exposed along 

the north rim of the basin during Middle Devonian 

time. Before deposition of the Dundee formation, 

collapse into salt caves of the Salina took place 

on a regional scale. The leaching of salt at this 

time was probably much more extensive than just 

along the north rim; collapse features at the south 

side of the Michigan Basin indicate solution activity there also. The probable presence of an outer 

topographic rim, made by the same resistant limestone of the Niagara group that form the Niagara 

escarpment today, gives some further support to 

the theory that the great volume of salt leached 

from the Salina during the middle Devonian time 

was washed into the desiccating late Lucas sea 

where it was precipitated when this land-locked 

body of water had shrunk until it occupied only 

the deepest part of the basin.

The downwarping during later Lucas time continued until a total of more than 1, 000 ft of carbonate rock, anhydrite, and salt had been deposited 

in the center of the basin. Meanwhile, according 

to the Ehler's hypothesis, with the emergence of 

Findlay arch, sediments of Columbus age were 

deposited on top of the older Lucas sediments 

southeast of the arch. No definite break has been 

found at the outcrop in northern Ohio between 

Detroit River and Columbus strata, and it is probable that sea did not withdraw but was made 

more shallow by the emergence of the Findlay 

arch. The Columbus sea probably did not extend 

into the Michigan Basin where the late Lucas sea 

was desiccating. If this theory is correct, the 

Columbus limestone is the equivalent in time of 

the younger evaporites, including the salt, in 

upper part of the Lucas of the central part of the 

Michigan Basin.

Paul Weaver, Gulf Oil Corp. , Huston, Texas, 

in an address at the University of Michigan, Jan. 

14, 1949, pointed out the much higher rate of deposition of carbonate rock. Consequently a 

thick evaporite section could be accumulating 

while a very much thinner limestone succession was being deposited elsewhere.

An alternative possible explanation for salt 

deposition in Lucas time is that the Columbus 

sea-did spill across the Findlay arch occasionally, thereby adding more salt to the evaporating waters occupying the Michigan Basin. This 

explanation, which is the bar theory of salt, 

concentration, is applied rather generally to 

explain the salt beds deposited earlier in Salina 

time in the Michigan Basin on a much greater 

scale.

Before the close of Lucas time the waters 

freshened somewhat, possibly due to increased 

rainfall, salt precipitation ceased, and anhydrite deposition decreased. At the same time 

carbonate rock deposition increased in relative abundance. The basin was filled with sediment, losing its identity as a topographic feature. The Lucas and Columbus seas withdrew 

and an interval of emergence and erosion 

followed. Some sand was carried out over the 

emergent lands, especially in Ontario and 

eastern Michigan. The distribution of this 

sand strongly suggests a source in Ontario 

rather than in Wisconsin. Submergence by the 

Dundee and Delaware sea followed, and the 

sands became incorporated in the basal parts 

of Dundee and Delaware strata. This sea was 

widespread, covering a considerable area 

beyond the boundaries of the Michigan Basin. 

Dundee and Delaware deposition was followed 

by the deposition of the Rogers City formation. 

Emergence followed the deposition of Dundee 

and Rogers City strata and subsequent erosion 

stripped these rocks from the southwestern 

corner of Michigan and again exposed Detroit 

River group at the surface. The truncated 

layers of the formations of the Detroit River 

were later covered by deposits of the Traverse 

sea. Additional downwarpings of the basin, 

which were minor in intensity as compared 

with that of Lucas time, have further increased 

the basin structure. Folding continued intej-- 

mittently throughout the sedimentary history 

of the basin but reached a climax during the 

pre-Pennsylvanian emergence. Pre-glacial 

erosion exposed the circular band of outcrop 

of the Detroit River group between the center 

and the periphery of the Michigan Basin, but 

glacial and post-glacial deposits, and the waters 

of the Great Lakes, have masked most of these 

exposures except for a few in southeastern 

Michigan, northern Ohio, and southwestern 

Ontario.

ECONOMIC GEOLOGY

Oil and ^as (Grant and Eddy, 1949; Cohee 

and Martin, 1948). Reservoirs in rocks of the 

Detroit River group have yielded about one19
Field producing oil from Detroit River 

group and reservoirs in younger rocks

I _____._L

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I S r- rFigure 12. Oil producing fields. 

20
eighth of the total production of oil and gas in 

Michigan to date. As no appreciable amount of oil 

was produced from the Detroit River before the 

year 1940, when the Reed City field was discovered,, 

the yield in recent years has been considerable and 

has called attention to future oil prospects in 

Detroit River strata.

All the oil and gas so far produced commercially 

from Detroit River group has come from the Lucas 

formation and mostly from dolomites within that 

formation. The Sylvania sandstone member of the 

Amherstburg formation has yielded good "showings" 

of oil in several wells (Landes, 1945a) but no production as yet. Oil found in sandstone' in Mason 

County originally believed to have been from the 

Sylvania sandstone member, is actually from the 

sandstone of the Richfield member of the Lucas 

according to Enyert (1949). The Filer sandstone 

lentil, and the limestones and dolomites of the 

Amherstburg, so far have been found barren of 

oil or gas in commercial volume.

The reservoirs within the Lucas formation discovered to date are either near the top or near 

the bottom of the formation. The upper reservoirs 

lie in the "Reed City zone", so-called because it 

is the source of oil from the Detroit River group 

in the Reed City field in Osceola County. The 

lower zone is named the "Richfield, " after the 

Richfield pool in Roscommon County. All of the 

"Reed City zone" production comes from dolomite 

layers lying within the uppermost 100 ft of the 

evaporite unit, and the largest yields come from 

rocks from 20 to 50 ft below the base of the Dundee 

formation. Some Michigan petroleum geologists 

include the "Reed City zone" in the lower part of 

the Dundee.

The "Richfield zone" occupies the lowest part 

of the Lucas formation. In the fields with important production from this zone the reservoirs are 

porous dolomite layers scattered through a section 

nearly 100 ft thick between the lowest thick anhydrite bed and the top of the Amherstburg formation. 

Interconnecting fractures may be the reason for 

much of the porosity of the dolomite of the Richfield member. Leading fields (fig. 12) are the 

Beaver Creek, East Norwich, Enterprise, and 

Richfield. Others include the Winterfield, Rose 

City, Fork, and Cedar fields. Minor production 

has been obtained from sandstones in the Richfield 

member in the Freer pool of Clare County and 

the Logan field of Mason County. In the small 

Akron field in northwestern Tuscola County the 

producing zone is a series of porous dolomite 

beds lying, in part at least, above the lowest 

anhydrite bed in the Lucas formation. The oil 

occurrences in the Atlanta area of Montmorency 

County are also in dolomite interbedded with 

anhydrite. Lindberg (oral communication) believes that Tuscola-Montmorency reservoirs are 

above and distinct from the "Richfield zone. "

In exploring for oil in the basal part of the Lucas

formation it has been the custom to drill until 

either oil was found or the "Black Lime" of the 

underlying Amherstburg formation was penetrated. Unfortunately the presence of "false" 

black limestone beds in the Lucas above the 

Richfield member has led to the abandonment 

of several wells in Roscommon and Tuscola 

Counties before the possible producing beds 

were penetrated.

The oil fields so far discovered in the Detroit 

River group are anticlinal accumulations. The 

dolomite zone of the Richfield member of the 

Lucas formation appears to have greater lateral continuity of porosity than the sandstone 

of the Richfield member The latter may consist of a series of discontinuous lenses, each 

one of relatively small size. The same is probably true of the Filer sandstone lentil of the 

Amherstburg formation. The lenses of the 

Sylvania sandstone member of the Amherstburg 

are more extensive, but are very likely also 

discontinuous. Exploration of this zone to date 

has been disappointing. However, most wells 

penetrating the Sylvania sandstone member in 

the central part of the basin have been offstructure.

It is reasonable to assume that many new 

fields in the Detroit River group will be discovered by exploring the Detroit River sequence 

of rock from top to bottom on anticlines. Strati - 

graphic traps, due to porosity pinch out in the 

dolomite zones, and also due to sand lenticularity.are additional possibilities.

Salt. --Salt in the Detroit River group has 

been exploited by the brine well method in 

Manistee County since 1881 and in Mason County 

since 1886. These salt producing areas are 

close to the western edge of the salt deposit 

of the Detroit River (fig. 5) In these areas the 

salt is thinnest, but it is also closest to the 

surface and is adjacent to water transportation. 

No attempt has been made to mine salt of the 

Detroit River. In the center of the deposit the 

aggregate thickness exceeds 400 ft. The reserve, 

although small in comparison with that of the 

deeper salt in the Salina formation, is enormous 

in terms of annual world production.

REFERENCES CITED

Carman, J. E., 1936, Sylvania sandstone of

northwestern Ohio: Geol. Soc. America Bull., 

voL 47, pp. 253-265.

Cohee, G. V. , and Martin, H. M. , 1948, A 

summary of the stratigraphy of the Southern 

Peninsula of Michigan: Michigan Geol. Soc. 

Rept. , pp. 7-8.

Cohee, G. V., and Underwood, L. B. , 1945,

Lithology and thickness of the Dundee formation 

and the Rogers City limestone in the Michigan 

Basin: U.S. Geol. Survey Oil and Gas Investigations Preliminary Map 38.

21
Coolly, G. A. , 1947, Insoluble residues of Detroit 

River and Dundee formations: (Univ. Michigan, 

unpublished thesis).

Cooper, G. A. , and others, 1942, Correlation of 

the Devonian sedimentary formations in North 

America: Geol. Soc. America Bull. , vol. 53, 

p. 1754.

Ehlers, G. M. , 1945, Geology of the Mackinaw 

Straits region: Michigan Geol. Survey Pub. 44, 

pp. 111-116.

...... 1950, Revised classification of the Middle

Devonian Detroit River group [abstract]; Geol. 

Soc. America Bull. , vol. 61, no. 12, pt. 2, 

pp. 1455-1456.

Enyert, R. L. , 1949. Middle Devonian sandstones 

of the Michigan Basin: (Univ. Michigan, unpublished doctoral thesis; to appear in Am. Assoc. 

Petroleum Geologists Bull.).

Grabau, A. W. , and Sherzer, W. H., 1910, The 

Monroe formation of southern Michigan and 

adjoining regions: Michigan Geol. Survey Pub. 

2.

Grant, R. P., and Eddy, G. E. , 1949, Prospects 

for and results of drilling beyond proven areas 

and to deeper zones in the Michigan Basin: Oil 

and Gas News, vol. 30, June 17.

Landes, K. K. , 1945a, Geology and oil and gas 

possibilities of Sylvania and Bois Blanc formations in Michigan: U. S. Geol. Survey Preliminary Map 28.

----.. 1945b, The Salina and Bass Island rocks 

of the Michigan Basin: U.S. Geol. Survey Preliminary Map 40.

------ 1945c, Geology of the Mackinaw Straits

region and subsurface geology of the northern 

Southern Peninsula: Michigan Geol. Survey 

Pub. 44.

Lane, A. C. , Prosser, C. R., Sherzer, W. H., 

and Grabau, A. W., 1909, Nomenclature and 

subdivision of the upper Siluric strata of 

Michigan, Ohio, and western New York: 

Geol. Soc. America Bull., vol. 19, pp. 553- 

566.

Lockett, J. R. , 1947, Development of structures 

in basin areas in northeastern United States, 

Am. Assoc. Petroleum Geologists'Bull., vol. 

31, pp. 429-446.

Newcombe, R.B., 1933, Oil and gas fields of 

Michigan: Michigan Geol. Survey Pub. 38

...... 1929 C1930J, Interpretation of recent

discoveries in the salt-bearing rocks of 

Michigan: Michigan Acad. Sci. , Arts, and 

Letters, vol. 12, pp. 239-250.

Pirtle, G. W. , 1932, Michigan structural basin 

and its relationship to surrounding areas: 

Am. Assoc. Petroleum Geologists Bull., vol. 

16, pp. 145-152.

Saunders, J. M. , 1948, Lithology and insoluble 

residues of a core from the Detroit River 

group: (Univ. Michigan, unpublished thesis).

Sherzer, W. H., and Grabau, A. W. , 1909, The 

Sylvania sandstone, its distribution, nature 

and origin: Michigan Geol. Survey Pub. 2, 

chapter 3, pp. 61-86.

Smith, R.A., 1937, 1938, Some new aspects of 

the Michigan Basin [abstract] : Proc. Geol. 

Soc. -America, p. 326.

Tharp, .Marie, 1944, Subsurface studies of the 

Detroit River series: (Univ. Michigan, unpublished thesis).

Wellman, D. D. , 1937, Insoluble residues of 

Dundee and Detroit River (Upper Monroe) 

formations of Central Michigan: Am. Assoc. 

Petroleum Geologists Bull. vol. 21, pp. 317- 

332.

WELLS USED IN CROSS SECTIONS

No. in 

sections

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

County

Berrien

Berrien

Van Buren

Kalamazoo

Barry

Gratiot

Midland

Ogemaw

Oscoda

Alpena

Alpena

Presque Isle

Antrim

Antrim

Clare

Midland

Livingston

Livingston

Washtenaw

Wayne

Company, farm, and number

A. Violette-C. K. Warren no. 1

Bloomingdale Development Co. -W. Tabor no. 1

Daily Crude Oil Co. -Leo Wise no. 1

Reid and Mackey - Norris and Smith,

B. Caldwell no. 1

Sun Oil Co. -Bernice Wilcox no. 1

Michigan Chemical Co. no. 13

Dow Chemical Co. -Fee no. 13

Pure Oil Co. -W. T. Yeo no. 1

Ohio Oil Co. -Mio Unit Area no. 1

Sohio Petroleum Co. -Turtle Lake Club no. 1

Charles W. Teater-Nevins no. 1

Alpena Land Co. -Grand Lake no. 1

Ohio Oil Co. -H. Chamberlain no. 1

Sun Oil Co. -State -Mane elona no. A-l

Pure Oil Co. -D. B. Thompson no. 1

Dow Chemical Co. no 11

Panhandle Eastern Pipe Line Co. , Addison no. 1

Panhandle Eastern Pipe Line Co. , G. Bauer no. 1

H.L. Heath-Merrit, Wilson, and Buers no. 1

Drake Bros. -L. Truesdell no. 1

Location

Section

8

33

26

32

5

24

19

2

30

9

18

8

14

36

3

20

11

25

1

25

Township

8S

5S

3S

IS

3N

12N

14N

21N

25N

29N

32N

33N

31N

29N

20N

14N

3N

2N

IS

2S

Range

20W

17W

13W

12W

9W

3W

2E

2E

3E

5E

6E

8E

8W

5W

3W

2E

3E

5E

7E

8E

ES
No. in 

sections

21

22

23

24

25

26

27

28

29

30

31

32

33

34

35

36

37

38

39

40

41

42

43

44

45

46

47

48

49

50

51

52

53

54

55

56

County

Wayne

Berrien

Van Buren

St. Joseph

Hillsdale

Lena wee

Washtenaw

Wayne

Oceana

Oceana

Mecosta

Midland

Bay

Tuscola

Huron

Cass

Van Buren

Muskegon

Oceana

Mason

Leelenau

Leelenau

Leelenau

Monroe

Wayne

Macomb

St. Clair

Huron

losco

Manistee

Lake

Osceola

Clare

Clare

Arenac

Huron

Company, farm, and number

F.C. .Cheers-W.E. Ellis

J. Warmen-Fee no. 1

Wolverine Oil and Exploration Syndicate,

Vought no. 3

O. A. Avery-S. Dunworth no. 1

Jacob Beck-Fee no. 2

Voorhees Drilling Co. , and others, Irving

Grove no. 1

Alfred Violette -Sander son no. 1

Solvay Process Co. -Well no. 36

Neil Wagenaar-J. and M. Kyncl no. 1

Pennsylvania Oil and Gas Co. , Bert Snow no. 1

Gulf Refining Co. -Mary Gale no. 1

Dow Chemical Co. -Fee no. M-2

Gallaher and Bachelder, William Bate son no. ?

Shell Oil Co. , Inc. -E.F. Hutchinson no. 1

Pacific Exploration Co. -Ballagh no. 1

C.A. Daniels -Charles Clute no. 1

Harris Oil Co. -Locker no. 1

Johnson Oil Refining Co. -Kate Sovacool no. 1

Carter Oil Co. -O. P. Neumann no. 1

Charles W. Teater-George Piper no. 1

Lupher Drilling Co. , and others, Wilce Farm

and Orchard Co. no. 1

Fred M. Copeland and P.M. .Barton, L.

Overby no. 1

D-O-H-I- Oil Corporation-Farrow no. 1

Joe Duffey-Putnam and Russell Estate no. 1

Schrier and Kerr-H. R. Ford Well

H.H. Brown-Krantz no. 1 (Private Claim 193)

Mueller Brass Co. -Wm. Van Antwerp no. 1

Pure Oil Co. -Joseph Stapleton no. 1

Ray W. Matlock-John C. Johnson no. 1

Ruggels and Rade maker Well no. 24

Ohio Oil Co. -Guy Fairbanks no. 1

Ohio Oil Co. -P. N. Stedman no. 3

Pure Oil Co. -Jennie Freer no. 1

Gulf Refining Co. -John Oman no. 1

Ervin Major -Archie McTaggart no. 1

Charles W. Teater -Thomas Polega no. 1

Location

Section

35

34

32

13

15

8

26

26?

35

23

3

27

2

21

32

2

13

2

21

18

34

5

13

5

22

9

22

1

12

11

29

18

8

26

27

Township

4S

3S

4S

6S

6S

5S

4S .

2S

16N

15N

14N

14N

14N

14N

15N

7S

IS

ION

14N

17N

28N

29N

8S

6S

2S

3N

6N

17N

22N

21N

20N

18N

17N

17N

19N

18N

Range

10E

17W

14W

11W

3W

4E

7E

HE

18W

15W

8W

2E

4E

10E

12E

13W

15W

17W

18W

17W

14W

12W

5E

7E

10E

14E

17E

15E

8E

17W

14W

10W

6W

4W

3E

13E

IHT.-DUP. SEC., WASH., D.C. ;