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1985 Middle and Late Wisconsinan (Pleistocene) insect assemblages from Illinois Kristine D. Carter University of North Dakota
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INSECT ASSEMBLAGES FROM ILLINOIS
by
Kristine D. Carter
Bachelor of Science, North Dakota State University, 1981 B~chelor of Arts, Moorhead State University, 1978
A thesis submitted to the graduate faculty of the University of North Dakota in partial fulfillment of the requirements for the degree of Master of Arts
Grand Forks, North Dakota
May
1985 I"
This thesis submitted by Kristine D. Carter in partial fulfillment of the requirements for the degree of Master of Arts from the University of North Dakota is hereby approved by the Faculty Advisory Committee under whom the work was done.
This thesis meets the standards for appearance and conforms to the style and format requirements of the Graduate School of the University of North Dakota, and is hereby approved.
Dean the Graduate School
55297:1 l. l. Permission
Title Middle and Late Wisconsinan (Pleistocene)
Insect Assemblages from Illinois Department -'---'---'--""'------Geolo Degree Master of Arts
In presenting this thesis in partial fulfillment of the requirements for a graduate degree from the University of North Dakota, I agree that the Library of this University shall make it freely available for inspection. I further agree that permission for extensive copying for scholarly purposes may be granted by the professor who supervised my thesis work, or in his absence, by the Chairman of the Department or the Dean of the Graduate School. It is under stood that any copying or publication or other use of this thesis or part thereof for financial gain shall not be allowed without my written permission. It is also understood that due recognition shall be given to me and the Univer sity of North Dakota in any scholarly use which may be made of any material in my thesis.
Signature ~ :1;...:.,. LJ. 01,~ Date 3-//-1£;-
iii TABLE OF CONTENTS
LIST OF ILLUSTRATIONS .v
LIST OF TABLES .. .vii
ACKNOWLEDGMENTS. .viii
ABSTRACT •...• ...... • • • • • • • • • • • .. X
INTRODUCTION...... ~ . .1 Objectives. • 1 Theory ••.•• . 4 Previous Work. .8
REGIONAL SETTING ..••••.• • .10
Modern Environment •.•.••...•. .10 Wisconsinan Geologic History. .10 Vegetational History .•••...•• .19
LOCATION AND DESCRIPTION OF SITES ..••..••...•....•....•.• 21
Athens North Quarry Site. 21 Biggsville Site ...... 23
METHODS OF AN ALYS IS ••...... • 2 7 Sample Collection. .27 Laboratory Methods. .28 Mathematical Treatment. .31
RESULTS ...... 34
Sediment Analysis. .34 Faunal Analysis ••• .34
DISCUSSION ••.••..•••.•. .65
Local Environment at the Athens North Quarry Site. .65 Local Environment at the Biggsville Site. .80 Regional Climate Interpretation ...... • 91 CONCLUSIONS ...... • 107 APPENDIX .••• • 109
Appendix A. Sample interval depths, sample weights, and numbers of beetle individuals and taxa per interval ...... 110 REFERENCES ..• ...... 115
iv LIST OF ILLUSTRATIONS
Figure
1. Location of Wisconsinan and Holocene midcontinental North American fossil beetle sites ..••...•...•••...•• 2
2. Physiographic divisions of Illinois •..•••.•.••••••.. 11
3. Diagrammatic cross-section showing the formations and members of Wisconsinan age in northern and western Illinois ...... 13
4. Quaternary deposits of Illinois ...•....•...••...... 14
5. Time-stratigraphic and rock-stratigraphic units and absolute dating of the Wisconsinan deposits in central Illinois ...... 15
6. Measured stratigraphic section, Athens North Quarry site, Illinois •.••.••••.. , •...••...•....•.... 22
7. Measured stratigraphic section, Biggsville site, Illinois ...... 24
8. Sediment size, amount of organic carbon, and percent of fossils that are corraded, Athens North Quarry site, Illinois •.••••.•.••.•••.•••....•. 35 9. Species diversity and numbers of aquatic taxa, Athens North Quarry site, Illinois ..•..••.•.•••..••. 44
10. Trellis diagram of Jaccard similarity coefficients showing faunal zones, Athens North Quarry site, Illinois ...•...•••.••••..•.•..•....••...... •.•....•. 46
11. Clustering of sample intervals, Athens North Quarry site, Illinois ...... 47 12. Species diversity and numbers of aquatic taxa, Biggsville site, Illinois ••.••••..••••....•.•••..•.• 62
13. Trellis diagram of Jaccard similarity coefficients showing fauna! zones, Biggsville site, Illinois ••••. 63
14. Clustering of sample intervals, Biggsville site, Illinois ...... 64 15. Sample intervals, lithology, and faunal zones of the Athens North Quarry and Biggsville sites, Illinois .. 73
16. Present distribution of~ borealis (Coleoptera: Scolytidae) ••...•••...•....••..••...... 92 17. Present distribution of Chlaenius alternatus (Coleoptera: Carabidae) •..••...••....••.•...•...... 93
18. Present distribution of Bembidion morulum (Coleoptera: Carabidae) •.•••.•.••.••••.•.•...... •... 94 19. Present distribution of Orthotomicus caelatus (Coleoptera: Scolytidae) ...••••••.....•..••..••...•. 95
20. Present distribution of Bembidion frontale (Coleoptera: Carabidae) •••••.••....••...•...... ••. 96
21. Present distribution of Agonum corvus (Coleoptera: Carabidae) ...... •••...... ••...... 97
22. Present distribution of~ latidens (Coleoptera: Scolytidae) •.....••••••...•.•...... ••. 99 23. Present distribution of Micropeplus cribratus {Coleoptera: Micropeplidae) •...•.•••••••••.••..•..• 100
24. Present distribution of Sphaeroderus nitidicollis brevoorti (Coleoptera: Carabidae) •.•••••..••••.•.•. 101
25. Present distribution of Carphoborus andersoni (Coleoptera: Scolytidae) ..•.••..•....••...•..•..•.. 102 26. Numbers of species represented in the Athens North Quarry and Biggsville beetle assemblages which pr~sently occur in the provinces of Canada and the s =es of the United States ..•••••.•.•..•...•.••... 104
Plate I. Fossil Coleoptera from the Athens North Quarry and Biggsville sites .....•..•...••....•...•...... ••... 42 II. Fossil Coleoptera from the Biggsville site ..••.••..• 60 LIST OF. TABLES
Table
1. Midcontinental North P ,rican fossil beetle sites .... 3
2. Taxonomic list of the coleopteran fauna from the Athens North Quarry site, Illinois •.•....•...... 37
3. Total numbers of coleopteran individuals of each taxon per sample interval, Athens North Quarry site, Illinois ....•••.....•....•..••....•••.••••••.. 40
4. Taxonomic list of the coleopteran fauna from the Biggsville site, Illinois ••..••.•...... ••..••.•.••.• 49
5. Total numbers of coleopteran individuals of each taxon per sample interval, Biggsville site, Illinois ...... 54 6. Sample interval depths and sample weights, Athens North Quarry site, Illinois ..•..••.•...... •..•...•. 111
7. Sample interval depths and sample weights, Biggsville site, Illinois ••.•••...••••...••..••.... 112
8. Numbers of identified beetles and minimum number of taxa per interval, Athens North Quarry site, Illinois ...... 113
9. Numbers of identified beetles and minimum number of taxa per interval, Biggsville site, Illinois .•..... 114 ACKNOWLEDGMENTS
I would like to thank the many people who gave me help
and support during this undertaking, and made this thesis possible. I am grateful to Dr. John R. Reid, the chairman
of my thesis committee, for his guidance, patience and
understanding during the preparation of this manuscript. I
thank the members of my committee, Dr. F. D. Holland, Jr.
and Dr. Allan c. Ashworth for their help and cooperation. I am especially grateful to Dr. Ashworth for introducing me
to fossil beetles and directing my research. Dr. Donald P.
Schwert also gave me invaluable advice and assistance during this project.
I am grateful to the following people for helping with
sample collection: Dr. R. G. Baker, Dr. G. R. Hallberg, J.
W. Hoganson, Dr. F. B. King, and Dr. J.E. King. Dr. R. G.
Baker and Dr. G. R. Hallberg allowed me access to their description of the Biggsville site. Dr. R. J. Stevenson did the SEM photography of my fossils, and Dr. R. D.
LeFever helped me with statistical methods. I also thank Dr. w. D. Gosnold for the use of his microcomputer.
The use of the facilities and the assistance of the staff of the Canadian National collection is gratefully acknowledged. I am indebted to Dr. D. E. Bright, Dr. J.M. Campbell, Dr. H. Goulet, Dr. J. McNamara, and Dr. A. Smetana for their help in the identification of my beetle fossils. I am also grateful to Dr. J. v. Matthews, Jr. of the Canadian Geological Survey for his help in beetle determinations, and Dr. E. U. Balsbaugh, Jr. allowed me access to the North Dakota State Insect Collection at North
Dakota State University. Thanks also go to Dr. A. M.
Cvancara for his determination of my gastropod fossils.
I thank the National Science Foundation (grant number
DEB 80 2392 -- A. C. Ashworth and D. P. Schwert, principal investigators; grant number BSR-840070 -- D. P. Schwert and
G. R. Hallberg, principal investigators) and the Graduate School of the University of North Dakota (Graduate Student Research Grant) for providing funding for this study. I am also grateful for the use of the facilities of the North
Dakota Geological Survey and the Geology Departments of the
University of North Dakota and North Dakota State University.
My mother, Stella Ziegler, and family, especially
Debra Sannes and Jack and Imogene Carter, have given me considerable support throughout my education and I am deep ly grateful. Finally, a very special thanks for his sup port, patience, and confidence in me goes to my husband,
Brian.
ix ABSTRACT
Two highly organic sediment sequences from central and western Illinois (the Athens North Quarry and Biggsville
sites, respectively) of Middle and Late Wisconsinan age were studied to gain knowledge about the environment and climate of this area during the time immediately prior to the maximum extent of the last glaciation. Paleoenviron mental and paleoclimatic inferences are based principally upon knowledge of the habitat preferences and geographic distributions of extant species of beetles that are repre sented as fossils. These data are supplemented by informa tion from sedimentological and taphonomic studies and from previously published palynological and plant-macrofossil studies.
The Athens North Quarry site is a 2.8 m-thick sequence of organic silt, ranging in age from about 25,000 to 22,000
11 c yr B.P. Two faunal zones based upon beetle fossils were recognized; a third was defined using gastropods. The environment, inferred from the fauna, was the margin of a eutrophic lake surrounded by a moist coniferous forest.
The sequence of events at the Athens North Quarry site began with the expansion of a nearby lake or pond over the forest floor, and ended with the infilling of the water body by Woodfordian loess and organic material. The Biggsville site is a channel-fill deposit con sisting of fluvial deposits, organic sediments, peat, and
loess. Samples for beetle analysis were collected from a 2.2 m-thick section of organic loams and peat ranging in age from 27,870 ~ 290 to 21,410 ~ 290 ~Cyr B.P. Two coleopteran faunal zones were recognized. Habitats in ferred from the beetle species present in these zones are interpreted as representing the development and demise of a bog in an abandoned stream channel, surrounded by a thin, spruce-dominated coniferous forest. The bog and forest were eventually choked by peat and loess deposits. This was followed by a period of pedogenesis.
An interpretation of the climate of central and western Illinois between about 28,000 and 21,000 '~c yr B.P. is based upon the present ranges of the species repre sented by fossils in the Athens North Quarry and Biggsville sites. The majority of these species now occur in the southern boreal forest region of southern Canada and northern United States. The climate during this period apparently was relatively stable, in contrast to the inter pretation of previous workers in this area; compositional changes in the coleopteran assemblages are interpreted as reflections of local changes in the environment rather than as indications of the shift from interstadial to full glacial conditions.
xi . ;. INTRODUCTION
Objectives
A wealth of information has been gathered about the environmental and climatic conditions during the Wiscon sinan of midcontinental North America from the interpreta tion of fossil insects (Figure 1, Table 1). Schwert and
Ashworth (1982) proposed that at the time of maximum Late
Wisconsinan glaciation, a beetle fauna with tundra and tree-line affinities inhabited the Midwest. Further, they said that this fauna subsequently became regionally extinct as the climate ameliorated. Little is known, however, about the fauna, environment, and climate in this region during .the period immediately prior to the last glaciation.
To gain knowledge about this period of environmental history, two highly organic sediment sequences of Middle and Late Wisconsinan age in central and western Illinois were examined for beetle fossils. They are referred to as the Athens North Quarry site and the Biggsville site, respectively. These sites were chosen because of their accessibility, overlapping ages, and their proximity to the boundary of maximum Wisconsinan glaciation. The specific objectives of this study are: 1. To describe the coleopteran fauna of each site. 2. To interpret the paleoenvironmental and paleoclimatic conditions based upon knowledge of 2
I' ,'--- I --- ... __ -,
I
I I ' I \' I
0--- 100ml 1. Gervais a. Norwood 2. Biggsville 9. Two Creeks 3. Athens North Quarry 1 O. Johns Lake 4. Garfield Heights 11. Mosbeck 5. Champaign County 12. Seibold 6. Elkader 13. Bongards 7. Conklin 14. Stanton
Maximum extent of Late Wlsconsinan ice sheets (Ruhe, 1983, p. 133)
Figure 1. Location of Wisconsinan and Holocene midcontinental North American fossil beetle sites. 3
Table 1
Midcontinental North American fossil insect sites.
Site name Age ( Mc yr B.P.) Describing authority
Gervais >46,900 Ashworth (1980) ?Early Wisconsinan
Garfield Heights ca. 24,000 Coope (1968)
Athens North Quarry ca. 25,170 - this study 22,170
Biggsville 27,870 - 21,410 this study
Champaign County Middle Wickham (1917) Wisconsinan
Elkader 20,530 Schwert (1982)
Conklin 17,170 Schwert (1982), Schwert et al. (1981) --
Norwood 12,400 - 11,200 Ashworth et al. (1981)
Two Creeks 11,860 Morgan and Morgan ( 19 79)
Johns Lake 10,800 Ashworth and Schwert (1981)
Mosbeck 9,940 Ashworth et al. (1972)
Seibold 9,750 Ashworth and Brophy (19721
Bongards 3,500 Schwert and Ashworth (in press)
Stanton 325 Fischer (1980) 4
the requirements of the identified beetle taxa
and of the lithology of the sediments.
3. To compare the inferred environmental and climatic data with that derived from other
paleoenvironmental and paleoclimatic indicators
in the region.
Theory
Fossil beetle assemblages have been used as indicators of past environments and climates since pioneering studies in the British Isles by G. R. Coope in 1959. Coope (1967,
1970, 1975, 1977a, 1977b, 1978, 1979) summarized the reasons why beetle fossils are valuable paleoenvironmental indicators:
1. Fossil beetles occur commonly in Quaternary
lacustrine and fluvial deposits. 2. Fossil beetles may be separated easily from
the sediment by kerosene flotation.
3. The robust coleopteran exoskeleton is often well
preserved with great morphologic detail and may be identified by comparison with modern species.
4. The taxonomy and geographic distribution of beetles are known for the palearctic and nearctic biogeo
graphic provinces. 5. Beetles are very precisely adapted to a wide variety of habitats. 6. Adult beetles are often highly mobile and can 5
respond rapidly to changes in the physical environment.
Ecological and climatic interpretations based upon
fossil beetle assemblages are dependent upon three basic
assumptions. The first of these concerns species con
stancy. Beetle species have undergone no detectable mor phological evolution during at least the last half of the
Quaternary period (Coope, 1970, 1975, 1977a, 1977b, 1978,
1979). Coope (1977b) considered morphological stability of
beetle species an essential prerequisite for their use as environmental indicators. He said gradual morphological differences from the species' modern counterparts would almost certainly have been associated with physiological change, which would in turn have changed their environ mental tolerances. The only evidence so far for evolu tionary change during the Pleistocene is Matthews' (1974) analysis of progressive wing reduction in the staphylinid species Tachinus apterus. Later work by Matthews (1976a,
1976b), on deposits of the Beaufort Formation from Meighen Island {Canadian Arctic Archipelago) and Lava Camp, Alaska, demonstrated that speciation did occur during the late Tertiary.
Extinctions of beetle species during the Quaternary are rare. Most species of beetles named from Pleistocene faunas have been put in synonomy with extant species. 6
Spilman (1976) described a species of Ptinidae, ftinus
priminidi, from fossil packrat middens of late Pleistocene
age in California and Arizona. This species, in the opin
ion of Ashworth (1979), could represent an undiscovered
member of the extant fauna. Miller et al. {1981) discussed
two extinct scarab beetles, Copris pristinus and
Onthophagus everestae, from late Pleistocene asphalt de
posits in California. They also believed that one or both
of these species may yet be discovered in inadequately
collected regions of Mexico, where their closest relatives
are presently found.
A second assumption is that the habitat requirements
of species are essentially the same as they were in the past (Coope, 1967, 1970, 1975, 1~77a). Because ecological
needs are determined by an organism's physiological make
up, Coope (1977a) considered it important to examine the
possibility of physiological evolution without associated
morphological change. He said that gradual physiological changes would produce ecologically mixed fossil assemblages which would become increasingly dissimilar to present day
populations with increasing age. Although ecologically mixed assemblages do occur, Coope (1977a) maintained that
they are relatively rare and usually represent transitional faunas characteristic of periods of rapid environmental change. 7
The third assumption is that the geographic ranges of the species are controlled by factors in the physical
environment (Coope, 1967, 1975). Factors which influence
distribution are summarized from Coope (1967). He pointed out that, in most cases, the suitability of a habitat involves a complex combination of these conditions:
1. Thermal environment -- Species must have an
adequate amount of heat to complete their life
cycles or reach a stage of development suitable
for hibernation before seasonal temperatures
reach the threshhold below which the beetles
become inactive. The impact of the thermal
environment may be influenced by wind exposure
and the conductivity of the substrate, or may
be buffered in habitats such as heat-generating,
decomposing vegetable matter, water, or burrows.
2. Soil conditions -- The particle size and organic
matter content of the soil are particularly important to ground-dwelling and burrowing species.
3. Hygric fa~tors -- Water energy, organic-matter
content, pH, and temperature of the water directly
influence species which spend all or part of their
life cycles in water. Other moisture-dependent
species live beside water or in damp or marshy places.
4. Chemical factors -- The pH and salinity of the soil and water are determining factors in the 8
habitat choices of some beetle species.
5. Botanical factors -- The distribution of species
dependent upon specific plants for food or shelter
is in turn dependent upon the availability of those
plants. Other related requirements may include the
presence of vegetable litter, trees, and shade.
6. Special factors -- This category includes such
factors as the dependence of predatory species on
certain prey, and the presence of carcasses or
dung.
Previous Work
Morgan -.-et --al. (1983) have reviewed the recent North American paleoentomological literature and have summarized the results of studies in a region-by-region account. The older literature and its significance has been reviewed by
Ashworth (1979) and Morgan and Morgan (1980).
Few paleoentomological sites of Middle Wisconsinan age have been examined in the Midwest. Fossil beetles from peat deposits in Champaign County, Illinois (Figure 1), were studied by Wickham (1917). He interpreted these de posits td be of Sangamonian age, and deduced from the beetle assemblage a boreal environment with climatic condi tions more rigorous than at present. Ashworth (1979), however, believed that, from their geographic position, these deposits may be of Farmdalian age. 9
The only recent study of a Middle Wisconsinan beetle
fauna is Coope's (1988) description of fossils from 24,000
14c yr B.P.-old, plant-rich silts at Garfield Heights, Ohio
(Figure 1). He identified 26 beetle individuals from a
sample weighing about two kilograms. His interpretation of this fauna suggested an environment that was open and
rather barren, with a scattered vegetation of low plants, carpets of moss, and a few trees. The presence of well drained, as well as damp soil, and the proximity of standing, or slowly flowing water were also implied. The climatic conditions suggested by this fauna indicated that conditions in front of the advancing glacier in early
Woodfordian time (24,000 14c yr B.P.) were more similar to those present1y near the northern fringes of the boreal forest of North America than to those presently existing in the region. REGIONAL SETTING
Modern Environment
The Athens North Quarry and Biggsville sites are in the Till Plains Section of the Central Lowlands Province
(Figure 2). This section has a subdued glacial topography developed largely on Illinoian drift. The Athens North Quarry site is in the Springfield Plain District and the
Biggsville site, in the Galesburg Plain District. The Springfield Plain is characterized by its flatness and shallowly entrenched drainage, whereas the Galesburg Plain includes a level to undulatory till plain with few morainic ridges, and more sharply incised valleys (Leighton et al., 1948).
Espenshade and Morrison (1976) described the modern environment of Illinois. The climate of Illinois is humid continental. Average annual precipitation is 700 to 1,000 mm per year. The average length of the frost-free period is 160 to 200 days. Pre-settlement vegetation consisted of oak-hickory forest mixed with tall-grass prairie. Present land usage in Illinois is predominantly feed-grain and liv.estock production.
Wisconsinan Geologic History
The Late Quaternary geologic histories of the Athens 11
CENTRAL LOWLAND PROVINCE
OZARK
PLATEAUS
PROVINCE
INTERIOR LOW PlATE:AUS , ,. .. ---==-"' PROVINCE: COASTAL PLAIN PROVINCE: ILLINOIS STAr~ tiZOJ.OIZICAL SURVCY
Figure 2. Physiographic divisions of Illinois (modified from Leighton et al., 1948, p. 18). 12
North Quarry and Biggsville sites are similar. Neither
site was glaciated during the Wisconsinan. The strati
graphic units analyzed in this study were deposited during
the Farmdalian and early Woodfordian Subages of the Wis-
consinan Age (Follmer ~., 1979; Hallberg and Baker,
written communication to D. P. Schwert, 1981). The strati
graphic relationships of the Wisconsinan Stage are sum
marized in figure 3. A map of the surficial deposits of
Illinois is presented as figure 4.
Mayewski al. (1980) summarized the time-stratigra-
phic units of the Late Quaternary in the Great Lakes
region. The Wisconsinan Stage in Illinois has been sub
divided (Figure 5) into five substages: Altonian, Farm
dalian, Woodfordian, Twocreekan, and Valderan (Frye and
Willman, 1960; Willman and Frye, 1970; Follmer ~.,
1979). As a result of their reinterpretation of the type
locality, Evenson et al. (1976) suggested that the Valderan
Substage be replaced with the Greatlakean Substage. This change has yet to gain universal acceptance. Dreimanis and
Karrow (1972) found the classification of Frye and Willman to be unsatisfactory and suggested that the Wisconsinan
Stage be subdivided into three substages: the Early,
Middle, and Late Wisconsinan. Dreimanis and Karrow placed the boundary between the Early and Middle Wisconsinan at the base of the Port Talbot I beds in the eastern Great
Lakes region (pre-50,000 years B.P.); the boundary between 13
TWOCREEKAN ANO VALO(RAN SUSSTAGES
.• ~• Juiu s~1 o ., TT'l1TfTTfrn; ; "'... ~• "' z < .,:!': z 0 u V, 3' w ... ··: cQO;¢;; 'nir.Nle~··;;,:::·::: .:;:.;· ~ "' ..." Ptat10 SI It M«mbe, Q "'.. ••.' ... ::•A ,9·., if• r/1i.M e~ ~-~-,~-:::;·-~::·-:·:.: :::=-::~::.~ l " "'z tilts ~ "i: ~· ...0 ~ __,':: ~;,' ': ..::: .t!>.f~{i.~ l " $1lt'.i . '
Figure 3. Diagrammatic cross section showing the formations and members of Wisconsinan age in northern and western Illinois (modified from Willman and Frye, 1970, p. 70). 14
QUATERNARY DEPOSITS OF ILLINOIS
Jerry A. Lineback 1981
0
O 50km 'j F3 Fi'
AGE UNIT
Cahokia Allt.ivium. Hofoeerttt t=:=::j .... Parldand S.nd, and Wisconsinan Henry Fo,mation COfllbined; aUuvium, windblown 'IGl'ld, al'ld sand and gravfl outwash. Wlsconiinan
EQualitv Formation; 1ili:, ctav. and =i;,_;_;_;_;i tand in glacial and 1lack"water lakes. Wfldron and Trafalgar tJ~M Moraine Formations combined; ~Grau~ gJ~jal till with some ~ maralne sand, grayef, and .1Ht. Winn.tttMgo 4nd Gl&tfcrd Formations combined: gladal lili with some sand. gtavel, and silt; .191;: 11u.ignmenu ol some units is uncen:ain.
T~lfflffe Silt, Pearl Formation, and Hagatnawn Membff of 1ha Gla.fal'd formation i::ombined; lak• 1ilt and day, outwnb t.and, grawl, and s,IL
Wolf Cr~k Formotion; glocial till with 9'~. sand~ tSGS 1981 - and Ult. CJ BMStoek.
Figure 4. Quaternary deposits of Illinois (modified from Lineback, 1981). 15
14c YR LITHOSTRATIGRAPHY CHRONOSTRATIGRAPHY B.P.
(I) C Ul (I) Q) o.- o- ~ :::c 7,000 Valderan Substage 11,000 Twocreekan Richland Substage l E 12,500 Loess -rl) >, (I) >, ... Peoria al C: rl) Alton Ian Roxana Slit Substage Figure 5. Time-stratigraphic and rock-stratigraphic units and absolute dating of the Wisconsinan deposits in central Illinois (modified from Follmer t al., 1979, p. 4). - 16 Middle and Late Wisconsinan was placed at the base of the Catfish Creek drift, ·at about 24,000 years B.P. Finally, they placed the Late Wisco.nsinan-Holocene boundary at 10,000 years B.P. During the first of the Wisconsinan subages, Altonian glaciers of the Lake Michigan and Green Bay Lobes entered Illinois (Willman and Frye, 1970). Follmer et al. (1979) described the lithologic units deposited during this sub age. Tills of Altonian age comprising the Winnebago Forma tion were deposited only in the northern part of the state. Meltwater and valley train deposits extended southward down the ancient Mississippi Valley and provided source areas for the uplarid loess deposits of the Roxana Silt. Most of this formation was deposited between 45,000 and 30,000 years B.P. According to Watts (1983), the Altonian Subage lasted from about 60,000 to sometime before 28,000 years B.P. During the warmer Farmdalian Subage, glaciers re treated to at least within the Lake Michigan Basin, but there is no direct evidence for the deglaciation of the continent (Frye and Willman, 1973). Watts (19831 suggested that because there is limited correlation of the deposits of this subage outside of Illinois and little evidence for a Farmdalian interstadial phase in marine cores, the use of "Farmdalian" should be restricted to the margins of 17 the Lake Michigan Lobe at present. The age range of the Farmdalian, as defined at its type section (28,000 to I~ 22,000 Cyr B.P, Frye and Willman, 1960) has been shortened by McKay (1979) to 28,000 to 25,000 ~c yr B .P. based upon more recent radiocarbon dates. The Farmdalian Substage represented a brief pause in loess accumulation and a period of pedogenesis (Follmer et ~., 1979). Evidence discussed by McKay (1979) from sites along the Mississippi Valley in southwestern Illinois sug gested that loess deposition in near-source areas slowed substantially during this substage but never ceased entire ly. According to Frye and Willman (1973), the peats and organic-rich silts of the Robein Formation were also depos ited during this time. The Robein Formation overlies the Altonian Roxana Silt and Winnebago Formations. The Farm dale Soil, described by McKay (1979), is weakly developed in the Robein and Roxana Formations (Figure 3). It lacks a structural or textural B horizon and often consists of a thin weakly-expressed A horizon over a carbonate-leached C horizon. Such a soil indicates that the Farmdalian inter stadial was brief and that the peak intensity of pedo genesis during this substage was at a low level. During the Woodfordian Subage, Illinois was invaded again by the glaciers of the Lake Michigan and Green Bay Lobes from a northerly d~rection, and by the Erie Lobe and 18 perhaps the Saginaw Lobe, from the east and northeast, respectively (Willman and Frye, 1970). The ice advance was preceded by the accumulation of proglacial loess deposits, the Morton Loess within the Wisconsinan glacial limit, and the Peoria Loess beyond that limit. At several sites in Illinois, the lower sections of these formations contain organic zones consisting predominantly of wood, twigs, and needles (McKay, 1979). Radiocarbon dates for the base of these units indicate that the glaciers reentered the ancient Mississippi drainage basin at about 25,000 1~c yr B.P., 6,000 years before reaching their maximum extent at about 19,000 14 c yr B.P. in the Peoria area of central Illinois (Follmer et al., 1979). Tills of the Wedron Formation overlie the Morton Loess (Figure 3). Deposition of the Peoria Loess continued throughout the Woodfordian beyond the limits of the glacier (Follmer et~., 1979). The Jules Soil, developed in the Peoria Loess, implies a period of slowed loess accumulation that coincided with a major retreat of glacial ice of the Lake Michigan Lobe (McKay, 1979). Loess, deposited over the till units as the glacier receded, comprises the Richland Loess. Other Woodfordian deposits include large areas of outwash (Henry Formation) and lacustrine deposits formed in backwater lakes (Equality Formation). The Wood fordian Subage ended about 12,500 l4c yr B.P. {Follmer, et al., 1979). 19 According to Willman and Frye {1970), events of the Twocreekan and Valderan (or Greatlakean) Substages are recognized in Illinois only by the fluctuation of lake stages and by terraces along major valleys. Loess deposi tion probably continued but at a greatly reduced rate, and the amount of loess of post-Woodfordian age in the Peoria and Richland loesses is probably minor. Vegetational History Pollen and plant macrofossil studies from a number of sites in Illinois {Gruger, 1972a, 1972b; F. B. King, 1979; J. E. King, 1979, 1981; Whittecar and Davis, 1982), Wis consin (Dirlam, 1979), and Iowa (Hallberg et al., 1980; Mundt and Baker, 1979; Van Zant et al., 1980) have provided evidence for the presence of a closed-canopy Picea-Pinus boreal forest during the late Altonian, Farmdalian, and early Woodfordian Substages. Berti (1975) found no evi dence for forest-tundra or tundra. The forest was dom inated by Pinus during the late Altonian and early Farm dalian time. Subsequently, species dominance shifted to Picea (Dirlam, 1979; Hallberg et al., 1980; Mundt and Baker, 1979; Van Zant et~-, 1980; Whittecar and Davis, 1982). This change from pine to spruce dominance was time transgressive, occurring at about 36,000 14c yr B.P. in northernmost Illinois (Whittecar and Davis, 1982) and cen tral Wisconsin (Dirlam, 1979), and at approximately 25,000 •4c yr B.P. in southeastern Iowa (Hallberg, et al., 1980). 20 Picea did not appear until about 21,000 '4c yr B.P. in south-central Illinois (Gruger, 1972a). Whittecar and Davis (1982) suggested that the compositional shift within the coniferous forest may have been part of a southward and westward expansion of the spruce-dominated boreal forest, presumably in response to climatic deterioration prior to the advance of Woodfordian ice. Macrofossils of ----Larix and Abies studied by F. B. King (1979) from central Illinois made their first appearance in the fossil record of the spruce-dominated forest between about 23,000 and 22,000 14 c yr B.P. They also provide evidence for a shift from mild interstadial conditions to colder, moister full-glacial conditions. LOCATION AND DESCRIPTION OF SITES Athens North Quarry Site The Athens North Quarry site is at the north end of the Indian Point Quarry of Material Services Corporation, in the SEl/4, NEl/4, sec. 18, T.18 N., R.5 w. of Menard County, Illinois (Figure 1). The section studied is located approximately 90-145 m north and east of that des cribed by Follmer et £1.l· (1979). The sampled section is illustrated in figure 6. The base of the sequence (6.2 m below ground surface) is dark gray (5Y4/1) clayey silt of unknown thickness. Overlying this unit is a distinct, 0.3 m-thick bed of black (10YR2.5/l) silty muck. Above the muck is 2.2 m of dark grayish brown (2.SY4/2) to black (10YR2.5/1) organic-rich silt. Organic fragments are present throughout the silt but abundant spruce wood, needles and cones are concen trated in certain layers. The organic-rich silt unit is overlain by 3.6 m of greenish-gray (5GY5/1), limonite stained, inorganic silt. The time-stratigraphic, rock-stratigraphic, and soil stratigraphic nomenclature, and the ages of the principal boundaries in the Athens North Quarry site (Figure 6) follow Follmer et al. (1979). The bedded clayey silt and overlying silty muck unit belong to the Robein Silt 21 22 Depth Cm) - 1 - inorganic -2- silt CD Cl (/) (/) -.."' (I) .Q 0 :::, ...I c.. 3 . 14 (I) C YR B.P. CG C ·.: "' 0 'O.. (I) -?-22,170 0 Q. i200 -"C - 4- 0 .. 0 (I) organic C. 3: E silt "'., - 5 - (I) (I) -(I) al ?-25, 170 - 6 - muck .t.450 C - al CD en - Cl C: clayey ,,-iii "' (I) e1: .0 '" 7 - silt .. :::, 0 "'(I) IJ.. a: Figure 6. Measured stratigraphic section, Athens North Quarry site, 'Illinois. 23 of Farmdalian age. The muck unit has been correlated with the Farmdale Soil (Follmer et~., 1979). The overlying organic and inorganic silt units belong to the Peoria Loess of Woodfordian age. A wood and muck sample, reported by Follmer et al. (1979), from the contact zone of the muck unit and the overlying organic-rich silt was dated at 25,170 ~200 14c yr B.P. (Illinois State Geological Survey, ISGS-536) and a wood sample from near the top of the organic-rich silt unit was dated at 22,170 +450 14 c yr B.P. {ISGS-534). The underlying Roxana Silt of Altonian age and the Glasford Formation of Illinoian age described by Follmer et al. (1979) were not exposed in the sampled section. The Quaternary deposits rest on Pennsylvanian carbonates ot the Modesto Formation. Biggsville Site The Biggsville site is on the south overburden face of the Biggsville Quarry, in the SWl/4, sec. 17, T.10 N., R.4 w. of Henderson county, Illinois (Figure 1). The lithology of the section was described by G. R. Hallberg and R. G. Baker of the Iowa Geological Survey (Hallberg and Baker, written communication to D. P. Schwert, 1981). The sampled section is illustrated in figure 7. Measured depths begin at the upper surface of the modern soil (beneath the spoil). The base of the sequence (6.2 m below the surface) is coarse cobble gravel with a dark 24 Depth (m) spoil -0 modern soil - 1 - - 2 . Peoria Loess -3· 14C YR B.P. -4 - ,_ 21,410.t.290 loess paleosol .. - 7 - gravel Figure 7. Measured stratigraphic section, Biggsville site, Illinois (from Hallberg and Baker, written communication to D. P. Schwert, 1981). 25 greenish-gray (5GY4/1) sandy loam matrix of unknown thick- A ness. The gravel is underlain by Mississippian limestone, not exposed in the measured section. Overlying the gravel is a 0.16 m-thick unit of dark olive-gray (5Y3/2) bedded, organic, sandy loam with an admixture of pebbles near the base, overlain in turn by 0.3 m of very dark grayish-brown (2.5Y3/2 and 10YR3/2), bedded, organic, s~lty loam. Well preserved moss mats occur along the bedding planes of this loam. The unit is overlain by 0.45 m of dark brown (7.5YR3/2) to dark reddish-brown (5YR3/4) and very dark grayish-brown (10YR3/2) silty peat containing some thin beds of fine sand and some mats of decomposed moss. Above the silty peat is a 0.76 m-thick unit of peat, dominantly fibrous, bedded, and dark reddish-brown (5YR3/4) to very dark brown (10YR2/2), and very dark gray (10YR3/1). It contains woody fragments which increase in abundance toward the top, where some beds are almost entirely of wood. A thin (0.18 m) unit of very dark gray (5Y3/1) to black (5Y2.5/1) organic-rich, mucky, silty loam to silty clay overlies the peat. The uppermost sampled unit is a 0.16 m thick basal loess paleosol, a silty loam. The dominant colors of the paleosol are very dark gray (5Y3/ll, dark olive-gray (5Y3/2) and black (5Y2.5/1). It is organic rich, has some fibrous organic matter and contains a few wood fragments. Some zones are clearly bedded. Above the basal loess paleosol is a thick (3.35 m) unit of light grayish-brown (2.5Y6/2) deoxidized and leached Peoria 26 Loess, overlain by 1.07 m of truncated and disturbed modern soil. Spoil and crushed rock cover the modern soil unit. Four samples from the Biggsville section were radio carbon dated by the Iowa Geological Survey (Figure 7). Their ages range from 27,870 ..:420 (Beta 4129) to 21,410 _:290 (ISGS-1231) 14c yr B.P. (Hallberg and Baker, written communication to D. P. Schwert, 1981, 1984). METHODS OF ANALYSIS Sample Collection The Athens North Quarry site was sampled in June 1979 by J. E. King, F. B. King, A. C. Ashworth, D. P. Schwert and me. An exposure face in the east wall of the quarry was cleaned to eliminate the possibility of contamination of the fossil assemblage by living forms. Bulk samples of sediment weighing between 3 and 12 kg were collected at 20- cm intervals, beginning at a depth of 3.4 m and continuing to 6.2 m. All samples were sealed in plastic bags and stored at room temperature until processing. Two hundred grams from each sample were reserved for textural and organic carbon content analyses and sealed in plastic bags. The Biggsville site was sampled in June 1981 by G. R. Hallberg, R. G. Baker, A. C. Ashworth, D. P. Schwert, and J. w. Hoganson. Bulk samples of sediment weighing between 2 and 6 kg were collected at 10-cm intervals from a cleaned section of the south overburden face in the quarry. Sam pling began at a depth of 4.42 m and continued to 6.62 m. All samples were sealed in plastic bags and stored at room temperature until they were processed. 27 28 Laboratory Methods Sediment Analysis Grain-size analysis was performed to determine the proportions of sand, silt and clay in the units of the Athens North Quarry site. The sediment was first treated with household bleach to remove the organic material present. The percentages of each textural category were determined using the method described by Perkins (1977); the sand content was determined by wet sieving, and the clay content by hydrometer. The silt content was calcu lated by subtracting the weight of the sand and the weight of the clay from the total weight of the sample. Organic carbon content was determined by hydrogen peroxide oxidation (Gross, 1971). Approximately two grams of sediment were treated with a 10% solution of hydrogen peroxide over heat until a minimal reaction was reached. The weight loss was calculated and converted to a percent age of the total weight of the sample. Insect Analysis Insect fragments were recovered using the flotation technique described by Ashworth (1979). Sediment was first washed through a 300 micron sieve. Disaggregation of peat samples was accomplished by first boiling them in a solution of Calgon and sodium carbonate for about one hour. The resulting residue was drained, transferred to a plastic 29 tub, and covered with kerosene. Kerosene adheres to chitin fragments, and because it is less dense than water, it will rise to the surface when mixed with water. The kerosene mud mixture was gently stirred for about five minutes, after which the excess kerosene was poured off, and cold water was slowly added to fill the tub. The mixture was allowed to settle for 15 minutes. Floating remains were decanted onto the 300 micron sieve. The tub was again filled with cold water and allowed to settle for 15 minutes. Floating remains were decanted onto the same sieve and washed with household detergent to remove the kerosene from the specimens. Beetle fragments were sorted under a binocular microscope and stored in 95% ethanol. Representative samples of non-coleopteran insect fossils and gastropods were also retained. Identifiable beetle and gastropod specimens were dried and mounted on micropaleon tological slides using a water soluble glue of gum traga canth and gum acacia. All slides were labelled with reference numbers indicating the site name, interval number and slide number and have been deposited in the Fossil Beetle Laboratory of the Geology Department, North Dakota State University, Fargo, North Dakota. The mounted fragments were identified by comparison with identified museum specimens in the insect collections of the Fossil Beetle Laboratory in Fargo and the Canadian National Collection (CNC), Department of Agriculture, in 30 Ottawa, Ontario, Canada. Recent taxonomic literature con taining keys and illustrations of species was also helpful. Several specimens were referred to taxonomic specialists for identification or for confirmation of identification. ln cases where a species or generic name could not be assigned with absolute certainty due to either the incom pleteness of the fossil or to the absence of markedly diagnostic characteristics in the modern or fossil speci men, the taxonomic name was preceded by cf. Generic and specific identification was attempted only for the Coleop tera. The presence of small numbers of oribatid mites, and specimens of the Hymenoptera, and of the Arachnida was noted but they were not included in counts. Because a beetle has fou·r potentially identifiable parts (head, thorax, left elytron, right elytron), diffulculties arise when counting the minimum number of individuals for use in statistical analysis. These problems may be resolved by equating the maximum number of any one skeletal part of a taxon with the minimum number of individuals of that taxon. For example, a collection of 12 heads, 23 thoraces, 19 left elytra and 13 right elytra would represent a minimum number of 23 beetle individuals. Unidentified beetles were not counted or included in mathematical treatments. Certain intervals in the Athens North Quarry section contained a large proportion of corraded fragments. Counts were made of the corraded and non-corraded fragments and percentages of them were calculated for each interval. 31 Previous collecting localities for each definitely identified species from the Athens North Quarry and Biggsville sites were plotted on maps to facilitate the comparison of the geographic distribution of that species with others in the faunas studied. Locality information was collected from the literature (Ashworth S:! al., 1972; Bright, 1976; Campbell, 1968, 1982; Gordon, 1976; Lindroth, 1961, 1963, 1966, 1968, 1969; Wood, 1982) and from specimen labels in the insect collections at the Canadian National Collection (CNC) and the United States National Museum (USNM) in Washington, D.C. State or provincial records were used where specific collecting localities were not available. Species from both sites with similar geographic ranges were combined into categories called distribution groups for the purpose of inferring a modern analog for the distribution of the majority of the species. Mathematical Treatment Counts of the number of individuals of each taxon per interval for the Athens North Quarry and Biggsville sites were made. The percentages of aquatic Coleoptera per interval were also calculated. Aquatic beetles, as defined by Leech and Chandler (1971), are beetles that spend a significant portion of their life cycles in water. According to Schaak and Franz (1978), species diversi ty in an ecosystem may be' expressed by either the number of 32 species in a sample (simple species diversity) or by more complex measures that are sensitive to the numbers of individuals of each species in a sample (equitability). The latter interpretive values are dependent upon adequacy of sampling, whereas simple species diversity is a bias free measure of diversity. Because of the high number of taxa represented by a single individual per interval, com plex diversity measures, such as the Simpson Index, were unusable here. In such cases, the value of the index would be undefined mathematically. Therefore, a simple species diversity curve using the number of taxa in an interval versus the depth of that interval was constructed for each site. As used here, a taxon is the lowest possible level of taxonomic identification. Patterns of similarity among the fossil assemblages from sampling intervals were established by cluster analy sis of similarity coefficients. Jaccard's coefficient of similarity was chosen because of its simplicity and wide use in ecological studies. Following the example of Valentine (1966), this coefficient was calculated as the number of species common to two samples divided by the total number of different species present in both samples: CJ= c/(a+b-c) a and b = number of species in each sample, respectively c = number of species common to both samples The sample units were the sampling intervals of each 33 fossil site. Sample interval number 1 of the Athens North Quarry site ~as excluded from statistical analysis because it contained no beetle fossils. A trellis diagram was con structed to illustrate the degree of similarity between pairs of sample intervals. The coefficients were then subjected to cluster analy sis by the weighted pair-group method described by Davis (1973). In this method, intervals were arranged into a hierarchy such that intervals with the highest degree of mutual similarity were placed together. Then, groups or clusters were associated with other groups which they most closely resembled. The clustering process continued until all of the intervals were grouped together in the form of a dendrogram. RESULTS Sediment Analysis Sample interval depths and sample weights for the Athens North Quarry and Biggsville sites are listed in tables 6 and 7, respectively, of appendix A. The tex tural composition of the sediments of the Athens North Quarry site is illustrated in figure 8. All units contain less than 2% sand and less than 16% clay. Most of the sediment, 83 to 93%, is silt. The organic carbon content of the Athens North Quarry samples is plotted against depth in figure 8. The organic carbon content of the sequence reaches its highest value, 18%, within the lower part of the organic silt lithologic unit. Faunal Analysis Athens North Quarry site At least 279 coleopteran individuals representing 17 families have been identified from the Athens North Quarry site. A total of 61 taxa was determined below the level of family, including 14 identified to species. Of the number of beetles, 25% was classified as aquatic following the usage of Leech and Chandler (1971). A summary of the sample data is found in table 8 of appendix A. \"; i ,... :,, E Ol .... Ill f.7.!71 'll, % 'll, % .c .2 > t..i..:I sand ailt clay organic --- % corraded loaalla .. 0 .. D El carbon C. .c CD -- CD :!: .. C ..J .5 10 20 70 80 90 10 20 10 20 30 40 50 Inorganic sltt 1 2 3 4· 4 5 6 w organic en silt 7 8 5· 9 10 1 1 12 13 6· muck clayey slit 14 Figure 8. Sediment size, amount of organic carbon, and percent of fossils that are corraded, Athens North Quarry site, Illinois. 36 A taxonomic list of the beetles is included in table 2. A quantitative summary of the insect taxa and their numbers per sample interval is given in table 3. Scanning electron photomicrographs Of some represent ative fossil species from the Athens North Quarry site are shown in plate I. Fossils from both sites are included to demonstrate the quality of preservation of the fossil mate rial, rather than for any systematic purpose. Six geographic distribution groups were established to describe the ranges of the species from both sites. The groups to which the species from the Athens North Quarry site belong are listed in table 2. Those species tor which collecting locality information was not available are indi cated by U. Descriptions and illustrations of these dis ' I tribution groups will be included in the discussion of the paleoclimate of the region. Maximum species diversity and density was found within sample interval number 4 from the upper part of the organ ic-rich silt unit. Simple species diversity, as number of taxa per sample interval, is illustrated in figure 9. YI Table 2 Taxonomic list of the co!eopteran fauna from Athens North Quarry site, Illinois. Order of genera tollows Arnett (1968). Order of species in the Carabidae and the Scolytidae follows that of Lindroth (1961, 1963, 1966, 1968, 1969) and Wood (1982), respectively. Taxa Skeletal Distribution elements 1 group2 Carabidae Sphaeroderus nitidicollis ---i3revoorti Lee. LR C Dyschirius integer Lee. PLR Dyschir~ A sp:--~ PLR Patrobus sp. H Bembidion morulum Lee. HPLR A Bembidion cf. morulum Lee. H L Bembidion sp. ~~- HPL Pterostichus patrue!is DeJ. p A Pterostichus sp. H L Diplocheila sp. p Chlaenius alternatus Horn p A Gen. indet·. HPLR Dytiscidae Hydropor1n1 gen. 1ndet. HPLR Ilybius sp. PLR Agabiini gen. indet. HPLR Gen. indet. HPLR Hydrophilidae Gen. indet. HP Hydraenidae _!Iydraena sp. LR Staphylinidae Bledius sp. p Eucnecosum brunnescens J. Sahlb. p A Eucnecosum tenue (Lee.) or brachypterum (Grav.). p Eucnecosum spp. HPLR Olophrum rotundicolle (C. Sahlb.) HPLR A Olophrum spp. LR Acidota crenata (Fab.J HP A* Pycnoglypta ~ptera Cpbl. HPLR Omaliinae gen. indet. PLR Stenus spp. HPLR Euaesthetus sp. HP cl::-Pnilonthus sp. LR - -·· ------. 38 Table 2--Continued Taxa Skeletal Distribution elements group Quedius (Raphirus) sp. HP Tachinus sp-.---- p Gymnusa sp. HP Aleocharinae gen. indet. P R Gen. indet. p Pselaphidae Reichenbachia sp. H LR Silphidae Thanatophilus sagax Mann. p u Leiodidae Agathidium sp. LR Scydmaenidae Gen. indet. LR Scarabaeidae Aegialia sp. R Aphodius sp. PLR Helodidae Cyphon or Paracyphon sp. R Gen. indet. p Byrrhidae Cytilus sp. PL Elateridae Hypolithus bicolor (Esch.) p u Cucujidae Narthecius sp. LR Chrysomelidae Donacia sp. R ct. Phaedon sp. LR Curculionidae sftona sp. H Hylobius sp. PLR Notaris sp. HPLR Erirhin1n1 gen. indet. H Magdalis sp. PLR Ceutorhynchini gen. indet. LR Gen. indet. HPLR 39 Table 2--Cont1nued Taxa Skeletal Distribution elements group scolytidae Phloeotribus ~E?~ sw. R A Carphoborus carr1 Sw. R A c'arpnoborus cf. carri Sw. L Polygraphus rufipennis (Kby.) LR A* Scolytus cf. p1ceae Sw. R Scolytus sp. LR Ips latidens (Lee.) L B* Pityophtfiorus cf. nitidus Mann. LR Pityophthorus sp. PLR cf. Pityophthorus sp. HPLR Gen. indet. H R 1 Skeletal elements: H head; P -- pronotum; L -- lett elytron; R right elytron. 2 Distribution groups: A -- generally northern, trans american, may also occur in the Rocky Mountains as tar south as ·colorado; B -- generally northern, trans american,but not north of so• N; C -- eastern; D - northwestern; A* and B* indicate groups whose d1str1- butions are comparable to those of A and B respectively, but the southern limits extend into southern United States; U -- distribution unknown. 40 Table J Total numbers of coleopter~n indiv1dugls of edCh tdxon per sample interval, At.hens North Quarry, Ill1no:ui. '?'ax.a sample intervals ------· t l 4 6 7 8 • 10 1t 12 tJ ------~-· ·---·------" CARABIDAE Sphaerode O'iT I SC l DA"£ Hydroporini gen. indet. ) ) ) I lXbius •P• ) 'l 2 l Agabuni. gen. indet. 2 l 7' l l 4 Gen. i.ndet:.. l 1 ' HYOROPHILI0AE Gen. indet. HYDRAENIOAE Hydrae~ sp. STAPHYllN!DAE Bledius sp. Eu'c'n"ecci sum brunnescens 2 5 J, sahlb. Eucnecosum tenue !Lee.) or · ~rachyote~um (Crav.} Eucnecosum spp. 5 OL:>enrum r-ot:undicolle 4 2 9 l jC, Sahlb, l Olo£ht:um spp, Ac1dota crenata (Fab.J ~OSilY:~td aptera Cpbl. l Omal11nae qen. ~net. 4 4 l 5 2 Stenus spp. l l 4 ] l 4 5 itu.i'esthetus sp. 2 5 2 ' ' ct~1lonthu-s sp. l Ouedius !Raeh:i.rusJ sp. ~h~sp. Gymnu~ ~P· 1 Aleccnarinae gen. irtdet. l 1 Cen. indet. FSELAPHIOAE Rekhenbdchia sp. 2 ' S [ :..?H!OAE ~~atop~~ §~ Mann. LE roe tDAE A5ath:.di.'J!:1: sp . ., .3C:YJ14AENtOAC c~n. tndet. 2 SCAR.'l.BAE I DAE Aegi.at!J! S\'.L ~~ Sp. 41 Table l--Continu~d : 2 6 ;u::.ooroA£ .9:.?hon or Pas_~~.D sp. G;;;n. 111det. f!YR! ELATERrDA£ Hynotitnus ~Le.£ {E1,,ctt.J CUCUJtDAE ~arthecius sp. CHRYS0M£L IC·A.E P~:.! sp. ct. ?taectot\ sp. O:tJRCt::LIONIDAE ~SP, :rylcbius sp, Notc'lrts sp. ~r1r~in1n1 gen. 1::d~t. 'tc:!-1:da_l~ Sp, 2 .:"""utcrh~·nch1n1 gen. :_ndet. -:;~n. ~ncet .. ;' SCGLYT!OAE ?~:oe~tr:buu occBae Sw. ,::,,~·onc~orua car-t! Sw. ::.:.r,mob::>r:.is ct". :arti. S;.,·, Poi•tqrapnus r-ufl~s !KDy. l Sc::d•1e.c:s ct. pL::eaoe 3,..;. Seo l'tt.us sp. 1£! ~dens IL.ac:.J 7 J l ?tZYO!'ht').'.J(US cf. :'.i:..Ldu.s )l!ann. ~:o r: nor:us so. c::. 1' o~o.r::s 5p. C,;,r.. ;; .,;c. 2 !2 42 PLATE I Fossil Coleoptera from the Athens North Quarry and Biggsville sites. Bar scale represents 100 micronsr anterior is up in all cases. Numbers refer to North Dakota State University Geology Department accession numbers. a. Pycnoglypta aptera, head, dorsal view, xlOO (ANQ 04-11-03). b. Pterostichus patruelis, pronotum, x33 (BGV 10-02-08). c. Olophrum consimile, pronotum, x50 (BGV 10-21-08). d. Polygraphus rutipennis, left elytron, X50 (ANQ 12-07-03). e. Olophrum rotundicolle, pronotum, x50 (BGV 13-09-04). f. Carphoborus andersoni, right elytron, x75 (BGV 14-03-03). g. Carphoborus carri, right elytron, x75 (ANQ 06-07-03) • h. corraded pronotum of Bembidion sp., characteristics of corrasion include pitting and thinning of the chitin, xlUO (ANQ 12-04-06). i. Bembidion morulum, pronotum, xlOO {ANQ 07-05-02). PLATE I I I 44 Sample Interval 1 2 \ 3 ~ 4 4 > 5 ,( ,... 6 , .....e 7 f .c: ,5 8 ; Q. -a, 9 \ 0 10 ; 1 1 I 12 ~ 13 6 14 10 20 30 40 50 Number of coleopteran taxa - .. - Number of aquatic tax a Figure 9. Species diversity and numbers of aquatic tax a, A U1c,1;s North Quarry site, Illinois. ------·····-- 45 A trellis diagram (Figure 10) based upon calculations of Jaccard coefficients of similarity illustrates the degree ot similarity between the beetle assemblages ot pairs ot sample intervals. Each square in the matrix repre sents the comparison of two sample intervals which are numbered along the diagonal. Possible values tor coeffi cients range trom O.O, for complete dissimilarity, to 1.0, for identity. Each coefficient in this sequence has a value of less than 0.7. The patterns which represent the degree of similarity become progressively denser as the value of the coefficient increases. Thus, the darker areas in the trellis diagram mark the faunally related groups of intervals. Intervals 2 through 10 form a large similarity group, and intervals 11 through 14 form a group ot mutually dissimilar intervals. The dendrogram (Figure 11), generated by the applica tion ot the weighted pair-group method to the similarity coefficients, shows the order of clustering of the sample intervals. Intervals 2 through 10 form a large cluster to which intervals 11 through 14 are added one at a time, being no more similar to each other than they are to the major cluster. These dissimilar intervals were grouped into faunal zone A-1. The intervals comprising the large cluster were designated faunal zone A-2. Sample interval number 1, which was not included in the statistical analy sis, is designated as fauna! zone A-3. The faunal zones 46 Jaccard similarity coefficients {!] 0.6-0.7 A-3 I!] 0.5-0.6 [!] 0.4-0.5 ., 0 0 & T 0 • 6 4l A-2 0 0 = (9 @ 0.3-0.4 ...0 0 •O 0 0 0 0 (9 0 & GI 9 @] 0.2-0.3 C 0 . 0 (9 (9 (9 ::J • 10 J_ t, ,1: Figure 10. Trellis diagram of Jaccard similarity coefficients showing faunal zones, Athens North Quarry site, Illinois. 47 1.0 I ..... 0.9 . C: I .. 0.8 I .!:! I I • -.. 0.7 l 0 Q - !l," >, 0.6 -- ;:- !'! 0.5 § .. 0.4 "O - ...m (.) 0.3 . -- (.) ..,m 0.2 0.1 . ii' 2 10 3 4 5 6 7 8 9 13 12 14 11 Sample intervals ,, J Figure 11. Clustering of sample intervals Athens North Quarry site, Illinois. 48 are illustrated in figure 10. The percentage of corraded fossils for each interval in the Athens North Quarry site is plotted against interval depth in figure 8. The highest percentages occur in inter vals 13 and 12, corresponding to the mµck unit and the lowermost part of the organic silt unit. Sample interval number 1 yielded 6 juvenile gastro ...,' ... pods. These were identified by A. M. Cvancara as terres trial snails, probably belonging to the family Succineidae (Cvancara, oral communication, 1984). Biggsville site At least l,395 coleopteran individuals, representing 25 families, have been identified from the Biggsville site. A total of 114 taxa was identified to the family level or lower, including 26 identified to species. Of the total, 31 percent was classified as aquatic according to the criteria established by Leech and Chandler (1971). A sum mary of the fauna! data is found in table 9 of appendix A. A taxonomic list of the beetle fauna, including designation of aquatic taxa is presented in table 4. A quantitative summary of the insect taxa and their numbers per sample is given in table 5. Scanning electron photomicrographs of several fossil 49 Table 4 Taxono~ic list at the coleopteran fauna tram the Biggsville site, Illinois. Order of genera tallows Arnett (1968). Or~er at species in the Carabidae, M1cropepl1dae, and scolyti~ae follows that of Lindroth (1961, 1963, 1966, 1968, 1969), \Campbell (1968), and Wood (1982), respectively. Taxa Skeletal Distribution elements' group1. Carabidae I Notio hi lu!s sp. R l:ffet isa s • H Elaphius a.ericanus Dej. or ripariusbL. HP R Elapnruss • H Dyi;-cEirTus \ ..t!m!_dus Lth. HPLR A Dyschirius,sp. HPLR Patrobus Sf· HPL Bembidion sp. (planiusculum grp.) p Bemb1:~:ion Table 4--continued Taxa Skeletal Distribution elements group _Ilybius sl. HPLR Agabiini 9en. indet. HPLR cf. Rhantu.s sp. L Col mbete sp. L Gen. inde. PLR Hydrophilidii!e Helophoru' sp HPLR Hydrochus sp. P R Hydrobius fuscipes L. LR u Hydrobius:sp. R Cercyon sp. LR Gen. indef. HPLR Hydraenidae1 Ochthebiu$ sp. H LR Hydraena fP· HPLR Gen. indef. R I Staphylinid Table 4--continued Taxa Skeletal Distribution elements group Pselaphidai Reichenbachia sp. HPLR Silphidae i Thanatop~ilus sp. HP I Leptodirid I Scarabaeida'f Aegialia $p. LR Aphodius sp. H LR Aphodiini[gen. indet. H L Gen. indett. H HeloC!idae \ Gen. inde~. p i Byrrhidae I Cytilus sp'. HPLR Gen. indet\· H L Heteroceridaf' Gen. indetj. PL Elmidae ·1 Dubiraphia.sp. p Cantharidae \ Gen.· indet 1 p Nitidulidae Gen. indet L Cucujidae Narthecius 'sp. --~------·-- I R Gen. indet.\ R 52 Table 4--Continued Taxa Skeletal Distribution elements group cryptophagidae Anchicera ephippiata Zimm. L B coccinellidae Nephus ornatu~ naviculatus (Csy. l R A* Lathridiidae ct. Corticaria sp. PLR Chrysomelidae Macroplea sp. H LR D0nac1a sp. LR Plateumaris_ sp. LR ct. Al1=i_~ sp. p Curculionidae Lepidophorus sp. H Sitonini gen. indet. HP Dorytomus sp. LR Grypus~sp. . R Notaris aethiops F. H LR A Notaris sp. H &1.·r11Inini gen. indet. HPL Bagous sp. PL Magdalis sp. R ct. Magdalis sp. L Hypol_<=~schtis-sp. L Ceutorhynchus sp. p Ceutorhynchini gen. indet. R Cryptorhynchini gen. indet. R Gen. indet. HPLR Scolytidae Hylesinus sp. R Phloeotribus piceae Sw. R A Carphoborus andersoni sw. LR D Carphoboru~ carri Sw. R A Polygraphus rufipennis (Kby.) H LR A* Polygraphus sp. L Scolytus sp. LR Orthotomicus caelatus (Eich.) L A* ~ borealis Sw. R A Crypturgus borealis Sw. PLR A* Pithophthorus sp. HPLR ct. Pithophthorus sp. p 53 1 Skeletal elements: H head; P -- pronotumi L -- left elytron1 R right elytron ~Distribution groups: A -- generally northern, trans american, may also occur in the Rocky Mountains as far south as Colorado; B -- generally northern, trans american, but not north of 50° N1 C -- eastern, D - northwestern, A* and B* indicate groups whose distri butions are comparable to those of A and B, respectively, but the southern limits extend into southern United States; (Ul distribution unknown. Table 5 Total nu/l'bers of coleoptecut indt7tdqals of ea.ct\ ta~on per sample interval, Siqgsv1l\e, Ill1ncis. Tax.a 5&.mp!~ tnter,,al::. 1 2 J 4 5 n 7 a 9 10 11 12 13 14 1s 16 11 1a l9 20 21 22 CAI.U;lHDAE Notiophi lus sp. Bleth~- sp. Elaphrus americ.arrns Oej, o, nearius L. Elap(1.r:.!.! Sp Dysch1rius timidus Llh. 7 5 5~sctunus :s:p. 1 1 1 J l 2 l 3 1 1 3 1 2 Paaoous sp. 1 1 l l 1 Bembid1on sp. ' ~iusculum grp.} Bemb{dion cf. nigr1pes Kby. l Bemhtdion sp. (dorsa. le grp.) l 1 Bem~ cf, ~!!>. Hay. 2 Bembtdton :,p. (verucolor qrp. I Bemb1d1on morulom Lee. l l 2 V' Bembidion er, morulum Lee. 1 .,, '13emb1d1on sp. lmus1co-la grp.! I Ben'lb1aiori transparens GebL 2 l 7 l J Bemb1dton ~ranspatens Gebl. l ' 1 Bembtd100 concretum Csy. 1 Bemb1d1on forte;str1-atum Mb1. 1 6 l 7 l 11 J Semo1dion ct. fortestrtdtum Ml3. ' ' l ' l 1 ' Bemb1dion pseudo~al,tum Lth. ' 2 eemb1dion front.ale Lth, Bemb1.:.hon ~(~f:S_uliferum g:rp.J 7 Bemhtdlon spp. l 1 1 l 1 l l 10 l 2 l 2 2 J 5 Pterost1chus pensvlvarncus Lee. 1 or adstncrus t:"sch. Pterost1ch':!.:! p,.,1uuelis Oo?j. 2 2 t l Pterostlc~us cf. oatru~Ji~ De), 2 2 Pterc1t1chus spp. l 2 I l 1 l t 2 Agonum sp.'"('me 1,mar i 11m q:.:p.) Aqonum corvws"'l:eC:---- ~:7oni1~ ct. decentis Say A~onum spp. 1 1 2 UieToCh~lJ~ sp. Chlaz,r,iqs sr:,, Gen 1 nder, l 1 l l 1 1 t l l 1 l 0\11' l S1~ I D/1£ B1de1;5:;n1 :ien, indet. 1 l l!ydrc.p'..•r;:u q""n" u;det. ' l l ' l l l ,. th. ' Table 5--Continued Sample intervals Taxa 9 10 ll 12 13 14 15 16 17 18 19 20 21 22 2 3 ' s 6 ] a 3 l l l 3 l l l l l 2 l 2 l l Ilybiu~ sp. 1 1 l 1 l AgabiLn1 gen. indet~ l 1 l l cf. Rhantus sp. 1 ) 2 2 Collinbetes sp. l l Coen. 1ndeL 7 5 5 1 3 4 7 3 HYDROPHILIDA£ l l 1 • • Heloehorus sp. ' l Hydr(?chus sp. ' 1 Hydrob1us fuscipes L. 1 1 1 Hydro61us sp. 1 1 2 1 l 3 I 4 4 1:ercyoo sp, 11 s 2 • 8 2 • Gen. iodet. l l l l 6 25 14 18 8 H'fOFA.ENIDi\t 8 21 18 23 15 54 11 1S Ochthebios sp. J 4 1 Hydraena sp. l U1 Gen. 1ndet, U1 l 2 l STA.PHYLINlDAE car:eelimus sp, c!. careeiimus sp. cf. Platysteth~s sp. l tHedius sp. Eucnecosum brunnescens J, Sahlb. 1 l Eucnecosum tenue Lee. or 2 3 5 23 l l 2 hrachypterum Grav. l 7 20 6 21 17 l 2 l 2 l Eucnecosum spp. l 3 13 2 5 l l 2 10 11 'll 2 4 l ' olophrum consirnile (Gyll.i 2 l 2 24 ' 1 4 l l 61o~hrum rotund1colle l l ; l l l - ( • SahlP. • l ' l Olophrum spp. l Pseeh 1dom1s sp. 3 2 3 2 6 2 l 2 • cf. Pycnoglypta sp. 2 l 4 J 2 7 S 11 5 l 4191413 7 4 10 • 17 •5 Oma l i inae gen. l ndet. l 4 2 13 4 2 6 l 6 l l l ' 3 5 2 6 l 17 • 2 ~~ spp. 1 l 3 l l 3 l Euaesthetus sp. 2 2 ' Ct.Phi lonthus sp. 2 1 Brzoeorus sp. l l Ti;1,ch1nus sp. l l 2 5 TaChyporin~e gen. indet.• l 2 2 J 2 1 2 l I l 2 2 l l l 3 1 G'fmnusa :;p. l 2 l 1 l 2 A. ~0Cti"~r1nae gen. 1.ndet. 2 ' " ' Gen. ind et.. ' ~ ___ _,,' Tabte s--~~1:1nued raxa Sample 1.ntervals 2 3 ' s ' 7 8 9 10 11 12 13 " 151b1118 192021?2 MfCROPEPLlDAE ~icropeplus tesserula Curtis Micropeplus sculptus Lee, 1 2 ~1cropeplus cr1bratus Lee. 2 PSELAPHIDAE Reichenbachia sp. 1 ' 2 4 28 8 • l l 2 2 51 LPHIOAE Thanatophilus sp. LEPTODIRI.DAE Catops sp. 2 L£10D10AE H~dnobius sp. l As;ieth1dium sp. 1 2 5 14 l 2 l 3 l t J Gen.a.ndet, l ' en SCYDMAEN I DAE Gen. indeL l l 3 °' Hl5TER1DA.E ,,en, indet. SC'.ARMH,EIDAE A~11/l11a sp. ru?hclh us sp. l I l 1 1 T\Phod1 ini gen. indet.. l 2 Gen. 1ndet. HELODIDA.E Gen. 1 ndet. ' 7 ' ' l ' B'lRRH!DA.E Cyt1.lus sp. l 2 Gen. indet. l ' 2 ' HETf.ROCEFlIDAE Gen. H,det. 2 EV-1!:iAE i)u:::1:aoh1a sp. 1 l :: kWriu, Rt DAE :;,..:n. i r,cet. ,ck,.tL ..... •,> Tabie S--Continueq T21xa Sdmplc •ntervals 2 5 6 7 a 9 10 11 12 13 14 15 16 17 18 19 ;,'O 21 22 ------NIT IDUL lDAE. Gen. rndat. CUCUJ!DAE Nart.hecius sp. Gen. tndet. CR'lPTOPttAG ! DAE ~D~ ephipp121t21 Z1mm. COCCINELL!OAE Nephus ornatus nav1cuiam-1csy.} {.A'I'HRIDI IOAE cf. Corticat CHR'lSOHE.I,IOAE Macrcplea sp. Donac ia sp. J ' U1 Flateumaris sp. 4 3 8 4 .-J rr.--nt tea $p. DonacITna'e gen. indet. 2 2 3 3 CU!tCiJLlONIDAE ~pi do_E.Q£!.:.:i_!! sp. Sttonin1 gen. indet. , Dorytomus sp. 2 '!rn~.~ sp. ~;..! ~__E.hiops r. Notari$ Sf', Enrn1nin1 gen. indet. Ba9ous sp. ~dal1._~ sp. cf. ~aqd~:!_ sp. !:!.z:poles;;~ sp. Ceutorhvnchus sp. l Ccutorhynchini gen. indet, Cryptorhynchint gen. indet. Gen. indeL 2 12 6 1 Sw. Sw, ' ·rctble 5--Cont_~[\!lt!d 'l'axa Sample 1ntetV6ls 1 2 l 4 5 6 7 8 9 10 11 12 B 14 15 16 17 18 19 2CJ 21 22 Cdrphoborus carr1 Sw~ Polygr6phus rufi'eemnu i Kby. J Potygr6phus sp. 1 Scr.>lytus sp. 3 l 2 1 Orthotomicus cael~tus tE1ch,l 1 ~ boreall_! Sw~- 1 Crypturqus bore~lis Sw~ 4 P1tyoehthorus sp. 2 l 2 l l l l 2 cf. P1tyophthorus sp. 5 l en 0:, 59 species tram Biggsville are presented in plates I and II. The named species are assigned to distribution groups in table 4. The distribution groups of the species from the Biggsville site will be described and illustrated along with those from the Athens North Quarry site in the discus sion ot the climate in the region. Maximum species diversity occurs in intervals numbered 19 and 20 in the organic silty loam unit. Maximum species density occurs in interval number 10 in the peat unit. Minimum species diversity occurs in interval number 5 of the basal loess paleosol. Simple species diversity tor each sample is illustrated in figure 12. A trellis diagram {Figure 13) of similarity coef ficients shows two main areas with denser patterns. Inter ., . vals 1 through 4 form a small group, and intervals 5 through 21 form a much larger group of intervals with similar beetle assemblages. Interval 22 shows little similarity with any other unit, with similarity coetticient values of less than 0.1. The dendrogram (Figure 14) reflects the same division of intervals. Intervals 5 through 22 are designated faunal zone B-1, and interval numbers 1 through 4 are included in taunal zone B-2 (Figure 13) • 60 PLATE II Fossil Coleoptera from the Biggsville site. Bar scale represents 100 microns: anterior is up in < ... all cases. Numbers refer to North Dakota State University Geology Department accession numbers. a. Bembidion frontale, pronotum, xlOO (BGV 20-01-09). b. Micropeplus sculptus, right elytron, xlOO {BGV 18-04-03). c. _Micropeplus .tesserula, right elytron, xlOO {BGV 11-02-01). d-f. Dyschirius timidus d. head, dorsal view, xlOO (BGV 10-03-13). e. pronotum, xlOO (BGV 10-03-14). f. right elytron, x55 (BGV 10-03-09). g-h. Micropeplus cribratus g. pronotum, xlOO {BGV 22-01-01) h. right elytron, xlOO (BGV 22-01-02). i. Bembidion fortestriatum, pronotum, xlOO {BGV 15-12-06). j. Bembidion transparens, pronotum, xlOO (BGV 15-12-02). D r :n::mrrrrr: ·nwmwr·w·· mm PLATE II I I C I , I h 62 Sample interval 1 2 'I 3 't 4 5 5 .6 T 7 t 8 ) 9 ( ,.... e 10 ' > ' -.c... 1 1 '( Q. 12 Q) .-)<, 0 13 ;' 14 t 15 '\ lo 6 16 I 17 ; 18 + 19 ~ 20 ' ) 21 ( " 22 ' ... 10 20 30 40 50 Number of coleopteran taxa - .. - Number of aquatic taxa Figure 12. Species diversity and number of aquatic taxa, Biggsville site, Illinois. 63 1 >-- T () 2 Jaccard similarity coeffic ients B-2 0 • 3 (S) 0 © 4 [!] o. 5-0.6 . . 5 . . . 6 0 0 ~ o . 4-0.5 • . . . 0 © 7 a 0 . 0 0 0 [§] o. 3-0.4 9 .. 0 . . . 0 •0 0• () II> C: . . . . () () 10 0 0 0 @] o . 2-0.3 N 0 . . . ·0 () () () () 11 . 0 . . 0 () () 0 () 12 1-0.2 "'C: D o. " B-1 . 0 © 0 0 () ()• () 0 () 13 II. . () () 14 "' 0 . & () & () () 0 0.0-0.1 . . . 0 () 0 0 0 IS)• 0 & 15 0 . . . . 0 0 0 0 () 0 () () •0 0 16 . . . 0 0 & 0 0 0 0 () 6) (9 0 17 18 . . . • 0 0 0 0 (;) 0 0 0 & 0 () (9 ,-;" 19 . . . . . 0 0 & 0 0 () 0 & () () () i$) () . . . . 0 . 0 . ·O 0 ·O . 20 21 . . 0 0 0 0 0 0 0 0 0 0 0 0 0 (9 (9 I 22 Figure 13. Trellis diagram of Jaccard similarity coefficients showing faunal zones, Biggsville site, Illinois. 1.0 0.1 . 1 2 3 4 5 6 8 9 12 13 10 7 11 14 15 16 19 18 17 21 20 22 Sample Intervals Figure 14. Clustering of sample intervals, Biggsville site, IllJnois. DISCUSSION Paleoenvironmental interpretations of the Athens North Quarry and Biggsville sites are made to describe the local environment that existed at each site and to infer the climate of the region. A sequence of events is pro posed for each site. Paleoenvironmental and paleoclimatic inferences are based principally upon knowledge of the habitat preferences and geographic distributions of extant species of beetles that are represented as fossils. These data are supple mented by data from sedimentological and taphonomic studies and from previously published paleontological and palyno logical studies. General knowledge of beetle habitat pref erences was gained from Arnett (1968), Blatchley and Leng (1916), Dillon and Dillon (1961), Doyen and Ulrich (1978), Leech and Chandler (1971), Moore and Legner (1979), and White (1983), and from conversations with entomologists. To avoid excessive repetition, general habitat data derived from these sources is not cited in the text. The sources of specific habitat information, however, are indicated. Local Environment at the Athens North Quarry Site The Athens North Quarry sequence is divided into three faunal zones (Figure 10). Zone A-1 includes sample inter vals 11 through 14. Zone A-2 comprises sample intervals 2 65 66 Interval number 1 is assigned to zone A-3. through 10. zone A-1 Faunal zone A-1 is defined on the presence of a total of 58 beetle individuals belonging to at least 19 taxa. Beetles from this zone are represented by species of aquatic, hygrophilous, forest and miscellaneous habitats. In general, though, zone A-1 is characterized by low spe cies diversity and density in which hygrophilous species ' ' dominate. "-'(\ The aquatic element of this zone is represented by one individual of the dytiscid tribe Agabiini. Members of this tribe are generally found in temporary pools or marshy areas. The modern counterparts of the majority of the taxa of zone A-1 are hygrophilous, occupying moist terrestrial habitats. The carabid genus Qyschirius burrows in moist soil with sparse or no vegetation, usually near water (Lindroth, 1961, p.132). Most species of ~emb~dion inhabit water-marginal areas. Pterostichus patruelis is a very eurytopic swamp species, occurring in Sphagnum bogs, as well as more or less eutrophic Carex mires (Lindroth, 1966, p. 505). The rove beetle species of zone A-1 commonly inhabit 67 moist organic habitats. Species of Eucnecosum dwell in leaf litter under shrubs. as well as among sedges. Olophrum rotundicolle lives in wet mosses and sedges in pond marginal habitats (Ashworth, 1980, p. 209). Species of Stenus are usually found in wet situations such as bogs, moist meadows, and marshes. The weevil genus Notaris and members of the minute seed weevil tribe Ceutorhynchini are also common in pond-marginal situations, feeding on sedges and other types of vascular hydrophytes. The presence of coniferous trees in the area during the deposition of zone A-1 is indicated by several tree inhabiting species. The weevil Hylobius is known to feed on and live beneath the bark of Pinus (Blatchley and Leng, 1916, p. 186). Hosts of the scolytids Carphoborus and Polygraphus rufipennis include Picea, Abies, Pinus, and other conifers (Wood, 1982, p. 369-374, 389). Several species in zone A-1 represent other terres trial habitats: the ?ill beetle Cytilus is often found inhabiting mosses; dry sandy areas near water are indicated by the presence of the scarab Aegialia. Phytophagous chry somelids and weevils are also present. ~or example, Sitona is often found on plants in open areas. Zone A-2 Fifty taxa, including a total of 226 individuals, were 68 identified from zone A-2. The number of identified indi viduals per kilogram and the average number of taxa present per interval in zone A-2 are approximately double that of A-1 (Table 7, Appendix A). All but five species of the 27 taxa identified from zone A-1 are also present in A-2. Similar to zone A-1, the beetle species of zone A-2 are predominantly representative of aquatic, hygrophilous and forest habitats. Also present are inhabitants of several miscellaneous habitats. Compared to zone A-1, this zone is generally characterized by higher species diversity and density, an increase in the aquatic component, but con tinued dominance by hygrophilous species. The aquatic fauna, represented by five families, shows an increase in diversity from that of zone A-1. Members of the family Hydrophilidae, like the Dytiscidae, are commonly found swimming in shallow weedy ponds. The hydraenid Hydraen~ is closely related to the hydrophilids but cannot swim. Most species of Hydraena are found crawling in moist matted vegetation, The chrysomelid beetle Donacia and species within the Helodidae inhabit thick growths of sedges and emergent vegetation. The fauna of zone A-2, like that of A-1, is dominated by hygrophilous forms. Taxa common to both zones include the ground beetles Dyschirius, Bembidion, Pterostichus £>_atruelis, the rove beetl.es, two species of Eucnecosum, 69 Ologhrum rotundicolle, Stenus, and curculionids of the I tri~e Ceutorhynchini. The species Dyschirius integer bur- rows in moist clayey soil at the margins of fresh water I' wheteI the vegetation is depressed and the ground is bare in spots (Lindroth, 1969, p. 149). Bembidion morulum has been I obs4rved on moist peaty soil in coastal tundra and inhab- I iti~g pond-marginal sedges (Lindroth, 1963, p. 389). Most I spe~ies of Diplocheila occur near stagnant freshwater with dense vegetation (Lindroth, 1969, p. 939). Similarly, I ' Chlfenius alternatus has been found among sedges, grasses, " mos$es, and other water-marginal plants (Lindroth, 1969, p. 992) • I I Species of the staphylinid Bledius commonly occur togbther with species of the carabid Dyschirius (Lindroth, 196~, p. 132). Bledius also burrows into moist sand or I mud!. The rove beetles Acidota crenata and Pycnoglypta often occur with Olophrum and other staphylinids of the 1 su9family Omaliinae in wet areas with sedges, grasses, moss tus1 socks, accumulations of plant debris, and willow shrubs. Sp~cies of the staphylinid Gymnusa are also associated with swaimps, swampy places beside ponds and lakes, and bogs (K~imaszewski, 1979, p. 14). Weevils of the tribe I I Erfrhinini are marsh dwellers: many of the larvae feed on aqtjatic plants and the adults are often found near open i water. 70 Forest-dwelling species increase in numbers and di- , \iersity in zone A-2 • .!£§_ latidens is known (Bright, 1976, ~· 152) to inhabit shaded-out or broken limbs of Pinus, T•uga canadensis (hemlock), and Pseudotsuga menziesii I 1pouglas fir). The habitats of other scolytids of this zbne were described by Wood (1982). Hosts of Carphoborus c~rri include Picea engelmannii (Engelmann spruce), Picea I giauca (white spruce), and Picea rubens (red spruce). I , Pfloeotribus piceae prefers the shaded-out branches of ' I•, ':,1' l~rge living Picea glauca trees. Polygraphus rufipennis I uJually lives in dead or dying spruce, but is known to o~cur in Abies and Pinus. Pityophthorus and Scolytus are ' fdund in both coniferous and broad-leafed trees. Bright (~976, p. 179) noted that Pithyophthorus prefers dead or d~ing twigs or small branches. Several other taxa, present in zbne A-2, also indicate th~ presence of a forest. The cucujid beetles, such as Narthecius, live under bark of trees. Members of the click ' beltle family, Elateridae, are found on the foliage of trtes and bushes as well as in rotten tree trunks. The pi~e-feeding weevil Hylobius is present in this zone, as is MaQdalis, a weevil which feeds in broken branches of dead or ldying conifers or deciduous trees. The ground beetle, ~~roderus nitidicollis brevoorti lives on the forest flgor, preferring moist places with mosses and dead leaves, corrimonly near water (Lindroth, 1961, p. 29). 1 71 Other beetle species from zone A-2 represent miscel la~eous habitats, several of which may also be related to th~ forest floor. Members of the rove beetle genera QufdiusI and Tachinus are generally found in moss, leaf liltter, debris and decaying organic material (Smetana, 1971, p. 6; Moore and Legner, 1979, p. 270). The leiodid Agathidium is known to inhabit fungi and slime molds on decaying vegetation or under the bark of trees. Some mem bers of the family Scydmaenidae and the pselaphid genus Reichenbachia are reported (Grigarick and Schuster, 1967, p. 1) to live together with ants. Others inhabit leaf '" mold, leaf litter and moss, or live under bark, logs, or stones. The byrrhid Cytilus commonly lives in moss. The scarab Aphodius is usually found in dung but also dwells in fungi and beneath leaves and logs. Carrion beetles such as • :1 Thanatophilus sagax commonly feed on carrion. Zone A-3 This fauna! zone is composed solely of interval number 1, which contains no beetle fossils and therefore is not included in similarity and cluster calculations. It does however contain several gastropods. Unfortunately, the individuals are juveniles and therefore very difficult to identify with certainty. They probably belong to the ter restrial gastropod family Succineidae (Cvancara, oral communication, 1984). Most terrestrial snails in this region require a soil cover of moist organic debris in 72 which to reproduce. Both eggs and immature snails are highly susceptible to drying and to the effects of direct sunlight. In addition, most common terrestrial gastropods depend on decaying organic matter and fungi for food (Leonard and Frye, 1954, p. 400). Therefore, the occur rence of these snails in zone A-3 indicates the presence of a moist organic habitat. Sedimentology and taphonomy . ,,• Additional clue~ concerning the character of the local , environment were gathered from the characteristics of the sediment. The relationship of the sample intervals to the lithologic units and faunal zones at the Athens North Quarry site are shown in figure 15. Intervals 13 and 14 of zone A-1 are within the muck unit, which represents a : ii period of pedogenesis (Follmer et~., 1979). The over lying two intervals of zone A-1 and all of zone A-2 are included in the organic-rich silt unit of the Peoria Loess. Zone A-3 (interval number 1) belongs to the inorganic silt unit of the Peoria Loess. The degree of corrasion of the beetle fossils also provided information about the environment at the Athens North Quarry site. The highest proportions of corraded beetle fragments are found in sample intervals 12 (54%) and . . 13 (49%) of zone A-1 (Figure 8). Characteristics of these fragments include pitting and thinning of the chitin frag- .. ATHENS NORTH QUARRY BIGGSVILLE -Ill .c...... > .c... ,_ "'...> c. E G) c. E Ill G) ...... Lithology ... Fauna! G> .... Lithology ... Fauna I Q .!: zones C C: zones --- . 1 Inorganic slit 1 A-3 2 T s B-2 2 loess paleosol 4 5 3 ~4- ~5 e organic silly loam 7 4 8 , e 5 10 s A-2 11 organic silt peat 12 B-1 13 7 w 14 "" 15 8 ~s- '--5- 18 17 9 silty peat 18 19 10 20 organic silty loam 21 11 22 organic sandy loam 12 A-1 ~a- muck 13 -1- gravel clavey silt · 14 l Figure 15. Sample intervals, lithology and fauna! zones of the Athens North Quarry and Biggsville sites, Illinois. ~;;,. ~· ~ - ;- "~'. 74 ments (Plate re). Although chemical alteration of chitin by the leaching of lipids may also cause post-mortem pitting, the pitting and thinning of the fossils may be predomi nantly the result of microbial degradation of the chitin in the soil. According to Atlas and Bartha (1981), chitin in the soil is subject to attack by various fungi and bac teria, including actinomycetes. The role of actinomycetes in the degradation of complex organic substrates such as chitin was discussed by Lacy (1973). These bacteria are widespread in all soils. Their numbers and importance are dependent upon the soil type, depth, moisture, aeration, pH and organic matter content. Soil moisture and pH appear to be the most important factors. Most soil actinomycetes are aerobic and prefer neutral or slightly alkaline soils. The preservation of chitin in an aerated soil occurs when the degradation process is inhibited by protective layers of wax and protein on the chitin fragments. Lacy also pointed out that there are generally few actinomycetes in acidic peaty soils, especially if they are water-logged. Pollen and plant macrofossils J.E. King (1979) described the palynology of the Athens North Quarry site, and F. 8. King (1979), the plant macrofossils. Pollen samples were studied from a SO-cm thick section from the lower organic-rich part of the . ' Peoria Loess, dating between about 25,000 and 23,000 14c yr 8.P. The dominant taxa, which comprised about 70 percent 75 of the total upland flora, were Picea and Pinus. Other common taxa throughout the section were Quercus (oak), Graminae (grasses) and Tubuliflora (the sunflower group)• Components which were present only in the lower part of the section include lix (willow), and Morus (mulberry). J.E. King interpreted the pollen as repre sentative of a forest composed of pine and spruce with a grass and herb understory. Occasional oak trees may also have grown in the area, or their pollen grains may have been transported in by prevailing winds from source areas '' . to the southwest. Although the disappearance upward of birch, willow, and mulberry might imply a shift to a slightly colder climate, the pollen from this site did not suggest any type of major climatic change during this period. F. B. King (1979) examined collections of plant macro fossils from a bulk sample of the organic-rich zone of the Peoria Loess, dating between about 25,000 and 22,000 1~C yr B.P. Present within this sample was wood of both Picea and Larix laricina (tamarack), and needles of Picea, Abies balsamea (balsam fir) and cones of Picea mariana (black spruce). Seeds of Cyperus (sedge), Hypericurn (St. John's wort) and Viola (violet) were also identified. According to F. B. King, all of these genera include species adapted to growth in bogs or under moist coniferous forests. A change in the composition of the forest during the deposi- 76 tion of the upper part of the organic silt unit (Figure 6) was indicated by the addition of macrofossils of Larix laricina and Abies balsamea to the floral assemblage. Be- cause these species were not represented by pollen grains in the lower part of the organic silt unit, dating between about 25,000 to 23,000 ~Cyr B.P., F. B. King inferred that they may have been growing on the site at a slightly later time than the pollen record, that is, between about 23,000 to 22,000 '~c yr B.P. Both of these species, along ' with ficea mariana, are known to occur together frequently • under moist or peaty conditions. Therefore, evidence from the plant macrofossils supported J. E. King's (1979) interpretation of the site, but suggested a moister coni ferous forest than suggested by J.E. King. Sequence of events By combining the data derived from the sediment, vege tation (J. E. King, 1979; F. B. King, 1979), beetles and gastropods, an hypothetical model of the environment and the events at the location of the Athens North Quarry site for the period of about 25,000 to 22,000 14 c yr B.P. can be constructed. The .muck unit of zone A-1 probably represents a soil zone in a moist coniferous forest adjacent to the marshy margin of a pond or lake. High proportions of corraded fragments indicate microbial activity in the soil; this 77 argues against a bog environment with acidic or water logged conditions. The forest was composed dominantly of pine and spruce with lesser components of birch, willow, mulberry, and possibly oak, with an understory of grasses, herbs, and shrubs. Nearby marshy areas of sedges, rushes, wet mosses, and leaf litter were interrupted by patches of moist soil with sparse or no vegetation. The lithologic change from muck to organic silt perhaps indicates the onset of loess deposition in response to the expansion of glacial ice into the Lake Michigan basin. Slow loess .' . ' accumulation (approximately 7 cm per 100 years if a con stant rate of deposition is assumed) continued through the .j deposition of the upper half of zone A-1 and throughout zone A-2. Expansion of the nearby body of water occurred some time near the end of zone A-1 and the beginning of zone A- 2. Open water habitats were available at or very near the site as evidenced by the presence of dytiscids and hydro philids in zone A-2. Low percentages of corraded beetles may be an indication of reduced microbial activity due to a water-logged substrate. The forest at the site was domi nated by pine and spruce with a grass and herb understory during the deposition of zone A-2. Several beetle species from other terrestrial habitats in this zone provide evi dence for a forest floor with rotting logs, decaying plant debris, fungi, leaf molds, s.lime molds, mosses, dung, and 78 rotting carrion. The addition of tamarack to the forest was perhaps a reflecti-0n of an increase in soil moisture. The frequency of occurrence of scolytid beetles that live in dead and dying spruce increases upward in zone A-2. This increase may also indicate increased soil moisture beyond the tolerance of some of those trees. A possible shift to slightly colder climatic condi tions during the deposition of zone A-2 was suggested by J. " ' E. King (1979) to explain the disappearance of birch, ' willow, and mulberry near the top of the pollen profile of the Athens North Quarry site. overall, however, he be lieved the pollen evidence indicated a stable vegetation between 25,0oo- and 23,000 14c yr B.P. The appearance of tamarack and balsam fir within the forest during the period 23,000 to 22,000 14 c yr B.P. was interpreted by F. B. King (1979) as perhaps representative of the beginning of the shift from a mild interstadial climate to colder and moist er, full glacial conditions. Hygrophilous beetle species dominate the fauna throughout zone A-2. They indicate the presence of a thickly vegetated pond-marginal zone composed of sedges, emergent vegetation, willow shrubs, tussocks of moss, and matted plant debris. Expansion of the pond-marginal habi tat toward the center of the probable lake near the end of zone A-2 is inferred from_the general decrease in species 79 density and diversity of the beetles from open-water habi tats. Areas of exposed peaty or clayey soil are also implied by the presence of burrowing carabids and staphy linids. Zone A-3 is set apart from the preceding zones by the complete lack of beetle fossils, the appearance of terres trial snails, and an abrupt change in lithology. The cause of the sudden termination of the organic sequence is un- clear. It may be related to increased loess deposition as Ill .• - ' Woodfordian glaciers approached the area. The presence of the gastropods would seem to indicate a continued moist organic habitat, but no other evidence for the character of the local environment is present. Overall, the interpretations of the beetle assemblage, ,'' the pollen, and the plant macrofossils are in agreement. The shift to colder, moister conditions proposed by F. B. King for the period between 23,000 and 22,000 1~C yr B.P. at the Athens North Quarry site, however, is not reflected by the beetle data. 80 Local Environment at the Biggsville Site The compositions of the beetle assemblages from the Biggsville site and Athens North Quarry site are very similar. Only seven species from the Athens North Quarry site are missing at Biggsville. Four other Athens North • Quarry species may have been present at Biggsville but corresponding specimens from the Biggsville site were iden tifiable only at higher taxonomic levels. Species diversi ty and density, however, is much greater at the Biggsville ' . . site. The Biggsville beetle fauna includes 114 taxa whereas only 61 taxa were identified at the Athens North Quarry site. Variations in numbers of fossils between the two sites are shown in tables 8 and 9 of appendix A. The Biggsville site also has a higher overall percentage of aquatic taxa than does the Athens North Quarry site (31% at Biggsville vs 24% at Athens North Quarry). The Biggsville section is divided into two faunal zones. Zone B-1 includes sample intervals 5 through 22. ,,' Zone B-2 includes intervals 1 through 4 (Figure 13). The break between the two zones occurs within the basal loess paleosol unit but is not reflected in a change in lith ology. The relationship of the sample intervals to the lithologic units and the faunal zones of the Biggsville site is shown in figure 15. 8 J. Zone B-1 Faunal zone B-1 is based upon a total of 1,347 beetle individuals belonging to a minimum of 114 taxa. Beetle fossils from this zone represent aquatic, hygrophilic, forest and miscellaneous habitats. Zone B-1 is charac terized by high species diversity, dominance of the fauna by hygrophilic forms, a moderate open-water habitat com ponent, and a small but diagnostic forest habitat component. The aquatic habitats interpreted for zone B-1 include open-water, pond-marginal, and riparian situations. A shallow weedy body of open water bordered by thick growths of sedges and other vascular hydrophytes is indicated by fossils of dytiscids, hydrophilids, helodids, hydraenids, chrysomelids of the subfamily Donaciinae, and an aquatic curculionid. The proximity of a stream is inferred from the presence of several aquatic and hygrophilic species; all of the members of the Bembidion planiusculum species group described by Lindroth (1963) are strictly riparian, usually confined to the stoney-gravelly banks of running waters. The hydrophylids Hydrochus and Helophorus are known to dwell in streams as well .as ponds. The riffle beetle Dubiraphia is found chiefly on aquatic vegetation at the margins of slow-moving streams, as well as in lakes and ponds (Leech and Sanderson, 1959, p.986). The hydraenid Ochthebius is common in both riparian habitats and lakes. 82 Hygrophilic forms comprise the largest component of the coleopteran fauna of zone B-1. A vegetation-rich, pond-marginal habitat is indicated by several families of these. Weevils, such as Grypus, are commonly found on Equisetum (horsetail). Dorytomus commonly occurs on willow (Blatchley and Leng, 1916, p. 193) and species of Hypoleschus feed on the leaves of willow and other decid uous trees. The presence of additional weevils of the curculionid tribes Erirhinini and Ceutorhynchini also indi cate a wet pond-marginal environment. Rove beetle species, including Olophrum rotundicolle, Olophrum consimile, Eucnecosum, Psephidonus, Stenus, and Gymnusa, also indicate a swampy or very wet pond-marginal habitat composed of sedges, grasses, tussocks of moss, and accumulations of moist plant debris. The hygrophilic component of zone B-1 also includes a rich Bembidion fauna. Bembidion morulum and other members of the Bembidion musicola species-group usually occur among mosses and leaves on firm soil (Lindroth, 1963, p. 389, 387). Bembidion frontale prefers clayey soil mixed with organic material, often shaded by dense vegetation, at the margin of relatively small bodies of standing water (Lindroth, 1963, p. 402). Bembidion pseudbcautum occurs in rich swampy vegetation (Lindroth, 1963, p. 399). Bembidion transparens is found at the border of standing waters of a eutrophic or mesotrophic character, with a rich vegetation 83 of carex (sedge), Eleocharis palu.stris (spike rush), Typha latifolia (cattail), Comarum, and Menyanthes (buckbean) (Lindroth, 1963, p. 394). Bembidion concretum occurs in wet, eutrophic or mesotrophic swamps, with organic rich soil, and luxuriant vegetation including Carex and Typha ,;,. latifolia (Lindroth, 1963, p. 396). Bembidion fortestriatum most often occurs in swamps with Carex, Comarum, Menyanthes, and Similacina (Lindroth, 1963, p. 397). The habitat of both~- ~~parens and~- concretum often includes a carpet of mosses, particularly Drepanocladus aduncus, but never Sphagnum (Lindroth, 1963, p. 393-396). Other carabids found within this zone, such as Agonum corvus, Pterostichus patruelis, Ch.laenius, and Blethisa, occur in swamps or along standing water among sedges, rushes, and other pond-marginal plants. Patches of bare mud in this area are indicated by burrowing species of the Heteroceridae, Staphylinidae, and Carabidae. Heterocerids and the rove beetles Carpelimus and Bledius are found in wet sand, mud, or clay on the banks of ponds or streams (Moore and Legner, 1979, p. 22). The ground beetle Dyschirius commonly occurs together with Bledius and heterocerids, digging burrows in soil with sparse or no vegetation, usually near water (Lindroth, 1969, p. 132). A diverse group of scolytid beetles is present in zone 84 B-1. Their ecology was described by Wood (1982). Phloeotribus piceae, Ips borealis, and Carphoborus andersoni prefer the shaded or broken lower branches of Picea glauca. The hosts of Hylesinus belong to the genus Fraxinus (ash). Carphoborus carri, Polygraphus rufipennis, and Crypturgus borealis live in species of Picea, Abies, or Pinf:rs. The hosts of Orthotomicus caelatus probably include any species of Picea, Pinus, or Larix. Species of Pityophthorus are found in dead or dying twigs or small branches of both coniferous and deciduous trees. Scolytus feeds in both broad-leafed and coniferous trees. Other forest indicators are also present in zone B-1. The weevil Magdalis feeds in broken branches or in dead or dying trees. The cucujid Narthecius lives under the barks of both conifers and deciduous trees. The Nitidulidae feed on tree sap, and the Cantharidae are found on herbage and foliage. Several taxa in zone B-1 live in habitats charac teristic of a forest floor. Most species of the hydro philid genus Cercyon are strictly terrestrial but live in damp places, especially in decaying vegetal debris, or dung (Leech and Chandler, 1971, p. 345). Leiodids, such as Agathidium, live in fungi or slime mold on decaying plants or under bark, and Hydnobius has been collected in rotting fungus. Species of the micropeplid, Micropeplus, the '.l./I short-winged mold beetle, Reichenbachia, the pill beetle, Cytilus, the minute brown scavenger beetle, Corticaria, the -~ , 85 silken fungus beetle, Anchicera ephippiata, and the Scydmaenidae indicate the presence of decaying vegetable debris, fungi, moss, mold, and rotting logs. The Histeridae and the scarab Aphodius occur in dung as well as fungi and decomposing leaf litter. The members of the chrysomelid subfamily Alticinae feed on roots of plants, and the adults and larvae of the lady-bird, Nephus ornatus naviculatus, are often found on stems or leaves of plants, preying on mealybugs (Gordon, 1976, p. 278). Other members of the fauna of zone B-1 are represent ative of more open areas. The weevil Lepidophorus and the scarab Aegialia are characteristic of open sandy areas, often near water. Species of the ground beetle Notiophilus are heliophilous and rather xerophilous, occurring in open country, where the vegetation is sparse and the soil con sists of gravel, or in thin forest land (Lindroth, 1969, p. 90). Members of the ground beetle Pterostichus adstrictus species-group occur independently of open water (Lindroth, 1966, p. 485), whereas Patrobus inhabits open country but is more or less hygrophilous (Lindroth, 1969, p. 177). zone B-2 Zehe B-2 exhibits a sharp drop in both species diver sity and fossil density. The average number of taxa per sample interval is less than half of that of zone B-1, and an average of less than one-sixth as many identified indi- 86 viduals per kilogram are present (Table 9, Appendix A). Only four additional species made their first appearance during the time period encompassed by this zone. A total of 50 coleopteran individuals is present in this zone, representing at least 27 taxa. The majority of the beetles from this zone represent aquatic and hygro philic habitats, plus several miscellaneous habitats. The general trends which characterize this zone are lower spe cies diversity, continued dominance by hygrophilous forms, continued presence of open-water aquatic beetles, and a sharp decrease in forest taxa. Although the density of water beetles decreases sharply in zone B-2, aquatic habitats remain important. The dytiscids and hydrophilids present are common inhabi tants of shallow weedy ponds. Representatives of a ripar ian habitat were not found in this zone. The greatest percentage of beetle species represented by fossils in zone B-2 lives in water-related habitats. Weevils in the tribes Ceutorhynchini and Cryptorhynchini, as well as the rove beetles Olophrum and Stenus, are com monly found feeding on sedges and other pond-marginal plants. The ground beetle Diplocheila lives near stagnant fresh water where the vegetation is dense (Lindroth, 1968, p. 939). The Elaphrus species represented at the Biggsville site, either Elaphrus americanus or E. riparius, 87 lives on moist open ground where the vegetation is discon ( tinuous or lacking (Lindroth, 1969, p. 115-116) · The ' carabids Dyschirius and Bembidion also indicate the proxi mity of water and bare patches of soil. Patrobus is more or less hygrophilous but usually inhabits open country (Lindroth, 1969, p. 177). only. one forest-dweller, Pithophthorus, is represented in zone B-2; as in zone B-1, this scolytid indicates the presence of wood. Forest floor habitats, indicated by the staphylinid Tachinus, the pselaphid Reichenbachia, and the byrrhid Cytilus, include mold, moss, leaf litter, and other decaying material. Sedimentology Hallberg and Baker (written communication to D. P. Schwert, 1981) concluded that the Biggsville lithologic sequence (Figure 7} represents an infilled channel cut into Mississippian bedrock. The fill consists of fluvial depo sits, organic sediments, a peat sequence, and finally by Late Wisconsinan Peoria Loess. Fluvial deposits of coarse cobble gravel form the base of the sequence; these are overlain by beetle-bearing organic sediments. The grain size of the sediments decreases upward as the organic component of the units increases. A trend of decreasing mineral material and increasing organic matter continues upward through a sequence of silty peat and finally into a 88 woody fibrous peat unit, Formation of the peat probably 14 began sometime near 24,000 14 c yr B.P. At about 22,000 c yr B.P., an influx of mineral material became mixed with organic fragments and formed the organic silty loam to silty clay unit. The overlying basal loess paleosol indi cates a period of pedogenesis which ended at about 21,000 14c yr B.P., terminated by the deposition of the overlying massive loess unit. Sequence of events Combination of fossil beetle habitat data and con clusions drawn from the character of the sediment resulted in the construction of the following interpretation of the events at Biggsvitle during the period of approximately 28,000 to 21,000 14 c yr B.P. The fossil fauna of zone B-1 indicates a setting that included a shallow weedy body of open water surrounded by sedges, rushes, reeds, cattails, and other aquatic plants. Two species of Bembidion indicate that carpets of moss at the site were possibly composed of Drepanocladus rather than Sphagnum. Areas of firm soil covered by moss and leaves, patches of bare mud, and accumulations of plant debris were also present near the water. The possible proximity of a stream with sandy or gravelly banks is inferred from the presence of several riparian species. A nearby coniferous forest with open areas was probably domi- 89 nated by Picea, and included species of Fraxinus, and possibly Pi~, /\.bi~, and Lari~. The floor of the forest was moist, composed of moss, slime molds, fungi, molds, rotting logs, and decaying vegetal debris. The environment during the deposition of zone B-2 also included a body of open water bordered by sedges and other aquatic plants; no indicators of a riparian habitat are present. Areas of moist open ground with moss, molds, and decaying organic material plus bare patches of soil were present; but there is little evidence for the persistence of the coniferous forest in this zone. The most likely modern analog for the Biggsville site during the period of 28,000 to 21,000 ~Cyr B.P. is the margin of a bog in a spruce-dominated coniferous forest. The development of such an environment was discussed by Smith (1966, p. 182-185). Bog development begins with the colonization of open water by submerged and then floating plants. The accumulation of organic material raises the pond or lake bottom, and plants such as reeds, sedges, cotton grass, buckbean, and marsh cinquefoil begin to grow in the shallow margins. Mos·ses creep in and fill the space between the plants. As the mass of marginal vegetation thickens and expands, peat is formed and the mat extends out over the water. Shrubs surrounded by moss grow on thickened areas at the shoreward edge of the mat, followed 90 by the invasion of forest species, especially Picea and Larix, which advance as the mat closes toward the center of the lake. Larix is eventually replaced by Picea mariana, Thuja (aborvitae), and Abies balsamea. The Biggsville bog meets many of Smith's (1966) re quirements for a bog, such as the accumulation of peat and the presence of cushion-like vegetation. It was atypical perhaps in the composition of the mosses, because two Bembidion species indicate that the presence of Sphagnum was unlikely. The inference that the site was at the margin of the bog is based upon the possible proximity of forest and forest floor habitats. The forest surrounding the bog may not have been very dense, and it appears to have diminished near the top of the sequence. This decline may have been in response to the infilling of the bog by ·' Woodfordian loess. The sequence of events at the Biggsville site ended with a period of pedogenesis. Destruction of chitin during this process may account for the decline in numbers and diversity of beetle fossils near the top of the section (interval numbers 1 through 6). 91 Regional Climate Interpretation Because of the geographic proximity and overlapping ages of the Athens North Quarry and Biggsville sites, and similar ranges of their species, the faunas of the sites were combined in a study of the distribution patterns within the beetle assemblages. Maps of beetle distribu tions representative of the six distribution groups de scribed below illustrate that many of the beetle taxa recorded as fossils do not live in the area at the present time. The distribution groups are described as follows: Group A species {Figures 16 - 18) have northern transamerican distributions ranging from Alaska and the 1 northern Yukon to British Columbia in the west, and from ~ Newfoundland to the Great Lakes region in the east. Some spec may also occur in the Rocky Mountains as far south as Colorado. Group A* (Figure 19) has similar northern 1~ ' limits, but the ranges of the species of this group extend farther south into the United States, in some cases as far south as Arizona and Florida. Group B taxa (Figures 20 and 21) also have generally northern transamerican distributions, from southern British Columbia and Washington in the west, to the Great Lakes region in the east. However, the ranges of these species I. do not extend north of 50° North Latitude. Species with al similar northern limits but with expanded southern distri- ¥I 92 0 ml syo I 0 l\ffl 800 • !I!.!! borealla • Athens North Quarry o S'lale or provlnclal record 'Q Blggsvllle Figure 16. Present distribution of~ borealis (Coleoptera: Scolytidae). Locality data from Bright (1976, p.163) and wood (1982, p.681-683). Distribution group A; Athens North Quarry site. 93 0 ml 500 o km eoo • Chlaenius alternatus A Athens North Quarry Q Blggsvllle Figure 17. Present distribution of Chlaenius alternatus {Coleoptera: Carabidae). Locality~ data from Lindroth (1969, p. 993), CNC and USNM. Distribution group A; Athens North Quarry site. 94 0 mi 500 o km 800 • Bembldlon morulum • Athens North Quarry o S1a1e or provincial record 'v Biggsville Figure 18. Present distribution of Bembidion morulum (Coleoptera: Carabidae). Locality data from Lindroth (1963, p. 389). Distribution group A; Athens North Quarry and Biggsville sites. 95 I' 'I o ml 500 " ..,' __ ,__J o km aoo ·- - ' 0 ''·''""\ ' ' • Orthgtomlcus caelatus A Athens North Quarry o Stale or provincial record ~ Blggsvllle Pigure 19. Present distribution of Orthotomicus caelatus (Coleoptera: Scolytidae) Locali.ty data from Bright (1976, p. 149) and Wood (1982, p. 663-664) Distribution group A*; Biggsville site. 96 I I I 0 ml 500 .. J.:--"-.J •. O km 800 , ... -.... "\ • sembldlon trontale 6 Athens North Quarry 'iJ Biggsville Figure 20. Present distribution of Bembidion frontale (Coleoptera: Carabidae). Locality data from Lindroth (1963, .p. 402) and CNC. Distribution group B; Biggsville site. 97 .1 • Agonum corvus A Athens North Quarry o S1a1e or provlnclal record 'v Biggsville Figure 21. Present distribution of Agonurn corvus (Coleoptera: Carabidae). Locality data from Lindroth (1966, p. 603). Distribution group B; Biggsville site. 98 butions are assigned to distribution Group B* {Figure 22). Group C taxa (Figures 23 and 24) have eastern distri butions, occurring only as far west as Lake Winnipegosis in Manitoba and Texas. The eastern limit of this group ex tends from Newfoundland in the north to Georgia in the south. Distribution group D has one member, Carphoborus andersoni. Its present range is in northwestern North America, from Alaska in the west to northern Northwest Territorities, and northern Saskatchewan to the east (Figure 25). Although this species is rare at the present, it is a relatively common fossil in Wisconsinan assem blages. The modern and fossil distribution of this species was described by Ashworth (1977, p. 1627; 1980, p. 208), Morgan and Morgan (1980, p. 1121-1122), and Schwert and Morgan (1980, p. 107). Although Wood (1954) had indicated that this species may include another similar species, Carphoborus both have been retained as separate species in his recent (1982, p. 380-382) revision of the family Scolytidae. Schwert and Morgan. (1980, p. 107) pointed out that the occurrence of C. andersoni is rare and that its modern distribution may be extended upon more intensive sampling in eastern Canada. 99 '"":"tf 0 : 1 ,_... _~ \ 0 .' ' - ""''"' ' 0 , r-..J--- .. 4 o t' ,' I.. ,_ __ _,__t \. 0 , ' ~----- \. I ' t o,,'\ ,-----t-----1.------' tOs \ --- ,! I r-~ '; .' Q f Q I "'-- ! -~ : I -- i - 0 .. ' ..: _,..__• r' I - " " •. ,J....$~"""") 0 ,.,."",·, ' • lps 11111gens 4 Athena North Quarry o State or provincial record 'Q Biggsville Figure 22. Present distribution of Ips latidens (Coleoptera: Scolytidae). Locality data from Bright (1976, p. 155) and Wood (1982, p. 677). Distribution group B*; Athens North Quarry site. 100 • Mlerooeolus crtbratus • Athens North Ouarry 0 State or provincial record <;J Blggsville Figure 23. Present distribution of Micropeplus cribratus (Coloeptera: Micropeplidae). Locality data from Campbell (1968, p. 246). Distribution group C; Biggsville site. 101 ...... J I ' -- ..J tI 1-, "- i ' j ,---...L_' t. __ ... __ , I f I , '\ ,---J ... -f-----l.------'f I \ -- "'1 1 r---: r- -~ , ' t.. -... __ ..•, '·.. : J r- 0 ml 500 ,, __, ... --,-...! ;"-.!sii.----1 0 km 800 •.,.~- ... ft "· • Sphaeroderus nltldlcollls & Athens North Quarry brevoorli Q Biggsville Figure 24. Present distribution of Sphaeroderus nitidicollis brevoorti (Coleoptera: Carabidae). Locality data from Lindroth {1961, p. 30). Distribution group C; Athens North Quarry site. 102 0 ml 500 0 km eoo • Carpnoborus andetsonl 6 Athans North Quarry Q Biggsville Figure 25. Present distribution of Carphoborus andersoni (Coleoptera: Scolytidae). Locality data from Bright (1976, p. 101) and Wood (1982, p.380- 382). Distribution group D; Biggsville site. 103 Figure 26 shows the number of modern taxa represented in the Athens North Quarry and Biggsville beetle assem blages which presently occur in the provinces of Canada and the states of the United States. The greatest density of occurrences is in the southern boreal forest region of southern Canada and the northern Great Lakes region. With the exception of Carphoborus andersoni, the mixing of spe cies with disjunct ranges is minimal, During the initial stages of this study, it was ex pected that the transition from warmer interstadial condi tions to cold full-glacial conditions would be reflected by a corresponding transition from a boreal beetle fauna to a fauna with tundra or tree-line affinities. However, no marked change in the species composition of the beetle bearing faunal zones was apparent. The abrupt demise of the fauna of both sites by loess burial was perhaps more related to the depositional processes associated with wind than with a regional change in temperature. Therefore, the temperature change which allowed a tundra fauna described by Schwert et~- (1981) to survive in eastern Iowa at about 17,000 11c yr B.P. was not det~cted at the Athens North Quarry or Biggsville sites. No clear pattern of the disappearance of thermophilous species and the appearance of cold-adapted species resulted from the study of the Biggsville fauna. Further, the first 104 ! I A Athens North Quarry I Q B!ggsvllle I Figure 26. Numbers of taxa represented in the Athens I North Quarry and Biggsville beetle assemblages which presently occur in the provinces of Canada and the I states of the United States. l I I 105 or last appearances of a species may be the result of insufficient sampling rather than a significant climatic change. In the lowermost part of the sequence (sample intervals 19 and 20) three species of distribution group B made their last appearances: Bembidion frontale, Bembidion pseudocautum, and Anchicera ephippiata. Two southerly species, Micropeplus cribratus and Micropeplus made their last appearances in intervals 18 and 19. The northern species Bembidion morulum appeared around 24.,000 l"\c yr B.P. in interval number 12. But because both zones at Biggsville contain species with both northern and southern boreal forest distributions, a relatively stable climate is proposed for this area for the period of 28,000 to 21,000 0 I<\ C yr B. P. The same is true of the less diverse fauna of the area of the Athens North Quarry site. Bembidion morulum made its first appearance in interval number 7 at about 24,000 I"\ C yr B ..P (if a constant rate of deposition of about 7 cm per year is assumed). For the most part, however, both northern and southern boreal elements are present in zones A-1 and A-2, and climatic conditions would appear to have been stable at Athens North Quarry between 25,000 and 22,000 I'\ C yr B.P. The climatic stability indicated by the beetle assem blages of these two sites supports J. E. King's (1979) 106 r1 t pollen-based interpretation of a stable climate for central I Illinois. Minor changes in the composition of the local l vegetation (F. B. King, 1979; J.E. King, 1979) and the beetle fauna may have been the result of local changes within the plant and insect communities. The influence of the climatic shift to colder moister glacial conditions was perhaps not yet great enough at this time to produce a sharp change in the faunal assemblages at the two sites. This would imply that the transition from interglacial conditions to the full-glacial conditions described by Schwert et al. (1981) for east-central Illinois took place some time after 21,000 '"c yr B.P. Cold steppe and proba bly tundra conditions existed at Iowa City by about 17,000 •'IC yr B. P. (Schwert et ~-, 1981). . ' CONCLUSIONS Based upon the fossil beetle assemblages from two Middle to Late Wisconsinan sediment sequences, supplemented by sediment, gastropod, pollen, and plant macrofossil data, the following conclusions may be made. 1. The Athens North Quarry site represents the margin of a pond or eutrophic lake bordered by a moist coniferous forest. The sequence of events began with the expansion of a nearby lake or pond over the forest floor, and ended with the infilling of the water body by Woodfordian loess and organic material. 2. The Biggsville sequence reveals the development and demise of a bog in an abandoned stream chan '" nel, surrounded by at least a thin coniferous forest. The bog and forest were eventually choked by peat and loess deposits, and these were fol lowed by a period of pedogenesis. 3. The climate of central and western Illinois between about 28,000 and 21,000 t4c yr B.P. was relatively stable, and was similar to that of the southern boreal forest region of southern Canada and northern United States. The possible indica tions of cooler, wetter conditions beginning some 108 r time between 23,000 and 22,000 14 c yr B.P., in t I ferred by F. B. King (1979) and J.E. King (1979) from vegetational studies at Athens North Quarry, were not reflected by corresponding changes in the beetle fauna. Compositional changes in the floral and coleopteran fossil assemblages during this per iod are more likely reflections of changes in the local environment than of a regional climatic change. The major shift from interstadial condi tions to full-glacial conditions occurred sometime between the deposition of the beetle-bearing Biggsville section (ca. 21,000 years ago) and the development of the tundra conditions described by Schwer·t et al. (1981) in east-central Iowa (ca. 17,000 years ago) . .. •• APPENDIX Appendix A Sample interval depths, sample weights, and numbers of beetle individuals and taxa per interval. I • [ ... • • 111 Table 6. Sample interval depths and samp weights, Athens North Quarry site, Illinois. Interval Depth Weight number (m) (kg) 1 3.4 - 3.6 3.925 2 3.6 - 3.8 10.026 3 3.8 - 4.0 9.457 4 4.0 - 4.2 10.420 5 4.2 - 4.4 10.378 6 4.4 - 4.6 8.584 7 4.6 - 4.8 9.835 8 4.8 - 5.0 11. 624 9 5.0 - 5 • 2 11.257 10 5. 2 - 5.4 10.240 11 5.4 - 5.6 7.887 12 5. 6 - 5.8 11.180 13 5.8 - 6.0 11.120 14 6.0 - 6.2 11.685 • ,. 112 Table 7. Sample interval <:iepths and sample weights, Biggsville site, Illinois. Interval Depth Weight number (m) (kg) 1 4.42 - 4.52 4.52 2 4.52 - 4.62 4.08 3 4.62 - 4.72 3.60 4 4.72 - 4.82 3.25 5 4.82 - 4.92 3.43 6 4.92 - 5.02 3.40 7 5.02 - 5.12 3.72 8 5.12 - 5.22 2.73 9 5.22 - 5.32 3.24 10 5.32 - 5.42 3.17 11 5.42 - 5.52 3.36 12 5.52 - 5.62 3.34 13 5.62 5.72 3.76 14 5.72 - 5.82 4.02 15 5.82 - 5.92 3.13 16 5.92 - 6.02 4.01 17 6.02 - 6.12 3.94 18 6.12 - 6.22 4.44 19 6.22 - 6.32 5.50 20 6.32 - 6.42 4.95 21 6.42 - 6.52 5.12 22 6.52 - 6.62 5.50 113 Table 8. Numbers of identified beetles and minimum number of taxa per interval, Athens North Quarry site, Illinois. Interval Minimum number of Minimum number of Minimum number identified beetle identified beetle number individuals individuals per kg of taxa 1 0 0 0 2 19 { 10) * 1. 9 12 3 14 ( 43) 0.7 10 4 50 (20) 4.8 20 5 35 ( 2 9) 3.4 17 6 21 ( 2 9) 2.4 14 7 16 ( 12) 1. 6 11 8 34 ( 6) 2.9 12 9 20 ( 2 5) 1.8 12 10 17 (24) 1. 7 10 11 4 0) 0.5 4 12 18 6) 1. 6 11 13 28 0) 2.5 10 14 3 0) 0. 3 2 * Figures in parentheses are the percentages of aquatic beetle individuals. ~ 114 Table 9. Numbers of identified beetles and minimum number of taxa per interval, Biggsville site, Illinois. Interval Minimum number of Minimum number of Minimum number identified beetle identified beetle number individuals individuals per kg of taxa 1 9 ( 22) * 2.0 9 2 22 ( 3 6) 5.4 10 3 10 (20) 2.8 9 4 8 ( 12) 2.5 8 5 10 ( 10) 2.9 6 6 9 ( 3 3) 2.6 7 7 36 ( 11) 9.7 13 8 28 ( 21) 10.3 17 9 46 ( 4) 14.2 20 10 203 (11) 64.0 29 11 76 ( 32) 22.6 19 12 114 ( 2 7) 34.1 27 13 107 (33) 28.5 28 14 56 ( 4 3) 13.9 22 15 180 (40) 57.5 25 16 S3 ( 45) 13.2 24 17 81 (43) 20.6 21 18 42 (38) 9.5 23 19 95 ( 3 9) 17.3 34 20 96 (38) 19.4 34 21 54 ( 50) 10.5 22 22 60 ( 40) 10.9 28 * Figures in parentheses are the percentages of aquatic beetle individuals. .I .... . T 15'1 I ..... ~I REFERENCES --- REFERENCES Arnett, R.H., Jr., 1968, The beetles of the United States: A manual for identification: Ann Arbor, Michigan, American Entomological Institute, 1112 p. Ashworth, A. 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