15 April 2001
HISTORY OF PALEOLIMNOLOGY AT THE LIMNOLOGICAL RESEARCH CENTER OF THE UNIVERSITY OF MINNESOTA
Herbert E. Wright
In the following narrative two aspects of paleolimnology are considered: (1) formation of lake basins, and (2) constituents of lake sediments and their environmental and climatic interpretation. The approach is historical, and the projects concern not only Minnesota and elsewhere in North America but also other parts of the world. The projects mentioned are those referenced to numbered publications in the List of Contributions of the Limnological Research Center, which are included the LRC web site (http://lrc.geo.umn.edu). Unpublished theses are not included. At the end is the roster of students and post-doctoral associates not mentioned in the publications list arranged by decades.
(1) Origin of lakes
First should be considered the proglacial lakes that became filled with sediments during the glacial period. The largest of these was Glacial Lake Agassiz, which was formed between a moraine in northwestern Minnesota and the retreating ice front and extended well into Canada (Bjorck, 277). Lake Agassiz drained at times south into the Minnesota River valley (Matsch, 53) and thence the Mississippi, and at other times into Lake Superior through southern Manitoba and Ontario or northwest to the Mackenzie River and the Arctic Ocean . Other proglacial lakes, described in publications of the Minnesota Geological Survey, also existed at this time, e.g. Lake Minnesota south of Mankato, Lake Aitken and Lake Upham in north-central and northeastern Minnesota, and various lakes on what is now the Anoka sand plain.
The origin of existing Minnesota lakes was studied by Zumberge, who made a detailed classification of lakes on the basis of their mode of origin and subsequent geomorphic modification, and his Ph.D. thesis was published by the Minnesota Geological Survey as Bulletin 53 in 1952. Inasmuch as almost all Minnesota lakes are of glacial erosional or depositional origin, the result was principally a thorough classification of glacial lakes, and as such it was adopted by Hutchinson in Volume 1 of his authoritative Treatise in Limnology. The modification of lake morphology included the erosion of projecting headlands and the formation of bars and spits and curving shorelines. A summary of lake origins for Minnesota was published by Wright (396)
Other lake basins in Minnesota developed as a result of river action. The most conspicuous example is Lake Pepin, which formed in the Mississippi River valley behind a dam deposited by the tributary Chippewa River from Wisconsin when southward discharge of Glacial Lake Agassiz was diverted. Subsequent progradation of the delta of the Mississippi into Lake Pepin caused another dam to be built across the St. Croix River, thereby forming Lake St. Croix.. The chronology of formation of Lake Pepin and Lake St. Croix and the subsequent history was reviewed by Wright et al. (495).
(2) Lake Sediments
Pollen Studies
Minnesota
Because lake sediments in deep water may accumulate in a regular manner and remain undisturbed, they may contain an uninterrupted stratigraphy of aquatic organisms that have preservable hard parts, as well as other biological and geochemical components produced in the lake. But they may also contain pollen grains and mineral particles washed in from the surrounding landscape or blown in from near and far. The first approach to the stratigraphy of organic lake sediments has usually been pollen analysis, because the vegetational history inferred from the pollen content is an easily understood approach to environmental and climatic reconstructions. In Europe the long tradition of pollen analysis of peat deposits and to a less extent lake deposits resulted in the identification of a sequence of postglacial vegetational changes, particularly in Scandinavia, where glacial lakes are numerous. Although a similar tradition did not exist in the US, the pattern of moraines and other glacial features in Minnesota were believed to be a record of climatic changes that might also be manifested by the vegetational history revealed by stratigraphic pollen analysis of lake sediments. Accordingly research on pollen analysis was initiated in Minnesota, and
Magnus Fries,
an experienced Swedish specialist, came to the Geology Department in 1958 to establish a laboratory and supervise student research. In addition to his own work at a lake south of Ely (4a), he assisted several students in undertaking similar projects that were subsequently published, notably
Winter (4, 5),
Patten (4d, 5),
McAndrews (23), and
Cushing (12, 41, 45, 124).
In addition, in these early years 'investigations were independently made of the biochemical constituents of lake sediments, particularly by F. M. Swain and students (1, 2, 3, 11, 19, 21, 29, 33) and in later years by Eville Gorham and others (10, 14, 20, 47, 84, 104, 105, 109, 111, 129, 135, 140.)
During these developments the Limnological Research Center was established in 1959 as a result of a grant from the Hill Family Foundation, which had supported much of the early pollen studies. The activities of the pollen laboratory were incorporated into the Limnological Research Center and were supplemented by research on lake processes themselves.
Pollen studies in the Minnesota area continued with other visitors from Europe, e.g. Saskia Jelgersma from The Netherlands (4b), Krystyna Wasylikowa (60) and Kazik Wasylik from Poland, Willem Van Zeist from The Netherlands (52), Svante Bjorck from Sweden (368), W.A. Watts from Ireland (25, t4, 44, 86, 227,468), Richard West (4c) and H.J.B. Birks (133, 160, 213, 224) and Hilary Birks (114, 132, 161).from England, and C.R. Janssen (30, 31, 37.,43, 54, 99, 212, 423) from The Netherlands. H. Birks added plant-macrofossil analyses to the interpretations of pollen sequences, as had Watts. Published student projects on Minnesota lake sediments included those of Baker (4e), Shay (46, 56), Craig (87), Waddington (73), Amundsen (121), Stark (145), Synerholm (158), Murchie (317), Grimm (279), Swain (91, 178), Jacobson (179, 280), Almendinger (329, 330), Anthony (107), Keen (378), Eyster-Smith (334), Griffin (123), and Card (517). Paleomagnetic studies of lake sediments supplementing the pollen work were developed on Minnesota lakes by Banerjee (110,168, 245), Lund (210), and King (233, 234), 235). Several articles on coring devices and techniques were published by Wright and others (9, 13, 49, 162, 249, 304, 380, 395) and later by Verschuren (439)
Elsewhere in North America
Meanwhile other pollen investigations were initiated outside Minnesota with the objective of reconstructing vegetational and climatic history in other regions, e.g. Maher (7) and Bright (35, 36) in the Rocky Mountains and Bjorck in southern Ontario (300). Studies of lakes in the Chuska Mountains of northwestern New Mexico involved problems of the origin of non-glacial lakes (Wright 18) but also substantial pollen work (89, 93). Here another constituent of lake sediments was analyzed, i.e Cladocera (Megard, 8, 15, 16).
European visitors during these years included Eberhard Gruger (78., 101, 102) for work in Illinois and Johanna Gruger (94) in Kansas. Projects were undertaken by Watts and Wright (27, 269) in Nebraska and by Watts in the eastern U.S in the Appalachian Mountains and coastal plain (Watts 69, 79, 127, 165, 175, 188, 246) and in Florida (55, 81, 134, 157, 339, 443, 460, 480, 481) and by students Craig (72), P. Delcourt (130, 195, 196, 197, 221), H. Delcourt (194). and Teed (564). Other projects outside Minnesota were pursued in Ohio by Shane (306, 388, 414, 458, 459, 533) and elsewhere by others (28, 97, 128, 436, 474).
Outside North America
At about the same time lake-sediment studies were initiated in the Zagros Mountains of southwestern Iran, with pollen analysis undertaken by van Zeist (4, 42a, 50, 52), and this was followed by analyses of plant macrofossils by Wasylikowa (42) and Cladocera by Megard 22) from the same sediment. That work in turn has led to the analysis of other components of the lake sediments, namely stable isotopes (Stevens et al. 568), diatoms (Snyder et al. 569), and plant macrofossils Wasylikowa (571).
Charcoal
When a major wildfire occurred in northern Minnesota a project was initiated on the effects of the fire on the streams and lakes. This led to a thesis study by R. Wright (151) and to other publications (139, 312, 313). Interest in fire history then prompted a project in southern Labrador, which involved studies of the modern vegetation vegetation as well as the geochemistry of lake sediments (Engstrom, 264, 298, 303, 336), pollen stratigraphy (Lamb 185, 237, King 314, 453), and the formation of peatland pools (Foster and others 242, 273, 274, 321, 337, 342, 399). Studies were conducted elsewhere on the charcoal content of lake sediments (322), especially in the Boundary Waters Canoe Area (Swain 91, 178, Craig 87) and Itasca State Park (Clark 349, 350, 351, 355, 367, 370, 371, 372, 373, 377, 384, 391).
Lake-level Changes
A different approach to lake history involved detection of lake-level changes by analysis of plant macrofossils and mineral sediments. The first this was by Watts and Winter (25, 156), but later by systematic study of a cores from shallow to deeper water, focusing on groundwater/lake through a thesis study by Almendinger 393, 410) and related work (408, 409).. It was pursued in a different area by Locke in studies sediment geochemistry (472, 480, 524).
Diatoms and Geochemical Constituents
Interest in other components of lake sediments prompted analysis of diatoms. As with pollen studies, European experts who were recruited to start diatom stratigraphic analyses at Minnesota. The first visitor was MajBritt Florin from Sweden (57, 58), followed by Elizabeth Haworth (88) and R.W. Batttarbee (276, 299, 335) from England. Diatom studies were later pursued by post-docs Bradbury (77, 85, 92, 106., 108, 112, 131, 146, 155, 166), Brugam (176, 187, 189, 193, 216, 256, 293), and Kingston (275, 287). The first student project was that of Fritz (265, 347, 348) for a site in England. and later for studies of lake acidification in the UK (332, 374, 404). She then initiated work in the prairies of the Northern Great Plains (400. 401, 435, 440, 444, 501, 541) that included student projects by Laird (473, 504, 506, 507). This work has been supplemented by the study of ostracodes and geochemical and sedimentological components of the lake sediments (387, 402, 441, 479,, 483, 484, 499, 529, 530, 541). Similar multi-disciplinary studies were undertaken in Alaska by Hu and others (485, 503, 514, 531), in Yellowstone Park by Engstrom and others (407, 412), and elsewhere by Ito (497, 528, 535). Preliminary research on Cladoceran remains, non-diatom algae, and pigments were undertaken but not pursued (80, 82, 126, 140, 167,186, 291, 411). Geochemical work related to lake pollution was initiated by Engstrom and others (320, 437, 438, 445).
The geochemical investigations on the Great Plains lakes included stable-isotope analysis, and the same approach was applied to Minnesota varved lake sediments (482, 492, 532) and to sediments in New York (497, 528) and in western Ireland (457, 566).
Other Research Outside USA
Paleolimnological studies elsewhere in the world included a project on lakes on the stagnant ice of a surging glacier in the Yukon by Wright and others (83, 198, 204, 206) and the Glacier Bay region of southeastern Alaska by Engstrom and others 403, 465, 570). Lake sediments were also studied in the Andes by Wright, Seltzer, and Hansen (184, 369, 376, 406, 413, 446, 448, 462, 513, 515) and by Hansen in Central America (302) and Bermuda (333). A thesis study of the aquatic microfauna of tropical lakes in Kenya resulted in papers describing the history of changes in lake level and salinity by Verschuren (464.,469, 496, 505, 518, 519, 523, 525, 536, 537, 538,539), Work on the diatom stratigraphy of sediments in the Antarctic seas was published by Leventer (489, 490, 491, 508, 542, 543, 544).
Mineral Sediments
With the advent of Kerry Kelts as director of the LRC, lithologic studies of lake sediments became more common (425, 426, 450, 451, 452, 470, 475, 509, 551, 552, 557, especially by Valero Garces in Spain (526, 527, 555, 561) and the Andes of Chile and Argentina (476,454, 534, 556, 558, 559, 560, 562) as well as in the Northern Great Plains (461,484) and by Schwalb (463, 472, 488, 520, 562). Studies in Africa were expanded (494, 510, 511, 512, 521, 550, 554. Earlier sedimentological studies had been undertaken in Lake Superior (219, 220. 222, 236, 252, 253).
Other Publications
In addition to the publications mentioned above, which mostly concern analysis of components of lake sediments, regional reviews based on the pollen content or other aspects of paleolimnology by Wright and others can be mentioned (40. 59, 64, 70, 76, 115, 147, 148, 149, 208, 230, 225, 228, 247, 248, 251, 270, 286, 301, 344, 345, 356, 357, 358, 360, 375, 377, 382, 389, 394, 398, 427, 428. 431, 447, 471, 487, 522, 565). Included in the list of LRC Contributions are many papers concerned with neolimnology published by J. Shapiro and students and other persons associated at some time with the LRC, e.g. Eville Gorham. It also includes non-stratigraphic papers on extant vegetation and on peatlands, the latter notably by Paul Glaser, Jan Janssens, and C.R. Janssen.
The foregoing account concerns the publications on paleolimnology in the Limnological Research Center of the School of Earth Sciences. It excludes unpublished theses It should be emphasized that a substantial number of paleoecological studies based on pollen analysis of lake sediments have been undertaken in the Ecology Department in the laboratories of M.B. Davis and E.J. Cushing. Some of the students mentioned above, although closely associated with the LRC, undertook some or all of their pollen analyses in the Ecology Department because of the expert pollen-morphological resources available there, notably E.C. Grimm, G.L. Jacobson, J.R. Almendinger, and R. Teed, as well as Barbara Hansen. Other publications from that department involving the pollen content of lake and peat sediments include especially studies of beech/hemlock relations in northern Michigan.
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