Palynology in Southern North America

Research Article| May 01, 1955 PALYNOLOGY IN SOUTHERN NORTH AMERICA: PART III: MICROFOSSIL PROFILES UNDER MEXICO CITY CORRELATED WITH THE SEDIMENTARY PROFILES KATHRYN H CLISBY; KATHRYN H CLISBY OBERLIN COLLEGE, OBERLIN, OHIO; CONSERVATION PROGRAM, NEW HAVEN, CONN. Search for other works by this author on: GSW Google Scholar PAUL B SEARS PAUL B SEARS OBERLIN COLLEGE, OBERLIN, OHIO; CONSERVATION PROGRAM, NEW HAVEN, CONN. Search for other works by this author on: GSW Google Scholar Author and Article Information KATHRYN H CLISBY OBERLIN COLLEGE, OBERLIN, OHIO; CONSERVATION PROGRAM, NEW HAVEN, CONN. PAUL B SEARS OBERLIN COLLEGE, OBERLIN, OHIO; CONSERVATION PROGRAM, NEW HAVEN, CONN. Publisher: Geological Society of America Received: 18 May 1954 First Online: 02 Mar 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Copyright © 1955, The Geological Society of America, Inc. Copyright is not claimed on any material prepared by U.S. government employees within the scope of their employment. GSA Bulletin (1955) 66 (5): 511–520. https://doi.org/10.1130/0016-7606(1955)66511:PISNA2.0.CO;2 Article history Received: 18 May 1954 First Online: 02 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation KATHRYN H CLISBY, PAUL B SEARS; PALYNOLOGY IN SOUTHERN NORTH AMERICA: PART III: MICROFOSSIL PROFILES UNDER MEXICO CITY CORRELATED WITH THE SEDIMENTARY PROFILES. GSA Bulletin 1955;; 66 (5): 511–520. doi: https://doi.org/10.1130/0016-7606(1955)66511:PISNA2.0.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract The sediments of the Cuenca de Mexico fall into two classes—transported materials from the surrounding highlands and residual materials deposited as a result of limnological processes, in situ. The latter include inorganic and organic constituents as well as microfossils. Studied together these components reflect events influenced or controlled by changing climates, by volcanic and tectonic activity, and by erosion whether natural or accelerated by man.Changes in percentage composition of upland forest pollen reflect changes in available moisture, and thus in climate. Changes in the density or abundance of recoverable pollen are closely related to changes in sedimentary zones and in water content of the sediments. High pollen density is associated with slow sedimentation and high water content of the sediments, whereas stages of rapid sedimentation and low water content are marked by sparseness or absence of pollen. As upland forest pollen composition is chiefly a function of climate, pollen density is a function of volcanic and other physiographic processes.Pollen and spores from lowland communities reflect swamp conditions and changes in vegetation caused by disturbance of habitat by volcanism, tectonic activity, and human occupation. Temporary disturbance from fresh ash fall and tectonic activity tends to be followed by a brief period of heavy density of ruderal pollen (composite, amaranth, grass) and by prompt restoration of the prevailing upland forest communities.Maize pollen was recovered throughout the archeological period and at a depth of 9 m, predating the presence of agricultural man in the basin. It was again recovered at 70m, a depth which represents considerable antiquity for maize; which is evidence in favor of the American origin of this plant.Contemporary pollen gathered from a site comparable to the Mexico City basin indicates relatively short distance of upland pollen transport. Therefore, the sparse spruce pollen found at various horizons in the Mexican cores probably came from the vicinity during times cooler than the present. Exceptionally heavy spruce pollen in samples from a recent horizon appears to be the result of redeposition of older sediments from the surrounding highlands.Correlation of the sedimentary components involves a complex of climatic, tectonic, volcanic and biotic factors; evidence from every possible source, in addition to conventional pollen analysis, is required for proper interpretation. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.