Squantum “Tillite”, Massachusetts—Evidence of Glaciation or Subaqueous Mass Movements?

Research Article| September 01, 1961 Squantum "Tillite", Massachusetts—Evidence of Glaciation or Subaqueous Mass Movements? R. H DOTT, JR. R. H DOTT, JR. University of Wisconsin, Madison, Wis Search for other works by this author on: GSW Google Scholar GSA Bulletin (1961) 72 (9): 1289–1305. https://doi.org/10.1130/0016-7606(1961)72[1289:STMOGO]2.0.CO;2 Article history received: 20 Apr 1960 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 R. H DOTT; Squantum "Tillite", Massachusetts—Evidence of Glaciation or Subaqueous Mass Movements?. GSA Bulletin 1961;; 72 (9): 1289–1305. doi: https://doi.org/10.1130/0016-7606(1961)72[1289:STMOGO]2.0.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 writer interprets the Boston Bay group as partially intertongued lithofacies of coarse conglomerate and associated volcanic rocks (Roxbury conglomerate) and finely laminated siltstone and mudstone (Cambridge "slate"). He regards the Squantum "tillite" as multiple discontinuous lenses of unsorted pebbly to bouldery mudstone of various ages interstratified within this complex. Although fossil evidence is inconclusive, stratigraphic relationships and clastic compositions suggest that these deposits were formed during middle Paleozoic diastrophism. The writer does not consider the Squantum as a temporal equivalent to southern hemisphere Permo-Carboniferous glaciation, as advocates of a glacial origin had supposed. Lack of glacial pavement and comparison of composition, graded bedding, gross stratigraphy, and tectonic setting with known submarine slide and mass-flow deposits render the glacial interpretation suspect. Origin by gravity movement of rapidly deposited, volcanic-rich sediments and periodic resedimentation by turbidity currents in a Paleozoic eugeosynclinal belt is a more plausible alternative.Very poor sorting, striated clasts, faceting, and even some rafted erratic fragments in fine, laminated mudstones can arise from mechanisms other than glaciation. A preserved, extensive, grooved and polished pavement overlain by poorly sorted, till-like material—particularly if nonmarine—is the most compelling glacial evidence. Very large erratic boulders are suggestive of ice movement, as are abundant rafted erratic fragments in fine muds, as in the Gowganda formation of Ontario. Independent biologic or isotopic cold-temperature indicators are sorely needed to strengthen glacial interpretations. General stratigraphic relationships and tectonic setting serve as important factors in judging probability of alternate interpretations, particularly in geosynclinal sequences. From these criteria, the writer judges that only the Permo-Carboniferous glaciation in certain parts of the southern hemisphere is firmly established. The Gowganda and some other Precambrian deposits are very likely glacial, but most postulated examples must be re-evaluated. 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.