The British geosynclinal complex was bounded on both northwest and southeast by continental margins during the Lower Paleozoic. The northern margin, in Scotland and the northern parts of Ireland, consisted of a mountain range, the Scottish Highlands, which was technically active and was positioned between a stable continental foreland to the northwest, and an uncoupled oceanic crustal plate to the southeast. The southern margin, in Wales and the Welsh Borderland, was characterized by a horst and graben structure and was gradually subsiding during most of the Silurian period. The Scottish margin produced tremendous quantities of immature graywacke sands which accumulated in a trench adjacent to the source area, on the site of the present Southern Uplands. A pattern developed about the middle of the Silurian in which deposits in this trench became deformed and uplifted shortly after deposition and, in turn, contributed sediments to the trench which was progressively displaced to the south toward the Lake District. In this way, the marine area was gradually overwhelmed by crustal foreshortening, deformation, and sedimentation, and by the end of the Silurian, continental conditions were established.
Articulated specimens of Pentamerus oblongus and Stricklandia lens occur in a vertical position, umbones down, in blocks collected from a bed of late Llandovery age [Red Mountain Formation] in Alabama and from the Lower Llandovery of Scotland, respectively. These brachiopods are in their original position of growth, as indicated by growth irregularities in many specimens caused by proximity to their neighbors. Ample attachment surface was available in the form of disarticulated valves which are preserved just beneath the umbones of the specimens; the delthyria of these pentameroids are covered in such a way by the umbones of the brachial valves that it seems likely that their pedicles atrophied during ontogeny.
Research Article| April 01, 1989 Comment and Reply on "Mesozoic overthrust tectonics in south China" David B. Rowley; David B. Rowley 1Department of Geophysical Sciences, 5 734 S. Ellis Avenue, University of Chicago, Chicago, Illinois 60637 Search for other works by this author on: GSW Google Scholar Alfred M. Ziegler; Alfred M. Ziegler 1Department of Geophysical Sciences, 5 734 S. Ellis Avenue, University of Chicago, Chicago, Illinois 60637 Search for other works by this author on: GSW Google Scholar Nie Gyou; Nie Gyou 1Department of Geophysical Sciences, 5 734 S. Ellis Avenue, University of Chicago, Chicago, Illinois 60637 Search for other works by this author on: GSW Google Scholar Kenneth J. Hsü; Kenneth J. Hsü 2Geological Institute, E.T.H., Zurich, Switzerland Search for other works by this author on: GSW Google Scholar Sun Shu; Sun Shu 3Academia Sinica, Being, China Search for other works by this author on: GSW Google Scholar Li Jiliang; Li Jiliang 3Academia Sinica, Being, China Search for other works by this author on: GSW Google Scholar Chen Haihong; Chen Haihong 3Academia Sinica, Being, China Search for other works by this author on: GSW Google Scholar Pen Haipo; Pen Haipo 3Academia Sinica, Being, China Search for other works by this author on: GSW Google Scholar A.M.C. Sengor A.M.C. Sengor 4I.T.Ü Fakültesi Jeologi, Istanbul, Turkey Search for other works by this author on: GSW Google Scholar Author and Article Information David B. Rowley 1Department of Geophysical Sciences, 5 734 S. Ellis Avenue, University of Chicago, Chicago, Illinois 60637 Alfred M. Ziegler 1Department of Geophysical Sciences, 5 734 S. Ellis Avenue, University of Chicago, Chicago, Illinois 60637 Nie Gyou 1Department of Geophysical Sciences, 5 734 S. Ellis Avenue, University of Chicago, Chicago, Illinois 60637 Kenneth J. Hsü 2Geological Institute, E.T.H., Zurich, Switzerland Sun Shu 3Academia Sinica, Being, China Li Jiliang 3Academia Sinica, Being, China Chen Haihong 3Academia Sinica, Being, China Pen Haipo 3Academia Sinica, Being, China A.M.C. Sengor 4I.T.Ü Fakültesi Jeologi, Istanbul, Turkey Publisher: Geological Society of America First Online: 02 Jun 2017 Online ISSN: 1943-2682 Print ISSN: 0091-7613 Geological Society of America Geology (1989) 17 (4): 384–387. https://doi.org/10.1130/0091-7613(1989)017<0384:CAROMO>2.3.CO;2 Article history First Online: 02 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn Email Permissions Search Site Citation David B. Rowley, Alfred M. Ziegler, Nie Gyou, Kenneth J. Hsü, Sun Shu, Li Jiliang, Chen Haihong, Pen Haipo, A.M.C. Sengor; Comment and Reply on "Mesozoic overthrust tectonics in south China". Geology 1989;; 17 (4): 384–387. doi: https://doi.org/10.1130/0091-7613(1989)017<0384:CAROMO>2.3.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 SocietyGeology Search Advanced Search Abstract No abstract available 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.
The continuity through the past 300 million years of key tropical sediment types, namely coals, evaporites, reefs and carbonates, is examined. Physical controls for their geographical distributions are related to the Hadley cell circulation, and its effects on rainfall and ocean circulation. Climate modelling studies are reviewed in this context, as are biogeographical studies of key fossil groups. Low‐latitude peats and coals represent everwet climates related to the Intertropical Convergence Zone near the Equator, as well as coastal diurnal rainfall systems elsewhere in the tropics and subtropics. The incidence of tropical coals and rainforests through time is variable, being least common during the interval of Pangean monsoonal climates. Evaporites represent the descending limbs of the Hadley cells and are centred at 10° to 40° north and south in latitudes that today show an excess of evaporation over precipitation. These deposits coincide with the deserts as well as seasonally rainy climates, and their latitudinal ranges seem to have been relatively constant through time. Reefs also can be related to the Hadley circulation. They thrive within the regions of clear water associated with broad areas of downwelling which are displaced toward the western portions of tropical oceans. These dynamic features are ultimately driven by the subtropical high‐pressure cells which are the surface signature of the subsiding branches of the Hadley circulation. Carbonates occupy the same areas, but extend into higher latitudes in regions where terrestrial surface gradients are low and clastic runoff from the land is minimal. We argue that the palaeo‐latitudinal record of all these climate‐sensitive sediment types is broadly similar to their environments and latitudes of formation today, implying that dynamic effects of atmospheric and oceanic circulation control their distribution, rather than temperature gradients that would expand or contract through time.
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