198,274 research outputs found
Tertiary palaeosurfaces of the SW Deccan, Western India: implications for passive margin uplift
No full textTwo genetically distinct lateritized palaeosurfaces of different ages are recognized in the southwest Deccan Traps region of Western India using a combination of geochemical, topographical, and satellite image data. The Deccan Traps were erupted at the Cretaceous-Tertiary boundary (c. 65 Ma), and comprise a huge area of originally near-horizontal basalt lavas covering much of northwest Peninsular India, and topographically forming the coast-parallel Western Ghats escarpment and elevated Maharashtra plateau to the east.
Remnants of the older, palaeosurface currently exist as a series of isolated, laterite-capped plateaux forming the highest elevations along the Western Ghats (15°30'–18°15' N). This surface is of late Cretaceous-early Tertiary age, and originally developed upon flows which lay at, or near to, the top of the lava sequence. This lateritization phase was terminated by a period of uplift and extensive erosion in lower- to mid-Tertiary times during which the low-lying, low-relief coastal (Konkan) plain developed through the eastward recession of the Ghats scarpline. A second phase of lateritisation occurred upon this coastal pediplain during mid- to late Tertiary times. Since the earlier uplift had gently deformed the lava pile prior to the development of the pedimented surface, the low-level Konkian laterite lies with marked angular unconformity upon the lava stratigraphy. Both surfaces have been subject to further large-scale distortion resulting from continuing uplift effects.
Development and evolution of these Deccan palaeosurfaces is important since together they provide a record of uplift effects in western India. Moreover, they offer a datum against which the uplift erosional history may be further constrained and demonstrate that uplift effects have acted upon the Indian margin throughout the Tertiary. Since such longevity of uplift is difficult to reconcile with the commonly cited thermal and dynamic post-rift mechanisms known to act upon passive margins, the morphological and structural evolution of the rifted Deccan margin is better described in terms of denudational isostasy
Remote sensing for mapping palaeosurfaces on the basis of surficial chemistry; a mixed pixel approach. In: Widdowson, M. (ed) Palaeosurfaces: Recognition, Reconstruction and Palaeoenvironmental Interpretation
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Discussion: Sheth, H.C. Plume-related regional pre-volcanic uplift in the Deccan Traps: Absence of evidence, evidence of absence
No full textSheth misreads key aspects of my earlier comment. For the record: I consider ‘uplift’ an issue central to the plume debate. I reiterate; uplift ‘remains a polemic issue’, (i.e. worthy of discussion). Word limits preclude the desired detailed dialogue, but some important issues are raised below.
I entirely agree that concerted field work is necessary, but both this paper and Sheth (2005) offer little new field data, and instead rely largely upon an interpretation of previous authors’ information. Such retrospectives do not permit the reader to evaluate the relative merits of plume versus non-plume models, and so cannot materially progress debate.
The argument regarding southward (not eastward, as suggested by Sheth) younging of the main Deccan edifice remains robust. Three independent lines of geological evidence support this interpretation: Two independent lines are usually deemed sufficient to indicate a scientific ‘truth’.
Sheth concludes, logically, that Western Ghats is the product of post-Deccan denudational processes. This particular interpretation has long been available (e.g. Widdowson and Cox, 1996; Widdowson, 1997; Gunnell and Fleitout, 1998; Widdowson and Mitchell, 1999). Given this issue is not in dispute, why raise it here?
Sheth asserts that Cox’s (1989) plume-head drainage idea is problematic. Perhaps, but the fact that radial drainage patterns do occur in key CFBPs remains a valid, if inexplicable (?) observation. Cox’s idea was superseded by arguments provided in Widdowson and Cox (1996), Widdowson (1997; see fig. 14), and AFTA data (Gunnell et al., 2003), and so becomes irrelevant for contending pre-eruptive uplift.
Sheth argues, correctly, that the nature of the pre-Deccan palaeosurface holds important clues regarding pre-eruptive uplift in the DVP (Jerram and Widdowson, 2005). Much of this surface remains buried by the Deccan lavas, and is both inaccessible and unknowable. It only becomes exposed around the northern and eastern periphery of the main lava pile. Such peripheral localities, including many of those described by Sheth, were hundreds of kilometres from the Deccan eruptive loci. If any uplift did occur here, it would have been minimal at such large distances from the focus of putative plume head uplift, and thus consistent with that affecting the Dongargaon basin, for example (Tandon, 2002; Samant and Mohabey 2005).
The pre-eruptive palaeosurface has been significantly modified by the crustal loading of the Deccan edifice, and in its western extensions suppressed far below datum. Thus, the gross form and elevation of this basement – basalt contact is largely an artefact of post-eruptive flexural adjustment. Nevertheless, Sheth argues that this highly modified surface reveals a ‘peneplain’, and that its preservation as such precludes significant fluvial incision. Possibly: But peneplains are the consequence of erosion, and the classical, albeit obsolete, Davisian model requires regional uplift as a trigger for peneplanation to proceed. Etchplanation is more appropriate to the development of the pre-Deccan surface (e.g. Büdel, 1982). Here, thick alteration mantles accumulate through tropical weathering of surfaces exposed during prolonged periods of tectonic stability. If, as Sheth requires, such conditions had characterised the pre-Deccan land surface, then the widespread absence of deep weathering mantle preserved beneath the lava units may instead indicate that this landscape had been thoroughly stripped prior to DVP eruptions. Etchplain stripping may be achieved through widespread fluvial erosion induced by regional uplift (Borger and Widdowson, 2001).
Offshore sedimentary records in the Krishna, Godavari, and Narmada-Tapti basins, all reveal significant increases in Late Cretaceous depositional flux (Halkett et al. 2001): these data are consistent with pre-eruptive regional erosion of peninsular India – starting with the stripping of an easily erodable weathering mantle perhaps?
If pre-eruptive (plume-driven?) uplift had occurred in pre-Deccan peninsular India, what might then be recorded in the erosional and sedimentary chronologies of the DVP peripheral regions? Removal of any easily erodable weathering mantle, perhaps; minimal changes in elevation, possibly; development of shallow basins receiving fine clastic input from the plume-uplift effects hundreds of kilometres away - may be. This interpretation of the available infra- and intra-trappean sedimentary (i.e. Lameta Beds) data is equally plausible using the same compendium of field evidence provided by Sheth. Accordingly, I offer a modified, précis version of Sheth’s own summary:
‘Any original flatness and elevation of the pre-Deccan landscape has been significantly modified by syn- and post-eruptive isostatic adjustment deriving, initially, from the loading of the DVP edifice, and subsequently by denudational unloading. The occurrence of a stripped, pre-eruptive etchplain, together with associated offshore sedimentological data, are consistent with those phenomena predicted had a large plume head upwelled beneath India during the Late Cretaceous.
Post-Deccan uplift has elevated both the pre-Deccan, and post-Deccan surfaces. This uplift of the Western Ghats is not related to a putative Deccan plume: it is not domal, occurs beyond the limits off the Deccan lava cover, and represents a later, denudationally-driven, uplift (Widdowson, 1997). Thus, the easterly drainage of the Indian peninsula is not plume-related dome flank drainage, and is largely antecedent to denudational uplift effects’.
To summarise, of those observations described by Sheth, most, if not all, can equally and adequately be explained by the passage of India over a static, spatially restricted, mantle melting anomaly during the Late Cretaceous: For want of a better term, and until consensus offers me a better alternative, I will continue to call this anomaly, sensu lato, a ‘mantle plume’. I end by reiterating the rationale to my initial comment: The challenge to Sheth remains to deliver us an alternative, ‘non plume’, model that can better explain the Deccan CFBP
The geochemistry of Indian bole horizons: palaeoenvironmental implications of Deccan intravolcanic palaeosurfaces
No full textDeccan intravolcanic bole horizons represent weathering products formed during major hiatuses of a major volcanic episode. In these quiescent periods weathering processes pervasively altered the newly formed volcanic landscape and subsequent flows covered and effectively fossilized the resulting weathered palaeosurfaces. The current work is a detailed geochemical study which examines patterns of element mobilization during these intravolcanic weathering events.
The bole horizons normally rest on top of altered basaltic lavas. Both boles and altered lavas represent a comparatively early stage in weathering because the content of chemically residual elements, such as aluminium and iron, are closer to fresh basalt than laterite. Nevertheless, these is clear evidence for significant chemical alteration because the more mobile elements such as calcium and sodium have been substantially removed. A chemically distinctive nature for some boles can be demonstrated from chondrite normalized REE plots and, in these instances, strontium and neodymium isotopic compositions demonstrate that the fine-grained bole material is derived from a chemically distinct source. In addition, thin sections reveal that these fine grained portions commonly contains glass shards and occasionally fresh phenocrysts. It is therefore suggested that many Deccan boles are in fact weathered pyroclastic material, and that the pyroclastic content of the basaltic succession may be greater than previously supposed. A significant pyroclastic input during the Deccan eruptions has important palaeoenvironmental implications for the fate of late Cretaceous flora and fauna in peninsular India
Dr. Duane M. Jackson, Morehouse College, July 2011
No full textThis video is a conversation with Dr. Duane M. Jackson. Dr. Jackson talks about his paper, "Recall and the Serial Position Effect: The Role of Primacy and Recency on Accounting Students' Performance." Jackie Daniel, AUC Woodruff Library, is the interviewer
"Reflections on the subject of Emigration from Europe with a view to Settlement in the United States" By M. Carey.
No full text"Reflections on the subject of Emigration from Europe with a view to Settlement in the United States: containing bried sketches of the moral and political character of those states.
By M. Carey, member of the American philosophical, and of the American Antiquarian Society, and author of The Olive Branch, Cindiciae Hibernicae, essays on banking, on political economy, and on internal improvement.
To which are now added the English editor's comments on the subject; together with Important Advice to Emigrants, and Cautions Against Impositions Practiced in the Outports
RLS : Regional Language Studies
No full textA critical history of dialect collecting in Newfoundland / G.M. Story -- Selecting and Presenting the Lexicon / William Kirwin -- Selected sample entries -- Speech, sounds and taperecorded evidence in the "Dictionary of Newfoundland English" / J.D.A Widdowson
Dispelling the Myths Behind First-author Citation Counts
No full textWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
TA Treatment of Depression: A Hermeneutic Single-Case Efficacy Design Study - 'Sara'
No full textThis study is the first of a series of three, and represents an Italian systematic replication of previous UK findings (Widdowson 2012a, 2012b, 2012c, 2013) that investigated the effectiveness of a recently manualised transactional analysis treatment for depression with British clients, using Hermeneutic Single-Case Efficacy Design (HSCED). The various stages of HSCED as a systematic case study research method are described, as a quasi-judicial method to sift case evidence in which researchers construct opposing arguments around quantitative and qualitative multiple source evidences and judges evaluate these for and against propositions to conclude whether the client changed substantially over the course of therapy and that the outcome was attributable to the therapy. The therapist in this case was a white Italian woman with 10 years clinical experience and the client, Sara, was a 62-year old white Italian woman with moderate depression and three recent bereavements, who attended sixteen sessions of transactional analysis therapy. The diagnosis is based on the new DSM-5 criteria that allow differentiation between Depression and Bereavement. The conclusion of the judges was that this was a good-outcome case: the client improved early over the course of the therapy, reported positive experience of therapy and maintained the improvement at the end of the follow-up
Dr. Glendon Swarthout
No full textHosted by Roger M. Busfield, MSU Assistant Professor of Speech and Theater, Meet the Author is designed to introduce a general audience to a contemporary author and their work through in-depth interviews. This episode features a conversation between Dr. Glendon Swarthout, prolific author and English professor at MSU, and assistant professors Sam S. Baskett and Theodore B. Strandness
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