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Titolo:
Recognition of tectonic events in undeformed regions: contrasting results from the Midland Platform and East Midlands Shelf, Central England
Autore:
Green, PF; Thomson, K; Hudson, JD;
Indirizzi:
Geotrack Int, W Brunswick, Vic 3055, Australia Geotrack Int W Brunswick Vic Australia 3055 runswick, Vic 3055, Australia Univ Birmingham, Sch Earth Sci, Birmingham B15 2TT, W Midlands, England Univ Birmingham Birmingham W Midlands England B15 2TT W Midlands, England Univ Leicester, Dept Geol, Leicester LE1 7RH, Leics, England Univ Leicester Leicester Leics England LE1 7RH er LE1 7RH, Leics, England
Titolo Testata:
JOURNAL OF THE GEOLOGICAL SOCIETY
, volume: 158, anno: 2001,
parte:, 1
pagine: 59 - 73
SICI:
0016-7649(200101)158:<59:ROTEIU>2.0.ZU;2-#
Fonte:
ISI
Lingua:
ENG
Soggetto:
LATEST CRETACEOUS HOTSPOT; FISSION-TRACK ANALYSIS; TERTIARY EROSION; SOUTHEASTERLY TILT; NORTH-ATLANTIC; ONSHORE UK; APATITE; MODEL; INVERSION; BRITAIN;
Keywords:
AFTA; East Midlands; vitrinite reflectance; exhumation; thermal history;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Physical, Chemical & Earth Sciences
Citazioni:
62
Recensione:
Indirizzi per estratti:
Indirizzo: Green, PF Geotrack Int, 37 Melville Rd, W Brunswick, Vic 3055, Australia Geotrack Int 37 Melville Rd W Brunswick Vic Australia 3055 ralia
Citazione:
P.F. Green et al., "Recognition of tectonic events in undeformed regions: contrasting results from the Midland Platform and East Midlands Shelf, Central England", J GEOL SOC, 158, 2001, pp. 59-73

Abstract

Apatite fission-track and vitrinite reflectance data from Central England demonstrate how these techniques can reveal otherwise unrecognized tectonicand/or palaeothermal episodes in apparently tectonically stable areas. Theresults document the transition from an inverted basinal region in the north (East Midlands Shelf), to a tectonically stable platform in the south (Midland Platform). AFTA data from the region reveal two discrete cooling episodes, in the Early and Late Tertiary. Maximum palaeotemperatures from AFTAand VR data in outcrop samples define a consistent increase from less thanor equal to 50 degreesC in Lower Cretaceous and Upper Jurassic units in the SE to around 80-90 degreesC in Triassic and older units in the NW. These Early Tertiary palaeotemperatures reflect a combination of deeper burial and elevated basal heat flow. Results from the Rufford-1 well define an EarlyTertiary palaeogeothermal gradient of 40.5 degreesC km(-1) (32-50 degreesCkm(-1) at +/- 95% confidence limits), corresponding to deeper burial by 1450 m of additional section (1.1-2.2 km at +/- 95% confidence limits), subsequently removed by Tertiary erosion. In contrast, geological considerationssuggest a maximum overburden of 800-900 m above the base of the Lower Jurassic in the vicinity of Rugby where palaeotemperatures at outcrop are similar to those near the Rufford-1 location. The discrepancy between stratigraphic and palaeo-thermal reconstruction of former burial depths, often noted in earlier studies, remains unresolved. The Late Tertiary episode is much less well-constrained, but results from Rufford-1 may require between 910 and 1650 m of eroded section. Thus much of the total amount of removed overburden may have been removed during the Late Tertiary. Results from the ApleyBarn Borehole (Oxfordshire) reveal a Late Tertiary palaeothermal episode characterized by a highly non-linear palaeotemperature profile which probably reflects local heating due to passage of hot fluids. Despite stratigraphic evidence for some Early Tertiary erosion results from this borehole show no evidence of Early Tertiary effects. Major Early and Late Tertiary exhumation was limited to regions underlain by older Palaeozoic basins while regions overlying Palaeozoic basement were more stable, experiencing significantly less exhumation. We suggest this reflects the preferential reactivationof the weaker basinal regions as a result of compressional events at platemargins. Our results emphasize the importance of incorporating results from both 'inverted' and 'non-inverted' areas in understanding the causal mechanisms of uplift and inversion, and highlight the importance of testing apparent stability using palaeo-thermal methods.

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Documento generato il 10/04/20 alle ore 15:59:14