Extreme crustal thinning in the south Porcupine Basin and the nature of the Porcupine Median High: Implications for the formation of non-volcanic rifted margins.

Reston, Timothy J., Gaw, Viola, Pennell, J., Klaeschen, Dirk , Stubenrauch, A. and Walker, I. (2004) Extreme crustal thinning in the south Porcupine Basin and the nature of the Porcupine Median High: Implications for the formation of non-volcanic rifted margins. Journal of the Geological Society, 161 . pp. 783-798. DOI 10.1144/0016-764903-036.

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Abstract

The southern Porcupine Basin is characterized by axial stretching factors that are greater than six and typical of rifted margins. As such, the basin can be regarded as a natural laboratory to investigate the evolution and symmetry of rifting leading towards continental separation and breakup. A bright reflection (here named P) cuts down to the west from the base of the sedimentary section, is overlain by small fault blocks and appears to represent a detachment fault. P may in part follow the top of partially serpentinized mantle: this interpretation is consistent with gravity modelling, and with numerical models of crustal embrittlement and mantle serpentinization during extension. Furthermore, P closely resembles the S reflection west of Iberia, where such serpentinites are well documented. Although overall the basin remains symmetrical, the consistent westward structural dip of the detachment implies that, at high stretching factors, extension became asymmetric. Farther south, the ‘Porcupine Median High’, appearing lens-shaped in cross-section, overlies the tilted fault blocks and is onlapped by postrift sediment. Despite no evidence for synrift magmatism, this high has previously been interpreted as a basaltic structure. However, it develops above the line of intersection of the crust–mantle boundary with the P detachment, and hence may be related to the spatial limit of serpentinization. The median high may represent a serpentinite mud volcano or diapir; we suggest that such structures produce the serpentinite breccias found within the rifted continent–ocean transition of nonvolcanic margins.

Document Type: Article
Keywords: Crustal thinning, south Porcupine Basin
Research affiliation: OceanRep > GEOMAR > FB4 Dynamics of the Ocean Floor > FB4-GDY Marine Geodynamics
Refereed: Yes
Open Access Journal?: No
DOI etc.: 10.1144/0016-764903-036
ISSN: 0016-7649
Date Deposited: 10 Feb 2010 15:36
Last Modified: 15 Jan 2019 13:09
URI: http://oceanrep.geomar.de/id/eprint/7209

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