Thermal anomaly and water origin in Weebubbie Cave, Nullarbor Karst Plain, Australia

Remnants of the Caribbean Large Igneous Plateau (C-LIP) are found as thickened zones of oceanic crust in the Caribbean Sea, that formed during strong pulses of magmatic activity around 90 Ma. Previous studies have proposed the Gal&#225;pagos hotspot as the origin of the thermal anomaly responsible for the development of this igneous province. Particularly, geochemical signature relates accreted C-LIP fragments along northern South America with the well-known hotspot material.In this research, we use 3D lithospheric-scale structural and density models of the Caribbean region, in which up-to-date geophysical datasets (i.e.: tomographic data, Moho depths, sedimentary thickness, and bathymetry) have been integrated. Based on the gravity residuals (modelled minus observed EIGEN6C-4 dataset), we reconstruct density heterogeneities both in the crust and the uppermost oceanic mantle (< 50km).Our results suggest the presence of two positive mantle density anomalies in the Colombian and the Venezuelan basins, interpreted as the preserved plume material which migrated together with the Proto-Caribbean plate from the east Pacific. Such bodies have never been identified before, but a positive density trend is also observed in the mantle tomography, at least down to 75 km depth.Using recently published regional plate kinematic models and absolute reference frames, we test the hypothesis of the C-LIP origin in the Gal&#225;pagos hotspot. However, misfits of up to ~3000 km between the present hotspot location and the mantle anomalies, reconstructed back to 90 Ma, is observed, as other authors reported in the past.Therefore, we discuss possible sources of error responsible for this offset and pose two possible interpretations: 1. The Gal&#225;pagos hotspot migrated (~1200-3000 km) westward while the Proto-Caribbean moved to the northeast, or 2. The C-LIP was formed by a different plume, which &#8211; if considered fixed - would be nowadays located below the South American continent.

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2. Communication relative to the Fresh-Water Limestone of Burdiehouse, near Edinburgh, belonging to the Carboniferous Group of Rocks

Proceedings of the Royal Society of Edinburgh ◽

10.1017/s0370164600037147 ◽

1845 ◽

Vol 1 ◽

pp. 33-35 ◽

Cited By ~ 1

Author(s):

Hibbert

Keyword(s):

Fresh Water ◽

Marine Origin ◽

North East ◽

South West ◽

Water Origin ◽

The Common ◽

Firth Of Forth ◽

Carboniferous Limestone

In his paper, the author explains that the limestone in question, which is confounded with the common carboniferous or mountain limestone of marine origin, is, in his opinion, of fresh-water origin.On an irregular line extending from Joppa on the coast of the Firth of Forth, in a south and south-west direction to the Pentland Hills, strata of mountain or carboniferous limestone crop out at intervals; and their marine origin is indicated by encrinites, the Productus, &c., and corallines. This limestone is developed with least interruption between Edmonstone and Muirhouse, where it is from twelve to twenty feet thick. At this part of the line may be seen fractures and elevations of the strata of limestone and superincumbent shale and sandstone, evidently occasioned by a sudden and violent uplifting force acting from north-east to south-west, and causing the uplifted strata to dip south-east at an angle of 25°. These uplifted beds, between Edmonstone and Muirhouse, and subsequently to Burdiehouse, form the strata which dip under the coalmeasures of Gilmerton, Loanhead, and other sites.

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