Friday, 6 May 2016

Urban Geology: Grand Central Birmingham

Grand Central is the newest shopping complex in central Birmingham, replacing the old Pallasades shopping centre above New Street Station. The floor of this new shopping area is packed full of fossils, all of which are marine. There are two types of limestone here; a beige Jura Limestone from Germany, and a black, bituminous limestone from Spain.

Sponge fossil
The beige limestone has been on this blog before as it is used in the shop surrounds of the new Longbridge Town Centre in south Birmingham. Many of the same fossils feature at Grand Central – belemnite guards, ammonites, sponges, and fossil debris, as well as stylolites. This rock is Jurassic in age, so about 145 – 200 million years old.

en echelon tension gashes

The black limestone, Nero Marquina Marble, has stripes called en echelon gashes. These represent cracks in the rock as it was stretched under tension. The cracks were infilled with hydrothermal fluids which crystallised out. This rock is Cretaceous in age, so between 66 – 140 million years old. The white cliffs of Dover are the same age.

Grand Central will feature in Part Three of the Birmingham Building Stones guide.

Ammonite with hand for scale

Belemnite guard with phragmocone