The tertiary stratigraphy and echinoid palaeontology of Gozo, Malta

Abstract

The following succession of Tertiaiy rocks is established on the Maltese island of Gozo (youngest "beds first): Upper Coralline Limestone, over 290 feet; Transitional Greensand, 0 to 40 feet J Blue Clay, 0 to 200 feet; Upper Globigerina Limestone, 40 to l10-feet; Middle Globigerina Limestone, 0 to 60 feet; Lower Globigerina Limestone, 17 to 75 feet; Scutella Bed, ½ to 20 feet; Lower Coralline Limestone, over 450 feet. The algal and foraminiferal Lower Coralline Limestone was probably deposited in shallow water. The prominent Scutella Bed resembles a near-surface shell bank. Two phosphatic nodule beds, possibly marking stagnant periods, separate the Globigerina Limestones. The lower and upper divisions are formed of pelagic foraminifera with lamellibranchs and neritic echinoids. The middle division, a marly limestone, may be a deep of water deposit but has an upper, coarser facies in south-west Gozo. The Lower and Middle Globigerina Limestones thin eastward and the latter is absent over much of the eastern area where the nodule beds coalesce. The Upper Globigerina Limestone— Blue Clay boundary, despite sane previous opinions, is always sharp. The two beds have faunal similarities, their lithological differences are probably caused by a sudden onset of mud deposition. Variations in, thickness of the Blue Clay are considered to have an erosional origin. There is a gradual passage through the glauconitic Transitional Greensand, which varies in thickness and lithology and has a thick-shelled fauna suggesting a shallow water origin, to the Upper Coralline Limestone, which has a soft, lower division and a hard upper one, complicated by lateral variation and later recementation. The echinoids from the above succession are listed and the following ten species are described and figured: Scutella subrotunda, Scutella sp. nov., Hemiaster scillae, Hemiaster cotteaui, Fericosmus latus, Gregoiyaster lorioli, Schizaster eurynotus, Schizaster parkinsoni, Eupatagus dekonincki, Echinolampas lucae.