Shell concentrations from the Miocene Ar Rajmah Group at Soluq-Al Abyar road cut, southern Al Jabal Al Akhdar, NE Libya
- PDF / 5,844,237 Bytes
- 15 Pages / 595.276 x 790.866 pts Page_size
- 71 Downloads / 148 Views
ARABGU2016
Shell concentrations from the Miocene Ar Rajmah Group at Soluq-Al Abyar road cut, southern Al Jabal Al Akhdar, NE Libya Gamal M. El Qot 1 & Esam O. Abdulsamad 2 & Abdelsalam El Fakhry 2
Received: 8 September 2016 / Accepted: 5 December 2016 / Published online: 18 January 2017 # Saudi Society for Geosciences 2017
Abstract The Miocene Ar Rajmah Group, exposed along the Soluq-Al Abyar road cut in southern Al Jabal Al Akhdar, NE Libya, is very rich in both micro- and macrofossils, especially molluscs and echinoids. Seven shell concentrations were recognized of which four from the Benghazi Formation; pectinids–small oyster concentration (BSC1), Echinolampas sp.–Clypeaster cf. martini concentration (BSC2), molluscan shell concentration (BSC3), and Echinolampas cf. amplus– Clypeaster acclivis concentration (BSC4). Three shell concentrations occur in the Wadi Al Qattarah Formation; large oyster concentration (QSC1), Crassostrea gryphoides– Chlamys zitteli concentration (QSC2), and Cubitostrea digitalina concentration (QSC3). The main factors controlling the formation of the shell concentrations were storm-induced waves and currents, reduced sediment input, settling behavior of benthic macro-invertebrates, and productivity.
Keywords Miocene . Shell concentrations . Soluq-Al Abyar road cut . Southern Al Jabal Al Akhdar . NE Libya
This article is part of the Topical Collection on Current Advances in Geology of North Africa * Gamal M. El Qot [email protected] Esam O. Abdulsamad [email protected] 1
Geology Department, Faculty of Science, Benha University, Benha, Egypt
2
Earth Sciences Department, Faculty of Science, Benghazi University, Benghazi, Libya
Introduction Shell concentrations are widespread features in the sedimentary record. They represent one end-member of possible outcomes of carbonate preservation dynamics where net skeletal preservation is maximized owing to high production rates, low disintegration rates, and/or low sedimentation rates (Kidwell 1986, 1991; Davies et al. 1989; Fürsich and Oschmann 1993; Tomašovŷch et al. 2006). Analyses of shell concentrations and their genetic classifications provide a tool for paleoenvironmental reconstructions (e.g., Kidwell et al. 1986; Kidwell 1991; Fürsich and Oschmann 1993; Fürsich 1995; Abbot 1997; El Qot et al. 2009). Although shell concentrations are widespread in the sedimentary record, they have received comparatively little attention until now, especially in North Africa and the Middle East region. Few studies have been carried out dealing with this matter in this region including Kassab (1995), El-Ayyat and Kassab (2004), El Qot et al. (2009), Mekawy (2013), El-Sabbagh and El-Hedeny (2016). The present study deals with shell concentrations from the Miocene rocks of the Ar Rajmah Group from the Soluq-Al Abyar road cut near Soluq (located about 70 km southeast of Benghazi; 31° 43′ N and 20° 28′ E; Fig. 1), to deduce the paleoenvironment of the Miocene Ar Rajmah Group.
Lithostratigraphy The Ar Rajmah Group The Ar Rajmah Group represents the young
Data Loading...
