Bulletin of the Geological Society of Malaysia, Volume 53, June 2007, pp. 1 – 6

Discovery of a Lower Devonian Dacryoconarid bed from Hill B Guar Jentik, Perlis: Its significance and implications

Ong Swang Theng and Basir Jasin

Geology Programme, School of Environmental Science and Natural Resources, Faculty of Science and Technology, Universiti Kebangsaan Malaysia, 43600 Bangi, Selangor Darul Ehsan, Malaysia

Abstract: A Lower Devonian dacryoconarid bed has been found in Hill B at Guar Jentik, Perlis. This fossiliferous bed stratigraphically overlies a biomicritic limestone lenticle, also known as the Sanai Limestone member, which is located at the lower part of Hill B. The Dacryoconarid bed contains Nowakia acuaria and Styliolina sp.. Monograptus sp. and Plectodonta forteyi were also found in this layer. The occurrence of Nowakia acuaria and Plectodonta forteyi in the dacryoconarid bed indicate a late Pragian to early Emsian age. Dacryoconarids are randomly oriented and abundant at the top of the limestone overlying the dacryoconarid bed. Dacryoconarids are very rare in the middle part of the limestone. This indicates that the limestone bed at Hill B is older than Pragian. It is probably the upper part of the Setul Formation. The Devonian sequence at Hill B, which is represented by thinly bedded mudstone and the dacryoconarid bed, suggests very slow deposition or non-deposition during Middle and Late Devonian.

Abstrak: Lapisan dacryoconarid yang berusia Devon Bawah telah dijumpai di Bukit B Guar Jentik, Perlis. Lapisan kaya fosil ini secara stratigrafi menindih kekanta batu kapur biomikrit, yang terletak di bahagian bawah Bukit B. Lapisan dacryoconarid mengandungi Nowakia acuaria dan Styliolina sp. Selain daripada itu, Monograptus sp. dan Plectodonta forteyi juga dijumpai dalam lapisan ini. Nowakia acuaria dan Plectodonta forteyi adalah fosil index biostratigrafi yang penting dalam menunjukkan lapisan dacryoconarid ini berusia dari Pragian Akhir ke Emsian Awal. Dacryoconarid wujud dalam pelbagai orientasi dan banyak di bahagian atas batu kapur terutamanya di sentuhan antara batu kapur dan lapisan dacryoconarid. Dacryoconarid sangat jarang di bahagian tengah batu kapur. Ini menunjukkan lapisan batu kapur di Bukit B adalah lebih tua dari Pragian. Kemungkinan ini merupakan bahagian atas Formasi Setul. Jujukan Devon di Bukit B yang diwakili oleh lapisan nipis batu lodak dan lapisan dacryoconarid mencadangkan pengendapan yang perlahan atau tiada pengendapan semasa Devon Tengah dan Devon Akhir.

https://doi.org/10.7186/bgsm53200701