Stratigraphy and age estimate of Neogene shallow marine fossiliferous deposits in Brunei Darussalam (Ambug Hill, Tutong district). (1st June 2018)

• Record Type: Journal Article
• Authors: Kocsis, László; Briguglio, Antonino; Roslim, Amajida; Razak, Hazirah; Ćorić, Stjepan; Frijia, Gianluca
• Is Part Of: Journal of Asian earth sciences. Volume 158(2018)
• Page Start: 200
• Page End: 209
• Publication Date: 2018-06-01
• Subjects: Nannofossils -- Sr-isotope stratigraphy -- Late Miocene -- Southeast Asia -- Paleontology -- Sea level change -- Ambok or Ambuk hill; Earth sciences -- Asia -- Periodicals; Sciences de la terre -- Asie -- Périodiques; Earth sciences; Asia; Periodicals; 555.05
• DOI: 10.1016/j.jseaes.2018.02.023
• Languages: English
• ISSNs: 1367-9120

Abstract

Graphical abstract: Highlights: Exceptional fossiliferous marine deposits from Brunei Darussalam, Borneo. Combined bio- and Sr-isotope stratigraphy. Established Late Miocene (Late Tortonian-Messinian) age. A potential reference outcrop for studying palaeo-biodiversity. A promising sedimentary series for onshore type locality. Abstract: The Ambug Hill in Brunei is an exceptional geological site where a series of siliciclastic rocks crops out with some layers extremely rich in marine fossils. Such fossiliferous outcrops are extremely rare in the northern part of Borneo and their description is of primary importance as their fossil content can be used to correlate the regional depositional sequences with global biostratigraphic zonations. In this work we present for the first time a detailed sedimentary profile completed with Sr-isotopes and biostratigraphic dating. The succession is divided into four sedimentary units. The first unit comprises bioturbated sandstone followed by a second unit of clay-silt rich levels whose first 9.5 m contain rich marine fossil assemblages. Calcareous nannoplankton data indicate a Late Tortonian – Early Messinian (NN11) age, which is confirmed by Sr-isotope dating derived from bivalves giving a numerical age range from 8.3 to 6.2 My. After a major emersion surface, the third sedimentary unit of sand- and siltstone lacks suitable fossils for bio- and isotope stratigraphy. The age of emersion and the related sedimentary gap can be either correlated with the Me1 (7.25 My) or the Me2 (5.73 My) sequence boundary. A fourth, thin sedimentary unit is recognized on the top of the profile with silt- and claystone beds without age diagnostic remains and calcareous fossils.