The stratigraphy, structure and significance of the Nenering Tertiary beds, Pengkalan Hulu (Keroh), Hulu Perak

The study area which is located at the northern most part of Peninsular Malaysia neighbouring Thailand, displays outcrops of a series of rocks with ages that range nearly the entire Paleozoic Era and Cenozoic Era, that is, the Kroh Formation (Early Ordovician-Early Devonian), Kati Formation (CarboPermian?) and Nenering Tertiary Beds (Tertiary). The older Kroh Formation act as the basement unit for the other two younger formations. The strata of the Kroh Formation are extremely folded and deformed, whereby lying above it is the broadly folded Kati Formation which is limited to the SE portion and the Nenering Tertiary Beds to the NE portion of the study area. Both of the younger formations lie above clearly exposed basal planes of unconformity which are angular in nature. The Nenering Tertiary Beds which is an alluvial-fluviatile continental deposit comprises three main units, namely:- i) The Lower Unit ii) The Middle Unit iii) The Upper Unit The lithology consists of well-consolidated to semi-consolidated gravel beds, sandstone, silt and mud. Structurally the study area has undergone two periods of tectonic deformation, both of which are subjected to an east-west compression force that resulted in the two phases of folding of the strata of the Kroh Formation and the broad folds of the Kati Formation. The area has also gone through an active period of faulting during the pre-Tertiary which play an important role in the development of the sedimentary basin of the Nenering Tertiary Beds. Faulting remained active during the Tertiary periods and resulted in the tilting of the Tertiary beds to a broad open fold structure and exposing the primary plane of unconformity between the related formations