Assessing palaeobathymetry and sedimentation rates using palynomaceral analysis: a study of modern sediments from the Gulf of Papua, offshore Papua New Guinea

Abstract

A Nittrouer (2015): Assessing palaeobathymetry and sedimentation rates using palynomaceral analysis: a study of modern sediments from the Gulf of Papua, offshore Papua New Guinea, Palynology, Palynologists interested in better understanding the sedimentation and energy of depositional environments have often included studies of palynomaceral fragments, particularly when performing palynofacies analyses. Due to the difficult nature of classifying these fragments, researchers have developed numerous, often overlapping, classification schemes. These different schemes make it difficult to compare and contrast between research projects. Determining the appropriate scheme to apply when counting these fragments can be confusing, and application of these schemes can yield inconclusive results, especially when sedimentation and energy are in constant flux. A scheme of five categories, including brown wood (palynomaceral 1À2), leaf cuticle (palynomaceral 3), black debris (palynomaceral 4), structureless organic matter (SOM) and resin, is utilised here. It is applied to the analysis of 64 modern samples from the top 0À4 cm of sediment collected throughout the Gulf of Papua, Papua New Guinea. These samples span a suite of common marine depositional environments: river mouths and deltas, the proximal portion of the continental shelf dominated by a large clinoform, and turbidite and hemipelagic/pelagic deposits on the slope and in the deep ocean basin. Principal component analysis (PCA) confirms this simplified classification scheme provides an indirect means of assessing distance from shore and shelf-slope break, overall water depth and sediment accumulation rate, but other factors, such as processing technique, marine productivity, sediment source, time in transport and residence and bioturbation, are taken into account to fully explain distribution.

Palynofacies analysis of Ida-4 well, Niger Delta Basin, Nigeria

“…The palynomaceral slides were subjected to quantitative analysis of different types of palynomacerals (type 1, 2, 3, and 4) as well as structureless organic matter (SOM). Identification of palynomorph and palynomacerals was made using palynological albums and the published works of previous researchers (Germeraad et al 1968, Oyede 1992, Ige 2009, Bankole 2010, Ige et al 2011, Ajaegwu et al 2012, Durugbo & Aroyewun 2012, Ola & Adewale 2014, Thomas et al 2015.…”

“…It is heterogeneous and of higher plant in origin and some are products of exudation processes such as the gelification of plant debris in the sediments. Palynomaceral 1 includes small, medium and large sizes of flora debris, humic gel-like substances and resinous cortex irregularly shaped materials (Oyede 1992, Thomas et al 2015.…”

“…Also, it includes structured plant material, mainly of cuticular origin and degraded aqueous plant material. It is more buoyant than palynomaceral 2 (Thomas et al 2015).…”

“…Blade-shaped palynomaceral 4 is extremely buoyant and resistant to degradation. Thus, they are often transported over long distances (Oyede 1992, Thomas et al 2015. A concentration of PM 4 characterizes a high energy environment.…”

“…The term was first introduced by Combaz (1964) to describe the total microscopic image of the organic components in sedimentary rock samples. Subsequent authors have assigned different names to the organic components such as organic matter (Gehmann 1962, Lorente 1990, Batten & Stead 2005, palynodebris (Boulter & Riddick 1986, Van der Zwan 1990, Boulter 1994) and kerogen or palynomacerals (Oyede 1992, Tyson 1995, Araujo et al 1998, Thomas et al 2015. Palynofacies was defined by Tyson (1995) as a body of sediment containing a distinctive assemblage of palynological organic matter thought to reflect a specific set of environmental conditions or to be associated with a characteristic range of hydrocarbon-generating potential.…”