Abstract
Integrated analysis that involves physical sedimentological, standard palynological and electrofacies analyses on ditch cuttings and suite of wireline logs from Gaibu–1 Well, southern Bornu were examined to identify critical sequence elements and construct a bio-sequence stratigraphical framework. Four (4) palynozones consisting of Triorites africaensis, Cretacaeiporites scabratus - Odontochitina costata, Droseridites senonicus and Syncolporites/Milfordia spp Assemblage Zones construed to be Late Cretaceous – younger successions. Nine (9) depositional sequences each with candidate maximum flooding surfaces (375, 900, 1875, 2250, 2600, 3050, 3400, 3800, 4300 m) marked by marker shales with high abundance and diversity of palynomorphs. Thus, equate with the local lithostratigraphy and global large-scale depositional cycles with candidate sequence boundaries (50, 725, 1625, 2175, 2490, 2850, 3300, 3610, 3960, 4470 m) ranging about 96.28 to 70.07 Ma. The delineated transgressive surfaces along the built sequences mark the subjected onset of marine flooding characterised with interchange of progradational to retrogradational facies. Delineated sequence elements generally show up-hole from progradational to retrogradational and aggradational that represents Lowstand Systems Tracts (LSTs), Transgressive Systems Tracts (TSTs) and Highstand Systems Tracts (HSTs) respectively. The LSTs are seen in form of prograding complex and slope fans, suggestive of good reservoirs. The TSTs consist of channel sand units and shales that depict retrogradational marine units, which could serve as both seals and source rocks for the sand units. The HSTs are made up of interplay of aggradational to progradational sediment packages that could serve as a potential source rock. The palaeoenvironmental indices depict the successions are deposited within continental to open marine settings. 
Highlights
The Gaibu-1 Well was drilled in the southern segment of the Bornu Sub-basin (Nigeria’s portion of the mega Chad Basin), northeastern Nigeria (Figure 1)
Careful palynozones were established with the aid of local calibrated bioevents of First Downhole Occurrence (FDO) or Last Appearance datum (LAD) of diagnostic markers ascribed from each defined interval to prevent the caving / admixture of microfossils associated with ditch cuttings, while the ages derived were relative to the published literatures
An illustration of sandstone distribution based on the conducted sandstone analysis in the well is presented in Table 2, while Figure 2 shows the sandstone distribution as derived from wireline log and ditch cutting description
Summary
The Gaibu-1 Well was drilled in the southern segment of the Bornu Sub-basin (Nigeria’s portion of the mega Chad Basin), northeastern Nigeria (Figure 1). The last two to three decades have witnessed intense research and exploration efforts on the basin (Olugbemiro 1997; Adekoya et al 2014), owing to the discovery of commercial quantity of hydrocarbons in the upper portion of the mega Chad Basin (Termit Basin – Harouna and Philip, 2012) While, these researches covered the basin’s geo–history (Genik,1993; Hartley and Allen, 1994; Obaje et al 2004), stratigraphic palynology (Ola-Buraimo 2009; Ola–Buraimo and Boboye 2011; Ola-Buraimo 2012; Ola-Buraimo and Oluwajana 2012), foraminifera biostratigraphy (Adegoke 2012; Boboye 2012) and hydrocarbon potentials (Okosun 1995; Olugbemiro et al 1997; Zaborski et al 1998; Obaje et al 2006; Hamza et al 2011; Mohammed and Tela 2012; Adegoke et al 2015). This manuscript attempt integration of the recouped lithic characteristics, palynological data and wireline log dataset to construe
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