## 5 Discussion
### Bioturbation and Burrow Fill Impact on Porosity and Permeability  
The studied samples show a weak relationship between bioturbation and both porosity and permeability, with an R2 < 0.2 (Figure 8A,B). However, when burrow fill is added, it becomes evident that the coarse-filled burrows have higher porosity and permeability values than the fine-filled burrows (compare Figure 8C,D). This means that burrow filling material has a significant control on the porosity-permeability values (Figure 9B). The positive relationship of porosity and bioturbation is well documented in literature discussing the enhancement of porosity and permeability of an otherwise impermeable matrix through the passive infill of burrows by coarse material [8; 14; 32; 59; 60; 61; 62]. In addition, the burrow networks can act as fluid conduits and may form loci for preferential dissolution by meteoric water and these processes may modify the vertical and lateral flow properties [4; 14]. Open and coarse-filled burrows provide preferred, permeable flow conduits in otherwise less permeable intervals [61].  
[PERSON] et al. [61] in their study of the Upper Hanifa Formation (Ulayyah member), demonstrated that coarse material infilling the burrows in mud-dominated units indicate that the filling material was deposited in a high-energy environment, unlike the host material which was deposited under a low-energy depositional environment. Because of the coarse-grained infill, the burrows are characterized by higher porosity and permeability values than the host muddy units. Our data agree with their findings for the muddy units (Figure 9B). However, [61] did not discuss the impact of bioturbation on the grain-dominated units and subsequent infill with fine-grained sediments.  
In grain-dominated units, bioturbation has a negative impact on porosity and permeability as most of these units possess lower porosity and permeability values, compared to mud-dominated units. This was attributed to cementation of inter-particle pore spaces, and filling of burrows by fine-grained sediments, which act as baffles or barriers within an otherwise porous and permeable zone [61]. [PERSON] et al. [14] in their study of the influence of bioturbation on the fluid flow system of the Lower Cretaceous Glen Rose limestone, demonstrated that grainstone units have low ichnofabric indices (ii1 to ii2) and restrict the fluid flow due to their low permeabilities. This restriction was attributed to cementation of interparticle pores by sparry calcite cement. Likewise, [63] in his study on ichnofabric impact on reservoir quality of the Permian-Triassic Khuff Formation, demonstrated that some bioturbation burrows (dwelling burrows) may occur in grainy units with considerable amounts of mud. As result, these burrows reduce porosity and permeability and act as barriers for fluid flow through these units. Our data agree with these findings [14; 63]; the grain-dominated samples show both scenarios of extensive cementation (Figure 3D,E) and burrow fill by muddy material (Figure 6C).  
The microstructure of the micrite plays another significant role in controlling the porosity, permeability, and acoustic velocity. Some mud-dominated samples are characterized by a subhedral porous micritic texture, leading to higher porosity, permeability, and low velocity values (Figure 15A). In contrast, the burrow mud-fill of the grain-dominated samples show a compact coalescent micritic texture (Figure 15B) associated with lower porosity, permeability, and high acoustic velocity values. The coarse-filled burrows of the mud-dominated units might have enhanced the fluid flow that resulted in micrite dissolution by meteoric water, resulting in a porous and permeable micritic structure [4; 62]. Conversely, the absence of flow pathways for meteoric water within the grain-dominated units, in addition to extensive cementation, resulted in the tight compact micritic texture discussed above.