Analytical procedure followed for the microscale analyses of core samples. 

	Technique	Equipment	Sample type	Data obtained	Comment	
1	Core description under normal and UV light 		Polished core slabbed surface	Chalk facies and photographs	Description performed according to Table 1	
2	Computerized tomography scan (CT scan)	CT scan	Polished core slabbed surface	Density distribution and fractures		
3	Mini-permeameter and porosimeter analyses	Mini-permeameter  performing punctual  nitrogen gas injection	Polished core slabbed surface	Permeability and porosity measurements  	Measurements were performed at 5 mm spacing along a hypothetical median line 	
4	Porosity and gas permeability 	Gas permeameter and porosimeter	Core plugs (2.54 cm diameter)	N2-porosity and air-permeability (Klinkenberg corrected)		
5	Petrographic and microtextural description	Optical microscope	Thin sections (6 cm2 area)	Petrography and microtexture		
6	Scanning Electron Microscope (SEM) observations	Philips XL 30 SEM and  voltage equal to 12 keV	Spot size of 0.5 µm 	High resolution 2D microtextural description of BSE images

High resolution 3D textural description at x1000, x5000, x1000 and x20000 magnifications in SE mode		
7	Porosity estimation through image analysis	JMicroVision	3 to 6 BSE photomicrograph at x1000 of thin sections	Porosity of high resolution (x1000) thin sections	JmicroVision is an image analysis toolbox for measuring and quantifying components of high-definition images 	
8	Energy Dispersive X-ray Spectroscopy (EDS Spectrum)	Philips XL 30 SEM	Selected areas of thin sections	Analysis of elemental composition and distribution		
9	X-Ray diffraction analyses (XRD) and X-Ray fluorescence (XRF)	XRD and XRF spectrometer	Rock powders (4-10 cm3)	Quantitative mineralogical composition	The results of XRD and XRF analyses were combined for quantitative mineralogy using a Total in-house software	
Analytical procedure followed for the microscale analyses of core samples. BSE= back-scattered electron mode; SE= secondary electron mode.