Geology/Closure of a stratigraphic layer
QUESTION: I understand "structural closure" to be the area bounded by the lowest structural contour line, but what would "closure" mean when referring to a stratigraphic layer? e.g. "closure of the sandy layers occurs in the area south and northwest of the field as a result of normal faults."
ANSWER: I'm not real sure that I understand the question; however, I definitely don't understand the example about sandy layers etc. If you want to reword the question I will try to answer it.
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Thanks for your quick response. I can't really rephrase it, because I don't have much to go on, but I can give you more context. This is for a translation that I'm working on, and I've since realized that it means closure "by" sandy layers instead of closure "of" sandy layers, so that solves my translation problem, but I would still like to be able to visualize what is happening here. Here is the text with more context:
"The structure of is represented by a gentle, NW-SE elongated anticline. The hydrocarbon trap is mixed both stratigraphically and structurally with a combination of plastic tectonic structures such as anticlinal folding, plus rigid structures such as faults, and stratigraphic elements such as argillification closures and lenticular porous bodies. **Closure by sandy layers** occurs in the area south and northwest of the gas field as a result of normal faults. In particular, there is a normal fault in the southern area with [rigetti] on the order of hundreds of meters; in the northwest area, two normal faults of modest [rigetti] displace the blocks crossed by wells X and Y. In the N-NE area of the field, closure is assured by the presence of a stratigraphic limit due to a progressive argillification of the sediments and consequent lateral variation of porosity against the western flank of the upper carbonate."
As you can see, I'm still struggling with another term... "rigetti" literally means something that is discarded or thrown back, but if I can't locate the technical term, I guess that would be the topic of another question. Thanks in advance for your help with "closure."
I don't read the "Closure" as being a structural closure; to me the closure is the closure of the hydrocarbon trap. It may in fact be a structural closure by I don't read into the statement that it is such. Reading the statement previous to "Closure by sandy layers" indicates argillaceous closures, I believe that "closure by sandy layers" is just a continuation of the same tread of thought.
Sorry I couldn't give you a better answer - hope this helps.