A computer-implemented method of generating a depositional sequence volume from seismic data, the method comprising: receiving a seismic dataset comprising grid points of a 3-D subsurface model, wherein a first subset of the grid points and a second subset of the grid points identify corresponding 3-D seismic image cubes located within a 3-D mesh of cubical cells, and the first subset of grid points and the second subset of grid points comprise image values that describe the location and orientation of geological horizons located within the 3-D subsurface model; identifying reflections at the first subset of the grid points and geological constraints at the second subset of the grid points by processing the image values; and generating a depositional sequence volume for the 3-D subsurface model from the reflections at the first subset of grid points and the geological constraints at the second subset of grid points, wherein gradients of the depositional sequence volume are orthogonal to reflection planes of the reflections, wherein: identifying reflections at the first subset of the grid points further comprises: computing normal vectors of the plurality of reflections based on the image values at the first subset of grid points and deriving tangent vectors of the reflections at the first subset of grid points from the normal vectors of the reflections, wherein each grid point has an associated pair of linearly independent tangent vectors; generating a depositional sequence volume for the 3-D subsurface model further comprises: solving, subject to certain boundary conditions, a set of partial differential equations that minimizes a sum of squares of a dot product between the gradient of the depositional sequence volume at a respective grid point and a pair of linearly independent tangent vectors at the same grid point; and the sum is minimized by subjecting the depositional sequence volume at the second subset of grid points to the corresponding geological constraints, which represent different boundary conditions. receiving a seismic dataset comprising grid points of a 3-D subsurface model, wherein a first subset of the grid points and a second subset of the grid points identify corresponding 3-D seismic image cubes located within a 3-D mesh of cubical cells, and the first subset of grid points and the second subset of grid points comprise image values that describe the location and orientation of geological horizons located within the 3-D subsurface model; identifying reflections at the first subset of the grid points and geological constraints at the second subset of the grid points by processing the image values; and generating a depositional sequence volume for the 3-D subsurface model from the reflections at the first subset of grid points and the geological constraints at the second subset of grid points, wherein gradients of the depositional sequence volume are orthogonal to reflection planes of the reflections, wherein: identifying reflections at the first subset of the grid points further comprises: computing normal vectors of the plurality of reflections based on the image values at the first subset of grid points and deriving tangent vectors of the reflections at the first subset of grid points from the normal vectors of the reflections, wherein each grid point has an associated pair of linearly independent tangent vectors; generating a depositional sequence volume for the 3-D subsurface model further comprises: solving, subject to certain boundary conditions, a set of partial differential equations that minimizes a sum of squares of a dot product between the gradient of the depositional sequence volume at a respective grid point and a pair of linearly independent tangent vectors at the same grid point; and the sum is minimized by subjecting the depositional sequence volume at the second subset of grid points to the corresponding geological constraints, which represent different boundary conditions. identifying reflections at the first subset of the grid points further comprises: computing normal vectors of the plurality of reflections based on the image values at the first subset of grid points and deriving tangent vectors of the reflections at the first subset of grid points from the normal vectors of the reflections, wherein each grid point has an associated pair of linearly independent tangent vectors; generating a depositional sequence volume for the 3-D subsurface model further comprises: solving, subject to certain boundary conditions, a set of partial differential equations that minimizes a sum of squares of a dot product between the gradient of the depositional sequence volume at a respective grid point and a pair of linearly independent tangent vectors at the same grid point; and the sum is minimized by subjecting the depositional sequence volume at the second subset of grid points to the corresponding geological constraints, which represent different boundary conditions.