pointers to a class in dynamically allocated boost multi_array, not compiling

I am pretty new to C++ with Boost.

I want an object of class "world" to have an array named "chunk" of type "octreenode". Previously I had an ordinary one-dimensional array, and this worked fine. Now I'm trying to move to using a 3D array with Boost's multi_array functionality, and I'm really not sure what I'm doing wrong.

Simplified code:

class world {
public:

  typedef boost::multi_array<octreenode, 3> planetchunkarray;  // a boost_multi for chunks
  typedef planetchunkarray::index index;
  planetchunkarray *chunk;

  world(double x,double y,double z,
        int widtheast, int widthnorth, int height) :
        originx(x), originy(y), originz(z),
        chunkseast(widtheast), chunksnorth(widthnorth), chunksup(height) {

    chunk = new planetchunkarray(boost::extents[chunksnorth][chunkseast][chunksup]);
    planetchunkarray::extent_gen extents;

    for (int cz = 0; cz < chunksnorth; ++cz) {
      for (int cx = 0; cx < chunkseast; ++cx) {
        for (int cy = 0; cy < chunksup; ++cy) {
          (*chunk)[cz][cx][cy] = new octreenode(1,72);
        }
      }
    }
  }
};

After which if I attempt to make the assignment

root->planet[0]->chunk[0][0][0]->material = 4;

I get the error:

error: base operand of '->' has non-pointer type 'boost::detail::multi_array::sub_array<octreenode, 1u>'|

"octreenode" has the relevant constructor, and this line worked in identical syntax when it was just:

root->planet[0]->chunk[0]->material = 4;

(with a one-dimensional array). Similarly, while it compiled fine with a one-dimensional array, trying to pass the chunk to functions that expect a pointer to an "octreenode" object, such as:

compactoctree(root->planet[p]->chunk[cz][cx][cy], 0, 14);

generates the error

error: cannot convert 'boost::detail::multi_array::sub_array<octreenode, 1u>' to 'octreenode*' for argument '1' to 'short int compactoctree(octreenode*, int, int)'|

Would be very grateful for any suggestions, I'm sure I'm missing something obvious.